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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIPPING G. Camarillo 3 Internet-Draft Ericsson 4 Intended status: Standards Track April 2, 2007 5 Expires: October 4, 2007 7 A Document Format for Requesting Consent 8 draft-ietf-sipping-consent-format-02.txt 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on October 4, 2007. 35 Copyright Notice 37 Copyright (C) The IETF Trust (2007). 39 Abstract 41 This document defines an Extensible Markup Language (XML) format for 42 a permission document used to request consent. A permission document 43 written in this format is used by a relay to request a specific 44 recipient permission to perform a particular routing translation. 46 Table of Contents 48 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 49 2. Definitions and Terminology . . . . . . . . . . . . . . . . . 3 50 3. Permission Document Structure . . . . . . . . . . . . . . . . 3 51 3.1. Conditions . . . . . . . . . . . . . . . . . . . . . . . . 4 52 3.1.1. Identity Condition . . . . . . . . . . . . . . . . . . 4 53 3.1.2. Sender Condition . . . . . . . . . . . . . . . . . . . 5 54 3.1.3. Target Condition . . . . . . . . . . . . . . . . . . . 7 55 3.2. Actions . . . . . . . . . . . . . . . . . . . . . . . . . 7 56 3.2.1. Translation Handling . . . . . . . . . . . . . . . . . 7 57 4. Example Document . . . . . . . . . . . . . . . . . . . . . . . 7 58 5. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 8 59 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 60 6.1. XML Namespace Registration . . . . . . . . . . . . . . . . 9 61 6.2. XML Schema Registration . . . . . . . . . . . . . . . . . 10 62 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 63 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 64 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 65 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 66 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 67 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12 68 Intellectual Property and Copyright Statements . . . . . . . . . . 13 70 1. Introduction 72 The framework for consent-based communications in the Session 73 Initiation Protocol (SIP) [9] identifies the need for a format to 74 create permission documents. Such permission documents are used by 75 SIP [3] relays to request permission to perform translations. A 76 relay is defined as any SIP server, be it a proxy, B2BUA (Back-to- 77 Back User Agent), or some hybrid, which receives a request and 78 translates the request URI into one or more next hop URIs to which it 79 then delivers a request. 81 The format for permission documents specified in this document is 82 based on the XML document format for expressing Privacy Preferences 83 [8]. 85 2. Definitions and Terminology 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in RFC 2119 [1]. 91 Relay: Any SIP server, be it a proxy, B2BUA (Back-to-Back User 92 Agent), or some hybrid, that receives a request, translates its 93 Request-URI into one or more next-hop URIs (i.e., recipient URIs), 94 and delivers the request to those URIs. 96 Recipient URI: The Request-URI of an outgoing request sent by an 97 entity (e.g., a user agent or a proxy). The sending of such 98 request may have been the result of a translation operation. 100 Target URI: The Request-URI of an incoming request that arrives to 101 an entity (e.g., a proxy) that will perform a translation 102 operation. 104 Translation operation: Operation by which an entity (e.g., a proxy) 105 translates the request URI of an incoming request (i.e., the 106 target URI) into one or more URIs (i.e., recipient URIs) which are 107 used as the request URIs of one or more outgoing requests. 109 3. Permission Document Structure 111 A permission document is an XML document, formatted according to the 112 schema defined in [8]. Permission documents inherit the MIME type of 113 common policy documents, 'application/auth-policy+xml'. As described 114 in [8], this type of document is composed of three parts: conditions, 115 actions, and transformations. However, even though permission 116 documents need to have a transformation part to comply to the common 117 policy syntax, effectively, permission documents do not make any use 118 of transformations. 120 This section defines the new conditions and actions defined by this 121 specification. This specification does not define any new 122 transformation. 124 3.1. Conditions 126 Note that, as discussed in [8], a permission document applies to a 127 translation if all the expressions in its conditions part evaluate to 128 TRUE. 130 3.1.1. Identity Condition 132 The identity condition, defined in [8], is matched against the 133 recipient URI of a translation. 135 When performing a translation, a relay matches the identity condition 136 of the permission document that was used to request permission for 137 that translation against the destination URI of the outgoing request. 138 When receiving a request granting or denying permissions (e.g., a SIP 139 PUBLISH request as described in [9]), the relay matches the identity 140 condition of the permission document that was used to request 141 permission against the identity of the entity granting or denying 142 permissions (i.e., the sender of the PUBLISH request). 144 The element is defined in [8], which indicates that the 145 specific usages of the framework document need to define details that 146 are protocol and usage specific. In particular, this section defines 147 acceptable means of authentication. 149 The 'id' attribute in the elements and MUST contain a 150 scheme when these elements appear in a permission document. 152 When used with SIP, a recipient granting or denying a relay 153 permissions is considered authenticated if one of the following 154 techniques is used: 156 SIP Identity [7], as described in [9]. For PUBLISH requests that 157 are authenticated using the SIP Identity mechanism, the identity 158 of the sender of the PUBLISH request is equal to the SIP URI in 159 the From header field of the request, assuming that the signature 160 in the Identity header field has been validated. 162 P-Asserted-Identity [5], as described in [9]. For PUBLISH requests 163 that are authenticated using the P-Asserted-Identity mechanism, 164 the identity of the sender of the PUBLISH request is equal to the 165 P-Asserted-Identity header field of the request. 167 Return Routability Test, as described in [9]. 169 SIP digest, as described in [9]. 