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Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '0' on line 2342 -- Looks like a reference, but probably isn't: '1' on line 1553 -- Possible downref: Non-RFC (?) normative reference: ref. 'AES' ** Downref: Normative reference to an Informational RFC: RFC 8439 (ref. 'CHACHA') ** Downref: Normative reference to an Informational RFC: RFC 5869 (ref. 'HKDF') == Outdated reference: draft-ietf-quic-recovery has been published as RFC 9002 == Outdated reference: draft-ietf-quic-transport has been published as RFC 9000 -- Possible downref: Non-RFC (?) normative reference: ref. 'SHA' == Outdated reference: draft-ietf-tls-certificate-compression has been published as RFC 8879 == Outdated reference: A later version (-34) exists of draft-ietf-quic-http-32 Summary: 2 errors (**), 0 flaws (~~), 6 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 QUIC M. Thomson, Ed. 3 Internet-Draft Mozilla 4 Intended status: Standards Track S. Turner, Ed. 5 Expires: 23 April 2021 sn3rd 6 20 October 2020 8 Using TLS to Secure QUIC 9 draft-ietf-quic-tls-32 11 Abstract 13 This document describes how Transport Layer Security (TLS) is used to 14 secure QUIC. 16 Note to Readers 18 Discussion of this draft takes place on the QUIC working group 19 mailing list (quic@ietf.org), which is archived at 20 https://mailarchive.ietf.org/arch/search/?email_list=quic. 22 Working Group information can be found at https://github.com/quicwg; 23 source code and issues list for this draft can be found at 24 https://github.com/quicwg/base-drafts/labels/-tls. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on 23 April 2021. 43 Copyright Notice 45 Copyright (c) 2020 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 50 license-info) in effect on the date of publication of this document. 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. Code Components 53 extracted from this document must include Simplified BSD License text 54 as described in Section 4.e of the Trust Legal Provisions and are 55 provided without warranty as described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 60 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 4 61 2.1. TLS Overview . . . . . . . . . . . . . . . . . . . . . . 5 62 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 63 4. Carrying TLS Messages . . . . . . . . . . . . . . . . . . . . 8 64 4.1. Interface to TLS . . . . . . . . . . . . . . . . . . . . 9 65 4.1.1. Handshake Complete . . . . . . . . . . . . . . . . . 10 66 4.1.2. Handshake Confirmed . . . . . . . . . . . . . . . . . 10 67 4.1.3. Sending and Receiving Handshake Messages . . . . . . 10 68 4.1.4. Encryption Level Changes . . . . . . . . . . . . . . 12 69 4.1.5. TLS Interface Summary . . . . . . . . . . . . . . . . 14 70 4.2. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 15 71 4.3. ClientHello Size . . . . . . . . . . . . . . . . . . . . 15 72 4.4. Peer Authentication . . . . . . . . . . . . . . . . . . . 16 73 4.5. Session Resumption . . . . . . . . . . . . . . . . . . . 17 74 4.6. 0-RTT . . . . . . . . . . . . . . . . . . . . . . . . . . 17 75 4.6.1. Enabling 0-RTT . . . . . . . . . . . . . . . . . . . 18 76 4.6.2. Accepting and Rejecting 0-RTT . . . . . . . . . . . . 18 77 4.6.3. Validating 0-RTT Configuration . . . . . . . . . . . 19 78 4.7. HelloRetryRequest . . . . . . . . . . . . . . . . . . . . 19 79 4.8. TLS Errors . . . . . . . . . . . . . . . . . . . . . . . 19 80 4.9. Discarding Unused Keys . . . . . . . . . . . . . . . . . 20 81 4.9.1. Discarding Initial Keys . . . . . . . . . . . . . . . 20 82 4.9.2. Discarding Handshake Keys . . . . . . . . . . . . . . 21 83 4.9.3. Discarding 0-RTT Keys . . . . . . . . . . . . . . . . 21 84 5. Packet Protection . . . . . . . . . . . . . . . . . . . . . . 21 85 5.1. Packet Protection Keys . . . . . . . . . . . . . . . . . 22 86 5.2. Initial Secrets . . . . . . . . . . . . . . . . . . . . . 23 87 5.3. AEAD Usage . . . . . . . . . . . . . . . . . . . . . . . 24 88 5.4. Header Protection . . . . . . . . . . . . . . . . . . . . 25 89 5.4.1. Header Protection Application . . . . . . . . . . . . 26 90 5.4.2. Header Protection Sample . . . . . . . . . . . . . . 27 91 5.4.3. AES-Based Header Protection . . . . . . . . . . . . . 29 92 5.4.4. ChaCha20-Based Header Protection . . . . . . . . . . 29 93 5.5. Receiving Protected Packets . . . . . . . . . . . . . . . 30 94 5.6. Use of 0-RTT Keys . . . . . . . . . . . . . . . . . . . . 30 95 5.7. Receiving Out-of-Order Protected Packets . . . . . . . . 31 96 5.8. Retry Packet Integrity . . . . . . . . . . . . . . . . . 32 97 6. Key Update . . . . . . . . . . . . . . . . . . . . . . . . . 33 98 6.1. Initiating a Key Update . . . . . . . . . . . . . . . . . 34 99 6.2. Responding to a Key Update . . . . . . . . . . . . . . . 35 100 6.3. Timing of Receive Key Generation . . . . . . . . . . . . 36 101 6.4. Sending with Updated Keys . . . . . . . . . . . . . . . . 37 102 6.5. Receiving with Different Keys . . . . . . . . . . . . . . 37 103 6.6. Limits on AEAD Usage . . . . . . . . . . . . . . . . . . 38 104 6.7. Key Update Error Code . . . . . . . . . . . . . . . . . . 40 105 7. Security of Initial Messages . . . . . . . . . . . . . . . . 40 106 8. QUIC-Specific Adjustments to the TLS Handshake . . . . . . . 40 107 8.1. Protocol Negotiation . . . . . . . . . . . . . . . . . . 41 108 8.2. QUIC Transport Parameters Extension . . . . . . . . . . . 41 109 8.3. Removing the EndOfEarlyData Message . . . . . . . . . . . 42 110 8.4. Prohibit TLS Middlebox Compatibility Mode . . . . . . . . 42 111 9. Security Considerations . . . . . . . . . . . . . . . . . . . 43 112 9.1. Session Linkability . . . . . . . . . . . . . . . . . . . 43 113 9.2. Replay Attacks with 0-RTT . . . . . . . . . . . . . . . . 43 114 9.3. Packet Reflection Attack Mitigation . . . . . . . . . . . 44 115 9.4. Header Protection Analysis . . . . . . . . . . . . . . . 44 116 9.5. Header Protection Timing Side-Channels . . . . . . . . . 45 117 9.6. Key Diversity . . . . . . . . . . . . . . . . . . . . . . 46 118 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 119 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 46 120 11.1. Normative References . . . . . . . . . . . . . . . . . . 46 121 11.2. Informative References . . . . . . . . . . . . . . . . . 48 122 Appendix A. Sample Packet Protection . . . . . . . . . . . . . . 49 123 A.1. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . 49 124 A.2. Client Initial . . . . . . . . . . . . . . . . . . . . . 50 125 A.3. Server Initial . . . . . . . . . . . . . . . . . . . . . 52 126 A.4. Retry . . . . . . . . . . . . . . . . . . . . . . . . . . 53 127 A.5. ChaCha20-Poly1305 Short Header Packet . . . . . . . . . . 53 128 Appendix B. AEAD Algorithm Analysis . . . . . . . . . . . . . . 55 129 B.1. Analysis of AEAD_AES_128_GCM and AEAD_AES_256_GCM Usage 130 Limits . . . . . . . . . . . . . . . . . . . . . . . . . 56 131 B.1.1. Confidentiality Limit . . . . . . . . . . . . . . . . 56 132 B.1.2. Integrity Limit . . . . . . . . . . . . . . . . . . . 56 133 B.2. Analysis of AEAD_AES_128_CCM Usage Limits . . . . . . . . 57 134 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 58 135 C.1. Since draft-ietf-quic-tls-31 . . . . . . . . . . . . . . 58 136 C.2. Since draft-ietf-quic-tls-30 . . . . . . . . . . . . . . 58 137 C.3. Since draft-ietf-quic-tls-29 . . . . . . . . . . . . . . 58 138 C.4. Since draft-ietf-quic-tls-28 . . . . . . . . . . . . . . 58 139 C.5. Since draft-ietf-quic-tls-27 . . . . . . . . . . . . . . 59 140 C.6. Since draft-ietf-quic-tls-26 . . . . . . . . . . . . . . 59 141 C.7. Since draft-ietf-quic-tls-25 . . . . . . . . . . . . . . 59 142 C.8. Since draft-ietf-quic-tls-24 . . . . . . . . . . . . . . 59 143 C.9. Since draft-ietf-quic-tls-23 . . . . . . . . . . . . . . 59 144 C.10. Since draft-ietf-quic-tls-22 . . . . . . . . . . . . . . 59 145 C.11. Since draft-ietf-quic-tls-21 . . . . . . . . . . . . . . 59 146 C.12. Since draft-ietf-quic-tls-20 . . . . . . . . . . . . . . 60 147 C.13. Since draft-ietf-quic-tls-18 . . . . . . . . . . . . . . 60 148 C.14. Since draft-ietf-quic-tls-17 . . . . . . . . . . . . . . 60 149 C.15. Since draft-ietf-quic-tls-14 . . . . . . . . . . . . . . 60 150 C.16. Since draft-ietf-quic-tls-13 . . . . . . . . . . . . . . 60 151 C.17. Since draft-ietf-quic-tls-12 . . . . . . . . . . . . . . 61 152 C.18. Since draft-ietf-quic-tls-11 . . . . . . . . . . . . . . 61 153 C.19. Since draft-ietf-quic-tls-10 . . . . . . . . . . . . . . 61 154 C.20. Since draft-ietf-quic-tls-09 . . . . . . . . . . . . . . 61 155 C.21. Since draft-ietf-quic-tls-08 . . . . . . . . . . . . . . 61 156 C.22. Since draft-ietf-quic-tls-07 . . . . . . . . . . . . . . 61 157 C.23. Since draft-ietf-quic-tls-05 . . . . . . . . . . . . . . 61 158 C.24. Since draft-ietf-quic-tls-04 . . . . . . . . . . . . . . 62 159 C.25. Since draft-ietf-quic-tls-03 . . . . . . . . . . . . . . 62 160 C.26. Since draft-ietf-quic-tls-02 . . . . . . . . . . . . . . 62 161 C.27. Since draft-ietf-quic-tls-01 . . . . . . . . . . . . . . 62 162 C.28. Since draft-ietf-quic-tls-00 . . . . . . . . . . . . . . 62 163 C.29. Since draft-thomson-quic-tls-01 . . . . . . . . . . . . . 63 164 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 63 165 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 64 167 1. Introduction 169 This document describes how QUIC [QUIC-TRANSPORT] is secured using 170 TLS [TLS13]. 172 TLS 1.3 provides critical latency improvements for connection 173 establishment over previous versions. Absent packet loss, most new 174 connections can be established and secured within a single round 175 trip; on subsequent connections between the same client and server, 176 the client can often send application data immediately, that is, 177 using a zero round trip setup. 179 This document describes how TLS acts as a security component of QUIC. 181 2. Notational Conventions 183 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 184 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 185 "OPTIONAL" in this document are to be interpreted as described in 186 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 187 capitals, as shown here. 189 This document uses the terminology established in [QUIC-TRANSPORT]. 191 For brevity, the acronym TLS is used to refer to TLS 1.3, though a 192 newer version could be used; see Section 4.2. 194 2.1. TLS Overview 196 TLS provides two endpoints with a way to establish a means of 197 communication over an untrusted medium (that is, the Internet). TLS 198 enables authentication of peers and provides confidentiality and 199 integrity protection for messages that endpoints exchange. 201 Internally, TLS is a layered protocol, with the structure shown in 202 Figure 1. 204 +-------------+------------+--------------+---------+ 205 Handshake | | | Application | | 206 Layer | Handshake | Alerts | Data | ... | 207 | | | | | 208 +-------------+------------+--------------+---------+ 209 Record | | 210 Layer | Records | 211 | | 212 +---------------------------------------------------+ 214 Figure 1: TLS Layers 216 Each Handshake layer message (e.g., Handshake, Alerts, and 217 Application Data) is carried as a series of typed TLS records by the 218 Record layer. Records are individually cryptographically protected 219 and then transmitted over a reliable transport (typically TCP), which 220 provides sequencing and guaranteed delivery. 222 The TLS authenticated key exchange occurs between two endpoints: 223 client and server. The client initiates the exchange and the server 224 responds. If the key exchange completes successfully, both client 225 and server will agree on a secret. TLS supports both pre-shared key 226 (PSK) and Diffie-Hellman over either finite fields or elliptic curves 227 ((EC)DHE) key exchanges. PSK is the basis for Early Data (0-RTT); 228 the latter provides perfect forward secrecy (PFS) when the (EC)DHE 229 keys are destroyed. 231 After completing the TLS handshake, the client will have learned and 232 authenticated an identity for the server and the server is optionally 233 able to learn and authenticate an identity for the client. TLS 234 supports X.509 [RFC5280] certificate-based authentication for both 235 server and client. 237 The TLS key exchange is resistant to tampering by attackers and it 238 produces shared secrets that cannot be controlled by either 239 participating peer. 241 TLS provides two basic handshake modes of interest to QUIC: 243 * A full 1-RTT handshake, in which the client is able to send 244 Application Data after one round trip and the server immediately 245 responds after receiving the first handshake message from the 246 client. 248 * A 0-RTT handshake, in which the client uses information it has 249 previously learned about the server to send Application Data 250 immediately. This Application Data can be replayed by an attacker 251 so 0-RTT is not suitable for carrying instructions that might 252 initiate any non-idempotent action. 254 A simplified TLS handshake with 0-RTT application data is shown in 255 Figure 2. 257 Client Server 259 ClientHello 260 (0-RTT Application Data) --------> 261 ServerHello 262 {EncryptedExtensions} 263 {Finished} 264 <-------- [Application Data] 265 {Finished} --------> 267 [Application Data] <-------> [Application Data] 269 () Indicates messages protected by Early Data (0-RTT) Keys 270 {} Indicates messages protected using Handshake Keys 271 [] Indicates messages protected using Application Data 272 (1-RTT) Keys 274 Figure 2: TLS Handshake with 0-RTT 276 Figure 2 omits the EndOfEarlyData message, which is not used in QUIC; 277 see Section 8.3. Likewise, neither ChangeCipherSpec nor KeyUpdate 278 messages are used by QUIC. ChangeCipherSpec is redundant in TLS 1.3; 279 see Section 8.4. QUIC has its own key update mechanism; see 280 Section 6. 282 Data is protected using a number of encryption levels: 284 * Initial Keys 285 * Early Data (0-RTT) Keys 287 * Handshake Keys 289 * Application Data (1-RTT) Keys 291 Application Data may appear only in the Early Data and Application 292 Data levels. Handshake and Alert messages may appear in any level. 294 The 0-RTT handshake is only possible if the client and server have 295 previously communicated. In the 1-RTT handshake, the client is 296 unable to send protected Application Data until it has received all 297 of the Handshake messages sent by the server. 299 3. Protocol Overview 301 QUIC [QUIC-TRANSPORT] assumes responsibility for the confidentiality 302 and integrity protection of packets. For this it uses keys derived 303 from a TLS handshake [TLS13], but instead of carrying TLS records 304 over QUIC (as with TCP), TLS Handshake and Alert messages are carried 305 directly over the QUIC transport, which takes over the 306 responsibilities of the TLS record layer, as shown in Figure 3. 308 +--------------+--------------+ +-------------+ 309 | TLS | TLS | | QUIC | 310 | Handshake | Alerts | | Applications| 311 | | | | (h3, etc.) | 312 +--------------+--------------+-+-------------+ 313 | | 314 | QUIC Transport | 315 | (streams, reliability, congestion, etc.) | 316 | | 317 +---------------------------------------------+ 318 | | 319 | QUIC Packet Protection | 320 | | 321 +---------------------------------------------+ 323 Figure 3: QUIC Layers 325 QUIC also relies on TLS for authentication and negotiation of 326 parameters that are critical to security and performance. 