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'FIPS186' == Outdated reference: A later version (-07) exists of draft-ietf-mmusic-sdp-uks-02 == Outdated reference: A later version (-12) exists of draft-ietf-rtcweb-security-10 ** Obsolete normative reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) ** Obsolete normative reference: RFC 5245 (Obsoleted by RFC 8445, RFC 8839) ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) ** Obsolete normative reference: RFC 5785 (Obsoleted by RFC 8615) ** Obsolete normative reference: RFC 6347 (Obsoleted by RFC 9147) == Outdated reference: A later version (-26) exists of draft-ietf-rtcweb-jsep-24 Summary: 6 errors (**), 0 flaws (~~), 6 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 RTCWEB E. Rescorla 3 Internet-Draft RTFM, Inc. 4 Intended status: Standards Track October 22, 2018 5 Expires: April 25, 2019 7 WebRTC Security Architecture 8 draft-ietf-rtcweb-security-arch-16 10 Abstract 12 This document defines the security architecture for WebRTC, a 13 protocol suite intended for use with real-time applications that can 14 be deployed in browsers - "real time communication on the Web". 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at https://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on April 25, 2019. 33 Copyright Notice 35 Copyright (c) 2018 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (https://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 This document may contain material from IETF Documents or IETF 49 Contributions published or made publicly available before November 50 10, 2008. The person(s) controlling the copyright in some of this 51 material may not have granted the IETF Trust the right to allow 52 modifications of such material outside the IETF Standards Process. 53 Without obtaining an adequate license from the person(s) controlling 54 the copyright in such materials, this document may not be modified 55 outside the IETF Standards Process, and derivative works of it may 56 not be created outside the IETF Standards Process, except to format 57 it for publication as an RFC or to translate it into languages other 58 than English. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 3. Trust Model . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 3.1. Authenticated Entities . . . . . . . . . . . . . . . . . 5 66 3.2. Unauthenticated Entities . . . . . . . . . . . . . . . . 6 67 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 68 4.1. Initial Signaling . . . . . . . . . . . . . . . . . . . . 8 69 4.2. Media Consent Verification . . . . . . . . . . . . . . . 10 70 4.3. DTLS Handshake . . . . . . . . . . . . . . . . . . . . . 11 71 4.4. Communications and Consent Freshness . . . . . . . . . . 11 72 5. SDP Identity Attribute . . . . . . . . . . . . . . . . . . . 12 73 5.1. Offer/Answer Considerations . . . . . . . . . . . . . . . 13 74 5.1.1. Generating the Initial SDP Offer . . . . . . . . . . 13 75 5.1.2. Answerer Processing of SDP Offer . . . . . . . . . . 14 76 5.1.3. Generating of SDP Answer . . . . . . . . . . . . . . 14 77 5.1.4. Offerer Processing of SDP Answer . . . . . . . . . . 14 78 5.1.5. Modifying the Session . . . . . . . . . . . . . . . . 14 79 6. Detailed Technical Description . . . . . . . . . . . . . . . 14 80 6.1. Origin and Web Security Issues . . . . . . . . . . . . . 14 81 6.2. Device Permissions Model . . . . . . . . . . . . . . . . 15 82 6.3. Communications Consent . . . . . . . . . . . . . . . . . 17 83 6.4. IP Location Privacy . . . . . . . . . . . . . . . . . . . 17 84 6.5. Communications Security . . . . . . . . . . . . . . . . . 18 85 7. Web-Based Peer Authentication . . . . . . . . . . . . . . . . 20 86 7.1. Trust Relationships: IdPs, APs, and RPs . . . . . . . . . 21 87 7.2. Overview of Operation . . . . . . . . . . . . . . . . . . 22 88 7.3. Items for Standardization . . . . . . . . . . . . . . . . 24 89 7.4. Binding Identity Assertions to JSEP Offer/Answer 90 Transactions . . . . . . . . . . . . . . . . . . . . . . 24 91 7.4.1. Carrying Identity Assertions . . . . . . . . . . . . 25 92 7.5. Determining the IdP URI . . . . . . . . . . . . . . . . . 26 93 7.5.1. Authenticating Party . . . . . . . . . . . . . . . . 27 94 7.5.2. Relying Party . . . . . . . . . . . . . . . . . . . . 27 95 7.6. Requesting Assertions . . . . . . . . . . . . . . . . . . 27 96 7.7. Managing User Login . . . . . . . . . . . . . . . . . . . 28 97 8. Verifying Assertions . . . . . . . . . . . . . . . . . . . . 29 98 8.1. Identity Formats . . . . . . . . . . . . . . . . . . . . 29 99 9. Security Considerations . . . . . . . . . . . . . . . . . . . 30 100 9.1. Communications Security . . . . . . . . . . . . . . . . . 30 101 9.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 31 102 9.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 32 103 9.4. IdP Authentication Mechanism . . . . . . . . . . . . . . 33 104 9.4.1. PeerConnection Origin Check . . . . . . . . . . . . . 33 105 9.4.2. IdP Well-known URI . . . . . . . . . . . . . . . . . 34 106 9.4.3. Privacy of IdP-generated identities and the hosting 107 site . . . . . . . . . . . . . . . . . . . . . . . . 34 108 9.4.4. Security of Third-Party IdPs . . . . . . . . . . . . 34 109 9.4.4.1. Confusable Characters . . . . . . . . . . . . . . 34 110 9.4.5. Web Security Feature Interactions . . . . . . . . . . 35 111 9.4.5.1. Popup Blocking . . . . . . . . . . . . . . . . . 35 112 9.4.5.2. Third Party Cookies . . . . . . . . . . . . . . . 35 113 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35 114 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36 115 12. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 116 12.1. Changes since -15 . . . . . . . . . . . . . . . . . . . 36 117 12.2. Changes since -11 . . . . . . . . . . . . . . . . . . . 36 118 12.3. Changes since -10 . . . . . . . . . . . . . . . . . . . 36 119 12.4. Changes since -06 . . . . . . . . . . . . . . . . . . . 37 120 12.5. Changes since -05 . . . . . . . . . . . . . . . . . . . 37 121 12.6. Changes since -03 . . . . . . . . . . . . . . . . . . . 37 122 12.7. Changes since -03 . . . . . . . . . . . . . . . . . . . 37 123 12.8. Changes since -02 . . . . . . . . . . . . . . . . . . . 37 124 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 125 13.1. Normative References . . . . . . . . . . . . . . . . . . 38 126 13.2. Informative References . . . . . . . . . . . . . . . . . 41 127 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 42 129 1. Introduction 131 The Real-Time Communications on the Web (WebRTC) working group is 132 tasked with standardizing protocols for real-time communications 133 between Web browsers. The major use cases for WebRTC technology are 134 real-time audio and/or video calls, Web conferencing, and direct data 135 transfer. Unlike most conventional real-time systems, (e.g., SIP- 136 based [RFC3261] soft phones) WebRTC communications are directly 137 controlled by some Web server, via a JavaScript (JS) API as shown in 138 Figure 1. 140 +----------------+ 141 | | 142 | Web Server | 143 | | 144 +----------------+ 145 ^ ^ 146 / \ 147 HTTP / \ HTTP 148 / \ 149 / \ 150 v v 151 JS API JS API 152 +-----------+ +-----------+ 153 | | Media | | 154 | Browser |<---------->| Browser | 155 | | | | 156 +-----------+ +-----------+ 158 Figure 1: A simple WebRTC system 160 A more complicated system might allow for interdomain calling, as 161 shown in Figure 2. The protocol to be used between the domains is 162 not standardized by WebRTC, but given the installed base and the form 163 of the WebRTC API is likely to be something SDP-based like SIP. 165 +--------------+ +--------------+ 166 | | SIP,XMPP,...| | 167 | Web Server |<----------->| Web Server | 168 | | | | 169 +--------------+ +--------------+ 170 ^ ^ 171 | | 172 HTTP | | HTTP 173 | | 174 v v 175 JS API JS API 176 +-----------+ +-----------+ 177 | | Media | | 178 | Browser |<---------------->| Browser | 179 | | | | 180 +-----------+ +-----------+ 182 Figure 2: A multidomain WebRTC system 184 This system presents a number of new security challenges, which are 185 analyzed in [I-D.ietf-rtcweb-security]. This document describes a 186 security architecture for WebRTC which addresses the threats and 187 requirements described in that document. 189 2. Terminology 191 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 192 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 193 "OPTIONAL" in this document are to be interpreted as described in BCP 194 14 [RFC2119] [RFC8174] when, and only when, they appear in all 195 capitals, as shown here. 197 3. Trust Model 199 The basic assumption of this architecture is that network resources 200 exist in a hierarchy of trust, rooted in the browser, which serves as 201 the user's Trusted Computing Base (TCB). Any security property which 202 the user wishes to have enforced must be ultimately guaranteed by the 203 browser (or transitively by some property the browser verifies). 204 Conversely, if the browser is compromised, then no security 205 guarantees are possible. Note that there are cases (e.g., Internet 206 kiosks) where the user can't really trust the browser that much. In 207 these cases, the level of security provided is limited by how much 208 they trust the browser. 210 Optimally, we would not rely on trust in any entities other than the 211 browser. However, this is unfortunately not possible if we wish to 212 have a functional system. Other network elements fall into two 213 categories: those which can be authenticated by the browser and thus 214 can be granted permissions to access sensitive resources, and those 215 which cannot be authenticated and thus are untrusted. 217 3.1. Authenticated Entities 219 There are two major classes of authenticated entities in the system: 221 o Calling services: Web sites whose origin we can verify (optimally 222 via HTTPS, but in some cases because we are on a topologically 223 restricted network, such as behind a firewall, and can infer 224 authentication from firewall behavior). 226 o Other users: WebRTC peers whose origin we can verify 227 cryptographically (optimally via DTLS-SRTP). 229 Note that merely being authenticated does not make these entities 230 trusted. For instance, just because we can verify that 231 https://www.evil.org/ is owned by Dr. Evil does not mean that we can 232 trust Dr. Evil to access our camera and microphone. However, it 233 gives the user an opportunity to determine whether he wishes to trust 234 Dr. Evil or not; after all, if he desires to contact Dr. Evil 235 (perhaps to arrange for ransom payment), it's safe to temporarily 236 give him access to the camera and microphone for the purpose of the 237 call, but he doesn't want Dr. Evil to be able to access his camera 238 and microphone other than during the call. The point here is that we 239 must first identify other elements before we can determine whether 240 and how much to trust them. Additionally, sometimes we need to 241 identify the communicating peer before we know what policies to 242 apply. 