171 3.1.2. Sender Condition 173 The sender condition is matched against the URI of the sender of the 174 request that is used as input for a translation. Sender conditions 175 can contain the same elements and attributes as identity conditions. 177 When performing a translation, a relay matches the sender condition 178 against the identity of the sender of the incoming request. 180 The following subsections define acceptable means of authentication, 181 the procedure for representing the identity of the sender as a URI, 182 and the procedure for converting an identifier of the form 183 user@domain, present in the 'id' attribute of the and 184 elements, into a URI. 186 3.1.2.1. Acceptable Means of Authentication 188 When used with SIP, a request sent by a sender is considered 189 authenticated if one of the following techniques is used: 191 SIP Digest: the relay authenticates the sender using SIP digest 192 authentication [2]. However, if the anonymous authentication 193 described on page 194 of RFC 3261 [3] is used, the sender is not 194 considered authenticated. 196 Asserted Identity: if a request contains a P-Asserted-ID header 197 field [5] and the request is coming from a trusted element, the 198 sender is considered authenticated. 200 Cryptographically Verified Identity: if a request contains an 201 Identity header field as defined in [7], and it validates the From 202 header field of the request, the request is considered to be 203 authenticated. Note that this is true even if the request 204 contained a From header field of the form 205 sip:anonymous@example.com. As long as the signature verifies that 206 the request legitimately came from this identity, it is considered 207 authenticated. 209 3.1.2.2. Computing a URI for the Sender 211 For requests that are authenticated using SIP Digest, the identity of 212 the sender is set equal to the SIP Address of Record (AOR) for the 213 user that has authenticated themselves. For example, consider the 214 following "user record" in a database: 216 SIP AOR: sip:alice@example.com 217 digest username: ali 218 digest password: f779ajvvh8a6s6 219 digest realm: example.com 221 If the relay receives a request, challenges it with the realm set to 222 "example.com", and the subsequent request contains an Authorization 223 header field with a username of "ali" and a digest response generated 224 with the password "f779ajvvh8a6s6", the identity used in matching 225 operations is "sip:alice@example.com". 227 For requests that are authenticated using RFC 3325 [5], the identity 228 of the sender is equal to the SIP URI in the P-Asserted-ID header 229 field. If there are multiple values for the P-Asserted-ID header 230 field (there can be one sip URI and one tel URI [10]), then each of 231 them is used for the comparisons outlined in [8], and if either of 232 them match a or element, it is considered a match. 234 For requests that are authenticated using the SIP Identity mechanism 235 [7], identity of the sender is equal to the SIP URI in the From 236 header field of the request, assuming that the signature in the 237 Identity header field has been validated. 239 SIP also allows for anonymous requests. If a request is anonymous 240 because the digest challenge/response used the "anonymous" username, 241 the request is considered unauthenticated and will not match the 242 condition. If a request is anonymous because it contains a 243 Privacy header field [4], but still contains a P-Asserted-ID header 244 field, the identity in the P-Asserted-ID header field is still used 245 in the authorization computations; the fact that the request was 246 anonymous has no impact on the identity processing. However, if the 247 request had traversed a trust boundary and the P-Asserted-ID header 248 field and the Privacy header field had been removed, the request will 249 be considered unauthenticated when it arrives at the presence server, 250 and thus not match the condition. Finally, if a request 251 contained an Identity header field that was validated, and the From 252 header field contained a URI of the form sip:anonymous@example.com, 253 then the watcher is considered authenticated, and it will have an 254 identity equal to sip:anonymous@example.com. Had such an identity 255 been placed into a or element, there will be a match. 257 3.1.2.3. Computing a SIP URI from the id Attribute 259 If the or condition does not contain a scheme, 260 conversion of the value in the 'id' attribute to a SIP URI is done 261 trivially. If the characters in the 'id' attribute are valid 262 characters for the user and hostpart components of the SIP URI, a 263 'sip:' is appended to the contents of the 'id' attribute, and the 264 result is the SIP URI. If the characters in the 'id' attribute are 265 not valid for the user and hostpart components of the SIP URI, 266 conversion is not possible. This happens, for example, when the user 267 portion of the 'id' attribute contain UTF-8 characters. 269 3.1.3. Target Condition 271 The target condition is matched against the target URI of a 272 translation. Target conditions can contain the same elements and 273 attributes as identity conditions. 275 When performing a translation, a relay matches the target condition 276 against the destination of the incoming request, which is typically 277 contained in the Request-URI. 279 3.2. Actions 281 The actions in a permission document provide URIs to grant or deny 282 permission to perform the translation described in the document. 284 3.2.1. Translation Handling 286 The provides URIs for a recipient to grant or deny 287 the relay permission to perform a translation. The defined values 288 are: 290 deny: this action tells the relay not to perform the translation. 292 grant: this action tells the server to perform the translation. 294 The 'perm-uri' attribute in the element provides a 295 URI to grant or deny permission to perform a translation. 297 4. Example Document 299 The following permission document is generated by the relay handling 300 'sip:alices-friends@example.com' in order to ask for permission to 301 relay requests sent to that URI to 'sip:bob@example.org'. 303 304 310 311 312 313 314 315 316 317 318 319 320 321 322 323 grant 325 deny 327 328 329 330 332 5. XML Schema 333 334 342 343 344 346 347 348 349 350 351 352 354 355 356 357 358 360 361 362 363 365 367 6. IANA Considerations 369 This section registers a new XML namespace and a new XML schema per 370 the procedures in [6]. 372 6.1. XML Namespace Registration 374 URI: urn:ietf:params:xml:ns:common-policy 376 Registrant Contact: IETF SIPPING working group, 377 , Gonzalo Camarillo 378 379 XML: 381 BEGIN 382 383 385 386 387 389 Consent Rules Namespace 390 391 392

