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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 AVTCORE M. Petit-Huguenin 3 Internet-Draft Impedance Mismatch 4 Updates: 5764 (if approved) G. Salgueiro 5 Intended status: Standards Track Cisco Systems 6 Expires: July 29, 2016 January 26, 2016 8 Multiplexing Scheme Updates for Secure Real-time Transport Protocol 9 (SRTP) Extension for Datagram Transport Layer Security (DTLS) 10 draft-ietf-avtcore-rfc5764-mux-fixes-04 12 Abstract 14 This document defines how Datagram Transport Layer Security (DTLS), 15 Real-time Transport Protocol (RTP), Real-time Transport Control 16 Protocol (RTCP), Session Traversal Utilities for NAT (STUN), and 17 Traversal Using Relays around NAT (TURN) packets are multiplexed on a 18 single receiving socket. It overrides the guidance from SRTP 19 Extension for DTLS [RFC5764], which suffered from three issues 20 described and fixed in this document. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 29, 2016. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Implicit Allocation of Codepoints for New STUN Methods . . . 3 58 3. Implicit Allocation of New Codepoints for TLS ContentTypes . 4 59 4. Multiplexing of TURN Channels . . . . . . . . . . . . . . . . 5 60 5. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 6. RFC 5764 Updates . . . . . . . . . . . . . . . . . . . . . . 6 62 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7 63 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 64 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 65 9.1. STUN Methods . . . . . . . . . . . . . . . . . . . . . . 8 66 9.2. TLS ContentType . . . . . . . . . . . . . . . . . . . . . 9 67 9.3. TURN Channel Numbers . . . . . . . . . . . . . . . . . . 9 68 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 69 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 70 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 71 11.2. Informative References . . . . . . . . . . . . . . . . . 11 72 Appendix A. Release notes . . . . . . . . . . . . . . . . . . . 11 73 A.1. Modifications between draft-ietf-avtcore-rfc5764-mux- 74 fixes-04 and draft-ietf-avtcore-rfc5764-mux-fixes-03 . . 11 75 A.2. Modifications between draft-ietf-avtcore-rfc5764-mux- 76 fixes-03 and draft-ietf-avtcore-rfc5764-mux-fixes-02 . . 12 77 A.3. Modifications between draft-ietf-avtcore-rfc5764-mux- 78 fixes-02 and draft-ietf-avtcore-rfc5764-mux-fixes-01 . . 12 79 A.4. Modifications between draft-ietf-avtcore-rfc5764-mux- 80 fixes-01 and draft-ietf-avtcore-rfc5764-mux-fixes-00 . . 12 81 A.5. Modifications between draft-ietf-avtcore-rfc5764-mux- 82 fixes-00 and draft-petithuguenin-avtcore-rfc5764-mux- 83 fixes-02 . . . . . . . . . . . . . . . . . . . . . . . . 12 84 A.6. Modifications between draft-petithuguenin-avtcore-rfc5764 85 -mux-fixes-00 and draft-petithuguenin-avtcore-rfc5764 86 -mux-fixes-01 . . . . . . . . . . . . . . . . . . . . . . 13 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 89 1. Introduction 91 Section 5.1.2 of Secure Real-time Transport Protocol (SRTP) Extension 92 for DTLS [RFC5764] defines a scheme for a Real-time Transport 93 Protocol (RTP) [RFC3550] receiver to demultiplex Datagram Transport 94 Layer Security (DTLS) [RFC6347], Session Traversal Utilities for NAT 95 (STUN) [RFC5389] and Secure Real-time Transport Protocol 96 (SRTP)/Secure Real-time Transport Control Protocol (SRTCP) [RFC3711] 97 packets that are arriving on the RTP port. Unfortunately, this 98 demultiplexing scheme has created problematic issues: 100 1. It implicitly allocated codepoints for new STUN methods without 101 an IANA registry reflecting these new allocations. 103 2. It implicitly allocated codepoints for new Transport Layer 104 Security (TLS) ContentTypes without an IANA registry reflecting 105 these new allocations. 107 3. It did not take into account the fact that the Traversal Using 108 Relays around NAT (TURN) usage of STUN can create TURN channels 109 that also need to be demultiplexed with the other packet types 110 explicitly mentioned in Section 5.1.2 of RFC 5764. 