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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 5988 (Obsoleted by RFC 8288) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 XMPP Working Group L. Stout, Ed. 3 Internet-Draft &yet 4 Intended status: Standards Track J. Moffitt 5 Expires: October 22, 2014 Mozilla 6 E. Cestari 7 cstar industries 8 April 20, 2014 10 An XMPP Sub-protocol for WebSocket 11 draft-ietf-xmpp-websocket-04 13 Abstract 15 This document defines a binding for the XMPP protocol over a 16 WebSocket transport layer. A WebSocket binding for XMPP provides 17 higher performance than the current HTTP binding for XMPP. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on October 22, 2014. 36 Copyright Notice 38 Copyright (c) 2014 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. XMPP Sub-Protocol . . . . . . . . . . . . . . . . . . . . . . 3 56 3.1. Handshake . . . . . . . . . . . . . . . . . . . . . . . . 3 57 3.2. WebSocket Messages . . . . . . . . . . . . . . . . . . . 4 58 3.3. XMPP Framing . . . . . . . . . . . . . . . . . . . . . . 4 59 3.3.1. Framed XML Stream . . . . . . . . . . . . . . . . . . 4 60 3.3.2. Framed Stream Namespace . . . . . . . . . . . . . . . 5 61 3.3.3. Stream Frames . . . . . . . . . . . . . . . . . . . . 5 62 3.4. Stream Initiation . . . . . . . . . . . . . . . . . . . . 6 63 3.5. Stream Errors . . . . . . . . . . . . . . . . . . . . . . 7 64 3.6. Closing the Connection . . . . . . . . . . . . . . . . . 7 65 3.6.1. see-other-uri . . . . . . . . . . . . . . . . . . . . 8 66 3.7. Stream Restarts . . . . . . . . . . . . . . . . . . . . . 8 67 3.8. Pings and Keepalives . . . . . . . . . . . . . . . . . . 8 68 3.9. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . 9 69 3.10. Stream Management . . . . . . . . . . . . . . . . . . . . 9 70 4. Discovering the WebSocket Connection Method . . . . . . . . . 9 71 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 72 5.1. WebSocket Subprotocol Name . . . . . . . . . . . . . . . 10 73 5.2. URN Sub-Namespace . . . . . . . . . . . . . . . . . . . . 10 74 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 75 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 76 7.1. Normative References . . . . . . . . . . . . . . . . . . 11 77 7.2. Informative References . . . . . . . . . . . . . . . . . 11 78 Appendix A. XML Schema . . . . . . . . . . . . . . . . . . . . . 12 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 81 1. Introduction 83 Applications using the Extensible Messaging and Presence Protocol 84 (XMPP) (see [RFC6120] and [RFC6121]) on the Web currently make use of 85 BOSH (see [XEP-0124] and [XEP-0206]), an XMPP binding to HTTP. BOSH 86 is based on the HTTP long polling technique, and it suffers from high 87 transport overhead compared to XMPP's native binding to TCP. In 88 addition, there are a number of other known issues with long polling 89 [RFC6202], which have an impact on BOSH-based systems. 91 It would be much better in most circumstances to avoid tunneling XMPP 92 over HTTP long polled connections and instead use the XMPP protocol 93 directly. However, the APIs and sandbox that browsers have provided 94 do not allow this. The WebSocket protocol [RFC6455] exists to solve 95 these kinds of problems and is a bidirectional protocol that provides 96 a simple message-based framing layer over raw sockets, allowing for 97 more robust and efficient communication in web applications. 99 The WebSocket protocol enables two-way communication between a client 100 and a server, effectively emulating TCP at the application layer and 101 therefore overcoming many of the problems with existing long-polling 102 techniques for bidirectional HTTP. This document defines a WebSocket 103 sub-protocol for XMPP. 105 2. Terminology 107 The basic unit of framing in the WebSocket protocol is called a 108 message. In XMPP, the basic unit is the stanza, which is a subset of 109 the first-level children of each document in an XMPP stream (see 110 Section 9 of [RFC6120]). XMPP also has a concept of messages, which 111 are stanzas with a top-level element of . In this 112 document, the word "message" will mean a WebSocket message, not an 113 XMPP message stanza, unless otherwise noted. 