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<pre>Internet Engineering Task Force (IETF) B. Campbell
Request for Comments: 7522 Ping Identity
Category: Standards Track C. Mortimore
ISSN: 2070-1721 Salesforce
M. Jones
Microsoft
May 2015
<span class="h1">Security Assertion Markup Language (SAML) 2.0 Profile</span>
<span class="h1">for OAuth 2.0 Client Authentication and Authorization Grants</span>
Abstract
This specification defines the use of a Security Assertion Markup
Language (SAML) 2.0 Bearer Assertion as a means for requesting an
OAuth 2.0 access token as well as for client authentication.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in <a href="./rfc5741#section-2">Section 2 of RFC 5741</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="http://www.rfc-editor.org/info/rfc7522">http://www.rfc-editor.org/info/rfc7522</a>.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
<span class="grey">Campbell, et al. Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc7522">RFC 7522</a> OAuth SAML Assertion Profiles May 2015</span>
Table of Contents
<a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-2">2</a>
<a href="#section-1.1">1.1</a>. Notational Conventions . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-1.2">1.2</a>. Terminology . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-2">2</a>. HTTP Parameter Bindings for Transporting Assertions . . . . . <a href="#page-4">4</a>
<a href="#section-2.1">2.1</a>. Using SAML Assertions as Authorization Grants . . . . . . <a href="#page-4">4</a>
<a href="#section-2.2">2.2</a>. Using SAML Assertions for Client Authentication . . . . . <a href="#page-5">5</a>
<a href="#section-3">3</a>. Assertion Format and Processing Requirements . . . . . . . . <a href="#page-6">6</a>
<a href="#section-3.1">3.1</a>. Authorization Grant Processing . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-3.2">3.2</a>. Client Authentication Processing . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-4">4</a>. Authorization Grant Example . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5">5</a>. Interoperability Considerations . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6">6</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-7">7</a>. Privacy Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-8">8</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
8.1. Sub-Namespace Registration of
urn:ietf:params:oauth:grant-type:saml2-bearer . . . . . . <a href="#page-12">12</a>
8.2. Sub-Namespace Registration of
urn:ietf:params:oauth:client-assertion-type:saml2-bearer 13
<a href="#section-9">9</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-9.1">9.1</a>. Normative References . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-9.2">9.2</a>. Informative References . . . . . . . . . . . . . . . . . <a href="#page-14">14</a>
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-15">15</a>
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-15">15</a>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
The Security Assertion Markup Language (SAML) 2.0
[<a href="#ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>] is an XML-based framework that allows
identity and security information to be shared across security
domains. The SAML specification, while primarily targeted at
providing cross domain Web browser single sign-on (SSO), was also
designed to be modular and extensible to facilitate use in other
contexts.
The Assertion, an XML security token, is a fundamental construct of
SAML that is often adopted for use in other protocols and
specifications. (Some examples include [<a href="#ref-OASIS.WSS-SAMLTokenProfile">OASIS.WSS-SAMLTokenProfile</a>]
and [<a href="#ref-OASIS.WS-Fed">OASIS.WS-Fed</a>].) An Assertion is generally issued by an Identity
Provider and consumed by a Service Provider that relies on its
content to identify the Assertion's subject for security-related
purposes.
The OAuth 2.0 Authorization Framework [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>] provides a method for
making authenticated HTTP requests to a resource using an access
token. Access tokens are issued to third-party clients by an
authorization server (AS) with the (sometimes implicit) approval of
<span class="grey">Campbell, et al. Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc7522">RFC 7522</a> OAuth SAML Assertion Profiles May 2015</span>
the resource owner. In OAuth, an authorization grant is an abstract
term used to describe intermediate credentials that represent the
resource owner authorization. An authorization grant is used by the
client to obtain an access token. Several authorization grant types
are defined to support a wide range of client types and user
experiences. OAuth also allows for the definition of new extension
grant types to support additional clients or to provide a bridge
between OAuth and other trust frameworks. Finally, OAuth allows the
definition of additional authentication mechanisms to be used by
clients when interacting with the authorization server.
