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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 GEOPRIV J. Winterbottom 3 Internet-Draft Commscope 4 Intended status: Standards Track H. Tschofenig 5 Expires: January 13, 2013 Nokia Siemens Networks 6 H. Schulzrinne 7 Columbia University 8 M. Thomson 9 (Unaffiliated) 10 July 12, 2012 12 A Location Dereferencing Protocol Using HELD 13 draft-ietf-geopriv-deref-protocol-06 15 Abstract 17 This document describes how to use the Hypertext Transfer Protocol 18 (HTTP) over Transport Layer Security (TLS) as a dereferencing 19 protocol to resolve a reference to a Presence Information Data Format 20 Location Object (PIDF-LO). The document assumes that a Location 21 Recipient possesses a URI that can be used in conjunction with the 22 HTTP-Enabled Location Delivery (HELD) protocol to request the 23 location of the Target. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on January 13, 2013. 42 Copyright Notice 44 Copyright (c) 2012 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. HELD Dereference Protocol . . . . . . . . . . . . . . . . . . 4 62 3.1. HELD Usage Profile . . . . . . . . . . . . . . . . . . . . 4 63 3.2. HTTP GET Behavior . . . . . . . . . . . . . . . . . . . . 5 64 4. Authorization Models . . . . . . . . . . . . . . . . . . . . . 6 65 4.1. Authorization by Possession . . . . . . . . . . . . . . . 7 66 4.2. Authorization via Access Control . . . . . . . . . . . . . 8 67 4.3. Access Control with HELD Deference . . . . . . . . . . . . 8 68 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 69 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 70 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 71 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 72 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 73 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 74 9.2. Informative references . . . . . . . . . . . . . . . . . . 15 75 Appendix A. GEOPRIV Using Protocol Compliance . . . . . . . . . . 16 76 Appendix B. Compliance to Location Reference Requirements . . . . 19 77 B.1. Requirements for a Location Configuration Protocol . . . . 20 78 B.2. Requirements for a Location Dereference Protocol . . . . . 21 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 81 1. Introduction 83 A location URI [RFC5808] identifies a resource that contains the 84 location of an entity. This document specifies how a holder of an 85 "http:" or "https:" location URI uses that URI to retrieve location 86 information. 88 A location URI can be acquired using a location configuration 89 protocol, such as HTTP-Enabled Location Delivery (HELD) [RFC5985] or 90 the Dynamic Host Configuration Protocol (DHCP) location URI option 91 [I-D.ietf-geopriv-dhcp-lbyr-uri-option]. 93 A Location Recipient that dereferences a location URI acquires 94 location information in the of a Presence Information Data Format - 95 Location Object (PIDF-LO) document [RFC4119]. HELD parameters allow 96 for specifying the type of location information, though some 97 constraints are placed on allowable parameters. 99 Location URIs compatible with HELD dereferencing use the "https:" or 100 "http:" scheme. HELD can be used by Location Recipients that are 101 aware of the fact that the URI is a location URI. Mandatory support 102 for an HTTP GET request ensures that the URI can be used even if it 103 is not recognized as a location URI. 105 2. Terminology 107 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 108 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 109 document are to be interpreted as described in [RFC2119]. 111 This document uses key terminology from several sources: 113 o terms for the GEOPRIV reference model defined in [RFC6280]; 115 o the term Location Information Server (LIS), from [RFC5687], is a 116 node in the access network that provides location information to 117 an end point; a LIS provides location URIs; 119 o the term Location Server (LS), from [RFC6280], is used to identify 120 the role that responds to a location dereference request; this 121 might be the same entity as the LIS, but the model in [RFC5808] 122 allows for the existence of separate - but related - entities; and 124 o the term location URI is coined in [RFC5808]. 126 3. HELD Dereference Protocol 128 This section describes how HELD can be used to dereference a location 129 URI. This process can be applied when a Location Recipient is in 130 possession of a location URI with a "https:" or "http:" URI scheme. 132 This document does not describe a specific authentication mechanism. 133 This means that authorization policies are unable to specifically 134 identify authorized Location Recipients. 136 A Location Recipient that wishes to dereference an "https:" or 137 "http:" URI performs a HELD request on HTTP to the identified 138 resource. 140 Note: In many cases, an "http:" URI does not provide sufficient 141 security for location URIs. The absence of the security 142 mechanisms provided by TLS means that the Rule Maker has no 143 control over who receives location information and the Location 144 Recipient has no assurance that the information is correct. 