English

Whois.SmartWeb.CZ

RFC 8217 - úplné znění

Plné znění RFC 8217:






Internet Engineering Task Force (IETF)                         R. Sparks
Request for Comments: 8217                                        Oracle
Updates: 3261, 3325, 3515, 3892, 4508,                       August 2017
         5002, 5318, 5360, 5502
Category: Standards Track
ISSN: 2070-1721


Clarifications for When to Use the name-addr Production in SIP Messages

Abstract

   RFC 3261 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 RFC 3261 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 is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/RFC 8217.











Sparks                       Standards Track                    [Page 1]

RFC 8217 name-addr Clarifications August 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 RFC 3261 . . . . . . . . . . . . . . . . . . . . . 4 4. Updates to RFCs Defining SIP Extension Header Fields . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction [RFC 3261] 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 [RFC 5234] specified in [RFC 3261], 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 [RFC 3261], 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 Standards Track [Page 2]
RFC 8217 name-addr Clarifications August 2017 Section 20.39 of [RFC 3261], 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 of [RFC 3261]: 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 has been included, the requirement to use the name-addr form has not been consistently stated. 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 it 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 [RFC 3261]. (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 [RFC 2119] [RFC 8174] when, and only when, they appear in all capitals, as shown here. Sparks Standards Track [Page 3]
RFC 8217 name-addr Clarifications August 2017 3. Updates to RFC 3261 This text from introduction to Section 20 of [RFC 3261]: 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: [RFC 3515], [RFC 3892], [RFC 4508], and [RFC 5360] and the following Informational RFCs: [RFC 3325], [RFC 5002], [RFC 5318], and [RFC 5502] 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 RFC 8217, the "addr-spec" form MUST NOT be used if its value would contain a comma, semicolon, or question mark. The status of these RFCs remains unchanged. In particular the status of the Informational RFCs remains Informational. Sparks Standards Track [Page 4]
RFC 8217 name-addr Clarifications August 2017 5. IANA Considerations This document does not require any IANA actions. 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 misinterpreted by the receiving element. 7. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC 2119, March 1997, <http://www.rfc-editor.org/info/RFC 2119>. [RFC 3261] 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/RFC 3261, June 2002, <http://www.rfc-editor.org/info/RFC 3261>. [RFC 3325] 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/RFC 3325, November 2002, <http://www.rfc-editor.org/info/RFC 3325>. [RFC 3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, DOI 10.17487/RFC 3515, April 2003, <http://www.rfc-editor.org/info/RFC 3515>. [RFC 3892] Sparks, R., "The Session Initiation Protocol (SIP) Referred-By Mechanism", RFC 3892, DOI 10.17487/RFC 3892, September 2004, <http://www.rfc-editor.org/info/RFC 3892>. [RFC 4508] Levin, O. and A. Johnston, "Conveying Feature Tags with the Session Initiation Protocol (SIP) REFER Method", RFC 4508, DOI 10.17487/RFC 4508, May 2006, <http://www.rfc-editor.org/info/RFC 4508>. [RFC 5002] Camarillo, G. and G. Blanco, "The Session Initiation Protocol (SIP) P-Profile-Key Private Header (P-Header)", RFC 5002, DOI 10.17487/RFC 5002, August 2007, <http://www.rfc-editor.org/info/RFC 5002>. Sparks Standards Track [Page 5]
RFC 8217 name-addr Clarifications August 2017 [RFC 5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC 5234, January 2008, <http://www.rfc-editor.org/info/RFC 5234>. [RFC 5318] Hautakorpi, J. and G. Camarillo, "The Session Initiation Protocol (SIP) P-Refused-URI-List Private-Header (P-Header)", RFC 5318, DOI 10.17487/RFC 5318, December 2008, <http://www.rfc-editor.org/info/RFC 5318>. [RFC 5360] 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/RFC 5360, October 2008, <http://www.rfc-editor.org/info/RFC 5360>. [RFC 5502] 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/RFC 5502, April 2009, <http://www.rfc-editor.org/info/RFC 5502>. [RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174, May 2017, <http://www.rfc-editor.org/info/RFC 8174>. 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. Author's Address Robert Sparks Oracle Email: rjsparks@nostrum.com Sparks Standards Track [Page 6]


English version: RFC 8217