draft-ietf-lamps-eai-addresses-11.txt   draft-ietf-lamps-eai-addresses-12.txt 
LAMPS A. Melnikov, Ed. LAMPS A. Melnikov, Ed.
Internet-Draft Isode Ltd Internet-Draft Isode Ltd
Intended status: Standards Track W. Chuang, Ed. Intended status: Standards Track W. Chuang, Ed.
Expires: December 20, 2017 Google, Inc. Expires: December 31, 2017 Google, Inc.
June 18, 2017 June 29, 2017
Internationalized Email Addresses in X.509 certificates Internationalized Email Addresses in X.509 certificates
draft-ietf-lamps-eai-addresses-11 draft-ietf-lamps-eai-addresses-12
Abstract Abstract
This document defines a new name form for inclusion in the otherName This document defines a new name form for inclusion in the otherName
field of an X.509 Subject Alternative Name and Issuer Alternative field of an X.509 Subject Alternative Name and Issuer Alternative
Name extension that allows a certificate subject to be associated Name extension that allows a certificate subject to be associated
with an Internationalized Email Address. with an Internationalized Email Address.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." 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 Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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This document further refines Internationalized [RFC6531] Mailbox This document further refines Internationalized [RFC6531] Mailbox
ABNF rules and calls this SmtpUTF8Mailbox. In SmtpUTF8Mailbox, ABNF rules and calls this SmtpUTF8Mailbox. In SmtpUTF8Mailbox,
labels that include non-ASCII characters MUST be stored in U-label labels that include non-ASCII characters MUST be stored in U-label
(rather than A-label) [RFC5890] form. This restriction removes the (rather than A-label) [RFC5890] form. This restriction removes the
need to determine which label encoding A- or U-label is present in 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 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 as UTF-8 [RFC3629] in Normalization Form C and other properties
specified there. In SmtpUTF8Mailbox, domain labels that solely use specified there. In SmtpUTF8Mailbox, domain labels that solely use
ASCII characters (meaning not A- nor U-labels) SHALL use NR-LDH 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 restricted to lower case letters. NR-LDH stands for "Non-Reserved
Letters Digits Hyphen" and is the set LDH labels that do not have Letters Digits Hyphen" and is the set LDH labels that do not have
"--" characters in the third and forth character position, which "--" characters in the third and forth character position, which
excludes "tagged domain names" such as A-labels. Consistent with the excludes "tagged domain names" such as A-labels. Consistent with the
treatment of rfc822Name in [RFC5280], SmtpUTF8Name is an envelope treatment of rfc822Name in [RFC5280], SmtpUTF8Name is an envelope
<Mailbox> and has no phrase (such as a common name) before it, has no <Mailbox> and has no phrase (such as a common name) before it, has no
comment (text surrounded in parentheses) after it, and is not comment (text surrounded in parentheses) after it, and is not
surrounded by "<" and ">". surrounded by "<" and ">".
Due to operational reasons to be described shortly and name Due to operational reasons to be described shortly and name
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anywhere else that these are used. anywhere else that these are used.
5. Matching of Internationalized Email Addresses in X.509 certificates 5. Matching of Internationalized Email Addresses in X.509 certificates
In equivalence comparison with SmtpUTF8Name, there may be some setup In equivalence comparison with SmtpUTF8Name, there may be some setup
work on one or both inputs depending of whether the input is already work on one or both inputs depending of whether the input is already
in comparison form. Comparing SmtpUTF8Names consists of a domain in comparison form. Comparing SmtpUTF8Names consists of a domain
part step and a local-part step. The comparison form for local-parts 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 always is UTF-8. The comparison form for domain parts depends on
context. While some contexts such as certificate path validation in context. While some contexts such as certificate path validation in
[RFC5280] specify transforming domain to A-label (section 7.5 and 7.2 [RFC5280] specify transforming domain to A-label (Section 7.5 and 7.2
in [RFC5280]), this document RECOMMENDS transforming to UTF-8 U-label in [RFC5280] as updated by [ID-lamps-rfc5280-i18n-update]), this
instead. This reduces the likelihood of errors by reducing document RECOMMENDS transforming to UTF-8 U-label instead. This
conversions as more implementations natively support U- label reduces the likelihood of errors by reducing conversions as more
domains. implementations natively support U- label domains.