112 Having overlapping ranges between different IANA registries becomes 113 an issue when a new codepoint is allocated in one of these registries 114 without carefully anyalyzing the impact it could have on the other 115 registries when that codepoint is demultiplexed. Even if a codepoint 116 is not initially thought to be useful in an RFC 5764 implementation, 117 the respective IANA registry expert should at least raise a flag when 118 the allocated codepoint irrevocably prevents multiplexing. 120 The first goal of this document is to make sure that future 121 allocations in any of the affected protocols are done with the full 122 knowledge of their impact on multiplexing. This is achieved by 123 modifying the IANA registries with instructions for coordination 124 between the protocols at risk. 126 A second goal is to permit the addition of new protocols to the list 127 of existing multiplexed protocols in a manner that does not break 128 existing implementations. 130 The flaws in the demultiplexing scheme were unavoidably inherited by 131 other documents, such as [RFC7345] and 132 [I-D.ietf-mmusic-sdp-bundle-negotiation]. So in addition, these and 133 any other affected documents will need to be corrected with the 134 updates this document provides. 136 2. Implicit Allocation of Codepoints for New STUN Methods 138 The demultiplexing scheme in [RFC5764] states that the receiver can 139 identify the packet type by looking at the first byte. If the value 140 of this first byte is 0 or 1, the packet is identified to be STUN. 141 The problem that arises as a result of this implicit allocation is 142 that this restricts the codepoints for STUN methods (as described in 143 Section 18.1 of [RFC5389]) to values between 0x000 and 0x07F, which 144 in turn reduces the number of possible STUN method codepoints 145 assigned by IETF Review (i.e., the range from (0x000 - 0x7FF) from 146 2048 to only 128 and eliminating the possibility of having STUN 147 method codepoints assigned by Designated Expert (i.e., the range 148 0x800 - 0xFFF). 150 To preserve the Designated Expert range, this document allocates the 151 value 2 and 3 to also identify STUN methods. 153 The IANA Registry for STUN methods is modified to mark the codepoints 154 from 0x100 to 0xFFF as Reserved. These codepoints can still be 155 allocated, but require IETF Review with a document that will properly 156 evaluate the risk of an assignment overlapping with other registries. 158 In addition, this document also updates the IANA registry such that 159 the STUN method codepoints assigned in the 0x080-0x0FF range are also 160 assigned via Designated Expert. The proposed changes to the STUN 161 Method Registry are: 163 OLD: 165 0x000-0x7FF IETF Review 166 0x800-0xFFF Designated Expert 168 NEW: 170 0x000-0x07F IETF Review 171 0x080-0x0FF Designated Expert 172 0x100-0xFFF Reserved 174 3. Implicit Allocation of New Codepoints for TLS ContentTypes 176 The demultiplexing scheme in [RFC5764] dictates that if the value of 177 the first byte is between 20 and 63 (inclusive), then the packet is 178 identified to be DTLS. The problem that arises is that this 179 restricts the TLS ContentType codepoints (as defined in Section 12 of 180 [RFC5246]) to this range, and by extension implicitly allocates 181 ContentType codepoints 0 to 19 and 64 to 255. With respect to TLS 182 packet identification, this document simply explicitly reserves the 183 codepoints from 0 to 19 and from 64 to 255. These codepoints can 184 still be allocated, but require Standards Action with a document that 185 will properly evaluate the risk of an assignment overlapping with 186 other registries. The proposed changes to the TLS ContentTypes 187 Registry are: 189 OLD: 191 0-19 Unassigned 192 20 change_cipher_spec 193 21 alert 194 22 handshake 195 23 application_data 196 24 heartbeat 197 25-255 Unassigned 199 NEW: 201 0-19 Reserved (Requires coordination, see RFCXXXX) 202 20 change_cipher_spec 203 21 alert 204 22 handshake 205 23 application_data 206 24 heartbeat 207 25-63 Unassigned 208 64-255 Reserved (Requires coordination, see RFCXXXX) 210 4. Multiplexing of TURN Channels 212 When used with ICE [RFC5245], an RFC 5764 implementation can receive 213 packets on the same socket from three different paths, as shown in 214 Figure 1: 