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Versions: (draft-camarillo-sipping-consent-format) 00 01 02 03 04 05 06 07 08 RFC 5361

SIPPING                                                     G. Camarillo
Internet-Draft                                                  Ericsson
Intended status: Standards Track                          April 24, 2007
Expires: October 26, 2007


                A Document Format for Requesting Consent
                draft-ietf-sipping-consent-format-03.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document defines an Extensible Markup Language (XML) format for
   a permission document used to request consent.  A permission document
   written in this format is used by a relay to request a specific
   recipient permission to perform a particular routing translation.







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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Definitions and Terminology  . . . . . . . . . . . . . . . . .  3
   3.  Permission Document Structure  . . . . . . . . . . . . . . . .  3
     3.1.  Conditions . . . . . . . . . . . . . . . . . . . . . . . .  4
       3.1.1.  Identity Condition . . . . . . . . . . . . . . . . . .  4
       3.1.2.  Sender Condition . . . . . . . . . . . . . . . . . . .  5
       3.1.3.  Target Condition . . . . . . . . . . . . . . . . . . .  7
     3.2.  Actions  . . . . . . . . . . . . . . . . . . . . . . . . .  7
       3.2.1.  Translation Handling . . . . . . . . . . . . . . . . .  7
   4.  Example Document . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  XML Namespace Registration . . . . . . . . . . . . . . . .  9
     6.2.  XML Schema Registration  . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13




























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1.  Introduction

   The framework for consent-based communications in the Session
   Initiation Protocol (SIP) [9] identifies the need for a format to
   create permission documents.  Such permission documents are used by
   SIP [3] relays to request permission to perform translations.  A
   relay is defined as any SIP server, be it a proxy, B2BUA (Back-to-
   Back User Agent), or some hybrid, which receives a request and
   translates the request URI into one or more next hop URIs to which it
   then delivers a request.

   The format for permission documents specified in this document is
   based on the XML document format for expressing Privacy Preferences
   [8].


2.  Definitions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

   Relay:  Any SIP server, be it a proxy, B2BUA (Back-to-Back User
      Agent), or some hybrid, that receives a request, translates its
      Request-URI into one or more next-hop URIs (i.e., recipient URIs),
      and delivers the request to those URIs.

   Recipient URI:  The Request-URI of an outgoing request sent by an
      entity (e.g., a user agent or a proxy).  The sending of such
      request may have been the result of a translation operation.

   Target URI:  The Request-URI of an incoming request that arrives to
      an entity (e.g., a proxy) that will perform a translation
      operation.

   Translation operation:  Operation by which an entity (e.g., a proxy)
      translates the request URI of an incoming request (i.e., the
      target URI) into one or more URIs (i.e., recipient URIs) which are
      used as the request URIs of one or more outgoing requests.


3.  Permission Document Structure

   A permission document is an XML document, formatted according to the
   schema defined in [8].  Permission documents inherit the MIME type of
   common policy documents, 'application/auth-policy+xml'.  As described
   in [8], this type of document is composed of three parts: conditions,
   actions, and transformations.  However, even though permission



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   documents need to have a transformation part to comply to the common
   policy syntax, effectively, permission documents do not make any use
   of transformations.

   This section defines the new conditions and actions defined by this
   specification.  This specification does not define any new
   transformation.

3.1.  Conditions

   Note that, as discussed in [8], a permission document applies to a
   translation if all the expressions in its conditions part evaluate to
   TRUE.

3.1.1.  Identity Condition

   The identity condition, defined in [8], is matched against the
   recipient URI of a translation.

   When performing a translation, a relay matches the identity condition
   of the permission document that was used to request permission for
   that translation against the destination URI of the outgoing request.
   When receiving a request granting or denying permissions (e.g., a SIP
   PUBLISH request as described in [9]), the relay matches the identity
   condition of the permission document that was used to request
   permission against the identity of the entity granting or denying
   permissions (i.e., the sender of the PUBLISH request).

