File: rfc2743.txt

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Network Working Group                                            J. Linn
Request for Comments: 2743                              RSA Laboratories
Obsoletes: 2078                                             January 2000
Category: Standards Track


         Generic Security Service Application Program Interface
                          Version 2, Update 1


Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   The Generic Security Service Application Program Interface (GSS-API),
   Version 2, as defined in [RFC-2078], provides security services to
   callers in a generic fashion, supportable with a range of underlying
   mechanisms and technologies and hence allowing source-level
   portability of applications to different environments. This
   specification defines GSS-API services and primitives at a level
   independent of underlying mechanism and programming language
   environment, and is to be complemented by other, related
   specifications:

      documents defining specific parameter bindings for particular
      language environments

      documents defining token formats, protocols, and procedures to be
      implemented in order to realize GSS-API services atop particular
      security mechanisms

   This memo obsoletes [RFC-2078], making specific, incremental changes
   in response to implementation experience and liaison requests. It is
   intended, therefore, that this memo or a successor version thereto
   will become the basis for subsequent progression of the GSS-API
   specification on the standards track.





Linn                        Standards Track                     [Page 1]

RFC 2743                        GSS-API                     January 2000


TABLE OF CONTENTS

   1: GSS-API Characteristics and Concepts . . . . . . . . . . . .  4
   1.1: GSS-API Constructs . . . . . . . . . . . . . . . . . . . .  6
   1.1.1:  Credentials . . . . . . . . . . . . . . . . . . . . . .  6
   1.1.1.1: Credential Constructs and Concepts . . . . . . . . . .  6
   1.1.1.2: Credential Management  . . . . . . . . . . . . . . . .  7
   1.1.1.3: Default Credential Resolution  . . . . . . . . . . . .  8
   1.1.2: Tokens . . . . . . . . . . . . . . . . . . . . . . . . .  9
   1.1.3:  Security Contexts . . . . . . . . . . . . . . . . . . . 11
   1.1.4:  Mechanism Types . . . . . . . . . . . . . . . . . . . . 12
   1.1.5:  Naming  . . . . . . . . . . . . . . . . . . . . . . . . 13
   1.1.6:  Channel Bindings  . . . . . . . . . . . . . . . . . . . 16
   1.2:  GSS-API Features and Issues . . . . . . . . . . . . . . . 17
   1.2.1:  Status Reporting  and Optional Service Support  . . . . 17
   1.2.1.1: Status Reporting . . . . . . . . . . . . . . . . . . . 17
   1.2.1.2: Optional Service Support . . . . . . . . . . . . . . . 19
   1.2.2: Per-Message Security Service Availability  . . . . . . . 20
   1.2.3: Per-Message Replay Detection and Sequencing  . . . . . . 21
   1.2.4:  Quality of Protection . . . . . . . . . . . . . . . . . 24
   1.2.5: Anonymity Support  . . . . . . . . . . . . . . . . . . . 25
   1.2.6: Initialization . . . . . . . . . . . . . . . . . . . . . 25
   1.2.7: Per-Message Protection During Context Establishment  . . 26
   1.2.8: Implementation Robustness  . . . . . . . . . . . . . . . 27
   1.2.9: Delegation . . . . . . . . . . . . . . . . . . . . . . . 28
   1.2.10: Interprocess Context Transfer . . . . . . . . . . . . . 28
   2:  Interface Descriptions  . . . . . . . . . . . . . . . . . . 29
   2.1:  Credential management calls . . . . . . . . . . . . . . . 31
   2.1.1:  GSS_Acquire_cred call . . . . . . . . . . . . . . . . . 31
   2.1.2:  GSS_Release_cred call . . . . . . . . . . . . . . . . . 34
   2.1.3:  GSS_Inquire_cred call . . . . . . . . . . . . . . . . . 35
   2.1.4:  GSS_Add_cred call . . . . . . . . . . . . . . . . . . . 37
   2.1.5:  GSS_Inquire_cred_by_mech call . . . . . . . . . . . . . 40
   2.2:  Context-level calls . . . . . . . . . . . . . . . . . . . 41
   2.2.1:  GSS_Init_sec_context call . . . . . . . . . . . . . . . 42
   2.2.2:  GSS_Accept_sec_context call . . . . . . . . . . . . . . 49
   2.2.3:  GSS_Delete_sec_context call . . . . . . . . . . . . . . 53
   2.2.4:  GSS_Process_context_token call  . . . . . . . . . . . . 54
   2.2.5:  GSS_Context_time call . . . . . . . . . . . . . . . . . 55
   2.2.6:  GSS_Inquire_context call  . . . . . . . . . . . . . . . 56
   2.2.7:  GSS_Wrap_size_limit call  . . . . . . . . . . . . . . . 57
   2.2.8:  GSS_Export_sec_context call . . . . . . . . . . . . . . 59
   2.2.9:  GSS_Import_sec_context call . . . . . . . . . . . . . . 61
   2.3:  Per-message calls . . . . . . . . . . . . . . . . . . . . 62
   2.3.1:  GSS_GetMIC call . . . . . . . . . . . . . . . . . . . . 63
   2.3.2:  GSS_VerifyMIC call  . . . . . . . . . . . . . . . . . . 64
   2.3.3:  GSS_Wrap call . . . . . . . . . . . . . . . . . . . . . 65
   2.3.4:  GSS_Unwrap call . . . . . . . . . . . . . . . . . . . . 66



Linn                        Standards Track                     [Page 2]

RFC 2743                        GSS-API                     January 2000


   2.4:  Support calls . . . . . . . . . . . . . . . . . . . . . . 68
   2.4.1:  GSS_Display_status call . . . . . . . . . . . . . . . . 68
   2.4.2:  GSS_Indicate_mechs call . . . . . . . . . . . . . . . . 69
   2.4.3:  GSS_Compare_name call . . . . . . . . . . . . . . . . . 70
   2.4.4:  GSS_Display_name call . . . . . . . . . . . . . . . . . 71
   2.4.5:  GSS_Import_name call  . . . . . . . . . . . . . . . . . 72
   2.4.6:  GSS_Release_name call . . . . . . . . . . . . . . . . . 73
   2.4.7:  GSS_Release_buffer call . . . . . . . . . . . . . . . . 74
   2.4.8:  GSS_Release_OID_set call  . . . . . . . . . . . . . . . 74
   2.4.9:  GSS_Create_empty_OID_set call . . . . . . . . . . . . . 75
   2.4.10: GSS_Add_OID_set_member call . . . . . . . . . . . . . . 76
   2.4.11: GSS_Test_OID_set_member call  . . . . . . . . . . . . . 76
   2.4.12: GSS_Inquire_names_for_mech call . . . . . . . . . . . . 77
   2.4.13: GSS_Inquire_mechs_for_name call . . . . . . . . . . . . 77
   2.4.14: GSS_Canonicalize_name call  . . . . . . . . . . . . . . 78
   2.4.15: GSS_Export_name call  . . . . . . . . . . . . . . . . . 79
   2.4.16: GSS_Duplicate_name call . . . . . . . . . . . . . . . . 80
   3: Data Structure Definitions for GSS-V2 Usage  . . . . . . . . 81
   3.1: Mechanism-Independent Token Format . . . . . . . . . . . . 81
   3.2: Mechanism-Independent Exported Name Object Format  . . . . 84
   4: Name Type Definitions  . . . . . . . . . . . . . . . . . . . 85
   4.1: Host-Based Service Name Form . . . . . . . . . . . . . . . 85
   4.2: User Name Form . . . . . . . . . . . . . . . . . . . . . . 86
   4.3: Machine UID Form . . . . . . . . . . . . . . . . . . . . . 87
   4.4: String UID Form  . . . . . . . . . . . . . . . . . . . . . 87
   4.5: Anonymous Nametype . . . . . . . . . . . . . . . . . . . . 87
   4.6: GSS_C_NO_OID . . . . . . . . . . . . . . . . . . . . . . . 88
   4.7: Exported Name Object . . . . . . . . . . . . . . . . . . . 88
   4.8: GSS_C_NO_NAME  . . . . . . . . . . . . . . . . . . . . . . 88
   5:  Mechanism-Specific Example Scenarios  . . . . . . . . . . . 88
   5.1: Kerberos V5, single-TGT  . . . . . . . . . . . . . . . . . 89
   5.2: Kerberos V5, double-TGT  . . . . . . . . . . . . . . . . . 89
   5.3:  X.509 Authentication Framework  . . . . . . . . . . . . . 90
   6:  Security Considerations . . . . . . . . . . . . . . . . . . 91
   7:  Related Activities  . . . . . . . . . . . . . . . . . . . . 92
   8:  Referenced Documents  . . . . . . . . . . . . . . . . . . . 93
   Appendix A: Mechanism Design Constraints  . . . . . . . . . . . 94
   Appendix B: Compatibility with GSS-V1 . . . . . . . . . . . . . 94
   Appendix C: Changes Relative to RFC-2078  . . . . . . . . . . . 96
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . .100
   Full Copyright Statement  . . . . . . . . . . . . . . . . . . .101










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1: GSS-API Characteristics and Concepts

   GSS-API operates in the following paradigm.  A typical GSS-API caller
   is itself a communications protocol, calling on GSS-API in order to
   protect its communications with authentication, integrity, and/or
   confidentiality security services.  A GSS-API caller accepts tokens
   provided to it by its local GSS-API implementation and transfers the
   tokens to a peer on a remote system; that peer passes the received
   tokens to its local GSS-API implementation for processing. The
   security services available through GSS-API in this fashion are
   implementable (and have been implemented) over a range of underlying
   mechanisms based on secret-key and public-key cryptographic
   technologies.

   The GSS-API separates the operations of initializing a security
   context between peers, achieving peer entity authentication
   (GSS_Init_sec_context() and GSS_Accept_sec_context() calls), from the
   operations of providing per-message data origin authentication and
   data integrity protection (GSS_GetMIC() and GSS_VerifyMIC() calls)
   for messages subsequently transferred in conjunction with that
   context.  (The definition for the peer entity authentication service,
   and other definitions used in this document, corresponds to that
   provided in [ISO-7498-2].) When establishing a security context, the
   GSS-API enables a context initiator to optionally permit its
   credentials to be delegated, meaning that the context acceptor may
   initiate further security contexts on behalf of the initiating
   caller. Per-message GSS_Wrap() and GSS_Unwrap() calls provide the
   data origin authentication and data integrity services which
   GSS_GetMIC() and GSS_VerifyMIC() offer, and also support selection of
   confidentiality services as a caller option. Additional calls provide
   supportive functions to the GSS-API's users.

   The following paragraphs provide an example illustrating the
   dataflows involved in use of the GSS-API by a client and server in a
   mechanism-independent fashion, establishing a security context and
   transferring a protected message. The example assumes that credential
   acquisition has already been completed.  The example also assumes
   that the underlying authentication technology is capable of
   authenticating a client to a server using elements carried within a
   single token, and of authenticating the server to the client (mutual
   authentication) with a single returned token; this assumption holds
   for some presently-documented CAT mechanisms but is not necessarily
   true for other cryptographic technologies and associated protocols.

   The client calls GSS_Init_sec_context() to establish a security
   context to the server identified by targ_name, and elects to set the
   mutual_req_flag so that mutual authentication is performed in the
   course of context establishment. GSS_Init_sec_context() returns an



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   output_token to be passed to the server, and indicates
   GSS_S_CONTINUE_NEEDED status pending completion of the mutual
   authentication sequence. Had mutual_req_flag not been set, the
   initial call to GSS_Init_sec_context() would have returned
   GSS_S_COMPLETE status. The client sends the output_token to the
   server.

   The server passes the received token as the input_token parameter to
   GSS_Accept_sec_context().  GSS_Accept_sec_context indicates
   GSS_S_COMPLETE status, provides the client's authenticated identity
   in the src_name result, and provides an output_token to be passed to
   the client. The server sends the output_token to the client.

   The client passes the received token as the input_token parameter to
   a successor call to GSS_Init_sec_context(), which processes data
   included in the token in order to achieve mutual authentication from
   the client's viewpoint. This call to GSS_Init_sec_context() returns
   GSS_S_COMPLETE status, indicating successful mutual authentication
   and the completion of context establishment for this example.

   The client generates a data message and passes it to GSS_Wrap().
   GSS_Wrap() performs data origin authentication, data integrity, and
   (optionally) confidentiality processing on the message and
   encapsulates the result into output_message, indicating
   GSS_S_COMPLETE status. The client sends the output_message to the
   server.

   The server passes the received message to GSS_Unwrap().  GSS_Unwrap()
   inverts the encapsulation performed by GSS_Wrap(), deciphers the
   message if the optional confidentiality feature was applied, and
   validates the data origin authentication and data integrity checking
   quantities. GSS_Unwrap() indicates successful validation by returning
   GSS_S_COMPLETE status along with the resultant output_message.

   For purposes of this example, we assume that the server knows by
   out-of-band means that this context will have no further use after
   one protected message is transferred from client to server. Given
   this premise, the server now calls GSS_Delete_sec_context() to flush
   context-level information.  Optionally, the server-side application
   may provide a token buffer to GSS_Delete_sec_context(), to receive a
   context_token to be transferred to the client in order to request
   that client-side context-level information be deleted.

   If a context_token is transferred, the client passes the
   context_token to GSS_Process_context_token(), which returns
   GSS_S_COMPLETE status after deleting context-level information at the
   client system.




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   The GSS-API design assumes and addresses several basic goals,
   including:

      Mechanism independence: The GSS-API defines an interface to
      cryptographically implemented strong authentication and other
      security services at a generic level which is independent of
      particular underlying mechanisms. For example, GSS-API-provided
      services have been implemented using secret-key technologies
      (e.g., Kerberos, per [RFC-1964]) and with public-key approaches
      (e.g., SPKM, per [RFC-2025]).

      Protocol environment independence: The GSS-API is independent of
      the communications protocol suites with which it is employed,
      permitting use in a broad range of protocol environments. In
      appropriate environments, an intermediate implementation "veneer"
      which is oriented to a particular communication protocol may be
      interposed between applications which call that protocol and the
      GSS-API (e.g., as defined in [RFC-2203] for Open Network Computing
      Remote Procedure Call (RPC)), thereby invoking GSS-API facilities
      in conjunction with that protocol's communications invocations.

      Protocol association independence: The GSS-API's security context
      construct is independent of communications protocol association
      constructs. This characteristic allows a single GSS-API
      implementation to be utilized by a variety of invoking protocol
      modules on behalf of those modules' calling applications. GSS-API
      services can also be invoked directly by applications, wholly
      independent of protocol associations.

      Suitability to a range of implementation placements: GSS-API
      clients are not constrained to reside within any Trusted Computing
      Base (TCB) perimeter defined on a system where the GSS-API is
      implemented; security services are specified in a manner suitable
      to both intra-TCB and extra-TCB callers.

1.1: GSS-API Constructs

   This section describes the basic elements comprising the GSS-API.

1.1.1:  Credentials

1.1.1.1: Credential Constructs and Concepts

   Credentials provide the prerequisites which permit GSS-API peers to
   establish security contexts with each other. A caller may designate
   that the credential elements which are to be applied for context
   initiation or acceptance be selected by default.  Alternately, those
   GSS-API callers which need to make explicit selection of particular



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   credentials structures may make references to those credentials
   through GSS-API-provided credential handles ("cred_handles").  In all
   cases, callers' credential references are indirect, mediated by GSS-
   API implementations and not requiring callers to access the selected
   credential elements.

   A single credential structure may be used to initiate outbound
   contexts and to accept inbound contexts. Callers needing to operate
   in only one of these modes may designate this fact when credentials
   are acquired for use, allowing underlying mechanisms to optimize
   their processing and storage requirements. The credential elements
   defined by a particular mechanism may contain multiple cryptographic
   keys, e.g., to enable authentication and message encryption to be
   performed with different algorithms.

   A GSS-API credential structure may contain multiple credential
   elements, each containing mechanism-specific information for a
   particular underlying mechanism (mech_type), but the set of elements
   within a given credential structure represent a common entity.  A
   credential structure's contents will vary depending on the set of
   mech_types supported by a particular GSS-API implementation. Each
   credential element identifies the data needed by its mechanism in
   order to establish contexts on behalf of a particular principal, and
   may contain separate credential references for use in context
   initiation and context acceptance.  Multiple credential elements
   within a given credential having overlapping combinations of
   mechanism, usage mode, and validity period are not permitted.

   Commonly, a single mech_type will be used for all security contexts
   established by a particular initiator to a particular target. A major
   motivation for supporting credential sets representing multiple
   mech_types is to allow initiators on systems which are equipped to
   handle multiple types to initiate contexts to targets on other
   systems which can accommodate only a subset of the set supported at
   the initiator's system.

1.1.1.2: Credential Management

   It is the responsibility of underlying system-specific mechanisms and
   OS functions below the GSS-API to ensure that the ability to acquire
   and use credentials associated with a given identity is constrained
   to appropriate processes within a system. This responsibility should
   be taken seriously by implementors, as the ability for an entity to
   utilize a principal's credentials is equivalent to the entity's
   ability to successfully assert that principal's identity.






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   Once a set of GSS-API credentials is established, the transferability
   of that credentials set to other processes or analogous constructs
   within a system is a local matter, not defined by the GSS-API. An
   example local policy would be one in which any credentials received
   as a result of login to a given user account, or of delegation of
   rights to that account, are accessible by, or transferable to,
   processes running under that account.

   The credential establishment process (particularly when performed on
   behalf of users rather than server processes) is likely to require
   access to passwords or other quantities which should be protected
   locally and exposed for the shortest time possible. As a result, it
   will often be appropriate for preliminary credential establishment to
   be performed through local means at user login time, with the
   result(s) cached for subsequent reference. These preliminary
   credentials would be set aside (in a system-specific fashion) for
   subsequent use, either:

      to be accessed by an invocation of the GSS-API GSS_Acquire_cred()
      call, returning an explicit handle to reference that credential

      to comprise default credential elements to be installed, and to be
      used when default credential behavior is requested on behalf of a
      process

1.1.1.3: Default Credential Resolution

   The GSS_Init_sec_context() and GSS_Accept_sec_context() routines
   allow the value GSS_C_NO_CREDENTIAL to be specified as their
   credential handle parameter.  This special credential handle
   indicates a desire by the application to act as a default principal.
   In support of application portability, support for the default
   resolution behavior described below for initiator credentials
   (GSS_Init_sec_context() usage) is mandated; support for the default
   resolution behavior described below for acceptor credentials
   (GSS_Accept_sec_context() usage) is recommended. If default
   credential resolution fails, GSS_S_NO_CRED status is to be returned.

      GSS_Init_sec_context:

         (i) If there is only a single principal capable of initiating
         security contexts that the application is authorized to act on
         behalf of, then that principal shall be used, otherwise








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         (ii) If the platform maintains a concept of a default network-
         identity, and if the application is authorized to act on behalf
         of that identity for the purpose of initiating security
         contexts, then the principal corresponding to that identity
         shall be used, otherwise

         (iii) If the platform maintains a concept of a default local
         identity, and provides a means to map local identities into
         network-identities, and if the application is authorized to act
         on behalf of the network-identity image of the default local
         identity for the purpose of initiating security contexts, then
         the principal corresponding to that identity shall be used,
         otherwise

         (iv) A user-configurable default identity should be used.

      GSS_Accept_sec_context:

         (i) If there is only a single authorized principal identity
         capable of accepting security contexts, then that principal
         shall be used, otherwise

         (ii) If the mechanism can determine the identity of the target
         principal by examining the context-establishment token, and if
         the accepting application is authorized to act as that
         principal for the purpose of accepting security contexts, then
         that principal identity shall be used, otherwise

         (iii) If the mechanism supports context acceptance by any
         principal, and mutual authentication was not requested, any
         principal that the application is authorized to accept security
         contexts under may be used, otherwise

         (iv) A user-configurable default identity shall be used.

   The purpose of the above rules is to allow security contexts to be
   established by both initiator and acceptor using the default behavior
   wherever possible.  Applications requesting default behavior are
   likely to be more portable across mechanisms and platforms than those
   that use GSS_Acquire_cred() to request a specific identity.

1.1.2: Tokens

   Tokens are data elements transferred between GSS-API callers, and are
   divided into two classes. Context-level tokens are exchanged in order
   to establish and manage a security context between peers. Per-message
   tokens relate to an established context and are exchanged to provide




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   protective security services (i.e., data origin authentication,
   integrity, and optional confidentiality) for corresponding data
   messages.

   The first context-level token obtained from GSS_Init_sec_context() is
   required to indicate at its very beginning a globally-interpretable
   mechanism identifier, i.e., an Object Identifier (OID) of the
   security mechanism. The remaining part of this token as well as the
   whole content of all other tokens are specific to the particular
   underlying mechanism used to support the GSS-API. Section 3.1 of this
   document provides, for designers of GSS-API mechanisms, the
   description of the header of the first context-level token which is
   then followed by mechanism-specific information.

   Tokens' contents are opaque from the viewpoint of GSS-API callers.
   They are generated within the GSS-API implementation at an end
   system, provided to a GSS-API caller to be transferred to the peer
   GSS-API caller at a remote end system, and processed by the GSS-API
   implementation at that remote end system.