328 Rather than a strict layering, these two protocols cooperate: QUIC 329 uses the TLS handshake; TLS uses the reliability, ordered delivery, 330 and record layer provided by QUIC. 332 At a high level, there are two main interactions between the TLS and 333 QUIC components: 335 * The TLS component sends and receives messages via the QUIC 336 component, with QUIC providing a reliable stream abstraction to 337 TLS. 339 * The TLS component provides a series of updates to the QUIC 340 component, including (a) new packet protection keys to install (b) 341 state changes such as handshake completion, the server 342 certificate, etc. 344 Figure 4 shows these interactions in more detail, with the QUIC 345 packet protection being called out specially. 347 +------------+ +------------+ 348 | |<---- Handshake Messages ----->| | 349 | |<- Validate 0-RTT parameters ->| | 350 | |<--------- 0-RTT Keys ---------| | 351 | QUIC |<------- Handshake Keys -------| TLS | 352 | |<--------- 1-RTT Keys ---------| | 353 | |<------- Handshake Done -------| | 354 +------------+ +------------+ 355 | ^ 356 | Protect | Protected 357 v | Packet 358 +------------+ 359 | QUIC | 360 | Packet | 361 | Protection | 362 +------------+ 364 Figure 4: QUIC and TLS Interactions 366 Unlike TLS over TCP, QUIC applications that want to send data do not 367 send it through TLS "application_data" records. Rather, they send it 368 as QUIC STREAM frames or other frame types, which are then carried in 369 QUIC packets. 371 4. Carrying TLS Messages 373 QUIC carries TLS handshake data in CRYPTO frames, each of which 374 consists of a contiguous block of handshake data identified by an 375 offset and length. Those frames are packaged into QUIC packets and 376 encrypted under the current TLS encryption level. As with TLS over 377 TCP, once TLS handshake data has been delivered to QUIC, it is QUIC's 378 responsibility to deliver it reliably. Each chunk of data that is 379 produced by TLS is associated with the set of keys that TLS is 380 currently using. If QUIC needs to retransmit that data, it MUST use 381 the same keys even if TLS has already updated to newer keys. 383 One important difference between TLS records (used with TCP) and QUIC 384 CRYPTO frames is that in QUIC multiple frames may appear in the same 385 QUIC packet as long as they are associated with the same packet 386 number space. For instance, an endpoint can bundle a Handshake 387 message and an ACK for some Handshake data into the same packet. 388 Some frames are prohibited in different packet number spaces; see 389 Section 12.5 of [QUIC-TRANSPORT]. 391 Because packets could be reordered on the wire, QUIC uses the packet 392 type to indicate which keys were used to protect a given packet, as 393 shown in Table 1. When packets of different types need to be sent, 394 endpoints SHOULD use coalesced packets to send them in the same UDP 395 datagram. 397 +=====================+=================+==================+ 398 | Packet Type | Encryption Keys | PN Space | 399 +=====================+=================+==================+ 400 | Initial | Initial secrets | Initial | 401 +---------------------+-----------------+------------------+ 402 | 0-RTT Protected | 0-RTT | Application data | 403 +---------------------+-----------------+------------------+ 404 | Handshake | Handshake | Handshake | 405 +---------------------+-----------------+------------------+ 406 | Retry | Retry | N/A | 407 +---------------------+-----------------+------------------+ 408 | Version Negotiation | N/A | N/A | 409 +---------------------+-----------------+------------------+ 410 | Short Header | 1-RTT | Application data | 411 +---------------------+-----------------+------------------+ 413 Table 1: Encryption Keys by Packet Type 415 Section 17 of [QUIC-TRANSPORT] shows how packets at the various 416 encryption levels fit into the handshake process. 418 4.1. Interface to TLS 420 As shown in Figure 4, the interface from QUIC to TLS consists of four 421 primary functions: 423 * Sending and receiving handshake messages 425 * Processing stored transport and application state from a resumed 426 session and determining if it is valid to accept early data 428 * Rekeying (both transmit and receive) 430 * Handshake state updates 432 Additional functions might be needed to configure TLS. 434 4.1.1. Handshake Complete 436 In this document, the TLS handshake is considered complete when the 437 TLS stack has reported that the handshake is complete. This happens 438 when the TLS stack has both sent a Finished message and verified the 439 peer's Finished message. Verifying the peer's Finished provides the 440 endpoints with an assurance that previous handshake messages have not 441 been modified. Note that the handshake does not complete at both 442 endpoints simultaneously. Consequently, any requirement that is 443 based on the completion of the handshake depends on the perspective 444 of the endpoint in question. 446 4.1.2. Handshake Confirmed 448 In this document, the TLS handshake is considered confirmed at the 449 server when the handshake completes. At the client, the handshake is 450 considered confirmed when a HANDSHAKE_DONE frame is received. 452 A client MAY consider the handshake to be confirmed when it receives 453 an acknowledgement for a 1-RTT packet. This can be implemented by 454 recording the lowest packet number sent with 1-RTT keys, and 455 comparing it to the Largest Acknowledged field in any received 1-RTT 456 ACK frame: once the latter is greater than or equal to the former, 457 the handshake is confirmed. 459 4.1.3. Sending and Receiving Handshake Messages 461 In order to drive the handshake, TLS depends on being able to send 462 and receive handshake messages. There are two basic functions on 463 this interface: one where QUIC requests handshake messages and one 464 where QUIC provides bytes that comprise handshake messages. 466 Before starting the handshake QUIC provides TLS with the transport 467 parameters (see Section 8.2) that it wishes to carry. 469 A QUIC client starts TLS by requesting TLS handshake bytes from TLS. 470 The client acquires handshake bytes before sending its first packet. 471 A QUIC server starts the process by providing TLS with the client's 472 handshake bytes. 474 At any time, the TLS stack at an endpoint will have a current sending 475 encryption level and receiving encryption level. Encryption levels 476 determine the packet type and keys that are used for protecting data. 478 Each encryption level is associated with a different sequence of 479 bytes, which is reliably transmitted to the peer in CRYPTO frames. 480 When TLS provides handshake bytes to be sent, they are appended to 481 the handshake bytes for the current encryption level. The encryption 482 level then determines the type of packet that the resulting CRYPTO 483 frame is carried in; see Table 1. 485 Four encryption levels are used, producing keys for Initial, 0-RTT, 486 Handshake, and 1-RTT packets. CRYPTO frames are carried in just 487 three of these levels, omitting the 0-RTT level. These four levels 488 correspond to three packet number spaces: Initial and Handshake 489 encrypted packets use their own separate spaces; 0-RTT and 1-RTT 490 packets use the application data packet number space. 492 QUIC takes the unprotected content of TLS handshake records as the 493 content of CRYPTO frames. TLS record protection is not used by QUIC. 494 QUIC assembles CRYPTO frames into QUIC packets, which are protected 495 using QUIC packet protection. 497 QUIC is only capable of conveying TLS handshake records in CRYPTO 498 frames. TLS alerts are turned into QUIC CONNECTION_CLOSE error 499 codes; see Section 4.8. TLS application data and other message types 500 cannot be carried by QUIC at any encryption level; it is an error if 501 they are received from the TLS stack. 503 When an endpoint receives a QUIC packet containing a CRYPTO frame 504 from the network, it proceeds as follows: 506 * If the packet uses the current TLS receiving encryption level, 507 sequence the data into the input flow as usual. As with STREAM 508 frames, the offset is used to find the proper location in the data 509 sequence. If the result of this process is that new data is 510 available, then it is delivered to TLS in order. 512 * If the packet is from a previously installed encryption level, it 513 MUST NOT contain data that extends past the end of previously 514 received data in that flow. Implementations MUST treat any 515 violations of this requirement as a connection error of type 516 PROTOCOL_VIOLATION. 518 * If the packet is from a new encryption level, it is saved for 519 later processing by TLS. Once TLS moves to receiving from this 520 encryption level, saved data can be provided to TLS. When TLS 521 provides keys for a higher encryption level, if there is data from 522 a previous encryption level that TLS has not consumed, this MUST 523 be treated as a connection error of type PROTOCOL_VIOLATION. 525 Each time that TLS is provided with new data, new handshake bytes are 526 requested from TLS. TLS might not provide any bytes if the handshake 527 messages it has received are incomplete or it has no data to send. 529 The content of CRYPTO frames might either be processed incrementally 530 by TLS or buffered until complete messages or flights are available. 531 TLS is responsible for buffering handshake bytes that have arrived in 532 order. QUIC is responsible for buffering handshake bytes that arrive 533 out of order or for encryption levels that are not yet ready. QUIC 534 does not provide any means of flow control for CRYPTO frames; see 535 Section 7.5 of [QUIC-TRANSPORT]. 537 Once the TLS handshake is complete, this is indicated to QUIC along 538 with any final handshake bytes that TLS needs to send. TLS also 539 provides QUIC with the transport parameters that the peer advertised 540 during the handshake. 542 Once the handshake is complete, TLS becomes passive. TLS can still 543 receive data from its peer and respond in kind, but it will not need 544 to send more data unless specifically requested - either by an 545 application or QUIC. One reason to send data is that the server 546 might wish to provide additional or updated session tickets to a 547 client. 549 When the handshake is complete, QUIC only needs to provide TLS with 550 any data that arrives in CRYPTO streams. In the same way that is 551 done during the handshake, new data is requested from TLS after 552 providing received data. 554 4.1.4. Encryption Level Changes 556 As keys at a given encryption level become available to TLS, TLS 557 indicates to QUIC that reading or writing keys at that encryption 558 level are available. 560 The availability of new keys is always a result of providing inputs 561 to TLS. TLS only provides new keys after being initialized (by a 562 client) or when provided with new handshake data. 564 However, a TLS implementation could perform some of its processing 565 asynchronously. In particular, the process of validating a 566 certificate can take some time. While waiting for TLS processing to 567 complete, an endpoint SHOULD buffer received packets if they might be 568 processed using keys that aren't yet available. These packets can be 569 processed once keys are provided by TLS. An endpoint SHOULD continue 570 to respond to packets that can be processed during this time. 572 After processing inputs, TLS might produce handshake bytes, keys for 573 new encryption levels, or both. 575 TLS provides QUIC with three items as a new encryption level becomes 576 available: 578 * A secret 580 * An Authenticated Encryption with Associated Data (AEAD) function 582 * A Key Derivation Function (KDF) 584 These values are based on the values that TLS negotiates and are used 585 by QUIC to generate packet and header protection keys; see Section 5 586 and Section 5.4. 588 If 0-RTT is possible, it is ready after the client sends a TLS 589 ClientHello message or the server receives that message. After 590 providing a QUIC client with the first handshake bytes, the TLS stack 591 might signal the change to 0-RTT keys. On the server, after 592 receiving handshake bytes that contain a ClientHello message, a TLS 593 server might signal that 0-RTT keys are available. 595 Although TLS only uses one encryption level at a time, QUIC may use 596 more than one level. For instance, after sending its Finished 597 message (using a CRYPTO frame at the Handshake encryption level) an 598 endpoint can send STREAM data (in 1-RTT encryption). If the Finished 599 message is lost, the endpoint uses the Handshake encryption level to 600 retransmit the lost message. Reordering or loss of packets can mean 601 that QUIC will need to handle packets at multiple encryption levels. 602 During the handshake, this means potentially handling packets at 603 higher and lower encryption levels than the current encryption level 604 used by TLS. 606 In particular, server implementations need to be able to read packets 607 at the Handshake encryption level at the same time as the 0-RTT 608 encryption level. A client could interleave ACK frames that are 609 protected with Handshake keys with 0-RTT data and the server needs to 610 process those acknowledgments in order to detect lost Handshake 611 packets. 613 QUIC also needs access to keys that might not ordinarily be available 614 to a TLS implementation. For instance, a client might need to 615 acknowledge Handshake packets before it is ready to send CRYPTO 616 frames at that encryption level. TLS therefore needs to provide keys 617 to QUIC before it might produce them for its own use. 619 4.1.5. TLS Interface Summary 621 Figure 5 summarizes the exchange between QUIC and TLS for both client 622 and server. Solid arrows indicate packets that carry handshake data; 623 dashed arrows show where application data can be sent. Each arrow is 624 tagged with the encryption level used for that transmission. 626 Client Server 627 ====== ====== 629 Get Handshake 630 Initial -------------> 631 Install tx 0-RTT Keys 632 0-RTT - - - - - - - -> 634 Handshake Received 635 Get Handshake 636 <------------- Initial 637 Install rx 0-RTT keys 638 Install Handshake keys 639 Get Handshake 640 <----------- Handshake 641 Install tx 1-RTT keys 642 <- - - - - - - - 1-RTT 644 Handshake Received (Initial) 645 Install Handshake keys 646 Handshake Received (Handshake) 647 Get Handshake 648 Handshake -----------> 649 Handshake Complete 650 Install 1-RTT keys 651 1-RTT - - - - - - - -> 653 Handshake Received 654 Handshake Complete 655 Install rx 1-RTT keys 657 Figure 5: Interaction Summary between QUIC and TLS 659 Figure 5 shows the multiple packets that form a single "flight" of 660 messages being processed individually, to show what incoming messages 661 trigger different actions. New handshake messages are requested 662 after incoming packets have been processed. This process varies 663 based on the structure of endpoint implementations and the order in 664 which packets arrive; this is intended to illustrate the steps 665 involved in a single handshake exchange. 667 4.2. TLS Version 669 This document describes how TLS 1.3 [TLS13] is used with QUIC. 671 In practice, the TLS handshake will negotiate a version of TLS to 672 use. This could result in a newer version of TLS than 1.3 being 673 negotiated if both endpoints support that version. This is 674 acceptable provided that the features of TLS 1.3 that are used by 675 QUIC are supported by the newer version. 677 Clients MUST NOT offer TLS versions older than 1.3. A badly 678 configured TLS implementation could negotiate TLS 1.2 or another 679 older version of TLS. An endpoint MUST terminate the connection if a 680 version of TLS older than 1.3 is negotiated. 