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Jennings 3 Internet-Draft Cisco 4 Intended status: Standards Track B. Lowekamp 5 Expires: October 19, 2016 Skype 6 E. Rescorla 7 RTFM, Inc. 8 S. Baset 9 H. Schulzrinne 10 Columbia University 11 T. Schmidt, Ed. 12 HAW Hamburg 13 April 17, 2016 15 A SIP Usage for RELOAD 16 draft-ietf-p2psip-sip-19 18 Abstract 20 This document defines a SIP Usage for REsource LOcation And Discovery 21 (RELOAD). The SIP Usage provides the functionality of a SIP proxy or 22 registrar in a fully-distributed system and includes a lookup service 23 for Address of Records (AORs) stored in the overlay. It also defines 24 Globally Routable User Agent URIs (GRUUs) that allow the 25 registrations to map an AOR to a specific node reachable through the 26 overlay. After such initial contact of a peer, the RELOAD AppAttach 27 method is used to establish a direct connection between nodes through 28 which SIP messages are exchanged. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on October 19, 2016. 47 Copyright Notice 49 Copyright (c) 2016 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 This document may contain material from IETF Documents or IETF 63 Contributions published or made publicly available before November 64 10, 2008. The person(s) controlling the copyright in some of this 65 material may not have granted the IETF Trust the right to allow 66 modifications of such material outside the IETF Standards Process. 67 Without obtaining an adequate license from the person(s) controlling 68 the copyright in such materials, this document may not be modified 69 outside the IETF Standards Process, and derivative works of it may 70 not be created outside the IETF Standards Process, except to format 71 it for publication as an RFC or to translate it into languages other 72 than English. 74 Table of Contents 76 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 77 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 78 3. Registering AORs in the Overlay . . . . . . . . . . . . . . . 5 79 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6 80 3.2. Data Structure . . . . . . . . . . . . . . . . . . . . . 6 81 3.3. Access Control . . . . . . . . . . . . . . . . . . . . . 8 82 3.4. Overlay Configuration Document Extension . . . . . . . . 9 83 4. Looking up an AOR . . . . . . . . . . . . . . . . . . . . . . 10 84 4.1. Finding a Route to an AOR . . . . . . . . . . . . . . . . 10 85 4.2. Resolving an AOR . . . . . . . . . . . . . . . . . . . . 11 86 5. Forming a Direct Connection . . . . . . . . . . . . . . . . . 11 87 5.1. Setting Up a Connection . . . . . . . . . . . . . . . . . 11 88 5.2. Keeping a Connection Alive . . . . . . . . . . . . . . . 12 89 6. Using GRUUs . . . . . . . . . . . . . . . . . . . . . . . . . 12 90 7. SIP-REGISTRATION Kind Definition . . . . . . . . . . . . . . 13 91 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 92 8.1. RELOAD-Specific Issues . . . . . . . . . . . . . . . . . 14 93 8.2. SIP-Specific Issues . . . . . . . . . . . . . . . . . . . 14 94 8.2.1. Fork Explosion . . . . . . . . . . . . . . . . . . . 14 95 8.2.2. Malicious Retargeting . . . . . . . . . . . . . . . . 14 96 8.2.3. Misuse of AORs . . . . . . . . . . . . . . . . . . . 15 97 8.2.4. Privacy Issues . . . . . . . . . . . . . . . . . . . 15 98 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 99 9.1. Data Kind-ID . . . . . . . . . . . . . . . . . . . . . . 15 100 9.2. XML Name Space Registration . . . . . . . . . . . . . . . 16 101 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 102 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 103 11.1. Normative References . . . . . . . . . . . . . . . . . . 16 104 11.2. Informative References . . . . . . . . . . . . . . . . . 18 105 Appendix A. Third Party Registration . . . . . . . . . . . . . . 18 106 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18 107 B.1. Changes since draft-ietf-p2psip-sip-09 . . . . . . . . . 18 108 B.2. Changes since draft-ietf-p2psip-sip-08 . . . . . . . . . 19 109 B.3. Changes since draft-ietf-p2psip-sip-07 . . . . . . . . . 19 110 B.4. Changes since draft-ietf-p2psip-sip-06 . . . . . . . . . 19 111 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 113 1. Introduction 115 REsource LOcation And Discovery (RELOAD) [RFC6940] specifies a peer- 116 to-peer (P2P) signaling protocol for the general use on the Internet. 