   Context-level tokens may be output by GSS-API calls (and should be
   transferred to GSS-API peers) whether or not the calls' status
   indicators indicate successful completion.  Per-message tokens, in
   contrast, are to be returned only upon successful completion of per-
   message calls. Zero-length tokens are never returned by GSS routines
   for transfer to a peer. Token transfer may take place in an in-band
   manner, integrated into the same protocol stream used by the GSS-API
   callers for other data transfers, or in an out-of-band manner across
   a logically separate channel.

   Different GSS-API tokens are used for different purposes (e.g.,
   context initiation, context acceptance, protected message data on an
   established context), and it is the responsibility of a GSS-API
   caller receiving tokens to distinguish their types, associate them
   with corresponding security contexts, and pass them to appropriate
   GSS-API processing routines.  Depending on the caller protocol
   environment, this distinction may be accomplished in several ways.

   The following examples illustrate means through which tokens' types
   may be distinguished:

      - implicit tagging based on state information (e.g., all tokens on
      a new association are considered to be context establishment
      tokens until context establishment is completed, at which point
      all tokens are considered to be wrapped data objects for that
      context),





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      - explicit tagging at the caller protocol level,

      - a hybrid of these approaches.

   Commonly, the encapsulated data within a token includes internal
   mechanism-specific tagging information, enabling mechanism-level
   processing modules to distinguish tokens used within the mechanism
   for different purposes.  Such internal mechanism-level tagging is
   recommended to mechanism designers, and enables mechanisms to
   determine whether a caller has passed a particular token for
   processing by an inappropriate GSS-API routine.

   Development of GSS-API mechanisms based on a particular underlying
   cryptographic technique and protocol (i.e., conformant to a specific
   GSS-API mechanism definition) does not necessarily imply that GSS-API
   callers using that GSS-API mechanism will be able to interoperate
   with peers invoking the same technique and protocol outside the GSS-
   API paradigm, or with peers implementing a different GSS-API
   mechanism based on the same underlying technology.  The format of
   GSS-API tokens defined in conjunction with a particular mechanism,
   and the techniques used to integrate those tokens into callers'
   protocols, may not be interoperable with the tokens used by non-GSS-
   API callers of the same underlying technique.

1.1.3:  Security Contexts

   Security contexts are established between peers, using credentials
   established locally in conjunction with each peer or received by
   peers via delegation. Multiple contexts may exist simultaneously
   between a pair of peers, using the same or different sets of
   credentials. Coexistence of multiple contexts using different
   credentials allows graceful rollover when credentials expire.
   Distinction among multiple contexts based on the same credentials
   serves applications by distinguishing different message streams in a
   security sense.

   The GSS-API is independent of underlying protocols and addressing
   structure, and depends on its callers to transport GSS-API-provided
   data elements. As a result of these factors, it is a caller
   responsibility to parse communicated messages, separating GSS-API-
   related data elements from caller-provided data.  The GSS-API is
   independent of connection vs. connectionless orientation of the
   underlying communications service.

   No correlation between security context and communications protocol
   association is dictated. (The optional channel binding facility,
   discussed in Section 1.1.6 of this document, represents an
   intentional exception to this rule, supporting additional protection



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   features within GSS-API supporting mechanisms.) This separation
   allows the GSS-API to be used in a wide range of communications
   environments, and also simplifies the calling sequences of the
   individual calls. In many cases (depending on underlying security
   protocol, associated mechanism, and availability of cached
   information), the state information required for context setup can be
   sent concurrently with initial signed user data, without interposing
   additional message exchanges.  Messages may be protected and
   transferred in both directions on an established GSS-API security
   context concurrently; protection of messages in one direction does
   not interfere with protection of messages in the reverse direction.

   GSS-API implementations are expected to retain inquirable context
   data on a context until the context is released by a caller, even
   after the context has expired, although underlying cryptographic data
   elements may be deleted after expiration in order to limit their
   exposure.

1.1.4:  Mechanism Types

   In order to successfully establish a security context with a target
   peer, it is necessary to identify an appropriate underlying mechanism
   type (mech_type) which both initiator and target peers support. The
   definition of a mechanism embodies not only the use of a particular
   cryptographic technology (or a hybrid or choice among alternative
   cryptographic technologies), but also definition of the syntax and
   semantics of data element exchanges which that mechanism will employ
   in order to support security services.

   It is recommended that callers initiating contexts specify the
   "default" mech_type value, allowing system-specific functions within
   or invoked by the GSS-API implementation to select the appropriate
   mech_type, but callers may direct that a particular mech_type be
   employed when necessary.

   For GSS-API purposes, the phrase "negotiating mechanism" refers to a
   mechanism which itself performs negotiation in order to select a
   concrete mechanism which is shared between peers and is then used for
   context establishment.  Only those mechanisms which are defined in
   their specifications as negotiating mechanisms are to yield selected
   mechanisms with different identifier values than the value which is
   input by a GSS-API caller, except for the case of a caller requesting
   the "default" mech_type.

   The means for identifying a shared mech_type to establish a security
   context with a peer will vary in different environments and
   circumstances; examples include (but are not limited to):




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      use of a fixed mech_type, defined by configuration, within an
      environment

      syntactic convention on a target-specific basis, through
      examination of a target's name lookup of a target's name in a
      naming service or other database in order to identify mech_types
      supported by that target

      explicit negotiation between GSS-API callers in advance of
      security context setup

      use of a negotiating mechanism

   When transferred between GSS-API peers, mech_type specifiers (per
   Section 3 of this document, represented as Object Identifiers (OIDs))
   serve to qualify the interpretation of associated tokens. (The
   structure and encoding of Object Identifiers is defined in [ISOIEC-
   8824] and [ISOIEC-8825].) Use of hierarchically structured OIDs
   serves to preclude ambiguous interpretation of mech_type specifiers.
   The OID representing the DASS ([RFC-1507]) MechType, for example, is
   1.3.12.2.1011.7.5, and that of the Kerberos V5 mechanism ([RFC-
   1964]), having been advanced to the level of Proposed Standard, is
   1.2.840.113554.1.2.2.

1.1.5:  Naming

   The GSS-API avoids prescribing naming structures, treating the names
   which are transferred across the interface in order to initiate and
   accept security contexts as opaque objects.  This approach supports
   the GSS-API's goal of implementability atop a range of underlying
   security mechanisms, recognizing the fact that different mechanisms
   process and authenticate names which are presented in different
   forms. Generalized services offering translation functions among
   arbitrary sets of naming environments are outside the scope of the
   GSS-API; availability and use of local conversion functions to
   translate among the naming formats supported within a given end
   system is anticipated.

   Different classes of name representations are used in conjunction
   with different GSS-API parameters:

      - Internal form (denoted in this document by INTERNAL NAME),
      opaque to callers and defined by individual GSS-API
      implementations.  GSS-API implementations supporting multiple
      namespace types must maintain internal tags to disambiguate the
      interpretation of particular names.  A Mechanism Name (MN) is a
      special case of INTERNAL NAME, guaranteed to contain elements




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      corresponding to one and only one mechanism; calls which are
      guaranteed to emit MNs or which require MNs as input are so
      identified within this specification.

      - Contiguous string ("flat") form (denoted in this document by
      OCTET STRING); accompanied by OID tags identifying the namespace
      to which they correspond.  Depending on tag value, flat names may
      or may not be printable strings for direct acceptance from and
      presentation to users. Tagging of flat names allows GSS-API
      callers and underlying GSS-API mechanisms to disambiguate name
      types and to determine whether an associated name's type is one
      which they are capable of processing, avoiding aliasing problems
      which could result from misinterpreting a name of one type as a
      name of another type.

      - The GSS-API Exported Name Object, a special case of flat name
      designated by a reserved OID value, carries a canonicalized form
      of a name suitable for binary comparisons.

   In addition to providing means for names to be tagged with types,
   this specification defines primitives to support a level of naming
   environment independence for certain calling applications. To provide
   basic services oriented towards the requirements of callers which
   need not themselves interpret the internal syntax and semantics of
   names, GSS-API calls for name comparison (GSS_Compare_name()),
   human-readable display (GSS_Display_name()), input conversion
   (GSS_Import_name()), internal name deallocation (GSS_Release_name()),
   and internal name duplication (GSS_Duplicate_name()) functions are
   defined. (It is anticipated that these proposed GSS-API calls will be
   implemented in many end systems based on system-specific name
   manipulation primitives already extant within those end systems;
   inclusion within the GSS-API is intended to offer GSS-API callers a
   portable means to perform specific operations, supportive of
   authorization and audit requirements, on authenticated names.)

   GSS_Import_name() implementations can, where appropriate, support
   more than one printable syntax corresponding to a given namespace
   (e.g., alternative printable representations for X.500 Distinguished
   Names), allowing flexibility for their callers to select among
   alternative representations. GSS_Display_name() implementations
   output a printable syntax selected as appropriate to their
   operational environments; this selection is a local matter. Callers
   desiring portability across alternative printable syntaxes should
   refrain from implementing comparisons based on printable name forms
   and should instead use the GSS_Compare_name()  call to determine
   whether or not one internal-format name matches another.





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   When used in large access control lists, the overhead of invoking
   GSS_Import_name() and GSS_Compare_name() on each name from the ACL
   may be prohibitive.  As an alternative way of supporting this case,
   GSS-API defines a special form of the contiguous string name which
   may be compared directly (e.g., with memcmp()).  Contiguous names
   suitable for comparison are generated by the GSS_Export_name()
   routine, which requires an MN as input.  Exported names may be re-
   imported by the GSS_Import_name() routine, and the resulting internal
   name will also be an MN.  The symbolic constant GSS_C_NT_EXPORT_NAME
   identifies the "export name" type. Structurally, an exported name
   object consists of a header containing an OID identifying the
   mechanism that authenticated the name, and a trailer containing the
   name itself, where the syntax of the trailer is defined by the
   individual mechanism specification.  The precise format of an
   exported name is defined in Section 3.2 of this specification.

   Note that the results obtained by using GSS_Compare_name() will in
   general be different from those obtained by invoking
   GSS_Canonicalize_name() and GSS_Export_name(), and then comparing the
   exported names.  The first series of operations determines whether
   two (unauthenticated) names identify the same principal; the second
   whether a particular mechanism would authenticate them as the same
   principal.  These two operations will in general give the same
   results only for MNs.

   The following diagram illustrates the intended dataflow among name-
   related GSS-API processing routines.
























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                        GSS-API library defaults
                               |
                               |
                               V                         text, for
   text -------------->  internal_name (IN) -----------> display only
         import_name()          /          display_name()
                               /
                              /
                             /
    accept_sec_context()    /
          |                /
          |               /
          |              /  canonicalize_name()
          |             /
          |            /
          |           /
          |          /
          |         /
          |        |
          V        V     <---------------------
    single mechanism        import_name()         exported name: flat
    internal_name (MN)                            binary "blob" usable
                         ---------------------->  for access control
                            export_name()

1.1.6:  Channel Bindings

   The GSS-API accommodates the concept of caller-provided channel
   binding ("chan_binding") information.  Channel bindings are used to
   strengthen the quality with which peer entity authentication is
   provided during context establishment, by limiting the scope within
   which an intercepted context establishment token can be reused by an
   attacker. Specifically, they enable GSS-API callers to bind the
   establishment of a security context to relevant characteristics
   (e.g., addresses, transformed representations of encryption keys) of
   the underlying communications channel, of protection mechanisms
   applied to that communications channel, and to application-specific
   data.

   The caller initiating a security context must determine the
   appropriate channel binding values to provide as input to the
   GSS_Init_sec_context() call, and consistent values must be provided
   to GSS_Accept_sec_context() by the context's target, in order for
   both peers' GSS-API mechanisms to validate that received tokens
   possess correct channel-related characteristics. Use or non-use of
   the GSS-API channel binding facility is a caller option.  GSS-API
   mechanisms can operate in an environment where NULL channel bindings
   are presented; mechanism implementors are encouraged, but not



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   required, to make use of caller-provided channel binding data within
   their mechanisms. Callers should not assume that underlying
   mechanisms provide confidentiality protection for channel binding
   information.

   When non-NULL channel bindings are provided by callers, certain
   mechanisms can offer enhanced security value by interpreting the
   bindings' content (rather than simply representing those bindings, or
   integrity check values computed on them, within tokens) and will
   therefore depend on presentation of specific data in a defined
   format. To this end, agreements among mechanism implementors are
   defining conventional interpretations for the contents of channel
   binding arguments, including address specifiers (with content
   dependent on communications protocol environment) for context
   initiators and acceptors. (These conventions are being incorporated
   in GSS-API mechanism specifications and into the GSS-API C language
   bindings specification.) In order for GSS-API callers to be portable
   across multiple mechanisms and achieve the full security
   functionality which each mechanism can provide, it is strongly
   recommended that GSS-API callers provide channel bindings consistent
   with these conventions and those of the networking environment in
   which they operate.

1.2:  GSS-API Features and Issues

   This section describes aspects of GSS-API operations, of the security
   services which the GSS-API provides, and provides commentary on
   design issues.

1.2.1:  Status Reporting and Optional Service Support

1.2.1.1: Status Reporting

   Each GSS-API call provides two status return values. Major_status
   values provide a mechanism-independent indication of call status
   (e.g., GSS_S_COMPLETE, GSS_S_FAILURE, GSS_S_CONTINUE_NEEDED),
   sufficient to drive normal control flow within the caller in a
   generic fashion. Table 1 summarizes the defined major_status return
   codes in tabular fashion.

   Sequencing-related informatory major_status codes
   (GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN, and
   GSS_S_GAP_TOKEN) can be indicated in conjunction with either
   GSS_S_COMPLETE or GSS_S_FAILURE status for GSS-API per-message calls.
   For context establishment calls, these sequencing-related codes will
   be indicated only in conjunction with GSS_S_FAILURE status (never in





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   conjunction with GSS_S_COMPLETE or GSS_S_CONTINUE_NEEDED), and,
   therefore, always correspond to fatal failures if encountered during
   the context establishment phase.

   Table 1: GSS-API Major Status Codes

   FATAL ERROR CODES

   GSS_S_BAD_BINDINGS            channel binding mismatch
   GSS_S_BAD_MECH                unsupported mechanism requested
   GSS_S_BAD_NAME                invalid name provided
   GSS_S_BAD_NAMETYPE            name of unsupported type provided
   GSS_S_BAD_STATUS              invalid input status selector
   GSS_S_BAD_SIG                 token had invalid integrity check
   GSS_S_BAD_MIC                   preferred alias for GSS_S_BAD_SIG
   GSS_S_CONTEXT_EXPIRED         specified security context expired
   GSS_S_CREDENTIALS_EXPIRED     expired credentials detected
   GSS_S_DEFECTIVE_CREDENTIAL    defective credential detected
   GSS_S_DEFECTIVE_TOKEN         defective token detected
   GSS_S_FAILURE                 failure, unspecified at GSS-API
                                   level
   GSS_S_NO_CONTEXT              no valid security context specified
   GSS_S_NO_CRED                 no valid credentials provided
   GSS_S_BAD_QOP                 unsupported QOP value
   GSS_S_UNAUTHORIZED            operation unauthorized
   GSS_S_UNAVAILABLE             operation unavailable
   GSS_S_DUPLICATE_ELEMENT       duplicate credential element requested
   GSS_S_NAME_NOT_MN             name contains multi-mechanism elements

   INFORMATORY STATUS CODES

   GSS_S_COMPLETE                normal completion
   GSS_S_CONTINUE_NEEDED         continuation call to routine
                                  required
   GSS_S_DUPLICATE_TOKEN         duplicate per-message token
                                  detected
   GSS_S_OLD_TOKEN               timed-out per-message token
                                  detected
   GSS_S_UNSEQ_TOKEN             reordered (early) per-message token
                                  detected
   GSS_S_GAP_TOKEN               skipped predecessor token(s)
                                  detected

   Minor_status provides more detailed status information which may
   include status codes specific to the underlying security mechanism.
   Minor_status values are not specified in this document.





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   GSS_S_CONTINUE_NEEDED major_status returns, and optional message
   outputs, are provided in GSS_Init_sec_context() and
   GSS_Accept_sec_context() calls so that different mechanisms'
   employment of different numbers of messages within their
   authentication sequences need not be reflected in separate code paths
   within calling applications. Instead, such cases are accommodated
   with sequences of continuation calls to GSS_Init_sec_context()  and
   GSS_Accept_sec_context().  The same facility is used to encapsulate
   mutual authentication within the GSS-API's context initiation calls.

   For mech_types which require interactions with third-party servers in
   order to establish a security context, GSS-API context establishment
   calls may block pending completion of such third-party interactions.
   On the other hand, no GSS-API calls pend on serialized interactions
   with GSS-API peer entities.  As a result, local GSS-API status
   returns cannot reflect unpredictable or asynchronous exceptions
   occurring at remote peers, and reflection of such status information
   is a caller responsibility outside the GSS-API.

1.2.1.2: Optional Service Support

   A context initiator may request various optional services at context
   establishment time. Each of these services is requested by setting a
   flag in the req_flags input parameter to GSS_Init_sec_context().

   The optional services currently defined are:

      - Delegation - The (usually temporary) transfer of rights from
      initiator to acceptor, enabling the acceptor to authenticate
      itself as an agent of the initiator.

      - Mutual Authentication - In addition to the initiator
      authenticating its identity to the context acceptor, the context
      acceptor should also authenticate itself to the initiator.

      - Replay detection - In addition to providing message integrity
      services, GSS_GetMIC() and GSS_Wrap() should include message
      numbering information to enable GSS_VerifyMIC() and GSS_Unwrap()
      to detect if a message has been duplicated.

      - Out-of-sequence detection - In addition to providing message
      integrity services, GSS_GetMIC() and GSS_Wrap() should include
      message sequencing information to enable GSS_VerifyMIC() and
      GSS_Unwrap() to detect if a message has been received out of
      sequence.






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      - Anonymous authentication - The establishment of the security
      context should not reveal the initiator's identity to the context
      acceptor.

      - Available per-message confidentiality - requests that per-
      message confidentiality services be available on the context.

      - Available per-message integrity - requests that per-message
      integrity services be available on the context.

   Any currently undefined bits within such flag arguments should be
   ignored by GSS-API implementations when presented by an application,
   and should be set to zero when returned to the application by the
   GSS-API implementation.

   Some mechanisms may not support all optional services, and some
   mechanisms may only support some services in conjunction with others.
   Both GSS_Init_sec_context() and GSS_Accept_sec_context() inform the
   applications which services will be available from the context when
   the establishment phase is complete, via the ret_flags output
   parameter.  In general, if the security mechanism is capable of
   providing a requested service, it should do so, even if additional
   services must be enabled in order to provide the requested service.
   If the mechanism is incapable of providing a requested service, it
   should proceed without the service, leaving the application to abort
   the context establishment process if it considers the requested
   service to be mandatory.

   Some mechanisms may specify that support for some services is
   optional, and that implementors of the mechanism need not provide it.
   This is most commonly true of the confidentiality service, often
   because of legal restrictions on the use of data-encryption, but may
   apply to any of the services.  Such mechanisms are required to send
   at least one token from acceptor to initiator during context
   establishment when the initiator indicates a desire to use such a
   service, so that the initiating GSS-API can correctly indicate
   whether the service is supported by the acceptor's GSS-API.

1.2.2: Per-Message Security Service Availability

   When a context is established, two flags are returned to indicate the
   set of per-message protection security services which will be
   available on the context:

      the integ_avail flag indicates whether per-message integrity and
      data origin authentication services are available





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      the conf_avail flag indicates whether per-message confidentiality
      services are available, and will never be returned TRUE unless the
      integ_avail flag is also returned TRUE

   GSS-API callers desiring per-message security services should check
   the values of these flags at context establishment time, and must be
   aware that a returned FALSE value for integ_avail means that
   invocation of GSS_GetMIC() or GSS_Wrap() primitives on the associated
   context will apply no cryptographic protection to user data messages.

   The GSS-API per-message integrity and data origin authentication
   services provide assurance to a receiving caller that protection was
   applied to a message by the caller's peer on the security context,
   corresponding to the entity named at context initiation.  The GSS-API
   per-message confidentiality service provides assurance to a sending
   caller that the message's content is protected from access by
   entities other than the context's named peer.

   The GSS-API per-message protection service primitives, as the
   category name implies, are oriented to operation at the granularity
   of protocol data units. They perform cryptographic operations on the
   data units, transfer cryptographic control information in tokens,
   and, in the case of GSS_Wrap(), encapsulate the protected data unit.
   As such, these primitives are not oriented to efficient data
   protection for stream-paradigm protocols (e.g., Telnet) if
   cryptography must be applied on an octet-by-octet basis.

1.2.3: Per-Message Replay Detection and Sequencing

   Certain underlying mech_types offer support for replay detection
   and/or sequencing of messages transferred on the contexts they
   support. These optionally-selectable protection features are distinct
   from replay detection and sequencing features applied to the context
   establishment operation itself; the presence or absence of context-
   level replay or sequencing features is wholly a function of the
   underlying mech_type's capabilities, and is not selected or omitted
   as a caller option.

