Internationalization Updates to RFC 5280
draft-housley-rfc5280-i18n-update-00

INTERNET-DRAFT                                                          
Internet Engineering Task Force                               R. Housley
Intended Status: Proposed Standard                        Vigil Security
Updates: RFC 5280 (once approved)                                       
Expires: 5 July 2017                                      5 January 2017

                Internationalization Updates to RFC 5280
                  draft-housley-rfc5280-i18n-update-00

Abstract

   These updates to RFC 5280 provide clarity on the handling of
   Internationalized Domain Names (IDNs) and Internationalized Email
   Addresses in X.509 Certificates.

Status of this Memo

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Copyright and License Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors. All rights reserved.

 

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   described in the Simplified BSD License.

1.  Introduction

   These updates to the Introduction and Section 7 of RFC 5280 [RFC5280]
   provide clarity on the handling of Internationalized Domain Names
   (IDNs) and Internationalized Email Addresses in X.509 Certificates.

   IDNs are converted to punycode.  The punycode form is carried in
   certificate, and the punycode form is used to compare two IDNs.

   The conversion to punycode is defined in Section 4 of RFC 3490
   [RFC3490].  In addition, Section 7.2 of RFC 5280 [RFC5280] provides
   some guidance about the flags used in that process.  That guidance is
   not changed by this update.

   Note that Internationalized Domain Names in Applications
   specification published in 2008 (IDNA2008) [RFC5891][RFC5892] also
   refer to RFC 3490 for the conversion to punycode.

   Internationalized Email Addresses that contain non-ASCII characters
   in the local-part of the address follow the conventions recently
   specified by the IETF LAMPS working group.

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.  Updates

   This section provides updates to several paragraphs in the
   Introduction and Section 7 of RFC 5280 [RFC5280].  For clarity, the
   original text and the replacement text are shown. 

 

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2.1.  Update in Section 1, Introduction

OLD

      * Enhanced support for internationalized names is specified in
        Section 7, with rules for encoding and comparing
        Internationalized Domain Names, Internationalized Resource
        Identifiers (IRIs), and distinguished names.  These rules are
        aligned with comparison rules established in current RFCs,
        including [RFC3490], [RFC3987], and [RFC4518].

NEW

      * Enhanced support for internationalized names is specified in
        Section 7, with rules for encoding and comparing
        Internationalized Domain Names, Internationalized Resource
        Identifiers (IRIs), and distinguished names.  These rules are
        aligned with comparison rules established in current RFCs,
        including [RFC3490], [RFC3987], [RFC4518], [RFC5890], and
        [RFC5891].

2.2.  Update in Section 7.2, IDNs in GeneralName

OLD

   IA5String is limited to the set of ASCII characters.  To accommodate
   internationalized domain names in the current structure, conforming
   implementations MUST convert internationalized domain names to the
   ASCII Compatible Encoding (ACE) format as specified in Section 4 of
   RFC 3490 before storage in the dNSName field.  Specifically,
   conforming implementations MUST perform the conversion operation
   specified in Section 4 of RFC 3490, with the following
   clarifications:

    ...

   Implementations should convert IDNs to Unicode before display.
   Specifically, conforming implementations should perform the
   conversion operation specified in Section 4 of RFC 3490, with the
   following clarifications:

NEW

   IA5String is limited to the set of ASCII characters.  To accommodate
   internationalized domain names in the current structure, conforming
   implementations MUST convert IDNs [RFC5890][RFC5891] to the
   ASCII Compatible Encoding (ACE) format as specified in Section 4 of
   [RFC3490] before placement in the dNSName field.  Specifically,
 

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   conforming implementations MUST perform the conversion operation
   specified in Section 4 of [RFC3490], with the following
   clarifications:

    ...

   Implementations should convert IDNs to Unicode before display.
   Specifically, conforming implementations should perform the
   conversion operation specified in Section 4 of [RFC3490], with the
   following clarifications:

2.3.  Update in Section 7.3, IDNs in Distinguished Names

OLD

   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.

NEW

   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 [RFC3490].  The label SHALL be considered
   a "stored string".  That is, the AllowUnassigned flag SHALL NOT be
   set.

2.4.  Update in Section 7.5, Internationalized Electronic Mail Addresses

OLD

   Electronic Mail addresses may be included in certificates and CRLs in
   the subjectAltName and issuerAltName extensions, name constraints
   extension, authority information access extension, subject
   information access extension, issuing distribution point extension,
 

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   or CRL distribution points extension.  Each of these extensions uses
   the GeneralName construct; GeneralName includes the rfc822Name
   choice, which is defined as type IA5String.  To accommodate email
   addresses with internationalized domain names using the current
   structure, conforming implementations MUST convert the addresses into
   an ASCII representation.