244 3.2. Unauthenticated Entities 246 Other than the above entities, we are not generally able to identify 247 other network elements, thus we cannot trust them. This does not 248 mean that it is not possible to have any interaction with them, but 249 it means that we must assume that they will behave maliciously and 250 design a system which is secure even if they do so. 252 4. Overview 254 This section describes a typical WebRTC session and shows how the 255 various security elements interact and what guarantees are provided 256 to the user. The example in this section is a "best case" scenario 257 in which we provide the maximal amount of user authentication and 258 media privacy with the minimal level of trust in the calling service. 259 Simpler versions with lower levels of security are also possible and 260 are noted in the text where applicable. It's also important to 261 recognize the tension between security (or performance) and privacy. 262 The example shown here is aimed towards settings where we are more 263 concerned about secure calling than about privacy, but as we shall 264 see, there are settings where one might wish to make different 265 tradeoffs--this architecture is still compatible with those settings. 267 For the purposes of this example, we assume the topology shown in the 268 figures below. This topology is derived from the topology shown in 269 Figure 1, but separates Alice and Bob's identities from the process 270 of signaling. Specifically, Alice and Bob have relationships with 271 some Identity Provider (IdP) that supports a protocol (such as OpenID 272 Connect) that can be used to demonstrate their identity to other 273 parties. For instance, Alice might have an account with a social 274 network which she can then use to authenticate to other web sites 275 without explicitly having an account with those sites; this is a 276 fairly conventional pattern on the Web. Section 7.1 provides an 277 overview of Identity Providers and the relevant terminology. Alice 278 and Bob might have relationships with different IdPs as well. 280 This separation of identity provision and signaling isn't 281 particularly important in "closed world" cases where Alice and Bob 282 are users on the same social network and have identities based on 283 that domain (Figure 3). However, there are important settings where 284 that is not the case, such as federation (calls from one domain to 285 another; Figure 4) and calling on untrusted sites, such as where two 286 users who have a relationship via a given social network want to call 287 each other on another, untrusted, site, such as a poker site. 289 Note that the servers themselves are also authenticated by an 290 external identity service, the SSL/TLS certificate infrastructure 291 (not shown). As is conventional in the Web, all identities are 292 ultimately rooted in that system. For instance, when an IdP makes an 293 identity assertion, the Relying Party consuming that assertion is 294 able to verify because it is able to connect to the IdP via HTTPS. 296 +----------------+ 297 | | 298 | Signaling | 299 | Server | 300 | | 301 +----------------+ 302 ^ ^ 303 / \ 304 HTTPS / \ HTTPS 305 / \ 306 / \ 307 v v 308 JS API JS API 309 +-----------+ +-----------+ 310 | | Media | | 311 Alice | Browser |<---------->| Browser | Bob 312 | | (DTLS+SRTP)| | 313 +-----------+ +-----------+ 314 ^ ^--+ +--^ ^ 315 | | | | 316 v | | v 317 +-----------+ | | +-----------+ 318 | |<--------+ | | 319 | IdP1 | | | IdP2 | 320 | | +------->| | 321 +-----------+ +-----------+ 323 Figure 3: A call with IdP-based identity 325 Figure 4 shows essentially the same calling scenario but with a call 326 between two separate domains (i.e., a federated case), as in 327 Figure 2. As mentioned above, the domains communicate by some 328 unspecified protocol and providing separate signaling and identity 329 allows for calls to be authenticated regardless of the details of the 330 inter-domain protocol. 332 +----------------+ Unspecified +----------------+ 333 | | protocol | | 334 | Signaling |<----------------->| Signaling | 335 | Server | (SIP, XMPP, ...) | Server | 336 | | | | 337 +----------------+ +----------------+ 338 ^ ^ 339 | | 340 HTTPS | | HTTPS 341 | | 342 | | 343 v v 344 JS API JS API 345 +-----------+ +-----------+ 346 | | Media | | 347 Alice | Browser |<--------------------------->| Browser | Bob 348 | | DTLS+SRTP | | 349 +-----------+ +-----------+ 350 ^ ^--+ +--^ ^ 351 | | | | 352 v | | v 353 +-----------+ | | +-----------+ 354 | |<-------------------------+ | | 355 | IdP1 | | | IdP2 | 356 | | +------------------------>| | 357 +-----------+ +-----------+ 359 Figure 4: A federated call with IdP-based identity 361 4.1. Initial Signaling 363 For simplicity, assume the topology in Figure 3. Alice and Bob are 364 both users of a common calling service; they both have approved the 365 calling service to make calls (we defer the discussion of device 366 access permissions till later). They are both connected to the 367 calling service via HTTPS and so know the origin with some level of 368 confidence. They also have accounts with some identity provider. 369 This sort of identity service is becoming increasingly common in the 370 Web environment (with technologies such as Federated Google Login, 371 Facebook Connect, OAuth, OpenID, WebFinger), and is often provided as 372 a side effect service of a user's ordinary accounts with some 373 service. In this example, we show Alice and Bob using a separate 374 identity service, though the identity service may be the same entity 375 as the calling service or there may be no identity service at all. 377 Alice is logged onto the calling service and decides to call Bob. 378 She can see from the calling service that he is online and the 379 calling service presents a JS UI in the form of a button next to 380 Bob's name which says "Call". Alice clicks the button, which 381 initiates a JS callback that instantiates a PeerConnection object. 382 This does not require a security check: JS from any origin is allowed 383 to get this far. 385 Once the PeerConnection is created, the calling service JS needs to 386 set up some media. Because this is an audio/video call, it creates a 387 MediaStream with two MediaStreamTracks, one connected to an audio 388 input and one connected to a video input. At this point the first 389 security check is required: untrusted origins are not allowed to 390 access the camera and microphone, so the browser prompts Alice for 391 permission. 393 In the current W3C API, once some streams have been added, Alice's 394 browser + JS generates a signaling message [I-D.ietf-rtcweb-jsep] 395 containing: 397 o Media channel information 399 o Interactive Connectivity Establishment (ICE) [RFC5245] candidates 401 o A fingerprint attribute binding the communication to a key pair 402 [RFC5763]. Note that this key may simply be ephemerally generated 403 for this call or specific to this domain, and Alice may have a 404 large number of such keys. 406 Prior to sending out the signaling message, the PeerConnection code 407 contacts the identity service and obtains an assertion binding 408 Alice's identity to her fingerprint. The exact details depend on the 409 identity service (though as discussed in Section 7 PeerConnection can 410 be agnostic to them), but for now it's easiest to think of as an 411 OAuth token. The assertion may bind other information to the 412 identity besides the fingerprint, but at minimum it needs to bind the 413 fingerprint. 415 This message is sent to the signaling server, e.g., by XMLHttpRequest 416 [XmlHttpRequest] or by WebSockets [RFC6455], preferably over TLS 417 [RFC5246]. The signaling server processes the message from Alice's 418 browser, determines that this is a call to Bob and sends a signaling 419 message to Bob's browser (again, the format is currently undefined). 420 The JS on Bob's browser processes it, and alerts Bob to the incoming 421 call and to Alice's identity. In this case, Alice has provided an 422 identity assertion and so Bob's browser contacts Alice's identity 423 provider (again, this is done in a generic way so the browser has no 424 specific knowledge of the IdP) to verify the assertion. This allows 425 the browser to display a trusted element in the browser chrome 426 indicating that a call is coming in from Alice. If Alice is in Bob's 427 address book, then this interface might also include her real name, a 428 picture, etc. The calling site will also provide some user interface 429 element (e.g., a button) to allow Bob to answer the call, though this 430 is most likely not part of the trusted UI. 432 If Bob agrees a PeerConnection is instantiated with the message from 433 Alice's side. Then, a similar process occurs as on Alice's browser: 434 Bob's browser prompts him for device permission, the media streams 435 are created, and a return signaling message containing media 436 information, ICE candidates, and a fingerprint is sent back to Alice 437 via the signaling service. If Bob has a relationship with an IdP, 438 the message will also come with an identity assertion. 440 At this point, Alice and Bob each know that the other party wants to 441 have a secure call with them. Based purely on the interface provided 442 by the signaling server, they know that the signaling server claims 443 that the call is from Alice to Bob. This level of security is 444 provided merely by having the fingerprint in the message and having 445 that message received securely from the signaling server. Because 446 the far end sent an identity assertion along with their message, they 447 know that this is verifiable from the IdP as well. Note that if the 448 call is federated, as shown in Figure 4 then Alice is able to verify 449 Bob's identity in a way that is not mediated by either her signaling 450 server or Bob's. Rather, she verifies it directly with Bob's IdP. 452 Of course, the call works perfectly well if either Alice or Bob 453 doesn't have a relationship with an IdP; they just get a lower level 454 of assurance. I.e., they simply have whatever information their 455 calling site claims about the caller/callee's identity. Moreover, 456 Alice might wish to make an anonymous call through an anonymous 457 calling site, in which case she would of course just not provide any 458 identity assertion and the calling site would mask her identity from 459 Bob. 461 4.2. Media Consent Verification 463 As described in ([I-D.ietf-rtcweb-security]; Section 4.2) media 464 consent verification is provided via ICE. Thus, Alice and Bob 465 perform ICE checks with each other. At the completion of these 466 checks, they are ready to send non-ICE data. 468 At this point, Alice knows that (a) Bob (assuming he is verified via 469 his IdP) or someone else who the signaling service is claiming is Bob 470 is willing to exchange traffic with her and (b) that either Bob is at 471 the IP address which she has verified via ICE or there is an attacker 472 who is on-path to that IP address detouring the traffic. Note that 473 it is not possible for an attacker who is on-path between Alice and 474 Bob but not attached to the signaling service to spoof these checks 475 because they do not have the ICE credentials. Bob has the same 476 security guarantees with respect to Alice. 