682 4.3. ClientHello Size 684 The first Initial packet from a client contains the start or all of 685 its first cryptographic handshake message, which for TLS is the 686 ClientHello. Servers might need to parse the entire ClientHello 687 (e.g., to access extensions such as Server Name Identification (SNI) 688 or Application Layer Protocol Negotiation (ALPN)) in order to decide 689 whether to accept the new incoming QUIC connection. If the 690 ClientHello spans multiple Initial packets, such servers would need 691 to buffer the first received fragments, which could consume excessive 692 resources if the client's address has not yet been validated. To 693 avoid this, servers MAY use the Retry feature (see Section 8.1 of 694 [QUIC-TRANSPORT]) to only buffer partial ClientHello messages from 695 clients with a validated address. 697 QUIC packet and framing add at least 36 bytes of overhead to the 698 ClientHello message. That overhead increases if the client chooses a 699 source connection ID longer than zero bytes. Overheads also do not 700 include the token or a destination connection ID longer than 8 bytes, 701 both of which might be required if a server sends a Retry packet. 703 A typical TLS ClientHello can easily fit into a 1200-byte packet. 704 However, in addition to the overheads added by QUIC, there are 705 several variables that could cause this limit to be exceeded. Large 706 session tickets, multiple or large key shares, and long lists of 707 supported ciphers, signature algorithms, versions, QUIC transport 708 parameters, and other negotiable parameters and extensions could 709 cause this message to grow. 711 For servers, in addition to connection IDs and tokens, the size of 712 TLS session tickets can have an effect on a client's ability to 713 connect efficiently. Minimizing the size of these values increases 714 the probability that clients can use them and still fit their 715 ClientHello message in their first Initial packet. 717 The TLS implementation does not need to ensure that the ClientHello 718 is sufficiently large. QUIC PADDING frames are added to increase the 719 size of the packet as necessary. 721 4.4. Peer Authentication 723 The requirements for authentication depend on the application 724 protocol that is in use. TLS provides server authentication and 725 permits the server to request client authentication. 727 A client MUST authenticate the identity of the server. This 728 typically involves verification that the identity of the server is 729 included in a certificate and that the certificate is issued by a 730 trusted entity (see for example [RFC2818]). 732 Note: Where servers provide certificates for authentication, the 733 size of the certificate chain can consume a large number of bytes. 734 Controlling the size of certificate chains is critical to 735 performance in QUIC as servers are limited to sending 3 bytes for 736 every byte received prior to validating the client address; see 737 Section 8.1 of [QUIC-TRANSPORT]. The size of a certificate chain 738 can be managed by limiting the number of names or extensions; 739 using keys with small public key representations, like ECDSA; or 740 by using certificate compression [COMPRESS]. 742 A server MAY request that the client authenticate during the 743 handshake. A server MAY refuse a connection if the client is unable 744 to authenticate when requested. The requirements for client 745 authentication vary based on application protocol and deployment. 747 A server MUST NOT use post-handshake client authentication (as 748 defined in Section 4.6.2 of [TLS13]), because the multiplexing 749 offered by QUIC prevents clients from correlating the certificate 750 request with the application-level event that triggered it (see 751 [HTTP2-TLS13]). More specifically, servers MUST NOT send post- 752 handshake TLS CertificateRequest messages and clients MUST treat 753 receipt of such messages as a connection error of type 754 PROTOCOL_VIOLATION. 756 4.5. Session Resumption 758 QUIC can use the session resumption feature of TLS 1.3. It does this 759 by carrying NewSessionTicket messages in CRYPTO frames after the 760 handshake is complete. Session resumption is the basis of 0-RTT, but 761 can be used without also enabling 0-RTT. 763 Endpoints that use session resumption might need to remember some 764 information about the current connection when creating a resumed 765 connection. TLS requires that some information be retained; see 766 Section 4.6.1 of [TLS13]. QUIC itself does not depend on any state 767 being retained when resuming a connection, unless 0-RTT is also used; 768 see Section 4.6.1 and Section 7.4.1 of [QUIC-TRANSPORT]. Application 769 protocols could depend on state that is retained between resumed 770 connections. 772 Clients can store any state required for resumption along with the 773 session ticket. Servers can use the session ticket to help carry 774 state. 776 Session resumption allows servers to link activity on the original 777 connection with the resumed connection, which might be a privacy 778 issue for clients. Clients can choose not to enable resumption to 779 avoid creating this correlation. Clients SHOULD NOT reuse tickets as 780 that allows entities other than the server to correlate connections; 781 see Section C.4 of [TLS13]. 783 4.6. 0-RTT 785 The 0-RTT feature in QUIC allows a client to send application data 786 before the handshake is complete. This is made possible by reusing 787 negotiated parameters from a previous connection. To enable this, 788 0-RTT depends on the client remembering critical parameters and 789 providing the server with a TLS session ticket that allows the server 790 to recover the same information. 792 This information includes parameters that determine TLS state, as 793 governed by [TLS13], QUIC transport parameters, the chosen 794 application protocol, and any information the application protocol 795 might need; see Section 4.6.3. This information determines how 0-RTT 796 packets and their contents are formed. 798 To ensure that the same information is available to both endpoints, 799 all information used to establish 0-RTT comes from the same 800 connection. Endpoints cannot selectively disregard information that 801 might alter the sending or processing of 0-RTT. 803 [TLS13] sets a limit of 7 days on the time between the original 804 connection and any attempt to use 0-RTT. There are other constraints 805 on 0-RTT usage, notably those caused by the potential exposure to 806 replay attack; see Section 9.2. 808 4.6.1. Enabling 0-RTT 810 To communicate their willingness to process 0-RTT data, servers send 811 a NewSessionTicket message that contains the early_data extension 812 with a max_early_data_size of 0xffffffff. The TLS 813 max_early_data_size parameter is not used in QUIC. The amount of 814 data that the client can send in 0-RTT is controlled by the 815 initial_max_data transport parameter supplied by the server. 817 Servers MUST NOT send the early_data extension with a 818 max_early_data_size field set to any value other than 0xffffffff. A 819 client MUST treat receipt of a NewSessionTicket that contains an 820 early_data extension with any other value as a connection error of 821 type PROTOCOL_VIOLATION. 823 A client that wishes to send 0-RTT packets uses the early_data 824 extension in the ClientHello message of a subsequent handshake; see 825 Section 4.2.10 of [TLS13]. It then sends application data in 0-RTT 826 packets. 828 A client that attempts 0-RTT might also provide an address validation 829 token if the server has sent a NEW_TOKEN frame; see Section 8.1 of 830 [QUIC-TRANSPORT]. 832 4.6.2. Accepting and Rejecting 0-RTT 834 A server accepts 0-RTT by sending an early_data extension in the 835 EncryptedExtensions (see Section 4.2.10 of [TLS13]). The server then 836 processes and acknowledges the 0-RTT packets that it receives. 838 A server rejects 0-RTT by sending the EncryptedExtensions without an 839 early_data extension. A server will always reject 0-RTT if it sends 840 a TLS HelloRetryRequest. When rejecting 0-RTT, a server MUST NOT 841 process any 0-RTT packets, even if it could. When 0-RTT was 842 rejected, a client SHOULD treat receipt of an acknowledgement for a 843 0-RTT packet as a connection error of type PROTOCOL_VIOLATION, if it 844 is able to detect the condition. 846 When 0-RTT is rejected, all connection characteristics that the 847 client assumed might be incorrect. This includes the choice of 848 application protocol, transport parameters, and any application 849 configuration. The client therefore MUST reset the state of all 850 streams, including application state bound to those streams. 852 A client MAY reattempt 0-RTT if it receives a Retry or Version 853 Negotiation packet. These packets do not signify rejection of 0-RTT. 855 4.6.3. Validating 0-RTT Configuration 857 When a server receives a ClientHello with the early_data extension, 858 it has to decide whether to accept or reject early data from the 859 client. Some of this decision is made by the TLS stack (e.g., 860 checking that the cipher suite being resumed was included in the 861 ClientHello; see Section 4.2.10 of [TLS13]). Even when the TLS stack 862 has no reason to reject early data, the QUIC stack or the application 863 protocol using QUIC might reject early data because the configuration 864 of the transport or application associated with the resumed session 865 is not compatible with the server's current configuration. 867 QUIC requires additional transport state to be associated with a 868 0-RTT session ticket. One common way to implement this is using 869 stateless session tickets and storing this state in the session 870 ticket. Application protocols that use QUIC might have similar 871 requirements regarding associating or storing state. This associated 872 state is used for deciding whether early data must be rejected. For 873 example, HTTP/3 ([QUIC-HTTP]) settings determine how early data from 874 the client is interpreted. Other applications using QUIC could have 875 different requirements for determining whether to accept or reject 876 early data. 878 4.7. HelloRetryRequest 880 The HelloRetryRequest message (see Section 4.1.4 of [TLS13]) can be 881 used to request that a client provide new information, such as a key 882 share, or to validate some characteristic of the client. From the 883 perspective of QUIC, HelloRetryRequest is not differentiated from 884 other cryptographic handshake messages that are carried in Initial 885 packets. Although it is in principle possible to use this feature 886 for address verification, QUIC implementations SHOULD instead use the 887 Retry feature; see Section 8.1 of [QUIC-TRANSPORT]. 889 4.8. TLS Errors 891 If TLS experiences an error, it generates an appropriate alert as 892 defined in Section 6 of [TLS13]. 894 A TLS alert is converted into a QUIC connection error. The alert 895 description is added to 0x100 to produce a QUIC error code from the 896 range reserved for CRYPTO_ERROR. The resulting value is sent in a 897 QUIC CONNECTION_CLOSE frame of type 0x1c. 899 The alert level of all TLS alerts is "fatal"; a TLS stack MUST NOT 900 generate alerts at the "warning" level. 902 QUIC permits the use of a generic code in place of a specific error 903 code; see Section 11 of [QUIC-TRANSPORT]. For TLS alerts, this 904 includes replacing any alert with a generic alert, such as 905 handshake_failure (0x128 in QUIC). Endpoints MAY use a generic error 906 code to avoid possibly exposing confidential information. 908 4.9. Discarding Unused Keys 910 After QUIC moves to a new encryption level, packet protection keys 911 for previous encryption levels can be discarded. This occurs several 912 times during the handshake, as well as when keys are updated; see 913 Section 6. 915 Packet protection keys are not discarded immediately when new keys 916 are available. If packets from a lower encryption level contain 917 CRYPTO frames, frames that retransmit that data MUST be sent at the 918 same encryption level. Similarly, an endpoint generates 919 acknowledgements for packets at the same encryption level as the 920 packet being acknowledged. Thus, it is possible that keys for a 921 lower encryption level are needed for a short time after keys for a 922 newer encryption level are available. 924 An endpoint cannot discard keys for a given encryption level unless 925 it has both received and acknowledged all CRYPTO frames for that 926 encryption level and when all CRYPTO frames for that encryption level 927 have been acknowledged by its peer. However, this does not guarantee 928 that no further packets will need to be received or sent at that 929 encryption level because a peer might not have received all the 930 acknowledgements necessary to reach the same state. 932 Though an endpoint might retain older keys, new data MUST be sent at 933 the highest currently-available encryption level. Only ACK frames 934 and retransmissions of data in CRYPTO frames are sent at a previous 935 encryption level. These packets MAY also include PADDING frames. 937 4.9.1. Discarding Initial Keys 939 Packets protected with Initial secrets (Section 5.2) are not 940 authenticated, meaning that an attacker could spoof packets with the 941 intent to disrupt a connection. To limit these attacks, Initial 942 packet protection keys are discarded more aggressively than other 943 keys. 945 The successful use of Handshake packets indicates that no more 946 Initial packets need to be exchanged, as these keys can only be 947 produced after receiving all CRYPTO frames from Initial packets. 948 Thus, a client MUST discard Initial keys when it first sends a 949 Handshake packet and a server MUST discard Initial keys when it first 950 successfully processes a Handshake packet. Endpoints MUST NOT send 951 Initial packets after this point. 953 This results in abandoning loss recovery state for the Initial 954 encryption level and ignoring any outstanding Initial packets. 956 4.9.2. Discarding Handshake Keys 958 An endpoint MUST discard its handshake keys when the TLS handshake is 959 confirmed (Section 4.1.2). The server MUST send a HANDSHAKE_DONE 960 frame as soon as it completes the handshake. 962 4.9.3. Discarding 0-RTT Keys 964 0-RTT and 1-RTT packets share the same packet number space, and 965 clients do not send 0-RTT packets after sending a 1-RTT packet 966 (Section 5.6). 968 Therefore, a client SHOULD discard 0-RTT keys as soon as it installs 969 1-RTT keys, since they have no use after that moment. 971 Additionally, a server MAY discard 0-RTT keys as soon as it receives 972 a 1-RTT packet. However, due to packet reordering, a 0-RTT packet 973 could arrive after a 1-RTT packet. Servers MAY temporarily retain 974 0-RTT keys to allow decrypting reordered packets without requiring 975 their contents to be retransmitted with 1-RTT keys. After receiving 976 a 1-RTT packet, servers MUST discard 0-RTT keys within a short time; 977 the RECOMMENDED time period is three times the Probe Timeout (PTO, 978 see [QUIC-RECOVERY]). A server MAY discard 0-RTT keys earlier if it 979 determines that it has received all 0-RTT packets, which can be done 980 by keeping track of missing packet numbers. 982 5. Packet Protection 984 As with TLS over TCP, QUIC protects packets with keys derived from 985 the TLS handshake, using the AEAD algorithm [AEAD] negotiated by TLS. 987 QUIC packets have varying protections depending on their type: 989 * Version Negotiation packets have no cryptographic protection. 991 * Retry packets use AEAD_AES_128_GCM to provide protection against 992 accidental modification or insertion by off-path adversaries; see 993 Section 5.8. 995 * Initial packets use AEAD_AES_128_GCM with keys derived from the 996 Destination Connection ID field of the first Initial packet sent 997 by the client; see Section 5.2. 