146 The Location Recipient establishes a connection to the LS, as 147 described in [RFC2818]. 149 TLS MUST be used unless confidentiality and integrity are provided by 150 some other mechanism, such as IPsec or a fully trusted network. 151 Without a reliable assertion that a mechanism is in place, such as 152 through configuration or user override, then TLS MUST be used. When 153 TLS is used, the TLS ciphersuite TLS_NULL_WITH_NULL_NULL MUST NOT be 154 used and the LS MUST be authenticated [RFC6125] to ensure that the 155 correct server is contacted. 157 A Location Server MAY reject a request and request that a Location 158 Recipient provide authentication credentials if authorization is 159 dependent on the Location Recipient identity. Future specifications 160 could define an authentication mechanism and a means by which 161 Location Recipients are identified in authorization policies. This 162 document provides definitions for neither item. 164 3.1. HELD Usage Profile 166 Use of HELD as a location dereference protocol is largely the same as 167 its use as a location configuration protocol. Aside from the 168 restrictions noted in this document, HELD semantics do not differ 169 from those established in [RFC5985]. 171 The HELD "locationRequest" is the only request permitted by this 172 specification. Similarly, request parameters other than the 173 following MUST NOT be accepted by the LS: "responseTime", 174 "locationType" (including the associated "exact" attribute). 176 Parameters and requests that do not have known behaviour for 177 dereference requests MUST NOT be used. The LS MUST ignore any 178 parameters that it does not understand unless it knows the parameters 179 to be invalid. If parameters are understood by the LS and known to 180 be invalid, the LS MAY generate a HELD error response. For instance, 181 those defined in [RFC6155] are always invalid and can be rejected. 183 The LS MUST NOT generate location URIs or provide a "locationUriSet" 184 in response to a dereference request. If the location request 185 contains a "locationType" element that includes "locationURI", this 186 parameter is either ignored or rejected as appropriate, based on the 187 associated "exact" attribute. 189 3.2. HTTP GET Behavior 191 GET is the method assumed by generic HTTP user agents, therefore 192 unless context identifies an "https:" URI as a HELD URI, such a user 193 agent might simply send an HTTP GET. Rather than providing an HTTP 194 405 (Method Not Allowed) response indicating that POST is the only 195 permitted method, a LIS MUST provide a HELD location response if it 196 receives an HTTP GET request. 198 An HTTP GET request to a HELD URI produces a HELD response as if the 199 following HELD request had been sent using HTTP POST: 201 202 203 geodetic civic 204 205 207 Figure 1: GET Request Equivalent Location Request 209 HTTP GET requests MUST be safe and idempotent [RFC2616] - that is, 210 there are no side-effects of making the request and a repeated 211 request has no more effect than a single request. Repeating a HELD 212 request might result in a different location, but only as a result of 213 a change in the state of the resource: the location of the Target. 215 Only the creation of a location URI as a result of receiving a 216 request causes a HELD request to have side-effects. A request to a 217 location URI can be both safe and idempotent, since a location URI 218 cannot be produced in response to a request to a location URI. 220 A Location Recipient MAY infer from a response containing the HELD 221 content type, "application/held+xml", that a URI references a 222 resource that supports HELD. 224 Content negotiation MAY be supported to produce a presence document 225 in place of a HELD location response. Where the presence document 226 would otherwise be included in a "locationResponse" document, it can 227 be included in the body of the HTTP response directly by including an 228 "Accept" header that includes "application/pidf+xml". 230 4. Authorization Models 232 This section discusses two extreme types of authorization models for 233 dereferencing with HELD URIs, namely "Authorization by Possession" 234 and "Authorization by Access Control". In the subsequent subsections 235 we discuss the properties of these two models. Figure 2, from 236 [RFC5808], shows the model applicable to location configuration, 237 conveyance and dereference. 