117 This document defines a SIP Usage of RELOAD that allows SIP [RFC3261] 118 user agents (UAs) to establish peer-to-peer SIP (or SIPS) sessions 119 without the requirement for permanent proxy or registration servers, 120 e.g., a fully distributed telephony service. In such a network, the 121 RELOAD overlay itself performs the registration and rendezvous 122 functions ordinarily associated with such servers. 124 The SIP Usage involves two basic functions. 126 Registration: SIP UAs can use the RELOAD data storage functionality 127 to store a mapping from their address-of-record (AOR) to their 128 Node-ID in the overlay, and to retrieve the Node-ID of other UAs. 130 Rendezvous: Once a SIP UA has identified the Node-ID for an AOR it 131 wishes to call, it can use the RELOAD message routing system to 132 set up a direct connection for exchanging SIP messages. 134 Mappings are stored in the SipRegistration Resource Record defined in 135 this document. All operations required to perform a SIP registration 136 or rendezvous are standard RELOAD protocol methods. 138 For example, Bob registers his AOR, "bob@dht.example.com", for his 139 Node-ID "1234". When Alice wants to call Bob, she queries the 140 overlay for "bob@dht.example.com" and receives Node-ID "1234" in 141 return. She then uses the overlay routing to establish a direct 142 connection with Bob and can directly transmit a standard SIP INVITE. 143 In detail, this works along the following steps. 145 1. Bob, operating Node-ID "1234", stores a mapping from his AOR to 146 his Node-ID in the overlay by applying a Store request for 147 "bob@dht.example.com -> 1234". 149 2. Alice, operating Node-ID "5678", decides to call Bob. She 150 retrieves Node-ID "1234" by performing a Fetch request on 151 "bob@dht.example.com". 153 3. Alice uses the overlay to route an AppAttach message to Bob's 154 peer (ID "1234"). Bob responds with his own AppAttach and they 155 set up a direct connection, as shown in Figure 1. Note that 156 mutual Interactive Connectivity Establishment (ICE) checks are 157 invoked automatically from AppAttach message exchange. 159 Overlay 160 Alice Peer1 ... PeerN Bob 161 (5678) (1234) 162 ------------------------------------------------- 163 AppAttach -> 164 AppAttach -> 165 AppAttach -> 166 AppAttach -> 167 <- AppAttach 168 <- AppAttach 169 <- AppAttach 170 <- AppAttach 172 <------------------ ICE Checks -----------------> 173 INVITE -----------------------------------------> 174 <--------------------------------------------- OK 175 ACK --------------------------------------------> 176 <------------ ICE Checks for media -------------> 177 <-------------------- RTP ----------------------> 179 Figure 1: Connection setup in P2P SIP using the RELOAD overlay 181 It is important to note that here the only role of RELOAD is to set 182 up the direct SIP connection between Alice and Bob. As soon as the 183 ICE checks complete and the connection is established, ordinary SIP 184 or SIPS is used. In particular, the establishment of the media 185 channel for a phone call happens via the usual SIP mechanisms, and 186 RELOAD is not involved. Media never traverses the overlay. After 187 the successful exchange of SIP messages, call peers run ICE 188 connectivity checks for media. 190 In addition to mappings from AORs to Node-IDs, the SIP Usage also 191 allows mappings from AORs to other AORs. This enables an indirection 192 useful for call forwarding. For instance, if Bob wants his phone 193 calls temporarily forwarded to Charlie, he can store the mapping 194 "bob@dht.example.com -> charlie@dht.example.com". When Alice wants 195 to call Bob, she retrieves this mapping and can then fetch Charlie's 196 AOR to retrieve his Node-ID. These mechanisms are described in 197 Section 3. 199 Alternatively, Globally Routable User Agent URIs (GRUUs) can be used 200 for directly accessing peers. They are handled via a separate 201 mechanism, as described in Section 6. 203 The SIP Usage for RELOAD addresses a fully distributed deployment of 204 session-based services among overlay peers. This RELOAD usage may be 205 relevant in a variety of environments, including a highly regulated 206 environment of a "single provider" that admits parties using AORs 207 with domains from controlled namespace(s) only, or an open, multi- 208 party infrastructure that liberally allows a registration and 209 rendezvous for various or any domain namespace. It is noteworthy in 210 this context that - in contrast to regular SIP - domain names play no 211 role in routing to a proxy server. Once connectivity to an overlay 212 is given, any name registration can be technically processed. 