999 * All other packets have strong cryptographic protections for 1000 confidentiality and integrity, using keys and algorithms 1001 negotiated by TLS. 1003 This section describes how packet protection is applied to Handshake 1004 packets, 0-RTT packets, and 1-RTT packets. The same packet 1005 protection process is applied to Initial packets. However, as it is 1006 trivial to determine the keys used for Initial packets, these packets 1007 are not considered to have confidentiality or integrity protection. 1008 Retry packets use a fixed key and so similarly lack confidentiality 1009 and integrity protection. 1011 5.1. Packet Protection Keys 1013 QUIC derives packet protection keys in the same way that TLS derives 1014 record protection keys. 1016 Each encryption level has separate secret values for protection of 1017 packets sent in each direction. These traffic secrets are derived by 1018 TLS (see Section 7.1 of [TLS13]) and are used by QUIC for all 1019 encryption levels except the Initial encryption level. The secrets 1020 for the Initial encryption level are computed based on the client's 1021 initial Destination Connection ID, as described in Section 5.2. 1023 The keys used for packet protection are computed from the TLS secrets 1024 using the KDF provided by TLS. In TLS 1.3, the HKDF-Expand-Label 1025 function described in Section 7.1 of [TLS13] is used, using the hash 1026 function from the negotiated cipher suite. Note that labels, which 1027 are described using strings, are encoded as bytes using ASCII [ASCII] 1028 without quotes or any trailing NUL byte. Other versions of TLS MUST 1029 provide a similar function in order to be used with QUIC. 1031 The current encryption level secret and the label "quic key" are 1032 input to the KDF to produce the AEAD key; the label "quic iv" is used 1033 to derive the Initialization Vector (IV); see Section 5.3. The 1034 header protection key uses the "quic hp" label; see Section 5.4. 1035 Using these labels provides key separation between QUIC and TLS; see 1036 Section 9.6. 1038 The KDF used for initial secrets is always the HKDF-Expand-Label 1039 function from TLS 1.3; see Section 5.2. 1041 5.2. Initial Secrets 1043 Initial packets apply the packet protection process, but use a secret 1044 derived from the Destination Connection ID field from the client's 1045 first Initial packet. 1047 This secret is determined by using HKDF-Extract (see Section 2.2 of 1048 [HKDF]) with a salt of 0xafbfec289993d24c9e9786f19c6111e04390a899 and 1049 a IKM of the Destination Connection ID field. This produces an 1050 intermediate pseudorandom key (PRK) that is used to derive two 1051 separate secrets for sending and receiving. 1053 The secret used by clients to construct Initial packets uses the PRK 1054 and the label "client in" as input to the HKDF-Expand-Label function 1055 from TLS [TLS13] to produce a 32-byte secret. Packets constructed by 1056 the server use the same process with the label "server in". The hash 1057 function for HKDF when deriving initial secrets and keys is SHA-256 1058 [SHA]. 1060 This process in pseudocode is: 1062 initial_salt = 0xafbfec289993d24c9e9786f19c6111e04390a899 1063 initial_secret = HKDF-Extract(initial_salt, 1064 client_dst_connection_id) 1066 client_initial_secret = HKDF-Expand-Label(initial_secret, 1067 "client in", "", 1068 Hash.length) 1069 server_initial_secret = HKDF-Expand-Label(initial_secret, 1070 "server in", "", 1071 Hash.length) 1073 The connection ID used with HKDF-Expand-Label is the Destination 1074 Connection ID in the Initial packet sent by the client. This will be 1075 a randomly-selected value unless the client creates the Initial 1076 packet after receiving a Retry packet, where the Destination 1077 Connection ID is selected by the server. 1079 Future versions of QUIC SHOULD generate a new salt value, thus 1080 ensuring that the keys are different for each version of QUIC. This 1081 prevents a middlebox that recognizes only one version of QUIC from 1082 seeing or modifying the contents of packets from future versions. 1084 The HKDF-Expand-Label function defined in TLS 1.3 MUST be used for 1085 Initial packets even where the TLS versions offered do not include 1086 TLS 1.3. 1088 The secrets used for constructing Initial packets change when a 1089 server sends a Retry packet to use the connection ID value selected 1090 by the server. The secrets do not change when a client changes the 1091 Destination Connection ID it uses in response to an Initial packet 1092 from the server. 1094 Note: The Destination Connection ID field could be any length up to 1095 20 bytes, including zero length if the server sends a Retry packet 1096 with a zero-length Source Connection ID field. After a Retry, the 1097 Initial keys provide the client no assurance that the server 1098 received its packet, so the client has to rely on the exchange 1099 that included the Retry packet to validate the server address; see 1100 Section 8.1 of [QUIC-TRANSPORT]. 1102 Appendix A contains sample Initial packets. 1104 5.3. AEAD Usage 1106 The Authenticated Encryption with Associated Data (AEAD; see [AEAD]) 1107 function used for QUIC packet protection is the AEAD that is 1108 negotiated for use with the TLS connection. For example, if TLS is 1109 using the TLS_AES_128_GCM_SHA256 cipher suite, the AEAD_AES_128_GCM 1110 function is used. 1112 QUIC can use any of the cipher suites defined in [TLS13] with the 1113 exception of TLS_AES_128_CCM_8_SHA256. A cipher suite MUST NOT be 1114 negotiated unless a header protection scheme is defined for the 1115 cipher suite. This document defines a header protection scheme for 1116 all cipher suites defined in [TLS13] aside from 1117 TLS_AES_128_CCM_8_SHA256. These cipher suites have a 16-byte 1118 authentication tag and produce an output 16 bytes larger than their 1119 input. 1121 Note: An endpoint MUST NOT reject a ClientHello that offers a cipher 1122 suite that it does not support, or it would be impossible to 1123 deploy a new cipher suite. This also applies to 1124 TLS_AES_128_CCM_8_SHA256. 1126 When constructing packets, the AEAD function is applied prior to 1127 applying header protection; see Section 5.4. The unprotected packet 1128 header is part of the associated data (A). When processing packets, 1129 an endpoint first removes the header protection. 1131 The key and IV for the packet are computed as described in 1132 Section 5.1. The nonce, N, is formed by combining the packet 1133 protection IV with the packet number. The 62 bits of the 1134 reconstructed QUIC packet number in network byte order are left- 1135 padded with zeros to the size of the IV. The exclusive OR of the 1136 padded packet number and the IV forms the AEAD nonce. 1138 The associated data, A, for the AEAD is the contents of the QUIC 1139 header, starting from the first byte of either the short or long 1140 header, up to and including the unprotected packet number. 1142 The input plaintext, P, for the AEAD is the payload of the QUIC 1143 packet, as described in [QUIC-TRANSPORT]. 1145 The output ciphertext, C, of the AEAD is transmitted in place of P. 1147 Some AEAD functions have limits for how many packets can be encrypted 1148 under the same key and IV; see Section 6.6. This might be lower than 1149 the packet number limit. An endpoint MUST initiate a key update 1150 (Section 6) prior to exceeding any limit set for the AEAD that is in 1151 use. 1153 5.4. Header Protection 1155 Parts of QUIC packet headers, in particular the Packet Number field, 1156 are protected using a key that is derived separately from the packet 1157 protection key and IV. The key derived using the "quic hp" label is 1158 used to provide confidentiality protection for those fields that are 1159 not exposed to on-path elements. 1161 This protection applies to the least-significant bits of the first 1162 byte, plus the Packet Number field. The four least-significant bits 1163 of the first byte are protected for packets with long headers; the 1164 five least significant bits of the first byte are protected for 1165 packets with short headers. For both header forms, this covers the 1166 reserved bits and the Packet Number Length field; the Key Phase bit 1167 is also protected for packets with a short header. 1169 The same header protection key is used for the duration of the 1170 connection, with the value not changing after a key update (see 1171 Section 6). This allows header protection to be used to protect the 1172 key phase. 1174 This process does not apply to Retry or Version Negotiation packets, 1175 which do not contain a protected payload or any of the fields that 1176 are protected by this process. 1178 5.4.1. Header Protection Application 1180 Header protection is applied after packet protection is applied (see 1181 Section 5.3). The ciphertext of the packet is sampled and used as 1182 input to an encryption algorithm. The algorithm used depends on the 1183 negotiated AEAD. 1185 The output of this algorithm is a 5-byte mask that is applied to the 1186 protected header fields using exclusive OR. The least significant 1187 bits of the first byte of the packet are masked by the least 1188 significant bits of the first mask byte, and the packet number is 1189 masked with the remaining bytes. Any unused bytes of mask that might 1190 result from a shorter packet number encoding are unused. 1192 Figure 6 shows a sample algorithm for applying header protection. 1193 Removing header protection only differs in the order in which the 1194 packet number length (pn_length) is determined. 1196 mask = header_protection(hp_key, sample) 1198 pn_length = (packet[0] & 0x03) + 1 1199 if (packet[0] & 0x80) == 0x80: 1200 # Long header: 4 bits masked 1201 packet[0] ^= mask[0] & 0x0f 1202 else: 1203 # Short header: 5 bits masked 1204 packet[0] ^= mask[0] & 0x1f 1206 # pn_offset is the start of the Packet Number field. 1207 packet[pn_offset:pn_offset+pn_length] ^= mask[1:1+pn_length] 1209 Figure 6: Header Protection Pseudocode 1211 Specific header protection functions are defined based on the 1212 selected cipher suite; see Section 5.4.3 and Section 5.4.4. 1214 Figure 7 shows an example long header packet (Initial) and a short 1215 header packet. Figure 7 shows the fields in each header that are 1216 covered by header protection and the portion of the protected packet 1217 payload that is sampled. 1219 Initial Packet { 1220 Header Form (1) = 1, 1221 Fixed Bit (1) = 1, 1222 Long Packet Type (2) = 0, 1223 Reserved Bits (2), # Protected 1224 Packet Number Length (2), # Protected 1225 Version (32), 1226 DCID Len (8), 1227 Destination Connection ID (0..160), 1228 SCID Len (8), 1229 Source Connection ID (0..160), 1230 Token Length (i), 1231 Token (..), 1232 Length (i), 1233 Packet Number (8..32), # Protected 1234 Protected Payload (0..24), # Skipped Part 1235 Protected Payload (128), # Sampled Part 1236 Protected Payload (..) # Remainder 1237 } 1239 Short Header Packet { 1240 Header Form (1) = 0, 1241 Fixed Bit (1) = 1, 1242 Spin Bit (1), 1243 Reserved Bits (2), # Protected 1244 Key Phase (1), # Protected 1245 Packet Number Length (2), # Protected 1246 Destination Connection ID (0..160), 1247 Packet Number (8..32), # Protected 1248 Protected Payload (0..24), # Skipped Part 1249 Protected Payload (128), # Sampled Part 1250 Protected Payload (..), # Remainder 1251 } 1253 Figure 7: Header Protection and Ciphertext Sample 1255 Before a TLS cipher suite can be used with QUIC, a header protection 1256 algorithm MUST be specified for the AEAD used with that cipher suite. 1257 This document defines algorithms for AEAD_AES_128_GCM, 1258 AEAD_AES_128_CCM, AEAD_AES_256_GCM (all these AES AEADs are defined 1259 in [AEAD]), and AEAD_CHACHA20_POLY1305 (defined in [CHACHA]). Prior 1260 to TLS selecting a cipher suite, AES header protection is used 1261 (Section 5.4.3), matching the AEAD_AES_128_GCM packet protection. 1263 5.4.2. Header Protection Sample 1265 The header protection algorithm uses both the header protection key 1266 and a sample of the ciphertext from the packet Payload field. 1268 The same number of bytes are always sampled, but an allowance needs 1269 to be made for the endpoint removing protection, which will not know 1270 the length of the Packet Number field. In sampling the packet 1271 ciphertext, the Packet Number field is assumed to be 4 bytes long 1272 (its maximum possible encoded length). 1274 An endpoint MUST discard packets that are not long enough to contain 1275 a complete sample. 1277 To ensure that sufficient data is available for sampling, packets are 1278 padded so that the combined lengths of the encoded packet number and 1279 protected payload is at least 4 bytes longer than the sample required 1280 for header protection. The cipher suites defined in [TLS13] - other 1281 than TLS_AES_128_CCM_8_SHA256, for which a header protection scheme 1282 is not defined in this document - have 16-byte expansions and 16-byte 1283 header protection samples. This results in needing at least 3 bytes 1284 of frames in the unprotected payload if the packet number is encoded 1285 on a single byte, or 2 bytes of frames for a 2-byte packet number 1286 encoding. 1288 The sampled ciphertext for a packet with a short header can be 1289 determined by the following pseudocode: 1291 sample_offset = 1 + len(connection_id) + 4 1293 sample = packet[sample_offset..sample_offset+sample_length] 1295 For example, for a packet with a short header, an 8-byte connection 1296 ID, and protected with AEAD_AES_128_GCM, the sample takes bytes 13 to 1297 28 inclusive (using zero-based indexing). 1299 A packet with a long header is sampled in the same way, noting that 1300 multiple QUIC packets might be included in the same UDP datagram and 1301 that each one is handled separately. 1303 sample_offset = 7 + len(destination_connection_id) + 1304 len(source_connection_id) + 1305 len(payload_length) + 4 1306 if packet_type == Initial: 1307 sample_offset += len(token_length) + 1308 len(token) 1310 sample = packet[sample_offset..sample_offset+sample_length] 1312 5.4.3. AES-Based Header Protection 1314 This section defines the packet protection algorithm for 1315 AEAD_AES_128_GCM, AEAD_AES_128_CCM, and AEAD_AES_256_GCM. 1316 AEAD_AES_128_GCM and AEAD_AES_128_CCM use 128-bit AES in electronic 1317 code-book (ECB) mode. AEAD_AES_256_GCM uses 256-bit AES in ECB mode. 1318 AES is defined in [AES]. 1320 This algorithm samples 16 bytes from the packet ciphertext. This 1321 value is used as the input to AES-ECB. In pseudocode, the header 1322 protection function is defined as: 1324 header_protection(hp_key, sample): 1325 mask = AES-ECB(hp_key, sample) 1327 5.4.4. ChaCha20-Based Header Protection 1329 When AEAD_CHACHA20_POLY1305 is in use, header protection uses the raw 1330 ChaCha20 function as defined in Section 2.4 of [CHACHA]. This uses a 1331 256-bit key and 16 bytes sampled from the packet protection output. 1333 The first 4 bytes of the sampled ciphertext are the block counter. A 1334 ChaCha20 implementation could take a 32-bit integer in place of a 1335 byte sequence, in which case the byte sequence is interpreted as a 1336 little-endian value. 1338 The remaining 12 bytes are used as the nonce. A ChaCha20 1339 implementation might take an array of three 32-bit integers in place 1340 of a byte sequence, in which case the nonce bytes are interpreted as 1341 a sequence of 32-bit little-endian integers. 1343 The encryption mask is produced by invoking ChaCha20 to protect 5 1344 zero bytes. In pseudocode, the header protection function is defined 1345 as: 1347 header_protection(hp_key, sample): 1348 counter = sample[0..3] 1349 nonce = sample[4..15] 1350 mask = ChaCha20(hp_key, counter, nonce, {0,0,0,0,0}) 1352 5.5. Receiving Protected Packets 1354 Once an endpoint successfully receives a packet with a given packet 1355 number, it MUST discard all packets in the same packet number space 1356 with higher packet numbers if they cannot be successfully unprotected 1357 with either the same key, or - if there is a key update - the next 1358 packet protection key (see Section 6). Similarly, a packet that 1359 appears to trigger a key update, but cannot be unprotected 1360 successfully MUST be discarded. 