Clarifications to the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile
draft-ietf-pkix-rfc5280-clarifications-03

INTERNET-DRAFT                                                 D. Cooper
Intended Status: Proposed Standard                                  NIST
Updates: 5280 (if approved)                              August 11, 2011
Expires: February 12, 2012                                              

     Clarifications to the Internet X.509 Public Key Infrastructure
       Certificate and Certificate Revocation List (CRL) Profile 
            <draft-ietf-pkix-rfc5280-clarifications-03.txt>

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Abstract

   This document updates RFC 5280, the Internet X.509 Public Key
   Infrastructure Certificate and Certificate Revocation List (CRL)
   Profile.  This document changes the set of acceptable encoding
   methods for the explicitText field of the user notice policy
   qualifier and clarifies the rules for converting internationalized
   domain name labels to ASCII.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Update to RFC 5280, Section 4.2.1.4: Certificate Policies  . .  3
   3.  Update to RFC 5280, Section 7.3: Internationalized Domain 
       Names in Distinguished Names . . . . . . . . . . . . . . . . .  4
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     6.1.  Normative References . . . . . . . . . . . . . . . . . . .  5
     6.2.  Informative References . . . . . . . . . . . . . . . . . .  5
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .  5

1.  Introduction

   This document updates the Internet X.509 Public Key Infrastructure
   Certificate and Certificate Revocation List (CRL) Profile [RFC5280].

   The ASN.1 [X.680] syntax for the user notice certificate policy
   qualifier allows for the explicitText field to be encoded using one
   of four possible encoding methods: IA5String, VisibleString,
   BMPString, or UTF8String.  RFC 5280 permits certification authorities
   (CA) to encode strings in the explicitText field as either UTF8String
   or IA5String while forbidding the use of VisibleString and BMPString.
   However, after RFC 5280 was published, an examination of existing
   certificates found that the VisibleString encoding was commonly used.
   This document brings the requirements into closer alignment with
   existing practice by stating that the explicitText field may be
   encoded in either UTF8String, VisibleString, or BMPString while
   forbidding the use of IA5String.

   Section 7.3 of RFC 5280 specifies rules for converting
   internationalized domain name labels that are to appear in a
   domainComponent attribute to ASCII.  The conversion process specified
   in RFC 5280 did not specify that the "UseSTD3ASCIIRules" flag needed
   to be set.  This document modifies the conversion process specified
 

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   in Section 7.3 of RFC 5280 to clarify that "UseSTD3ASCIIRules" flag
   should be set.  The result of this is to indicate that the check for
   conformance to [RFC1123] should be performed.  

1.1.  Terminology

   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 RFC 2119 [RFC2119].

2.  Update to RFC 5280, Section 4.2.1.4: Certificate Policies

   RFC 5280, Section 4.2.1.4, the tenth paragraph says:

|     An explicitText field includes the textual statement directly in
|     the certificate.  The explicitText field is a string with a
|     maximum size of 200 characters.  Conforming CAs SHOULD use the
|     UTF8String encoding for explicitText, but MAY use IA5String.
|     Conforming CAs MUST NOT encode explicitText as VisibleString or
|     BMPString.  The explicitText string SHOULD NOT include any control
|     characters (e.g., U+0000 to U+001F and U+007F to U+009F).  When
|     the UTF8String encoding is used, all character sequences SHOULD be
|     normalized according to Unicode normalization form C (NFC) [NFC].

   This paragraph is replaced with:

|     An explicitText field includes the textual statement directly in
|     the certificate.  The explicitText field is a string with a
|     maximum size of 200 characters.  Conforming CAs SHOULD use the
|     UTF8String encoding for explicitText, but MAY use VisibleString or
|     BMPString.  Conforming CAs MUST NOT encode explicitText as 
|     IA5String.  The explicitText string SHOULD NOT include any control
|     characters (e.g., U+0000 to U+001F and U+007F to U+009F).  When
|     the UTF8String or BMPString encoding is used, all character
|     sequences SHOULD be normalized according to Unicode normalization
|     form C (NFC) [NFC].

 

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3.  Update to RFC 5280, Section 7.3: Internationalized Domain Names in
   Distinguished Names

   RFC 5280, Section 7.3, the first paragraph says:

|  Domain Names may also be represented as distinguished names using
|  domain components in the subject field, the issuer field, the
|  subjectAltName extension, or the issuerAltName extension.  As with
|  the dNSName in the GeneralName type, the value of this attribute is
|  defined as an IA5String.  Each domainComponent attribute represents a
|  single label.  To represent a label from an IDN in the distinguished
|  name, the implementation MUST perform the "ToASCII" label conversion
|  specified in Section 4.1 of RFC 3490.  The label SHALL be considered
|  a "stored string".  That is, the AllowUnassigned flag SHALL NOT be
|  set.

   This paragraph is replaced with:

|  Domain Names may also be represented as distinguished names using
|  domain components in the subject field, the issuer field, the
|  subjectAltName extension, or the issuerAltName extension.  As with
|  the dNSName in the GeneralName type, the value of this attribute is
|  defined as an IA5String.  Each domainComponent attribute represents a
|  single label.  To represent a label from an IDN in the distinguished
|  name, the implementation MUST perform the "ToASCII" label conversion
|  specified in Section 4.1 of RFC 3490 with the UseSTD3ASCIIRules flag
|  set.  The label SHALL be considered a "stored string".  That is, the
|  AllowUnassigned flag SHALL NOT be set.  The conversion process is the
|  same as is performed in step 4 in Section 7.2.

 

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4.  Security Considerations

   This document introduces no new security considerations.

5.  IANA Considerations

   This document has no actions for IANA.

6.  References 

6.1.  Normative References

   [RFC1123]   Braden, R., Ed., "Requirements for Internet Hosts --
               Application and Support", STD 3, RFC 1123, October 1989.

   [RFC2119]   S. Bradner, "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5280]   Cooper, D., S. Santesson, S. Farrell, S. Boeyen, R.
               Housley and W. Polk, "Internet X.509 Public Key
               Infrastructure Certificate and Certificate Revocation
               List (CRL) Profile", RFC 5280, May 2008.

6.2.  Informative References

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

   [NFC]       Davis, M. and M. Duerst, "Unicode Standard Annex #15:
               Unicode Normalization Forms", October 2006,
               <http://www.unicode.org/reports/tr15/>.

Author's Address

   David Cooper
   National Institute of Standards and Technology
   100 Bureau Drive, Mail Stop 8930
   Gaithersburg, MD 20899-8930
   USA

   EMail: david.cooper@nist.gov

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