Namespace for Permission Documents

393

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

394

See RFCXXXX 395 [NOTE TO IANA/RFC-EDITOR: 396 Please replace XXXX with the RFC number of this 397 specification.].

398 399 400 END 402 6.2. XML Schema Registration 404 URI: urn:ietf:params:xml:schema:common-policy 406 Registrant Contact: IETF SIPPING working group, 407 , Gonzalo Camarillo 408 410 XML: The XML schema to be registered is contained in Section 5. 412 7. Security Considerations 414 Permission documents can reveal sensitive information. Additionally, 415 attackers may attempt to modify them in order to have clients grant 416 or deny permissions different to the ones they think are granting or 417 denying. For this reason, it is RECOMMENDED that relays use strong 418 means for information integrity protection and confidentiality when 419 sending permission documents to clients. 421 The mechanism used for conveying information to clients SHOULD ensure 422 the integrity and confidentially of the information. In order to 423 achieve these, an end-to-end SIP encryption mechanism, such as 424 S/MIME, as described in RFC 3261 [3], SHOULD be used. 426 If strong end-to-end security means (such as above) is not available, 427 it is RECOMMENDED that hop-by-hop security based on TLS and SIPS 428 URIs, as described in [3], is used. 430 8. Acknowledgements 432 Jonathan Rosenberg provided useful ideas on this document. Ben 433 Campbell and Mary Barnes performed a thorough review of this 434 document. 436 9. References 438 9.1. Normative References 440 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 441 Levels", BCP 14, RFC 2119, March 1997. 443 [2] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., 444 Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: 445 Basic and Digest Access Authentication", RFC 2617, June 1999. 447 [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 448 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 449 Session Initiation Protocol", RFC 3261, June 2002. 451 [4] Peterson, J., "A Privacy Mechanism for the Session Initiation 452 Protocol (SIP)", RFC 3323, November 2002. 454 [5] Jennings, C., Peterson, J., and M. Watson, "Private Extensions 455 to the Session Initiation Protocol (SIP) for Asserted Identity 456 within Trusted Networks", RFC 3325, November 2002. 458 [6] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 459 January 2004. 461 [7] Peterson, J. and C. Jennings, "Enhancements for Authenticated 462 Identity Management in the Session Initiation Protocol (SIP)", 463 RFC 4474, August 2006. 465 [8] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., Polk, 466 J., and J. Rosenberg, "Common Policy: A Document Format for 467 Expressing Privacy Preferences", RFC 4745, February 2007. 469 [9] Rosenberg, J., "A Framework for Consent-Based Communications in 470 the Session Initiation Protocol (SIP)", 471 draft-ietf-sip-consent-framework-01 (work in progress), 472 November 2006. 474 9.2. Informative References 476 [10] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, 477 December 2004. 479 Author's Address 481 Gonzalo Camarillo 482 Ericsson 483 Hirsalantie 11 484 Jorvas 02420 485 Finland 487 Email: Gonzalo.Camarillo@ericsson.com 489 Full Copyright Statement 491 Copyright (C) The IETF Trust (2007). 493 This document is subject to the rights, licenses and restrictions 494 contained in BCP 78, and except as set forth therein, the authors 495 retain all their rights. 497 This document and the information contained herein are provided on an 498 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 499 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 500 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 501 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 502 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 503 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 505 Intellectual Property 507 The IETF takes no position regarding the validity or scope of any 508 Intellectual Property Rights or other rights that might be claimed to 509 pertain to the implementation or use of the technology described in 510 this document or the extent to which any license under such rights 511 might or might not be available; nor does it represent that it has 512 made any independent effort to identify any such rights. 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