1362 Failure to unprotect a packet does not necessarily indicate the 1363 existence of a protocol error in a peer or an attack. The truncated 1364 packet number encoding used in QUIC can cause packet numbers to be 1365 decoded incorrectly if they are delayed significantly. 1367 5.6. Use of 0-RTT Keys 1369 If 0-RTT keys are available (see Section 4.6.1), the lack of replay 1370 protection means that restrictions on their use are necessary to 1371 avoid replay attacks on the protocol. 1373 A client MUST only use 0-RTT keys to protect data that is idempotent. 1374 A client MAY wish to apply additional restrictions on what data it 1375 sends prior to the completion of the TLS handshake. A client 1376 otherwise treats 0-RTT keys as equivalent to 1-RTT keys, except that 1377 it MUST NOT send ACKs with 0-RTT keys. 1379 A client that receives an indication that its 0-RTT data has been 1380 accepted by a server can send 0-RTT data until it receives all of the 1381 server's handshake messages. A client SHOULD stop sending 0-RTT data 1382 if it receives an indication that 0-RTT data has been rejected. 1384 A server MUST NOT use 0-RTT keys to protect packets; it uses 1-RTT 1385 keys to protect acknowledgements of 0-RTT packets. A client MUST NOT 1386 attempt to decrypt 0-RTT packets it receives and instead MUST discard 1387 them. 1389 Once a client has installed 1-RTT keys, it MUST NOT send any more 1390 0-RTT packets. 1392 Note: 0-RTT data can be acknowledged by the server as it receives 1393 it, but any packets containing acknowledgments of 0-RTT data 1394 cannot have packet protection removed by the client until the TLS 1395 handshake is complete. The 1-RTT keys necessary to remove packet 1396 protection cannot be derived until the client receives all server 1397 handshake messages. 1399 5.7. Receiving Out-of-Order Protected Packets 1401 Due to reordering and loss, protected packets might be received by an 1402 endpoint before the final TLS handshake messages are received. A 1403 client will be unable to decrypt 1-RTT packets from the server, 1404 whereas a server will be able to decrypt 1-RTT packets from the 1405 client. Endpoints in either role MUST NOT decrypt 1-RTT packets from 1406 their peer prior to completing the handshake. 1408 Even though 1-RTT keys are available to a server after receiving the 1409 first handshake messages from a client, it is missing assurances on 1410 the client state: 1412 * The client is not authenticated, unless the server has chosen to 1413 use a pre-shared key and validated the client's pre-shared key 1414 binder; see Section 4.2.11 of [TLS13]. 1416 * The client has not demonstrated liveness, unless the server has 1417 validated the client's address with a Retry packet or other means; 1418 see Section 8.1 of [QUIC-TRANSPORT]. 1420 * Any received 0-RTT data that the server responds to might be due 1421 to a replay attack. 1423 Therefore, the server's use of 1-RTT keys before the handshake is 1424 complete is limited to sending data. A server MUST NOT process 1425 incoming 1-RTT protected packets before the TLS handshake is 1426 complete. Because sending acknowledgments indicates that all frames 1427 in a packet have been processed, a server cannot send acknowledgments 1428 for 1-RTT packets until the TLS handshake is complete. Received 1429 packets protected with 1-RTT keys MAY be stored and later decrypted 1430 and used once the handshake is complete. 1432 Note: TLS implementations might provide all 1-RTT secrets prior to 1433 handshake completion. Even where QUIC implementations have 1-RTT 1434 read keys, those keys cannot be used prior to completing the 1435 handshake. 1437 The requirement for the server to wait for the client Finished 1438 message creates a dependency on that message being delivered. A 1439 client can avoid the potential for head-of-line blocking that this 1440 implies by sending its 1-RTT packets coalesced with a Handshake 1441 packet containing a copy of the CRYPTO frame that carries the 1442 Finished message, until one of the Handshake packets is acknowledged. 1443 This enables immediate server processing for those packets. 1445 A server could receive packets protected with 0-RTT keys prior to 1446 receiving a TLS ClientHello. The server MAY retain these packets for 1447 later decryption in anticipation of receiving a ClientHello. 1449 A client generally receives 1-RTT keys at the same time as the 1450 handshake completes. Even if it has 1-RTT secrets, a client MUST NOT 1451 process incoming 1-RTT protected packets before the TLS handshake is 1452 complete. 1454 5.8. Retry Packet Integrity 1456 Retry packets (see the Retry Packet section of [QUIC-TRANSPORT]) 1457 carry a Retry Integrity Tag that provides two properties: it allows 1458 discarding packets that have accidentally been corrupted by the 1459 network, and it diminishes off-path attackers' ability to send valid 1460 Retry packets. 1462 The Retry Integrity Tag is a 128-bit field that is computed as the 1463 output of AEAD_AES_128_GCM ([AEAD]) used with the following inputs: 1465 * The secret key, K, is 128 bits equal to 1466 0xccce187ed09a09d05728155a6cb96be1. 1468 * The nonce, N, is 96 bits equal to 0xe54930f97f2136f0530a8c1c. 1470 * The plaintext, P, is empty. 1472 * The associated data, A, is the contents of the Retry Pseudo- 1473 Packet, as illustrated in Figure 8: 1475 The secret key and the nonce are values derived by calling HKDF- 1476 Expand-Label using 1477 0x8b0d37eb8535022ebc8d76a207d80df22646ec06dc809642c30a8baa2baaff4c as 1478 the secret, with labels being "quic key" and "quic iv" (Section 5.1). 1480 Retry Pseudo-Packet { 1481 ODCID Length (8), 1482 Original Destination Connection ID (0..160), 1483 Header Form (1) = 1, 1484 Fixed Bit (1) = 1, 1485 Long Packet Type (2) = 3, 1486 Type-Specific Bits (4), 1487 Version (32), 1488 DCID Len (8), 1489 Destination Connection ID (0..160), 1490 SCID Len (8), 1491 Source Connection ID (0..160), 1492 Retry Token (..), 1493 } 1495 Figure 8: Retry Pseudo-Packet 1497 The Retry Pseudo-Packet is not sent over the wire. It is computed by 1498 taking the transmitted Retry packet, removing the Retry Integrity Tag 1499 and prepending the two following fields: 1501 ODCID Length: The ODCID Length field contains the length in bytes of 1502 the Original Destination Connection ID field that follows it, 1503 encoded as an 8-bit unsigned integer. 1505 Original Destination Connection ID: The Original Destination 1506 Connection ID contains the value of the Destination Connection ID 1507 from the Initial packet that this Retry is in response to. The 1508 length of this field is given in ODCID Length. The presence of 1509 this field mitigates an off-path attacker's ability to inject a 1510 Retry packet. 1512 6. Key Update 1514 Once the handshake is confirmed (see Section 4.1.2), an endpoint MAY 1515 initiate a key update. 1517 The Key Phase bit indicates which packet protection keys are used to 1518 protect the packet. The Key Phase bit is initially set to 0 for the 1519 first set of 1-RTT packets and toggled to signal each subsequent key 1520 update. 1522 The Key Phase bit allows a recipient to detect a change in keying 1523 material without needing to receive the first packet that triggered 1524 the change. An endpoint that notices a changed Key Phase bit updates 1525 keys and decrypts the packet that contains the changed value. 1527 This mechanism replaces the TLS KeyUpdate message. Endpoints MUST 1528 NOT send a TLS KeyUpdate message. Endpoints MUST treat the receipt 1529 of a TLS KeyUpdate message as a connection error of type 0x10a, 1530 equivalent to a fatal TLS alert of unexpected_message (see 1531 Section 4.8). 1533 Figure 9 shows a key update process, where the initial set of keys 1534 used (identified with @M) are replaced by updated keys (identified 1535 with @N). The value of the Key Phase bit is indicated in brackets 1536 []. 1538 Initiating Peer Responding Peer 1540 @M [0] QUIC Packets 1542 ... Update to @N 1543 @N [1] QUIC Packets 1544 --------> 1545 Update to @N ... 1546 QUIC Packets [1] @N 1547 <-------- 1548 QUIC Packets [1] @N 1549 containing ACK 1550 <-------- 1551 ... Key Update Permitted 1553 @N [1] QUIC Packets 1554 containing ACK for @N packets 1555 --------> 1556 Key Update Permitted ... 1558 Figure 9: Key Update 1560 6.1. Initiating a Key Update 1562 Endpoints maintain separate read and write secrets for packet 1563 protection. An endpoint initiates a key update by updating its 1564 packet protection write secret and using that to protect new packets. 1565 The endpoint creates a new write secret from the existing write 1566 secret as performed in Section 7.2 of [TLS13]. This uses the KDF 1567 function provided by TLS with a label of "quic ku". The 1568 corresponding key and IV are created from that secret as defined in 1569 Section 5.1. The header protection key is not updated. 1571 For example, to update write keys with TLS 1.3, HKDF-Expand-Label is 1572 used as: 1574 secret_ = HKDF-Expand-Label(secret_, "quic ku", 1575 "", Hash.length) 1577 The endpoint toggles the value of the Key Phase bit and uses the 1578 updated key and IV to protect all subsequent packets. 1580 An endpoint MUST NOT initiate a key update prior to having confirmed 1581 the handshake (Section 4.1.2). An endpoint MUST NOT initiate a 1582 subsequent key update unless it has received an acknowledgment for a 1583 packet that was sent protected with keys from the current key phase. 1584 This ensures that keys are available to both peers before another key 1585 update can be initiated. This can be implemented by tracking the 1586 lowest packet number sent with each key phase, and the highest 1587 acknowledged packet number in the 1-RTT space: once the latter is 1588 higher than or equal to the former, another key update can be 1589 initiated. 1591 Note: Keys of packets other than the 1-RTT packets are never 1592 updated; their keys are derived solely from the TLS handshake 1593 state. 1595 The endpoint that initiates a key update also updates the keys that 1596 it uses for receiving packets. These keys will be needed to process 1597 packets the peer sends after updating. 1599 An endpoint MUST retain old keys until it has successfully 1600 unprotected a packet sent using the new keys. An endpoint SHOULD 1601 retain old keys for some time after unprotecting a packet sent using 1602 the new keys. Discarding old keys too early can cause delayed 1603 packets to be discarded. Discarding packets will be interpreted as 1604 packet loss by the peer and could adversely affect performance. 1606 6.2. Responding to a Key Update 1608 A peer is permitted to initiate a key update after receiving an 1609 acknowledgement of a packet in the current key phase. An endpoint 1610 detects a key update when processing a packet with a key phase that 1611 differs from the value used to protect the last packet it sent. To 1612 process this packet, the endpoint uses the next packet protection key 1613 and IV. See Section 6.3 for considerations about generating these 1614 keys. 1616 If a packet is successfully processed using the next key and IV, then 1617 the peer has initiated a key update. The endpoint MUST update its 1618 send keys to the corresponding key phase in response, as described in 1619 Section 6.1. Sending keys MUST be updated before sending an 1620 acknowledgement for the packet that was received with updated keys. 1621 By acknowledging the packet that triggered the key update in a packet 1622 protected with the updated keys, the endpoint signals that the key 1623 update is complete. 1625 An endpoint can defer sending the packet or acknowledgement according 1626 to its normal packet sending behaviour; it is not necessary to 1627 immediately generate a packet in response to a key update. The next 1628 packet sent by the endpoint will use the updated keys. The next 1629 packet that contains an acknowledgement will cause the key update to 1630 be completed. If an endpoint detects a second update before it has 1631 sent any packets with updated keys containing an acknowledgement for 1632 the packet that initiated the key update, it indicates that its peer 1633 has updated keys twice without awaiting confirmation. An endpoint 1634 MAY treat consecutive key updates as a connection error of type 1635 KEY_UPDATE_ERROR. 1637 An endpoint that receives an acknowledgement that is carried in a 1638 packet protected with old keys where any acknowledged packet was 1639 protected with newer keys MAY treat that as a connection error of 1640 type KEY_UPDATE_ERROR. This indicates that a peer has received and 1641 acknowledged a packet that initiates a key update, but has not 1642 updated keys in response. 1644 6.3. Timing of Receive Key Generation 1646 Endpoints responding to an apparent key update MUST NOT generate a 1647 timing side-channel signal that might indicate that the Key Phase bit 1648 was invalid (see Section 9.4). Endpoints can use dummy packet 1649 protection keys in place of discarded keys when key updates are not 1650 yet permitted. Using dummy keys will generate no variation in the 1651 timing signal produced by attempting to remove packet protection, and 1652 results in all packets with an invalid Key Phase bit being rejected. 1654 The process of creating new packet protection keys for receiving 1655 packets could reveal that a key update has occurred. An endpoint MAY 1656 perform this process as part of packet processing, but this creates a 1657 timing signal that can be used by an attacker to learn when key 1658 updates happen and thus the value of the Key Phase bit in certain 1659 packets. Endpoints MAY instead defer the creation of the next set of 1660 receive packet protection keys until some time after a key update 1661 completes, up to three times the PTO; see Section 6.5. 1663 Once generated, the next set of packet protection keys SHOULD be 1664 retained, even if the packet that was received was subsequently 1665 discarded. Packets containing apparent key updates are easy to forge 1666 and - while the process of key update does not require significant 1667 effort - triggering this process could be used by an attacker for 1668 DoS. 1670 For this reason, endpoints MUST be able to retain two sets of packet 1671 protection keys for receiving packets: the current and the next. 1672 Retaining the previous keys in addition to these might improve 1673 performance, but this is not essential. 1675 6.4. Sending with Updated Keys 1677 An endpoint never sends packets that are protected with old keys. 1678 Only the current keys are used. Keys used for protecting packets can 1679 be discarded immediately after switching to newer keys. 1681 Packets with higher packet numbers MUST be protected with either the 1682 same or newer packet protection keys than packets with lower packet 1683 numbers. An endpoint that successfully removes protection with old 1684 keys when newer keys were used for packets with lower packet numbers 1685 MUST treat this as a connection error of type KEY_UPDATE_ERROR. 1687 6.5. Receiving with Different Keys 1689 For receiving packets during a key update, packets protected with 1690 older keys might arrive if they were delayed by the network. 1691 Retaining old packet protection keys allows these packets to be 1692 successfully processed. 