115 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 116 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 117 "OPTIONAL" in this document are to be interpreted as described in 118 [RFC2119]. 120 3. XMPP Sub-Protocol 122 3.1. Handshake 124 The XMPP sub-protocol is used to transport XMPP over a WebSocket 125 connection. The client and server agree to this protocol during the 126 WebSocket handshake (see Section 1.3 of [RFC6455]). 128 During the WebSocket handshake, the client MUST include the |Sec- 129 WebSocket-Protocol| header in its handshake, and the value |xmpp| 130 MUST be included in the list of protocols. The reply from the server 131 MUST also contain |xmpp| in its own |Sec-WebSocket-Protocol| header 132 in order for an XMPP sub-protocol connection to be established. 134 Once the handshake is complete, WebSocket messages sent or received 135 will conform to the protocol defined in the rest of this document. 137 C: GET /xmpp-websocket HTTP/1.1 138 Host: example.com 139 Upgrade: websocket 140 Connection: Upgrade 141 Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== 142 Origin: http://example.com 143 ... 144 Sec-WebSocket-Protocol: xmpp 145 Sec-WebSocket-Version: 13 147 S: HTTP/1.1 101 Switching Protocols 148 Upgrade: websocket 149 Connection: Upgrade 150 ... 151 Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo= 152 Sec-WebSocket-Protocol: xmpp 154 [WebSocket connection established] 156 C: 160 S: 166 3.2. WebSocket Messages 168 Data frame messages in the XMPP sub-protocol MUST be of the text type 169 and contain UTF-8 encoded data. 171 3.3. XMPP Framing 173 The WebSocket XMPP sub-protocol deviates from the standard method of 174 constructing and using XML streams as defined in [RFC6120] by 175 adopting the message framing provided by WebSocket to delineate the 176 stream open and close headers, stanzas, and other top-level stream 177 elements. 179 3.3.1. Framed XML Stream 181 The start of a framed XML stream is marked by the use of an opening 182 "stream header" which is an element with the appropriate 183 attributes and namespace declarations (see Section 3.3.2). The 184 attributes of the element are the same as those of the 185 element defined defined for the 'http://etherx.jabber.org/ 186 streams' namespace in [RFC6120] and with the same semantics and 187 restrictions. 189 The end of a framed XML stream is denoted by the closing "stream 190 header" which is a element with its associated attributes 191 and namespace declarations (see Section 3.3.2). 193 The introduction of the and elements is motivated by 194 the parsable XML document framing restriction in Section 3.3.3. As a 195 consequence, note that a framed XML stream does not provided a 196 wrapping element encompassing the entirety of the 197 XML stream, as in [RFC6120]. 199 3.3.2. Framed Stream Namespace 201 The XML stream "headers" (the and elements) MUST be 202 qualified by the namespace 'urn:ietf:params:xml:ns:xmpp-framing' (the 203 "framed stream namespace"). If this rule is violated, the entity 204 that receives the offending stream header MUST close the stream with 205 an error, which SHOULD be (see Section 4.9.3.10 206 of [RFC6120]). 208 3.3.3. Stream Frames 210 The individual frames of a framed XML stream have a one-to-one 211 correspondence with WebSocket messages, and MUST be parsable as 212 standalone XML documents, complete with all relevant namespace and 213 language declarations. The inclusion of XML declarations, however, 214 is NOT RECOMMENDED as WebSocket messages are already mandated to be 215 UTF-8 encoded and therefore would only add a constant size overhead 216 to each message. 218 The first character of each frame MUST be a '<' character. 220 Every XMPP stanza or other XML element (including the stream open and 221 close headers) sent directly over the XML stream MUST be sent in its 222 own frame. 