"Assertion Framework for OAuth 2.0 Client Authentication and
Authorization Grants" [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>] is an abstract extension to OAuth 2.0
that provides a general framework for the use of assertions as client
credentials and/or authorization grants with OAuth 2.0. This
specification profiles the OAuth Assertion Framework [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>] to
define an extension grant type that uses a SAML 2.0 Bearer Assertion
to request an OAuth 2.0 access token as well as for use as client
credentials. The format and processing rules for the SAML Assertion
defined in this specification are intentionally similar, though not
identical, to those in the Web Browser SSO profile defined in the
SAML Profiles [<a href="#ref-OASIS.saml-profiles-2.0-os">OASIS.saml-profiles-2.0-os</a>] specification. This
specification is reusing, to the extent reasonable, concepts and
patterns from that well-established profile.
This document defines how a SAML Assertion can be used to request an
access token when a client wishes to utilize an existing trust
relationship, expressed through the semantics of the SAML Assertion,
without a direct user approval step at the authorization server. It
also defines how a SAML Assertion can be used as a client
authentication mechanism. The use of an Assertion for client
authentication is orthogonal to and separable from using an Assertion
as an authorization grant. They can be used either in combination or
separately. Client assertion authentication is nothing more than an
alternative way for a client to authenticate to the token endpoint,
and it must be used in conjunction with some grant type to form a
complete and meaningful protocol request. Assertion authorization
grants may be used with or without client authentication or
identification. Whether or not client authentication is needed in
conjunction with an assertion authorization grant, as well as the
supported types of client authentication, are policy decisions at the
discretion of the authorization server.
The process by which the client obtains the SAML Assertion, prior to
exchanging it with the authorization server or using it for client
authentication, is out of scope.
<span class="grey">Campbell, et al. Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc7522">RFC 7522</a> OAuth SAML Assertion Profiles May 2015</span>
<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>. Notational Conventions</span>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <a href="./rfc2119">RFC 2119</a> [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a>. Terminology</span>
All terms are as defined in the following specifications: "The OAuth
2.0 Authorization Framework" [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>], the OAuth Assertion Framework
[<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>], and "Assertions and Protocols for the OASIS Security
Assertion Markup Language (SAML) V2.0" [<a href="#ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>].
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. HTTP Parameter Bindings for Transporting Assertions</span>
The OAuth Assertion Framework [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>] defines generic HTTP
parameters for transporting assertions during interactions with a
token endpoint. This section defines specific parameters and
treatments of those parameters for use with SAML 2.0 Bearer
Assertions.
<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>. Using SAML Assertions as Authorization Grants</span>
To use a SAML Bearer Assertion as an authorization grant, the client
uses an access token request as defined in <a href="#section-4">Section 4</a> of the OAuth
Assertion Framework [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>] with the following specific parameter
values and encodings.
The value of the "grant_type" parameter is
"urn:ietf:params:oauth:grant-type:saml2-bearer".
The value of the "assertion" parameter contains a single SAML 2.0
Assertion. It MUST NOT contain more than one SAML 2.0 Assertion.
The SAML Assertion XML data MUST be encoded using base64url, where
the encoding adheres to the definition in <a href="./rfc4648#section-5">Section 5 of RFC 4648</a>
[<a href="./rfc4648" title=""The Base16, Base32, and Base64 Data Encodings"">RFC4648</a>] and where the padding bits are set to zero. To avoid the
need for subsequent encoding steps (by "application/x-www-form-
urlencoded" [<a href="#ref-W3C.REC-html401-19991224">W3C.REC-html401-19991224</a>], for example), the base64url-
encoded data MUST NOT be line wrapped and pad characters ("=") MUST
NOT be included.
