Internet DRAFT - draft-sparks-sipcore-name-addr-guidance
draft-sparks-sipcore-name-addr-guidance
Network Working Group R. Sparks
Internet-Draft Oracle
Updates: 3261, 3325, 3515, 3892, 4508, September 27, 2016
5002, 5318, 5360, 5502 (if
approved)
Intended status: Standards Track
Expires: March 31, 2017
Clarifications for when to use the name-addr production in SIP messages
draft-sparks-sipcore-name-addr-guidance-01
Abstract
RFC3261 constrained several SIP header fields whose grammar contains
the "name-addr / addr-spec" alternative to use name-addr when certain
characters appear. Unfortunately it expressed the constraints with
prose copied into each header field definition, and at least one
header field was missed. Further, the constraint has not been copied
into documents defining extension headers whose grammar contains the
alternative.
This document updates RFC3261 to state the constraint generically,
and clarifies that the constraint applies to all SIP header fields
where there is a choice between using name-addr or addr-spec. It
also updates those extension SIP header fields that use the
alternative to clarify that the constraint applies (RFCs 3325, 3515,
3892, 4508, 5002, 5318, 5360, and 5502).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 31, 2017.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Updates to RFC3261 . . . . . . . . . . . . . . . . . . . . . 3
3. Updates to RFCs defining SIP Extension header fields . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
7. Instructions to the RFC Editor . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[RFC3261] defines several header fields that contain URIs to allow
both a form that contains the bare URI (addr-spec) and one that
provides a name and the URI (name-addr). This subset, taken from the
ABNF [RFC5234] specified in [RFC3261] shows the relevant part of the
definition of the syntax of the "From" header field:
From = ( "From" / "f" ) HCOLON from-spec
from-spec = ( name-addr / addr-spec )
*( SEMI from-param )
name-addr = [ display-name ] LAQUOT addr-spec RAQUOT
addr-spec = SIP-URI / SIPS-URI / absoluteURI
The prose in section 20.20 of [RFC3261], which discusses the "From"
header field, constrains how the production may be used by saying:
Even if the "display-name" is empty, the "name-addr" form
MUST be used if the "addr-spec" contains a comma, question
mark, or semicolon.
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Section 20.39, which discusses the "To" header field contains no such
constraining text.
This constraint is specified slightly differently, but with the same
intent, in the introduction to section 20:
The Contact, From, and To header fields contain a URI. If the URI
contains a comma, question mark or semicolon, the URI MUST be
enclosed in angle brackets (< and >).
Unfortunately, this can be read to only apply to the Contact, From,
and To header fields, making it necessary to provide the constraint
explicitly in the prose discussing any other header field using the
name-addr or addr-spec alternative.
As extension header fields were standardized, the specifications
sometimes failed to include the constraint. Many errata have been
entered to correct this omission. When the constraint was called
out, the form has not been consistent.
This memo updates the specifications of SIP and its extensions to
clarify that the constraint to use the name-addr form applies
anywhere there is a choice between the name-addr and addr-spec
production rules in the grammar for SIP header fields.
It is important to note that a message formed without honoring the
constraint will still be syntactically valid, but would be
interpreted differently. The characters after the comma, question
mark, or semicolon would be interpreted as header field parameters or
additional header field values as discussed in section 7.3.1 of
[RFC3261].
2. Updates to RFC3261
This text from the introduction to section 20 of [RFC3261]:
The Contact, From, and To header fields contain a URI. If the URI
contains a comma, question mark or semicolon, the URI MUST be
enclosed in angle brackets (< and >).
is replaced with:
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When constructing the value of any SIP header field whose grammar
allows choosing between name-addr and addr-spec, such as those
that use the form '(name-addr / addr-spec)', the "addr-spec" form
MUST NOT be used if its value would contain a comma, semicolon,
or question mark.
The header fields defined in this specification that allow this
choice are "To", "From", "Contact", and "Reply-To".
3. Updates to RFCs defining SIP Extension header fields
The following standards track RFCs: [RFC3515], [RFC3892], [RFC4508],
and [RFC5360]
and the following informational RFCS: [RFC3325], [RFC5002],
[RFC5318], and [RFC5502]
are updated to include:
This RFC contains the definition of one or more SIP header fields
that allow choosing between addr-spec and name-addr when
constructing header field values. As specified in RFCxxxx,
the "addr-spec" form MUST NOT be used if its value would contain
a comma, semicolon, or question mark.
The status of the Informational RFCs remains Informational.
4. IANA Considerations
This memo has no considerations for IANA.
5. Security Considerations
The updates specified in this memo clarify a constraint on the
grammar for producing SIP messages. It introduces no new security
considerations. One pre-existing consideration is worth reiterating:
messages produced without honoring the constraint will be mis-
interpreted by the receiving element.
6. Acknowledgments
Brett Tate identified this issue in several extension documents,
submitted several corresponding errata, and drove the discussion that
led to this memo. Substantive comments leading to this text were
provided by Paul Kyzivat, Gonzalo Camarillo, and Dale Worley.
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7. Instructions to the RFC Editor
Please remove this section in its entirety before publication as an
RFC.
Please replace any instances of RFCxxxx with the RFC number assigned
to this memo.
This memo, if it is approved, obviates Errata 3744, 3894, and
4648-4652 inclusive.
8. Normative References
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, DOI 10.17487/RFC3515, April 2003,
<http://www.rfc-editor.org/info/rfc3515>.
[RFC3892] Sparks, R., "The Session Initiation Protocol (SIP)
Referred-By Mechanism", RFC 3892, DOI 10.17487/RFC3892,
September 2004, <http://www.rfc-editor.org/info/rfc3892>.
[RFC4508] Levin, O. and A. Johnston, "Conveying Feature Tags with
the Session Initiation Protocol (SIP) REFER Method",
RFC 4508, DOI 10.17487/RFC4508, May 2006,
<http://www.rfc-editor.org/info/rfc4508>.
[RFC5360] Rosenberg, J., Camarillo, G., Ed., and D. Willis, "A
Framework for Consent-Based Communications in the Session
Initiation Protocol (SIP)", RFC 5360,
DOI 10.17487/RFC5360, October 2008,
<http://www.rfc-editor.org/info/rfc5360>.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
DOI 10.17487/RFC3325, November 2002,
<http://www.rfc-editor.org/info/rfc3325>.
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[RFC5002] Camarillo, G. and G. Blanco, "The Session Initiation
Protocol (SIP) P-Profile-Key Private Header (P-Header)",
RFC 5002, DOI 10.17487/RFC5002, August 2007,
<http://www.rfc-editor.org/info/rfc5002>.
[RFC5318] Hautakorpi, J. and G. Camarillo, "The Session Initiation
Protocol (SIP) P-Refused-URI-List Private-Header
(P-Header)", RFC 5318, DOI 10.17487/RFC5318, December
2008, <http://www.rfc-editor.org/info/rfc5318>.
[RFC5502] van Elburg, J., "The SIP P-Served-User Private-Header
(P-Header) for the 3GPP IP Multimedia (IM) Core Network
(CN) Subsystem", RFC 5502, DOI 10.17487/RFC5502, April
2009, <http://www.rfc-editor.org/info/rfc5502>.
Author's Address
Robert Sparks
Oracle
Email: rjsparks@nostrum.com
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