214 2. Terminology 216 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 217 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 218 document are to be interpreted as described in RFC 2119 [RFC2119]. 220 We use the terminology and definitions from Concepts and Terminology 221 for Peer to Peer SIP [I-D.ietf-p2psip-concepts] and the RELOAD Base 222 Protocol [RFC6940] extensively in this document. 224 In addition, term definitions from SIP [RFC3261] apply to this memo. 225 The term AOR is the SIP "Address of Record" used to identify a user 226 in SIP. For example, alice@example.com could be the AOR for Alice. 227 For the purposes of this specification, an AOR is considered not to 228 include the scheme (e.g. sip:) as the AOR needs to match the 229 rfc822Name in the X509v3 certificates [RFC5280]. It is worth noting 230 that SIP and SIPS are distinguished in P2PSIP by the Application-ID. 232 3. Registering AORs in the Overlay 233 3.1. Overview 235 In ordinary SIP, a UA registers its AOR and location with a 236 registrar. In RELOAD, this registrar function is provided by the 237 overlay as a whole. To register its location, a RELOAD peer stores a 238 SipRegistration Resource Record under its own AOR using the SIP- 239 REGISTRATION Kind, which is formally defined in Section 7. Note that 240 the registration lifetime known from the regular SIP REGISTER method 241 is inherited from the lifetime attribute of the basic RELOAD 242 StoredData structure (see Section 7 in [RFC6940]). 244 A RELOAD overlay MAY restrict the storage of AORs. Namespaces (i.e., 245 the right hand side of the AOR) that are supported for registration 246 and lookup can be configured for each RELOAD deployment as described 247 in Section 3.4. 249 As a simple example, consider Alice with AOR "alice@dht.example.org" 250 at Node-ID "1234". She might store the mapping 251 "alice@dht.example.org -> 1234" telling anyone who wants to call her 252 to contact node "1234". 254 RELOAD peers can store two kinds of SIP mappings, 256 o from an AOR to a destination list (a single Node-ID is just a 257 trivial destination list), or 259 o from an AOR to another AOR. 261 The meaning of the first kind of mapping is "in order to contact me, 262 form a connection with this peer." The meaning of the second kind of 263 mapping is "in order to contact me, dereference this AOR". The 264 latter allows for forwarding. For instance, if Alice wants her calls 265 to be forwarded to her secretary, Sam, she might insert the following 266 mapping "alice@dht.example.org -> sam@dht.example.org". 268 3.2. Data Structure 270 This section defines the SipRegistration Resource Record as follows: 272 enum { sip_registration_uri(1), sip_registration_route(2), 273 (255) } SipRegistrationType; 275 select (SipRegistration.type) { 276 case sip_registration_uri: 277 opaque uri<0..2^16-1>; 279 case sip_registration_route: 280 opaque contact_prefs<0..2^16-1>; 281 Destination destination_list<0..2^16-1>; 283 /* This type can be extended */ 285 } SipRegistrationData; 287 struct { 288 SipRegistrationType type; 289 uint16 length; 290 SipRegistrationData data; 291 } SipRegistration; 293 The contents of the SipRegistration Resource Record are: 295 type 297 the type of the registration 299 length 301 the length of the rest of the PDU 303 data 305 the registration data 307 o If the registration is of type "sip_registration_uri", then the 308 contents are an opaque string containing the AOR. 310 o If the registration is of type "sip_registration_route", then the 311 contents are an opaque string containing the callee's contact 312 preferences and a destination list for the peer. 314 The callee expresses its capabilities within the contact preferences 315 as specified in [RFC3840]. It encodes a media feature set comprised 316 of its capabilities as a contact predicate, i.e., a string of feature 317 parameters that appear as part of the Contact header field. Feature 318 parameters are derived from the media feature set syntax of [RFC2533] 319 (see also [RFC2738]) as described in [RFC3840]. 