   The caller initiating a context provides flags (replay_det_req_flag
   and sequence_req_flag) to specify whether the use of per-message
   replay detection and sequencing features is desired on the context
   being established. The GSS-API implementation at the initiator system
   can determine whether these features are supported (and whether they
   are optionally selectable) as a function of the selected mechanism,
   without need for bilateral negotiation with the target. When enabled,
   these features provide recipients with indicators as a result of
   GSS-API processing of incoming messages, identifying whether those
   messages were detected as duplicates or out-of-sequence. Detection of



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   such events does not prevent a suspect message from being provided to
   a recipient; the appropriate course of action on a suspect message is
   a matter of caller policy.

   The semantics of the replay detection and sequencing services applied
   to received messages, as visible across the interface which the GSS-
   API provides to its clients, are as follows:

   When replay_det_state is TRUE, the possible major_status returns for
   well-formed and correctly signed messages are as follows:

      1. GSS_S_COMPLETE, without concurrent indication of
      GSS_S_DUPLICATE_TOKEN or GSS_S_OLD_TOKEN, indicates that the
      message was within the window (of time or sequence space) allowing
      replay events to be detected, and that the message was not a
      replay of a previously-processed message within that window.

      2. GSS_S_DUPLICATE_TOKEN indicates that the cryptographic
      checkvalue on the received message was correct, but that the
      message was recognized as a duplicate of a previously-processed
      message.  In addition to identifying duplicated tokens originated
      by a context's peer, this status may also be used to identify
      reflected copies of locally-generated tokens; it is recommended
      that mechanism designers include within their protocols facilities
      to detect and report such tokens.

      3. GSS_S_OLD_TOKEN indicates that the cryptographic checkvalue on
      the received message was correct, but that the message is too old
      to be checked for duplication.

   When sequence_state is TRUE, the possible major_status returns for
   well-formed and correctly signed messages are as follows:

      1. GSS_S_COMPLETE, without concurrent indication of
      GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN, or
      GSS_S_GAP_TOKEN, indicates that the message was within the window
      (of time or sequence space) allowing replay events to be detected,
      that the message was not a replay of a previously-processed
      message within that window, and that no predecessor sequenced
      messages are missing relative to the last received message (if
      any) processed on the context with a correct cryptographic
      checkvalue.

      2. GSS_S_DUPLICATE_TOKEN indicates that the integrity check value
      on the received message was correct, but that the message was
      recognized as a duplicate of a previously-processed message.  In
      addition to identifying duplicated tokens originated by a
      context's peer, this status may also be used to identify reflected



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      copies of locally-generated tokens; it is recommended that
      mechanism designers include within their protocols facilities to
      detect and report such tokens.

      3. GSS_S_OLD_TOKEN indicates that the integrity check value on the
      received message was correct, but that the token is too old to be
      checked for duplication.

      4. GSS_S_UNSEQ_TOKEN indicates that the cryptographic checkvalue
      on the received message was correct, but that it is earlier in a
      sequenced stream than a message already processed on the context.
      [Note: Mechanisms can be architected to provide a stricter form of
      sequencing service, delivering particular messages to recipients
      only after all predecessor messages in an ordered stream have been
      delivered.  This type of support is incompatible with the GSS-API
      paradigm in which recipients receive all messages, whether in
      order or not, and provide them (one at a time, without intra-GSS-
      API message buffering) to GSS-API routines for validation.  GSS-
      API facilities provide supportive functions, aiding clients to
      achieve strict message stream integrity in an efficient manner in
      conjunction with sequencing provisions in communications
      protocols, but the GSS-API does not offer this level of message
      stream integrity service by itself.]

      5. GSS_S_GAP_TOKEN indicates that the cryptographic checkvalue on
      the received message was correct, but that one or more predecessor
      sequenced messages have not been successfully processed relative
      to the last received message (if any) processed on the context
      with a correct cryptographic checkvalue.

   As the message stream integrity features (especially sequencing) may
   interfere with certain applications' intended communications
   paradigms, and since support for such features is likely to be
   resource intensive, it is highly recommended that mech_types
   supporting these features allow them to be activated selectively on
   initiator request when a context is established. A context initiator
   and target are provided with corresponding indicators
   (replay_det_state and sequence_state), signifying whether these
   features are active on a given context.

   An example mech_type supporting per-message replay detection could
   (when replay_det_state is TRUE) implement the feature as follows: The
   underlying mechanism would insert timestamps in data elements output
   by GSS_GetMIC() and GSS_Wrap(), and would maintain (within a time-
   limited window) a cache (qualified by originator-recipient pair)
   identifying received data elements processed by GSS_VerifyMIC() and
   GSS_Unwrap(). When this feature is active, exception status returns
   (GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN) will be provided when



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   GSS_VerifyMIC() or GSS_Unwrap() is presented with a message which is
   either a detected duplicate of a prior message or which is too old to
   validate against a cache of recently received messages.

1.2.4:  Quality of Protection

   Some mech_types provide their users with fine granularity control
   over the means used to provide per-message protection, allowing
   callers to trade off security processing overhead dynamically against
   the protection requirements of particular messages. A per-message
   quality-of-protection parameter (analogous to quality-of-service, or
   QOS) selects among different QOP options supported by that mechanism.
   On context establishment for a multi-QOP mech_type, context-level
   data provides the prerequisite data for a range of protection
   qualities.

   It is expected that the majority of callers will not wish to exert
   explicit mechanism-specific QOP control and will therefore request
   selection of a default QOP. Definitions of, and choices among, non-
   default QOP values are mechanism-specific, and no ordered sequences
   of QOP values can be assumed equivalent across different mechanisms.
   Meaningful use of non-default QOP values demands that callers be
   familiar with the QOP definitions of an underlying mechanism or
   mechanisms, and is therefore a non-portable construct.  The
   GSS_S_BAD_QOP major_status value is defined in order to indicate that
   a provided QOP value is unsupported for a security context, most
   likely because that value is unrecognized by the underlying
   mechanism.

   In the interests of interoperability, mechanisms which allow optional
   support of particular QOP values shall satisfy one of the following
   conditions.  Either:

      (i) All implementations of the mechanism are required to be
      capable of processing messages protected using any QOP value,
      regardless of whether they can apply protection corresponding to
      that QOP, or

      (ii) The set of mutually-supported receiver QOP values must be
      determined during context establishment, and messages may be
      protected by either peer using only QOP values from this
      mutually-supported set.

   NOTE: (i) is just a special-case of (ii), where implementations are
   required to support all QOP values on receipt.






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1.2.5: Anonymity Support

   In certain situations or environments, an application may wish to
   authenticate a peer and/or protect communications using GSS-API per-
   message services without revealing its own identity.  For example,
   consider an application which provides read access to a research
   database, and which permits queries by arbitrary requestors.  A
   client of such a service might wish to authenticate the service, to
   establish trust in the information received from it, but might not
   wish to disclose its identity to the service for privacy reasons.

   In ordinary GSS-API usage, a context initiator's identity is made
   available to the context acceptor as part of the context
   establishment process.  To provide for anonymity support, a facility
   (input anon_req_flag to GSS_Init_sec_context()) is provided through
   which context initiators may request that their identity not be
   provided to the context acceptor.  Mechanisms are not required to
   honor this request, but a caller will be informed (via returned
   anon_state indicator from GSS_Init_sec_context()) whether or not the
   request is honored. Note that authentication as the anonymous
   principal does not necessarily imply that credentials are not
   required in order to establish a context.

   Section 4.5 of this document defines the Object Identifier value used
   to identify an anonymous principal.

   Four possible combinations of anon_state and mutual_state are
   possible, with the following results:

      anon_state == FALSE, mutual_state == FALSE: initiator
      authenticated to target.

      anon_state == FALSE, mutual_state == TRUE: initiator authenticated
      to target, target authenticated to initiator.

      anon_state == TRUE, mutual_state == FALSE: initiator authenticated
      as anonymous principal to target.

      anon_state == TRUE, mutual_state == TRUE: initiator authenticated
      as anonymous principal to target, target authenticated to
      initiator.

1.2.6: Initialization

   No initialization calls (i.e., calls which must be invoked prior to
   invocation of other facilities in the interface) are defined in GSS-
   API.  As an implication of this fact, GSS-API implementations must
   themselves be self-initializing.



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1.2.7: Per-Message Protection During Context Establishment

   A facility is defined in GSS-V2 to enable protection and buffering of
   data messages for later transfer while a security context's
   establishment is in GSS_S_CONTINUE_NEEDED status, to be used in cases
   where the caller side already possesses the necessary session key to
   enable this processing. Specifically, a new state Boolean, called
   prot_ready_state, is added to the set of information returned by
   GSS_Init_sec_context(), GSS_Accept_sec_context(), and
   GSS_Inquire_context().

   For context establishment calls, this state Boolean is valid and
   interpretable when the associated major_status is either
   GSS_S_CONTINUE_NEEDED, or GSS_S_COMPLETE.  Callers of GSS-API (both
   initiators and acceptors) can assume that per-message protection (via
   GSS_Wrap(), GSS_Unwrap(), GSS_GetMIC() and GSS_VerifyMIC()) is
   available and ready for use if either: prot_ready_state == TRUE, or
   major_status == GSS_S_COMPLETE, though mutual authentication (if
   requested) cannot be guaranteed until GSS_S_COMPLETE is returned.
   Callers making use of per-message protection services in advance of
   GSS_S_COMPLETE status should be aware of the possibility that a
   subsequent context establishment step may fail, and that certain
   context data (e.g., mech_type) as returned for subsequent calls may
   change.

   This approach achieves full, transparent backward compatibility for
   GSS-API V1 callers, who need not even know of the existence of
   prot_ready_state, and who will get the expected behavior from
   GSS_S_COMPLETE, but who will not be able to use per-message
   protection before GSS_S_COMPLETE is returned.

   It is not a requirement that GSS-V2 mechanisms ever return TRUE
   prot_ready_state before completion of context establishment (indeed,
   some mechanisms will not evolve usable message protection keys,
   especially at the context acceptor, before context establishment is
   complete).  It is expected but not required that GSS-V2 mechanisms
   will return TRUE prot_ready_state upon completion of context
   establishment if they support per-message protection at all (however
   GSS-V2 applications should not assume that TRUE prot_ready_state will
   always be returned together with the GSS_S_COMPLETE major_status,
   since GSS-V2 implementations may continue to support GSS-V1 mechanism
   code, which will never return TRUE prot_ready_state).

   When prot_ready_state is returned TRUE, mechanisms shall also set
   those context service indicator flags (deleg_state, mutual_state,
   replay_det_state, sequence_state, anon_state, trans_state,
   conf_avail, integ_avail) which represent facilities confirmed, at
   that time, to be available on the context being established.  In



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   situations where prot_ready_state is returned before GSS_S_COMPLETE,
   it is possible that additional facilities may be confirmed and
   subsequently indicated when GSS_S_COMPLETE is returned.

1.2.8: Implementation Robustness

   This section recommends aspects of GSS-API implementation behavior in
   the interests of overall robustness.

   Invocation of GSS-API calls is to incur no undocumented side effects
   visible at the GSS-API level.

   If a token is presented for processing on a GSS-API security context
   and that token generates a fatal error in processing or is otherwise
   determined to be invalid for that context, the context's state should
   not be disrupted for purposes of processing subsequent valid tokens.

   Certain local conditions at a GSS-API implementation (e.g.,
   unavailability of memory) may preclude, temporarily or permanently,
   the successful processing of tokens on a GSS-API security context,
   typically generating GSS_S_FAILURE major_status returns along with
   locally-significant minor_status.  For robust operation under such
   conditions, the following recommendations are made:

      Failing calls should free any memory they allocate, so that
      callers may retry without causing further loss of resources.

      Failure of an individual call on an established context should not
      preclude subsequent calls from succeeding on the same context.

      Whenever possible, it should be possible for
      GSS_Delete_sec_context() calls to be successfully processed even
      if other calls cannot succeed, thereby enabling context-related
      resources to be released.

   A failure of GSS_GetMIC() or GSS_Wrap() due to an attempt to use an
   unsupported QOP will not interfere with context validity, nor shall
   such a failure impact the ability of the application to subsequently
   invoke GSS_GetMIC() or GSS_Wrap() using a supported QOP. Any state
   information concerning sequencing of outgoing messages shall be
   unchanged by an unsuccessful call of GSS_GetMIC() or GSS_Wrap().










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1.2.9: Delegation

   The GSS-API allows delegation to be controlled by the initiating
   application via a Boolean parameter to GSS_Init_sec_context(), the
   routine that establishes a security context.  Some mechanisms do not
   support delegation, and for such mechanisms attempts by an
   application to enable delegation are ignored.

   The acceptor of a security context for which the initiator enabled
   delegation will receive (via the delegated_cred_handle parameter of
   GSS_Accept_sec_context()) a credential handle that contains the
   delegated identity, and this credential handle may be used to
   initiate subsequent GSS-API security contexts as an agent or delegate
   of the initiator.  If the original initiator's identity is "A" and
   the delegate's identity is "B", then, depending on the underlying
   mechanism, the identity embodied by the delegated credential may be
   either "A" or "B acting for A".

   For many mechanisms that support delegation, a simple Boolean does
   not provide enough control.  Examples of additional aspects of
   delegation control that a mechanism might provide to an application
   are duration of delegation, network addresses from which delegation
   is valid, and constraints on the tasks that may be performed by a
   delegate.  Such controls are presently outside the scope of the GSS-
   API.  GSS-API implementations supporting mechanisms offering
   additional controls should provide extension routines that allow
   these controls to be exercised (perhaps by modifying the initiator's
   GSS-API credential prior to its use in establishing a context).
   However, the simple delegation control provided by GSS-API should
   always be able to over-ride other mechanism-specific delegation
   controls; if the application instructs GSS_Init_sec_context() that
   delegation is not desired, then the implementation must not permit
   delegation to occur.  This is an exception to the general rule that a
   mechanism may enable services even if they are not requested;
   delegation may only be provided at the explicit request of the
   application.

1.2.10: Interprocess Context Transfer

   GSS-API V2 provides routines (GSS_Export_sec_context() and
   GSS_Import_sec_context()) which allow a security context to be
   transferred between processes on a single machine.  The most common
   use for such a feature is a client-server design where the server is
   implemented as a single process that accepts incoming security
   contexts, which then launches child processes to deal with the data
   on these contexts.  In such a design, the child processes must have
   access to the security context data structure created within the




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   parent by its call to GSS_Accept_sec_context() so that they can use
   per-message protection services and delete the security context when
   the communication session ends.

   Since the security context data structure is expected to contain
   sequencing information, it is impractical in general to share a
   context between processes.  Thus GSS-API provides a call
   (GSS_Export_sec_context()) that the process which currently owns the
   context can call to declare that it has no intention to use the
   context subsequently, and to create an inter-process token containing
   information needed by the adopting process to successfully import the
   context.  After successful completion of this call, the original
   security context is made inaccessible to the calling process by GSS-
   API, and any context handles referring to this context are no longer
   valid.  The originating process transfers the inter-process token to
   the adopting process, which passes it to GSS_Import_sec_context(),
   and a fresh context handle is created such that it is functionally
   identical to the original context.

   The inter-process token may contain sensitive data from the original
   security context (including cryptographic keys).  Applications using
   inter-process tokens to transfer security contexts must take
   appropriate steps to protect these tokens in transit.
   Implementations are not required to support the inter-process
   transfer of security contexts.  The ability to transfer a security
   context is indicated when the context is created, by
   GSS_Init_sec_context() or GSS_Accept_sec_context() indicating a TRUE
   trans_state return value.

2:  Interface Descriptions

   This section describes the GSS-API's service interface, dividing the
   set of calls offered into four groups. Credential management calls
   are related to the acquisition and release of credentials by
   principals. Context-level calls are related to the management of
   security contexts between principals. Per-message calls are related
   to the protection of individual messages on established security
   contexts. Support calls provide ancillary functions useful to GSS-API
   callers. Table 2 groups and summarizes the calls in tabular fashion.

   Table 2:  GSS-API Calls

   CREDENTIAL MANAGEMENT

   GSS_Acquire_cred             acquire credentials for use
   GSS_Release_cred             release credentials after use
   GSS_Inquire_cred             display information about
                                credentials



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   GSS_Add_cred                 construct credentials incrementally
   GSS_Inquire_cred_by_mech     display per-mechanism credential
                                  information

   CONTEXT-LEVEL CALLS

   GSS_Init_sec_context         initiate outbound security context
   GSS_Accept_sec_context       accept inbound security context
   GSS_Delete_sec_context       flush context when no longer needed
   GSS_Process_context_token    process received control token on
                                  context
   GSS_Context_time             indicate validity time remaining on
                                     context
   GSS_Inquire_context          display information about context
   GSS_Wrap_size_limit          determine GSS_Wrap token size limit
   GSS_Export_sec_context       transfer context to other process
   GSS_Import_sec_context       import transferred context

   PER-MESSAGE CALLS

   GSS_GetMIC                   apply integrity check, receive as
                                  token separate from message
   GSS_VerifyMIC                validate integrity check token
                                  along with message
   GSS_Wrap                     sign, optionally encrypt,
                                  encapsulate
   GSS_Unwrap                   decapsulate, decrypt if needed,
                                  validate integrity check

   SUPPORT CALLS

   GSS_Display_status           translate status codes to printable
                                  form
   GSS_Indicate_mechs           indicate mech_types supported on
                                  local system
   GSS_Compare_name             compare two names for equality
   GSS_Display_name             translate name to printable form
   GSS_Import_name              convert printable name to
                                  normalized form
   GSS_Release_name             free storage of normalized-form
                                  name
   GSS_Release_buffer           free storage of general GSS-allocated
                                  object
   GSS_Release_OID_set          free storage of OID set object
   GSS_Create_empty_OID_set     create empty OID set
   GSS_Add_OID_set_member       add member to OID set
   GSS_Test_OID_set_member      test if OID is member of OID set
   GSS_Inquire_names_for_mech   indicate name types supported by



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                                  mechanism
   GSS_Inquire_mechs_for_name   indicates mechanisms supporting name
                                  type
   GSS_Canonicalize_name        translate name to per-mechanism form
   GSS_Export_name              externalize per-mechanism name
   GSS_Duplicate_name           duplicate name object

2.1:  Credential management calls

   These GSS-API calls provide functions related to the management of
   credentials. Their characterization with regard to whether or not
   they may block pending exchanges with other network entities (e.g.,
   directories or authentication servers) depends in part on OS-specific
   (extra-GSS-API) issues, so is not specified in this document.

   The GSS_Acquire_cred() call is defined within the GSS-API in support
   of application portability, with a particular orientation towards
   support of portable server applications. It is recognized that (for
   certain systems and mechanisms) credentials for interactive users may
   be managed differently from credentials for server processes; in such
   environments, it is the GSS-API implementation's responsibility to
   distinguish these cases and the procedures for making this
   distinction are a local matter. The GSS_Release_cred() call provides
   a means for callers to indicate to the GSS-API that use of a
   credentials structure is no longer required. The GSS_Inquire_cred()
   call allows callers to determine information about a credentials
   structure.  The GSS_Add_cred() call enables callers to append
   elements to an existing credential structure, allowing iterative
   construction of a multi-mechanism credential. The
   GSS_Inquire_cred_by_mech() call enables callers to extract per-
   mechanism information describing a credentials structure.

2.1.1:  GSS_Acquire_cred call

   Inputs:

   o  desired_name INTERNAL NAME, -- NULL requests locally-determined
   -- default

   o  lifetime_req INTEGER, -- in seconds; 0 requests default

   o  desired_mechs SET OF OBJECT IDENTIFIER, -- NULL requests
   -- system-selected default

   o  cred_usage INTEGER -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
   -- 2=ACCEPT-ONLY





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   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  output_cred_handle CREDENTIAL HANDLE, -- if returned non-NULL,
   -- caller must release with GSS_Release_cred()

   o  actual_mechs SET OF OBJECT IDENTIFIER, -- if returned non-NULL,
   -- caller must release with GSS_Release_oid_set()

   o  lifetime_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that requested credentials were
   successfully established, for the duration indicated in lifetime_rec,
   suitable for the usage requested in cred_usage, for the set of
   mech_types indicated in actual_mechs, and that those credentials can
   be referenced for subsequent use with the handle returned in
   output_cred_handle.

   o  GSS_S_BAD_MECH indicates that a mech_type unsupported by the GSS-
   API implementation type was requested, causing the credential
   establishment operation to fail.

   o  GSS_S_BAD_NAMETYPE indicates that the provided desired_name is
   uninterpretable or of a type unsupported by the applicable underlying
   GSS-API mechanism(s), so no credentials could be established for the
   accompanying desired_name.

   o  GSS_S_BAD_NAME indicates that the provided desired_name is
   inconsistent in terms of internally-incorporated type specifier
   information, so no credentials could be established for the
   accompanying desired_name.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that underlying credential
   elements corresponding to the requested desired_name have expired, so
   requested credentials could not be established.

   o GSS_S_NO_CRED indicates that no credential elements corresponding
   to the requested desired_name and usage could be accessed, so
   requested credentials could not be established.  In particular, this
   status should be returned upon temporary user-fixable conditions





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   preventing successful credential establishment and upon lack of
   authorization to establish and use credentials associated with the
   identity named in the input desired_name argument.

   o  GSS_S_FAILURE indicates that credential establishment failed for
   reasons unspecified at the GSS-API level.