The "scope" parameter may be used, as defined in the OAuth Assertion
Framework [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>], to indicate the requested scope.
<span class="grey">Campbell, et al. Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc7522">RFC 7522</a> OAuth SAML Assertion Profiles May 2015</span>
Authentication of the client is optional, as described in
<a href="#section-3.2.1">Section 3.2.1</a> of OAuth 2.0 [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>] and consequently, the
"client_id" is only needed when a form of client authentication that
relies on the parameter is used.
The following example demonstrates an access token request with an
Assertion as an authorization grant (with extra line breaks for
display purposes only):
POST /token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Asaml2-bearer&
assertion=PHNhbWxwOl...[omitted for brevity]...ZT4
<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>. Using SAML Assertions for Client Authentication</span>
To use a SAML Bearer Assertion for client authentication, the client
uses the following parameter values and encodings.
The value of the "client_assertion_type" parameter is
"urn:ietf:params:oauth:client-assertion-type:saml2-bearer".
The value of the "client_assertion" parameter MUST contain a single
SAML 2.0 Assertion. The SAML Assertion XML data MUST be encoded
using base64url, where the encoding adheres to the definition in
<a href="./rfc4648#section-5">Section 5 of RFC 4648</a> [<a href="./rfc4648" title=""The Base16, Base32, and Base64 Data Encodings"">RFC4648</a>] and where the padding bits are set to
zero. To avoid the need for subsequent encoding steps (by
"application/x-www-form-urlencoded" [<a href="#ref-W3C.REC-html401-19991224">W3C.REC-html401-19991224</a>], for
example), the base64url-encoded data SHOULD NOT be line wrapped and
pad characters ("=") SHOULD NOT be included.
The following example demonstrates a client authenticating using an
Assertion during the presentation of an authorization code grant in
an access token request (with extra line breaks for display purposes
only):
POST /token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&
code=n0esc3NRze7LTCu7iYzS6a5acc3f0ogp4&
client_assertion_type=urn%3Aietf%3Aparams%3Aoauth
%3Aclient-assertion-type%3Asaml2-bearer&
client_assertion=PHNhbW...[omitted for brevity]...ZT
<span class="grey">Campbell, et al. Standards Track [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc7522">RFC 7522</a> OAuth SAML Assertion Profiles May 2015</span>
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Assertion Format and Processing Requirements</span>
In order to issue an access token response as described in OAuth 2.0
[<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>] or to rely on an Assertion for client authentication, the
authorization server MUST validate the Assertion according to the
criteria below. Application of additional restrictions and policy
are at the discretion of the authorization server.
1. The Assertion's <Issuer> element MUST contain a unique
identifier for the entity that issued the Assertion. In the
absence of an application profile specifying otherwise,
compliant applications MUST compare Issuer values using the
Simple String Comparison method defined in Section 6.2.1 of <a href="./rfc3986">RFC</a>
<a href="./rfc3986">3986</a> [<a href="./rfc3986" title=""Uniform Resource Identifier (URI): Generic Syntax"">RFC3986</a>].
2. The Assertion MUST contain a <Conditions> element with an
<AudienceRestriction> element with an <Audience> element that
identifies the authorization server as an intended audience.
<a href="#section-2.5.1.4">Section 2.5.1.4</a> of "Assertions and Protocols for the OASIS
Security Assertion Markup Language (SAML) V2.0"
[<a href="#ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>] defines the <AudienceRestriction> and
<Audience> elements and, in addition to the URI references
discussed there, the token endpoint URL of the authorization
server MAY be used as a URI that identifies the authorization
server as an intended audience. The authorization server MUST
reject any Assertion that does not contain its own identity as
the intended audience. In the absence of an application profile
specifying otherwise, compliant applications MUST compare the
Audience values using the Simple String Comparison method
defined in <a href="./rfc3986#section-6.2.1">Section 6.2.1 of RFC 3986</a> [<a href="./rfc3986" title=""Uniform Resource Identifier (URI): Generic Syntax"">RFC3986</a>]. As noted in
<a href="#section-5">Section 5</a>, the precise strings to be used as the Audience for a
given authorization server must be configured out of band by the
authorization server and the issuer of the Assertion.