239 +---------+--------+ Location +-----------+ 240 | | | Dereference | Location | 241 | LIS - LS +---------------+ Recipient | 242 | | | Protocol | | 243 +----+----+--------+ (3) +-----+-----+ 244 | `. | 245 | Policy `. | 246 Location | Exchange `. | 247 Configuration | (*) | | 248 Protocol | +----+----+ | 249 (1) | | Rule | Location | 250 | | Maker | Conveyance | 251 +-----+----+ +---------+ Protocol | 252 | | (2) | 253 | Target +------------------------------+ 254 | | 255 +----------+ 257 Figure 2: Communication Model 259 It is important to note that this document does not mandate a 260 specific authorization model. It is possible to combine aspects of 261 both models. However, no authentication framework is provided, which 262 limits the policy options available when the "Authorization by Access 263 Control" model is used. 265 For either authorization model, the overall process is similar. The 266 following steps are followed, with minor alterations: 268 1. The Target acquires a location URI from the LIS. This uses a 269 location configuration protocol (LCP), such as HELD or DHCP. 271 2. The Target then conveys the location URI to a third party, the 272 Location Recipient (for example using SIP as described in 273 [RFC6442]). This step is shown in (2) of Figure 2. 275 3. The Location Recipient then needs to dereference the location URI 276 in order to obtain the Location Object (3). An "https:" or 277 "http:" URI is dereferenced as described in this document; other 278 URI schemes might be dereferenced using another method. 280 In this final step, the Location Server (LS) or LIS makes an 281 authorization decision. How this decision is reached depends on the 282 authorization model. 284 4.1. Authorization by Possession 286 In this model, possession - or knowledge - of the location URI is 287 used to control access to location information. A location URI might 288 be constructed such that it is hard to guess (see C8 of [RFC5808]) 289 and the set of entities that it is disclosed to can be limited. The 290 only authentication this would require by the LS is evidence of 291 possession of the URI. The LS could immediately authorize any 292 request that indicates this URI. 294 Authorization by possession does not require direct interaction with 295 a Rule Maker; it is assumed that the Rule Maker is able to exert 296 control over the distribution of the location URI. Therefore, the 297 LIS can operate with limited policy input from a Rule Maker. 299 Limited disclosure is an important aspect of this authorization 300 model. The location URI is a secret; therefore, ensuring that 301 adversaries are not able to acquire this information is paramount. 302 Encryption, such as might be offered by TLS [RFC5246] or S/MIME 303 [RFC5751], protects the information from eavesdroppers. 305 Use of authorization by possession location URIs in a hop-by-hop 306 protocol such as SIP [RFC3261] adds the possibility of on-path 307 adversaries. Depending on the usage of the location URI for certain 308 location based applications (e.g., emergency services, location based 309 routing) specific treatment is important, as discussed in [RFC6442]. 311 Using possession as a basis for authorization means that, once 312 granted, authorization cannot be easily revoked. Cancellation of a 313 location URI ensures that legitimate users are also affected; 314 application of additional policy is theoretically possible, but could 315 be technically infeasible. Expiration of location URIs limits the 316 usable time for a location URI, requiring that an attacker continue 317 to learn new location URIs to retain access to current location 318 information. 320 A very simple policy might be established at the time that a location 321 URI is created. This policy specifies that the location URI expires 322 after a certain time, which limits any inadvertent exposure of 323 location information to adversaries. The expiration time of the 324 location URI might be negotiated at the time of its creation, or it 325 might be unilaterally set by the LIS. 327 4.2. Authorization via Access Control 329 Use of explicit access control provides a Rule Maker greater control 330 over the behaviour of an LS. In contrast to authorization by 331 possession, possession of this form of location URI does not imply 332 authorization. Since an explicit policy is used to authorize access 333 to location information, the location URI can be distributed to many 334 potential Location Recipients. 336 Either before creation or dissemination of the location URI, the Rule 337 Maker establishes an authorization policy with the LS. In reference 338 to Figure 2, authorization policies might be established at creation 339 (Step 1), and need to be established before the location URI is 340 published (Step 2) to ensure that the policy grants access to the 341 desired Location Recipients. Depending on the mechanism used, it 342 might also be possible to change authorization policies at any time. 344 A possible format for these authorization policies is available with 345 GEOPRIV Common Policy [RFC4745] and Geolocation Policy 346 [I-D.ietf-geopriv-policy]. Additional constraints might be 347 established by other means. 349 The LS enforces the authorization policy when a Location Recipient 350 dereferences the URI. Explicit authorization policies allow a Rule 351 Maker to specify how location information is provided to Location 352 Recipients. 