1694 As packets protected with keys from the next key phase use the same 1695 Key Phase value as those protected with keys from the previous key 1696 phase, it can be necessary to distinguish between the two. This can 1697 be done using packet numbers. A recovered packet number that is 1698 lower than any packet number from the current key phase uses the 1699 previous packet protection keys; a recovered packet number that is 1700 higher than any packet number from the current key phase requires the 1701 use of the next packet protection keys. 1703 Some care is necessary to ensure that any process for selecting 1704 between previous, current, and next packet protection keys does not 1705 expose a timing side channel that might reveal which keys were used 1706 to remove packet protection. See Section 9.5 for more information. 1708 Alternatively, endpoints can retain only two sets of packet 1709 protection keys, swapping previous for next after enough time has 1710 passed to allow for reordering in the network. In this case, the Key 1711 Phase bit alone can be used to select keys. 1713 An endpoint MAY allow a period of approximately the Probe Timeout 1714 (PTO; see [QUIC-RECOVERY]) after receiving a packet that uses the new 1715 key generation before it creates the next set of packet protection 1716 keys. These updated keys MAY replace the previous keys at that time. 1717 With the caveat that PTO is a subjective measure - that is, a peer 1718 could have a different view of the RTT - this time is expected to be 1719 long enough that any reordered packets would be declared lost by a 1720 peer even if they were acknowledged and short enough to allow for 1721 subsequent key updates. 1723 Endpoints need to allow for the possibility that a peer might not be 1724 able to decrypt packets that initiate a key update during the period 1725 when it retains old keys. Endpoints SHOULD wait three times the PTO 1726 before initiating a key update after receiving an acknowledgment that 1727 confirms that the previous key update was received. Failing to allow 1728 sufficient time could lead to packets being discarded. 1730 An endpoint SHOULD retain old read keys for no more than three times 1731 the PTO after having received a packet protected using the new keys. 1732 After this period, old read keys and their corresponding secrets 1733 SHOULD be discarded. 1735 6.6. Limits on AEAD Usage 1737 This document sets usage limits for AEAD algorithms to ensure that 1738 overuse does not give an adversary a disproportionate advantage in 1739 attacking the confidentiality and integrity of communications when 1740 using QUIC. 1742 The usage limits defined in TLS 1.3 exist for protection against 1743 attacks on confidentiality and apply to successful applications of 1744 AEAD protection. The integrity protections in authenticated 1745 encryption also depend on limiting the number of attempts to forge 1746 packets. TLS achieves this by closing connections after any record 1747 fails an authentication check. In comparison, QUIC ignores any 1748 packet that cannot be authenticated, allowing multiple forgery 1749 attempts. 1751 QUIC accounts for AEAD confidentiality and integrity limits 1752 separately. The confidentiality limit applies to the number of 1753 packets encrypted with a given key. The integrity limit applies to 1754 the number of packets decrypted within a given connection. Details 1755 on enforcing these limits for each AEAD algorithm follow below. 1757 Endpoints MUST count the number of encrypted packets for each set of 1758 keys. If the total number of encrypted packets with the same key 1759 exceeds the confidentiality limit for the selected AEAD, the endpoint 1760 MUST stop using those keys. Endpoints MUST initiate a key update 1761 before sending more protected packets than the confidentiality limit 1762 for the selected AEAD permits. If a key update is not possible or 1763 integrity limits are reached, the endpoint MUST stop using the 1764 connection and only send stateless resets in response to receiving 1765 packets. It is RECOMMENDED that endpoints immediately close the 1766 connection with a connection error of type AEAD_LIMIT_REACHED before 1767 reaching a state where key updates are not possible. 1769 For AEAD_AES_128_GCM and AEAD_AES_256_GCM, the confidentiality limit 1770 is 2^23 encrypted packets; see Appendix B.1. For 1771 AEAD_CHACHA20_POLY1305, the confidentiality limit is greater than the 1772 number of possible packets (2^62) and so can be disregarded. For 1773 AEAD_AES_128_CCM, the confidentiality limit is 2^21.5 encrypted 1774 packets; see Appendix B.2. Applying a limit reduces the probability 1775 that an attacker can distinguish the AEAD in use from a random 1776 permutation; see [AEBounds], [ROBUST], and [GCM-MU]. 1778 In addition to counting packets sent, endpoints MUST count the number 1779 of received packets that fail authentication during the lifetime of a 1780 connection. If the total number of received packets that fail 1781 authentication within the connection, across all keys, exceeds the 1782 integrity limit for the selected AEAD, the endpoint MUST immediately 1783 close the connection with a connection error of type 1784 AEAD_LIMIT_REACHED and not process any more packets. 1786 For AEAD_AES_128_GCM and AEAD_AES_256_GCM, the integrity limit is 1787 2^52 invalid packets; see Appendix B.1. For AEAD_CHACHA20_POLY1305, 1788 the integrity limit is 2^36 invalid packets; see [AEBounds]. For 1789 AEAD_AES_128_CCM, the integrity limit is 2^21.5 invalid packets; see 1790 Appendix B.2. Applying this limit reduces the probability that an 1791 attacker can successfully forge a packet; see [AEBounds], [ROBUST], 1792 and [GCM-MU]. 1794 Endpoints that limit the size of packets MAY use higher 1795 confidentiality and integrity limits; see Appendix B for details. 1797 Future analyses and specifications MAY relax confidentiality or 1798 integrity limits for an AEAD. 1800 Note: These limits were originally calculated using assumptions 1801 about the limits on TLS record size. The maximum size of a TLS 1802 record is 2^14 bytes. In comparison, QUIC packets can be up to 1803 2^16 bytes. However, it is expected that QUIC packets will 1804 generally be smaller than TLS records. Where packets might be 1805 larger than 2^14 bytes in length, smaller limits might be needed. 1807 Any TLS cipher suite that is specified for use with QUIC MUST define 1808 limits on the use of the associated AEAD function that preserves 1809 margins for confidentiality and integrity. That is, limits MUST be 1810 specified for the number of packets that can be authenticated and for 1811 the number of packets that can fail authentication. Providing a 1812 reference to any analysis upon which values are based - and any 1813 assumptions used in that analysis - allows limits to be adapted to 1814 varying usage conditions. 1816 6.7. Key Update Error Code 1818 The KEY_UPDATE_ERROR error code (0xe) is used to signal errors 1819 related to key updates. 1821 7. Security of Initial Messages 1823 Initial packets are not protected with a secret key, so they are 1824 subject to potential tampering by an attacker. QUIC provides 1825 protection against attackers that cannot read packets, but does not 1826 attempt to provide additional protection against attacks where the 1827 attacker can observe and inject packets. Some forms of tampering - 1828 such as modifying the TLS messages themselves - are detectable, but 1829 some - such as modifying ACKs - are not. 1831 For example, an attacker could inject a packet containing an ACK 1832 frame that makes it appear that a packet had not been received or to 1833 create a false impression of the state of the connection (e.g., by 1834 modifying the ACK Delay). Note that such a packet could cause a 1835 legitimate packet to be dropped as a duplicate. Implementations 1836 SHOULD use caution in relying on any data that is contained in 1837 Initial packets that is not otherwise authenticated. 1839 It is also possible for the attacker to tamper with data that is 1840 carried in Handshake packets, but because that tampering requires 1841 modifying TLS handshake messages, that tampering will cause the TLS 1842 handshake to fail. 1844 8. QUIC-Specific Adjustments to the TLS Handshake 1846 Certain aspects of the TLS handshake are different when used with 1847 QUIC. 1849 QUIC also requires additional features from TLS. In addition to 1850 negotiation of cryptographic parameters, the TLS handshake carries 1851 and authenticates values for QUIC transport parameters. 1853 8.1. Protocol Negotiation 1855 QUIC requires that the cryptographic handshake provide authenticated 1856 protocol negotiation. TLS uses Application Layer Protocol 1857 Negotiation ([ALPN]) to select an application protocol. Unless 1858 another mechanism is used for agreeing on an application protocol, 1859 endpoints MUST use ALPN for this purpose. 1861 When using ALPN, endpoints MUST immediately close a connection (see 1862 Section 10.2 of [QUIC-TRANSPORT]) with a no_application_protocol TLS 1863 alert (QUIC error code 0x178; see Section 4.8) if an application 1864 protocol is not negotiated. While [ALPN] only specifies that servers 1865 use this alert, QUIC clients MUST use error 0x178 to terminate a 1866 connection when ALPN negotiation fails. 1868 An application protocol MAY restrict the QUIC versions that it can 1869 operate over. Servers MUST select an application protocol compatible 1870 with the QUIC version that the client has selected. The server MUST 1871 treat the inability to select a compatible application protocol as a 1872 connection error of type 0x178 (no_application_protocol). Similarly, 1873 a client MUST treat the selection of an incompatible application 1874 protocol by a server as a connection error of type 0x178. 1876 8.2. QUIC Transport Parameters Extension 1878 QUIC transport parameters are carried in a TLS extension. Different 1879 versions of QUIC might define a different method for negotiating 1880 transport configuration. 1882 Including transport parameters in the TLS handshake provides 1883 integrity protection for these values. 1885 enum { 1886 quic_transport_parameters(0xffa5), (65535) 1887 } ExtensionType; 1889 The extension_data field of the quic_transport_parameters extension 1890 contains a value that is defined by the version of QUIC that is in 1891 use. 1893 The quic_transport_parameters extension is carried in the ClientHello 1894 and the EncryptedExtensions messages during the handshake. Endpoints 1895 MUST send the quic_transport_parameters extension; endpoints that 1896 receive ClientHello or EncryptedExtensions messages without the 1897 quic_transport_parameters extension MUST close the connection with an 1898 error of type 0x16d (equivalent to a fatal TLS missing_extension 1899 alert, see Section 4.8). 1901 While the transport parameters are technically available prior to the 1902 completion of the handshake, they cannot be fully trusted until the 1903 handshake completes, and reliance on them should be minimized. 1904 However, any tampering with the parameters will cause the handshake 1905 to fail. 1907 Endpoints MUST NOT send this extension in a TLS connection that does 1908 not use QUIC (such as the use of TLS with TCP defined in [TLS13]). A 1909 fatal unsupported_extension alert MUST be sent by an implementation 1910 that supports this extension if the extension is received when the 1911 transport is not QUIC. 1913 8.3. Removing the EndOfEarlyData Message 1915 The TLS EndOfEarlyData message is not used with QUIC. QUIC does not 1916 rely on this message to mark the end of 0-RTT data or to signal the 1917 change to Handshake keys. 1919 Clients MUST NOT send the EndOfEarlyData message. A server MUST 1920 treat receipt of a CRYPTO frame in a 0-RTT packet as a connection 1921 error of type PROTOCOL_VIOLATION. 1923 As a result, EndOfEarlyData does not appear in the TLS handshake 1924 transcript. 1926 8.4. Prohibit TLS Middlebox Compatibility Mode 1928 Appendix D.4 of [TLS13] describes an alteration to the TLS 1.3 1929 handshake as a workaround for bugs in some middleboxes. The TLS 1.3 1930 middlebox compatibility mode involves setting the legacy_session_id 1931 field to a 32-byte value in the ClientHello and ServerHello, then 1932 sending a change_cipher_spec record. Both field and record carry no 1933 semantic content and are ignored. 1935 This mode has no use in QUIC as it only applies to middleboxes that 1936 interfere with TLS over TCP. QUIC also provides no means to carry a 1937 change_cipher_spec record. A client MUST NOT request the use of the 1938 TLS 1.3 compatibility mode. A server SHOULD treat the receipt of a 1939 TLS ClientHello with a non-empty legacy_session_id field as a 1940 connection error of type PROTOCOL_VIOLATION. 1942 9. Security Considerations 1944 All of the security considerations that apply to TLS also apply to 1945 the use of TLS in QUIC. Reading all of [TLS13] and its appendices is 1946 the best way to gain an understanding of the security properties of 1947 QUIC. 1949 This section summarizes some of the more important security aspects 1950 specific to the TLS integration, though there are many security- 1951 relevant details in the remainder of the document. 1953 9.1. Session Linkability 1955 Use of TLS session tickets allows servers and possibly other entities 1956 to correlate connections made by the same client; see Section 4.5 for 1957 details. 1959 9.2. Replay Attacks with 0-RTT 1961 As described in Section 8 of [TLS13], use of TLS early data comes 1962 with an exposure to replay attack. The use of 0-RTT in QUIC is 1963 similarly vulnerable to replay attack. 1965 Endpoints MUST implement and use the replay protections described in 1966 [TLS13], however it is recognized that these protections are 1967 imperfect. Therefore, additional consideration of the risk of replay 1968 is needed. 1970 QUIC is not vulnerable to replay attack, except via the application 1971 protocol information it might carry. The management of QUIC protocol 1972 state based on the frame types defined in [QUIC-TRANSPORT] is not 1973 vulnerable to replay. Processing of QUIC frames is idempotent and 1974 cannot result in invalid connection states if frames are replayed, 1975 reordered or lost. QUIC connections do not produce effects that last 1976 beyond the lifetime of the connection, except for those produced by 1977 the application protocol that QUIC serves. 1979 Note: TLS session tickets and address validation tokens are used to 1980 carry QUIC configuration information between connections. 1981 Specifically, to enable a server to efficiently recover state that 1982 is used in connection establishment and address validation. These 1983 MUST NOT be used to communicate application semantics between 1984 endpoints; clients MUST treat them as opaque values. The 1985 potential for reuse of these tokens means that they require 1986 stronger protections against replay. 1988 A server that accepts 0-RTT on a connection incurs a higher cost than 1989 accepting a connection without 0-RTT. This includes higher 1990 processing and computation costs. Servers need to consider the 1991 probability of replay and all associated costs when accepting 0-RTT. 1993 Ultimately, the responsibility for managing the risks of replay 1994 attacks with 0-RTT lies with an application protocol. An application 1995 protocol that uses QUIC MUST describe how the protocol uses 0-RTT and 1996 the measures that are employed to protect against replay attack. An 1997 analysis of replay risk needs to consider all QUIC protocol features 1998 that carry application semantics. 2000 Disabling 0-RTT entirely is the most effective defense against replay 2001 attack. 2003 QUIC extensions MUST describe how replay attacks affect their 2004 operation, or prohibit their use in 0-RTT. Application protocols 2005 MUST either prohibit the use of extensions that carry application 2006 semantics in 0-RTT or provide replay mitigation strategies. 