3. The Assertion MUST contain a <Subject> element identifying the
principal that is the subject of the Assertion. Additional
information identifying the subject/principal MAY be included in
an <AttributeStatement>.
A. For the authorization grant, the Subject typically
identifies an authorized accessor for which the access token
is being requested (i.e., the resource owner or an
authorized delegate), but in some cases, it may be a
pseudonymous identifier or other value denoting an anonymous
user.
B. For client authentication, the Subject MUST be the
"client_id" of the OAuth client.
<span class="grey">Campbell, et al. Standards Track [Page 6]</span></pre>
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4. The Assertion MUST have an expiry that limits the time window
during which it can be used. The expiry can be expressed either
as the NotOnOrAfter attribute of the <Conditions> element or as
the NotOnOrAfter attribute of a suitable
<SubjectConfirmationData> element.
5. The <Subject> element MUST contain at least one
<SubjectConfirmation> element that has a Method attribute with a
value of "urn:oasis:names:tc:SAML:2.0:cm:bearer". If the
Assertion does not have a suitable NotOnOrAfter attribute on the
<Conditions> element, the <SubjectConfirmation> element MUST
contain a <SubjectConfirmationData> element. When present, the
<SubjectConfirmationData> element MUST have a Recipient
attribute with a value indicating the token endpoint URL of the
authorization server (or an acceptable alias). The
authorization server MUST verify that the value of the Recipient
attribute matches the token endpoint URL (or an acceptable
alias) to which the Assertion was delivered. The
<SubjectConfirmationData> element MUST have a NotOnOrAfter
attribute that limits the window during which the Assertion can
be confirmed. The <SubjectConfirmationData> element MAY also
contain an Address attribute limiting the client address from
which the Assertion can be delivered. Verification of the
Address is at the discretion of the authorization server.
6. The authorization server MUST reject the entire Assertion if the
NotOnOrAfter instant on the <Conditions> element has passed
(subject to allowable clock skew between systems). The
authorization server MUST reject the <SubjectConfirmation> (but
MAY still use the rest of the Assertion) if the NotOnOrAfter
instant on the <SubjectConfirmationData> has passed (subject to
allowable clock skew). Note that the authorization server may
reject Assertions with a NotOnOrAfter instant that is
unreasonably far in the future. The authorization server MAY
ensure that Bearer Assertions are not replayed, by maintaining
the set of used ID values for the length of time for which the
Assertion would be considered valid based on the applicable
NotOnOrAfter instant.
7. If the Assertion issuer directly authenticated the subject, the
Assertion SHOULD contain a single <AuthnStatement> representing
that authentication event. If the Assertion was issued with the
intention that the client act autonomously on behalf of the
subject, an <AuthnStatement> SHOULD NOT be included and the
client presenting the Assertion SHOULD be identified in the
<NameID> or similar element in the <SubjectConfirmation>
element, or by other available means like "SAML V2.0 Condition
for Delegation Restriction" [<a href="#ref-OASIS.saml-deleg-cs">OASIS.saml-deleg-cs</a>].
<span class="grey">Campbell, et al. Standards Track [Page 7]</span></pre>
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8. Other statements, in particular <AttributeStatement> elements,
MAY be included in the Assertion.
9. The Assertion MUST be digitally signed or have a Message
Authentication Code (MAC) applied by the issuer. The
authorization server MUST reject Assertions with an invalid
signature or MAC.
10. Encrypted elements MAY appear in place of their plaintext
counterparts as defined in [<a href="#ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>].
11. The authorization server MUST reject an Assertion that is not
valid in all other respects per [<a href="#ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>], such
as (but not limited to) all content within the Conditions
element including the NotOnOrAfter and NotBefore attributes,
unknown condition types, etc.