478 4.3. DTLS Handshake 480 Once the ICE checks have completed [more specifically, once some ICE 481 checks have completed], Alice and Bob can set up a secure channel or 482 channels. This is performed via DTLS [RFC6347] and DTLS-SRTP 483 [RFC5763] keying for SRTP [RFC3711] for the media channel and SCTP 484 over DTLS [RFC8261] for data channels. Specifically, Alice and Bob 485 perform a DTLS handshake on every component which has been 486 established by ICE. The total number of channels depends on the 487 amount of muxing; in the most likely case we are using both RTP/RTCP 488 mux and muxing multiple media streams on the same channel, in which 489 case there is only one DTLS handshake. Once the DTLS handshake has 490 completed, the keys are exported [RFC5705] and used to key SRTP for 491 the media channels. 493 At this point, Alice and Bob know that they share a set of secure 494 data and/or media channels with keys which are not known to any 495 third-party attacker. If Alice and Bob authenticated via their IdPs, 496 then they also know that the signaling service is not mounting a man- 497 in-the-middle attack on their traffic. Even if they do not use an 498 IdP, as long as they have minimal trust in the signaling service not 499 to perform a man-in-the-middle attack, they know that their 500 communications are secure against the signaling service as well 501 (i.e., that the signaling service cannot mount a passive attack on 502 the communications). 504 4.4. Communications and Consent Freshness 506 From a security perspective, everything from here on in is a little 507 anticlimactic: Alice and Bob exchange data protected by the keys 508 negotiated by DTLS. Because of the security guarantees discussed in 509 the previous sections, they know that the communications are 510 encrypted and authenticated. 512 The one remaining security property we need to establish is "consent 513 freshness", i.e., allowing Alice to verify that Bob is still prepared 514 to receive her communications so that Alice does not continue to send 515 large traffic volumes to entities which went abruptly offline. ICE 516 specifies periodic STUN keepalives but only if media is not flowing. 517 Because the consent issue is more difficult here, we require WebRTC 518 implementations to periodically send keepalives. As described in 519 Section 5.3, these keepalives MUST be based on the consent freshness 520 mechanism specified in [RFC7675]. If a keepalive fails and no new 521 ICE channels can be established, then the session is terminated. 523 5. SDP Identity Attribute 525 The SDP 'identity' attribute is a session-level attribute that is 526 used by an endpoint to convey its identity assertion to its peer. 527 The identity assertion value is encoded as Base-64, as described in 528 Section 4 of [RFC4648]. 530 The procedures in this section are based on the assumption that the 531 identity assertion of an endpoint is bound to the fingerprints of the 532 endpoint. This does not preclude the definition of alternative means 533 of binding an assertion to the endpoint, but such means are outside 534 the scope of this specification. 536 The semantics of multiple 'identity' attributes within an offer or 537 answer are undefined. Implementations SHOULD only include a single 538 'identity' attribute in an offer or answer and relying parties MAY 539 elect to ignore all but the first 'identity' attribute. 541 Name: identity 543 Value: identity-assertion 545 Usage Level: session 547 Charset Dependent: no 549 Default Value: N/A 551 Name: identity 553 Syntax: 555 identity-assertion = identity-assertion-value 556 *(SP identity-extension) 557 identity-assertion-value = base64 558 identity-extension = extension-name [ "=" extension-value ] 559 extension-name = token 560 extension-value = 1*(%x01-09 / %x0b-0c / %x0e-3a / %x3c-ff) 561 ; byte-string from [RFC4566] 563 564 566 Example: 568 a=identity:\ 569 eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\ 570 In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\ 571 IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\ 572 aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9 574 Note that long lines in the example are folded to meet the column 575 width constraints of this document; the backslash ("\") at the end of 576 a line and the carriage return that follows shall be ignored. 578 This specification does not define any extensions for the attribute. 580 The identity-assertion value is a JSON [RFC8259] encoded string. The 581 JSON object contains two keys: "assertion" and "idp". The 582 "assertion" key value contains an opaque string that is consumed by 583 the IdP. The "idp" key value contains a dictionary with one or two 584 further values that identify the IdP. See Section 7.6 for more 585 details. 587 5.1. Offer/Answer Considerations 589 This section defines the SDP Offer/Answer [RFC6454] considerations 590 for the SDP 'identity' attribute. 592 Within this section, 'initial offer' refers to the first offer in the 593 SDP session that contains an SDP "identity" attribute. 595 5.1.1. Generating the Initial SDP Offer 597 When an offerer sends an offer, in order to provide its identity 598 assertion to the peer, it includes an 'identity' attribute in the 599 offer. In addition, the offerer includes one or more SDP 600 'fingerprint' attributes. The 'identity' attribute MUST be bound to 601 all the 'fingerprint' attributes in the session description. 603 5.1.2. Answerer Processing of SDP Offer 605 When an answerer receives an offer that contains an 'identity' 606 attribute, the answerer can use the the attribute information to 607 contact the IdP, and verify the identity of the peer. If the 608 identity verification fails, the answerer MUST reject the offer. 610 5.1.3. Generating of SDP Answer 612 If the answerer elects to include an 'identity' attribute, it follows 613 the same steps as those in Section 5.1.1. The answerer can choose to 614 include or omit an 'identity' attribute independently, regardless of 615 whether the offerer did so. 617 5.1.4. Offerer Processing of SDP Answer 619 Offer processing of an 'identity' attribute is the same as that 620 described in Section 5.1.2. 622 5.1.5. Modifying the Session 624 When modifying a session, if the set of fingerprints is unchanged, 625 then the sender MAY send the same 'identity' attribute. In this 626 case, the established identity SHOULD be applied to existing DTLS 627 connections as well as new connections established using one of those 628 fingerprints. Note that [I-D.ietf-rtcweb-jsep], Section 5.2.1 629 requires that each media section use the same set of fingerprints for 630 every media section. 632 If the set of fingerprints changes, then the sender MUST either send 633 a new 'identity' attribute or none at all. Because a change in 634 fingerprints also causes a new DTLS connection to be established, the 635 receiver MUST discard all previously established identities. 637 6. Detailed Technical Description 639 6.1. Origin and Web Security Issues 641 The basic unit of permissions for WebRTC is the origin [RFC6454]. 642 Because the security of the origin depends on being able to 643 authenticate content from that origin, the origin can only be 644 securely established if data is transferred over HTTPS [RFC2818]. 645 Thus, clients MUST treat HTTP and HTTPS origins as different 646 permissions domains. [Note: this follows directly from the origin 647 security model and is stated here merely for clarity.] 648 Many web browsers currently forbid by default any active mixed 649 content on HTTPS pages. That is, when JavaScript is loaded from an 650 HTTP origin onto an HTTPS page, an error is displayed and the HTTP 651 content is not executed unless the user overrides the error. Any 652 browser which enforces such a policy will also not permit access to 653 WebRTC functionality from mixed content pages (because they never 654 display mixed content). Browsers which allow active mixed content 655 MUST nevertheless disable WebRTC functionality in mixed content 656 settings. 658 Note that it is possible for a page which was not mixed content to 659 become mixed content during the duration of the call. The major risk 660 here is that the newly arrived insecure JS might redirect media to a 661 location controlled by the attacker. Implementations MUST either 662 choose to terminate the call or display a warning at that point. 664 Also note that the security architecture depends on the keying 665 material not being available to move between origins. But, it is 666 assumed that the identity assertion can be passed to anyone that the 667 page cares to. 669 6.2. Device Permissions Model 671 Implementations MUST obtain explicit user consent prior to providing 672 access to the camera and/or microphone. Implementations MUST at 673 minimum support the following two permissions models for HTTPS 674 origins. 676 o Requests for one-time camera/microphone access. 678 o Requests for permanent access. 680 Because HTTP origins cannot be securely established against network 681 attackers, implementations MUST NOT allow the setting of permanent 682 access permissions for HTTP origins. Implementations MUST refuse all 683 permissions grants for HTTP origins. 685 In addition, they SHOULD support requests for access that promise 686 that media from this grant will be sent to a single communicating 687 peer (obviously there could be other requests for other peers). 688 E.g., "Call customerservice@ford.com". The semantics of this request 689 are that the media stream from the camera and microphone will only be 690 routed through a connection which has been cryptographically verified 691 (through the IdP mechanism or an X.509 certificate in the DTLS-SRTP 692 handshake) as being associated with the stated identity. Note that 693 it is unlikely that browsers would have an X.509 certificate, but 694 servers might. Browsers servicing such requests SHOULD clearly 695 indicate that identity to the user when asking for permission. The 696 idea behind this type of permissions is that a user might have a 697 fairly narrow list of peers he is willing to communicate with, e.g., 698 "my mother" rather than "anyone on Facebook". Narrow permissions 699 grants allow the browser to do that enforcement. 