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<pre>Internet Engineering Task Force (IETF) S. Santesson
Request for Comments: 5816 3xA Security
Updates: <a href="./rfc3161">3161</a> N. Pope
Category: Standards Track Thales
ISSN: 2070-1721 March 2010
<span class="h1">ESSCertIDv2 Update for <a href="./rfc3161">RFC 3161</a></span>
Abstract
This document updates <a href="./rfc3161">RFC 3161</a>. It allows the use of ESSCertIDv2, as
defined in <a href="./rfc5035">RFC 5035</a>, to specify the hash of a signer certificate when
the hash is calculated with a function other than the Secure Hash
Algorithm (SHA-1).
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/rfc5816">http://www.rfc-editor.org/info/rfc5816</a>.
Copyright Notice
Copyright (c) 2010 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.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
<span class="grey">Santesson & Pope Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc5816">RFC 5816</a> ESSCertIDv2 Update for <a href="./rfc3161">RFC 3161</a> March 2010</span>
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-1.1">1.1</a>. Terminology ................................................<a href="#page-2">2</a>
<a href="#section-2">2</a>. Updates to <a href="./rfc3161">RFC 3161</a> .............................................<a href="#page-3">3</a>
<a href="#section-2.1">2.1</a>. Changes to <a href="#section-2.4.1">Section 2.4.1</a>, Request Format ...................<a href="#page-3">3</a>
<a href="#section-2.2">2.2</a>. Changes to <a href="#section-2.4.2">Section 2.4.2</a>, Response Format ..................<a href="#page-3">3</a>
<a href="#section-2.2.1">2.2.1</a>. Signature of Time-Stamp Token .......................<a href="#page-3">3</a>
<a href="#section-2.2.2">2.2.2</a>. Verifying the Time-Stamp Token ......................<a href="#page-4">4</a>
<a href="#section-3">3</a>. Security Considerations .........................................<a href="#page-4">4</a>
<a href="#section-4">4</a>. References ......................................................<a href="#page-5">5</a>
<a href="#section-4.1">4.1</a>. Normative References .......................................<a href="#page-5">5</a>
<a href="#section-4.2">4.2</a>. Informative References .....................................<a href="#page-5">5</a>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
The time-stamping protocol defined in <a href="./rfc3161">RFC 3161</a> [<a href="./rfc3161" title=""Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)"">RFC3161</a>] requires
that the Cryptographic Message Syntax (CMS) SignedData [<a href="./rfc5652" title=""Cryptographic Message Syntax (CMS)"">RFC5652</a>],
used to apply a digital signature on the time-stamp token, include a
signed attribute that identifies the signer's certificate.
This identifier only allows SHA-1 [<a href="#ref-SHA1">SHA1</a>] to be used as the hash
algorithm to generate the identifier value.
The mechanism used in [<a href="./rfc3161" title=""Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)"">RFC3161</a>] employed ESSCertID from <a href="./rfc2634">RFC 2634</a>
[<a href="#ref-ESS" title=""Enhanced Security Services for S/MIME"">ESS</a>]. <a href="./rfc5035">RFC 5035</a> [<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>] updated ESSCertID with ESSCertIDv2 to allow
the use of any hash algorithm.
The changes to <a href="./rfc3161">RFC 3161</a> [<a href="./rfc3161" title=""Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)"">RFC3161</a>] defined in this document allow
ESSCertIDv2 to be used to include an identifier of the signing
certificate as defined in <a href="./rfc5035">RFC 5035</a> [<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>].
<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>. Terminology</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>].
<span class="grey">Santesson & Pope Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc5816">RFC 5816</a> ESSCertIDv2 Update for <a href="./rfc3161">RFC 3161</a> March 2010</span>
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Updates to <a href="./rfc3161">RFC 3161</a></span>
<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>. Changes to <a href="#section-2.4.1">Section 2.4.1</a>, Request Format</span>
Last paragraph on Page 5.
Old:
If the certReq field is present and set to true, the TSA's public
key certificate that is referenced by the ESSCertID identifier
inside a SigningCertificate attribute in the response MUST be
provided by the TSA in the certificates field from the SignedData
structure in that response. That field may also contain other
certificates.
New:
If the certReq field is present and set to true, the TSA's public
key certificate that is referenced by the ESSCertID [<a href="#ref-ESS" title=""Enhanced Security Services for S/MIME"">ESS</a>] field
inside a SigningCertificate attribute or by the ESSCertIDv2
[<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>] field inside a SigningCertificateV2 attribute in the
response MUST be provided by the TSA in the certificates field
from the SignedData structure in that response. That field may
also contain other certificates.
<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>. Changes to <a href="#section-2.4.2">Section 2.4.2</a>, Response Format</span>
<span class="h4"><a class="selflink" id="section-2.2.1" href="#section-2.2.1">2.2.1</a>. Signature of Time-Stamp Token</span>
Fifth paragraph on Page 8, just before the definition of TSTInfo.