   GSS_Acquire_cred() is used to acquire credentials so that a principal
   can (as a function of the input cred_usage parameter) initiate and/or
   accept security contexts under the identity represented by the
   desired_name input argument. On successful completion, the returned
   output_cred_handle result provides a handle for subsequent references
   to the acquired credentials.  Typically, single-user client processes
   requesting that default credential behavior be applied for context
   establishment purposes will have no need to invoke this call.

   A caller may provide the value NULL (GSS_C_NO_NAME) for desired_name,
   which will be interpreted as a request for a credential handle that
   will invoke default behavior when passed to GSS_Init_sec_context(),
   if cred_usage is GSS_C_INITIATE or GSS_C_BOTH, or
   GSS_Accept_sec_context(), if cred_usage is GSS_C_ACCEPT or
   GSS_C_BOTH.  It is possible that multiple pre-established credentials
   may exist for the same principal identity (for example, as a result
   of multiple user login sessions) when GSS_Acquire_cred() is called;
   the means used in such cases to select a specific credential are
   local matters.  The input lifetime_req argument to GSS_Acquire_cred()
   may provide useful information for local GSS-API implementations to
   employ in making this disambiguation in a manner which will best
   satisfy a caller's intent.

   This routine is expected to be used primarily by context acceptors,
   since implementations are likely to provide mechanism-specific ways
   of obtaining GSS-API initiator credentials from the system login
   process.  Some implementations may therefore not support the
   acquisition of GSS_C_INITIATE or GSS_C_BOTH credentials via
   GSS_Acquire_cred() for any name other than GSS_C_NO_NAME, or a name
   resulting from applying GSS_Inquire_context() to an active context,
   or a name resulting from applying GSS_Inquire_cred() against a
   credential handle corresponding to default behavior. It is important
   to recognize that the explicit name which is yielded by resolving a
   default reference may change over time, e.g., as a result of local
   credential element management operations outside GSS-API; once
   resolved, however, the value of such an explicit name will remain
   constant.

   The lifetime_rec result indicates the length of time for which the
   acquired credentials will be valid, as an offset from the present. A
   mechanism may return a reserved value indicating INDEFINITE if no



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   constraints on credential lifetime are imposed.  A caller of
   GSS_Acquire_cred() can request a length of time for which acquired
   credentials are to be valid (lifetime_req argument), beginning at the
   present, or can request credentials with a default validity interval.
   (Requests for postdated credentials are not supported within the
   GSS-API.) Certain mechanisms and implementations may bind in
   credential validity period specifiers at a point preliminary to
   invocation of the GSS_Acquire_cred() call (e.g., in conjunction with
   user login procedures). As a result, callers requesting non-default
   values for lifetime_req must recognize that such requests cannot
   always be honored and must be prepared to accommodate the use of
   returned credentials with different lifetimes as indicated in
   lifetime_rec.

   The caller of GSS_Acquire_cred() can explicitly specify a set of
   mech_types which are to be accommodated in the returned credentials
   (desired_mechs argument), or can request credentials for a system-
   defined default set of mech_types. Selection of the system-specified
   default set is recommended in the interests of application
   portability. The actual_mechs return value may be interrogated by the
   caller to determine the set of mechanisms with which the returned
   credentials may be used.

2.1.2:  GSS_Release_cred call

   Input:

   o  cred_handle CREDENTIAL HANDLE -- if GSS_C_NO_CREDENTIAL
   -- is specified, the call will complete successfully, but
   -- will have no effect; no credential elements will be
   -- released.

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the credentials referenced by the
   input cred_handle were released for purposes of subsequent access by
   the caller. The effect on other processes which may be authorized
   shared access to such credentials is a local matter.







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   o  GSS_S_NO_CRED indicates that no release operation was performed,
   either because the input cred_handle was invalid or because the
   caller lacks authorization to access the referenced credentials.

   o  GSS_S_FAILURE indicates that the release operation failed for
   reasons unspecified at the GSS-API level.

   Provides a means for a caller to explicitly request that credentials
   be released when their use is no longer required. Note that system-
   specific credential management functions are also likely to exist,
   for example to assure that credentials shared among processes are
   properly deleted when all affected processes terminate, even if no
   explicit release requests are issued by those processes. Given the
   fact that multiple callers are not precluded from gaining authorized
   access to the same credentials, invocation of GSS_Release_cred()
   cannot be assumed to delete a particular set of credentials on a
   system-wide basis.

2.1.3:  GSS_Inquire_cred call

   Input:

   o  cred_handle CREDENTIAL HANDLE -- if GSS_C_NO_CREDENTIAL
   -- is specified, default initiator credentials are queried

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  cred_name INTERNAL NAME,  -- caller must release with
   -- GSS_Release_name()

   o  lifetime_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   o  cred_usage INTEGER, -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
   -- 2=ACCEPT-ONLY

   o  mech_set SET OF OBJECT IDENTIFIER  -- caller must release
   -- with GSS_Release_oid_set()









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   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the credentials referenced by the
   input cred_handle argument were valid, and that the output cred_name,
   lifetime_rec, and cred_usage values represent, respectively, the
   credentials' associated principal name, remaining lifetime, suitable
   usage modes, and supported mechanism types.

   o  GSS_S_NO_CRED indicates that no information could be returned
   about the referenced credentials, either because the input
   cred_handle was invalid or because the caller lacks authorization to
   access the referenced credentials.

   o  GSS_S_DEFECTIVE_CREDENTIAL indicates that the referenced
   credentials are invalid.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that the referenced
   credentials have expired.

   o  GSS_S_FAILURE indicates that the operation failed for reasons
   unspecified at the GSS-API level.

   The GSS_Inquire_cred() call is defined primarily for the use of those
   callers which request use of default credential behavior rather than
   acquiring credentials explicitly with GSS_Acquire_cred().  It enables
   callers to determine a credential structure's associated principal
   name, remaining validity period, usability for security context
   initiation and/or acceptance, and supported mechanisms.

   For a multi-mechanism credential, the returned "lifetime" specifier
   indicates the shortest lifetime of any of the mechanisms' elements in
   the credential (for either context initiation or acceptance
   purposes).

   GSS_Inquire_cred() should indicate INITIATE-AND-ACCEPT for
   "cred_usage" if both of the following conditions hold:

      (1) there exists in the credential an element which allows context
      initiation using some mechanism

      (2) there exists in the credential an element which allows context
      acceptance using some mechanism (allowably, but not necessarily,
      one of the same mechanism(s) qualifying for (1)).

   If condition (1) holds but not condition (2), GSS_Inquire_cred()
   should indicate INITIATE-ONLY for "cred_usage".  If condition (2)
   holds but not condition (1), GSS_Inquire_cred() should indicate
   ACCEPT-ONLY for "cred_usage".



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   Callers requiring finer disambiguation among available combinations
   of lifetimes, usage modes, and mechanisms should call the
   GSS_Inquire_cred_by_mech() routine, passing that routine one of the
   mech OIDs returned by GSS_Inquire_cred().

2.1.4:  GSS_Add_cred call

   Inputs:

   o  input_cred_handle CREDENTIAL HANDLE -- handle to credential
   -- structure created with prior GSS_Acquire_cred() or
   -- GSS_Add_cred() call; see text for definition of behavior
   -- when GSS_C_NO_CREDENTIAL provided.

   o  desired_name INTERNAL NAME

   o  initiator_time_req INTEGER -- in seconds; 0 requests default

   o  acceptor_time_req INTEGER -- in seconds; 0 requests default

   o  desired_mech OBJECT IDENTIFIER

   o  cred_usage INTEGER -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
   -- 2=ACCEPT-ONLY

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  output_cred_handle CREDENTIAL HANDLE, -- NULL to request that
   -- credential elements be added "in place" to the credential
   -- structure identified by input_cred_handle,
   -- non-NULL pointer to request that
   -- a new credential structure and handle be created.
   -- if credential handle returned, caller must release with
   -- GSS_Release_cred()

   o  actual_mechs SET OF OBJECT IDENTIFIER, -- if returned, caller must
   -- release with GSS_Release_oid_set()

   o  initiator_time_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   o  acceptor_time_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE




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   o  cred_usage INTEGER, -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
   -- 2=ACCEPT-ONLY

   o  mech_set SET OF OBJECT IDENTIFIER -- full set of mechanisms
   -- supported by resulting credential.

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the credentials referenced by the
   input_cred_handle argument were valid, and that the resulting
   credential from GSS_Add_cred() is valid for the durations indicated
   in initiator_time_rec and acceptor_time_rec, suitable for the usage
   requested in cred_usage, and for the mechanisms indicated in
   actual_mechs.

   o  GSS_S_DUPLICATE_ELEMENT indicates that the input desired_mech
   specified a mechanism for which the referenced credential already
   contained a credential element with overlapping cred_usage and
   validity time specifiers.

   o  GSS_S_BAD_MECH indicates that the input desired_mech specified a
   mechanism unsupported by the GSS-API implementation, causing the
   GSS_Add_cred() operation to fail.

   o  GSS_S_BAD_NAMETYPE indicates that the provided desired_name is
   uninterpretable or of a type unsupported by the applicable underlying
   GSS-API mechanism(s), so the GSS_Add_cred() operation could not be
   performed for that name.

   o  GSS_S_BAD_NAME indicates that the provided desired_name is
   inconsistent in terms of internally-incorporated type specifier
   information, so the GSS_Add_cred() operation could not be performed
   for that name.

   o  GSS_S_NO_CRED indicates that the input_cred_handle referenced
   invalid or inaccessible credentials. In particular, this status
   should be returned upon temporary user-fixable conditions preventing
   successful credential establishment or upon lack of authorization to
   establish or use credentials representing the requested identity.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that referenced credential
   elements have expired, so the GSS_Add_cred() operation could not be
   performed.

   o  GSS_S_FAILURE indicates that the operation failed for reasons
   unspecified at the GSS-API level.





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   GSS_Add_cred() enables callers to construct credentials iteratively
   by adding credential elements in successive operations, corresponding
   to different mechanisms.  This offers particular value in multi-
   mechanism environments, as the major_status and minor_status values
   returned on each iteration are individually visible and can therefore
   be interpreted unambiguously on a per-mechanism basis. A credential
   element is identified by the name of the principal to which it
   refers.  GSS-API implementations must impose a local access control
   policy on callers of this routine to prevent unauthorized callers
   from acquiring credential elements to which they are not entitled.
   This routine is not intended to provide a "login to the network"
   function, as such a function would involve the creation of new
   mechanism-specific authentication data, rather than merely acquiring
   a GSS-API handle to existing data.  Such functions, if required,
   should be defined in implementation-specific extension routines.

   If credential acquisition is time-consuming for a mechanism, the
   mechanism may choose to delay the actual acquisition until the
   credential is required (e.g. by GSS_Init_sec_context() or
   GSS_Accept_sec_context()).  Such mechanism-specific implementation
   decisions should be invisible to the calling application; thus a call
   of GSS_Inquire_cred() immediately following the call of
   GSS_Acquire_cred() must return valid credential data, and may
   therefore incur the overhead of a deferred credential acquisition.

   If GSS_C_NO_CREDENTIAL is specified as input_cred_handle, a non-NULL
   output_cred_handle must be supplied.  For the case of
   GSS_C_NO_CREDENTIAL as input_cred_handle, GSS_Add_cred() will create
   the credential referenced by its output_cred_handle based on default
   behavior.  That is, the call will have the same effect as if the
   caller had previously called GSS_Acquire_cred(), specifying the same
   usage and passing GSS_C_NO_NAME as the desired_name parameter
   (thereby obtaining an explicit credential handle corresponding to
   default behavior), had passed that credential handle to
   GSS_Add_cred(), and had finally called GSS_Release_cred() on the
   credential handle received from GSS_Acquire_cred().

   This routine is expected to be used primarily by context acceptors,
   since implementations are likely to provide mechanism-specific ways
   of obtaining GSS-API initiator credentials from the system login
   process.  Some implementations may therefore not support the
   acquisition of GSS_C_INITIATE or GSS_C_BOTH credentials via
   GSS_Acquire_cred() for any name other than GSS_C_NO_NAME, or a name
   resulting from applying GSS_Inquire_context() to an active context,
   or a name resulting from applying GSS_Inquire_cred() against a
   credential handle corresponding to default behavior. It is important
   to recognize that the explicit name which is yielded by resolving a
   default reference may change over time, e.g., as a result of local



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   credential element management operations outside GSS-API; once
   resolved, however, the value of such an explicit name will remain
   constant.

   A caller may provide the value NULL (GSS_C_NO_NAME) for desired_name,
   which will be interpreted as a request for a credential handle that
   will invoke default behavior when passed to GSS_Init_sec_context(),
   if cred_usage is GSS_C_INITIATE or GSS_C_BOTH, or
   GSS_Accept_sec_context(), if cred_usage is GSS_C_ACCEPT or
   GSS_C_BOTH.

   The same input desired_name, or default reference, should be used on
   all GSS_Acquire_cred() and GSS_Add_cred() calls corresponding to a
   particular credential.

2.1.5:  GSS_Inquire_cred_by_mech call

   Inputs:

   o  cred_handle CREDENTIAL HANDLE -- if GSS_C_NO_CREDENTIAL
   -- specified, default initiator credentials are queried

   o  mech_type OBJECT IDENTIFIER  -- specific mechanism for
   -- which credentials are being queried

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  cred_name INTERNAL NAME, -- guaranteed to be MN; caller must
   -- release with GSS_Release_name()

   o  lifetime_rec_initiate INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   o  lifetime_rec_accept INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   o  cred_usage INTEGER, -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
   -- 2=ACCEPT-ONLY

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the credentials referenced by the
   input cred_handle argument were valid, that the mechanism indicated
   by the input mech_type was represented with elements within those



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   credentials, and that the output cred_name, lifetime_rec_initiate,
   lifetime_rec_accept, and cred_usage values represent, respectively,
   the credentials' associated principal name, remaining lifetimes, and
   suitable usage modes.

   o  GSS_S_NO_CRED indicates that no information could be returned
   about the referenced credentials, either because the input
   cred_handle was invalid or because the caller lacks authorization to
   access the referenced credentials.

   o  GSS_S_DEFECTIVE_CREDENTIAL indicates that the referenced
   credentials are invalid.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that the referenced
   credentials have expired.

   o  GSS_S_BAD_MECH indicates that the referenced credentials do not
   contain elements for the requested mechanism.

   o  GSS_S_FAILURE indicates that the operation failed for reasons
   unspecified at the GSS-API level.

   The GSS_Inquire_cred_by_mech() call enables callers in multi-
   mechanism environments to acquire specific data about available
   combinations of lifetimes, usage modes, and mechanisms within a
   credential structure.  The lifetime_rec_initiate result indicates the
   available lifetime for context initiation purposes; the
   lifetime_rec_accept result indicates the available lifetime for
   context acceptance purposes.

2.2:  Context-level calls

   This group of calls is devoted to the establishment and management of
   security contexts between peers. A context's initiator calls
   GSS_Init_sec_context(), resulting in generation of a token which the
   caller passes to the target. At the target, that token is passed to
   GSS_Accept_sec_context(). Depending on the underlying mech_type and
   specified options, additional token exchanges may be performed in the
   course of context establishment; such exchanges are accommodated by
   GSS_S_CONTINUE_NEEDED status returns from GSS_Init_sec_context() and
   GSS_Accept_sec_context().

   Either party to an established context may invoke
   GSS_Delete_sec_context() to flush context information when a context
   is no longer required. GSS_Process_context_token() is used to process
   received tokens carrying context-level control information.
   GSS_Context_time() allows a caller to determine the length of time
   for which an established context will remain valid.



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   GSS_Inquire_context() returns status information describing context
   characteristics. GSS_Wrap_size_limit() allows a caller to determine
   the size of a token which will be generated by a GSS_Wrap()
   operation.  GSS_Export_sec_context() and GSS_Import_sec_context()
   enable transfer of active contexts between processes on an end
   system.

2.2.1:  GSS_Init_sec_context call

   Inputs:

   o  claimant_cred_handle CREDENTIAL HANDLE, -- NULL specifies "use
   -- default"

   o  input_context_handle CONTEXT HANDLE, -- 0
   -- (GSS_C_NO_CONTEXT) specifies "none assigned yet"

   o  targ_name INTERNAL NAME,

   o  mech_type OBJECT IDENTIFIER, -- NULL parameter specifies "use
   -- default"

   o  deleg_req_flag BOOLEAN,

   o  mutual_req_flag BOOLEAN,

   o  replay_det_req_flag BOOLEAN,

   o  sequence_req_flag BOOLEAN,

   o  anon_req_flag BOOLEAN,

   o  conf_req_flag BOOLEAN,

   o  integ_req_flag BOOLEAN,

   o  lifetime_req INTEGER, -- 0 specifies default lifetime

   o  chan_bindings OCTET STRING,

   o  input_token OCTET STRING -- NULL or token received from target

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,




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   o  output_context_handle CONTEXT HANDLE,  -- once returned non-NULL,
   -- caller must release with GSS_Delete_sec_context()

   o  mech_type OBJECT IDENTIFIER, -- actual mechanism always
   -- indicated, never NULL; caller should treat as read-only
   -- and should not attempt to release

   o  output_token OCTET STRING, -- NULL or token to pass to context
   -- target; caller must release with GSS_Release_buffer()

   o  deleg_state BOOLEAN,

   o  mutual_state BOOLEAN,

   o  replay_det_state BOOLEAN,

   o  sequence_state BOOLEAN,

   o  anon_state BOOLEAN,

   o  trans_state BOOLEAN,

   o  prot_ready_state BOOLEAN, -- see Section 1.2.7

   o  conf_avail BOOLEAN,

   o  integ_avail BOOLEAN,

   o  lifetime_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   This call may block pending network interactions for those mech_types
   in which an authentication server or other network entity must be
   consulted on behalf of a context initiator in order to generate an
   output_token suitable for presentation to a specified target.

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that context-level information was
   successfully initialized, and that the returned output_token will
   provide sufficient information for the target to perform per-message
   processing on the newly-established context.

   o  GSS_S_CONTINUE_NEEDED indicates that control information in the
   returned output_token must be sent to the target, and that a reply
   must be received and passed as the input_token argument





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   to a continuation call to GSS_Init_sec_context(), before per-message
   processing can be performed in conjunction with this context (unless
   the prot_ready_state value is concurrently returned TRUE).

   o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
   on the input_token failed, preventing further processing from being
   performed based on that token.

   o  GSS_S_DEFECTIVE_CREDENTIAL indicates that consistency checks
   performed on the credential structure referenced by
   claimant_cred_handle failed, preventing further processing from being
   performed using that credential structure.

   o  GSS_S_BAD_SIG (GSS_S_BAD_MIC) indicates that the received
   input_token contains an incorrect integrity check, so context setup
   cannot be accomplished.

   o  GSS_S_NO_CRED indicates that no context was established, either
   because the input cred_handle was invalid, because the referenced
   credentials are valid for context acceptor use only, because the
   caller lacks authorization to access the referenced credentials, or
   because the resolution of default credentials failed.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that the credentials provided
   through the input claimant_cred_handle argument are no longer valid,
   so context establishment cannot be completed.

   o  GSS_S_BAD_BINDINGS indicates that a mismatch between the caller-
   provided chan_bindings and those extracted from the input_token was
   detected, signifying a security-relevant event and preventing context
   establishment. (This result will be returned by
   GSS_Init_sec_context() only for contexts where mutual_state is TRUE.)

   o  GSS_S_OLD_TOKEN indicates that the input_token is too old to be
   checked for integrity. This is a fatal error during context
   establishment.

   o  GSS_S_DUPLICATE_TOKEN indicates that the input token has a correct
   integrity check, but is a duplicate of a token already processed.
   This is a fatal error during context establishment.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided; this major status will be
   returned only for successor calls following GSS_S_CONTINUE_ NEEDED
   status returns.






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   o  GSS_S_BAD_NAMETYPE indicates that the provided targ_name is of a
   type uninterpretable or unsupported by the applicable underlying
   GSS-API mechanism(s), so context establishment cannot be completed.

   o  GSS_S_BAD_NAME indicates that the provided targ_name is
   inconsistent in terms of internally-incorporated type specifier
   information, so context establishment cannot be accomplished.

   o  GSS_S_BAD_MECH indicates receipt of a context establishment token
   or of a caller request specifying a mechanism unsupported by the
   local system or with the caller's active credentials

   o  GSS_S_FAILURE indicates that context setup could not be
   accomplished for reasons unspecified at the GSS-API level, and that
   no interface-defined recovery action is available.

   This routine is used by a context initiator, and ordinarily emits an
   output_token suitable for use by the target within the selected
   mech_type's protocol.  For the case of a multi-step exchange, this
   output_token will be one in a series, each generated by a successive
   call. Using information in the credentials structure referenced by
   claimant_cred_handle, GSS_Init_sec_context() initializes the data
   structures required to establish a security context with target
   targ_name.