701 API Requirement: The API MUST provide a mechanism for the requesting 702 JS to relinquish the ability to see or modify the media (e.g., via 703 MediaStream.record()). Combined with secure authentication of the 704 communicating peer, this allows a user to be sure that the calling 705 site is not accessing or modifying their conversion. 707 UI Requirement: The UI MUST clearly indicate when the user's camera 708 and microphone are in use. This indication MUST NOT be 709 suppressable by the JS and MUST clearly indicate how to terminate 710 device access, and provide a UI means to immediately stop camera/ 711 microphone input without the JS being able to prevent it. 713 UI Requirement: If the UI indication of camera/microphone use are 714 displayed in the browser such that minimizing the browser window 715 would hide the indication, or the JS creating an overlapping 716 window would hide the indication, then the browser SHOULD stop 717 camera and microphone input when the indication is hidden. [Note: 718 this may not be necessary in systems that are non-windows-based 719 but that have good notifications support, such as phones.] 721 o Browsers MUST NOT permit permanent screen or application sharing 722 permissions to be installed as a response to a JS request for 723 permissions. Instead, they must require some other user action 724 such as a permissions setting or an application install experience 725 to grant permission to a site. 727 o Browsers MUST provide a separate dialog request for screen/ 728 application sharing permissions even if the media request is made 729 at the same time as camera and microphone. 731 o The browser MUST indicate any windows which are currently being 732 shared in some unambiguous way. Windows which are not visible 733 MUST NOT be shared even if the application is being shared. If 734 the screen is being shared, then that MUST be indicated. 736 Clients MAY permit the formation of data channels without any direct 737 user approval. Because sites can always tunnel data through the 738 server, further restrictions on the data channel do not provide any 739 additional security. (though see Section 6.3 for a related issue). 741 Implementations which support some form of direct user authentication 742 SHOULD also provide a policy by which a user can authorize calls only 743 to specific communicating peers. Specifically, the implementation 744 SHOULD provide the following interfaces/controls: 746 o Allow future calls to this verified user. 748 o Allow future calls to any verified user who is in my system 749 address book (this only works with address book integration, of 750 course). 752 Implementations SHOULD also provide a different user interface 753 indication when calls are in progress to users whose identities are 754 directly verifiable. Section 6.5 provides more on this. 756 6.3. Communications Consent 758 Browser client implementations of WebRTC MUST implement ICE. Server 759 gateway implementations which operate only at public IP addresses 760 MUST implement either full ICE or ICE-Lite [RFC5245]. 762 Browser implementations MUST verify reachability via ICE prior to 763 sending any non-ICE packets to a given destination. Implementations 764 MUST NOT provide the ICE transaction ID to JavaScript during the 765 lifetime of the transaction (i.e., during the period when the ICE 766 stack would accept a new response for that transaction). The JS MUST 767 NOT be permitted to control the local ufrag and password, though it 768 of course knows it. 770 While continuing consent is required, the ICE [RFC5245]; Section 10 771 keepalives use STUN Binding Indications which are one-way and 772 therefore not sufficient. The current WG consensus is to use ICE 773 Binding Requests for continuing consent freshness. ICE already 774 requires that implementations respond to such requests, so this 775 approach is maximally compatible. A separate document will profile 776 the ICE timers to be used; see [RFC7675]. 778 6.4. IP Location Privacy 780 A side effect of the default ICE behavior is that the peer learns 781 one's IP address, which leaks large amounts of location information. 782 This has negative privacy consequences in some circumstances. The 783 API requirements in this section are intended to mitigate this issue. 784 Note that these requirements are NOT intended to protect the user's 785 IP address from a malicious site. In general, the site will learn at 786 least a user's server reflexive address from any HTTP transaction. 787 Rather, these requirements are intended to allow a site to cooperate 788 with the user to hide the user's IP address from the other side of 789 the call. Hiding the user's IP address from the server requires some 790 sort of explicit privacy preserving mechanism on the client (e.g., 791 Tor Browser [https://www.torproject.org/projects/torbrowser.html.en]) 792 and is out of scope for this specification. 794 API Requirement: The API MUST provide a mechanism to allow the JS to 795 suppress ICE negotiation (though perhaps to allow candidate 796 gathering) until the user has decided to answer the call [note: 797 determining when the call has been answered is a question for the 798 JS.] This enables a user to prevent a peer from learning their IP 799 address if they elect not to answer a call and also from learning 800 whether the user is online. 802 API Requirement: The API MUST provide a mechanism for the calling 803 application JS to indicate that only TURN candidates are to be 804 used. This prevents the peer from learning one's IP address at 805 all. This mechanism MUST also permit suppression of the related 806 address field, since that leaks local addresses. 808 API Requirement: The API MUST provide a mechanism for the calling 809 application to reconfigure an existing call to add non-TURN 810 candidates. Taken together, this and the previous requirement 811 allow ICE negotiation to start immediately on incoming call 812 notification, thus reducing post-dial delay, but also to avoid 813 disclosing the user's IP address until they have decided to 814 answer. They also allow users to completely hide their IP address 815 for the duration of the call. Finally, they allow a mechanism for 816 the user to optimize performance by reconfiguring to allow non- 817 turn candidates during an active call if the user decides they no 818 longer need to hide their IP address 820 Note that some enterprises may operate proxies and/or NATs designed 821 to hide internal IP addresses from the outside world. WebRTC 822 provides no explicit mechanism to allow this function. Either such 823 enterprises need to proxy the HTTP/HTTPS and modify the SDP and/or 824 the JS, or there needs to be browser support to set the "TURN-only" 825 policy regardless of the site's preferences. 827 6.5. Communications Security 829 Implementations MUST implement SRTP [RFC3711]. Implementations MUST 830 implement DTLS [RFC6347] and DTLS-SRTP [RFC5763][RFC5764] for SRTP 831 keying. Implementations MUST implement [RFC8261]. 833 All media channels MUST be secured via SRTP and SRTCP. Media traffic 834 MUST NOT be sent over plain (unencrypted) RTP or RTCP; that is, 835 implementations MUST NOT negotiate cipher suites with NULL encryption 836 modes. DTLS-SRTP MUST be offered for every media channel. WebRTC 837 implementations MUST NOT offer SDP Security Descriptions [RFC4568] or 838 select it if offered. A SRTP MKI MUST NOT be used. 840 All data channels MUST be secured via DTLS. 842 All implementations MUST implement DTLS 1.0, with the cipher suite 843 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA with the the P-256 curve 844 [FIPS186]. The DTLS-SRTP protection profile 845 SRTP_AES128_CM_HMAC_SHA1_80 MUST be supported for SRTP. 846 Implementations SHOULD implement DTLS 1.2 with the 847 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite. 848 Implementations MUST favor cipher suites which support (Perfect 849 Forward Secrecy) PFS over non-PFS cipher suites and SHOULD favor AEAD 850 over non-AEAD cipher suites. 852 Implementations MUST NOT implement DTLS renegotiation and MUST reject 853 it with a "no_renegotiation" alert if offered. 855 API Requirement: The API MUST generate a new authentication key pair 856 for every new call by default. This is intended to allow for 857 unlinkability. 859 API Requirement: The API MUST provide a means to reuse a key pair 860 for calls. This can be used to enable key continuity-based 861 authentication, and could be used to amortize key generation 862 costs. 864 API Requirement: Unless the user specifically configures an external 865 key pair, different key pairs MUST be used for each origin. (This 866 avoids creating a super-cookie.) 868 API Requirement: When DTLS-SRTP is used, the API MUST NOT permit the 869 JS to obtain the negotiated keying material. This requirement 870 preserves the end-to-end security of the media. 872 UI Requirements: A user-oriented client MUST provide an "inspector" 873 interface which allows the user to determine the security 874 characteristics of the media. 876 The following properties SHOULD be displayed "up-front" in the 877 browser chrome, i.e., without requiring the user to ask for them: 879 * A client MUST provide a user interface through which a user may 880 determine the security characteristics for currently-displayed 881 audio and video stream(s) 883 * A client MUST provide a user interface through which a user may 884 determine the security characteristics for transmissions of 885 their microphone audio and camera video. 887 * If the far endpoint was directly verified, either via a third- 888 party verifiable X.509 certificate or via a Web IdP mechanism 889 (see Section 7) the "security characteristics" MUST include the 890 verified information. X.509 identities and Web IdP identities 891 have similar semantics and should be displayed in a similar 892 way. 894 The following properties are more likely to require some "drill- 895 down" from the user: 897 * The "security characteristics" MUST indicate the cryptographic 898 algorithms in use (For example: "AES-CBC".) However, if Null 899 ciphers are used, that MUST be presented to the user at the 900 top-level UI. 902 * The "security characteristics" MUST indicate whether PFS is 903 provided. 905 * The "security characteristics" MUST include some mechanism to 906 allow an out-of-band verification of the peer, such as a 907 certificate fingerprint or a Short Authentication String (SAS). 