321 This encoding covers all SIP User Agent capabilities, as defined in 322 [RFC3840] and registered in the SIP feature tag registration tree. 323 In particular, a callee can indicate that it prefers contact via a 324 particular SIP scheme - SIP or SIPS - by using one of the following 325 contact_prefs attribute: 327 (sip.schemes=SIP) 328 (sip.schemes=SIPS) 330 RELOAD explicitly supports multiple registrations for a single AOR. 331 The registrations are stored in a Dictionary with Node-IDs as the 332 dictionary keys. Consider, for instance, the case where Alice has 333 two peers: 335 o her desk phone (1234) 337 o her cell phone (5678) 339 Alice might store the following in the overlay at resource 340 "alice@dht.example.com". 342 o A SipRegistration of type "sip_registration_route" with dictionary 343 key "1234" and value "1234". 345 o A SipRegistration of type "sip_registration_route" with dictionary 346 key "5678" and value "5678". 348 Note that this structure explicitly allows one Node-ID to forward to 349 another Node-ID. For instance, Alice could set calls to her desk 350 phone to ring at her cell phone by storing a SipRegistration of type 351 "sip_registration_route" with dictionary key "1234" and value "5678". 353 3.3. Access Control 355 In order to prevent hijacking or other misuse, registrations are 356 subject to access control rules. Two kinds of restrictions apply: 358 o A Store is permitted only for AORs with domain names that fall 359 into the namespaces supported by the RELOAD overlay instance. 361 o Storing requests are performed according to the USER-NODE-MATCH 362 access control policy of RELOAD. 364 Before issuing a Store request to the overlay, any peer SHOULD verify 365 that the AOR of the request is a valid Resource Name with respect to 366 its domain name and the namespaces defined in the overlay 367 configuration document (see Section 3.4). 369 Before a Store is permitted, the storing peer MUST check that: 371 o The AOR of the request is a valid Resource Name with respect to 372 the namespaces defined in the overlay configuration document. 374 o The certificate contains a username that is a SIP AOR which hashes 375 to the Resource-ID it is being stored at. 377 o The certificate contains a Node-ID that is the same as the 378 dictionary key it is being stored at. 380 If any of these checks fail, the request MUST be rejected with an 381 Error_Forbidden error. 383 Note that these rules permit Alice to forward calls to Bob without 384 his permission. However, they do not permit Alice to forward Bob's 385 calls to her. See Section 8.2.2 for additional descriptions. 387 3.4. Overlay Configuration Document Extension 389 The use of a SIP-enabled overlay MAY be restricted to users with AORs 390 from specific domains. When deploying an overlay service, providers 391 can decide about these use case scenarios by defining a set of 392 namespaces for admissible domain names. This section extends the 393 overlay configuration document by defining new elements for patterns 394 that describe a corresponding domain name syntax. 396 A RELOAD overlay can be configured to accept store requests for any 397 AOR, or to apply domain name restrictions. To apply restrictions, 398 the overlay configuration document needs to contain a element. The element serves as a 400 container for zero to multiple sub-elements. A 401 element MAY be present if the "enable" attribute of its parent 402 element is set to true. Each element defines a pattern for 403 constructing admissible resource names. It is of type xsd:string and 404 interpreted as a regular expression according to "POSIX Extended 405 Regular Expression" (see the specifications in [IEEE-Posix]). 407 Encoding of the domain name complies to the restricted ASCII 408 character set without character escaping as defined in Section 19.1 409 of [RFC3261]. 411 Inclusion of a element in an overlay 412 configuration document is OPTIONAL. If the element is not included, 413 the default behavior is to accept any AOR. If the element is 414 included and the "enable" attribute is not set or set to false, the 415 overlay MUST only accept AORs that match the domain name of the 416 overlay. If the element is included and the "enable" attribute is 417 set to true, the overlay MUST only accept AORs that match patterns 418 specified in the element. 420 Example of Domain Patterns: 421 dht\.example\.com 422 .