   The targ_name may be any valid INTERNAL NAME; it need not be an MN.
   In addition to support for other name types, it is recommended (newly
   as of GSS-V2, Update 1) that mechanisms be able to accept
   GSS_C_NO_NAME as an input type for targ_name.  While recommended,
   such support is not required, and it is recognized that not all
   mechanisms can construct tokens without explicitly naming the context
   target, even when mutual authentication of the target is not
   obtained.  Callers wishing to make use of this facility and concerned
   with portability should be aware that support for GSS_C_NO_NAME as
   input targ_name type is unlikely to be provided within mechanism
   definitions specified prior to GSS-V2, Update 1.

   The claimant_cred_handle must correspond to the same valid
   credentials structure on the initial call to GSS_Init_sec_context()
   and on any successor calls resulting from GSS_S_CONTINUE_NEEDED
   status returns; different protocol sequences modeled by the
   GSS_S_CONTINUE_NEEDED facility will require access to credentials at
   different points in the context establishment sequence.

   The caller-provided input_context_handle argument is to be 0
   (GSS_C_NO_CONTEXT), specifying "not yet assigned", on the first
   GSS_Init_sec_context()  call relating to a given context. If
   successful (i.e., if accompanied by major_status GSS_S_COMPLETE or



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   GSS_S_CONTINUE_NEEDED), and only if successful, the initial
   GSS_Init_sec_context() call returns a non-zero output_context_handle
   for use in future references to this context.  Once a non-zero
   output_context_handle has been returned, GSS-API callers should call
   GSS_Delete_sec_context() to release context-related resources if
   errors occur in later phases of context establishment, or when an
   established context is no longer required. If GSS_Init_sec_context()
   is passed the handle of a context which is already fully established,
   GSS_S_FAILURE status is returned.

   When continuation attempts to GSS_Init_sec_context() are needed to
   perform context establishment, the previously-returned non-zero
   handle value is entered into the input_context_handle argument and
   will be echoed in the returned output_context_handle argument. On
   such continuation attempts (and only on continuation attempts) the
   input_token value is used, to provide the token returned from the
   context's target.

   The chan_bindings argument is used by the caller to provide
   information binding the security context to security-related
   characteristics (e.g., addresses, cryptographic keys) of the
   underlying communications channel. See Section 1.1.6 of this document
   for more discussion of this argument's usage.

   The input_token argument contains a message received from the target,
   and is significant only on a call to GSS_Init_sec_context() which
   follows a previous return indicating GSS_S_CONTINUE_NEEDED
   major_status.

   It is the caller's responsibility to establish a communications path
   to the target, and to transmit any returned output_token (independent
   of the accompanying returned major_status value) to the target over
   that path. The output_token can, however, be transmitted along with
   the first application-provided input message to be processed by
   GSS_GetMIC() or GSS_Wrap() in conjunction with a successfully-
   established context. (Note: when the GSS-V2 prot_ready_state
   indicator is returned TRUE, it can be possible to transfer a
   protected message before context establishment is complete:  see also
   Section 1.2.7)

   The initiator may request various context-level functions through
   input flags: the deleg_req_flag requests delegation of access rights,
   the mutual_req_flag requests mutual authentication, the
   replay_det_req_flag requests that replay detection features be
   applied to messages transferred on the established context, and the
   sequence_req_flag requests that sequencing be enforced. (See Section





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   1.2.3 for more information on replay detection and sequencing
   features.)  The anon_req_flag requests that the initiator's identity
   not be transferred within tokens to be sent to the acceptor.

   The conf_req_flag and integ_req_flag provide informatory inputs to
   the GSS-API implementation as to whether, respectively, per-message
   confidentiality and per-message integrity services will be required
   on the context.  This information is important as an input to
   negotiating mechanisms.  It is important to recognize, however, that
   the inclusion of these flags (which are newly defined for GSS-V2)
   introduces a backward incompatibility with callers implemented to
   GSS-V1, where the flags were not defined.  Since no GSS-V1 callers
   would set these flags, even if per-message services are desired,
   GSS-V2 mechanism implementations which enable such services
   selectively based on the flags' values may fail to provide them to
   contexts established for GSS-V1 callers.  It may be appropriate under
   certain circumstances, therefore, for such mechanism implementations
   to infer these service request flags to be set if a caller is known
   to be implemented to GSS-V1.

   Not all of the optionally-requestable features will be available in
   all underlying mech_types. The corresponding return state values
   deleg_state, mutual_state, replay_det_state, and sequence_state
   indicate, as a function of mech_type processing capabilities and
   initiator-provided input flags, the set of features which will be
   active on the context.  The returned trans_state value indicates
   whether the context is transferable to other processes through use of
   GSS_Export_sec_context().  These state indicators' values are
   undefined unless either the routine's major_status indicates
   GSS_S_COMPLETE, or TRUE prot_ready_state is returned along with
   GSS_S_CONTINUE_NEEDED major_status; for the latter case, it is
   possible that additional features, not confirmed or indicated along
   with TRUE prot_ready_state, will be confirmed and indicated when
   GSS_S_COMPLETE is subsequently returned.

   The returned anon_state and prot_ready_state values are significant
   for both GSS_S_COMPLETE and GSS_S_CONTINUE_NEEDED major_status
   returns from GSS_Init_sec_context(). When anon_state is returned
   TRUE, this indicates that neither the current token nor its
   predecessors delivers or has delivered the initiator's identity.
   Callers wishing to perform context establishment only if anonymity
   support is provided should transfer a returned token from
   GSS_Init_sec_context() to the peer only if it is accompanied by a
   TRUE anon_state indicator.  When prot_ready_state is returned TRUE in
   conjunction with GSS_S_CONTINUE_NEEDED major_status, this indicates
   that per-message protection operations may be applied on the context:
   see Section 1.2.7 for further discussion of this facility.




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   Failure to provide the precise set of features requested by the
   caller does not cause context establishment to fail; it is the
   caller's prerogative to delete the context if the feature set
   provided is unsuitable for the caller's use.

   The returned mech_type value indicates the specific mechanism
   employed on the context; it will never indicate the value for
   "default".  A valid mech_type result must be returned along with a
   GSS_S_COMPLETE status return; GSS-API implementations may (but are
   not required to) also return mech_type along with predecessor calls
   indicating GSS_S_CONTINUE_NEEDED status or (if a mechanism is
   determinable) in conjunction with fatal error cases.  For the case of
   mechanisms which themselves perform negotiation, the returned
   mech_type result may indicate selection of a mechanism identified by
   an OID different than that passed in the input mech_type argument,
   and the returned value may change between successive calls returning
   GSS_S_CONTINUE_NEEDED and the final call returning GSS_S_COMPLETE.

   The conf_avail return value indicates whether the context supports
   per-message confidentiality services, and so informs the caller
   whether or not a request for encryption through the conf_req_flag
   input to GSS_Wrap() can be honored. In similar fashion, the
   integ_avail return value indicates whether per-message integrity
   services are available (through either GSS_GetMIC() or GSS_Wrap()) on
   the established context. These state indicators' values are undefined
   unless either the routine's major_status indicates GSS_S_COMPLETE, or
   TRUE prot_ready_state is returned along with GSS_S_CONTINUE_NEEDED
   major_status.

   The lifetime_req input specifies a desired upper bound for the
   lifetime of the context to be established, with a value of 0 used to
   request a default lifetime. The lifetime_rec return value indicates
   the length of time for which the context will be valid, expressed as
   an offset from the present; depending on mechanism capabilities,
   credential lifetimes, and local policy, it may not correspond to the
   value requested in lifetime_req.  If no constraints on context
   lifetime are imposed, this may be indicated by returning a reserved
   value representing INDEFINITE lifetime_req. The value of lifetime_rec
   is undefined unless the routine's major_status indicates
   GSS_S_COMPLETE.

   If the mutual_state is TRUE, this fact will be reflected within the
   output_token. A call to GSS_Accept_sec_context() at the target in
   conjunction with such a context will return a token, to be processed
   by a continuation call to GSS_Init_sec_context(), in order to achieve
   mutual authentication.





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2.2.2:  GSS_Accept_sec_context call

   Inputs:

   o  acceptor_cred_handle CREDENTIAL HANDLE, -- NULL specifies
   -- "use default"

   o  input_context_handle CONTEXT HANDLE, -- 0
   -- (GSS_C_NO_CONTEXT) specifies "not yet assigned"

   o  chan_bindings OCTET STRING,

   o  input_token OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  src_name INTERNAL NAME, -- guaranteed to be MN
   -- once returned, caller must release with GSS_Release_name()

   o  mech_type OBJECT IDENTIFIER, -- caller should treat as
   -- read-only; does not need to be released

   o  output_context_handle CONTEXT HANDLE, -- once returned
   -- non-NULL in context establishment sequence, caller
   -- must release with GSS_Delete_sec_context()

   o  deleg_state BOOLEAN,

   o  mutual_state BOOLEAN,

   o  replay_det_state BOOLEAN,

   o  sequence_state BOOLEAN,

   o  anon_state BOOLEAN,

   o  trans_state BOOLEAN,

   o  prot_ready_state BOOLEAN, -- see Section 1.2.7 for discussion

   o  conf_avail BOOLEAN,

   o  integ_avail BOOLEAN,




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   o  lifetime_rec INTEGER, -- in seconds, or reserved value for
   -- INDEFINITE

   o  delegated_cred_handle CREDENTIAL HANDLE, -- if returned non-NULL,
   -- caller must release with GSS_Release_cred()

   o  output_token OCTET STRING -- NULL or token to pass to context
   -- initiator; if returned non-NULL, caller must release with
   -- GSS_Release_buffer()

   This call may block pending network interactions for those mech_types
   in which a directory service or other network entity must be
   consulted on behalf of a context acceptor in order to validate a
   received input_token.

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that context-level data structures were
   successfully initialized, and that per-message processing can now be
   performed in conjunction with this context.

   o  GSS_S_CONTINUE_NEEDED indicates that control information in the
   returned output_token must be sent to the initiator, and that a
   response must be received and passed as the input_token argument to a
   continuation call to GSS_Accept_sec_context(), before per-message
   processing can be performed in conjunction with this context.

   o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
   on the input_token failed, preventing further processing from being
   performed based on that token.

   o  GSS_S_DEFECTIVE_CREDENTIAL indicates that consistency checks
   performed on the credential structure referenced by
   acceptor_cred_handle failed, preventing further processing from being
   performed using that credential structure.

   o  GSS_S_BAD_SIG (GSS_S_BAD_MIC) indicates that the received
   input_token contains an incorrect integrity check, so context setup
   cannot be accomplished.

   o  GSS_S_DUPLICATE_TOKEN indicates that the integrity check on the
   received input_token was correct, but that the input_token was
   recognized as a duplicate of an input_token already processed. No new
   context is established.







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   o  GSS_S_OLD_TOKEN indicates that the integrity check on the received
   input_token was correct, but that the input_token is too old to be
   checked for duplication against previously-processed input_tokens. No
   new context is established.

   o  GSS_S_NO_CRED indicates that no context was established, either
   because the input cred_handle was invalid, because the referenced
   credentials are valid for context initiator use only, because the
   caller lacks authorization to access the referenced credentials, or
   because the procedure for default credential resolution failed.

   o  GSS_S_CREDENTIALS_EXPIRED indicates that the credentials provided
   through the input acceptor_cred_handle argument are no longer valid,
   so context establishment cannot be completed.

   o  GSS_S_BAD_BINDINGS indicates that a mismatch between the caller-
   provided chan_bindings and those extracted from the input_token was
   detected, signifying a security-relevant event and preventing context
   establishment.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided; this major status will be
   returned only for successor calls following GSS_S_CONTINUE_ NEEDED
   status returns.

   o  GSS_S_BAD_MECH indicates receipt of a context establishment token
   specifying a mechanism unsupported by the local system or with the
   caller's active credentials.

   o  GSS_S_FAILURE indicates that context setup could not be
   accomplished for reasons unspecified at the GSS-API level, and that
   no interface-defined recovery action is available.

   The GSS_Accept_sec_context() routine is used by a context target.
   Using information in the credentials structure referenced by the
   input acceptor_cred_handle, it verifies the incoming input_token and
   (following the successful completion of a context establishment
   sequence) returns the authenticated src_name and the mech_type used.
   The returned src_name is guaranteed to be an MN, processed by the
   mechanism under which the context was established. The
   acceptor_cred_handle must correspond to the same valid credentials
   structure on the initial call to GSS_Accept_sec_context() and on any
   successor calls resulting from GSS_S_CONTINUE_NEEDED status returns;
   different protocol sequences modeled by the GSS_S_CONTINUE_NEEDED
   mechanism will require access to credentials at different points in
   the context establishment sequence.





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   The caller-provided input_context_handle argument is to be 0
   (GSS_C_NO_CONTEXT), specifying "not yet assigned", on the first
   GSS_Accept_sec_context() call relating to a given context. If
   successful (i.e., if accompanied by major_status GSS_S_COMPLETE or
   GSS_S_CONTINUE_NEEDED), and only if successful, the initial
   GSS_Accept_sec_context() call returns a non-zero
   output_context_handle for use in future references to this context.
   Once a non-zero output_context_handle has been returned, GSS-API
   callers should call GSS_Delete_sec_context() to release context-
   related resources if errors occur in later phases of context
   establishment, or when an established context is no longer required.
   If GSS_Accept_sec_context() is passed the handle of a context which
   is already fully established, GSS_S_FAILURE status is returned.

   The chan_bindings argument is used by the caller to provide
   information binding the security context to security-related
   characteristics (e.g., addresses, cryptographic keys) of the
   underlying communications channel. See Section 1.1.6 of this document
   for more discussion of this argument's usage.

   The returned state results (deleg_state, mutual_state,
   replay_det_state, sequence_state, anon_state, trans_state, and
   prot_ready_state) reflect the same information as described for
   GSS_Init_sec_context(), and their values are significant under the
   same return state conditions.

   The conf_avail return value indicates whether the context supports
   per-message confidentiality services, and so informs the caller
   whether or not a request for encryption through the conf_req_flag
   input to GSS_Wrap() can be honored. In similar fashion, the
   integ_avail return value indicates whether per-message integrity
   services are available (through either GSS_GetMIC()  or GSS_Wrap())
   on the established context.  These values are significant under the
   same return state conditions as described under
   GSS_Init_sec_context().

   The lifetime_rec return value is significant only in conjunction with
   GSS_S_COMPLETE major_status, and indicates the length of time for
   which the context will be valid, expressed as an offset from the
   present.

   The returned mech_type value indicates the specific mechanism
   employed on the context; it will never indicate the value for
   "default".  A valid mech_type result must be returned whenever
   GSS_S_COMPLETE status is indicated; GSS-API implementations may (but
   are not required to) also return mech_type along with predecessor
   calls indicating GSS_S_CONTINUE_NEEDED status or (if a mechanism is
   determinable) in conjunction with fatal error cases.  For the case of



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   mechanisms which themselves perform negotiation, the returned
   mech_type result may indicate selection of a mechanism identified by
   an OID different than that passed in the input mech_type argument,
   and the returned value may change between successive calls returning
   GSS_S_CONTINUE_NEEDED and the final call returning GSS_S_COMPLETE.

   The delegated_cred_handle result is significant only when deleg_state
   is TRUE, and provides a means for the target to reference the
   delegated credentials. The output_token result, when non-NULL,
   provides a context-level token to be returned to the context
   initiator to continue a multi-step context establishment sequence. As
   noted with GSS_Init_sec_context(), any returned token should be
   transferred to the context's peer (in this case, the context
   initiator), independent of the value of the accompanying returned
   major_status.

   Note: A target must be able to distinguish a context-level
   input_token, which is passed to GSS_Accept_sec_context(), from the
   per-message data elements passed to GSS_VerifyMIC()  or GSS_Unwrap().
   These data elements may arrive in a single application message, and
   GSS_Accept_sec_context() must be performed before per-message
   processing can be performed successfully.

2.2.3: GSS_Delete_sec_context call

   Input:

   o  context_handle CONTEXT HANDLE

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  output_context_token OCTET STRING

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the context was recognized, and that
   relevant context-specific information was flushed.  If the caller
   provides a non-null buffer to receive an output_context_token, and
   the mechanism returns a non-NULL token into that buffer, the returned
   output_context_token is ready for transfer to the context's peer.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided, so no deletion was performed.




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   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the GSS_Delete_sec_context() operation could not be performed for
   reasons unspecified at the GSS-API level.

   This call can be made by either peer in a security context, to flush
   context-specific information. Once a non-zero output_context_handle
   has been returned by context establishment calls, GSS-API callers
   should call GSS_Delete_sec_context() to release context-related
   resources if errors occur in later phases of context establishment,
   or when an established context is no longer required.  This call may
   block pending network interactions for mech_types in which active
   notification must be made to a central server when a security context
   is to be deleted.

   If a non-null output_context_token parameter is provided by the
   caller, an output_context_token may be returned to the caller.  If an
   output_context_token is provided to the caller, it can be passed to
   the context's peer to inform the peer's GSS-API implementation that
   the peer's corresponding context information can also be flushed.
   (Once a context is established, the peers involved are expected to
   retain cached credential and context-related information until the
   information's expiration time is reached or until a
   GSS_Delete_sec_context() call is made.)

   The facility for context_token usage to signal context deletion is
   retained for compatibility with GSS-API Version 1.  For current
   usage, it is recommended that both peers to a context invoke
   GSS_Delete_sec_context() independently, passing a null
   output_context_token buffer to indicate that no context_token is
   required.  Implementations of GSS_Delete_sec_context() should delete
   relevant locally-stored context information.

   Attempts to perform per-message processing on a deleted context will
   result in error returns.

2.2.4:  GSS_Process_context_token call

   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  input_context_token OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,



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   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the input_context_token was
   successfully processed in conjunction with the context referenced by
   context_handle.

   o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
   on the received context_token failed, preventing further processing
   from being performed with that token.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided.

   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the GSS_Process_context_token() operation could not be performed for
   reasons unspecified at the GSS-API level.

   This call is used to process context_tokens received from a peer once
   a context has been established, with corresponding impact on
   context-level state information. One use for this facility is
   processing of the context_tokens generated by
   GSS_Delete_sec_context(); GSS_Process_context_token() will not block
   pending network interactions for that purpose. Another use is to
   process tokens indicating remote-peer context establishment failures
   after the point where the local GSS-API implementation has already
   indicated GSS_S_COMPLETE status.

2.2.5:  GSS_Context_time call

   Input:

   o  context_handle CONTEXT HANDLE,

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  lifetime_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the referenced context is valid, and
   will remain valid for the amount of time indicated in lifetime_rec.





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   o  GSS_S_CONTEXT_EXPIRED indicates that data items related to the
   referenced context have expired.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided.

   o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level.

   This call is used to determine the amount of time for which a
   currently established context will remain valid.

2.2.6: GSS_Inquire_context call

   Input:

   o  context_handle CONTEXT HANDLE,

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  src_name INTERNAL NAME,  -- name of context initiator,
   -- guaranteed to be MN;
   -- caller must release with GSS_Release_name() if returned

   o  targ_name INTERNAL NAME,  -- name of context target,
   -- guaranteed to be MN;
   -- caller must release with GSS_Release_name() if returned

   o  lifetime_rec INTEGER -- in seconds, or reserved value for
   -- INDEFINITE or EXPIRED

   o  mech_type OBJECT IDENTIFIER, -- the mechanism supporting this
   -- security context; caller should treat as read-only and not
   -- attempt to release

   o  deleg_state BOOLEAN,

   o  mutual_state BOOLEAN,

   o  replay_det_state BOOLEAN,

   o  sequence_state BOOLEAN,

   o  anon_state BOOLEAN,



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   o  trans_state BOOLEAN,

   o  prot_ready_state BOOLEAN,

   o  conf_avail BOOLEAN,

   o  integ_avail BOOLEAN,

   o  locally_initiated BOOLEAN, -- TRUE if initiator, FALSE if acceptor

   o  open BOOLEAN, -- TRUE if context fully established, FALSE
   -- if partly established (in CONTINUE_NEEDED state)

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the referenced context is valid and
   that deleg_state, mutual_state, replay_det_state, sequence_state,
   anon_state, trans_state, prot_ready_state, conf_avail, integ_avail,
   locally_initiated, and open return values describe the corresponding
   characteristics of the context.  If open is TRUE, lifetime_rec is
   also returned: if open is TRUE and the context peer's name is known,
   src_name and targ_name are valid in addition to the values listed
   above.  The mech_type value must be returned for contexts where open
   is TRUE and may be returned for contexts where open is FALSE.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided. Return values other than
   major_status and minor_status are undefined.

   o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level. Return values other than
   major_status and minor_status are undefined.

   This call is used to extract information describing characteristics
   of a security context.  Note that GSS-API implementations are
   expected to retain inquirable context data on a context until the
   context is released by a caller, even after the context has expired,
   although underlying cryptographic data elements may be deleted after
   expiration in order to limit their exposure.