224 Examples of WebSocket messages that contain independently parsable 225 XML documents (note that for stream features and errors, there is no 226 parent context element providing the "stream" namespace prefix as in 227 [RFC6120], and thus the stream namespace MUST be declared): 229 -- WS Message boundary -- 230 231 232 233 -- WS Message boundary -- 234 235 236 237 -- WS Message boundary -- 238 239 Every WebSocket message is parsable by itself. 240 242 3.4. Stream Initiation 244 The first message sent after the WebSocket opening handshake MUST be 245 from the initiating entity, and MUST be an element qualified 246 by the "urn:ietf:params:xml:ns:xmpp-framing" namespace and with the 247 same attributes mandated for the opening tag as described in 248 Section 4.7 of [RFC6120]. 250 The receiving entity MUST respond with either an element 251 (whose attributes match those described in Section 4.7 of [RFC6120]) 252 or a element (see Section 3.6.1). 254 An example of a successful stream initiation exchange: 256 C: 260 S: 266 Clients MUST NOT multiplex XMPP streams over the same WebSocket. 268 3.5. Stream Errors 270 Stream level errors in XMPP are terminal. Should such an error 271 occur, the server MUST send the stream error as a complete element in 272 a message to the client. 274 If the error occurs during the opening of a stream, the server MUST 275 send the initial open element response, followed by the stream level 276 error in a second WebSocket message frame. The server MUST then 277 close the connection as specified in Section 3.6. 279 3.6. Closing the Connection 281 Either the server or the client may close the connection at any time. 282 Before closing the connection, the closing party SHOULD close the 283 XMPP stream, if it has been established, by sending a message with 284 the element, qualified by the "urn:ietf:params:xml:ns:xmpp- 285 framing" namespace. The stream is considered closed when a 286 corresponding element is received from the other party. 288 To close the WebSocket connection, the closing party MUST initiate 289 the WebSocket closing handshake (see Section 7.1.2 of [RFC6455]). 291 An example of ending an XMPP over WebSocket session by first closing 292 the XMPP stream layer and then the WebSocket connection layer: 294 Client (XMPP WSS) Server 295 | | | | 296 | | | | 299 | |<------------------------------------------------------------| | 300 | | | | 301 | | (XMPP Stream Closed) | | 302 | +-------------------------------------------------------------+ | 303 | | 304 | WS CLOSE FRAME | 305 |------------------------------------------------------------------>| 306 | WS CLOSE FRAME | 307 |<------------------------------------------------------------------| 308 | | 309 | (Connection Closed) | 310 +-------------------------------------------------------------------+ 312 If a client closes the WebSocket connection without closing the XMPP 313 stream after having enabled stream management (see Section 3.10), the 314 server SHOULD keep the XMPP session alive for a period of time based 315 on server policy, as specified in [XEP-0198]. If the client has not 316 negotiated the use of [XEP-0198], there is no distinction between a 317 stream that was closed as described above and a simple disconnection; 318 the stream is then considered implicitly closed and the XMPP session 319 ended. 321 3.6.1. see-other-uri 323 If the server (or a connection manager intermediary) wishes to 324 instruct the client to move to a different WebSocket endpoint (e.g. 325 for load balancing purposes), the server MAY send a element 326 and set the "see-other-uri" attribute to the URI of the new 327 connection endpoint (which MAY be for a different transport method, 328 such as BOSH (see [XEP-0124] and [XEP-0206]). 330 Clients MUST NOT accept suggested endpoints with a lower security 331 context (e.g. moving from a "wss://" endpoint to a "ws://" or "http:/ 332 /" endpoint). 