216 1. Directly from the source 218 2. Through a NAT 220 3. Relayed by a TURN server 222 +------+ 223 | TURN |<------------------------+ 224 +------+ | 225 | | 226 | +-------------------------+ | 227 | | | | 228 v v | | 229 NAT ----------- | | 230 | | +---------------------+ | | 231 | | | | | | 232 v v v | | | 233 +----------+ +----------+ 234 | RFC 5764 | | RFC 5764 | 235 +----------+ +----------+ 237 Figure 1: Packet Reception by an RFC 5764 Implementation 239 Even if the ICE algorithm succeeded in selecting a non-relayed path, 240 it is still possible to receive data from the TURN server. For 241 instance, when ICE is used with aggressive nomination the media path 242 can quickly change until it stabilizes. Also, freeing ICE candidates 243 is optional, so the TURN server can restart forwarding STUN 244 connectivity checks during an ICE restart. 246 TURN channels are an optimization where data packets are exchanged 247 with a 4-byte prefix, instead of the standard 36-byte STUN overhead 248 (see Section 2.5 of [RFC5766]). The problem is that the RFC 5764 249 demultiplexing scheme does not define what to do with packets 250 received over a TURN channel since these packets will start with a 251 first byte whose value will be between 64 and 127 (inclusive). If 252 the TURN server was instructed to send data over a TURN channel, then 253 the current RFC 5764 demultiplexing scheme will reject these packets. 254 Current implementations violate RFC 5764 for values 64 to 127 255 (inclusive) and they instead parse packets with such values as TURN. 257 In order to prevent future documents from assigning values from the 258 unused range to a new protocol, this document modifies the RFC 5764 259 demultiplexing algorithm to properly account for TURN channels by 260 allocating the values from 64 to 79 for this purpose. 262 5. Terminology 264 The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL" 265 in this document are to be interpreted as described in [RFC2119] when 266 they appear in ALL CAPS. When these words are not in ALL CAPS (such 267 as "must" or "Must"), they have their usual English meanings, and are 268 not to be interpreted as RFC 2119 key words. 270 6. RFC 5764 Updates 272 This document updates the text in Section 5.1.2 of [RFC5764] as 273 follows: 275 OLD TEXT 277 The process for demultiplexing a packet is as follows. The receiver 278 looks at the first byte of the packet. If the value of this byte is 279 0 or 1, then the packet is STUN. If the value is in between 128 and 280 191 (inclusive), then the packet is RTP (or RTCP, if both RTCP and 281 RTP are being multiplexed over the same destination port). If the 282 value is between 20 and 63 (inclusive), the packet is DTLS. This 283 process is summarized in Figure 3. 285 +----------------+ 286 | 127 < B < 192 -+--> forward to RTP 287 | | 288 packet --> | 19 < B < 64 -+--> forward to DTLS 289 | | 290 | B < 2 -+--> forward to STUN 291 +----------------+ 293 Figure 3: The DTLS-SRTP receiver's packet demultiplexing algorithm. 294 Here the field B denotes the leading byte of the packet. 296 END OLD TEXT 298 NEW TEXT 300 The process for demultiplexing a packet is as follows. The receiver 301 looks at the first byte of the packet. If the value of this byte is 302 in between 0 and 3 (inclusive), then the packet is STUN. Then if the 303 value is between 20 and 63 (inclusive), the packet is DTLS. Then if 304 the value is between 64 and 79 (inclusive), the packet is TURN 305 Channel. Then if the value is in between 128 and 191 (inclusive), 306 then the packet is RTP (or RTCP, if both RTCP and RTP are being 307 multiplexed over the same destination port). Else if the value does 308 not match any known range then the packet MUST be dropped and an 309 alert MAY be logged. This process is summarized in Figure 3. 311 +----------------+ 312 | [0..3] -+--> forward to STUN 313 | | 314 packet --> | [20..63] -+--> forward to DTLS 315 | | 316 | [64..79] -+--> forward to TURN Channel 317 | | 318 | [128..191] -+--> forward to RTP 319 +----------------+ 321 Figure 3: The DTLS-SRTP receiver's packet demultiplexing algorithm. 