Security Working Group L. Baudoin
Internet-Draft W. Chuang
Expires: August 7, 2016 N. Lidzborski
Google, Inc.
February 4, 2016
Internationalized Electronic Mail Addresses in RFC5280 / X.509
Certificates
draft-lbaudoin-iemax-02
Abstract
Specifies support for email address internationalization in RFC5280 /
X.509 certificates. This defines an encoding for Unicode email
local-part characters in certificate Subject Alternative Names and
Issuer Alternative rfc822Names. The encoding is backwards compatible
with existing practices with rfc822Name.
Status of This Memo
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Internet-Draft Internationalized-Email-X509 February 2016
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Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Background
Internationalization of email addresses has significant precedence.
Email addresses and their parts are specified in [RFC5322].
Internationalization of domain names was specified in [RFC3490] and
more recently in [RFC5890] via puny-coding of the unicode domain name
labels. Email address as certificate Subject Alternative Name (SAN)
and Issuer Alternative Name (IAN) rfc822Name support this
internationalization of domain names as described in section 7.5 of
[RFC5280]. In [RFC6532], email headers as specified in [RFC5321] and
[RFC5322] was refined to support UTF-8 unicode representation which
implies support for Unicode email addresses but RFC5280 was not
updated to take Unicode email local-part into account.
2. Proposal
This draft proposes an encoding for internationalized email addresses
with Unicode local-part. This encoding is a further refinement of
email addresses in RFC5280 SAN and IAN rfc822Name thus allowing
existing PKI practices using email addresses to continue. To support
the Unicode local-part, this draft proposes a base64 encoding for the
local-part string with an identifier character to distinguish this
encoding. That is the encoded string starts with an escape character
':' to identify that the local-part is Unicode and that the
successive characters contain the base64 encoded local-part until the
'@' at character is seen. The escape colon character is a character
intentionally choosen such that it is supported by IA5String but not
possible in a compliant ASCII RFC5322 email addresses. The local-
part of the email address then consists of Unicode UTF-8 name that
must be websafe base64url encoded as specifed in [RFC4648]. Support
for internationalized domain names in the certificates is already
specified in RFC5280, and this draft does not change that
interpretation for the email domain. Similarly the email address
must follow existing Mailbox name practices specified in RFC5280
section 4.2.1.6 that there must be no common name, no comment, nor
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Internet-Draft Internationalized-Email-X509 February 2016
"<" or ">" present. A compliant reader of the encoded email address
would strip the escape ':' and decode the base64 local-part to UTF-8.
One potential issue for an encoded internationalized SAN or IAN email
address is its impact on RFC5280 naming constraints particularly
between a draft compliant certificate and a non compliant
implementation. This encoding will not impact name matching in this
scenario as mismatching local-part names and constraints will always
match test negatively. The local-parts should only match if the
implementation is compliant with this draft. Because the draft does
not change internationalized domain name behavior, both the compliant
and non-compliant implementation can test domain name constraints in
the expected way.
3. References
[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>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[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>.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
DOI 10.17487/RFC5321, October 2008,
<http://www.rfc-editor.org/info/rfc5321>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<http://www.rfc-editor.org/info/rfc5322>.
[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>.
[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized
Email Headers", RFC 6532, DOI 10.17487/RFC6532, February
2012, <http://www.rfc-editor.org/info/rfc6532>.
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Authors' Addresses
Laetitia Baudoin
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email: lbaudoin@google.com
Weihaw Chuang
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email: weihaw@google.com
Nicolas Lidzborski
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email: nlidz@google.com
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