   The <identity> element is defined in [8], which indicates that the
   specific usages of the framework document need to define details that
   are protocol and usage specific.  In particular, this section defines
   acceptable means of authentication.

   The 'id' attribute in the elements <one> and <except> MUST contain a
   scheme when these elements appear in a permission document.

   When used with SIP, a recipient granting or denying a relay
   permissions is considered authenticated if one of the following
   techniques is used:

   SIP Identity  [7], as described in [9].  For PUBLISH requests that
      are authenticated using the SIP Identity mechanism, the identity
      of the sender of the PUBLISH request is equal to the SIP URI in
      the From header field of the request, assuming that the signature
      in the Identity header field has been validated.






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   P-Asserted-Identity  [5], as described in [9].  For PUBLISH requests
      that are authenticated using the P-Asserted-Identity mechanism,
      the identity of the sender of the PUBLISH request is equal to the
      P-Asserted-Identity header field of the request.

   Return Routability Test,  as described in [9].

   SIP digest,  as described in [9].

3.1.2.  Sender Condition

   The sender condition is matched against the URI of the sender of the
   request that is used as input for a translation.  Sender conditions
   can contain the same elements and attributes as identity conditions.

   When performing a translation, a relay matches the sender condition
   against the identity of the sender of the incoming request.

   The following subsections define acceptable means of authentication,
   the procedure for representing the identity of the sender as a URI,
   and the procedure for converting an identifier of the form
   user@domain, present in the 'id' attribute of the <one> and <except>
   elements, into a URI.

3.1.2.1.  Acceptable Means of Authentication

   When used with SIP, a request sent by a sender is considered
   authenticated if one of the following techniques is used:

   SIP Digest:  the relay authenticates the sender using SIP digest
      authentication [2].  However, if the anonymous authentication
      described on page 194 of RFC 3261 [3] is used, the sender is not
      considered authenticated.

   Asserted Identity:  if a request contains a P-Asserted-ID header
      field [5] and the request is coming from a trusted element, the
      sender is considered authenticated.

   Cryptographically Verified Identity:  if a request contains an
      Identity header field as defined in [7], and it validates the From
      header field of the request, the request is considered to be
      authenticated.  Note that this is true even if the request
      contained a From header field of the form
      sip:anonymous@example.com.  As long as the signature verifies that
      the request legitimately came from this identity, it is considered
      authenticated.




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3.1.2.2.  Computing a URI for the Sender

   For requests that are authenticated using SIP Digest, the identity of
   the sender is set equal to the SIP Address of Record (AOR) for the
   user that has authenticated themselves.  For example, consider the
   following "user record" in a database:

      SIP AOR: sip:alice@example.com
      digest username: ali
      digest password: f779ajvvh8a6s6
      digest realm: example.com

   If the relay receives a request, challenges it with the realm set to
   "example.com", and the subsequent request contains an Authorization
   header field with a username of "ali" and a digest response generated
   with the password "f779ajvvh8a6s6", the identity used in matching
   operations is "sip:alice@example.com".

   For requests that are authenticated using RFC 3325 [5], the identity
   of the sender is equal to the SIP URI in the P-Asserted-ID header
   field.  If there are multiple values for the P-Asserted-ID header
   field (there can be one sip URI and one tel URI [10]), then each of
   them is used for the comparisons outlined in [8], and if either of
   them match a <one> or <except> element, it is considered a match.

   For requests that are authenticated using the SIP Identity mechanism
   [7], identity of the sender is equal to the SIP URI in the From
   header field of the request, assuming that the signature in the
   Identity header field has been validated.