Comparison of two SmtpUTF8Name is straightforward with no setup work Comparison of two SmtpUTF8Name is straightforward with no setup work
needed. They are considered equivalent if there is an exact octet- needed. They are considered equivalent if there is an exact octet-
for-octet match. Comparison with email addresses such as for-octet match. Comparison with email addresses such as
Internationalized email address or rfc822Name requires additional Internationalized email address or rfc822Name requires additional
setup steps for domain part and local-part. The initial preparation setup steps for domain part and local-part. The initial preparation
for the email addresses is to remove any phrases or comments, as well for the email addresses is to remove any phrases or comments, as well
as "<" and ">" present. This document calls for comparison of domain as "<" and ">" present. This document calls for comparison of domain
labels that include non-ASCII characters be tranformed to U-label if 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 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, A-label by using Section 5.1 of [RFC5891]. Next if necessary,
transform any A-labels to U-labels Unicode as specified in section transform any A-labels to U-labels Unicode as specified in
5.2 of [RFC5891]. Finally if necessary convert the Unicode to UTF-8 Section 5.2 of [RFC5891]. Finally if necessary convert the Unicode
as specified in section 3 of [RFC3629]. For ASCII NR-LDH labels, to UTF-8 as specified in Section 3 of [RFC3629]. For ASCII NR-LDH
upper case letters are converted to lower case letters. In setup for labels, upper case letters are converted to lower case letters. In
SmtpUTF8Mailbox, the email address local-part MUST conform to the setup for SmtpUTF8Mailbox, the email address local-part MUST conform
requirements of [RFC6530] and [RFC6531], including being a string in to the requirements of [RFC6530] and [RFC6531], including being a
UTF-8 form. In particular, the local-part MUST NOT be transformed in string in UTF-8 form. In particular, the local-part MUST NOT be
any way, such as by doing case folding or normalization of any kind. transformed in any way, such as by doing case folding or
The <Local-part> part of an Internationalized email address is normalization of any kind. The <Local-part> part of an
already in UTF-8. For rfc822Name the local-part, which is IA5String Internationalized email address is already in UTF-8. For rfc822Name
(ASCII), trivially maps to UTF-8 without change. Once setup is the local-part, which is IA5String (ASCII), trivially maps to UTF-8
complete, they are again compared octet-for-octet. without change. Once setup is complete, they are again compared
octet-for-octet.
To summarize non-normatively, the comparison steps including setup To summarize non-normatively, the comparison steps including setup
are: are:
1. If the domain contains A-labels, transform them to U-labels. 1. If the domain contains A-labels, transform them to U-labels.
2. If the domain contains ASCII NR-LDH labels, lowercase them. 2. If the domain contains ASCII NR-LDH labels, lowercase them.
3. Compare strings octet-for-octet for equivalence. 3. Compare strings octet-for-octet for equivalence.
This specification expressly does not define any wildcard characters This specification expressly does not define any wildcard characters
and SmtpUTF8Name comparison implementations MUST NOT interpret any and SmtpUTF8Name comparison implementations MUST NOT interpret any
character as wildcards. Instead, to specify multiple email addresses character as wildcards. Instead, to specify multiple email addresses
through SmtpUTF8Name, the certificate MUST use multiple through SmtpUTF8Name, the certificate MUST use multiple
subjectAltNames or issuerAltNames to explicitly carry any additional subjectAltNames or issuerAltNames to explicitly carry any additional
email addresses. email addresses.
6. Name constraints in path validation 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 rfc822Name name constraints to SmtpUTF8Name subjectAltNames. A
SmtpUTF8Name aware path validators will apply name constraint SmtpUTF8Name aware path validators will apply name constraint
comparison to the subject distinguished name and both forms of comparison to the subject distinguished name and both forms of
subject alternative name rfc822Name and SmtpUTF8Name. subject alternative name rfc822Name and SmtpUTF8Name.
Both rfc822Name and SmtpUTF8Name subject alternative names represent Both rfc822Name and SmtpUTF8Name subject alternative names represent
the same underlying email address namespace. Since legacy CAs the same underlying email address namespace. Since legacy CAs
constrained to issue certificates for a specific set of domains would constrained to issue certificates for a specific set of domains would
lack corresponding UTF-8 constraints, this specification modifies and lack corresponding UTF-8 constraints, [ID-lamps-rfc5280-i18n-update]
extends rfc822Name name SmtpUTF8Name does not violate existing name updates modifies and extends rfc822Name name constraints defined in
constraints. Since it is not valid to include non-ASCII UTF-8 [RFC5280] to cover SmtpUTF8Name subject alternative names. This
characters in the local-part of rfc822Name name constraints, and ensures that the introduction of SmtpUTF8Name does not violate
since name constraints that include a local-part are rarely, if at existing name constraints. Since it is not valid to include non-
all, used in practice, this specification modifies [RFC5280] name ASCII UTF-8 characters in the local-part of rfc822Name name
constraints to only admit the forms represent all addresses at a host constraints, and since name constraints that include a local-part are
or all mailboxes in a domain, and deprecates rfc822Name name rarely, if at all, used in practice, name constraints updated in
constraints that represent a particular mailbox. That is, rfc822Name [ID-lamps-rfc5280-i18n-update] admit the forms that represent all
constraints with a local-part SHOULD NOT be used. 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 Constraint comparison with SmtpUTF8Name subjectAltName starts with
the setup steps defined by Section 5. Setup converts the inputs of the setup steps defined by Section 5. Setup converts the inputs of
the comparison which is one of a subject distinguished name or a the comparison which is one of a subject distinguished name or a
rfc822Name or SmtpUTF8Name subjectAltName, and one of a rfc822Name rfc822Name or SmtpUTF8Name subjectAltName, and one of a rfc822Name
name constraint, to constraint comparison form. For rfc822Name name name constraint, to constraint comparison form. For rfc822Name name
constraint, this will convert any domain A-labels to U-labels. For constraint, this will convert any domain A-labels to U-labels. For
both the name constraint and the subject, this will lower case any both the name constraint and the subject, this will lower case any
domain NR-LDH labels. Strip the local-part and "@" separator from domain NR-LDH labels. Strip the local-part and "@" separator from
each rfc822Name and SmtpUTF8Name, leaving just the domain-part. each rfc822Name and SmtpUTF8Name, leaving just the domain-part.