2008 9.3. Packet Reflection Attack Mitigation 2010 A small ClientHello that results in a large block of handshake 2011 messages from a server can be used in packet reflection attacks to 2012 amplify the traffic generated by an attacker. 2014 QUIC includes three defenses against this attack. First, the packet 2015 containing a ClientHello MUST be padded to a minimum size. Second, 2016 if responding to an unverified source address, the server is 2017 forbidden to send more than three times as many bytes as the number 2018 of bytes it has received (see Section 8.1 of [QUIC-TRANSPORT]). 2019 Finally, because acknowledgements of Handshake packets are 2020 authenticated, a blind attacker cannot forge them. Put together, 2021 these defenses limit the level of amplification. 2023 9.4. Header Protection Analysis 2025 [NAN] analyzes authenticated encryption algorithms that provide nonce 2026 privacy, referred to as "Hide Nonce" (HN) transforms. The general 2027 header protection construction in this document is one of those 2028 algorithms (HN1). Header protection uses the output of the packet 2029 protection AEAD to derive "sample", and then encrypts the header 2030 field using a pseudorandom function (PRF) as follows: 2032 protected_field = field XOR PRF(hp_key, sample) 2033 The header protection variants in this document use a pseudorandom 2034 permutation (PRP) in place of a generic PRF. However, since all PRPs 2035 are also PRFs [IMC], these variants do not deviate from the HN1 2036 construction. 2038 As "hp_key" is distinct from the packet protection key, it follows 2039 that header protection achieves AE2 security as defined in [NAN] and 2040 therefore guarantees privacy of "field", the protected packet header. 2041 Future header protection variants based on this construction MUST use 2042 a PRF to ensure equivalent security guarantees. 2044 Use of the same key and ciphertext sample more than once risks 2045 compromising header protection. Protecting two different headers 2046 with the same key and ciphertext sample reveals the exclusive OR of 2047 the protected fields. Assuming that the AEAD acts as a PRF, if L 2048 bits are sampled, the odds of two ciphertext samples being identical 2049 approach 2^(-L/2), that is, the birthday bound. For the algorithms 2050 described in this document, that probability is one in 2^64. 2052 To prevent an attacker from modifying packet headers, the header is 2053 transitively authenticated using packet protection; the entire packet 2054 header is part of the authenticated additional data. Protected 2055 fields that are falsified or modified can only be detected once the 2056 packet protection is removed. 2058 9.5. Header Protection Timing Side-Channels 2060 An attacker could guess values for packet numbers or Key Phase and 2061 have an endpoint confirm guesses through timing side channels. 2062 Similarly, guesses for the packet number length can be tried and 2063 exposed. If the recipient of a packet discards packets with 2064 duplicate packet numbers without attempting to remove packet 2065 protection they could reveal through timing side-channels that the 2066 packet number matches a received packet. For authentication to be 2067 free from side-channels, the entire process of header protection 2068 removal, packet number recovery, and packet protection removal MUST 2069 be applied together without timing and other side-channels. 2071 For the sending of packets, construction and protection of packet 2072 payloads and packet numbers MUST be free from side-channels that 2073 would reveal the packet number or its encoded size. 2075 During a key update, the time taken to generate new keys could reveal 2076 through timing side-channels that a key update has occurred. 2077 Alternatively, where an attacker injects packets this side-channel 2078 could reveal the value of the Key Phase on injected packets. After 2079 receiving a key update, an endpoint SHOULD generate and save the next 2080 set of receive packet protection keys, as described in Section 6.3. 2082 By generating new keys before a key update is received, receipt of 2083 packets will not create timing signals that leak the value of the Key 2084 Phase. 2086 This depends on not doing this key generation during packet 2087 processing and it can require that endpoints maintain three sets of 2088 packet protection keys for receiving: for the previous key phase, for 2089 the current key phase, and for the next key phase. Endpoints can 2090 instead choose to defer generation of the next receive packet 2091 protection keys until they discard old keys so that only two sets of 2092 receive keys need to be retained at any point in time. 2094 9.6. Key Diversity 2096 In using TLS, the central key schedule of TLS is used. As a result 2097 of the TLS handshake messages being integrated into the calculation 2098 of secrets, the inclusion of the QUIC transport parameters extension 2099 ensures that handshake and 1-RTT keys are not the same as those that 2100 might be produced by a server running TLS over TCP. To avoid the 2101 possibility of cross-protocol key synchronization, additional 2102 measures are provided to improve key separation. 2104 The QUIC packet protection keys and IVs are derived using a different 2105 label than the equivalent keys in TLS. 2107 To preserve this separation, a new version of QUIC SHOULD define new 2108 labels for key derivation for packet protection key and IV, plus the 2109 header protection keys. This version of QUIC uses the string "quic". 2110 Other versions can use a version-specific label in place of that 2111 string. 2113 The initial secrets use a key that is specific to the negotiated QUIC 2114 version. New QUIC versions SHOULD define a new salt value used in 2115 calculating initial secrets. 2117 10. IANA Considerations 2119 This document registers the quic_transport_parameters extension found 2120 in Section 8.2 in the TLS ExtensionType Values Registry 2121 [TLS-REGISTRIES]. 2123 The Recommended column is to be marked Yes. The TLS 1.3 Column is to 2124 include CH and EE. 2126 11. References 2128 11.1. Normative References 2130 [AEAD] McGrew, D., "An Interface and Algorithms for Authenticated 2131 Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, 2132 . 2134 [AES] "Advanced encryption standard (AES)", National Institute 2135 of Standards and Technology report, 2136 DOI 10.6028/nist.fips.197, November 2001, 2137 . 2139 [ALPN] Friedl, S., Popov, A., Langley, A., and E. Stephan, 2140 "Transport Layer Security (TLS) Application-Layer Protocol 2141 Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, 2142 July 2014, . 2144 [CHACHA] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF 2145 Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018, 2146 . 2148 [HKDF] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand 2149 Key Derivation Function (HKDF)", RFC 5869, 2150 DOI 10.17487/RFC5869, May 2010, 2151 . 2153 [QUIC-RECOVERY] 2154 Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection 2155 and Congestion Control", Work in Progress, Internet-Draft, 2156 draft-ietf-quic-recovery-32, 20 October 2020, 2157 . 2159 [QUIC-TRANSPORT] 2160 Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based 2161 Multiplexed and Secure Transport", Work in Progress, 2162 Internet-Draft, draft-ietf-quic-transport-32, 20 October 2163 2020, . 2166 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2167 Requirement Levels", BCP 14, RFC 2119, 2168 DOI 10.17487/RFC2119, March 1997, 2169 . 2171 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2172 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2173 May 2017, . 2175 [SHA] Dang, Q., "Secure Hash Standard", National Institute of 2176 Standards and Technology report, 2177 DOI 10.6028/nist.fips.180-4, July 2015, 2178 . 2180 [TLS-REGISTRIES] 2181 Salowey, J. and S. Turner, "IANA Registry Updates for TLS 2182 and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018, 2183 . 2185 [TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol 2186 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 2187 . 2189 11.2. Informative References 2191 [AEBounds] Luykx, A. and K. Paterson, "Limits on Authenticated 2192 Encryption Use in TLS", 8 March 2016, 2193 . 2195 [ASCII] Cerf, V., "ASCII format for network interchange", STD 80, 2196 RFC 20, DOI 10.17487/RFC0020, October 1969, 2197 . 2199 [CCM-ANALYSIS] 2200 Jonsson, J., "On the Security of CTR + CBC-MAC", Selected 2201 Areas in Cryptography pp. 76-93, 2202 DOI 10.1007/3-540-36492-7_7, 2003, 2203 . 2205 [COMPRESS] Ghedini, A. and V. Vasiliev, "TLS Certificate 2206 Compression", Work in Progress, Internet-Draft, draft- 2207 ietf-tls-certificate-compression-10, 6 January 2020, 2208 . 2211 [GCM-MU] Hoang, V., Tessaro, S., and A. Thiruvengadam, "The Multi- 2212 user Security of GCM, Revisited", Proceedings of the 2018 2213 ACM SIGSAC Conference on Computer and 2214 Communications Security, DOI 10.1145/3243734.3243816, 2215 January 2018, . 2217 [HTTP2-TLS13] 2218 Benjamin, D., "Using TLS 1.3 with HTTP/2", RFC 8740, 2219 DOI 10.17487/RFC8740, February 2020, 2220 . 2222 [IMC] Katz, J. and Y. Lindell, "Introduction to Modern 2223 Cryptography, Second Edition", ISBN 978-1466570269, 6 2224 November 2014. 2226 [NAN] Bellare, M., Ng, R., and B. Tackmann, "Nonces Are Noticed: 2227 AEAD Revisited", Advances in Cryptology - CRYPTO 2019 pp. 2228 235-265, DOI 10.1007/978-3-030-26948-7_9, 2019, 2229 . 2231 [QUIC-HTTP] 2232 Bishop, M., Ed., "Hypertext Transfer Protocol Version 3 2233 (HTTP/3)", Work in Progress, Internet-Draft, draft-ietf- 2234 quic-http-32, 20 October 2020, 2235 . 2237 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 2238 DOI 10.17487/RFC2818, May 2000, 2239 . 2241 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 2242 Housley, R., and W. Polk, "Internet X.509 Public Key 2243 Infrastructure Certificate and Certificate Revocation List 2244 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 2245 . 2247 [ROBUST] Fischlin, M., Günther, F., and C. Janson, "Robust 2248 Channels: Handling Unreliable Networks in the Record 2249 Layers of QUIC and DTLS 1.3", 16 May 2020, 2250 . 2252 Appendix A. Sample Packet Protection 2254 This section shows examples of packet protection so that 2255 implementations can be verified incrementally. Samples of Initial 2256 packets from both client and server, plus a Retry packet are defined. 2257 These packets use an 8-byte client-chosen Destination Connection ID 2258 of 0x8394c8f03e515708. Some intermediate values are included. All 2259 values are shown in hexadecimal. 2261 A.1. Keys 2263 The labels generated by the HKDF-Expand-Label function are: 2265 client in: 00200f746c73313320636c69656e7420696e00 2267 server in: 00200f746c7331332073657276657220696e00 2269 quic key: 00100e746c7331332071756963206b657900 2270 quic iv: 000c0d746c733133207175696320697600 2272 quic hp: 00100d746c733133207175696320687000 2274 The initial secret is common: 2276 initial_secret = HKDF-Extract(initial_salt, cid) 2277 = 1e7e7764529715b1e0ddc8e9753c6157 2278 6769605187793ed366f8bbf8c9e986eb 2280 The secrets for protecting client packets are: 2282 client_initial_secret 2283 = HKDF-Expand-Label(initial_secret, "client in", _, 32) 2284 = 0088119288f1d866733ceeed15ff9d50 2285 902cf82952eee27e9d4d4918ea371d87 2287 key = HKDF-Expand-Label(client_initial_secret, "quic key", _, 16) 2288 = 175257a31eb09dea9366d8bb79ad80ba 2290 iv = HKDF-Expand-Label(client_initial_secret, "quic iv", _, 12) 2291 = 6b26114b9cba2b63a9e8dd4f 2293 hp = HKDF-Expand-Label(client_initial_secret, "quic hp", _, 16) 2294 = 9ddd12c994c0698b89374a9c077a3077 2296 The secrets for protecting server packets are: 2298 server_initial_secret 2299 = HKDF-Expand-Label(initial_secret, "server in", _, 32) 2300 = 006f881359244dd9ad1acf85f595bad6 2301 7c13f9f5586f5e64e1acae1d9ea8f616 2303 key = HKDF-Expand-Label(server_initial_secret, "quic key", _, 16) 2304 = 149d0b1662ab871fbe63c49b5e655a5d 2306 iv = HKDF-Expand-Label(server_initial_secret, "quic iv", _, 12) 2307 = bab2b12a4c76016ace47856d 2309 hp = HKDF-Expand-Label(server_initial_secret, "quic hp", _, 16) 2310 = c0c499a65a60024a18a250974ea01dfa 2312 A.2. Client Initial 2314 The client sends an Initial packet. The unprotected payload of this 2315 packet contains the following CRYPTO frame, plus enough PADDING 2316 frames to make a 1162 byte payload: 2318 060040f1010000ed0303ebf8fa56f129 39b9584a3896472ec40bb863cfd3e868 2319 04fe3a47f06a2b69484c000004130113 02010000c000000010000e00000b6578 2320 616d706c652e636f6dff01000100000a 00080006001d00170018001000070005 2321 04616c706e0005000501000000000033 00260024001d00209370b2c9caa47fba 2322 baf4559fedba753de171fa71f50f1ce1 5d43e994ec74d748002b000302030400 2323 0d0010000e0403050306030203080408 050806002d00020101001c00024001ff 2324 a500320408ffffffffffffffff050480 00ffff07048000ffff08011001048000 2325 75300901100f088394c8f03e51570806 048000ffff 2327 The unprotected header includes the connection ID and a 4-byte packet 2328 number encoding for a packet number of 2: 2330 c3ff000020088394c8f03e5157080000449e00000002 2332 Protecting the payload produces output that is sampled for header 2333 protection. Because the header uses a 4-byte packet number encoding, 2334 the first 16 bytes of the protected payload is sampled, then applied 2335 to the header: 2337 sample = fb66bc6a93032b50dd8973972d149421 2339 mask = AES-ECB(hp, sample)[0..4] 2340 = 1e9cdb9909 2342 header[0] ^= mask[0] & 0x0f 2343 = cd 2344 header[18..21] ^= mask[1..4] 2345 = 9cdb990b 2346 header = cdff000020088394c8f03e5157080000449e9cdb990b 2348 The resulting protected packet is: 2350 cdff000020088394c8f03e5157080000 449e9cdb990bfb66bc6a93032b50dd89 2351 73972d149421874d3849e3708d71354e a33bcdc356f3ea6e2a1a1bd7c3d14003 2352 8d3e784d04c30a2cdb40c32523aba2da fe1c1bf3d27a6be38fe38ae033fbb071 2353 3c1c73661bb6639795b42b97f77068ea d51f11fbf9489af2501d09481e6c64d4 2354 b8551cd3cea70d830ce2aeeec789ef55 1a7fbe36b3f7e1549a9f8d8e153b3fac 2355 3fb7b7812c9ed7c20b4be190ebd89956 26e7f0fc887925ec6f0606c5d36aa81b 2356 ebb7aacdc4a31bb5f23d55faef5c5190 5783384f375a43235b5c742c78ab1bae 2357 0a188b75efbde6b3774ed61282f9670a 9dea19e1566103ce675ab4e21081fb58 2358 60340a1e88e4f10e39eae25cd685b109 29636d4f02e7fad2a5a458249f5c0298 2359 a6d53acbe41a7fc83fa7cc01973f7a74 d1237a51974e097636b6203997f921d0 2360 7bc1940a6f2d0de9f5a11432946159ed 6cc21df65c4ddd1115f86427259a196c 2361 7148b25b6478b0dc7766e1c4d1b1f515 9f90eabc61636226244642ee148b464c 2362 9e619ee50a5e3ddc836227cad938987c 4ea3c1fa7c75bbf88d89e9ada642b2b8 2363 8fe8107b7ea375b1b64889a4e9e5c38a 1c896ce275a5658d250e2d76e1ed3a34 2364 ce7e3a3f383d0c996d0bed106c2899ca 6fc263ef0455e74bb6ac1640ea7bfedc 2365 59f03fee0e1725ea150ff4d69a7660c5 542119c71de270ae7c3ecfd1af2c4ce5 2366 51986949cc34a66b3e216bfe18b347e6 c05fd050f85912db303a8f054ec23e38 2367 f44d1c725ab641ae929fecc8e3cefa56 19df4231f5b4c009fa0c0bbc60bc75f7 2368 6d06ef154fc8577077d9d6a1d2bd9bf0 81dc783ece60111bea7da9e5a9748069 2369 d078b2bef48de04cabe3755b197d52b3 2046949ecaa310274b4aac0d008b1948 2370 c1082cdfe2083e386d4fd84c0ed0666d 3ee26c4515c4fee73433ac703b690a9f 2371 7bf278a77486ace44c489a0c7ac8dfe4 d1a58fb3a730b993ff0f0d61b4d89557 2372 831eb4c752ffd39c10f6b9f46d8db278 da624fd800e4af85548a294c1518893a 2373 8778c4f6d6d73c93df200960104e062b 388ea97dcf4016bced7f62b4f062cb6c 2374 04c20693d9a0e3b74ba8fe74cc012378 84f40d765ae56a51688d985cf0ceaef4 2375 3045ed8c3f0c33bced08537f6882613a cd3b08d665fce9dd8aa73171e2d3771a 2376 61dba2790e491d413d93d987e2745af2 9418e428be34941485c93447520ffe23 2377 1da2304d6a0fd5d07d08372202369661 59bef3cf904d722324dd852513df39ae 2378 030d8173908da6364786d3c1bfcb19ea 77a63b25f1e7fc661def480c5d00d444 2379 56269ebd84efd8e3a8b2c257eec76060 682848cbf5194bc99e49ee75e4d0d254 2380 bad4bfd74970c30e44b65511d4ad0e6e c7398e08e01307eeeea14e46ccd87cf3 2381 6b285221254d8fc6a6765c524ded0085 dca5bd688ddf722e2c0faf9d0fb2ce7a 2382 0c3f2cee19ca0ffba461ca8dc5d2c817 8b0762cf67135558494d2a96f1a139f0 2383 edb42d2af89a9c9122b07acbc29e5e72 2df8615c343702491098478a389c9872 2384 a10b0c9875125e257c7bfdf27eef4060 bd3d00f4c14fd3e3496c38d3c5d1a566 2385 8c39350effbc2d16ca17be4ce29f02ed 969504dda2a8c6b9ff919e693ee79e09 2386 089316e7d1d89ec099db3b2b268725d8 88536a4b8bf9aee8fb43e82a4d919d48 2387 b5a464ca5b62df3be35ee0d0a2ec68f3 2389 A.3. Server Initial 2391 The server sends the following payload in response, including an ACK 2392 frame, a CRYPTO frame, and no PADDING frames: 2394 02000000000600405a020000560303ee fce7f7b37ba1d1632e96677825ddf739 2395 88cfc79825df566dc5430b9a045a1200 130100002e00330024001d00209d3c94 2396 0d89690b84d08a60993c144eca684d10 81287c834d5311bcf32bb9da1a002b00 2397 020304 2398 The header from the server includes a new connection ID and a 2-byte 2399 packet number encoding for a packet number of 1: 2401 c1ff0000200008f067a5502a4262b50040750001 2403 As a result, after protection, the header protection sample is taken 2404 starting from the third protected octet: 2406 sample = 823a5d24534d906ce4c76782a2167e34 2407 mask = abaaf34fdc 2408 header = c7ff0000200008f067a5502a4262b5004075fb12 2410 The final protected packet is then: 2412 c7ff0000200008f067a5502a4262b500 4075fb12ff07823a5d24534d906ce4c7 2413 6782a2167e3479c0f7f6395dc2c91676 302fe6d70bb7cbeb117b4ddb7d173498 2414 44fd61dae200b8338e1b932976b61d91 e64a02e9e0ee72e3a6f63aba4ceeeec5 2415 be2f24f2d86027572943533846caa13e 6f163fb257473d0eda5047360fd4a47e 2416 fd8142fafc0f76 2418 A.4. Retry 2420 This shows a Retry packet that might be sent in response to the 2421 Initial packet in Appendix A.2. The integrity check includes the 2422 client-chosen connection ID value of 0x8394c8f03e515708, but that 2423 value is not included in the final Retry packet: 2425 ffff0000200008f067a5502a4262b574 6f6b656e59756519dd6cc85bd90e33a9 2426 34d2ff85 2428 A.5. ChaCha20-Poly1305 Short Header Packet 2430 This example shows some of the steps required to protect a packet 2431 with a short header. This example uses AEAD_CHACHA20_POLY1305. 