323 END NEW TEXT 325 7. Implementation Status 327 [[Note to RFC Editor: Please remove this section and the reference to 328 [RFC6982] before publication.]] 330 This section records the status of known implementations of the 331 protocol defined by this specification at the time of posting of this 332 Internet-Draft, and is based on a proposal described in [RFC6982]. 334 The description of implementations in this section is intended to 335 assist the IETF in its decision processes in progressing drafts to 336 RFCs. Please note that the listing of any individual implementation 337 here does not imply endorsement by the IETF. Furthermore, no effort 338 has been spent to verify the information presented here that was 339 supplied by IETF contributors. This is not intended as, and must not 340 be construed to be, a catalog of available implementations or their 341 features. Readers are advised to note that other implementations may 342 exist. 344 According to [RFC6982], "this will allow reviewers and working groups 345 to assign due consideration to documents that have the benefit of 346 running code, which may serve as evidence of valuable experimentation 347 and feedback that have made the implemented protocols more mature. 348 It is up to the individual working groups to use this information as 349 they see fit". 351 Note that there is currently no implementation declared in this 352 section, but the intent is to add RFC 6982 templates here from 353 implementers that support the modifications in this document. 355 8. Security Considerations 357 This document updates existing IANA registries, adds a new range for 358 TURN channels in the demuxing algorithm, and madates an ascending 359 order for testing the ranges in the demuxing algorithm. 361 These modifications do not introduce any specific security 362 considerations beyond those detailed in [RFC5764]. 364 9. IANA Considerations 366 9.1. STUN Methods 368 This specification contains the registration information for reserved 369 STUN Methods codepoints, as explained in Section 2 and in accordance 370 with the procedures defined in Section 18.1 of [RFC5389]. 372 Value: 0x100-0xFFF 374 Name: Reserved (MUST be allocated with IETF Review. For DTLS-SRTP 375 multiplexing collision avoidance see RFC XXXX) 377 Reference: RFC5764, RFCXXXX 379 This specification also reassigns the ranges in the STUN Methods 380 Registry as follow: 382 Range: 0x000-0x07F 384 Registration Procedures: IETF Review 386 Range: 0x080-0x0FF 388 Registration Procedures: Designated Expert 390 9.2. TLS ContentType 392 This specification contains the registration information for reserved 393 TLS ContentType codepoints, as explained in Section 3 and in 394 accordance with the procedures defined in Section 12 of [RFC5246]. 396 Value: 0-19 398 Description: Reserved (MUST be allocated with Standards Action. 399 For DTLS-SRTP multiplexing collision avoidance see RFC XXXX) 401 DTLS-OK: N/A 403 Reference: RFC5764, RFCXXXX 405 Value: 64-255 407 Description: Reserved (MUST be allocated with Standards Action. 408 For DTLS-SRTP multiplexing collision avoidance see RFC XXXX) 410 DTLS-OK: N/A 412 Reference: RFC5764, RFCXXXX 414 9.3. TURN Channel Numbers 416 This specification contains the registration information for reserved 417 TURN Channel Numbers codepoints, as explained in Section 4 and in 418 accordance with the procedures defined in Section 18 of [RFC5766]. 420 Value: 0x5000-0xFFFF 422 Name: Reserved (For DTLS-SRTP multiplexing collision avoidance see 423 RFC XXXX) 425 Reference: RFCXXXX 427 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 428 document.] 430 10. Acknowledgements 432 The implicit STUN Method codepoint allocations problem was first 433 reported by Martin Thomson in the RTCWEB mailing-list and discussed 434 further with Magnus Westerlund. 436 Thanks to Simon Perreault, Colton Shields, Cullen Jennings, Colin 437 Perkins, Magnus Westerlund, Paul Jones, Jonathan Lennox, Varun Singh 438 and Justin Uberti for the comments, suggestions, and questions that 439 helped improve this document. 441 11. References 443 11.1. Normative References 445 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 446 Requirement Levels", BCP 14, RFC 2119, 447 DOI 10.17487/RFC2119, March 1997, 448 . 