*\.my\.example 424 In this example, any AOR will be accepted that is either of the form 425 @dht.example.com, or ends with the domain "my.example". 427 The Relax NG Grammar for the AOR Domain Restriction reads: 429 # AOR DOMAIN RESTRICTION URN SUB-NAMESPACE 431 namespace sip = "urn:ietf:params:xml:ns:p2p:config-base:sip" 433 # AOR DOMAIN RESTRICTION ELEMENT 435 Kind-parameter &= element sip:domain-restriction { 437 attribute enable { xsd:boolean } 439 # PATTERN ELEMENT 441 element sip:pattern { xsd:string }* 442 }? 444 4. Looking up an AOR 446 4.1. Finding a Route to an AOR 448 A RELOAD user, member of an overlay, who wishes to call another user 449 with given AOR SHALL proceed in the following way. 451 AOR is GRUU? If the AOR is a GRUU for this overlay, the callee can 452 be contacted directly as described in Section 6. 454 AOR domain is hosted in overlay? If the domain part of the AOR 455 matches a domain pattern configured in the overlay, the user can 456 continue to resolve the AOR in this overlay. The user MAY choose 457 to query the DNS service records to search for additional support 458 of this domain name. 460 AOR domain not supported by overlay? If the domain part of the AOR 461 is not supported in the current overlay, the user SHOULD query the 462 DNS (or other discovery services at hand) to search for an 463 alternative overlay that services the AOR under request. 464 Alternatively, standard SIP procedures for contacting the callee 465 SHOULD be used. 467 AOR inaccessible? If all of the above contact attempts fail, the 468 call fails. 470 The procedures described above likewise apply when nodes are 471 simultaneously connected to several overlays. 473 4.2. Resolving an AOR 475 A RELOAD user that has discovered a route to an AOR in the current 476 overlay SHALL execute the following steps. 478 1. Perform a Fetch for Kind SIP-REGISTRATION at the Resource-ID 479 corresponding to the AOR. This Fetch SHOULD NOT indicate any 480 dictionary keys, so that it will fetch all the stored values. 482 2. If any of the results of the Fetch are non-GRUU AORs, then repeat 483 step 1 for that AOR. 485 3. Once only GRUUs and destination lists remain, the peer removes 486 duplicate destination lists and GRUUs from the list and initiates 487 SIP or SIPS connections to the appropriate peers as described in 488 the following sections. If there are also external AORs, the 489 peer follows the appropriate procedure for contacting them as 490 well. 492 5. Forming a Direct Connection 494 5.1. Setting Up a Connection 496 Once the peer has translated the AOR into a set of destination lists, 497 it then uses the overlay to route AppAttach messages to each of those 498 peers. The "application" field MUST be either 5060 to indicate SIP 499 or 5061 for using SIPS. If certificate-based authentication is in 500 use, the responding peer MUST present a certificate with a Node-ID 501 matching the terminal entry in the destination list. Otherwise, the 502 connection MUST NOT be used and MUST be closed. Note that it is 503 possible that the peers already have a RELOAD connection mutually 504 established. This MUST NOT be used for SIP messages unless it is a 505 SIP connection. A previously established SIP connection MAY be used 506 for a new call. 508 Once the AppAttach succeeds, the peer sends plain or (D)TLS encrypted 509 SIP messages over the connection as in normal SIP. A caller MAY 510 choose to contact the callee using SIP or secure SIPS, but SHOULD 511 follow a preference indicated by the callee in its contact_prefs 512 attribute (see Section 3.2). A callee MAY choose to listen on both 513 SIP and SIPS ports and accept calls from either SIP schemes, or 514 select a single one. However, a callee that decides to accept SIPS 515 calls, only, SHOULD indicate its choice by setting the corresponding 516 attribute in its contact_prefs. It is noteworthy that according to 517 [RFC6940] all overlay links are built on (D)TLS secured transport. 518 While hop-wise encrypted paths do not prevent the use of plain SIP, 519 SIPS requires end-to-end protection that may include client links and 520 endpoint certificates. 