354 4.3. Access Control with HELD Deference 356 This document does not describe a specific authentication mechanism; 357 therefore, the authorization by access control model is not an 358 option. Instead, this document assumes the authorization by 359 possession model. 361 Other policy mechanisms, such as those described in 362 [I-D.ietf-geopriv-policy], can be applied for different Location 363 Recipients if each recipient is given a different location URIs. 365 Each location URI can be assigned different authorization policy. 366 Selective disclosure used in this fashion can be used in place of 367 identity-based authorization. 369 How policy is associated with a location URI is not defined by this 370 document. [I-D.ietf-geopriv-policy-uri] describes one possible 371 mechanism. 373 Use of identity-based authorization policy is not precluded. A 374 Location Server MAY support an authentication mechanism that enables 375 identity-based authorization policies to be used. Future 376 specifications might define means of identifying recipients. 378 Note: Policy frameworks like [RFC4745] degrade in a way that 379 protects privacy if features are not supported. If a policy 380 specifies a rule that is conditional on the identity of a 381 recipient and the protocol does not (or cannot) provide an 382 assertion identity of the recipient, the rule has no effect and 383 the policy defaults to providing less information. 385 5. Examples 387 An example scenario envisioned by this document is shown in Figure 3. 388 This diagram shows how a location dereference protocol fits with 389 location configuration and conveyance. [RFC5808] contains more 390 information on this scenario and others like it. 392 +-------------+ 393 +------------+ | Location | +-----------+ 394 | End Device | | Information | | Location | 395 | (Target) | | Server | | Recipient | 396 +-----+------+ +------+------+ +-----+-----+ 397 | | | 398 .- + - - - - - - - - - - - - + -. | 399 : | locationRequest | : | 400 . |----(for location URI)-->| . | 401 : | | : Location | 402 . | locationResponse | . Configuration | 403 : |<-----(location URI)-----| : | 404 . | | . | 405 `- + - - - - - - - - - - - - + -' | 406 | | | 407 | Location Conveyance | 408 |~ ~ ~ ~ ~ ~ ~ ~ ~ ~(location URI)~ ~ ~ ~ ~ ~ ~ ~ ~>| 409 | | | 410 | .- + - - - - - - - - - - - - + -. 411 | : | locationRequest | : 412 | . |<------(for civic)-------| . 413 | Dereferencing : | | : 414 | . | locationResponse | . 415 | : |--------(PIDF-LO)------->| : 416 | . | | . 417 | `- + - - - - - - - - - - - - + -' 418 | | | 420 Figure 3: Example of Dereference Protocol Exchange 422 The example in Figure 4 shows the simplest form of dereferencing 423 request using HELD to the location URI 424 "https://ls.example.com:49152/uri/w3g61nf5n66p0". The only way that 425 this differs from the example in Section 10.1 of [RFC5985] is in the 426 request URI and the source of the URI. 428 POST /uri/w3g61nf5n66p0 HTTP/1.1 429 Host: ls.example.com:49152 430 Content-Type: application/held+xml 431 Content-Length: 87 433 434 436 Figure 4: Minimal Dereferencing Request 438 Figure 5 shows the response to the previous request listing both 439 civic and geodetic location information of the Target's location. 441 Again, this is identical to the response in Section 10.1 of [RFC5985] 442 - unless policy specifies otherwise, the Location Recipient receives 443 the same information as the Device. 445 HTTP/1.1 200 OK 446 Server: Example LIS 447 Date: Mon, 10 Jan 2011 03:42:29 GMT 448 Expires: Tue, 11 Jan 2011 03:42:29 GMT 449 Cache-control: private 450 Content-Type: application/held+xml 451 Content-Length: 676 453 454 455 457 458 459 461 462 464 -34.407 150.88001 465 466 467 468 469 false 470 471 2011-01-11T03:42:29+00:00 472 473 Wiremap 474 475 476 2006-01-10T03:42:28+00:00 477 478 479 481 Figure 5: Response with Location Information 483 The following GET request is treated in an equivalent fashion. The 484 LS treats this request as though it were a location request of the 485 form shown in Figure 1. The same response might be provided. 487 GET /uri/w3g61nf5n66p0 HTTP/1.1 488 Host: ls.example.com:49152 489 Accept: application/held+xml 491 Figure 6: GET Request 493 The following GET request uses content negotiation to indicate a 494 preference for a presence document. 496 GET /uri/w3g61nf5n66p0 HTTP/1.1 497 Host: ls.example.com:49152 498 Accept: application/pidf+xml,application/held+xml;q=0.5 500 Figure 7: GET Request with Content Negotiation 502 The response only differs from a normal HELD location response to a 503 POST request in that the "locationResponse" element is omitted and 504 the "Content-Type" header reflects the changed content. 