2.2.7:   GSS_Wrap_size_limit call

   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  conf_req_flag BOOLEAN,




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   o  qop INTEGER,

   o  output_size INTEGER

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  max_input_size INTEGER

   Return major_status codes:

   o  GSS_S_COMPLETE indicates a successful token size determination:
   an input message with a length in octets equal to the returned
   max_input_size value will, when passed to GSS_Wrap() for processing
   on the context identified by the context_handle parameter with the
   confidentiality request state as provided in conf_req_flag and with
   the quality of protection specifier provided in the qop parameter,
   yield an output token no larger than the value of the provided
   output_size parameter.

   o  GSS_S_CONTEXT_EXPIRED indicates that the provided input
   context_handle is recognized, but that the referenced context has
   expired.  Return values other than major_status and minor_status are
   undefined.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided. Return values other than
   major_status and minor_status are undefined.

   o  GSS_S_BAD_QOP indicates that the provided QOP value is not
   recognized or supported for the context.

   o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level. Return values other than
   major_status and minor_status are undefined.

   This call is used to determine the largest input datum which may be
   passed to GSS_Wrap() without yielding an output token larger than a
   caller-specified value.









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2.2.8:   GSS_Export_sec_context call

   Inputs:

   o  context_handle CONTEXT HANDLE

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  interprocess_token OCTET STRING  -- caller must release
   -- with GSS_Release_buffer()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the referenced context has been
   successfully exported to a representation in the interprocess_token,
   and is no longer available for use by the caller.

   o  GSS_S_UNAVAILABLE indicates that the context export facility is
   not available for use on the referenced context.  (This status should
   occur only for contexts for which the trans_state value is FALSE.)
   Return values other than major_status and minor_status are undefined.

   o  GSS_S_CONTEXT_EXPIRED indicates that the provided input
   context_handle is recognized, but that the referenced context has
   expired.  Return values other than major_status and minor_status are
   undefined.

   o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
   for the input context_handle provided. Return values other than
   major_status and minor_status are undefined.

   o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level. Return values other than
   major_status and minor_status are undefined.

   This call generates an interprocess token for transfer to another
   process within an end system, in order to transfer control of a
   security context to that process.  The recipient of the interprocess
   token will call GSS_Import_sec_context() to accept the transfer.  The
   GSS_Export_sec_context() operation is defined for use only with
   security contexts which are fully and successfully established (i.e.,
   those for which GSS_Init_sec_context() and GSS_Accept_sec_context()
   have returned GSS_S_COMPLETE major_status).




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   A successful GSS_Export_sec_context() operation deactivates the
   security context for the calling process; for this case, the GSS-API
   implementation shall deallocate all process-wide resources associated
   with the security context and shall set the context_handle to
   GSS_C_NO_CONTEXT.  In the event of an error that makes it impossible
   to complete export of the security context, the GSS-API
   implementation must not return an interprocess token and should
   strive to leave the security context referenced by the context_handle
   untouched.  If this is impossible, it is permissible for the
   implementation to delete the security context, provided that it also
   sets the context_handle parameter to GSS_C_NO_CONTEXT.

   Portable callers must not assume that a given interprocess token can
   be imported by GSS_Import_sec_context() more than once, thereby
   creating multiple instantiations of a single context.  GSS-API
   implementations may detect and reject attempted multiple imports, but
   are not required to do so.

   The internal representation contained within the interprocess token
   is an implementation-defined local matter.  Interprocess tokens
   cannot be assumed to be transferable across different GSS-API
   implementations.

   It is recommended that GSS-API implementations adopt policies suited
   to their operational environments in order to define the set of
   processes eligible to import a context, but specific constraints in
   this area are local matters.  Candidate examples include transfers
   between processes operating on behalf of the same user identity, or
   processes comprising a common job.  However, it may be impossible to
   enforce such policies in some implementations.

   In support of the above goals, implementations may protect the
   transferred context data by using cryptography to protect data within
   the interprocess token, or by using interprocess tokens as a means to
   reference local interprocess communication facilities (protected by
   other means) rather than storing the context data directly within the
   tokens.

   Transfer of an open context may, for certain mechanisms and
   implementations, reveal data about the credential which was used to
   establish the context.  Callers should, therefore, be cautious about
   the trustworthiness of processes to which they transfer contexts.
   Although the GSS-API implementation may provide its own set of
   protections over the exported context, the caller is responsible for
   protecting the interprocess token from disclosure, and for taking
   care that the context is transferred to an appropriate destination
   process.




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2.2.9:   GSS_Import_sec_context call

   Inputs:

   o  interprocess_token OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  context_handle CONTEXT HANDLE  -- if successfully returned,
   -- caller must release with GSS_Delete_sec_context()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the context represented by the input
   interprocess_token has been successfully transferred to the caller,
   and is available for future use via the output context_handle.

   o  GSS_S_NO_CONTEXT indicates that the context represented by the
   input interprocess_token was invalid. Return values other than
   major_status and minor_status are undefined.

   o  GSS_S_DEFECTIVE_TOKEN indicates that the input interprocess_token
   was defective.  Return values other than major_status and
   minor_status are undefined.

   o  GSS_S_UNAVAILABLE indicates that the context import facility is
   not available for use on the referenced context.  Return values other
   than major_status and minor_status are undefined.

   o  GSS_S_UNAUTHORIZED indicates that the context represented by the
   input interprocess_token is unauthorized for transfer to the caller.
   Return values other than major_status and minor_status are undefined.

   o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level. Return values other than
   major_status and minor_status are undefined.

   This call processes an interprocess token generated by
   GSS_Export_sec_context(), making the transferred context available
   for use by the caller.  After a successful GSS_Import_sec_context()
   operation, the imported context is available for use by the importing
   process. In particular, the imported context is usable for all per-
   message operations and may be deleted or exported by its importer.
   The inability to receive delegated credentials through



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   gss_import_sec_context() precludes establishment of new contexts
   based on information delegated to the importer's end system within
   the context which is being imported, unless those delegated
   credentials are obtained through separate routines (e.g., XGSS-API
   calls) outside the GSS-V2 definition.

   For further discussion of the security and authorization issues
   regarding this call, please see the discussion in Section 2.2.8.

2.3:  Per-message calls

   This group of calls is used to perform per-message protection
   processing on an established security context. None of these calls
   block pending network interactions. These calls may be invoked by a
   context's initiator or by the context's target.  The four members of
   this group should be considered as two pairs; the output from
   GSS_GetMIC() is properly input to GSS_VerifyMIC(), and the output
   from GSS_Wrap() is properly input to GSS_Unwrap().

   GSS_GetMIC() and GSS_VerifyMIC() support data origin authentication
   and data integrity services. When GSS_GetMIC() is invoked on an input
   message, it yields a per-message token containing data items which
   allow underlying mechanisms to provide the specified security
   services. The original message, along with the generated per-message
   token, is passed to the remote peer; these two data elements are
   processed by GSS_VerifyMIC(), which validates the message in
   conjunction with the separate token.

   GSS_Wrap() and GSS_Unwrap() support caller-requested confidentiality
   in addition to the data origin authentication and data integrity
   services offered by GSS_GetMIC() and GSS_VerifyMIC(). GSS_Wrap()
   outputs a single data element, encapsulating optionally enciphered
   user data as well as associated token data items.  The data element
   output from GSS_Wrap() is passed to the remote peer and processed by
   GSS_Unwrap() at that system. GSS_Unwrap() combines decipherment (as
   required) with validation of data items related to authentication and
   integrity.

   Although zero-length tokens are never returned by GSS calls for
   transfer to a context's peer, a zero-length object may be passed by a
   caller into GSS_Wrap(), in which case the corresponding peer calling
   GSS_Unwrap() on the transferred token will receive a zero-length
   object as output from GSS_Unwrap().  Similarly, GSS_GetMIC() can be
   called on an empty object, yielding a MIC which GSS_VerifyMIC() will
   successfully verify against the active security context in
   conjunction with a zero-length object.





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2.3.1:  GSS_GetMIC call

   Note: This call is functionally equivalent to the GSS_Sign call as
   defined in previous versions of this specification. In the interests
   of backward compatibility, it is recommended that implementations
   support this function under both names for the present; future
   references to this function as GSS_Sign are deprecated.

   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  qop_req INTEGER, -- 0 specifies default QOP

   o  message OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  per_msg_token OCTET STRING  -- caller must release
   -- with GSS_Release_buffer()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that an integrity check, suitable for an
   established security context, was successfully applied and that the
   message and corresponding per_msg_token are ready for transmission.

   o  GSS_S_CONTEXT_EXPIRED indicates that context-related data items
   have expired, so that the requested operation cannot be performed.

   o  GSS_S_NO_CONTEXT indicates that no context was recognized for the
   input context_handle provided.

   o  GSS_S_BAD_QOP indicates that the provided QOP value is not
   recognized or supported for the context.

   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the requested operation could not be performed for reasons
   unspecified at the GSS-API level.

   Using the security context referenced by context_handle, apply an
   integrity check to the input message (along with timestamps and/or
   other data included in support of mech_type-specific mechanisms) and
   (if GSS_S_COMPLETE status is indicated) return the result in



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   per_msg_token. The qop_req parameter, interpretation of which is
   discussed in Section 1.2.4, allows quality-of-protection control. The
   caller passes the message and the per_msg_token to the target.

   The GSS_GetMIC() function completes before the message and
   per_msg_token is sent to the peer; successful application of
   GSS_GetMIC() does not guarantee that a corresponding GSS_VerifyMIC()
   has been (or can necessarily be) performed successfully when the
   message arrives at the destination.

   Mechanisms which do not support per-message protection services
   should return GSS_S_FAILURE if this routine is called.

2.3.2:  GSS_VerifyMIC call

   Note: This call is functionally equivalent to the GSS_Verify call as
   defined in previous versions of this specification. In the interests
   of backward compatibility, it is recommended that implementations
   support this function under both names for the present; future
   references to this function as GSS_Verify are deprecated.

   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  message OCTET STRING,

   o  per_msg_token OCTET STRING

   Outputs:

   o  qop_state INTEGER,

   o  major_status INTEGER,

   o  minor_status INTEGER,

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the message was successfully
   verified.

   o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
   on the received per_msg_token failed, preventing further processing
   from being performed with that token.

   o  GSS_S_BAD_SIG (GSS_S_BAD_MIC) indicates that the received
   per_msg_token contains an incorrect integrity check for the message.



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   o  GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN, and
   GSS_S_GAP_TOKEN values appear in conjunction with the optional per-
   message replay detection features described in Section 1.2.3; their
   semantics are described in that section.

   o  GSS_S_CONTEXT_EXPIRED indicates that context-related data items
   have expired, so that the requested operation cannot be performed.

   o  GSS_S_NO_CONTEXT indicates that no context was recognized for the
   input context_handle provided.

   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the GSS_VerifyMIC() operation could not be performed for reasons
   unspecified at the GSS-API level.

   Using the security context referenced by context_handle, verify that
   the input per_msg_token contains an appropriate integrity check for
   the input message, and apply any active replay detection or
   sequencing features. Returns an indication of the quality-of-
   protection applied to the processed message in the qop_state result.

   Mechanisms which do not support per-message protection services
   should return GSS_S_FAILURE if this routine is called.

2.3.3: GSS_Wrap call

   Note: This call is functionally equivalent to the GSS_Seal call as
   defined in previous versions of this specification. In the interests
   of backward compatibility, it is recommended that implementations
   support this function under both names for the present; future
   references to this function as GSS_Seal are deprecated.

   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  conf_req_flag BOOLEAN,

   o  qop_req INTEGER, -- 0 specifies default QOP

   o  input_message OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,




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   o  conf_state BOOLEAN,

   o  output_message OCTET STRING  -- caller must release with
   -- GSS_Release_buffer()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the input_message was successfully
   processed and that the output_message is ready for transmission.

   o  GSS_S_CONTEXT_EXPIRED indicates that context-related data items
   have expired, so that the requested operation cannot be performed.

   o  GSS_S_NO_CONTEXT indicates that no context was recognized for the
   input context_handle provided.

   o  GSS_S_BAD_QOP indicates that the provided QOP value is not
   recognized or supported for the context.

   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the GSS_Wrap() operation could not be performed for reasons
   unspecified at the GSS-API level.

   Performs the data origin authentication and data integrity functions
   of GSS_GetMIC().  If the input conf_req_flag is TRUE, requests that
   confidentiality be applied to the input_message.  Confidentiality may
   not be supported in all mech_types or by all implementations; the
   returned conf_state flag indicates whether confidentiality was
   provided for the input_message. The qop_req parameter, interpretation
   of which is discussed in Section 1.2.4, allows quality-of-protection
   control.

   When GSS_S_COMPLETE status is returned, the GSS_Wrap() call yields a
   single output_message data element containing (optionally enciphered)
   user data as well as control information.

   Mechanisms which do not support per-message protection services
   should return GSS_S_FAILURE if this routine is called.

2.3.4: GSS_Unwrap call

   Note: This call is functionally equivalent to the GSS_Unseal call as
   defined in previous versions of this specification. In the interests
   of backward compatibility, it is recommended that implementations
   support this function under both names for the present; future
   references to this function as GSS_Unseal are deprecated.





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   Inputs:

   o  context_handle CONTEXT HANDLE,

   o  input_message OCTET STRING

   Outputs:

   o  conf_state BOOLEAN,

   o  qop_state INTEGER,

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  output_message OCTET STRING  -- caller must release with
   -- GSS_Release_buffer()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the input_message was successfully
   processed and that the resulting output_message is available.

   o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
   on the per_msg_token extracted from the input_message failed,
   preventing further processing from being performed.

   o  GSS_S_BAD_SIG (GSS_S_BAD_MIC) indicates that an incorrect
   integrity check was detected for the message.

   o  GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN, and
   GSS_S_GAP_TOKEN values appear in conjunction with the optional per-
   message replay detection features described in Section 1.2.3; their
   semantics are described in that section.

   o  GSS_S_CONTEXT_EXPIRED indicates that context-related data items
   have expired, so that the requested operation cannot be performed.

   o  GSS_S_NO_CONTEXT indicates that no context was recognized for the
   input context_handle provided.

   o  GSS_S_FAILURE indicates that the context is recognized, but that
   the GSS_Unwrap() operation could not be performed for reasons
   unspecified at the GSS-API level.






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   Processes a data element generated (and optionally enciphered) by
   GSS_Wrap(), provided as input_message. The returned conf_state value
   indicates whether confidentiality was applied to the input_message.
   If conf_state is TRUE, GSS_Unwrap() has deciphered the input_message.
   Returns an indication of the quality-of-protection applied to the
   processed message in the qop_state result. GSS_Unwrap() performs the
   data integrity and data origin authentication checking functions of
   GSS_VerifyMIC() on the plaintext data. Plaintext data is returned in
   output_message.

   Mechanisms which do not support per-message protection services
   should return GSS_S_FAILURE if this routine is called.

2.4:  Support calls

   This group of calls provides support functions useful to GSS-API
   callers, independent of the state of established contexts. Their
   characterization with regard to blocking or non-blocking status in
   terms of network interactions is unspecified.

2.4.1:  GSS_Display_status call

   Inputs:

   o  status_value INTEGER, -- GSS-API major_status or minor_status
   -- return value

   o  status_type INTEGER, -- 1 if major_status, 2 if minor_status

   o  mech_type OBJECT IDENTIFIER -- mech_type to be used for
   -- minor_status translation

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  status_string_set SET OF OCTET STRING  -- required calls for
   -- release by caller are specific to language bindings

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a valid printable status
   representation (possibly representing more than one status event
   encoded within the status_value) is available in the returned
   status_string_set.




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   o  GSS_S_BAD_MECH indicates that translation in accordance with an
   unsupported mech_type was requested, so translation could not be
   performed.

   o  GSS_S_BAD_STATUS indicates that the input status_value was
   invalid, or that the input status_type carried a value other than 1
   or 2, so translation could not be performed.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Provides a means for callers to translate GSS-API-returned major and
   minor status codes into printable string representations.  Note: some
   language bindings may employ an iterative approach in order to emit
   successive status components; this approach is acceptable but not
   required for conformance with the current specification.

   Although not contemplated in [RFC-2078], it has been observed that
   some existing GSS-API implementations return GSS_S_CONTINUE_NEEDED
   status when iterating through successive messages returned from
   GSS_Display_status(). This behavior is deprecated;
   GSS_S_CONTINUE_NEEDED should be returned only by
   GSS_Init_sec_context() and GSS_Accept_sec_context().  For maximal
   portability, however, it is recommended that defensive callers be
   able to accept and ignore GSS_S_CONTINUE_NEEDED status if indicated
   by GSS_Display_status() or any other call other than
   GSS_Init_sec_context() or GSS_Accept_sec_context().

2.4.2:  GSS_Indicate_mechs call

   Input:

   o  (none)

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  mech_set SET OF OBJECT IDENTIFIER  -- caller must release
   -- with GSS_Release_oid_set()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a set of available mechanisms has
   been returned in mech_set.




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   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to determine the set of mechanism types available on
   the local system. This call is intended for support of specialized
   callers who need to request non-default mech_type sets from GSS-API
   calls which accept input mechanism type specifiers.

2.4.3:  GSS_Compare_name call

   Inputs:

   o  name1 INTERNAL NAME,

   o  name2 INTERNAL NAME

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  name_equal BOOLEAN

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that name1 and name2 were comparable, and
   that the name_equal result indicates whether name1 and name2
   represent the same entity.

   o  GSS_S_BAD_NAMETYPE indicates that the two input names' types are
   different and incomparable, so that the comparison operation could
   not be completed.

   o  GSS_S_BAD_NAME indicates that one or both of the input names was
   ill-formed in terms of its internal type specifier, so the comparison
   operation could not be completed.

   o  GSS_S_FAILURE indicates that the call's operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to compare two internal name representations to
   determine whether they refer to the same entity.  If either name
   presented to GSS_Compare_name() denotes an anonymous principal,
   GSS_Compare_name() shall indicate FALSE.  It is not required that
   either or both inputs name1 and name2 be MNs; for some





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   implementations and cases, GSS_S_BAD_NAMETYPE may be returned,
   indicating name incomparability, for the case where neither input
   name is an MN.

2.4.4:  GSS_Display_name call

   Inputs:

   o  name INTERNAL NAME

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  name_string OCTET STRING, -- caller must release
   -- with GSS_Release_buffer()

   o  name_type OBJECT IDENTIFIER  -- caller should treat
   -- as read-only; does not need to be released

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a valid printable name
   representation is available in the returned name_string.

   o  GSS_S_BAD_NAME indicates that the contents of the provided name
   were inconsistent with the internally-indicated name type, so no
   printable representation could be generated.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to translate an internal name representation into a
   printable form with associated namespace type descriptor. The syntax
   of the printable form is a local matter.

   If the input name represents an anonymous identity, a reserved value
   (GSS_C_NT_ANONYMOUS) shall be returned for name_type.

   The GSS_C_NO_OID name type is to be returned only when the
   corresponding internal name was created through import with
   GSS_C_NO_OID. It is acceptable for mechanisms to normalize names
   imported with GSS_C_NO_OID into other supported types and, therefore,
   to display them with types other than GSS_C_NO_OID.





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2.4.5:  GSS_Import_name call

   Inputs:

   o  input_name_string OCTET STRING,

   o  input_name_type OBJECT IDENTIFIER

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  output_name INTERNAL NAME  -- caller must release with
   -- GSS_Release_name()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a valid name representation is
   output in output_name and described by the type value in
   output_name_type.

   o  GSS_S_BAD_NAMETYPE indicates that the input_name_type is
   unsupported by the applicable underlying GSS-API mechanism(s), so the
   import operation could not be completed.

   o  GSS_S_BAD_NAME indicates that the provided input_name_string is
   ill-formed in terms of the input_name_type, so the import operation
   could not be completed.

   o  GSS_S_BAD_MECH indicates that the input presented for import was
   an exported name object and that its enclosed mechanism type was not
   recognized or was unsupported by the GSS-API implementation.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to provide a name representation as a contiguous octet
   string, designate the type of namespace in conjunction with which it
   should be parsed, and convert that representation to an internal form
   suitable for input to other GSS-API routines.  The syntax of the
   input_name_string is defined in conjunction with its associated name
   type; depending on the input_name_type, the associated
   input_name_string may or may not be a printable string.  If the
   input_name_type's value is GSS_C_NO_OID, a mechanism-specific default
   printable syntax (which shall be specified in the corresponding GSS-
   V2 mechanism specification) is assumed for the input_name_string;



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   other input_name_type values as registered by GSS-API implementations
   can be used to indicate specific non-default name syntaxes. Note: The
   input_name_type argument serves to describe and qualify the
   interpretation of the associated input_name_string; it does not
   specify the data type of the returned output_name.

   If a mechanism claims support for a particular name type, its
   GSS_Import_name() operation shall be able to accept all possible
   values conformant to the external name syntax as defined for that
   name type.  These imported values may correspond to:

      (1) locally registered entities (for which credentials may be
      acquired),

      (2) non-local entities (for which local credentials cannot be
      acquired, but which may be referenced as targets of initiated
      security contexts or initiators of accepted security contexts), or
      to

      (3) neither of the above.

   Determination of whether a particular name belongs to class (1), (2),
   or (3) as described above is not guaranteed to be performed by the
   GSS_Import_name() function.

   The internal name generated by a GSS_Import_name() operation may be a
   single-mechanism MN, and is likely to be an MN within a single-
   mechanism implementation, but portable callers must not depend on
   this property (and must not, therefore, assume that the output from
   GSS_Import_name() can be passed directly to GSS_Export_name() without
   first being processed through GSS_Canonicalize_name()).

