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rfc:rfc5361

Network Working Group G. Camarillo Request for Comments: 5361 Ericsson Category: Standards Track October 2008

              A Document Format for Requesting Consent

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

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.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
 2.  Definitions and Terminology  . . . . . . . . . . . . . . . . .  2
 3.  Permission Document Structure  . . . . . . . . . . . . . . . .  3
   3.1.  Conditions . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.1.  Recipient Condition  . . . . . . . . . . . . . . . . .  3
     3.1.2.  Identity Condition . . . . . . . . . . . . . . . . . .  4
     3.1.3.  Target Condition . . . . . . . . . . . . . . . . . . .  6
     3.1.4.  Validity Condition . . . . . . . . . . . . . . . . . .  7
     3.1.5.  Sphere Condition . . . . . . . . . . . . . . . . . . .  7
   3.2.  Actions  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.1.  Translation Handling . . . . . . . . . . . . . . . . .  7
 4.  Example Document . . . . . . . . . . . . . . . . . . . . . . .  7
 5.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 10
 6.  Extensibility  . . . . . . . . . . . . . . . . . . . . . . . . 10
 7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   7.1.  XML Namespace Registration . . . . . . . . . . . . . . . . 11
   7.2.  XML Schema Registration  . . . . . . . . . . . . . . . . . 11
 8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
 9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
   10.2. Informative References . . . . . . . . . . . . . . . . . . 13

Camarillo Standards Track [Page 1] RFC 5361 Permission Document Format October 2008

1. Introduction

 The framework for consent-based communications in the Session
 Initiation Protocol (SIP) [RFC5360] identifies the need for a format
 to create permission documents.  Such permission documents are used
 by SIP [RFC3261] 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 Common Policy [RFC4745], an XML document format for
 expressing privacy preferences.

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 [RFC2119].
 This document uses the terms defined in [RFC5360].  For completeness,
 these terms are repeated here.  Figure 1 of [RFC5360] shows the
 relationship between target and recipient URIs in a translation
 operation.
 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 can have been
    the result of a translation operation.
 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.
 Target URI:
    The Request-URI of an incoming request that arrives to a relay
    that will perform a translation operation.
 Translation logic:
    The logic that defines a translation operation at a relay.  This
    logic includes the translation's target and recipient URIs.

Camarillo Standards Track [Page 2] RFC 5361 Permission Document Format October 2008

 Translation operation:
    Operation by which a relay translates the Request-URI of an
    incoming request (i.e., the target URI) into one or more URIs
    (i.e., recipient URIs) that 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 [RFC4745].  Permission documents inherit the MIME
 type of common policy documents, 'application/auth-policy+xml'.  As
 described in [RFC4745], this type of document is composed of three
 parts: conditions, actions, and transformations.
 This section defines the new conditions and actions defined by this
 specification.  This specification does not define any new
 transformation.

3.1. Conditions

 The conditions in a permission document are a set of expressions,
 each of which evaluates to either TRUE or FALSE.  Note that, as
 discussed in [RFC4745], a permission document applies to a
 translation if all the expressions in its conditions part evaluate to
 TRUE.

3.1.1. Recipient Condition

 The recipient condition is matched against the recipient URI of a
 translation.  Recipient conditions can contain the same elements and
 attributes as identity conditions.
 When performing a translation, a relay matches the recipient
 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 [RFC5360]),
 the relay matches the recipient 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).  If there is a match, the recipient condition
 evaluates to TRUE.  Otherwise, the recipient condition evaluates to
 FALSE.
 Since only authenticated identities can be matched, this section
 defines acceptable means of authentication, which are in line with
 those described in Section 5.6.1 of [RFC5360].

Camarillo Standards Track [Page 3] RFC 5361 Permission Document Format October 2008

 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  [RFC4474], as described in Section 5.6.1.1 of
    [RFC5360].  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.
 P-Asserted-Identity  [RFC3325] (which can only be used in closed
    network environments) as described in Section 5.6.1.2 of
    [RFC5360].  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 Section 5.6.1.3 of
    [RFC5360].  It can be used for SIP PUBLISH and HTTP GET requests.
    No authentication is expected to be used with return routability
    tests and, therefore, no identity matching procedures are defined.
 SIP digest, as described in Section 5.6.1.4 of [RFC5360].  The
    identity of the sender is set equal to the SIP Address of Record
    (AOR) for the user that has authenticated themselves.