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in Section 8 in [RFC5280] , but introduces a new issue by permitting in Section 8 in [RFC5280] , but introduces a new issue by permitting
non-ASCII characters in the email address local-part. This issue, as 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], 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 is that use of Unicode introduces the risk of visually similar and
identical characters which can be exploited to deceive the recipient. identical characters which can be exploited to deceive the recipient.
The former document references some means to mitigate against these The former document references some means to mitigate against these
attacks. attacks.
8. IANA Considerations 8. IANA Considerations
in Section Section 3 and the ASN.1 module identifier defined in In Section 3 and the ASN.1 module identifier defined in Appendix A.
Section Appendix A. IANA is kindly requested to make the following IANA is kindly requested to make the following assignments for:
assignments for:
The LAMPS-EaiAddresses-2016 ASN.1 module in the "SMI Security 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). PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).
The SmtpUTF8Name otherName in the "PKIX Other Name Forms" registry The SmtpUTF8Name otherName in the "PKIX Other Name Forms" registry
(1.3.6.1.5.5.7.8). (1.3.6.1.5.5.7.8).
9. References 9. References
9.1. Normative References 9.1. Normative References
[ID-lamps-rfc5280-i18n-update]
Housley, R., "Internationalization Updates to RFC 5280",
June 2017, <https://datatracker.ietf.org/doc/draft-
housley-rfc5280-i18n-update/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>. 2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
skipping to change at page 10, line 43 skipping to change at page 10, line 43
on-SmtpUTF8Name OTHER-NAME ::= { on-SmtpUTF8Name OTHER-NAME ::= {
SmtpUTF8Name IDENTIFIED BY id-on-SmtpUTF8Name SmtpUTF8Name IDENTIFIED BY id-on-SmtpUTF8Name
} }
id-on-SmtpUTF8Name OBJECT IDENTIFIER ::= { id-on 9 } id-on-SmtpUTF8Name OBJECT IDENTIFIER ::= { id-on 9 }
SmtpUTF8Name ::= UTF8String (SIZE (1..MAX)) SmtpUTF8Name ::= UTF8String (SIZE (1..MAX))
END END
Figure 2
Appendix B. Example of SmtpUTF8Name Appendix B. Example of SmtpUTF8Name
This non-normative example demonstrates using SmtpUTF8Name as an This non-normative example demonstrates using SmtpUTF8Name as an
otherName in GeneralName to encode the email address otherName in GeneralName to encode the email address
"u+8001u+5E2B@example.com". "u+8001u+5E2B@example.com".
The hexadecimal DER encoding of the email address is: The hexadecimal DER encoding of the email address is:
A022060A 2B060105 05070012 0809A014 0C12E880 81E5B8AB 40657861 A022060A 2B060105 05070012 0809A014 0C12E880 81E5B8AB 40657861
6D706C65 2E636F6D 6D706C65 2E636F6D
The text decoding is: The text decoding is:
0 34: [0] { 0 34: [0] {
2 10: OBJECT IDENTIFIER '1 3 6 1 5 5 7 0 18 8 9' 2 10: OBJECT IDENTIFIER '1 3 6 1 5 5 7 0 18 8 9'
14 20: [0] { 14 20: [0] {
16 18: UTF8String '..@example.com' 16 18: UTF8String '..@example.com'
: } : }
: } : }
Figure 3 Figure 2
The example was encoded on the OSS Nokalva ASN.1 Playground and the The example was encoded on the OSS Nokalva ASN.1 Playground and the
above text decoding is an output of Peter Gutmann's "dumpasn1" above text decoding is an output of Peter Gutmann's "dumpasn1"
program. program.
Appendix C. Acknowledgements Appendix C. Acknowledgements
Thank you to Magnus Nystrom for motivating this document. Thanks to Thank you to Magnus Nystrom for motivating this document. Thanks to
Russ Housley, Nicolas Lidzborski, Laetitia Baudoin, Ryan Sleevi, Sean Russ Housley, Nicolas Lidzborski, Laetitia Baudoin, Ryan Sleevi, Sean
Leonard, Sean Turner, John Levine, and Patrik Falstrom for their Leonard, Sean Turner, John Levine, and Patrik Falstrom for their
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