909 7. Web-Based Peer Authentication 911 In a number of cases, it is desirable for the endpoint (i.e., the 912 browser) to be able to directly identify the endpoint on the other 913 side without trusting the signaling service to which they are 914 connected. For instance, users may be making a call via a federated 915 system where they wish to get direct authentication of the other 916 side. Alternately, they may be making a call on a site which they 917 minimally trust (such as a poker site) but to someone who has an 918 identity on a site they do trust (such as a social network.) 920 Recently, a number of Web-based identity technologies (OAuth, 921 Facebook Connect etc.) have been developed. While the details vary, 922 what these technologies share is that they have a Web-based (i.e., 923 HTTP/HTTPS) identity provider which attests to your identity. For 924 instance, if I have an account at example.org, I could use the 925 example.org identity provider to prove to others that I was 926 alice@example.org. The development of these technologies allows us 927 to separate calling from identity provision: I could call you on 928 Poker Galaxy but identify myself as alice@example.org. 930 Whatever the underlying technology, the general principle is that the 931 party which is being authenticated is NOT the signaling site but 932 rather the user (and their browser). Similarly, the relying party is 933 the browser and not the signaling site. Thus, the browser MUST 934 generate the input to the IdP assertion process and display the 935 results of the verification process to the user in a way which cannot 936 be imitated by the calling site. 938 The mechanisms defined in this document do not require the browser to 939 implement any particular identity protocol or to support any 940 particular IdP. Instead, this document provides a generic interface 941 which any IdP can implement. Thus, new IdPs and protocols can be 942 introduced without change to either the browser or the calling 943 service. This avoids the need to make a commitment to any particular 944 identity protocol, although browsers may opt to directly implement 945 some identity protocols in order to provide superior performance or 946 UI properties. 948 7.1. Trust Relationships: IdPs, APs, and RPs 950 Any federated identity protocol has three major participants: 952 Authenticating Party (AP): The entity which is trying to establish 953 its identity. 955 Identity Provider (IdP): The entity which is vouching for the AP's 956 identity. 958 Relying Party (RP): The entity which is trying to verify the AP's 959 identity. 961 The AP and the IdP have an account relationship of some kind: the AP 962 registers with the IdP and is able to subsequently authenticate 963 directly to the IdP (e.g., with a password). This means that the 964 browser must somehow know which IdP(s) the user has an account 965 relationship with. This can either be something that the user 966 configures into the browser or that is configured at the calling site 967 and then provided to the PeerConnection by the Web application at the 968 calling site. The use case for having this information configured 969 into the browser is that the user may "log into" the browser to bind 970 it to some identity. This is becoming common in new browsers. 971 However, it should also be possible for the IdP information to simply 972 be provided by the calling application. 974 At a high level there are two kinds of IdPs: 976 Authoritative: IdPs which have verifiable control of some section 977 of the identity space. For instance, in the realm of e-mail, the 978 operator of "example.com" has complete control of the namespace 979 ending in "@example.com". Thus, "alice@example.com" is whoever 980 the operator says it is. Examples of systems with authoritative 981 identity providers include DNSSEC, RFC 4474, and Facebook Connect 982 (Facebook identities only make sense within the context of the 983 Facebook system). 985 Third-Party: IdPs which don't have control of their section of the 986 identity space but instead verify user's identities via some 987 unspecified mechanism and then attest to it. Because the IdP 988 doesn't actually control the namespace, RPs need to trust that the 989 IdP is correctly verifying AP identities, and there can 990 potentially be multiple IdPs attesting to the same section of the 991 identity space. Probably the best-known example of a third-party 992 identity provider is SSL/TLS certificates, where there are a large 993 number of CAs all of whom can attest to any domain name. 995 If an AP is authenticating via an authoritative IdP, then the RP does 996 not need to explicitly configure trust in the IdP at all. The 997 identity mechanism can directly verify that the IdP indeed made the 998 relevant identity assertion (a function provided by the mechanisms in 999 this document), and any assertion it makes about an identity for 1000 which it is authoritative is directly verifiable. Note that this 1001 does not mean that the IdP might not lie, but that is a 1002 trustworthiness judgement that the user can make at the time he looks 1003 at the identity. 1005 By contrast, if an AP is authenticating via a third-party IdP, the RP 1006 needs to explicitly trust that IdP (hence the need for an explicit 1007 trust anchor list in PKI-based SSL/TLS clients). The list of 1008 trustable IdPs needs to be configured directly into the browser, 1009 either by the user or potentially by the browser manufacturer. This 1010 is a significant advantage of authoritative IdPs and implies that if 1011 third-party IdPs are to be supported, the potential number needs to 1012 be fairly small. 1014 7.2. Overview of Operation 1016 In order to provide security without trusting the calling site, the 1017 PeerConnection component of the browser must interact directly with 1018 the IdP. The details of the mechanism are described in the W3C API 1019 specification, but the general idea is that the PeerConnection 1020 component downloads JS from a specific location on the IdP dictated 1021 by the IdP domain name. That JS (the "IdP proxy") runs in an 1022 isolated security context within the browser and the PeerConnection 1023 talks to it via a secure message passing channel. 1025 Note that there are two logically separate functions here: 1027 o Identity assertion generation. 1029 o Identity assertion verification. 1031 The same IdP JS "endpoint" is used for both functions but of course a 1032 given IdP might behave differently and load new JS to perform one 1033 function or the other. 1035 +--------------------------------------+ 1036 | Browser | 1037 | | 1038 | +----------------------------------+ | 1039 | | https://calling-site.example.com | | 1040 | | | | 1041 | | Calling JS Code | | 1042 | | ^ | | 1043 | +---------------|------------------+ | 1044 | | API Calls | 1045 | v | 1046 | PeerConnection | 1047 | ^ | 1048 | | API Calls | 1049 | +-----------|-------------+ | +---------------+ 1050 | | v | | | | 1051 | | IdP Proxy |<-------->| Identity | 1052 | | | | | Provider | 1053 | | https://idp.example.org | | | | 1054 | +-------------------------+ | +---------------+ 1055 | | 1056 +--------------------------------------+ 1058 When the PeerConnection object wants to interact with the IdP, the 1059 sequence of events is as follows: 1061 1. The browser (the PeerConnection component) instantiates an IdP 1062 proxy. This allows the IdP to load whatever JS is necessary into 1063 the proxy. The resulting code runs in the IdP's security 1064 context. 1066 2. The IdP registers an object with the browser that conforms to the 1067 API defined in [webrtc-api]. 1069 3. The browser invokes methods on the object registered by the IdP 1070 proxy to create or verify identity assertions. 1072 This approach allows us to decouple the browser from any particular 1073 identity provider; the browser need only know how to load the IdP's 1074 JavaScript--the location of which is determined based on the IdP's 1075 identity--and to call the generic API for requesting and verifying 1076 identity assertions. The IdP provides whatever logic is necessary to 1077 bridge the generic protocol to the IdP's specific requirements. 1078 Thus, a single browser can support any number of identity protocols, 1079 including being forward compatible with IdPs which did not exist at 1080 the time the browser was written. 1082 7.3. Items for Standardization 1084 There are two parts to this work: 1086 o The precise information from the signaling message that must be 1087 cryptographically bound to the user's identity and a mechanism for 1088 carrying assertions in JSEP messages. This is specified in 1089 Section 7.4. 1091 o The interface to the IdP, which is defined in the companion W3C 1092 WebRTC API specification [webrtc-api]. 1094 The WebRTC API specification also defines JavaScript interfaces that 1095 the calling application can use to specify which IdP to use. That 1096 API also provides access to the assertion-generation capability and 1097 the status of the validation process. 1099 7.4. Binding Identity Assertions to JSEP Offer/Answer Transactions 1101 An identity assertion binds the user's identity (as asserted by the 1102 IdP) to the SDP offer/answer exchange and specifically to the media. 1103 In order to achieve this, the PeerConnection must provide the DTLS- 1104 SRTP fingerprint to be bound to the identity. This is provided as a 1105 JavaScript object (also known as a dictionary or hash) with a single 1106 "fingerprint" key, as shown below: 1108 { 1109 "fingerprint": [ { 1110 "algorithm": "sha-256", 1111 "digest": "4A:AD:B9:B1:3F:...:E5:7C:AB" 1112 }, { 1113 "algorithm": "sha-1", 1114 "digest": "74:E9:76:C8:19:...:F4:45:6B" 1115 } ] 1116 } 1118 The "fingerprint" value is an array of objects. Each object in the 1119 array contains "algorithm" and "digest" values, which correspond 1120 directly to the algorithm and digest values in the "fingerprint" 1121 attribute of the SDP [RFC8122]. 1123 This object is encoded in a JSON [RFC8259] string for passing to the 1124 IdP. 1126 This structure does not need to be interpreted by the IdP or the IdP 1127 proxy. It is consumed solely by the RP's browser. The IdP merely 1128 treats it as an opaque value to be attested to. Thus, new parameters 1129 can be added to the assertion without modifying the IdP. 1131 7.4.1. Carrying Identity Assertions 1133 Once an IdP has generated an assertion, it is attached to the SDP 1134 offer/answer message. This is done by adding a new 'identity' 1135 attribute to the SDP. The sole contents of this value are a 1136 Base64-encoded [RFC4648] identity assertion. For example: 1138 v=0 1139 o=- 1181923068 1181923196 IN IP4 ua1.example.com 1140 s=example1 1141 c=IN IP4 ua1.example.com 1142 a=fingerprint:sha-1 \ 1143 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 1144 a=identity:\ 1145 eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\ 1146 In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\ 1147 IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\ 1148 aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9 1149 a=... 