PKIX Working Group                              S. Santesson (Microsoft)
INTERNET-DRAFT                               R. Housley (Vigil Security)
Expires July 2005
Updates RFC 3280                                           January 2005

                Internet X.509 Public Key Infrastructure
               Authority Information Access CRL Extension
                    <draft-ietf-pkix-crlaia-00.txt>


Status of this Memo

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   patent or other IPR claims of which I am aware have been disclosed,
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Abstract

   This document updates RFC 3280 by defining the Authority Information
   Access Certificate Revocation Lists (CRL) extension.  RFC 3280
   defines the Authority Information Access certificate extension using
   the same syntax.  The CRL extension provides a means of discovering
   and retrieving CRL issuer certificates.










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Table of Contents

   1  Introduction ................................................    2
   2  Authority Information Access Extension in CRL ...............    4
   3  Security Considerations .....................................    5
   4  References ..................................................    5
   Authors' Addresses .............................................    6
   Disclaimer .....................................................    7
   Copyright Statement ............................................    7

1.  Introduction

   RFC 3280 [PKIX1] specifies the validation of certification paths.
   One aspect involves the determination that a certificate has not been
   revoked, and one revocation checking mechanism is the Certificate
   Revocation List (CRL).  CRL validation is also specified in RFC 3280,
   which involves the constructions of a valid certification path for
   the CRL issuer.  Building a CRL issuer certification path from the
   signer of the CRL to a trust anchor is straightforward when the
   certificate of the CRL issuer is present in the certification path
   associated with the target certificate.

   There is however several legitimate scenarios where the certificate
   of the CRL issuer is not present, or easily discovered, from the
   target certification path.  This can be the case when indirect CRLs
   are used, when the certification Authority (CA) that issued the
   target certificate changes its certificate signing key, or when the
   CA employs separate keys for certificate signing and CRL signing.

   Standardized methods of finding the certificate of the CRL issuer are
   currently available either though an accessible directory location or
   through use of the Subject Information Access extension in
   intermediary CA certificates.  These methods are however not
   generally applicable, and they do not provide a generic solution to
   the problem.  Directory lookup requires presence and access to a
   directory.  The Subject Information Access extension supports
   building the CRL issuer certification path top-down (in the direction
   from the trust anchor to the CRL issuer), which can be complex and
   will fail if critical certificates in the CRL issuer certification
   path do not include an appropriate Subject Information Access
   extension.

   RFC 3280 [PKIX1] has provided for bottom-up discovery of
   certification paths through the Authority Information Access
   extension, where the id-ad-caIssuers access method may specify one or
   more accessLocation fields that contain references to CA certificates
   superior to the certificate containing this extension.




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   This document provides a straightforward and generic solution to the
   CRL issuer certification path building problem by permitting use of
   the Authority Information Access extension in CRLs, enabling a CRL
   checking application to use the same access method (id-ad-caIssuers)
   to locate the certificate of the CRL issuer and, if necessary,
   complete the CRL issuer certification path building to an appropriate
   trust anchor.












































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INTERNET DRAFT Authority Information Access CRL Extension   January 2005


2.  Authority Information Access CRL Extension

   This section defines the use of the Authority Information Access
   extension in a CRL.  The syntax and semantics defined in RFC 3280
   [PKIX1] for the certificate extensions are also used for the CRL
   extension.

   This CRL extension MUST NOT be marked critical.

   This extension MUST be identified by the extension object identifier
   (OID) defined in RFC 3280 (1.3.6.1.5.5.7.1.1), and the
   AuthotiyInfoAccessSyntax MUST be used to form the extension value.
   For convenience, the ASN.1 [X.680] definition of the Authority
   Information Access extension is repeated below.

      id-pe-authorityInfoAccess OBJECT IDENTIFIER  ::=  { id-pe 1 }

      AuthorityInfoAccessSyntax  ::=  SEQUENCE SIZE (1..MAX) OF
                               AccessDescription

      AccessDescription  ::=  SEQUENCE {
         accessMethod          OBJECT IDENTIFIER,
         accessLocation        GeneralName  }

      id-ad OBJECT IDENTIFIER  ::=  { id-pkix 48 }

      id-ad-caIssuers OBJECT IDENTIFIER  ::=  { id-ad 2 }

   When present in a CRL, this extension MUST include at least one
   AccessDescription specifying id-ad-caIssuers as the acessMethod.
   Access method types other than id-ad-caIssuers MUST NOT be included.