522 SIP messages carry the SIP URIs of actual overlay endpoints (e.g., 523 "sip:alice@dht.example.com") in the Via and Contact headers, while 524 the communication continues via the RELOAD connection. However, a UA 525 can redirect its communication path by setting an alternate Contact 526 header field like in ordinary SIP. 528 5.2. Keeping a Connection Alive 530 In many cases, RELOAD connections will traverse NATs and Firewalls 531 that maintain states established from ICE [RFC5245] negotiations. It 532 is the responsibility of the Peers to provide sufficiently frequent 533 traffic to keep NAT and Firewall states present and the connection 534 alive. Keepalives are a mandatory component of ICE (see Section 10 535 of [RFC5245]) and no further operations are required. Applications 536 that want to assure maintenance of sessions individually need to 537 follow regular SIP means. Accordingly, a SIP Peer MAY apply keep- 538 alive techniques in agreement with its transport binding as defined 539 in Section 3.5 of [RFC5626]. 541 6. Using GRUUs 543 Globally Routable User Agent URIs (GRUUs) [RFC5627] have been 544 designed to allow direct routing without the indirection of a SIP 545 proxy function. The concept is transferred to RELOAD overlays as 546 follows. GRUUs in RELOAD are constructed by embedding a 547 base64-encoded destination list in the "gr" URI parameter of the 548 GRUU. The base64 encoding is done with the alphabet specified in 549 table 1 of [RFC4648] with the exception that ~ is used in place of =. 551 Example of a RELOAD GRUU: 552 alice@example.com;gr=MDEyMzQ1Njc4OTAxMjM0NTY3ODk~ 554 GRUUs do not require to store data in the Overlay Instance. Rather 555 when a peer needs to route a message to a GRUU in the same P2P 556 overlay, it simply uses the destination list and connects to that 557 peer. Because a GRUU contains a destination list, it can have the 558 same contents as a destination list stored elsewhere in the resource 559 dictionary. 561 Anonymous GRUUs [RFC5767] are constructed analogously, but require 562 either that the enrollment server issues a different Node-ID for each 563 anonymous GRUU required, or that a destination list be used that 564 includes a peer that compresses the destination list to stop the 565 Node-ID from being revealed. 567 7. SIP-REGISTRATION Kind Definition 569 This section defines the SIP-REGISTRATION Kind. 571 Name SIP-REGISTRATION 573 Kind IDs The Resource Name for the SIP-REGISTRATION Kind-ID is the 574 AOR of the user as specified in Section 2. The data stored is a 575 SipRegistration, which can contain either another URI or a 576 destination list to the peer which is acting for the user. 578 Data Model The data model for the SIP-REGISTRATION Kind-ID is 579 dictionary. The dictionary key is the Node-ID of the storing 580 peer. This allows each peer (presumably corresponding to a single 581 device) to store a single route mapping. 583 Access Control USER-NODE-MATCH. Note that this matches the SIP AOR 584 against the rfc822Name in the X509v3 certificate. The rfc822Name 585 does not include the scheme so that the "sip:" prefix needs to be 586 removed from the SIP AOR before matching. Escaped characters ('%' 587 encoding) in the SIP AOR also need to be decoded prior to 588 matching. 590 Data stored under the SIP-REGISTRATION Kind is of type 591 SipRegistration. This comes in two varieties: 593 sip_registration_uri 595 a URI which the user can be reached at. 597 sip_registration_route 599 a destination list which can be used to reach the user's peer. 601 8. Security Considerations 603 8.1. RELOAD-Specific Issues 605 This Usage for RELOAD does not define new protocol elements or 606 operations. Hence no new threats arrive from message exchanges in 607 RELOAD. 609 This document introduces an AOR domain restriction function that must 610 be surveyed by the storing peer. A misconfigured or malicious peer 611 could cause frequent rejects of illegitimate storing requests. 612 However, domain name control relies on a lightweight pattern matching 613 and can be processed prior to validating certificates. Hence no 614 extra burden is introduced for RELOAD peers beyond loads already 615 present in the base protocol. 617 8.2. SIP-Specific Issues 619 8.2.1. Fork Explosion 621 Because SIP includes a forking capability (the ability to retarget to 622 multiple recipients), fork bombs are a potential DoS concern. 623 However, in the SIP usage of RELOAD, fork bombs are a much lower 624 concern than in a conventional SIP Proxy infrastructure, because the 625 calling party is involved in each retargeting event. It can 626 therefore directly measure the number of forks and throttle at some 627 reasonable number. 