Internet DRAFT - draft-ietf-sipcore-name-addr-guidance
draft-ietf-sipcore-name-addr-guidance
Network Working Group R. Sparks
Internet-Draft Oracle
Updates: 3261, 3325, 3515, 3892, 4508, June 01, 2017
5002, 5318, 5360, 5502 (if
approved)
Intended status: Standards Track
Expires: December 3, 2017
Clarifications for when to use the name-addr production in SIP messages
draft-ietf-sipcore-name-addr-guidance-02
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 the RFCs that define extension SIP header fields using
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
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 3, 2017.
Sparks Expires December 3, 2017 [Page 1]
Internet-Draft Name-addr Clarifications June 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
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Updates to RFC3261 . . . . . . . . . . . . . . . . . . . . . 3
4. Updates to RFCs defining SIP Extension header fields . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
8. Instructions to the RFC Editor . . . . . . . . . . . . . . . 5
9. 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.
Sparks Expires December 3, 2017 [Page 2]
Internet-Draft Name-addr Clarifications June 2017
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 very likely
be interpreted differently. The characters after the comma, question
mark, or semicolon will, in most cases, be interpreted as header
field parameters or additional header field values as discussed in
section 7.3.1 of [RFC3261]. (An exception is the degenerate case of
a URL like sip:10.0.0.1,@10.0.0.0 where it is possible to parse the
comma via the 'user' production).
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Updates to RFC3261
This text from the introduction to section 20 of [RFC3261]:
Sparks Expires December 3, 2017 [Page 3]
Internet-Draft Name-addr Clarifications June 2017
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 >). Any URI parameters are
contained within these brackets. If the URI is not enclosed in
angle brackets, any semicolon-delimited parameters are
header-parameters, not URI parameters.
is replaced with:
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.
When a URI appears in such a header field, any URI parameters MUST
be contained within angle brackets (< and >). If the URI is not
enclosed in angle brackets, any semicolon-delimited parameters are
header-parameters, not URI parameters.
The header fields defined in this specification that allow this
choice are "To", "From", "Contact", and "Reply-To".
4. 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.
5. IANA Considerations
This memo has no considerations for IANA.
Sparks Expires December 3, 2017 [Page 4]
Internet-Draft Name-addr Clarifications June 2017
6. 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 very likely be
mis-interpreted by the receiving element.
7. 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, Dale Worley, and
Yehoshua Gev.
8. 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.
9. 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>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
Sparks Expires December 3, 2017 [Page 5]
Internet-Draft Name-addr Clarifications June 2017
[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>.
[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
Sparks Expires December 3, 2017 [Page 6]