3.1.2. Identity Condition

 The identity condition, which is defined in [RFC4745], is matched
 against the URI of the sender of the request that is used as input
 for a translation.
 When performing a translation, a relay matches the identity condition
 against the identity of the sender of the incoming request.  If they
 match, the identity condition evaluates to TRUE.  Otherwise, the
 identity condition evaluates to FALSE.
 Since only authenticated identities can be matched, 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.

Camarillo Standards Track [Page 4] RFC 5361 Permission Document Format October 2008

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 [RFC2617].  However, if the anonymous
    authentication described on page 194 of [RFC3261] is used, the
    sender is not considered authenticated.
 Asserted Identity:  if a request contains a P-Asserted-ID header
    field [RFC3325] 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 [RFC4474], 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.

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 and 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 [RFC3325], 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 [RFC3966]), then each of
 them is used for the comparisons outlined in [RFC4745]; if either of
 them match a <one> or <except> element, it is considered a match.

Camarillo Standards Track [Page 5] RFC 5361 Permission Document Format October 2008

 For requests that are authenticated using the SIP Identity mechanism
 [RFC4474], 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
 <identity> condition.  If a request is anonymous because it contains
 a Privacy header field [RFC3323], 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 relay, 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
 sender 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.

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 and, thus, the identity condition
 evaluates to FALSE.  This happens, for example, when the user portion
 of the 'id' attribute contains UTF-8 characters.

3.1.3. Target Condition

 The target condition is matched against the target URI of a
 translation.  The target condition 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.  If they match, the target condition
 evaluates to TRUE.  Otherwise, the target condition evaluates to
 FALSE.

Camarillo Standards Track [Page 6] RFC 5361 Permission Document Format October 2008

3.1.4. Validity Condition

 The <validity> element is not applicable to this document.  Each
 <permission> element has an infinite lifetime and can be revoked
 using an independent mechanism, as described in Section 5.8 of
 [RFC5360].  In any case, as discussed in Section 4.1 of [RFC5360],
 permissions are only valid as long as the context where they were
 granted is valid.  If present, <validity> elements MUST be ignored.

3.1.5. Sphere Condition

 The <sphere> element is not applicable to this document and therefore
 is not used.  If present, <sphere> elements MUST be ignored.

3.2. Actions

 The actions in a permission document provide URIs to grant or deny
 permission to perform the translation described in the document.
    Note that the <trans-handling> element is not an action, as
    defined in Common Policy [RFC4745], but rather an informational
    element.  Therefore, the conflict resolution mechanism does not
    apply to it.
 Each policy rule contains at least two <trans-handling> elements; one
 element with a URI to grant and another with a URI to deny
 permission.

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

 In the following example, a client adds 'sip:bob@example.org' to the
 translation whose target URI is 'sip:alices-friends@example.com'.
 The relay handling the translation generates the following permission
 document in order to ask for permission to relay requests sent to
 'sip:alices-friends@example.com' to 'sip:bob@example.org'.  The

Camarillo Standards Track [Page 7] RFC 5361 Permission Document Format October 2008

 target URI is 'sip:alices-friends@example.com', and the recipient URI
 is 'sip:bob@example.org'.  The sender's identity does not play a role
 in this example.  Therefore, the permission document does not put any
 restriction on potential senders.
+--------+        +--------------------------------+  Permission
|        |        |                                |   Request
| Client |        |             Relay              |    with
|        |        | sip:alices-friends@example.com |  Permission
+--------+        |                                |   Document
    |             |+-------+                       |-------------+
    |             ||Transl.|                       |             |
    |Manipulation ||Logic  |                       |             |
    +------------>|+-------+                       |             |
         Add      +--------------------------------+             |
   sip:bob@example.org                                           V
                                               +---------------------+
                                               |                     |
                                               |      Recipient      |
                                               | sip:bob@example.org |
                                               |                     |
                                               +---------------------+