506 HTTP/1.1 200 OK 507 Server: Example LIS 508 Date: Mon, 10 Jan 2011 03:42:29 GMT 509 Expires: Tue, 11 Jan 2011 03:42:29 GMT 510 Cache-control: private 511 Content-Type: application/pidf+xml 512 Content-Length: 591 514 515 517 518 520 Figure 8: GET Response with PIDF-LO 522 6. Security Considerations 524 Privacy of location information is the most important security 525 consideration for this document. Two measures in particular are used 526 to protect privacy: TLS and authorization policies. TLS provides a 527 means of ensuring confidentiality of location information through 528 encryption and mutual authentication. An authorization policy allows 529 a Rule Maker to explicitly control how location information is 530 provided to Location Recipients. 532 The process by which a Rule Maker establishes an authorization policy 533 is not covered by this document; several methods are possible, for 534 instance: [I-D.ietf-geopriv-policy-uri], [RFC4825]. 536 TLS MUST be used for dereferencing location URIs unless 537 confidentiality and integrity are provided by some other mechanism, 538 as discussed in Section 3. Location Recipients MUST authenticate the 539 host identity using the domain name included in the location URI, 540 using the procedure described in Section 3.1 of [RFC2818]. Local 541 policy determines what a Location Recipient does if authentication 542 fails or cannot be attempted. 544 The authorization by possession model (Section 4.1) further relies on 545 TLS when transmitting the location URI to protect the secrecy of the 546 URI. Possession of such a URI implies the same privacy 547 considerations as possession of the PIDF-LO document that the URI 548 references. 550 Location URIs MUST only be disclosed to authorized Location 551 Recipients. The GEOPRIV architecture [RFC6280] identifies the Rule 552 Maker role as being the entity that authorizes disclosure of this 553 nature. 555 Protection of the location URI is necessary, since the policy 556 attached to such a location URI permits any who have the URI to view 557 it. This aspect of security is covered in more detail in the 558 specification of location conveyance protocols, such as [RFC6442]. 560 The LS MUST NOT provide any information about the Target except its 561 location, unless policy from a Rule Maker allows otherwise. In 562 particular, the requirements in [RFC5808] mandate this measure to 563 protect the identity of the Target. To this end, an unlinked 564 pseudonym MUST be provided in the "entity" attribute of the PIDF-LO 565 document. 567 Further security considerations and requirements relating to the use 568 of location URIs are described in [RFC5808]. 570 7. IANA Considerations 572 This document makes no request of IANA. 574 [[IANA/RFC-EDITOR: Please remove this section before publication.]] 576 8. Acknowledgements 578 Thanks to Barbara Stark and Guy Caron for providing early comments. 579 Thanks to Rohan Mahy for constructive comments on the scope and 580 format of the document. Thanks to Ted Hardie for his strawman 581 proposal that provided assistance with the security section of this 582 document. Richard Barnes made helpful observations on the 583 application of authorization policy. Bernard Aboba and Julian 584 Reschke contributed constructive reviews. 586 The participants of the GEOPRIV interim meeting 2008 provided 587 significant feedback on this document. 589 James Polk provided input on security in June 2008. 591 Martin Dawson was an original author of this document. Sadly, he 592 passed away prior to its publication. 594 9. References 596 9.1. Normative References 598 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 599 Requirement Levels", BCP 14, RFC 2119, March 1997. 601 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 602 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 603 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 605 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 607 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 608 Resource Identifier (URI): Generic Syntax", STD 66, 609 RFC 3986, January 2005. 611 [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object 612 Format", RFC 4119, December 2005. 614 [RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV 615 Presence Information Data Format Location Object (PIDF-LO) 616 Usage Clarification, Considerations, and Recommendations", 617 RFC 5491, March 2009. 619 [RFC5985] Barnes, M., "HTTP-Enabled Location Delivery (HELD)", 620 RFC 5985, September 2010. 622 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and 623 Verification of Domain-Based Application Service Identity 624 within Internet Public Key Infrastructure Using X.509 625 (PKIX) Certificates in the Context of Transport Layer 626 Security (TLS)", RFC 6125, March 2011. 628 9.2. Informative references 630 [I-D.ietf-geopriv-dhcp-lbyr-uri-option] 631 Polk, J., "Dynamic Host Configuration Protocol (DHCP) IPv4 632 and IPv6 Option for a Location Uniform Resource Identifier 633 (URI)", draft-ietf-geopriv-dhcp-lbyr-uri-option-15 (work 634 in progress), May 2012. 636 [I-D.ietf-geopriv-policy] 637 Schulzrinne, H., Tschofenig, H., Cuellar, J., Polk, J., 638 Morris, J., and M. Thomson, "Geolocation Policy: A 639 Document Format for Expressing Privacy Preferences for 640 Location Information", draft-ietf-geopriv-policy-26 (work 641 in progress), June 2012. 