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Authorization Grant Processing</span>
Assertion authorization grants may be used with or without client
authentication or identification. Whether or not client
authentication is needed in conjunction with an Assertion
authorization grant, as well as the supported types of client
authentication, are policy decisions at the discretion of the
authorization server. However, if client credentials are present in
the request, the authorization server MUST validate them.
If the Assertion is not valid (including if its subject confirmation
requirements cannot be met), the authorization server constructs an
error response as defined in OAuth 2.0 [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>]. The value of the
"error" parameter MUST be the "invalid_grant" error code. The
authorization server MAY include additional information regarding the
reasons the Assertion was considered invalid using the
"error_description" or "error_uri" parameters.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_grant",
"error_description":"Audience validation failed"
}
<span class="grey">Campbell, et al. Standards Track [Page 8]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-9" ></span>
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<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Client Authentication Processing</span>
If the client Assertion is not valid (including if its subject
confirmation requirements cannot be met), the authorization server
constructs an error response as defined in OAuth 2.0 [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>]. The
value of the "error" parameter MUST be the "invalid_client" error
code. The authorization server MAY include additional information
regarding the reasons the Assertion was considered invalid using the
"error_description" or "error_uri" parameters.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Authorization Grant Example</span>
The following examples illustrate what a conforming Assertion and an
access token request would look like.
The example shows an assertion issued and signed by the SAML Identity
Provider identified as "https://saml-idp.example.com". The subject
of the Assertion is identified by email address as
"brian@example.com", who authenticated to the Identity Provider by
means of a digital signature where the key was validated as part of
an X.509 Public Key Infrastructure. The intended audience of the
Assertion is "https://saml-sp.example.net", which is an identifier
for a SAML Service Provider with which the authorization server
identifies itself. The Assertion is sent as part of an access token
request to the authorization server's token endpoint at
"https://authz.example.net/token.oauth2".
<span class="grey">Campbell, et al. Standards Track [Page 9]</span></pre>
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Below is an example SAML 2.0 Assertion (whitespace formatting is for
display purposes only):
<Assertion IssueInstant="2010-10-01T20:07:34.619Z"
ID="ef1xsbZxPV2oqjd7HTLRLIBlBb7"
Version="2.0"
xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
<Issuer>https://saml-idp.example.com</Issuer>
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
[...omitted for brevity...]
</ds:Signature>
<Subject>
<NameID
Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">
brian@example.com
</NameID>
<SubjectConfirmation
Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
<SubjectConfirmationData
NotOnOrAfter="2010-10-01T20:12:34.619Z"
Recipient="https://authz.example.net/token.oauth2"/>
</SubjectConfirmation>
</Subject>
<Conditions>
<AudienceRestriction>
<Audience>https://saml-sp.example.net</Audience>
</AudienceRestriction>
</Conditions>
<AuthnStatement AuthnInstant="2010-10-01T20:07:34.371Z">
<AuthnContext>
<AuthnContextClassRef>
urn:oasis:names:tc:SAML:2.0:ac:classes:X509
</AuthnContextClassRef>
</AuthnContext>
</AuthnStatement>
</Assertion>
Figure 1: Example SAML 2.0 Assertion
<span class="grey">Campbell, et al. Standards Track [Page 10]</span></pre>
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To present the Assertion shown in the previous example as part of an
access token request, for example, the client might make the
following HTTPS request (with extra line breaks for display purposes
only):
POST /token.oauth2 HTTP/1.1
Host: authz.example.net
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Asaml2-
bearer&assertion=PEFzc2VydGlvbiBJc3N1ZUluc3RhbnQ9IjIwMTEtMDU
[...omitted for brevity...]aG5TdGF0ZW1lbnQ-PC9Bc3NlcnRpb24-
Figure 2: Example Request
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Interoperability Considerations</span>
Agreement between system entities regarding identifiers, keys, and
endpoints is required in order to achieve interoperable deployments
of this profile. Specific items that require agreement are as
follows: values for the Issuer and Audience identifiers, the location
of the token endpoint, the key used to apply and verify the digital
signature over the Assertion, one-time use restrictions on
Assertions, maximum Assertion lifetime allowed, and the specific
Subject and attribute requirements of the Assertion. The exchange of
such information is explicitly out of scope for this specification,
and typical deployment of it will be done alongside existing SAML Web
SSO deployments that have already established a means of exchanging
such information. "Metadata for the OASIS Security Assertion Markup
Language (SAML) V2.0" [<a href="#ref-OASIS.saml-metadata-2.0-os">OASIS.saml-metadata-2.0-os</a>] specifies one
common method of exchanging SAML-related information about system
entities.