334 An example of the server closing a stream and instructing the client 335 to connect at a different WebSocket endpoint: 337 S: 340 3.7. Stream Restarts 342 Whenever a stream restart is mandated, both the server and client 343 streams are implicitly closed and new streams MUST be opened, using 344 the same process as in Section 3.4. The client MUST send a new 345 stream element and MUST NOT send a closing element. 347 An example of restarting the stream after successful SASL 348 negotiation: 350 S: 352 [Streams implicitly closed] 354 C: 358 3.8. Pings and Keepalives 360 XMPP servers often send "whitespace keepalives" (see Section 4.6.1 of 361 [RFC6120]) between stanzas to maintain an XML stream, and XMPP 362 clients can do the same as these extra whitespace characters are not 363 significant in the protocol. Servers and clients SHOULD use 364 WebSocket ping control frames instead for this purpose. 366 In some cases, the WebSocket connection might be served by an 367 intermediary connection manager and not the XMPP server. In these 368 situations, the use of WebSocket ping messages are insufficient to 369 test that the XMPP stream is still alive. Both the XMPP Ping 370 extension [XEP-0199] and the XMPP Stream Management extension 371 [XEP-0198] provide mechanisms to ping the XMPP server, and either 372 extension (or both) MAY be used to determine the state of the 373 connection. 375 3.9. Use of TLS 377 TLS cannot be used at the XMPP sub-protocol layer because the sub- 378 protocol does not allow for raw binary data to be sent. Instead, 379 enabling TLS SHOULD be done at the WebSocket layer using secure 380 WebSocket connections via the |wss| URI scheme. (See Section 10.6 of 381 [RFC6455].) 383 Because TLS is to be provided outside of the XMPP sub-protocol layer, 384 a server MUST NOT advertise TLS as a stream feature (see Section 4.6 385 of [RFC6120]), and a client MUST ignore any advertised TLS stream 386 feature, when using the XMPP sub-protocol. 388 3.10. Stream Management 390 In order to alleviate the problems of temporary disconnections, the 391 XMPP Stream Management extension [XEP-0198] MAY be used to confirm 392 when stanzas have been received by the server. 394 In particular, the use of session resumption in [XEP-0198] MAY be 395 used to allow for recreating the same stream session state after a 396 temporary network unavailability or after navigating to a new URL in 397 a browser. 399 4. Discovering the WebSocket Connection Method 401 Section 3 of [RFC6120] defines a procedure for connecting to an XMPP 402 server, including ways to discover the TCP/IP address and port of the 403 server. When using the WebSocket binding as specified in this 404 document (instead of the TCP binding as specified in [RFC6120]), a 405 client needs an alternative way to discover information about the 406 server's connection methods, since web browsers and other WebSocket- 407 capable software applications typically cannot obtain such 408 information from the Domain Name System. 410 The alternative lookup process uses Web Host Metadata [RFC6415] and 411 Web Linking [RFC5988], where the link relation type is "urn:xmpp:alt- 412 connections:websocket" as described in Discovering Alternate XMPP 413 Connection Methods [XEP-0156]. An example follows. 415 416 418 420 Servers MAY expose discovery information using host-meta documents, 421 and clients MAY use such information to determine the WebSocket 422 endpoint for a server. 424 Use of web-host metadata MAY be used to establish trust between the 425 XMPP server domain and the WebSocket endpoint, particularly in multi- 426 tenant situations where the same WebSocket endpoint is serving 427 multiple XMPP domains. 429 5. IANA Considerations 431 5.1. WebSocket Subprotocol Name 433 This specification requests IANA to register the WebSocket XMPP sub- 434 protocol under the "WebSocket Subprotocol Name" Registry with the 435 following data: 437 Subprotocol Identifier: xmpp 439 Subprotocol Common Name: WebSocket Transport for the Extensible 440 Messaging and Presence Protocol (XMPP) 442 Subprotocol Definition: this document 444 5.2. URN Sub-Namespace 446 A URN sub-namespace for framing of Extensible Messaging and Presence 447 Protocol (XMPP) streams is defined as follows. 