643 [I-D.ietf-geopriv-policy-uri] 644 Thomson, M., Winterbottom, J., Barnes, R., and H. 645 Tschofenig, "Location Configuration Extensions for Policy 646 Management", draft-ietf-geopriv-policy-uri-04 (work in 647 progress), November 2011. 649 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 650 A., Peterson, J., Sparks, R., Handley, M., and E. 651 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 652 June 2002. 654 [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and 655 J. Polk, "Geopriv Requirements", RFC 3693, February 2004. 657 [RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., 658 Polk, J., and J. Rosenberg, "Common Policy: A Document 659 Format for Expressing Privacy Preferences", RFC 4745, 660 February 2007. 662 [RFC4825] Rosenberg, J., "The Extensible Markup Language (XML) 663 Configuration Access Protocol (XCAP)", RFC 4825, May 2007. 665 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 666 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 668 [RFC5687] Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7 669 Location Configuration Protocol: Problem Statement and 670 Requirements", RFC 5687, March 2010. 672 [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet 673 Mail Extensions (S/MIME) Version 3.2 Message 674 Specification", RFC 5751, January 2010. 676 [RFC5808] Marshall, R., "Requirements for a Location-by-Reference 677 Mechanism", RFC 5808, May 2010. 679 [RFC6155] Winterbottom, J., Thomson, M., Tschofenig, H., and R. 680 Barnes, "Use of Device Identity in HTTP-Enabled Location 681 Delivery (HELD)", RFC 6155, March 2011. 683 [RFC6280] Barnes, R., Lepinski, M., Cooper, A., Morris, J., 684 Tschofenig, H., and H. Schulzrinne, "An Architecture for 685 Location and Location Privacy in Internet Applications", 686 BCP 160, RFC 6280, July 2011. 688 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 689 for the Session Initiation Protocol", RFC 6442, 690 December 2011. 692 Appendix A. GEOPRIV Using Protocol Compliance 694 This section describes how use of HELD as a location dereference 695 protocol complies with the GEOPRIV requirements described in 696 [RFC3693]. 698 Req. 1. (Location Object generalities): 700 This section relates to the PIDF-LO [RFC4119] document, 701 which is used by HELD. These requirements are addressed by 702 [RFC4119] and [RFC5491]. 704 Req. 2. (Location Object fields): 706 This section relates to the PIDF-LO [RFC4119] document, 707 which is used by HELD. These requirements are addressed by 708 [RFC4119] and [RFC5491]. 710 Req. 3. (Location Data Types): 712 This section relates to the PIDF-LO [RFC4119] document, 713 which is used by HELD. These requirements are addressed by 714 [RFC4119] and [RFC5491]. 716 Section 7.2 of [RFC3693] details the requirements of a "Using 717 Protocol". These requirements are restated, followed by a statement 718 of compliance: 720 Req. 4. "The using protocol has to obey the privacy and security 721 instructions coded in the Location Object and in the 722 corresponding Rules regarding the transmission and storage 723 of the LO." 725 Compliant: This specification describes the use of HTTP over 726 TLS for carring the PIDF-LO from the LS to the Location 727 Recipient. The sending and receiving parties are expected 728 to comply with the instructions carried inside the object. 730 Though discouraged, using unsecured http: URIs is permitted. 731 Using unsecured HTTP is likely to result in non-compliance 732 with this requirement. 734 Req. 5. "The using protocol will typically facilitate that the keys 735 associated with the credentials are transported to the 736 respective parties, that is, key establishment is the 737 responsibility of the using protocol." 739 Compliant: This document specifies that authentication of 740 the LS uses the established public key infrastructure used 741 by HTTP over TLS [RFC2818]. Authentication of Location 742 Recipients is either based on distribution of a secret (the 743 location URI) using a conveyance protocol (for instance, 744 [RFC6442]), allowances are made for later work to define 745 alternative methods. 747 Req. 6. "(Single Message Transfer) In particular, for tracking of 748 small target devices, the design should allow a single 749 message/packet transmission of location as a complete 750 transaction." 752 Not Compliant: The XML encoding specified in [RFC4119] is 753 not suited to single packet transfers. Use of compressed 754 content encoding [RFC2616] might allow this condition to be 755 met. 757 Section 7.3 of [RFC3693] details the requirements of a "Rule based 758 Location Data Transfer". These requirements are restated where they 759 are applicable to this document: 761 Req. 7. "(LS Rules) The decision of a Location Server to provide a 762 Location Recipient access to Location Information MUST be 763 based on Rule Maker-defined Privacy Rules." 