1150 t=0 0 1151 m=audio 6056 RTP/SAVP 0 1152 a=sendrecv 1153 ... 1155 Note that long lines in the example are folded to meet the column 1156 width constraints of this document; the backslash ("\") at the end of 1157 a line and the carriage return that follows shall be ignored. 1159 The 'identity' attribute attests to all "fingerprint" attributes in 1160 the session description. It is therefore a session-level attribute. 1162 Multiple "fingerprint" values can be used to offer alternative 1163 certificates for a peer. The "identity" attribute MUST include all 1164 fingerprint values that are included in "fingerprint" attributes of 1165 the session description. 1167 The RP browser MUST verify that the in-use certificate for a DTLS 1168 connection is in the set of fingerprints returned from the IdP when 1169 verifying an assertion. 1171 7.5. Determining the IdP URI 1173 In order to ensure that the IdP is under control of the domain owner 1174 rather than someone who merely has an account on the domain owner's 1175 server (e.g., in shared hosting scenarios), the IdP JavaScript is 1176 hosted at a deterministic location based on the IdP's domain name. 1177 Each IdP proxy instance is associated with two values: 1179 Authority: The authority [RFC3986] at which the IdP's service is 1180 hosted. Note that this may include a non-default port or a 1181 userinfo component, but neither will be available in a certificate 1182 verifying the site. 1184 protocol: The specific IdP protocol which the IdP is using. This is 1185 a completely opaque IdP-specific string, but allows an IdP to 1186 implement two protocols in parallel. This value may be the empty 1187 string. If no value for protocol is provided, a value of 1188 "default" is used. 1190 Each IdP MUST serve its initial entry page (i.e., the one loaded by 1191 the IdP proxy) from a well-known URI [RFC5785]. The well-known URI 1192 for an IdP proxy is formed from the following URI components: 1194 1. The scheme, "https:". An IdP MUST be loaded using HTTPS 1195 [RFC2818]. 1197 2. The authority [RFC3986]. As noted above, the authority MAY 1198 contain a non-default port number or userinfo sub-component. 1199 Both are removed when determining if an asserted identity matches 1200 the name of the IdP. 1202 3. The path, starting with "/.well-known/idp-proxy/" and appended 1203 with the IdP protocol. Note that the separator characters '/' 1204 (%2F) and '\' (%5C) MUST NOT be permitted in the protocol field, 1205 lest an attacker be able to direct requests outside of the 1206 controlled "/.well-known/" prefix. Query and fragment values MAY 1207 be used by including '?' or '#' characters. 1209 For example, for the IdP "identity.example.com" and the protocol 1210 "example", the URL would be: 1212 https://identity.example.com/.well-known/idp-proxy/example 1214 The IdP MAY redirect requests to this URL, but they MUST retain the 1215 "https" scheme. This changes the effective origin of the IdP, but 1216 not the domain of the identities that the IdP is permitted to assert 1217 and validate. I.e., the IdP is still regarded as authoritative for 1218 the original domain. 1220 7.5.1. Authenticating Party 1222 How an AP determines the appropriate IdP domain is out of scope of 1223 this specification. In general, however, the AP has some actual 1224 account relationship with the IdP, as this identity is what the IdP 1225 is attesting to. Thus, the AP somehow supplies the IdP information 1226 to the browser. Some potential mechanisms include: 1228 o Provided by the user directly. 1230 o Selected from some set of IdPs known to the calling site. E.g., a 1231 button that shows "Authenticate via Facebook Connect" 1233 7.5.2. Relying Party 1235 Unlike the AP, the RP need not have any particular relationship with 1236 the IdP. Rather, it needs to be able to process whatever assertion 1237 is provided by the AP. As the assertion contains the IdP's identity, 1238 the URI can be constructed directly from the assertion, and thus the 1239 RP can directly verify the technical validity of the assertion with 1240 no user interaction. Authoritative assertions need only be 1241 verifiable. Third-party assertions also MUST be verified against 1242 local policy, as described in Section 8.1. 1244 7.6. Requesting Assertions 1246 The input to identity assertion is the JSON-encoded object described 1247 in Section 7.4 that contains the set of certificate fingerprints the 1248 browser intends to use. This string is treated as opaque from the 1249 perspective of the IdP. 1251 The browser also identifies the origin that the PeerConnection is run 1252 in, which allows the IdP to make decisions based on who is requesting 1253 the assertion. 1255 An application can optionally provide a user identifier hint when 1256 specifying an IdP. This value is a hint that the IdP can use to 1257 select amongst multiple identities, or to avoid providing assertions 1258 for unwanted identities. The "username" is a string that has no 1259 meaning to any entity other than the IdP, it can contain any data the 1260 IdP needs in order to correctly generate an assertion. 1262 An identity assertion that is successfully provided by the IdP 1263 consists of the following information: 1265 idp: The domain name of an IdP and the protocol string. This MAY 1266 identify a different IdP or protocol from the one that generated 1267 the assertion. 1269 assertion: An opaque value containing the assertion itself. This is 1270 only interpretable by the identified IdP or the IdP code running 1271 in the client. 1273 Figure 5 shows an example assertion formatted as JSON. In this case, 1274 the message has presumably been digitally signed/MACed in some way 1275 that the IdP can later verify it, but this is an implementation 1276 detail and out of scope of this document. Line breaks are inserted 1277 solely for readability. 1279 { 1280 "idp":{ 1281 "domain": "example.org", 1282 "protocol": "bogus" 1283 }, 1284 "assertion": "{\"identity\":\"bob@example.org\", 1285 \"contents\":\"abcdefghijklmnopqrstuvwyz\", 1286 \"signature\":\"010203040506\"}" 1287 } 1289 Figure 5: Example assertion 1291 For use in signaling, the assertion is serialized into JSON, 1292 Base64-encoded [RFC4648], and used as the value of the "identity" 1293 attribute. 1295 7.7. Managing User Login 1297 In order to generate an identity assertion, the IdP needs proof of 1298 the user's identity. It is common practice to authenticate users 1299 (using passwords or multi-factor authentication), then use Cookies 1300 [RFC6265] or HTTP authentication [RFC7617] for subsequent exchanges. 1302 The IdP proxy is able to access cookies, HTTP authentication or other 1303 persistent session data because it operates in the security context 1304 of the IdP origin. Therefore, if a user is logged in, the IdP could 1305 have all the information needed to generate an assertion. 1307 An IdP proxy is unable to generate an assertion if the user is not 1308 logged in, or the IdP wants to interact with the user to acquire more 1309 information before generating the assertion. If the IdP wants to 1310 interact with the user before generating an assertion, the IdP proxy 1311 can fail to generate an assertion and instead indicate a URL where 1312 login should proceed. 1314 The application can then load the provided URL to enable the user to 1315 enter credentials. The communication between the application and the 1316 IdP is described in [webrtc-api]. 1318 8. Verifying Assertions 1320 The input to identity validation is the assertion string taken from a 1321 decoded 'identity' attribute. 1323 The IdP proxy verifies the assertion. Depending on the identity 1324 protocol, the proxy might contact the IdP server or other servers. 1325 For instance, an OAuth-based protocol will likely require using the 1326 IdP as an oracle, whereas with a signature-based scheme might be able 1327 to verify the assertion without contacting the IdP, provided that it 1328 has cached the relevant public key. 1330 Regardless of the mechanism, if verification succeeds, a successful 1331 response from the IdP proxy consists of the following information: 1333 identity: The identity of the AP from the IdP's perspective. 1334 Details of this are provided in Section 8.1. 1336 contents: The original unmodified string provided by the AP as input 1337 to the assertion generation process. 1339 Figure 6 shows an example response formatted as JSON for illustrative 1340 purposes. 1342 { 1343 "identity": "bob@example.org", 1344 "contents": "{\"fingerprint\":[ ... ]}" 1345 } 1347 Figure 6: Example verification result 1349 8.1. Identity Formats 1351 The identity provided from the IdP to the RP browser MUST consist of 1352 a string representing the user's identity. This string is in the 1353 form "@", where "user" consists of any character except 1354 '@', and domain is an internationalized domain name [RFC5890]. 1356 The PeerConnection API MUST check this string as follows: 1358 1. If the domain portion of the string is equal to the domain name 1359 of the IdP proxy, then the assertion is valid, as the IdP is 1360 authoritative for this domain. Comparison of domain names is 1361 done using the label equivalence rule defined in Section 2.3.2.4 1362 of [RFC5890]. 1364 2. If the domain portion of the string is not equal to the domain 1365 name of the IdP proxy, then the PeerConnection object MUST reject 1366 the assertion unless: 1368 1. the IdP domain is trusted as an acceptable third-party IdP; 1369 and 1371 2. local policy is configured to trust this IdP domain for the 1372 domain portion of the identity string. 1374 Sites that have identities that do not fit into the RFC822 style (for 1375 instance, identifiers that are simple numeric values, or values that 1376 contain '@' characters) SHOULD convert them to this form by escaping 1377 illegal characters and appending their IdP domain (e.g., 1378 user%40133@identity.example.com), thus ensuring that they are 1379 authoritative for the identity. 1381 9. Security Considerations 1383 Much of the security analysis of this problem is contained in 1384 [I-D.ietf-rtcweb-security] or in the discussion of the particular 1385 issues above. In order to avoid repetition, this section focuses on 1386 (a) residual threats that are not addressed by this document and (b) 1387 threats produced by failure/misbehavior of one of the components in 1388 the system. 1390 9.1. Communications Security 1392 IF HTTPS is not used to secure communications to the signaling 1393 server, and the identity mechanism used in Section 7 is not used, 1394 then any on-path attacker can replace the DTLS-SRTP fingerprints in 1395 the handshake and thus substitute its own identity for that of either 1396 endpoint. 