The RSA-SHA256 algorithm, from [<a href="./rfc6931" title=""Additional XML Security Uniform Resource Identifiers (URIs)"">RFC6931</a>], is a mandatory-to-implement
XML signature algorithm for this profile.
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Security Considerations</span>
The security considerations described within the following
specifications are all applicable to this document: "Assertion
Framework for OAuth 2.0 Client Authentication and Authorization
Grants" [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>], "The OAuth 2.0 Authorization Framework" [<a href="./rfc6749" title=""The OAuth 2.0 Authorization Framework"">RFC6749</a>],
and "Security and Privacy Considerations for the OASIS Security
Assertion Markup Language (SAML) V2.0"
[<a href="#ref-OASIS.saml-sec-consider-2.0-os">OASIS.saml-sec-consider-2.0-os</a>].
<span class="grey">Campbell, et al. Standards Track [Page 11]</span></pre>
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The specification does not mandate replay protection for the SAML
Assertion usage for either the authorization grant or for client
authentication. It is an optional feature, which implementations may
employ at their own discretion.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Privacy Considerations</span>
A SAML Assertion may contain privacy-sensitive information and, to
prevent disclosure of such information to unintended parties, should
only be transmitted over encrypted channels, such as Transport Layer
Security (TLS). In cases where it is desirable to prevent disclosure
of certain information to the client, the Subject and/or individual
attributes of a SAML Assertion should be encrypted to the
authorization server.
Deployments should determine the minimum amount of information
necessary to complete the exchange and include only that information
in an Assertion (typically by limiting what information is included
in an <AttributeStatement> or by omitting it altogether). In some
cases, the Subject can be a value representing an anonymous or
pseudonymous user, as described in <a href="#section-6.3.1">Section 6.3.1</a> of the OAuth
Assertion Framework [<a href="./rfc7521" title=""Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants"">RFC7521</a>].
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. IANA Considerations</span>
<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. Sub-Namespace Registration of</span>
<span class="h3"> urn:ietf:params:oauth:grant-type:saml2-bearer</span>
This section registers the value "grant-type:saml2-bearer" in the
IANA "OAuth URI" registry established by "An IETF URN Sub-Namespace
for OAuth" [<a href="./rfc6755" title=""An IETF URN Sub-Namespace for OAuth"">RFC6755</a>].
o URN: urn:ietf:params:oauth:grant-type:saml2-bearer
o Common Name: SAML 2.0 Bearer Assertion Grant Type Profile for
OAuth 2.0
o Change Controller: IESG
o Specification Document: <a href="./rfc7522">RFC 7522</a>
<span class="grey">Campbell, et al. Standards Track [Page 12]</span></pre>
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<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>. Sub-Namespace Registration of</span>
<span class="h3"> urn:ietf:params:oauth:client-assertion-type:saml2-bearer</span>
This section registers the value "client-assertion-type:saml2-bearer"
in the IANA "OAuth URI" registry established by "An IETF URN Sub-
Namespace for OAuth" [<a href="./rfc6755" title=""An IETF URN Sub-Namespace for OAuth"">RFC6755</a>].
