--- 1/draft-ietf-lamps-eai-addresses-11.txt 2017-06-30 07:13:23.778140570 -0700 +++ 2/draft-ietf-lamps-eai-addresses-12.txt 2017-06-30 07:13:23.814141423 -0700 @@ -1,19 +1,19 @@ LAMPS A. Melnikov, Ed. Internet-Draft Isode Ltd Intended status: Standards Track W. Chuang, Ed. -Expires: December 20, 2017 Google, Inc. - June 18, 2017 +Expires: December 31, 2017 Google, Inc. + June 29, 2017 Internationalized Email Addresses in X.509 certificates - draft-ietf-lamps-eai-addresses-11 + draft-ietf-lamps-eai-addresses-12 Abstract This document defines a new name form for inclusion in the otherName field of an X.509 Subject Alternative Name and Issuer Alternative Name extension that allows a certificate subject to be associated with an Internationalized Email Address. Status of This Memo @@ -23,21 +23,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on December 20, 2017. + This Internet-Draft will expire on December 31, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -116,21 +116,21 @@ This document further refines Internationalized [RFC6531] Mailbox ABNF rules and calls this SmtpUTF8Mailbox. In SmtpUTF8Mailbox, labels that include non-ASCII characters MUST be stored in U-label (rather than A-label) [RFC5890] form. This restriction removes the need to determine which label encoding A- or U-label is present in the Domain. As per Section 2.3.2.1 of [RFC5890], U-label are encoded as UTF-8 [RFC3629] in Normalization Form C and other properties specified there. In SmtpUTF8Mailbox, domain labels that solely use ASCII characters (meaning not A- nor U-labels) SHALL use NR-LDH - restrictions as specified by section 2.3.1 of [RFC5890] and SHALL be + restrictions as specified by Section 2.3.1 of [RFC5890] and SHALL be restricted to lower case letters. NR-LDH stands for "Non-Reserved Letters Digits Hyphen" and is the set LDH labels that do not have "--" characters in the third and forth character position, which excludes "tagged domain names" such as A-labels. Consistent with the treatment of rfc822Name in [RFC5280], SmtpUTF8Name is an envelope and has no phrase (such as a common name) before it, has no comment (text surrounded in parentheses) after it, and is not surrounded by "<" and ">". Due to operational reasons to be described shortly and name @@ -156,86 +156,89 @@ anywhere else that these are used. 5. Matching of Internationalized Email Addresses in X.509 certificates In equivalence comparison with SmtpUTF8Name, there may be some setup work on one or both inputs depending of whether the input is already in comparison form. Comparing SmtpUTF8Names consists of a domain part step and a local-part step. The comparison form for local-parts always is UTF-8. The comparison form for domain parts depends on context. While some contexts such as certificate path validation in - [RFC5280] specify transforming domain to A-label (section 7.5 and 7.2 - in [RFC5280]), this document RECOMMENDS transforming to UTF-8 U-label - instead. This reduces the likelihood of errors by reducing - conversions as more implementations natively support U- label - domains. + [RFC5280] specify transforming domain to A-label (Section 7.5 and 7.2 + in [RFC5280] as updated by [ID-lamps-rfc5280-i18n-update]), this + document RECOMMENDS transforming to UTF-8 U-label instead. This + reduces the likelihood of errors by reducing conversions as more + implementations natively support U- label domains. Comparison of two SmtpUTF8Name is straightforward with no setup work needed. They are considered equivalent if there is an exact octet- for-octet match. Comparison with email addresses such as Internationalized email address or rfc822Name requires additional setup steps for domain part and local-part. The initial preparation for the email addresses is to remove any phrases or comments, as well as "<" and ">" present. This document calls for comparison of domain labels that include non-ASCII characters be tranformed to U-label if not already in that form. The first step is to detect use of the - A-label by using section 5.1 of [RFC5891]. Next if necessary, - transform any A-labels to U-labels Unicode as specified in section - 5.2 of [RFC5891]. Finally if necessary convert the Unicode to UTF-8 - as specified in section 3 of [RFC3629]. For ASCII NR-LDH labels, - upper case letters are converted to lower case letters. In setup for - SmtpUTF8Mailbox, the email address local-part MUST conform to the - requirements of [RFC6530] and [RFC6531], including being a string in - UTF-8 form. In particular, the local-part MUST NOT be transformed in - any way, such as by doing case folding or normalization of any kind. - The part of an Internationalized email address is - already in UTF-8. For rfc822Name the local-part, which is IA5String - (ASCII), trivially maps to UTF-8 without change. Once setup is - complete, they are again compared octet-for-octet. + A-label by using Section 5.1 of [RFC5891]. Next if necessary, + transform any A-labels to U-labels Unicode as specified in + Section 5.2 of [RFC5891]. Finally if necessary convert the Unicode + to UTF-8 as specified in Section 3 of [RFC3629]. For ASCII NR-LDH + labels, upper case letters are converted to lower case letters. In + setup for SmtpUTF8Mailbox, the email address local-part MUST conform + to the requirements of [RFC6530] and [RFC6531], including being a + string in UTF-8 form. In particular, the local-part MUST NOT be + transformed in any way, such as by doing case folding or + normalization of any kind. The part of an + Internationalized email address is already in UTF-8. For rfc822Name + the local-part, which is IA5String (ASCII), trivially maps to UTF-8 + without change. Once setup is complete, they are again compared + octet-for-octet. To summarize non-normatively, the comparison steps including setup are: 1. If the domain contains A-labels, transform them to U-labels. 