Old:
The time-stamp token MUST NOT contain any signatures other than
the signature of the TSA. The certificate identifier (ESSCertID)
of the TSA certificate MUST be included as a signerInfo attribute
inside a SigningCertificate attribute.
New:
The time-stamp token MUST NOT contain any signatures other than
the signature of the TSA. The certificate identifier (either
ESSCertID [<a href="#ref-ESS" title=""Enhanced Security Services for S/MIME"">ESS</a>] or ESSCertIDv2 [<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>]) of the TSA certificate
MUST be included as a signerInfo attribute inside a
SigningCertificate attribute.
<span class="grey">Santesson & Pope Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc5816">RFC 5816</a> ESSCertIDv2 Update for <a href="./rfc3161">RFC 3161</a> March 2010</span>
Note: As mentioned in <a href="./rfc5035">RFC 5035</a> [<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>], the SigningCertificateV2
attribute MUST be used if any algorithm other than SHA-1 is
used and SHOULD NOT be used for SHA-1.
Note: For backwards compatibility, in line with <a href="./rfc5035">RFC 5035</a>, both
ESSCertID and ESSCertIDv2 MAY be present. Systems MAY
ignore ESSCertIDv2 if <a href="./rfc5035">RFC 5035</a> has not been implemented.
<span class="h4"><a class="selflink" id="section-2.2.2" href="#section-2.2.2">2.2.2</a>. Verifying the Time-Stamp Token</span>
Third paragraph on Page 11.
Old:
The purpose of the tsa field is to give a hint in identifying the
name of the TSA. If present, it MUST correspond to one of the
subject names included in the certificate that is to be used to
verify the token. However, the actual identification of the
entity that signed the response will always occur through the use
of the certificate identifier (ESSCertID Attribute) inside a
SigningCertificate attribute which is part of the signerInfo (See
Section 5 of [<a href="#ref-ESS" title=""Enhanced Security Services for S/MIME"">ESS</a>]).
New:
The purpose of the tsa field is to give a hint in identifying the
name of the TSA. If present, it MUST correspond to one of the
subject names included in the certificate that is to be used to
verify the token. However, the actual identification of the
entity that signed the response will always occur through the use
of the certificate identifier (ESSCertID inside a
SigningCertificate attribute or ESSCertIDv2 inside a
SigningCertificateV2 attribute) that is part of the signerInfo
(see Section 5 of [<a href="#ref-ESS" title=""Enhanced Security Services for S/MIME"">ESS</a>] and <a href="#section-3">Section 3</a> of [<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>]).
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Security Considerations</span>
This document incorporates the security considerations of <a href="./rfc5035">RFC 5035</a>
[<a href="#ref-ESSV2" title=""Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility"">ESSV2</a>] with further explanations in this section.
ESSCertID provides a means based on the SHA-1 hash algorithm for
identifying the certificate used to verify the signature on a time
stamp. The use of ESSCertIDv2 aims to enable implementers to comply
with policies that require phasing out all uses of the SHA-1
algorithm.
<span class="grey">Santesson & Pope Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc5816">RFC 5816</a> ESSCertIDv2 Update for <a href="./rfc3161">RFC 3161</a> March 2010</span>
The update provided by this document is motivated by reasons of
interoperability and migration to other hash algorithms rather than
mitigating new security issues.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. References</span>
<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>. Normative References</span>
[<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>, March 1997.
[<a id="ref-ESS">ESS</a>] Hoffman, P., Ed., "Enhanced Security Services for
S/MIME", <a href="./rfc2634">RFC 2634</a>, June 1999.
[<a id="ref-ESSV2">ESSV2</a>] Schaad, J., "Enhanced Security Services (ESS) Update:
Adding CertID Algorithm Agility", <a href="./rfc5035">RFC 5035</a>, August 2007.
[<a id="ref-RFC3161">RFC3161</a>] Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,
"Internet X.509 Public Key Infrastructure Time-Stamp
Protocol (TSP)", <a href="./rfc3161">RFC 3161</a>, August 2001.
[<a id="ref-RFC5652">RFC5652</a>] Housley, R., "Cryptographic Message Syntax (CMS)",
<a href="./rfc5652">RFC 5652</a>, September 2009.
<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>. Informative References</span>
[<a id="ref-SHA1">SHA1</a>] Secure Hash Standard. FIPS Pub 180-1. National Institute
of Standards and Technology. 17 April 1995.
Authors' Addresses
Stefan Santesson
3xA Security AB
Sweden
EMail: sts@aaa-sec.com
Nick Pope
Thales Information Systems Security
Long Crendon, Aylesbury
United Kingdom
EMail: nick.pope@thales-esecurity.com
Santesson & Pope Standards Track [Page 5]
</pre>
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