765 Compliant: This document describes two alternative methods 766 by which a Rule Maker is able to control access to location 767 information. Rule Maker policy is enforced by the LS when 768 a location URI is dereferenced. However, this document 769 does not describe how a location URI is created, or how a 770 Rule Maker associates policy with a location URI. These 771 are covered by other specifications. 773 Req. 8. (LG Rules) Not Applicable: This relationship between LS and 774 the source of its information (be that Location Generator 775 (LG) or LIS) is out of scope for this document. 777 Req. 9. "(Viewer Rules) A Viewer does not need to be aware of the 778 full Rules defined by the Rule Maker (because a Viewer 779 SHOULD NOT retransmit Location Information), and thus a 780 Viewer SHOULD receive only the subset of Privacy Rules 781 necessary for the Viewer to handle the LO in compliance 782 with the full Privacy Rules (such as, instruction on the 783 time period for which the LO can be retained)." 785 Compliant: The Rule Maker might define (via mechanisms 786 outside the scope of this document) which policy rules are 787 disclosed to other entities. For instance, if [RFC4745] is 788 used to convey authorization policies from Rule Maker to 789 LS, this is possible using the parameters specified in 790 [I-D.ietf-geopriv-policy]. 792 In order to comply with these rules, a Location Recipient 793 MUST NOT redistribute a location URI without express 794 permission. Depending on the access control model, the 795 location URI might be secret (see Section 3.3 of 796 [RFC5808]). 798 Req. 10. (Full Rule language) Not Applicable: Note however that 799 Geopriv has defined a rule language capable of expressing a 800 wide range of privacy rules (see [RFC4745] and 801 [I-D.ietf-geopriv-policy]. 803 Req. 11. (Limited Rule language) Not Applicable: This requirement 804 applies to (and is addressed by) PIDF-LO [RFC4119]. 806 Section 7.4 of [RFC3693] details the requirements of "Location Object 807 Privacy and Security". These requirements are restated where they 808 are applicable to this document: 810 Req. 12. (Identity Protection) Compliant: Identity protection of the 811 Target is provided as long as both of the following 812 conditions are true: 814 (a) the location URI is not associated with the identity 815 of the Target in any context, and 817 (b) the PIDF-LO does not contain information about the 818 identity of the Target. 820 For instance, this requirement is complied with if the 821 protocol that conveys the location URI does not link the 822 identity of the Target to the location URI and the LS 823 doesn't include meaningful identification information in 824 the PIDF-LO document. Section 6 recommends that an 825 unlinked pseudonym is used by the LS. 827 Req. 13. (Credential Requirements) Compliant: The primary security 828 mechanism specified in this document is Transport Layer 829 Security. TLS offers the ability to use different types of 830 credentials, including symmetric, asymmetric credentials or 831 a combination of them. 833 Req. 14. (Security Features) Compliant: Geopriv defines a few 834 security requirements for the protection of Location 835 Objects such as mutual end-point authentication, data 836 object integrity, data object confidentiality and replay 837 protection. The ability to use Transport Layer security 838 fulfills most of these requirements. Authentication of 839 Location Recipients in this document relies on proof of a 840 shared secret - the location URI. This does not preclude 841 the addition of more robust authentication procedures. 843 Req. 15. (Minimal Crypto) Compliant: The mandatory to implement 844 ciphersuite is provided in the TLS layer security 845 specification. 847 Appendix B. Compliance to Location Reference Requirements 849 This section describes how HELD complies to the location reference 850 requirements stipulated in [RFC5808]. Compliance of [RFC5985] to the 851 Location Configuration Protocol is included. 853 Note that use of HELD as a location dereference protocol does not 854 necessarily imply that HELD is the corresponding LCP. This 855 document is still applicable to HTTP location URIs that are 856 acquired by other means. 858 B.1. Requirements for a Location Configuration Protocol 860 C1. "Location URI support: The location configuration protocol MUST 861 support a location reference in URI form." 863 Compliant: HELD only provides location references in URI form. 865 C2. "Location URI expiration: When a location URI has a limited 866 validity interval, its lifetime MUST be indicated." 868 Compliant: HELD indicates the expiry time of location URIs using 869 the "expires" attribute. [I-D.ietf-geopriv-policy-uri] provides 870 a way to control expiration of a location URI. 872 C3. "Location URI cancellation: The location configuration protocol 873 MUST support the ability to request a cancellation of a specific 874 location URI." 876 Compliant with Extension: [I-D.ietf-geopriv-policy-uri] 877 describes how a location URI can be cancelled through the 878 application of policy. Without extensions, HELD does not 879 provide a method for cancelling location URIs. 881 C4. "Location Information Masking: The location URI MUST ensure, by 882 default, through randomization and uniqueness, that the location 883 URI does not contain location information specific components." 