o URN: urn:ietf:params:oauth:client-assertion-type:saml2-bearer
o Common Name: SAML 2.0 Bearer Assertion Profile for OAuth 2.0
Client Authentication
o Change Controller: IESG
o Specification Document: <a href="./rfc7522">RFC 7522</a>
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. References</span>
<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>. Normative References</span>
[<a id="ref-OASIS.saml-core-2.0-os">OASIS.saml-core-2.0-os</a>]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocols for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard
saml-core-2.0-os, March 2005, <<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-core-2.0-os.pdf">http://docs.oasis-open.org/</a>
<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-core-2.0-os.pdf">security/saml/v2.0/saml-core-2.0-os.pdf</a>>.
[<a id="ref-OASIS.saml-deleg-cs">OASIS.saml-deleg-cs</a>]
Cantor, S., Ed., "SAML V2.0 Condition for Delegation
Restriction Version 1", Committee Specification 01,
November 2009, <<a href="http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-delegation-cs-01.html">http://docs.oasis-open.org/</a>
<a href="http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-delegation-cs-01.html">security/saml/Post2.0/sstc-saml-delegation-cs-01.html</a>>.
[<a id="ref-OASIS.saml-sec-consider-2.0-os">OASIS.saml-sec-consider-2.0-os</a>]
Hirsch, F., Philpott, R., and E. Maler, "Security and
Privacy Considerations for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard
saml-sec-consider-2.0-os, March 2005,
<<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-sec-consider-2.0-os.pdf">http://docs.oasis-open.org/security/saml/v2.0/</a>
<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-sec-consider-2.0-os.pdf">saml-sec-consider-2.0-os.pdf</a>>.
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>,
DOI 10.17487/RFC2119, March 1997,
<<a href="http://www.rfc-editor.org/info/rfc2119">http://www.rfc-editor.org/info/rfc2119</a>>.
<span class="grey">Campbell, et al. Standards Track [Page 13]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-14" ></span>
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[<a id="ref-RFC3986">RFC3986</a>] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
<a href="./rfc3986">RFC 3986</a>, DOI 10.17487/RFC3986, January 2005,
<<a href="http://www.rfc-editor.org/info/rfc3986">http://www.rfc-editor.org/info/rfc3986</a>>.
[<a id="ref-RFC4648">RFC4648</a>] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", <a href="./rfc4648">RFC 4648</a>, DOI 10.17487/RFC4648, October 2006,
<<a href="http://www.rfc-editor.org/info/rfc4648">http://www.rfc-editor.org/info/rfc4648</a>>.
[<a id="ref-RFC6749">RFC6749</a>] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
<a href="./rfc6749">RFC 6749</a>, DOI 10.17487/RFC6749, October 2012,
<<a href="http://www.rfc-editor.org/info/rfc6749">http://www.rfc-editor.org/info/rfc6749</a>>.
[<a id="ref-RFC6931">RFC6931</a>] Eastlake 3rd, D., "Additional XML Security Uniform
Resource Identifiers (URIs)", <a href="./rfc6931">RFC 6931</a>,
DOI 10.17487/RFC6931, April 2013,
<<a href="http://www.rfc-editor.org/info/rfc6931">http://www.rfc-editor.org/info/rfc6931</a>>.
[<a id="ref-RFC7521">RFC7521</a>] Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
"Assertion Framework for OAuth 2.0 Client Authentication
and Authorization Grants", <a href="./rfc7521">RFC 7521</a>, DOI 10.17487/RFC7521,
May 2015, <<a href="http://www.rfc-editor.org/info/rfc7521">http://www.rfc-editor.org/info/rfc7521</a>>.