   All present accessLocation values MUST use the
   uniformResourceIdentifier [URI] form, and the values MUST use either
   the ldap scheme [LDAP] or the http scheme [HTTP/1.1].

   When ldap scheme is specified, the URI MUST point to an attribute
   containing one or more binary DER [X.660] encoded certificate.

   When the http scheme is specified, the URI MUST point to a
   certificate file.  The certificate file MUST contain either a single
   DER encoded certificate (indicated by the .cer file extension) or
   contain a certification path (indicated by the .p7c file extension):

      .cer   A single DER encoded certificate as specified in
             RFC 2585 [PKIX-CERT].

      .p7c   A MIME encoded application/pkcs7-mime "certs-only" file



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INTERNET DRAFT Authority Information Access CRL Extension   January 2005


             as specified in RFC 2797 [CMC].


3  Security Considerations

     Implementers should take into account the possible existence of
     multiple unrelated CAs and CRL issuers with the same name.  As
     means of reducing problems and security issues related to issuer
     name collisions, CA names SHOULD be formed in a way that reduce the
     likelihood of name collisions.  Implementations validating CRLs
     MUST ensure that the certification path of the target certificate
     and the CRL issuer certification path used to validate the target
     certificate, terminate at the same trust anchor.

     Implementers should be aware of risks involved if the Authority
     Information Access extensions of corrupted CRLs contain links to
     malicious code.  Implementers should always take the steps of
     validating the retrieved data to ensure that the data is properly
     formed.


4 References

     Normative references:

     [RFC 2119]  S. Bradner, "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

     [RFC 3280]  R. Housley, W. Polk, W. Ford, and D. Solo, "Internet
                 X.509 Public Key Infrastructure: Certificate and
                 Certificate Revocation List (CRL) Profile", RFC 3280,
                 April 2002.


     [HTTP/1.1]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
                 Masinter, L., Leach P. and T. Berners-Lee, "Hypertext
                 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

     [URI]       Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
                 Resource Identifiers (URI): Generic Syntax", RFC 2396,
                 August 1998.

     [LDAP]      Wahl, M., Howes, T., and S. Kille, "Lightweight Directory
                 Access Protocol (v3)", RFC 2251, December 1997.

     [PKIX-CERT] R. Housley and P. Hoffman, "Internet X.509 Public Key
                 Infrastructure: Operational Protocols: FTP and HTTP",
                 RFC 2585, May 1999.



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     [CMC]       M. Myers, X. Liu, J. Schaad, J. Weinstein, "Certificate
                 Management Messages over CMS", RFC 2797, April 2000.

     Informative references:

     [X.680]     ITU-T Recommendation X.680 (2002) | ISO/IEC 8824-1:2002),
                 Information Technology - Abstract Syntax Notation One,
                 2002.

     [X.660]     ITU-T Recommendation X.660 Information Technology - ASN.1
                 encoding rules: Specification of Basic Encoding Rules
                 (BER), Canonical Encoding Rules (CER) and Distinguished
                 Encoding Rules (DER), 1997.




Authors' Addresses


     Stefan Santesson
     Microsoft
     Tuborg Boulevard 12
     2900 Hellerup
     Denmark

     EMail: stefans@microsoft.com


     Russell Housley
     Vigil Security, LLC
     918 Spring Knoll Drive
     Herndon, VA 20170
     USA

     EMail: housley@vigilsec.com















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INTERNET DRAFT Authority Information Access CRL Extension   January 2005


Disclaimer

     This document and the information contained herein are provided on
     an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
     REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
     THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
     THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
     ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
     PARTICULAR PURPOSE.


Copyright Statement

     Copyright (C) The Internet Society (2004).  This document is
     subject to the rights, licenses and restrictions contained in BCP
     78, and except as set forth therein, the authors retain all their
     rights.


Expires July 2005






























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