1398 Even if HTTPS is used, the signaling server can potentially mount a 1399 man-in-the-middle attack unless implementations have some mechanism 1400 for independently verifying keys. The UI requirements in Section 6.5 1401 are designed to provide such a mechanism for motivated/security 1402 conscious users, but are not suitable for general use. The identity 1403 service mechanisms in Section 7 are more suitable for general use. 1404 Note, however, that a malicious signaling service can strip off any 1405 such identity assertions, though it cannot forge new ones. Note that 1406 all of the third-party security mechanisms available (whether X.509 1407 certificates or a third-party IdP) rely on the security of the third 1408 party--this is of course also true of your connection to the Web site 1409 itself. Users who wish to assure themselves of security against a 1410 malicious identity provider can only do so by verifying peer 1411 credentials directly, e.g., by checking the peer's fingerprint 1412 against a value delivered out of band. 1414 In order to protect against malicious content JavaScript, that 1415 JavaScript MUST NOT be allowed to have direct access to---or perform 1416 computations with---DTLS keys. For instance, if content JS were able 1417 to compute digital signatures, then it would be possible for content 1418 JS to get an identity assertion for a browser's generated key and 1419 then use that assertion plus a signature by the key to authenticate a 1420 call protected under an ephemeral Diffie-Hellman (DH) key controlled 1421 by the content JS, thus violating the security guarantees otherwise 1422 provided by the IdP mechanism. Note that it is not sufficient merely 1423 to deny the content JS direct access to the keys, as some have 1424 suggested doing with the WebCrypto API [webcrypto]. The JS must also 1425 not be allowed to perform operations that would be valid for a DTLS 1426 endpoint. By far the safest approach is simply to deny the ability 1427 to perform any operations that depend on secret information 1428 associated with the key. Operations that depend on public 1429 information, such as exporting the public key are of course safe. 1431 9.2. Privacy 1433 The requirements in this document are intended to allow: 1435 o Users to participate in calls without revealing their location. 1437 o Potential callees to avoid revealing their location and even 1438 presence status prior to agreeing to answer a call. 1440 However, these privacy protections come at a performance cost in 1441 terms of using TURN relays and, in the latter case, delaying ICE. 1442 Sites SHOULD make users aware of these tradeoffs. 1444 Note that the protections provided here assume a non-malicious 1445 calling service. As the calling service always knows the users 1446 status and (absent the use of a technology like Tor) their IP 1447 address, they can violate the users privacy at will. Users who wish 1448 privacy against the calling sites they are using must use separate 1449 privacy enhancing technologies such as Tor. Combined WebRTC/Tor 1450 implementations SHOULD arrange to route the media as well as the 1451 signaling through Tor. Currently this will produce very suboptimal 1452 performance. 1454 Additionally, any identifier which persists across multiple calls is 1455 potentially a problem for privacy, especially for anonymous calling 1456 services. Such services SHOULD instruct the browser to use separate 1457 DTLS keys for each call and also to use TURN throughout the call. 1458 Otherwise, the other side will learn linkable information. 1459 Additionally, browsers SHOULD implement the privacy-preserving CNAME 1460 generation mode of [RFC7022]. 1462 9.3. Denial of Service 1464 The consent mechanisms described in this document are intended to 1465 mitigate denial of service attacks in which an attacker uses clients 1466 to send large amounts of traffic to a victim without the consent of 1467 the victim. While these mechanisms are sufficient to protect victims 1468 who have not implemented WebRTC at all, WebRTC implementations need 1469 to be more careful. 1471 Consider the case of a call center which accepts calls via WebRTC. 1472 An attacker proxies the call center's front-end and arranges for 1473 multiple clients to initiate calls to the call center. Note that 1474 this requires user consent in many cases but because the data channel 1475 does not need consent, he can use that directly. Since ICE will 1476 complete, browsers can then be induced to send large amounts of data 1477 to the victim call center if it supports the data channel at all. 1478 Preventing this attack requires that automated WebRTC implementations 1479 implement sensible flow control and have the ability to triage out 1480 (i.e., stop responding to ICE probes on) calls which are behaving 1481 badly, and especially to be prepared to remotely throttle the data 1482 channel in the absence of plausible audio and video (which the 1483 attacker cannot control). 1485 Another related attack is for the signaling service to swap the ICE 1486 candidates for the audio and video streams, thus forcing a browser to 1487 send video to the sink that the other victim expects will contain 1488 audio (perhaps it is only expecting audio!) potentially causing 1489 overload. Muxing multiple media flows over a single transport makes 1490 it harder to individually suppress a single flow by denying ICE 1491 keepalives. Either media-level (RTCP) mechanisms must be used or the 1492 implementation must deny responses entirely, thus terminating the 1493 call. 1495 Yet another attack, suggested by Magnus Westerlund, is for the 1496 attacker to cross-connect offers and answers as follows. It induces 1497 the victim to make a call and then uses its control of other users 1498 browsers to get them to attempt a call to someone. It then 1499 translates their offers into apparent answers to the victim, which 1500 looks like large-scale parallel forking. The victim still responds 1501 to ICE responses and now the browsers all try to send media to the 1502 victim. Implementations can defend themselves from this attack by 1503 only responding to ICE Binding Requests for a limited number of 1504 remote ufrags (this is the reason for the requirement that the JS not 1505 be able to control the ufrag and password). 1507 [I-D.ietf-rtcweb-rtp-usage] Section 13 documents a number of 1508 potential RTCP-based DoS attacks and countermeasures. 1510 Note that attacks based on confusing one end or the other about 1511 consent are possible even in the face of the third-party identity 1512 mechanism as long as major parts of the signaling messages are not 1513 signed. On the other hand, signing the entire message severely 1514 restricts the capabilities of the calling application, so there are 1515 difficult tradeoffs here. 1517 9.4. IdP Authentication Mechanism 1519 This mechanism relies for its security on the IdP and on the 1520 PeerConnection correctly enforcing the security invariants described 1521 above. At a high level, the IdP is attesting that the user 1522 identified in the assertion wishes to be associated with the 1523 assertion. Thus, it must not be possible for arbitrary third parties 1524 to get assertions tied to a user or to produce assertions that RPs 1525 will accept. 1527 9.4.1. PeerConnection Origin Check 1529 Fundamentally, the IdP proxy is just a piece of HTML and JS loaded by 1530 the browser, so nothing stops a Web attacker from creating their own 1531 IFRAME, loading the IdP proxy HTML/JS, and requesting a signature 1532 over his own keys rather than those generated in the browser. 1533 However, that proxy would be in the attacker's origin, not the IdP's 1534 origin. Only the browser itself can instantiate a context that (a) 1535 is in the IdP's origin and (b) exposes the correct API surface. 1536 Thus, the IdP proxy on the sender's side MUST ensure that it is 1537 running in the IdP's origin prior to issuing assertions. 1539 Note that this check only asserts that the browser (or some other 1540 entity with access to the user's authentication data) attests to the 1541 request and hence to the fingerprint. It does not demonstrate that 1542 the browser has access to the associated private key, and therefore 1543 an attacker can attach their own identity to another party's keying 1544 material, thus making a call which comes from Alice appear to come 1545 from the attacker. See [I-D.ietf-mmusic-sdp-uks] for defenses 1546 against this form of attack. 1548 9.4.2. IdP Well-known URI 1550 As described in Section 7.5 the IdP proxy HTML/JS landing page is 1551 located at a well-known URI based on the IdP's domain name. This 1552 requirement prevents an attacker who can write some resources at the 1553 IdP (e.g., on one's Facebook wall) from being able to impersonate the 1554 IdP. 1556 9.4.3. Privacy of IdP-generated identities and the hosting site 1558 Depending on the structure of the IdP's assertions, the calling site 1559 may learn the user's identity from the perspective of the IdP. In 1560 many cases this is not an issue because the user is authenticating to 1561 the site via the IdP in any case, for instance when the user has 1562 logged in with Facebook Connect and is then authenticating their call 1563 with a Facebook identity. However, in other case, the user may not 1564 have already revealed their identity to the site. In general, IdPs 1565 SHOULD either verify that the user is willing to have their identity 1566 revealed to the site (e.g., through the usual IdP permissions dialog) 1567 or arrange that the identity information is only available to known 1568 RPs (e.g., social graph adjacencies) but not to the calling site. 1569 The "origin" field of the signature request can be used to check that 1570 the user has agreed to disclose their identity to the calling site; 1571 because it is supplied by the PeerConnection it can be trusted to be 1572 correct. 1574 9.4.4. Security of Third-Party IdPs 1576 As discussed above, each third-party IdP represents a new universal 1577 trust point and therefore the number of these IdPs needs to be quite 1578 limited. Most IdPs, even those which issue unqualified identities 1579 such as Facebook, can be recast as authoritative IdPs (e.g., 1580 123456@facebook.com). However, in such cases, the user interface 1581 implications are not entirely desirable. One intermediate approach 1582 is to have special (potentially user configurable) UI for large 1583 authoritative IdPs, thus allowing the user to instantly grasp that 1584 the call is being authenticated by Facebook, Google, etc. 1586 9.4.4.1. Confusable Characters 1588 Because a broad range of characters are permitted in identity 1589 strings, it may be possible for attackers to craft identities which 1590 are confusable with other identities (see [RFC6943] for more on this 1591 topic). This is a problem with any identifier space of this type 1592 (e.g., e-mail addresses). Those minting identifers should avoid 1593 mixed scripts and similar confusable characters. Those presenting 1594 these identifiers to a user should consider highlighting cases of 1595 mixed script usage (see [RFC5890], section 4.4). Other best 1596 practices are still in development. 