2. If the domain contains ASCII NR-LDH labels, lowercase them. 3. Compare strings octet-for-octet for equivalence. This specification expressly does not define any wildcard characters and SmtpUTF8Name comparison implementations MUST NOT interpret any character as wildcards. Instead, to specify multiple email addresses through SmtpUTF8Name, the certificate MUST use multiple subjectAltNames or issuerAltNames to explicitly carry any additional email addresses. 6. Name constraints in path validation - This section updates section 4.2.1.10 of [RFC5280] to extend + This section updates Section 4.2.1.10 of [RFC5280] to extend rfc822Name name constraints to SmtpUTF8Name subjectAltNames. A SmtpUTF8Name aware path validators will apply name constraint comparison to the subject distinguished name and both forms of subject alternative name rfc822Name and SmtpUTF8Name. Both rfc822Name and SmtpUTF8Name subject alternative names represent the same underlying email address namespace. Since legacy CAs constrained to issue certificates for a specific set of domains would - lack corresponding UTF-8 constraints, this specification modifies and - extends rfc822Name name SmtpUTF8Name does not violate existing name - constraints. Since it is not valid to include non-ASCII UTF-8 - characters in the local-part of rfc822Name name constraints, and - since name constraints that include a local-part are rarely, if at - all, used in practice, this specification modifies [RFC5280] name - constraints to only admit the forms represent all addresses at a host - or all mailboxes in a domain, and deprecates rfc822Name name - constraints that represent a particular mailbox. That is, rfc822Name - constraints with a local-part SHOULD NOT be used. + lack corresponding UTF-8 constraints, [ID-lamps-rfc5280-i18n-update] + updates modifies and extends rfc822Name name constraints defined in + [RFC5280] to cover SmtpUTF8Name subject alternative names. This + ensures that the introduction of SmtpUTF8Name does not violate + existing name constraints. Since it is not valid to include non- + ASCII UTF-8 characters in the local-part of rfc822Name name + constraints, and since name constraints that include a local-part are + rarely, if at all, used in practice, name constraints updated in + [ID-lamps-rfc5280-i18n-update] admit the forms that represent all + addresses at a host or all mailboxes in a domain, and deprecates + rfc822Name name constraints that represent a particular mailbox. + That is, rfc822Name constraints with a local-part SHOULD NOT be used. Constraint comparison with SmtpUTF8Name subjectAltName starts with the setup steps defined by Section 5. Setup converts the inputs of the comparison which is one of a subject distinguished name or a rfc822Name or SmtpUTF8Name subjectAltName, and one of a rfc822Name name constraint, to constraint comparison form. For rfc822Name name constraint, this will convert any domain A-labels to U-labels. For both the name constraint and the subject, this will lower case any domain NR-LDH labels. Strip the local-part and "@" separator from each rfc822Name and SmtpUTF8Name, leaving just the domain-part. @@ -302,34 +305,38 @@ in Section 8 in [RFC5280] , but introduces a new issue by permitting non-ASCII characters in the email address local-part. This issue, as mentioned in Section 4.4 of [RFC5890] and in Section 4 of [RFC6532], is that use of Unicode introduces the risk of visually similar and identical characters which can be exploited to deceive the recipient. The former document references some means to mitigate against these attacks. 8. IANA Considerations - in Section Section 3 and the ASN.1 module identifier defined in - Section Appendix A. IANA is kindly requested to make the following - assignments for: + In Section 3 and the ASN.1 module identifier defined in Appendix A. + IANA is kindly requested to make the following assignments for: The LAMPS-EaiAddresses-2016 ASN.1 module in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). The SmtpUTF8Name otherName in the "PKIX Other Name Forms" registry (1.3.6.1.5.5.7.8). 9. References 9.1. Normative References + [ID-lamps-rfc5280-i18n-update] + Housley, R., "Internationalization Updates to RFC 5280", + June 2017, . + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax @@ -414,41 +421,39 @@ on-SmtpUTF8Name OTHER-NAME ::= { SmtpUTF8Name IDENTIFIED BY id-on-SmtpUTF8Name } id-on-SmtpUTF8Name OBJECT IDENTIFIER ::= { id-on 9 } SmtpUTF8Name ::= UTF8String (SIZE (1..MAX)) END - Figure 2 - Appendix B. Example of SmtpUTF8Name This non-normative example demonstrates using SmtpUTF8Name as an otherName in GeneralName to encode the email address "u+8001u+5E2B@example.com". The hexadecimal DER encoding of the email address is: A022060A 2B060105 05070012 0809A014 0C12E880 81E5B8AB 40657861 6D706C65 2E636F6D The text decoding is: 0 34: [0] { 2 10: OBJECT IDENTIFIER '1 3 6 1 5 5 7 0 18 8 9' 14 20: [0] { 16 18: UTF8String '..@example.com' : } : } - Figure 3 + Figure 2 The example was encoded on the OSS Nokalva ASN.1 Playground and the above text decoding is an output of Peter Gutmann's "dumpasn1" program. Appendix C. Acknowledgements Thank you to Magnus Nystrom for motivating this document. Thanks to Russ Housley, Nicolas Lidzborski, Laetitia Baudoin, Ryan Sleevi, Sean Leonard, Sean Turner, John Levine, and Patrik Falstrom for their