Camarillo Standards Track [Page 8] RFC 5361 Permission Document Format October 2008

<?xml version="1.0" encoding="UTF-8"?>
       <cp:ruleset
           xmlns="urn:ietf:params:xml:ns:consent-rules"
           xmlns:cp="urn:ietf:params:xml:ns:common-policy">
           <cp:rule id="f1">
        <cp:conditions>
            <cp:identity>
                <cp:many/>
            </cp:identity>
            <recipient>
                <cp:one id="sip:bob@example.org"/>
            </recipient>
            <target>
                <cp:one id="sip:alices-friends@example.com"/>
            </target>
        </cp:conditions>
        <cp:actions>
            <trans-handling
                perm-uri="sips:grant-1awdch5Fasddfce34@example.com"
                >grant</trans-handling>
            <trans-handling
                perm-uri="https://example.com/grant-1awdch5Fasddfce34"
                >grant</trans-handling>
            <trans-handling
                perm-uri="sips:deny-23rCsdfgvdT5sdfgye@example.com"
                >deny</trans-handling>
            <trans-handling
                perm-uri="https://example.com/deny-23rCsdfgvdT5sdfgye"
                >deny</trans-handling>
        </cp:actions>
        <cp:transformations/>
    </cp:rule>
    </cp:ruleset>

Camarillo Standards Track [Page 9] RFC 5361 Permission Document Format October 2008

5. XML Schema

 <?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="recipient" 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. Extensibility

 This specification defines elements that do not have extension points
 in the "urn:ietf:params:xml:ns:consent-rules" namespace.  Instance
 documents that utilize these element definitions SHOULD be schema
 valid.  Applications processing instance documents with content that
 is not understood by the application MUST ignore that content.  IETF
 extension documents of this specification MAY reuse the
 "urn:ietf:params:xml:ns:consent-rules" namespace to define new
 elements.

Camarillo Standards Track [Page 10] RFC 5361 Permission Document Format October 2008

7. IANA Considerations

 This section registers a new XML namespace and a new XML schema per
 the procedures in [RFC3688].

7.1. 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>
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="http://www.rfc-editor.org/rfc/rfc5361.txt">RFC 5361
     </a>.</p>
   </body>
   </html>
   END

7.2. 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.

Camarillo Standards Track [Page 11] RFC 5361 Permission Document Format October 2008

8. Security Considerations

 RFC 5360 [RFC5360] discusses security-related issues, such as how to
 authenticate SIP and HTTP requests granting permissions and how to
 transport permission documents between relays and recipients, that
 are directly related to this specification.

9. Acknowledgements

 Jonathan Rosenberg provided useful ideas on this document.  Hannes
 Tschofenig helped align this document with common policy.  Ben
 Campbell and Mary Barnes performed a thorough review of this
 document.  Lakshminath Dondeti provided useful comments.

10. References

10.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2617]  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.
 [RFC3261]  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.
 [RFC3323]  Peterson, J., "A Privacy Mechanism for the Session
            Initiation Protocol (SIP)", RFC 3323, November 2002.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            January 2004.
 [RFC4474]  Peterson, J. and C. Jennings, "Enhancements for
            Authenticated Identity Management in the Session
            Initiation Protocol (SIP)", RFC 4474, August 2006.
 [RFC4745]  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.

Camarillo Standards Track [Page 12] RFC 5361 Permission Document Format October 2008

 [RFC5360]  Rosenberg, J., Camarillo, G., and D. Willis, "A Framework
            for Consent-Based Communications in the Session Initiation
            Protocol (SIP)", RFC 5360, October 2008.

10.2. Informative References

 [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
            RFC 3966, December 2004.
 [RFC3325]  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.

Author's Address

 Gonzalo Camarillo
 Ericsson
 Hirsalantie 11
 Jorvas  02420
 Finland
 EMail: Gonzalo.Camarillo@ericsson.com

Camarillo Standards Track [Page 13] RFC 5361 Permission Document Format October 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 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
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Camarillo Standards Track [Page 14]

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