1598 9.4.5. Web Security Feature Interactions 1600 A number of optional Web security features have the potential to 1601 cause issues for this mechanism, as discussed below. 1603 9.4.5.1. Popup Blocking 1605 The IdP proxy is unable to generate popup windows, dialogs or any 1606 other form of user interactions. This prevents the IdP proxy from 1607 being used to circumvent user interaction. The "LOGINNEEDED" message 1608 allows the IdP proxy to inform the calling site of a need for user 1609 login, providing the information necessary to satisfy this 1610 requirement without resorting to direct user interaction from the IdP 1611 proxy itself. 1613 9.4.5.2. Third Party Cookies 1615 Some browsers allow users to block third party cookies (cookies 1616 associated with origins other than the top level page) for privacy 1617 reasons. Any IdP which uses cookies to persist logins will be broken 1618 by third-party cookie blocking. One option is to accept this as a 1619 limitation; another is to have the PeerConnection object disable 1620 third-party cookie blocking for the IdP proxy. 1622 10. IANA Considerations 1624 This specification defines the "identity" SDP attribute per the 1625 procedures of Section 8.2.4 of [RFC4566]. The required information 1626 for the registration is included here: 1628 Contact Name: Eric Rescorla (ekr@rftm.com) 1630 Attribute Name: identity 1632 Long Form: identity 1634 Type of Attribute: session-level 1636 Charset Considerations: This attribute is not subject to the charset 1637 attribute. 1639 Purpose: This attribute carries an identity assertion, binding an 1640 identity to the transport-level security session. 1642 Appropriate Values: See Section 5 of RFCXXXX [[Editor Note: This 1643 document.]] 1645 Mux Category: NORMAL. 1647 11. Acknowledgements 1649 Bernard Aboba, Harald Alvestrand, Richard Barnes, Dan Druta, Cullen 1650 Jennings, Hadriel Kaplan, Matthew Kaufman, Jim McEachern, Martin 1651 Thomson, Magnus Westerland. Matthew Kaufman provided the UI material 1652 in Section 6.5. Christer Holmberg provided the initial version of 1653 Section 5.1. 1655 12. Changes 1657 [RFC Editor: Please remove this section prior to publication.] 1659 12.1. Changes since -15 1661 Rewrite the Identity section in more conventional offer/answer 1662 format. 1664 Clarify rules on changing identities. 1666 12.2. Changes since -11 1668 Update discussion of IdP security model 1670 Replace "domain name" with RFC 3986 Authority 1672 Clean up discussion of how to generate IdP URI. 1674 Remove obsolete text about null cipher suites. 1676 Remove obsolete appendixes about older IdP systems 1678 Require support for ECDSA, PFS, and AEAD 1680 12.3. Changes since -10 1682 Update cipher suite profiles. 1684 Rework IdP interaction based on implementation experience in Firefox. 1686 12.4. Changes since -06 1688 Replaced RTCWEB and RTC-Web with WebRTC, except when referring to the 1689 IETF WG 1691 Forbade use in mixed content as discussed in Orlando. 1693 Added a requirement to surface NULL ciphers to the top-level. 1695 Tried to clarify SRTP versus DTLS-SRTP. 1697 Added a section on screen sharing permissions. 1699 Assorted editorial work. 1701 12.5. Changes since -05 1703 The following changes have been made since the -05 draft. 1705 o Response to comments from Richard Barnes 1707 o More explanation of the IdP security properties and the federation 1708 use case. 1710 o Editorial cleanup. 1712 12.6. Changes since -03 1714 Version -04 was a version control mistake. Please ignore. 1716 The following changes have been made since the -04 draft. 1718 o Move origin check from IdP to RP per discussion in YVR. 1720 o Clarified treatment of X.509-level identities. 1722 o Editorial cleanup. 1724 12.7. Changes since -03 1726 12.8. Changes since -02 1728 The following changes have been made since the -02 draft. 1730 o Forbid persistent HTTP permissions. 1732 o Clarified the text in S 5.4 to clearly refer to requirements on 1733 the API to provide functionality to the site. 1735 o Fold in the IETF portion of draft-rescorla-rtcweb-generic-idp 1737 o Retarget the continuing consent section to assume Binding Requests 1739 o Added some more privacy and linkage text in various places. 1741 o Editorial improvements 1743 13. References 1745 13.1. Normative References 1747 [FIPS186] National Institute of Standards and Technology (NIST), 1748 "Digital Signature Standard (DSS)", NIST PUB 186-4 , July 1749 2013. 1751 [I-D.ietf-mmusic-sdp-uks] 1752 Thomson, M. and E. Rescorla, "Unknown Key Share Attacks on 1753 uses of Transport Layer Security with the Session 1754 Description Protocol (SDP)", draft-ietf-mmusic-sdp-uks-02 1755 (work in progress), August 2018. 1757 [I-D.ietf-rtcweb-rtp-usage] 1758 Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time 1759 Communication (WebRTC): Media Transport and Use of RTP", 1760 draft-ietf-rtcweb-rtp-usage-26 (work in progress), March 1761 2016. 1763 [I-D.ietf-rtcweb-security] 1764 Rescorla, E., "Security Considerations for WebRTC", draft- 1765 ietf-rtcweb-security-10 (work in progress), January 2018. 1767 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1768 Requirement Levels", BCP 14, RFC 2119, 1769 DOI 10.17487/RFC2119, March 1997, 1770 . 1772 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1773 DOI 10.17487/RFC2818, May 2000, 1774 . 1776 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 1777 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 1778 RFC 3711, DOI 10.17487/RFC3711, March 2004, 1779 . 1781 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1782 Resource Identifier (URI): Generic Syntax", STD 66, 1783 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1784 . 1786 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 1787 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 1788 July 2006, . 1790 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 1791 Description Protocol (SDP) Security Descriptions for Media 1792 Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, 1793 . 1795 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 1796 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 1797 . 1799 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 1800 Specifications: ABNF", STD 68, RFC 5234, 1801 DOI 10.17487/RFC5234, January 2008, 1802 . 1804 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 1805 (ICE): A Protocol for Network Address Translator (NAT) 1806 Traversal for Offer/Answer Protocols", RFC 5245, 1807 DOI 10.17487/RFC5245, April 2010, 1808 . 1810 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1811 (TLS) Protocol Version 1.2", RFC 5246, 1812 DOI 10.17487/RFC5246, August 2008, 1813 . 1815 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework 1816 for Establishing a Secure Real-time Transport Protocol 1817 (SRTP) Security Context Using Datagram Transport Layer 1818 Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May 1819 2010, . 1821 [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer 1822 Security (DTLS) Extension to Establish Keys for the Secure 1823 Real-time Transport Protocol (SRTP)", RFC 5764, 1824 DOI 10.17487/RFC5764, May 2010, 1825 . 1827 [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known 1828 Uniform Resource Identifiers (URIs)", RFC 5785, 1829 DOI 10.17487/RFC5785, April 2010, 1830 . 1832 [RFC5890] Klensin, J., "Internationalized Domain Names for 1833 Applications (IDNA): Definitions and Document Framework", 1834 RFC 5890, DOI 10.17487/RFC5890, August 2010, 1835 . 1837 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 1838 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 1839 January 2012, . 1841 [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, 1842 DOI 10.17487/RFC6454, December 2011, 1843 . 1845 [RFC7022] Begen, A., Perkins, C., Wing, D., and E. Rescorla, 1846 "Guidelines for Choosing RTP Control Protocol (RTCP) 1847 Canonical Names (CNAMEs)", RFC 7022, DOI 10.17487/RFC7022, 1848 September 2013, . 1850 [RFC7675] Perumal, M., Wing, D., Ravindranath, R., Reddy, T., and M. 1851 Thomson, "Session Traversal Utilities for NAT (STUN) Usage 1852 for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675, 1853 October 2015, . 1855 [RFC8122] Lennox, J. and C. Holmberg, "Connection-Oriented Media 1856 Transport over the Transport Layer Security (TLS) Protocol 1857 in the Session Description Protocol (SDP)", RFC 8122, 1858 DOI 10.17487/RFC8122, March 2017, 1859 . 1861 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1862 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1863 May 2017, . 1865 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1866 Interchange Format", STD 90, RFC 8259, 1867 DOI 10.17487/RFC8259, December 2017, 1868 . 1870 [RFC8261] Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, 1871 "Datagram Transport Layer Security (DTLS) Encapsulation of 1872 SCTP Packets", RFC 8261, DOI 10.17487/RFC8261, November 1873 2017, . 1875 [webcrypto] 1876 Dahl, Sleevi, "Web Cryptography API", June 2013. 1878 Available at http://www.w3.org/TR/WebCryptoAPI/ 1880 [webrtc-api] 1881 Bergkvist, Burnett, Jennings, Narayanan, "WebRTC 1.0: 1882 Real-time Communication Between Browsers", October 2011. 1884 Available at http://dev.w3.org/2011/webrtc/editor/ 1885 webrtc.html 1887 13.2. Informative References 1889 [I-D.ietf-rtcweb-jsep] 1890 Uberti, J., Jennings, C., and E. Rescorla, "JavaScript 1891 Session Establishment Protocol", draft-ietf-rtcweb-jsep-24 1892 (work in progress), October 2017. 1894 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1895 A., Peterson, J., Sparks, R., Handley, M., and E. 1896 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1897 DOI 10.17487/RFC3261, June 2002, 1898 . 1900 [RFC5705] Rescorla, E., "Keying Material Exporters for Transport 1901 Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, 1902 March 2010, . 1904 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1905 DOI 10.17487/RFC6265, April 2011, 1906 . 1908 [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", 1909 RFC 6455, DOI 10.17487/RFC6455, December 2011, 1910 . 1912 [RFC6943] Thaler, D., Ed., "Issues in Identifier Comparison for 1913 Security Purposes", RFC 6943, DOI 10.17487/RFC6943, May 1914 2013, . 1916 [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme", 1917 RFC 7617, DOI 10.17487/RFC7617, September 2015, 1918 . 1920 [XmlHttpRequest] 1921 van Kesteren, A., "XMLHttpRequest Level 2", January 2012. 1923 Author's Address 1925 Eric Rescorla 1926 RTFM, Inc. 1927 2064 Edgewood Drive 1928 Palo Alto, CA 94303 1929 USA 1931 Phone: +1 650 678 2350 1932 Email: ekr@rtfm.com