   SIP also allows for anonymous requests.  If a request is anonymous
   because the digest challenge/response used the "anonymous" username,
   the request is considered unauthenticated and will not match the
   <sender> condition.  If a request is anonymous because it contains a
   Privacy header field [4], but still contains a P-Asserted-ID header
   field, the identity in the P-Asserted-ID header field is still used
   in the authorization computations; the fact that the request was
   anonymous has no impact on the identity processing.  However, if the
   request had traversed a trust boundary and the P-Asserted-ID header
   field and the Privacy header field had been removed, the request will
   be considered unauthenticated when it arrives at the presence server,
   and thus not match the <sender> condition.  Finally, if a request
   contained an Identity header field that was validated, and the From
   header field contained a URI of the form sip:anonymous@example.com,
   then the watcher is considered authenticated, and it will have an
   identity equal to sip:anonymous@example.com.  Had such an identity
   been placed into a <one> or <except> element, there will be a match.




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3.1.2.3.  Computing a SIP URI from the id Attribute

   If the <one> or <except> condition does not contain a scheme,
   conversion of the value in the 'id' attribute to a SIP URI is done
   trivially.  If the characters in the 'id' attribute are valid
   characters for the user and hostpart components of the SIP URI, a
   'sip:' is appended to the contents of the 'id' attribute, and the
   result is the SIP URI.  If the characters in the 'id' attribute are
   not valid for the user and hostpart components of the SIP URI,
   conversion is not possible.  This happens, for example, when the user
   portion of the 'id' attribute contain UTF-8 characters.

3.1.3.  Target Condition

   The target condition is matched against the target URI of a
   translation.  Target conditions can contain the same elements and
   attributes as identity conditions.

   When performing a translation, a relay matches the target condition
   against the destination of the incoming request, which is typically
   contained in the Request-URI.

3.2.  Actions

   The actions in a permission document provide URIs to grant or deny
   permission to perform the translation described in the document.

3.2.1.  Translation Handling

   The <trans-handling> provides URIs for a recipient to grant or deny
   the relay permission to perform a translation.  The defined values
   are:

   deny:  this action tells the relay not to perform the translation.

   grant:  this action tells the server to perform the translation.

   The 'perm-uri' attribute in the <trans-handling> element provides a
   URI to grant or deny permission to perform a translation.


4.  Example Document

   The following permission document is generated by the relay handling
   'sip:alices-friends@example.com' in order to ask for permission to
   relay requests sent to that URI to 'sip:bob@example.org'.





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   <?xml version="1.0" encoding="UTF-8"?>
      <cr:ruleset
       xmlns="urn:ietf:params:xml:ns:consent-rules"
       xmlns:cp="urn:ietf:params:xml:ns:common-policy"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="urn:ietf:params:xml:ns:consent-rules
                          consent-rules.xsd">
       <cp:rule id="1">
        <cp:conditions>
         <cp:identity>
          <cp:one id="sip:bob@example.org"/>
         </cp:identity>
         <target>
          <cp:one id="sip:alices-friends@example.com""/>
         </target>
         <sender>
          <cp:any/>
         </sender>
        </cp:conditions>
        <cp:actions>
         <trans-handling
                perm-uri="sip:foo@example.com">grant</trans-handling>
         <trans-handling
                perm-uri="sip:bar@example.com">deny</trans-handling>
        </cp:actions>
        <cp:transformations/>
       </cp:rule>
      </cp:ruleset>


5.  XML Schema




















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   <?xml version="1.0" encoding="UTF-8"?>
      <xs:schema
        targetNamespace="urn:ietf:params:xml:ns:consent-rules"
        xmlns:cr="urn:ietf:params:xml:ns:consent-rules"
        xmlns:cp="urn:ietf:params:xml:ns:common-policy"
        xmlns:xs="http://www.w3.org/2001/XMLSchema"
        elementFormDefault="qualified"
        attributeFormDefault="unqualified">

        <!-- Conditions -->
        <xs:element name="sender" type="cp:identityType"/>
        <xs:element name="target" type="cp:identityType"/>

       <!-- Actions -->
       <xs:simpleType name="trans-values">
          <xs:restriction base="xs:string">
            <xs:enumeration value="deny"/>
            <xs:enumeration value="grant"/>
          </xs:restriction>
        </xs:simpleType>

        <xs:element name="trans-handling">
          <xs:complexType>
            <xs:simpleContent>
              <xs:extension base="trans-values">
                <xs:attribute name="perm-uri" type="xs:anyURI"
                              use="required"/>
              </xs:extension>
            </xs:simpleContent>
          </xs:complexType>
        </xs:element>

      </xs:schema>



6.  IANA Considerations

   This section registers a new XML namespace and a new XML schema per
   the procedures in [6].