   Where the host-part (the Domain of the Mailbox) contains an
   internationalized name, the domain name MUST be converted from an IDN
   to the ASCII Compatible Encoding (ACE) format as specified in Section
   7.2.

   Two email addresses are considered to match if:

      1)  the local-part of each name is an exact match, AND

      2)  the host-part of each name matches using a case-insensitive
          ASCII comparison.

   Implementations should convert the host-part of internationalized
   email addresses specified in these extensions to Unicode before
   display.  Specifically, conforming implementations should perform the
   conversion of the host-part of the Mailbox as described in Section
   7.2.

NEW

   Electronic Mail addresses may be included in certificates and CRLs in
   the subjectAltName and issuerAltName extensions, name constraints
   extension, authority information access extension, subject
   information access extension, issuing distribution point extension,
   or CRL distribution points extension.  Each of these extensions uses
   the GeneralName construct.  If the email address includes an IDN but
   the local-part of the email address can be represented in ASCII, then
   the email address is placed in the rfc822Name choice of GeneralName,
   which is defined as type IA5String.  If the local-part of the
   internationalized email address cannot be represented in ASCII, then
   the internationalized email address is placed in the otherName choice
   of GeneralName using the conventions in [ID.lamps-eai-addresses].

   7.5.1.  Local-part Contains Only ASCII Characters

   Where the host-part contains an IDN, conforming implementations MUST
   convert the domain name into an ASCII representation using the ASCII
   Compatible Encoding (ACE) format as specified in Section 7.2.

   Two email addresses are considered to match if:

 

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      1)  the local-part of each name is an exact match, AND

      2)  the host-part of each name matches using a case-insensitive
          ASCII comparison.

   Implementations should convert the host-part of internationalized
   email addresses specified in these extensions to Unicode before
   display.  Specifically, conforming implementations should perform the
   conversion of the host-part of the Mailbox as described in Section
   7.2.

   7.5.2.  Local-part Contains Non-ASCII Characters

   When the local-part contains non-ASCII character, conforming
   implementations MUST be placed in the SmtpUtf8Name within the
   otherName choice of GeneralName as specified in Section 3 of
   [ID.lamps-eai-addresses].  Note that the UTF8 encoding of the
   internationalized email address MUST NOT contain a
   Byte-Order-Mark (BOM) [RFC3629] to aid comparison.

   The comparison of two internationalized email addresses is
   specified in Section 4 of [ID.lamps-eai-addresses].

   Implementations should convert the local-part and the host-part of
   internationalized email addresses placed in these extensions to
   Unicode before display.

3.  Security Considerations

   The security considerations in RFC 5280 [RFC5280] are not changed by
   this update.

4.  IANA Considerations

   No IANA registries are changed by this update.

5.  Normative References

   [ID.lamps-eai-addresses]
              Melnikov, A. (Ed.) and W. Chuang (Ed.), "Internationalized
              Email Addresses in X.509 certificates", December 2016,
              <http://www.ietf.org/id/draft-ietf-lamps-eai-addresses>,
              work-in-progress.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI
              10.17487/RFC2119, March 1997, <http://www.rfc-
              editor.org/info/rfc2119>.
 

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   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, DOI 10.17487/RFC3490, March 2003,
              <http://www.rfc-editor.org/info/rfc3490>.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
              January 2005, <http://www.rfc-editor.org/info/rfc3987>.

   [RFC4518]  Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP): Internationalized String Preparation", RFC 4518,
              DOI 10.17487/RFC4518, June 2006, <http://www.rfc-
              editor.org/info/rfc4518>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891, DOI
              10.17487/RFC5891, August 2010, <http://www.rfc-
              editor.org/info/rfc5891>.

   [RFC5892]  Faltstrom, P., Ed., "The Unicode Code Points and
              Internationalized Domain Names for Applications (IDNA)",
              RFC 5892, DOI 10.17487/RFC5892, August 2010,
              <http://www.rfc-editor.org/info/rfc5892>.

6.  Informative References

   [RFC3639]  St. Johns, M., Ed., Huston, G., Ed., and IAB,
              "Considerations on the use of a Service Identifier in
              Packet Headers", RFC 3639, DOI 10.17487/RFC3639, October
              2003, <http://www.rfc-editor.org/info/rfc3639>.

Acknowledgements

   Thanks to John Klensin for confirming many of the details in this
   update.

   Thanks to Alexey Melnikov for the encouragement to write this update.

 

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Authors' Address

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

   EMail: housley@vigilsec.com

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