629 8.2.2. Malicious Retargeting 631 Another potential DoS attack is for the owner of an attractive AOR to 632 retarget all calls to some victim. This attack is common to SIP and 633 difficult to ameliorate without requiring the target of a SIP 634 registration to authorize all stores. The overhead of that 635 requirement would be excessive and in addition there are good use 636 cases for retargeting to a peer without its explicit cooperation. 638 8.2.3. Misuse of AORs 640 A RELOAD overlay and enrollment service that liberally accept 641 registrations for AORs of domain names unrelated to the overlay 642 instance and without further authorisation, eventually store presence 643 state for misused AORs. An attacker could hijack names, register a 644 bogus presence and attract calls dedicated to a victim that resides 645 within or outside the Overlay Instance. 647 A hijacking of AORs can be mitigated by restricting the name spaces 648 admissible in the Overlay Instance, or by additional verification 649 actions of the enrollment service. To prevent an (exclusive) routing 650 to a bogus registration, a caller can in addition query the DNS (or 651 other discovery services at hand) to search for an alternative 652 presence of the callee in another overlay or a normal SIP 653 infrastructure. 655 8.2.4. Privacy Issues 657 All RELOAD SIP registration data is visible to all nodes in the 658 overlay. Location privacy can be gained from using anonymous GRUUs. 659 Methods of providing anonymity or deploying pseudonyms exist, but are 660 beyond the scope of this document. 662 9. IANA Considerations 664 9.1. Data Kind-ID 666 IANA shall register the following code point in the "RELOAD Data 667 Kind-ID" Registry (cf., [RFC6940]) to represent the SIP-REGISTRATION 668 Kind, as described in Section 7. [NOTE TO IANA/RFC-EDITOR: Please 669 replace RFC-AAAA with the RFC number for this specification in the 670 following list.] 672 +---------------------+------------+----------+ 673 | Kind | Kind-ID | RFC | 674 +---------------------+------------+----------+ 675 | SIP-REGISTRATION | 1 | RFC-AAAA | 676 +---------------------+------------+----------+ 678 9.2. XML Name Space Registration 680 This document registers the following URI for the config XML 681 namespace in the IETF XML registry defined in [RFC3688] 683 URI: urn:ietf:params:xml:ns:p2p:config-base:sip 685 Registrant Contact: The IESG 687 XML: N/A, the requested URI is an XML namespace 689 10. Acknowledgments 691 This document was generated in parts from initial drafts and 692 discussions in the early specification phase of the P2PSIP base 693 protocol. Significant contributions (in alphabetical order) were 694 from David A. Bryan, James Deverick, Marcin Matuszewski, Jonathan 695 Rosenberg, and Marcia Zangrilli, which is gratefully acknowledged. 697 Additional thanks go to all those who helped with ideas, discussions, 698 and reviews, in particular (in alphabetical order) Roland Bless, 699 Michael Chen, Alissa Cooper, Marc Petit-Huguenin, Brian Rosen, Meral 700 Shirazipour, and Matthias Waehlisch. 702 11. References 704 11.1. Normative References 706 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 707 Requirement Levels", BCP 14, RFC 2119, 708 DOI 10.17487/RFC2119, March 1997, 709 . 711 [RFC6940] Jennings, C., Lowekamp, B., Ed., Rescorla, E., Baset, S., 712 and H. Schulzrinne, "REsource LOcation And Discovery 713 (RELOAD) Base Protocol", RFC 6940, DOI 10.17487/RFC6940, 714 January 2014, . 716 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 717 A., Peterson, J., Sparks, R., Handley, M., and E. 718 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 719 DOI 10.17487/RFC3261, June 2002, 720 . 722 [RFC2533] Klyne, G., "A Syntax for Describing Media Feature Sets", 723 RFC 2533, DOI 10.17487/RFC2533, March 1999, 724 . 726 [RFC2738] Klyne, G., "Corrections to "A Syntax for Describing Media 727 Feature Sets"", RFC 2738, DOI 10.17487/RFC2738, December 728 1999, . 730 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 731 DOI 10.17487/RFC3688, January 2004, 732 . 734 [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, 735 "Indicating User Agent Capabilities in the Session 736 Initiation Protocol (SIP)", RFC 3840, 737 DOI 10.17487/RFC3840, August 2004, 738 . 740 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 741 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 742 . 