6.1.  XML Namespace Registration

      URI: urn:ietf:params:xml:ns:consent-rules

      Registrant Contact: IETF SIPPING working group,
      <sipping@ietf.org>, Gonzalo Camarillo
      <Gonzalo.Camarillo@ericsson.com>



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      XML:

      BEGIN
      <?xml version="1.0"?>
      <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
        "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
      <html xmlns="http://www.w3.org/1999/xhtml">
      <head>
        <meta http-equiv="content-type"
              content="text/html;charset=iso-8859-1"/>
        <title>Consent Rules Namespace</title>
      </head>
      <body>
        <h1>Namespace for Permission Documents</h1>
        <h2>urn:ietf:params:xml:ns:consent-rules</h2>
      <p>See <a href="[URL of published RFC]">RFCXXXX
          [NOTE TO IANA/RFC-EDITOR:
           Please replace XXXX with the RFC number of this
          specification.]</a>.</p>
      </body>
      </html>
      END

6.2.  XML Schema Registration

      URI: urn:ietf:params:xml:schema:consent-rules

      Registrant Contact: IETF SIPPING working group,
      <sipping@ietf.org>, Gonzalo Camarillo
      <Gonzalo.Camarillo@ericsson.com>

      XML: The XML schema to be registered is contained in Section 5.


7.  Security Considerations

   Permission documents can reveal sensitive information.  Additionally,
   attackers may attempt to modify them in order to have clients grant
   or deny permissions different to the ones they think are granting or
   denying.  For this reason, it is RECOMMENDED that relays use strong
   means for information integrity protection and confidentiality when
   sending permission documents to clients.

   The mechanism used for conveying information to clients SHOULD ensure
   the integrity and confidentially of the information.  In order to
   achieve these, an end-to-end SIP encryption mechanism, such as
   S/MIME, as described in RFC 3261 [3], SHOULD be used.




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   If strong end-to-end security means (such as above) is not available,
   it is RECOMMENDED that hop-by-hop security based on TLS and SIPS
   URIs, as described in [3], is used.


8.  Acknowledgements

   Jonathan Rosenberg provided useful ideas on this document.  Ben
   Campbell and Mary Barnes performed a thorough review of this
   document.


9.  References

9.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
         Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication:
         Basic and Digest Access Authentication", RFC 2617, June 1999.

   [3]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [4]   Peterson, J., "A Privacy Mechanism for the Session Initiation
         Protocol (SIP)", RFC 3323, November 2002.

   [5]   Jennings, C., Peterson, J., and M. Watson, "Private Extensions
         to the Session Initiation Protocol (SIP) for Asserted Identity
         within Trusted Networks", RFC 3325, November 2002.

   [6]   Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
         January 2004.

   [7]   Peterson, J. and C. Jennings, "Enhancements for Authenticated
         Identity Management in the Session Initiation Protocol (SIP)",
         RFC 4474, August 2006.

   [8]   Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., Polk,
         J., and J. Rosenberg, "Common Policy: A Document Format for
         Expressing Privacy Preferences", RFC 4745, February 2007.

   [9]   Rosenberg, J., "A Framework for Consent-Based Communications in
         the Session Initiation  Protocol (SIP)",
         draft-ietf-sip-consent-framework-01 (work in progress),



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         November 2006.

9.2.  Informative References

   [10]  Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
         December 2004.


Author's Address

   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com


































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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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