2.4.6: GSS_Release_name call

   Inputs:

   o  name INTERNAL NAME

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the storage associated with the
   input name was successfully released.



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   o  GSS_S_BAD_NAME indicates that the input name argument did not
   contain a valid name.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to release the storage associated with an internal
   name representation.  This call's specific behavior depends on the
   language and programming environment within which a GSS-API
   implementation operates, and is therefore detailed within applicable
   bindings specifications; in particular, implementation and invocation
   of this call may be superfluous (and may be omitted) within bindings
   where memory management is automatic.

2.4.7: GSS_Release_buffer call

   Inputs:

   o  buffer OCTET STRING

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the storage associated with the
   input buffer was successfully released.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to release the storage associated with an OCTET STRING
   buffer allocated by another GSS-API call.  This call's specific
   behavior depends on the language and programming environment within
   which a GSS-API implementation operates, and is therefore detailed
   within applicable bindings specifications; in particular,
   implementation and invocation of this call may be superfluous (and
   may be omitted) within bindings where memory management is automatic.

2.4.8: GSS_Release_OID_set call

   Inputs:

   o  buffer SET OF OBJECT IDENTIFIER




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   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the storage associated with the
   input object identifier set was successfully released.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to release the storage associated with an object
   identifier set object allocated by another GSS-API call.  This call's
   specific behavior depends on the language and programming environment
   within which a GSS-API implementation operates, and is therefore
   detailed within applicable bindings specifications; in particular,
   implementation and invocation of this call may be superfluous (and
   may be omitted) within bindings where memory management is automatic.

2.4.9: GSS_Create_empty_OID_set call

   Inputs:

   o  (none)

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  oid_set SET OF OBJECT IDENTIFIER  -- caller must release
   -- with GSS_Release_oid_set()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates successful completion

   o  GSS_S_FAILURE indicates that the operation failed

   Creates an object identifier set containing no object identifiers, to
   which members may be subsequently added using the
   GSS_Add_OID_set_member() routine.  These routines are intended to be
   used to construct sets of mechanism object identifiers, for input to
   GSS_Acquire_cred().



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2.4.10: GSS_Add_OID_set_member call

   Inputs:

   o  member_oid OBJECT IDENTIFIER,

   o  oid_set SET OF OBJECT IDENTIFIER

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   Return major_status codes:

   o  GSS_S_COMPLETE indicates successful completion

   o  GSS_S_FAILURE indicates that the operation failed

   Adds an Object Identifier to an Object Identifier set.  This routine
   is intended for use in conjunction with GSS_Create_empty_OID_set()
   when constructing a set of mechanism OIDs for input to
   GSS_Acquire_cred().

2.4.11: GSS_Test_OID_set_member call

   Inputs:

   o  member OBJECT IDENTIFIER,

   o  set SET OF OBJECT IDENTIFIER

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  present BOOLEAN

   Return major_status codes:

   o  GSS_S_COMPLETE indicates successful completion

   o  GSS_S_FAILURE indicates that the operation failed





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   Interrogates an Object Identifier set to determine whether a
   specified Object Identifier is a member.  This routine is intended to
   be used with OID sets returned by GSS_Indicate_mechs(),
   GSS_Acquire_cred(), and GSS_Inquire_cred().

2.4.12:  GSS_Inquire_names_for_mech call

   Input:

   o  input_mech_type OBJECT IDENTIFIER, -- mechanism type

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  name_type_set SET OF OBJECT IDENTIFIER -- caller must release
   -- with GSS_Release_oid_set()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that the output name_type_set contains a
   list of name types which are supported by the locally available
   mechanism identified by input_mech_type.

   o  GSS_S_BAD_MECH indicates that the mechanism identified by
   input_mech_type was unsupported within the local implementation,
   causing the query to fail.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   Allows callers to determine the set of name types which are
   supportable by a specific locally-available mechanism.

2.4.13: GSS_Inquire_mechs_for_name call

   Inputs:

   o  input_name INTERNAL NAME,

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,




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   o  mech_types SET OF OBJECT IDENTIFIER  -- caller must release
   -- with GSS_Release_oid_set()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a set of object identifiers,
   corresponding to the set of mechanisms suitable for processing the
   input_name, is available in mech_types.

   o  GSS_S_BAD_NAME indicates that the input_name was ill-formed and
   could not be processed.

   o  GSS_S_BAD_NAMETYPE indicates that the input_name parameter
   contained an invalid name type or a name type unsupported by the
   GSS-API implementation.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   This routine returns the mechanism set with which the input_name may
   be processed.

   Each mechanism returned will recognize at least one element within
   the name. It is permissible for this routine to be implemented within
   a mechanism-independent GSS-API layer, using the type information
   contained within the presented name, and based on registration
   information provided by individual mechanism implementations.  This
   means that the returned mech_types result may indicate that a
   particular mechanism will understand a particular name when in fact
   it would refuse to accept that name as input to
   GSS_Canonicalize_name(), GSS_Init_sec_context(), GSS_Acquire_cred(),
   or GSS_Add_cred(), due to some property of the particular name rather
   than a property of the name type.  Thus, this routine should be used
   only as a pre-filter for a call to a subsequent mechanism-specific
   routine.

2.4.14: GSS_Canonicalize_name call

   Inputs:

   o  input_name INTERNAL NAME,

   o  mech_type OBJECT IDENTIFIER  -- must be explicit mechanism,
   -- not "default" specifier or identifier of negotiating mechanism

   Outputs:

   o  major_status INTEGER,



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   o  minor_status INTEGER,

   o  output_name INTERNAL NAME  -- caller must release with
   -- GSS_Release_name()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a mechanism-specific reduction of
   the input_name, as processed by the mechanism identified by
   mech_type, is available in output_name.

   o  GSS_S_BAD_MECH indicates that the identified mechanism is
   unsupported for this operation; this may correspond either to a
   mechanism wholly unsupported by the local GSS-API implementation or
   to a negotiating mechanism with which the canonicalization operation
   cannot be performed.

   o  GSS_S_BAD_NAMETYPE indicates that the input name does not contain
   an element with suitable type for processing by the identified
   mechanism.

   o  GSS_S_BAD_NAME indicates that the input name contains an element
   with suitable type for processing by the identified mechanism, but
   that this element could not be processed successfully.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   This routine reduces a GSS-API internal name input_name, which may in
   general contain elements corresponding to multiple mechanisms, to a
   mechanism-specific Mechanism Name (MN) output_name by applying the
   translations corresponding to the mechanism identified by mech_type.
   The contents of input_name are unaffected by the
   GSS_Canonicalize_name() operation.  References to output_name will
   remain valid until output_name is released, independent of whether or
   not input_name is subsequently released.

2.4.15: GSS_Export_name call

   Inputs:

   o  input_name INTERNAL NAME, -- required to be MN

   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,



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   o  output_name OCTET STRING  -- caller must release
   -- with GSS_Release_buffer()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that a flat representation of the input
   name is available in output_name.

   o  GSS_S_NAME_NOT_MN indicates that the input name contained elements
   corresponding to multiple mechanisms, so cannot be exported into a
   single-mechanism flat form.

   o  GSS_S_BAD_NAME indicates that the input name was an MN, but could
   not be processed.

   o  GSS_S_BAD_NAMETYPE indicates that the input name was an MN, but
   that its type is unsupported by the GSS-API implementation.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   This routine creates a flat name representation, suitable for
   bytewise comparison or for input to GSS_Import_name() in conjunction
   with the reserved GSS-API Exported Name Object OID, from a internal-
   form Mechanism Name (MN) as emitted, e.g., by GSS_Canonicalize_name()
   or GSS_Accept_sec_context().

   The emitted GSS-API Exported Name Object is self-describing; no
   associated parameter-level OID need be emitted by this call.  This
   flat representation consists of a mechanism-independent wrapper
   layer, defined in Section 3.2 of this document, enclosing a
   mechanism-defined name representation.

   In all cases, the flat name output by GSS_Export_name() to correspond
   to a particular input MN must be invariant over time within a
   particular installation.

   The GSS_S_NAME_NOT_MN status code is provided to enable
   implementations to reject input names which are not MNs.  It is not,
   however, required for purposes of conformance to this specification
   that all non-MN input names must necessarily be rejected.

2.4.16: GSS_Duplicate_name call

   Inputs:

   o  src_name INTERNAL NAME




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   Outputs:

   o  major_status INTEGER,

   o  minor_status INTEGER,

   o  dest_name INTERNAL NAME  -- caller must release
   -- with GSS_Release_name()

   Return major_status codes:

   o  GSS_S_COMPLETE indicates that dest_name references an internal
   name object containing the same name as passed to src_name.

   o  GSS_S_BAD_NAME indicates that the input name was invalid.

   o  GSS_S_FAILURE indicates that the requested operation could not be
   performed for reasons unspecified at the GSS-API level.

   This routine takes input internal name src_name, and returns another
   reference (dest_name) to that name which can be used even if src_name
   is later freed.  (Note: This may be implemented by copying or through
   use of reference counts.)

3: Data Structure Definitions for GSS-V2 Usage

   Subsections of this section define, for interoperability and
   portability purposes, certain data structures for use with GSS-V2.

3.1: Mechanism-Independent Token Format

   This section specifies a mechanism-independent level of encapsulating
   representation for the initial token of a GSS-API context
   establishment sequence, incorporating an identifier of the mechanism
   type to be used on that context and enabling tokens to be interpreted
   unambiguously at GSS-API peers. Use of this format is required for
   initial context establishment tokens of Internet standards-track
   GSS-API mechanisms; use in non-initial tokens is optional.

   The encoding format for the token tag is derived from ASN.1 and DER
   (per illustrative ASN.1 syntax included later within this
   subsection), but its concrete representation is defined directly in
   terms of octets rather than at the ASN.1 level in order to facilitate
   interoperable implementation without use of general ASN.1 processing
   code.  The token tag consists of the following elements, in order:

      1. 0x60 -- Tag for [APPLICATION 0] SEQUENCE; indicates that
      -- constructed form, definite length encoding follows.



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      2. Token length octets, specifying length of subsequent data
      (i.e., the summed lengths of elements 3-5 in this list, and of the
      mechanism-defined token object following the tag).  This element
      comprises a variable number of octets:

         2a. If the indicated value is less than 128, it shall be
         represented in a single octet with bit 8 (high order) set to
         "0" and the remaining bits representing the value.

         2b. If the indicated value is 128 or more, it shall be
         represented in two or more octets, with bit 8 of the first
         octet set to "1" and the remaining bits of the first octet
         specifying the number of additional octets.  The subsequent
         octets carry the value, 8 bits per octet, most significant
         digit first.  The minimum number of octets shall be used to
         encode the length (i.e., no octets representing leading zeros
         shall be included within the length encoding).

      3. 0x06 -- Tag for OBJECT IDENTIFIER

      4. Object identifier length -- length (number of octets) of
      -- the encoded object identifier contained in element 5,
      -- encoded per rules as described in 2a. and 2b. above.

      5. Object identifier octets -- variable number of octets,
      -- encoded per ASN.1 BER rules:

         5a. The first octet contains the sum of two values: (1) the
         top-level object identifier component, multiplied by 40
         (decimal), and (2) the second-level object identifier
         component.  This special case is the only point within an
         object identifier encoding where a single octet represents
         contents of more than one component.

         5b. Subsequent octets, if required, encode successively-lower
         components in the represented object identifier.  A component's
         encoding may span multiple octets, encoding 7 bits per octet
         (most significant bits first) and with bit 8 set to "1" on all
         but the final octet in the component's encoding.  The minimum
         number of octets shall be used to encode each component (i.e.,
         no octets representing leading zeros shall be included within a
         component's encoding).

      (Note: In many implementations, elements 3-5 may be stored and
      referenced as a contiguous string constant.)






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   The token tag is immediately followed by a mechanism-defined token
   object.  Note that no independent size specifier intervenes following
   the object identifier value to indicate the size of the mechanism-
   defined token object.  While ASN.1 usage within mechanism-defined
   tokens is permitted, there is no requirement that the mechanism-
   specific innerContextToken, innerMsgToken, and sealedUserData data
   elements must employ ASN.1 BER/DER encoding conventions.

   The following ASN.1 syntax is included for descriptive purposes only,
   to illustrate structural relationships among token and tag objects.
   For interoperability purposes, token and tag encoding shall be
   performed using the concrete encoding procedures described earlier in
   this subsection.

      GSS-API DEFINITIONS ::=

      BEGIN

      MechType ::= OBJECT IDENTIFIER
      -- data structure definitions
      -- callers must be able to distinguish among
      -- InitialContextToken, SubsequentContextToken,
      -- PerMsgToken, and SealedMessage data elements
      -- based on the usage in which they occur

      InitialContextToken ::=
      -- option indication (delegation, etc.) indicated within
      -- mechanism-specific token
      [APPLICATION 0] IMPLICIT SEQUENCE {
              thisMech MechType,
              innerContextToken ANY DEFINED BY thisMech
                 -- contents mechanism-specific
                 -- ASN.1 structure not required
              }

      SubsequentContextToken ::= innerContextToken ANY
      -- interpretation based on predecessor InitialContextToken
      -- ASN.1 structure not required

      PerMsgToken ::=
      -- as emitted by GSS_GetMIC and processed by GSS_VerifyMIC
      -- ASN.1 structure not required
              innerMsgToken ANY

      SealedMessage ::=
      -- as emitted by GSS_Wrap and processed by GSS_Unwrap
      -- includes internal, mechanism-defined indicator
      -- of whether or not encrypted



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      -- ASN.1 structure not required
              sealedUserData ANY

      END

3.2: Mechanism-Independent Exported Name Object Format

   This section specifies a mechanism-independent level of encapsulating
   representation for names exported via the GSS_Export_name() call,
   including an object identifier representing the exporting mechanism.
   The format of names encapsulated via this representation shall be
   defined within individual mechanism drafts.  The Object Identifier
   value to indicate names of this type is defined in Section 4.7 of
   this document.

   No name type OID is included in this mechanism-independent level of
   format definition, since (depending on individual mechanism
   specifications) the enclosed name may be implicitly typed or may be
   explicitly typed using a means other than OID encoding.

   The bytes within MECH_OID_LEN and NAME_LEN elements are represented
   most significant byte first (equivalently, in IP network byte order).

        Length    Name          Description

        2               TOK_ID          Token Identifier
                                        For exported name objects, this
                                        must be hex 04 01.
        2               MECH_OID_LEN    Length of the Mechanism OID
        MECH_OID_LEN    MECH_OID        Mechanism OID, in DER
        4               NAME_LEN        Length of name
        NAME_LEN        NAME            Exported name; format defined in
                                        applicable mechanism draft.

   A concrete example of the contents of an exported name object,
   derived from the Kerberos Version 5 mechanism, is as follows:

   04 01 00 0B 06 09 2A 86 48 86 F7 12 01 02 02 hx xx xx xl pp qq ... zz

   04 01        mandatory token identifier

   00 0B        2-byte length of the immediately following DER-encoded
                ASN.1 value of type OID, most significant octet first








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   06 09 2A 86 48 86 F7 12 01 02 02    DER-encoded ASN.1 value
                                       of type OID; Kerberos V5
                                       mechanism OID indicates
                                       Kerberos V5 exported name

          in Detail:      06                  Identifier octet (6=OID)
                          09                           Length octet(s)
                          2A 86 48 86 F7 12 01 02 02   Content octet(s)

   hx xx xx xl   4-byte length of the immediately following exported
                 name blob, most significant octet first

   pp qq ... zz  exported name blob of specified length,
                 bits and bytes specified in the
                 (Kerberos 5) GSS-API v2 mechanism spec

4: Name Type Definitions

   This section includes definitions for name types and associated
   syntaxes which are defined in a mechanism-independent fashion at the
   GSS-API level rather than being defined in individual mechanism
   specifications.

4.1: Host-Based Service Name Form

   This name form shall be represented by the Object Identifier:

   {iso(1) member-body(2) United States(840) mit(113554) infosys(1)
   "gssapi(2) generic(1) service_name(4)}.

   The recommended symbolic name for this type is
   "GSS_C_NT_HOSTBASED_SERVICE".

   For reasons of compatibility with existing implementations, it is
   recommended that this OID be used rather than the alternate value as
   included in [RFC-2078]:

   {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
   2(gss-host-based-services)}

   While it is not recommended that this alternate value be emitted on
   output by GSS implementations, it is recommended that it be accepted
   on input as equivalent to the recommended value.








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   This name type is used to represent services associated with host
   computers.  Support for this name form is recommended to mechanism
   designers in the interests of portability, but is not mandated by
   this specification. This name form is constructed using two elements,
   "service" and "hostname", as follows:

   service@hostname

   When a reference to a name of this type is resolved, the "hostname"
   may (as an example implementation strategy) be canonicalized by
   attempting a DNS lookup and using the fully-qualified domain name
   which is returned, or by using the "hostname" as provided if the DNS
   lookup fails.  The canonicalization operation also maps the host's
   name into lower-case characters.

   The "hostname" element may be omitted. If no "@" separator is
   included, the entire name is interpreted as the service specifier,
   with the "hostname" defaulted to the canonicalized name of the local
   host.

   Documents specifying means for GSS integration into a particular
   protocol should state either:

      (a) that a specific IANA-registered name associated with that
      protocol shall be used for the "service" element (this admits, if
      needed, the possibility that a single name can be registered and
      shared among a related set of protocols), or

      (b) that the generic name "host" shall be used for the "service"
      element, or

      (c) that, for that protocol, fallback in specified order (a, then
      b) or (b, then a) shall be applied.

   IANA registration of specific names per (a) should be handled in
   accordance with the "Specification Required" assignment policy,
   defined by BCP 26, RFC 2434 as follows: "Values and their meaning
   must be documented in an RFC or other available reference, in
   sufficient detail so that interoperability between independent
   implementations is possible."

4.2: User Name Form

   This name form shall be represented by the Object Identifier {iso(1)
   member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
   generic(1) user_name(1)}. The recommended mechanism-independent
   symbolic name for this type is "GSS_C_NT_USER_NAME". (Note: the same




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   name form and OID is defined within the Kerberos V5 GSS-API
   mechanism, but the symbolic name recommended there begins with a
   "GSS_KRB5_NT_" prefix.)

   This name type is used to indicate a named user on a local system.
   Its syntax and interpretation may be OS-specific. This name form is
   constructed as:

   username

4.3: Machine UID Form

   This name form shall be represented by the Object Identifier {iso(1)
   member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
   generic(1) machine_uid_name(2)}.  The recommended mechanism-
   independent symbolic name for this type is
   "GSS_C_NT_MACHINE_UID_NAME".  (Note: the same name form and OID is
   defined within the Kerberos V5 GSS-API mechanism, but the symbolic
   name recommended there begins with a "GSS_KRB5_NT_" prefix.)

   This name type is used to indicate a numeric user identifier
   corresponding to a user on a local system.  Its interpretation is
   OS-specific.  The gss_buffer_desc representing a name of this type
   should contain a locally-significant user ID, represented in host
   byte order.  The GSS_Import_name() operation resolves this uid into a
   username, which is then treated as the User Name Form.

4.4: String UID Form

   This name form shall be represented by the Object Identifier {iso(1)
   member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
   generic(1) string_uid_name(3)}.  The recommended symbolic name for
   this type is "GSS_C_NT_STRING_UID_NAME".  (Note: the same name form
   and OID is defined within the Kerberos V5 GSS-API mechanism, but the
   symbolic name recommended there begins with a "GSS_KRB5_NT_" prefix.)

   This name type is used to indicate a string of digits representing
   the numeric user identifier of a user on a local system.  Its
   interpretation is OS-specific. This name type is similar to the
   Machine UID Form, except that the buffer contains a string
   representing the user ID.

4.5: Anonymous Nametype

   The following Object Identifier value is provided as a means to
   identify anonymous names, and can be compared against in order to
   determine, in a mechanism-independent fashion, whether a name refers
   to an anonymous principal:



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   {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
   3(gss-anonymous-name)}

   The recommended symbolic name corresponding to this definition is
   GSS_C_NT_ANONYMOUS.

4.6: GSS_C_NO_OID

   The recommended symbolic name GSS_C_NO_OID corresponds to a null
   input value instead of an actual object identifier.  Where specified,
   it indicates interpretation of an associated name based on a
   mechanism-specific default printable syntax.

4.7: Exported Name Object

   Name objects of the Mechanism-Independent Exported Name Object type,
   as defined in Section 3.2 of this document, will be identified with
   the following Object Identifier:

   {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
   4(gss-api-exported-name)}

   The recommended symbolic name corresponding to this definition is
   GSS_C_NT_EXPORT_NAME.

4.8: GSS_C_NO_NAME

   The recommended symbolic name GSS_C_NO_NAME indicates that no name is
   being passed within a particular value of a parameter used for the
   purpose of transferring names. Note: GSS_C_NO_NAME is not an actual
   name type, and is not represented by an OID; its acceptability in
   lieu of an actual name is confined to specific calls
   (GSS_Acquire_cred(), GSS_Add_cred(), and GSS_Init_sec_context()) with
   usages as identified within this specification.