449 URI: urn:ietf:params:xml:ns:xmpp-framing 451 Specification: this document 453 Description: This is the XML namespace name for framing of 454 Extensible Messaging and Presence Protocol (XMPP) streams as 455 defined by RFC XXXX. 457 Registrant Contact: IESG 459 6. Security Considerations 461 Since application level TLS cannot be used (see Section 3.9), 462 applications need to protect the privacy of XMPP traffic at the 463 WebSocket or other appropriate layer. 465 Browser based applications are not able to inspect and verify at the 466 application layer the certificate used for the WebSocket connection 467 to ensure that it corresponds to the domain specified as the "to" 468 address of the XMPP stream. For hosts whose domain matches the 469 origin for the WebSocket connection, that check is already performed 470 by the browser. However, in situations where the domain of the XMPP 471 server might not match the origin for the WebSocket endpoint 472 (especially multi-tenant hosting situations), the web host metadata 473 method (see [RFC6415] and [XEP-0156]) MAY be used to delegate trust 474 from the XMPP server domain to the WebSocket origin. 476 When presented with a new WebSocket endpoint via the "see-other-uri" 477 attribute of a element, clients MUST NOT accept the 478 suggestion if the security context of the new endpoint is lower than 479 the current one in order to prevent downgrade attacks from a "wss://" 480 endpoint to "ws://". 482 The Security Considerations for both WebSocket (see Section 10 of 483 [RFC6455] and XMPP (see Section 13 of [RFC6120]) apply to the 484 WebSocket XMPP sub-protocol. 486 7. References 488 7.1. Normative References 490 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 491 Requirement Levels", BCP 14, RFC 2119, March 1997. 493 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 494 Protocol (XMPP): Core", RFC 6120, March 2011. 496 [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 497 6455, December 2011. 499 7.2. Informative References 501 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 503 [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence 504 Protocol (XMPP): Instant Messaging and Presence", RFC 505 6121, March 2011. 507 [RFC6202] Loreto, S., Saint-Andre, P., Salsano, S., and G. Wilkins, 508 "Known Issues and Best Practices for the Use of Long 509 Polling and Streaming in Bidirectional HTTP", RFC 6202, 510 April 2011. 512 [RFC6415] Hammer-Lahav, E. and B. Cook, "Web Host Metadata", RFC 513 6415, October 2011. 515 [XEP-0124] 516 Paterson, I., Smith, D., Saint-Andre, P., Moffitt, J., and 517 L. Stout, "Bidirectional-streams Over Synchronous HTTP 518 (BOSH)", XSF XEP 0124, November 2013. 520 [XEP-0156] 521 Hildebrand, J., Saint-Andre, P., and L. Stout, 522 "Discovering Alternative XMPP Connection Methods", XSF XEP 523 0156, January 2014. 525 [XEP-0198] 526 Karneges, J., Saint-Andre, P., Hildebrand, J., Forno, F., 527 Cridland, D., and M. Wild, "Stream Management", XSF XEP 528 0198, June 2011. 530 [XEP-0199] 531 Saint-Andre, P., "XMPP Ping", XSF XEP 0199, June 2009. 533 [XEP-0206] 534 Paterson, I., Saint-Andre, P., and L. Stout, "XMPP Over 535 BOSH", XSF XEP 0206, November 2013. 537 [XML-SCHEMA] 538 Thompson, H., Maloney, M., Mendelsohn, N., and D. Beech, 539 "XML Schema Part 1: Structures Second Edition", World Wide 540 Web Consortium Recommendation REC-xmlschema-1-20041028, 541 October 2004, 542 . 544 Appendix A. XML Schema 546 The following schema formally defines the 'urn:ietf:params:xml:ns 547 :xmpp-framing' namespace used in this document, in conformance with 548 W3C XML Schema [XML-SCHEMA]. Because validation of XML streams and 549 stanzas is optional, this schema is not normative and is provided for 550 descriptive purposes only. 552 554 560 561 562 563 564 566 568 570 572 574 575 576 577 579 580 581 582 583 585 587 589 591 593 595 596 597 598 600 601 602 604 605 607 609 Authors' Addresses 611 Lance Stout (editor) 612 &yet 614 Email: lance@andyet.net 616 Jack Moffitt 617 Mozilla 619 Email: jack@metajack.im 621 Eric Cestari 622 cstar industries 624 Email: eric@cstar.io