744 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 745 (ICE): A Protocol for Network Address Translator (NAT) 746 Traversal for Offer/Answer Protocols", RFC 5245, 747 DOI 10.17487/RFC5245, April 2010, 748 . 750 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 751 Housley, R., and W. Polk, "Internet X.509 Public Key 752 Infrastructure Certificate and Certificate Revocation List 753 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 754 . 756 [RFC5626] Jennings, C., Ed., Mahy, R., Ed., and F. Audet, Ed., 757 "Managing Client-Initiated Connections in the Session 758 Initiation Protocol (SIP)", RFC 5626, 759 DOI 10.17487/RFC5626, October 2009, 760 . 762 [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User 763 Agent URIs (GRUUs) in the Session Initiation Protocol 764 (SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009, 765 . 767 [IEEE-Posix] 768 "IEEE Standard for Information Technology - Portable 769 Operating System Interface (POSIX) - Part 2: Shell and 770 Utilities (Vol. 1)", IEEE Std 1003.2-1992, ISBN 771 1-55937-255-9, January 1993. 773 11.2. Informative References 775 [I-D.ietf-p2psip-concepts] 776 Bryan, D., Matthews, P., Shim, E., Willis, D., and S. 777 Dawkins, "Concepts and Terminology for Peer to Peer SIP", 778 draft-ietf-p2psip-concepts-08 (work in progress), February 779 2016. 781 [RFC5767] Munakata, M., Schubert, S., and T. Ohba, "User-Agent- 782 Driven Privacy Mechanism for SIP", RFC 5767, 783 DOI 10.17487/RFC5767, April 2010, 784 . 786 [I-D.ietf-p2psip-share] 787 Knauf, A., Schmidt, T., Hege, G., and M. Waehlisch, "A 788 Usage for Shared Resources in RELOAD (ShaRe)", draft-ietf- 789 p2psip-share-08 (work in progress), March 2016. 791 Appendix A. Third Party Registration 793 In traditional SIP, the mechanism of a third party registration 794 (i.e., an assistant acting for a boss, changing users register a 795 role-based AOR, ...) is defined in Section 10.2 of [RFC3261]. This 796 is a REGISTER which uses the URI of the third-party in its From 797 header and cannot be translated directly into a P2PSIP registration, 798 because only the owner of the certificate can store a SIP- 799 REGISTRATION in a RELOAD overlay. 801 A way to implement third party registration is by using the extended 802 access control mechanism USER-CHAIN-ACL defined in 803 [I-D.ietf-p2psip-share]. Creating a new Kind "SIP-3P-REGISTRATION" 804 that is ruled by USER-CHAIN-ACL allows the owner of the certificate 805 to delegate the right for registration to individual third parties. 806 In this way, original SIP functionality can be regained without 807 weakening the security control of RELOAD. 809 Appendix B. Change Log 811 B.1. Changes since draft-ietf-p2psip-sip-09 813 o Added subsection on keepalive 815 o Updated references 817 B.2. Changes since draft-ietf-p2psip-sip-08 819 o Added the handling of SIPS 821 o Specified use of Posix regular expressions in configuration 822 document 824 o Added IANA registration for namespace 826 o Editorial polishing 828 o Updated and extended references 830 B.3. Changes since draft-ietf-p2psip-sip-07 832 o Cleared open issues 834 o Clarified use cases after WG discussion 836 o Added configuration document extensions for configurable domain 837 names 839 o Specified format of contact_prefs 841 o Clarified routing to AORs 843 o Extended security section 845 o Added Appendix on Third Party Registration 847 o Added IANA code points 849 o Editorial polishing 851 o Updated and extended references 853 B.4. Changes since draft-ietf-p2psip-sip-06 855 o Added Open Issue 857 Authors' Addresses 858 Cullen Jennings 859 Cisco 860 170 West Tasman Drive 861 MS: SJC-21/2 862 San Jose, CA 95134 863 USA 865 Phone: +1 408 421-9990 866 Email: fluffy@cisco.com 868 Bruce B. Lowekamp 869 Skype 870 Palo Alto, CA 871 USA 873 Email: bbl@lowekamp.net 875 Eric Rescorla 876 RTFM, Inc. 877 2064 Edgewood Drive 878 Palo Alto, CA 94303 879 USA 881 Phone: +1 650 678 2350 882 Email: ekr@rtfm.com 884 Salman A. Baset 885 Columbia University 886 1214 Amsterdam Avenue 887 New York, NY 888 USA 890 Email: salman@cs.columbia.edu 892 Henning Schulzrinne 893 Columbia University 894 1214 Amsterdam Avenue 895 New York, NY 896 USA 898 Email: hgs@cs.columbia.edu 899 Thomas C. Schmidt (editor) 900 HAW Hamburg 901 Berliner Tor 7 902 Hamburg 20099 903 Germany 905 Email: t.schmidt@haw-hamburg.de