450 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 451 Jacobson, "RTP: A Transport Protocol for Real-Time 452 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 453 July 2003, . 455 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 456 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 457 RFC 3711, DOI 10.17487/RFC3711, March 2004, 458 . 460 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 461 (ICE): A Protocol for Network Address Translator (NAT) 462 Traversal for Offer/Answer Protocols", RFC 5245, 463 DOI 10.17487/RFC5245, April 2010, 464 . 466 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 467 (TLS) Protocol Version 1.2", RFC 5246, 468 DOI 10.17487/RFC5246, August 2008, 469 . 471 [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 472 "Session Traversal Utilities for NAT (STUN)", RFC 5389, 473 DOI 10.17487/RFC5389, October 2008, 474 . 476 [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer 477 Security (DTLS) Extension to Establish Keys for the Secure 478 Real-time Transport Protocol (SRTP)", RFC 5764, 479 DOI 10.17487/RFC5764, May 2010, 480 . 482 [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using 483 Relays around NAT (TURN): Relay Extensions to Session 484 Traversal Utilities for NAT (STUN)", RFC 5766, 485 DOI 10.17487/RFC5766, April 2010, 486 . 488 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 489 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 490 January 2012, . 492 11.2. Informative References 494 [RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 495 Code: The Implementation Status Section", RFC 6982, 496 DOI 10.17487/RFC6982, July 2013, 497 . 499 [RFC7345] Holmberg, C., Sedlacek, I., and G. Salgueiro, "UDP 500 Transport Layer (UDPTL) over Datagram Transport Layer 501 Security (DTLS)", RFC 7345, DOI 10.17487/RFC7345, August 502 2014, . 504 [I-D.ietf-mmusic-sdp-bundle-negotiation] 505 Holmberg, C., Alvestrand, H., and C. Jennings, 506 "Negotiating Media Multiplexing Using the Session 507 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 508 negotiation-23 (work in progress), July 2015. 510 Appendix A. Release notes 512 This section must be removed before publication as an RFC. 514 A.1. Modifications between draft-ietf-avtcore-rfc5764-mux-fixes-04 and 515 draft-ietf-avtcore-rfc5764-mux-fixes-03 517 o Removed Section on "Demultiplexing Algorithm Test Order" 519 o Split the Introduction into separate sections 521 A.2. Modifications between draft-ietf-avtcore-rfc5764-mux-fixes-03 and 522 draft-ietf-avtcore-rfc5764-mux-fixes-02 524 o Revert to the RFC 5389, as the stunbis reference was needed only 525 for STUN over SCTP. 527 A.3. Modifications between draft-ietf-avtcore-rfc5764-mux-fixes-02 and 528 draft-ietf-avtcore-rfc5764-mux-fixes-01 530 o Remove any discussion about SCTP until a consensus emerges in 531 TRAM. 533 A.4. Modifications between draft-ietf-avtcore-rfc5764-mux-fixes-01 and 534 draft-ietf-avtcore-rfc5764-mux-fixes-00 536 o Instead of allocating the values that are common on each registry, 537 the specification now only reserves them, giving the possibility 538 to allocate them in case muxing is irrelevant. 540 o STUN range is now 0-3m with 2-3 being Designated Expert. 542 o TLS ContentType 0-19 and 64-255 are now reserved. 544 o Add SCTP over UDP value. 546 o If an implementation uses the source IP address/port to separate 547 TURN channels packets then the whole channel numbers are 548 available. 550 o If not the prefix is between 64 and 79. 552 o First byte test order is now by incremental values, so failure is 553 deterministic. 555 o Redraw the demuxing diagram. 557 A.5. Modifications between draft-ietf-avtcore-rfc5764-mux-fixes-00 and 558 draft-petithuguenin-avtcore-rfc5764-mux-fixes-02 560 o Adoption by WG. 562 o Add reference to STUNbis. 564 A.6. Modifications between draft-petithuguenin-avtcore-rfc5764-mux- 565 fixes-00 and draft-petithuguenin-avtcore-rfc5764-mux-fixes-01 567 o Change affiliation. 569 Authors' Addresses 571 Marc Petit-Huguenin 572 Impedance Mismatch 574 Email: marc@petit-huguenin.org 576 Gonzalo Salgueiro 577 Cisco Systems 578 7200-12 Kit Creek Road 579 Research Triangle Park, NC 27709 580 US 582 Email: gsalguei@cisco.com