<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>. Informative References</span>
[<a id="ref-OASIS.WS-Fed">OASIS.WS-Fed</a>]
Goodner, M. and A. Nadalin, "Web Services Federation
Language (WS-Federation) Version 1.2", OASIS Standard, May
2009, <<a href="http://docs.oasis-open.org/wsfed/federation/v1.2/os/ws-federation-1.2-spec-os.html">http://docs.oasis-open.org/wsfed/</a>
<a href="http://docs.oasis-open.org/wsfed/federation/v1.2/os/ws-federation-1.2-spec-os.html">federation/v1.2/os/ws-federation-1.2-spec-os.html</a>>.
[<a id="ref-OASIS.WSS-SAMLTokenProfile">OASIS.WSS-SAMLTokenProfile</a>]
Monzillo, R., Kaler, C., Nadalin, T., Hallam-Baker, P.,
and C. Milono, "Web Services Security SAML Token Profile
Version 1.1.1", OASIS Standard, May 2012,
<<a href="http://docs.oasis-open.org/wss-m/wss/v1.1.1/wss-SAMLTokenProfile-v1.1.1.html">http://docs.oasis-open.org/wss-m/wss/v1.1.1/</a>
<a href="http://docs.oasis-open.org/wss-m/wss/v1.1.1/wss-SAMLTokenProfile-v1.1.1.html">wss-SAMLTokenProfile-v1.1.1.html</a>>.
[<a id="ref-OASIS.saml-metadata-2.0-os">OASIS.saml-metadata-2.0-os</a>]
Cantor, S., Moreh, J., Philpott, R., and E. Maler,
"Metadata for the OASIS Security Assertion Markup Language
(SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March
2005, <<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-metadata-2.0-os.pdf">http://docs.oasis-open.org/security/saml/v2.0/</a>
<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-metadata-2.0-os.pdf">saml-metadata-2.0-os.pdf</a>>.
<span class="grey">Campbell, et al. Standards Track [Page 14]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
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[<a id="ref-OASIS.saml-profiles-2.0-os">OASIS.saml-profiles-2.0-os</a>]
Hughes, J., Cantor, S., Hodges, J., Hirsch, F., Mishra,
P., Philpott, R., and E. Maler, "Profiles for the OASIS
Security Assertion Markup Language (SAML) V2.0", OASIS
Standard OASIS.saml-profiles-2.0-os, March 2005,
<<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-profiles-2.0-os.pdf">http://docs.oasis-open.org/security/saml/v2.0/</a>
<a href="http://docs.oasis-open.org/security/saml/v2.0/saml-profiles-2.0-os.pdf">saml-profiles-2.0-os.pdf</a>>.
[<a id="ref-RFC6755">RFC6755</a>] Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
for OAuth", <a href="./rfc6755">RFC 6755</a>, DOI 10.17487/RFC6755, October 2012,
<<a href="http://www.rfc-editor.org/info/rfc6755">http://www.rfc-editor.org/info/rfc6755</a>>.
[<a id="ref-W3C.REC-html401-19991224">W3C.REC-html401-19991224</a>]
Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01
Specification", World Wide Web Consortium Recommendation
REC-html401-19991224, December 1999,
<<a href="http://www.w3.org/TR/1999/REC-html401-19991224">http://www.w3.org/TR/1999/REC-html401-19991224</a>>.
Acknowledgements
The following people contributed wording and concepts to this
document: Paul Madsen, Patrick Harding, Peter Motykowski, Eran
Hammer, Peter Saint-Andre, Ian Barnett, Eric Fazendin, Torsten
Lodderstedt, Susan Harper, Scott Tomilson, Scott Cantor, Hannes
Tschofenig, David Waite, Phil Hunt, and Mukesh Bhatnagar.
Authors' Addresses
Brian Campbell
Ping Identity
EMail: brian.d.campbell@gmail.com
Chuck Mortimore
Salesforce.com
EMail: cmortimore@salesforce.com
Michael B. Jones
Microsoft
EMail: mbj@microsoft.com
URI: <a href="http://self-issued.info/">http://self-issued.info/</a>
Campbell, et al. Standards Track [Page 15]
</pre>
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