885 Compliant: The HELD specification explicitly references this 886 requirement in providing guidance on the format of the location 887 URI. 889 C5. "Target Identity Protection: The location URI MUST NOT contain 890 information that identifies the Target (e.g., user or device)." 892 Compliant: The HELD specification provides specific guidance on 893 the anonymity of the Target with regards to the generation of 894 location URIs. Section 6 expands on this guidance. 896 C6. "Reuse indicator: There SHOULD be a way to allow a Target to 897 control whether a location URI can be resolved once only, or 898 multiple times." 900 Not Compliant: Specific extensions to the protocol or 901 authorization policy formats is needed to alter the default 902 behavior, which allows unlimited resolution of the location URI. 904 C7. "Selective disclosure: The location configuration protocol MUST 905 provide a mechanism that allows the Rule Maker to control what 906 information is being disclosed about the Target." 908 Compliant with Extension: Use of policy mechanisms and 909 [I-D.ietf-geopriv-policy-uri] enable this capability. Note that 910 this document recommends that only location information be 911 provided. 913 C8. "Location URI Not guessable: As a default, the location 914 configuration protocol MUST return location URIs that are random 915 and unique throughout the indicated lifetime. A location URI 916 with 128-bits of randomness is RECOMMENDED." 918 Compliant: HELD specifies that location URIs conform to this 919 requirement. The amount of randomness is not specifically 920 identified since it depends on a number of factors that change 921 over time, such as the number of valid location URIs, the 922 validity period of those URIs and the rate that guesses can be 923 made. 925 C9. "Location URI Options: In the case of user-provided 926 authorization policies, where anonymous or non-guessable 927 location URIs are not warranted, the location configuration 928 protocol MAY support a variety of optional location URI 929 conventions, as requested by a Target to a location 930 configuration server, (e.g., embedded location information 931 within the location URI)." 933 Not Compliant: HELD does not support Device-specified location 934 URI forms. 936 B.2. Requirements for a Location Dereference Protocol 938 D1. "Location URI support: The location dereference protocol MUST 939 support a location reference in URI form." 941 Compliant: HELD only provides location references in URI form. 943 D2. "Authentication: The location dereference protocol MUST include 944 mechanisms to authenticate both the client and the server." 946 Partially Compliant: TLS provides means for mutual 947 authentication. This document only specifies the required 948 mechanism for server authentication. Client authentication is 949 not precluded. 951 D3. "Dereferenced Location Form: The value returned by the 952 dereference protocol MUST contain a well-formed PIDF-LO 953 document." 955 Compliant: HELD requires that location objects are in the form 956 of a PIDF-LO that complies with [RFC5491]. 958 D4. "Location URI Repeated Use: The location dereference protocol 959 MUST support the ability for the same location URI to be 960 resolved more than once, based on dereference server 961 configuration." 963 Compliant: A Location Recipient may access and use a location 964 URI as many times as desired until URI expiration results in the 965 URI being invalidated. Authorization policies might include 966 rules that modify this behavior. 968 D5. "The location dereference protocol MUST support confidentiality 969 protection of messages sent between the Location Recipient and 970 the location server." 972 Compliant: This document strongly recommends the use of TLS for 973 confidentiality and HELD mandates its implementation. Unsecured 974 HTTP is permitted: the associated risks are described in 975 Section 3. 977 Authors' Addresses 979 James Winterbottom 980 Commscope 981 Andrew Building (39) 982 Wollongong University Campus 983 Northfields Avenue 984 Wollongong, NSW 2522 985 AU 987 Phone: +61 242 212938 988 Email: james.winterbottom@commscope.com 989 Hannes Tschofenig 990 Nokia Siemens Networks 991 Linnoitustie 6 992 Espoo 02600 993 Finland 995 Phone: +358 (50) 4871445 996 Email: Hannes.Tschofenig@gmx.net 997 URI: http://www.tschofenig.priv.at 999 Henning Schulzrinne 1000 Columbia University 1001 Department of Computer Science 1002 450 Computer Science Building, New York, NY 10027 1003 US 1005 Phone: +1 212 939 7004 1006 Email: hgs@cs.columbia.edu 1007 URI: http://www.cs.columbia.edu 1009 Martin Thomson 1010 (Unaffiliated) 1011 . 1012 Mountain View, CA 94043 1013 US 1015 Phone: +1 650-353-1925 1016 Email: martin.thomson@gmail.com