5:  Mechanism-Specific Example Scenarios

   This section provides illustrative overviews of the use of various
   candidate mechanism types to support the GSS-API. These discussions
   are intended primarily for readers familiar with specific security
   technologies, demonstrating how GSS-API functions can be used and
   implemented by candidate underlying mechanisms. They should not be
   regarded as constrictive to implementations or as defining the only
   means through which GSS-API functions can be realized with a
   particular underlying technology, and do not demonstrate all GSS-API
   features with each technology.





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5.1: Kerberos V5, single-TGT

   OS-specific login functions yield a TGT to the local realm Kerberos
   server; TGT is placed in a credentials structure for the client.
   Client calls GSS_Acquire_cred()  to acquire a cred_handle in order to
   reference the credentials for use in establishing security contexts.

   Client calls GSS_Init_sec_context().  If the requested service is
   located in a different realm, GSS_Init_sec_context()  gets the
   necessary TGT/key pairs needed to traverse the path from local to
   target realm; these data are placed in the owner's TGT cache. After
   any needed remote realm resolution, GSS_Init_sec_context() yields a
   service ticket to the requested service with a corresponding session
   key; these data are stored in conjunction with the context. GSS-API
   code sends KRB_TGS_REQ request(s) and receives KRB_TGS_REP
   response(s) (in the successful case) or KRB_ERROR.

   Assuming success, GSS_Init_sec_context()  builds a Kerberos-formatted
   KRB_AP_REQ message, and returns it in output_token.  The client sends
   the output_token to the service.

   The service passes the received token as the input_token argument to
   GSS_Accept_sec_context(),  which verifies the authenticator, provides
   the service with the client's authenticated name, and returns an
   output_context_handle.

   Both parties now hold the session key associated with the service
   ticket, and can use this key in subsequent GSS_GetMIC(),
   GSS_VerifyMIC(),  GSS_Wrap(), and GSS_Unwrap() operations.

5.2: Kerberos V5, double-TGT

   TGT acquisition as above.

   Note: To avoid unnecessary frequent invocations of error paths when
   implementing the GSS-API atop Kerberos V5, it seems appropriate to
   represent "single-TGT K-V5" and "double-TGT K-V5" with separate
   mech_types, and this discussion makes that assumption.

   Based on the (specified or defaulted) mech_type,
   GSS_Init_sec_context()  determines that the double-TGT protocol
   should be employed for the specified target. GSS_Init_sec_context()
   returns GSS_S_CONTINUE_NEEDED major_status, and its returned
   output_token contains a request to the service for the service's TGT.
   (If a service TGT with suitably long remaining lifetime already
   exists in a cache, it may be usable, obviating the need for this
   step.) The client passes the output_token to the service.  Note: this
   scenario illustrates a different use for the GSS_S_CONTINUE_NEEDED



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   status return facility than for support of mutual authentication;
   note that both uses can coexist as successive operations within a
   single context establishment operation.

   The service passes the received token as the input_token argument to
   GSS_Accept_sec_context(),  which recognizes it as a request for TGT.
   (Note that current Kerberos V5 defines no intra-protocol mechanism to
   represent such a request.) GSS_Accept_sec_context() returns
   GSS_S_CONTINUE_NEEDED major_status and provides the service's TGT in
   its output_token. The service sends the output_token to the client.

   The client passes the received token as the input_token argument to a
   continuation of GSS_Init_sec_context(). GSS_Init_sec_context() caches
   the received service TGT and uses it as part of a service ticket
   request to the Kerberos authentication server, storing the returned
   service ticket and session key in conjunction with the context.
   GSS_Init_sec_context() builds a Kerberos-formatted authenticator, and
   returns it in output_token along with GSS_S_COMPLETE return
   major_status. The client sends the output_token to the service.

   Service passes the received token as the input_token argument to a
   continuation call to GSS_Accept_sec_context().
   GSS_Accept_sec_context()  verifies the authenticator, provides the
   service with the client's authenticated name, and returns
   major_status GSS_S_COMPLETE.

   GSS_GetMIC(),  GSS_VerifyMIC(), GSS_Wrap(), and GSS_Unwrap()  as
   above.

5.3:  X.509 Authentication Framework

   This example illustrates use of the GSS-API in conjunction with
   public-key mechanisms, consistent with the X.509 Directory
   Authentication Framework.

   The GSS_Acquire_cred() call establishes a credentials structure,
   making the client's private key accessible for use on behalf of the
   client.

   The client calls GSS_Init_sec_context(), which interrogates the
   Directory to acquire (and validate) a chain of public-key
   certificates, thereby collecting the public key of the service.  The
   certificate validation operation determines that suitable integrity
   checks were applied by trusted authorities and that those
   certificates have not expired. GSS_Init_sec_context() generates a
   secret key for use in per-message protection operations on the
   context, and enciphers that secret key under the service's public
   key.



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   The enciphered secret key, along with an authenticator quantity
   signed with the client's private key, is included in the output_token
   from GSS_Init_sec_context().  The output_token also carries a
   certification path, consisting of a certificate chain leading from
   the service to the client; a variant approach would defer this path
   resolution to be performed by the service instead of being asserted
   by the client. The client application sends the output_token to the
   service.

   The service passes the received token as the input_token argument to
   GSS_Accept_sec_context(). GSS_Accept_sec_context() validates the
   certification path, and as a result determines a certified binding
   between the client's distinguished name and the client's public key.
   Given that public key, GSS_Accept_sec_context() can process the
   input_token's authenticator quantity and verify that the client's
   private key was used to sign the input_token. At this point, the
   client is authenticated to the service. The service uses its private
   key to decipher the enciphered secret key provided to it for per-
   message protection operations on the context.

   The client calls GSS_GetMIC() or GSS_Wrap() on a data message, which
   causes per-message authentication, integrity, and (optional)
   confidentiality facilities to be applied to that message. The service
   uses the context's shared secret key to perform corresponding
   GSS_VerifyMIC()  and GSS_Unwrap() calls.

6:  Security Considerations

   This document specifies a service interface for security facilities
   and services; as such, security considerations are considered
   throughout the specification.  Nonetheless, it is appropriate to
   summarize certain specific points relevant to GSS-API implementors
   and calling applications.  Usage of the GSS-API interface does not in
   itself provide security services or assurance; instead, these
   attributes are dependent on the underlying mechanism(s) which support
   a GSS-API implementation.  Callers must be attentive to the requests
   made to GSS-API calls and to the status indicators returned by GSS-
   API, as these specify the security service characteristics which
   GSS-API will provide.  When the interprocess context transfer
   facility is used, appropriate local controls should be applied to
   constrain access to interprocess tokens and to the sensitive data
   which they contain.









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7:  Related Activities

   In order to implement the GSS-API atop existing, emerging, and future
   security mechanisms:

      object identifiers must be assigned to candidate GSS-API
      mechanisms and the name types which they support

      concrete data element formats and processing procedures must be
      defined for candidate mechanisms

   Calling applications must implement formatting conventions which will
   enable them to distinguish GSS-API tokens from other data carried in
   their application protocols.

   Concrete language bindings are required for the programming
   environments in which the GSS-API is to be employed, as [RFC-1509]
   defines for the C programming language and GSS-V1.  C Language
   bindings for GSS-V2 are defined in [RFC-2744].
































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8:  Referenced Documents

   [ISO-7498-2]  International Standard ISO 7498-2-1988(E), Security
                 Architecture.

   [ISOIEC-8824] ISO/IEC 8824, "Specification of Abstract Syntax
                 Notation One (ASN.1)".

   [ISOIEC-8825] ISO/IEC 8825, "Specification of Basic Encoding Rules
                 for Abstract Syntax Notation One (ASN.1)".)

   [RFC-1507]:   Kaufman, C., "DASS: Distributed Authentication Security
                 Service", RFC 1507, September 1993.

   [RFC-1508]:   Linn, J., "Generic Security Service Application Program
                 Interface", RFC 1508, September 1993.

   [RFC-1509]:   Wray, J., "Generic Security Service API: C-bindings",
                 RFC 1509, September 1993.

   [RFC-1964]:   Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
                 RFC 1964, June 1996.

   [RFC-2025]:   Adams, C., "The Simple Public-Key GSS-API Mechanism
                 (SPKM)", RFC 2025, October 1996.

   [RFC-2078]:   Linn, J., "Generic Security Service Application Program
                 Interface, Version 2", RFC 2078, January 1997.

   [RFC-2203]:   Eisler, M., Chiu, A. and L. Ling, "RPCSEC_GSS Protocol
                 Specification", RFC 2203, September 1997.

   [RFC-2744]:   Wray, J., "Generic Security Service API Version 2 :
                 C-bindings", RFC 2744, January 2000.

















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APPENDIX A

MECHANISM DESIGN CONSTRAINTS

   The following constraints on GSS-API mechanism designs are adopted in
   response to observed caller protocol requirements, and adherence
   thereto is anticipated in subsequent descriptions of GSS-API
   mechanisms to be documented in standards-track Internet
   specifications.

   It is strongly recommended that mechanisms offering per-message
   protection services also offer at least one of the replay detection
   and sequencing services, as mechanisms offering neither of the latter
   will fail to satisfy recognized requirements of certain candidate
   caller protocols.

APPENDIX B

COMPATIBILITY WITH GSS-V1

   It is the intent of this document to define an interface and
   procedures which preserve compatibility between GSS-V1 [RFC-1508]
   callers and GSS-V2 providers.  All calls defined in GSS-V1 are
   preserved, and it has been a goal that GSS-V1 callers should be able
   to operate atop GSS-V2 provider implementations.  Certain detailed
   changes, summarized in this section, have been made in order to
   resolve omissions identified in GSS-V1.

   The following GSS-V1 constructs, while supported within GSS-V2, are
   deprecated:

      Names for per-message processing routines: GSS_Seal() deprecated
      in favor of GSS_Wrap(); GSS_Sign() deprecated in favor of
      GSS_GetMIC(); GSS_Unseal() deprecated in favor of GSS_Unwrap();
      GSS_Verify() deprecated in favor of GSS_VerifyMIC().

      GSS_Delete_sec_context() facility for context_token usage,
      allowing mechanisms to signal context deletion, is retained for
      compatibility with GSS-V1.  For current usage, it is recommended
      that both peers to a context invoke GSS_Delete_sec_context()
      independently, passing a null output_context_token buffer to
      indicate that no context_token is required.  Implementations of
      GSS_Delete_sec_context() should delete relevant locally-stored
      context information.

   This GSS-V2 specification adds the following calls which are not
   present in GSS-V1:




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      Credential management calls: GSS_Add_cred(),
      GSS_Inquire_cred_by_mech().

      Context-level calls: GSS_Inquire_context(), GSS_Wrap_size_limit(),
      GSS_Export_sec_context(), GSS_Import_sec_context().

      Per-message calls: No new calls.  Existing calls have been
      renamed.

      Support calls: GSS_Create_empty_OID_set(),
      GSS_Add_OID_set_member(), GSS_Test_OID_set_member(),
      GSS_Inquire_names_for_mech(), GSS_Inquire_mechs_for_name(),
      GSS_Canonicalize_name(), GSS_Export_name(), GSS_Duplicate_name().

   This GSS-V2 specification introduces three new facilities applicable
   to security contexts, indicated using the following context state
   values which are not present in GSS-V1:

      anon_state, set TRUE to indicate that a context's initiator is
      anonymous from the viewpoint of the target; Section 1.2.5 of this
      specification provides a summary description of the GSS-V2
      anonymity support facility, support and use of which is optional.

      prot_ready_state, set TRUE to indicate that a context may be used
      for per-message protection before final completion of context
      establishment; Section 1.2.7 of this specification provides a
      summary description of the GSS-V2 facility enabling mechanisms to
      selectively permit per-message protection during context
      establishment, support and use of which is optional.

      trans_state, set TRUE to indicate that a context is transferable
      to another process using the GSS-V2 GSS_Export_sec_context()
      facility.

   These state values are represented (at the C bindings level) in
   positions within a bit vector which are unused in GSS-V1, and may be
   safely ignored by GSS-V1 callers.

   New conf_req_flag and integ_req_flag inputs are defined for
   GSS_Init_sec_context(), primarily to provide information to
   negotiating mechanisms.  This introduces a compatibility issue with
   GSS-V1 callers, discussed in section 2.2.1 of this specification.









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   Relative to GSS-V1, GSS-V2 provides additional guidance to GSS-API
   implementors in the following areas: implementation robustness,
   credential management, behavior in multi-mechanism configurations,
   naming support, and inclusion of optional sequencing services.  The
   token tagging facility as defined in GSS-V2, Section 3.1, is now
   described directly in terms of octets to facilitate interoperable
   implementation without general ASN.1 processing code; the
   corresponding ASN.1 syntax, included for descriptive purposes, is
   unchanged from that in GSS-V1. For use in conjunction with added
   naming support facilities, a new Exported Name Object construct is
   added.  Additional name types are introduced in Section 4.

   This GSS-V2 specification adds the following major_status values
   which are not defined in GSS-V1:

        GSS_S_BAD_QOP                 unsupported QOP value
        GSS_S_UNAUTHORIZED            operation unauthorized
        GSS_S_UNAVAILABLE             operation unavailable
        GSS_S_DUPLICATE_ELEMENT       duplicate credential element
                                        requested
        GSS_S_NAME_NOT_MN                   name contains multi-mechanism
                                        elements
        GSS_S_GAP_TOKEN               skipped predecessor token(s)
                                        detected

   Of these added status codes, only two values are defined to be
   returnable by calls existing in GSS-V1: GSS_S_BAD_QOP (returnable by
   GSS_GetMIC() and GSS_Wrap()), and GSS_S_GAP_TOKEN (returnable by
   GSS_VerifyMIC() and GSS_Unwrap()).

   Additionally, GSS-V2 descriptions of certain calls present in GSS-V1
   have been updated to allow return of additional major_status values
   from the set as defined in GSS-V1: GSS_Inquire_cred() has
   GSS_S_DEFECTIVE_CREDENTIAL and GSS_S_CREDENTIALS_EXPIRED defined as
   returnable, GSS_Init_sec_context() has GSS_S_OLD_TOKEN,
   GSS_S_DUPLICATE_TOKEN, and GSS_S_BAD_MECH defined as returnable, and
   GSS_Accept_sec_context() has GSS_S_BAD_MECH defined as returnable.

APPENDIX C

CHANGES RELATIVE TO RFC-2078

   This document incorporates a number of changes relative to RFC-2078,
   made primarily in response to implementation experience, for purposes
   of alignment with the GSS-V2 C language bindings document, and to add
   informative clarification.  This section summarizes technical changes
   incorporated.




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   General:

      Clarified usage of object release routines, and incorporated
      statement that some may be omitted within certain operating
      environments.

      Removed GSS_Release_OID, GSS_OID_to_str(), and GSS_Str_to_OID()
      routines.

      Clarified circumstances under which zero-length tokens may validly
      exist as inputs and outputs to/from GSS-API calls.

      Added GSS_S_BAD_MIC status code as alias for GSS_S_BAD_SIG.

      For GSS_Display_status(), deferred to language bindings the choice
      of whether to return multiple status values in parallel or via
      iteration, and added commentary deprecating return of
      GSS_S_CONTINUE_NEEDED.

      Adapted and incorporated clarifying material on optional service
      support, delegation, and interprocess context transfer from C
      bindings document.

      Added and updated references to related documents, and to current
      status of cited Kerberos mechanism OID.

      Added general statement about GSS-API calls having no side effects
      visible at the GSS-API level.

   Context-related (including per-message protection issues):

      Clarified GSS_Delete_sec_context() usage for partially-established
      contexts.

      Added clarification on GSS_Export_sec_context() and
      GSS_Import_sec_context() behavior and context usage following an
      export-import sequence.

      Added informatory conf_req_flag, integ_req_flag inputs to
      GSS_Init_sec_context().  (Note: this facility introduces a
      backward incompatibility with GSS-V1 callers, discussed in Section
      2.2.1; this implication was recognized and accepted in working
      group discussion.)

      Stated that GSS_S_FAILURE is to be returned if
      GSS_Init_sec_context() or GSS_Accept_sec_context() is passed the
      handle of a context which is already fully established.




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      Re GSS_Inquire_sec_context(), stated that src_name and targ_name
      are not returned until GSS_S_COMPLETE status is reached; removed
      use of GSS_S_CONTEXT_EXPIRED status code (replacing with EXPIRED
      lifetime return value); stated requirement to retain inquirable
      data until context released by caller; added result value
      indicating whether or not context is fully open.

      Added discussion of interoperability conditions for mechanisms
      permitting optional support of QOPs. Removed reference to
      structured QOP elements in GSS_Verify_MIC().

      Added discussion of use of GSS_S_DUPLICATE_TOKEN status to
      indicate reflected per-message tokens.

      Clarified use of informational sequencing codes from per-message
      protection calls in conjunction with GSS_S_COMPLETE and
      GSS_S_FAILURE major_status returns, adjusting status code
      descriptions accordingly.

      Added specific statements about impact of GSS_GetMIC() and
      GSS_Wrap() failures on context state information, and generalized
      existing statements about impact of processing failures on
      received per-message tokens.

      For GSS_Init_sec_context() and GSS_Accept_sec_context(), permitted
      returned mech_type to be valid before GSS_S_COMPLETE, recognizing
      that the value may change on successive continuation calls in the
      negotiated mechanism case.

      Deleted GSS_S_CONTEXT_EXPIRED status from
      GSS_Import_sec_context().

      Added conf_req_flag input to GSS_Wrap_size_limit().

      Stated requirement for mechanisms' support of per-message
      protection services to be usable concurrently in both directions
      on a context.

   Credential-related:

      For GSS_Acquire_cred() and GSS_Add_cred(), aligned with C bindings
      statement of likely non-support for INITIATE or BOTH credentials
      if input name is neither empty nor a name resulting from applying
      GSS_Inquire_cred() against the default credential.  Further,
      stated that an explicit name returned by GSS_Inquire_context()
      should also be accepted.  Added commentary about potentially
      time-variant results of default resolution and attendant
      implications.  Aligned with C bindings re behavior when



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      GSS_C_NO_NAME provided for desired_name. In GSS_Acquire_cred(),
      stated that NULL, rather than empty OID set, should be used for
      desired_mechs in order to request default mechanism set.

      Added GSS_S_CREDENTIALS_EXPIRED as returnable major_status for
      GSS_Acquire_cred(), GSS_Add_cred(), also specifying GSS_S_NO_CRED
      as appropriate return for temporary, user-fixable credential
      unavailability.  GSS_Acquire_cred() and GSS_Add_cred() are also to
      return GSS_S_NO_CRED if an authorization failure is encountered
      upon credential acquisition.

      Removed GSS_S_CREDENTIALS_EXPIRED status return from per-message
      protection, GSS_Context_time(), and GSS_Inquire_context() calls.

      For GSS_Add_cred(), aligned with C bindings' description of
      behavior when addition of elements to the default credential is
      requested.

      Upgraded recommended default credential resolution algorithm to
      status of requirement for initiator credentials.

      For GSS_Release_cred(), GSS_Inquire_cred(), and
      GSS_Inquire_cred_by_mech(), clarified behavior for input
      GSS_C_NO_CREDENTIAL.

   Name-related:

      Aligned GSS_Inquire_mechs_for_name() description with C bindings.

      Removed GSS_S_BAD_NAMETYPE status return from
      GSS_Duplicate_name(), GSS_Display_name(); constrained its
      applicability for GSS_Compare_name().

      Aligned with C bindings statement re GSS_Import_name() behavior
      with GSS_C_NO_OID input name type, and stated that GSS-V2
      mechanism specifications are to define processing procedures
      applicable to their mechanisms.  Also clarified GSS_C_NO_OID usage
      with GSS_Display_name().

      Downgraded reference to name canonicalization via DNS lookup to an
      example.

      For GSS_Canonicalize_name(), stated that neither negotiated
      mechanisms nor the default mechanism are supported input
      mech_types for this operation, and specified GSS_S_BAD_MECH status
      to be returned in this case.  Clarified that the
      GSS_Canonicalize_name() operation is non-destructive to its input
      name.



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      Clarified semantics of GSS_C_NT_USER_NAME name type.

      Added descriptions of additional name types.  Also added
      discussion of GSS_C_NO_NAME and its constrained usage with
      specific GSS calls.

      Adapted and incorporated C bindings discussion about name
      comparisons with exported name objects.

      Added recommendation to mechanism designers for support of host-
      based service name type, deferring any requirement statement to
      individual mechanism specifications.  Added discussion of host-
      based service's service name element and proposed approach for
      IANA registration policy therefor.

      Clarified byte ordering within exported name object.  Stated that
      GSS_S_BAD_MECH is to be returned if, in the course of attempted
      import of an exported name object, the name object's enclosed
      mechanism type is unrecognized or unsupported.

      Stated that mechanisms may optionally accept GSS_C_NO_NAME as an
      input target name to GSS_Init_sec_context(), with comment that
      such support is unlikely within mechanisms predating GSS-V2,
      Update 1.

AUTHOR'S ADDRESS

   John Linn
   RSA Laboratories
   20 Crosby Drive
   Bedford, MA  01730 USA

   Phone: +1 781.687.7817
   EMail: jlinn@rsasecurity.com

















Linn                        Standards Track                   [Page 100]

RFC 2743                        GSS-API                     January 2000


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Linn                        Standards Track                   [Page 101]