2433 In this example, TLS produces an application write secret from which 2434 a server uses HKDF-Expand-Label to produce four values: a key, an IV, 2435 a header protection key, and the secret that will be used after keys 2436 are updated (this last value is not used further in this example). 2438 secret 2439 = 9ac312a7f877468ebe69422748ad00a1 2440 5443f18203a07d6060f688f30f21632b 2442 key = HKDF-Expand-Label(secret, "quic key", _, 32) 2443 = c6d98ff3441c3fe1b2182094f69caa2e 2444 d4b716b65488960a7a984979fb23e1c8 2446 iv = HKDF-Expand-Label(secret, "quic iv", _, 12) 2447 = e0459b3474bdd0e44a41c144 2449 hp = HKDF-Expand-Label(secret, "quic hp", _, 32) 2450 = 25a282b9e82f06f21f488917a4fc8f1b 2451 73573685608597d0efcb076b0ab7a7a4 2453 ku = HKDF-Expand-Label(secret, "quic ku", _, 32) 2454 = 1223504755036d556342ee9361d25342 2455 1a826c9ecdf3c7148684b36b714881f9 2457 The following shows the steps involved in protecting a minimal packet 2458 with an empty Destination Connection ID. This packet contains a 2459 single PING frame (that is, a payload of just 0x01) and has a packet 2460 number of 654360564. In this example, using a packet number of 2461 length 3 (that is, 49140 is encoded) avoids having to pad the payload 2462 of the packet; PADDING frames would be needed if the packet number is 2463 encoded on fewer octets. 2465 pn = 654360564 (decimal) 2466 nonce = e0459b3474bdd0e46d417eb0 2467 unprotected header = 4200bff4 2468 payload plaintext = 01 2469 payload ciphertext = 655e5cd55c41f69080575d7999c25a5bfb 2471 The resulting ciphertext is the minimum size possible. One byte is 2472 skipped to produce the sample for header protection. 2474 sample = 5e5cd55c41f69080575d7999c25a5bfb 2475 mask = aefefe7d03 2476 header = 4cfe4189 2478 The protected packet is the smallest possible packet size of 21 2479 bytes. 2481 packet = 4cfe4189655e5cd55c41f69080575d7999c25a5bfb 2483 Appendix B. AEAD Algorithm Analysis 2485 This section documents analyses used in deriving AEAD algorithm 2486 limits for AEAD_AES_128_GCM, AEAD_AES_128_CCM, and AEAD_AES_256_GCM. 2487 The analyses that follow use symbols for multiplication (*), division 2488 (/), and exponentiation (^), plus parentheses for establishing 2489 precedence. The following symbols are also used: 2491 t: The size of the authentication tag in bits. For these ciphers, t 2492 is 128. 2494 n: The size of the block function in bits. For these ciphers, n is 2495 128. 2497 k: The size of the key in bits. This is 128 for AEAD_AES_128_GCM 2498 and AEAD_AES_128_CCM; 256 for AEAD_AES_256_GCM. 2500 l: The number of blocks in each packet (see below). 2502 q: The number of genuine packets created and protected by endpoints. 2503 This value is the bound on the number of packets that can be 2504 protected before updating keys. 2506 v: The number of forged packets that endpoints will accept. This 2507 value is the bound on the number of forged packets that an 2508 endpoint can reject before updating keys. 2510 o: The amount of offline ideal cipher queries made by an adversary. 2512 The analyses that follow rely on a count of the number of block 2513 operations involved in producing each message. This analysis is 2514 performed for packets of size up to 2^11 (l = 2^7) and 2^16 (l = 2515 2^12). A size of 2^11 is expected to be a limit that matches common 2516 deployment patterns, whereas the 2^16 is the maximum possible size of 2517 a QUIC packet. Only endpoints that strictly limit packet size can 2518 use the larger confidentiality and integrity limits that are derived 2519 using the smaller packet size. 2521 For AEAD_AES_128_GCM and AEAD_AES_256_GCM, the message length (l) is 2522 the length of the associated data in blocks plus the length of the 2523 plaintext in blocks. 2525 For AEAD_AES_128_CCM, the total number of block cipher operations is 2526 the sum of: the length of the associated data in blocks, the length 2527 of the ciphertext in blocks, the length of the plaintext in blocks, 2528 plus 1. In this analysis, this is simplified to a value of twice the 2529 length of the packet in blocks (that is, "2l = 2^8" for packets that 2530 are limited to 2^11 bytes, or "2l = 2^13" otherwise). This 2531 simplification is based on the packet containing all of the 2532 associated data and ciphertext. This results in a 1 to 3 block 2533 overestimation of the number of operations per packet. 2535 B.1. Analysis of AEAD_AES_128_GCM and AEAD_AES_256_GCM Usage Limits 2537 [GCM-MU] specify concrete bounds for AEAD_AES_128_GCM and 2538 AEAD_AES_256_GCM as used in TLS 1.3 and QUIC. This section documents 2539 this analysis using several simplifying assumptions: 2541 * The number of ciphertext blocks an attacker uses in forgery 2542 attempts is bounded by v * l, the number of forgery attempts and 2543 the size of each packet (in blocks). 2545 * The amount of offline work done by an attacker does not dominate 2546 other factors in the analysis. 2548 The bounds in [GCM-MU] are tighter and more complete than those used 2549 in [AEBounds], which allows for larger limits than those described in 2550 [TLS13]. 2552 B.1.1. Confidentiality Limit 2554 For confidentiality, Theorum (4.3) in [GCM-MU] establishes that - for 2555 a single user that does not repeat nonces - the dominant term in 2556 determining the distinguishing advantage between a real and random 2557 AEAD algorithm gained by an attacker is: 2559 2 * (q * l)^2 / 2^n 2561 For a target advantage of 2^-57, this results in the relation: 2563 q <= 2^35 / l 2565 Thus, endpoints that do not send packets larger than 2^11 bytes 2566 cannot protect more than 2^28 packets in a single connection without 2567 causing an attacker to gain an larger advantage than the target of 2568 2^-57. The limit for endpoints that allow for the packet size to be 2569 as large as 2^16 is instead 2^23. 2571 B.1.2. Integrity Limit 2573 For integrity, Theorem (4.3) in [GCM-MU] establishes that an attacker 2574 gains an advantage in successfully forging a packet of no more than: 2576 (1 / 2^(8 * n)) + ((2 * v) / 2^(2 * n)) 2577 + ((2 * o * v) / 2^(k + n)) + (n * (v + (v * l)) / 2^k) 2579 The goal is to limit this advantage to 2^-57. For AEAD_AES_128_GCM, 2580 the fourth term in this inequality dominates the rest, so the others 2581 can be removed without significant effect on the result. This 2582 produces the following approximation: 2584 v <= 2^64 / l 2586 Endpoints that do not attempt to remove protection from packets 2587 larger than 2^11 bytes can attempt to remove protection from at most 2588 2^57 packets. Endpoints that do not restrict the size of processed 2589 packets can attempt to remove protection from at most 2^52 packets. 2591 For AEAD_AES_256_GCM, the same term dominates, but the larger value 2592 of k produces the following approximation: 2594 v <= 2^192 / l 2596 This is substantially larger than the limit for AEAD_AES_128_GCM. 2597 However, this document recommends that the same limit be applied to 2598 both functions as either limit is acceptably large. 2600 B.2. Analysis of AEAD_AES_128_CCM Usage Limits 2602 TLS [TLS13] and [AEBounds] do not specify limits on usage for 2603 AEAD_AES_128_CCM. However, any AEAD that is used with QUIC requires 2604 limits on use that ensure that both confidentiality and integrity are 2605 preserved. This section documents that analysis. 2607 [CCM-ANALYSIS] is used as the basis of this analysis. The results of 2608 that analysis are used to derive usage limits that are based on those 2609 chosen in [TLS13]. 2611 For confidentiality, Theorem 2 in [CCM-ANALYSIS] establishes that an 2612 attacker gains a distinguishing advantage over an ideal pseudorandom 2613 permutation (PRP) of no more than: 2615 (2l * q)^2 / 2^n 2617 The integrity limit in Theorem 1 in [CCM-ANALYSIS] provides an 2618 attacker a strictly higher advantage for the same number of messages. 2619 As the targets for the confidentiality advantage and the integrity 2620 advantage are the same, only Theorem 1 needs to be considered. 2622 Theorem 1 establishes that an attacker gains an advantage over an 2623 ideal PRP of no more than: 2625 v / 2^t + (2l * (v + q))^2 / 2^n 2626 As "t" and "n" are both 128, the first term is negligible relative to 2627 the second, so that term can be removed without a significant effect 2628 on the result. 2630 This produces a relation that combines both encryption and decryption 2631 attempts with the same limit as that produced by the theorem for 2632 confidentiality alone. For a target advantage of 2^-57, this results 2633 in: 2635 v + q <= 2^34.5 / l 2637 By setting "q = v", values for both confidentiality and integrity 2638 limits can be produced. Endpoints that limit packets to 2^11 bytes 2639 therefore have both confidentiality and integrity limits of 2^26.5 2640 packets. Endpoints that do not restrict packet size have a limit of 2641 2^21.5. 2643 Appendix C. Change Log 2645 *RFC Editor's Note:* Please remove this section prior to 2646 publication of a final version of this document. 2648 Issue and pull request numbers are listed with a leading octothorp. 2650 C.1. Since draft-ietf-quic-tls-31 2652 * Packet protection limits are based on maximum-sized packets; 2653 improved analysis (#3701, #4175) 2655 C.2. Since draft-ietf-quic-tls-30 2657 * Add a new error code for AEAD_LIMIT_REACHED code to avoid conflict 2658 (#4087, #4088) 2660 C.3. Since draft-ietf-quic-tls-29 2662 * Updated limits on packet protection (#3788, #3789) 2664 * Allow for packet processing to continue while waiting for TLS to 2665 provide keys (#3821, #3874) 2667 C.4. Since draft-ietf-quic-tls-28 2669 * Defined limits on the number of packets that can be protected with 2670 a single key and limits on the number of packets that can fail 2671 authentication (#3619, #3620) 2673 * Update Initial salt, Retry keys, and samples (#3711) 2675 C.5. Since draft-ietf-quic-tls-27 2677 * Allowed CONNECTION_CLOSE in any packet number space, with 2678 restrictions on use of the application-specific variant (#3430, 2679 #3435, #3440) 2681 * Prohibit the use of the compatibility mode from TLS 1.3 (#3594, 2682 #3595) 2684 C.6. Since draft-ietf-quic-tls-26 2686 * No changes 2688 C.7. Since draft-ietf-quic-tls-25 2690 * No changes 2692 C.8. Since draft-ietf-quic-tls-24 2694 * Rewrite key updates (#3050) 2696 - Allow but don't recommend deferring key updates (#2792, #3263) 2698 - More completely define received behavior (#2791) 2700 - Define the label used with HKDF-Expand-Label (#3054) 2702 C.9. Since draft-ietf-quic-tls-23 2704 * Key update text update (#3050): 2706 - Recommend constant-time key replacement (#2792) 2708 - Provide explicit labels for key update key derivation (#3054) 2710 * Allow first Initial from a client to span multiple packets (#2928, 2711 #3045) 2713 * PING can be sent at any encryption level (#3034, #3035) 2715 C.10. Since draft-ietf-quic-tls-22 2717 * Update the salt used for Initial secrets (#2887, #2980) 2719 C.11. Since draft-ietf-quic-tls-21 2721 * No changes 2723 C.12. Since draft-ietf-quic-tls-20 2725 * Mandate the use of the QUIC transport parameters extension (#2528, 2726 #2560) 2728 * Define handshake completion and confirmation; define clearer rules 2729 when it encryption keys should be discarded (#2214, #2267, #2673) 2731 C.13. Since draft-ietf-quic-tls-18 2733 * Increased the set of permissible frames in 0-RTT (#2344, #2355) 2735 * Transport parameter extension is mandatory (#2528, #2560) 2737 C.14. Since draft-ietf-quic-tls-17 2739 * Endpoints discard initial keys as soon as handshake keys are 2740 available (#1951, #2045) 2742 * Use of ALPN or equivalent is mandatory (#2263, #2284) 2744 C.15. Since draft-ietf-quic-tls-14 2746 * Update the salt used for Initial secrets (#1970) 2748 * Clarify that TLS_AES_128_CCM_8_SHA256 isn't supported (#2019) 2750 * Change header protection 2752 - Sample from a fixed offset (#1575, #2030) 2754 - Cover part of the first byte, including the key phase (#1322, 2755 #2006) 2757 * TLS provides an AEAD and KDF function (#2046) 2759 - Clarify that the TLS KDF is used with TLS (#1997) 2761 - Change the labels for calculation of QUIC keys (#1845, #1971, 2762 #1991) 2764 * Initial keys are discarded once Handshake keys are available 2765 (#1951, #2045) 2767 C.16. Since draft-ietf-quic-tls-13 2769 * Updated to TLS 1.3 final (#1660) 2771 C.17. Since draft-ietf-quic-tls-12 2773 * Changes to integration of the TLS handshake (#829, #1018, #1094, 2774 #1165, #1190, #1233, #1242, #1252, #1450) 2776 - The cryptographic handshake uses CRYPTO frames, not stream 0 2778 - QUIC packet protection is used in place of TLS record 2779 protection 2781 - Separate QUIC packet number spaces are used for the handshake 2783 - Changed Retry to be independent of the cryptographic handshake 2785 - Limit the use of HelloRetryRequest to address TLS needs (like 2786 key shares) 2788 * Changed codepoint of TLS extension (#1395, #1402) 2790 C.18. Since draft-ietf-quic-tls-11 2792 * Encrypted packet numbers. 2794 C.19. Since draft-ietf-quic-tls-10 2796 * No significant changes. 2798 C.20. Since draft-ietf-quic-tls-09 2800 * Cleaned up key schedule and updated the salt used for handshake 2801 packet protection (#1077) 2803 C.21. Since draft-ietf-quic-tls-08 2805 * Specify value for max_early_data_size to enable 0-RTT (#942) 2807 * Update key derivation function (#1003, #1004) 2809 C.22. Since draft-ietf-quic-tls-07 2811 * Handshake errors can be reported with CONNECTION_CLOSE (#608, 2812 #891) 2814 C.23. Since draft-ietf-quic-tls-05 2816 No significant changes. 2818 C.24. Since draft-ietf-quic-tls-04 2820 * Update labels used in HKDF-Expand-Label to match TLS 1.3 (#642) 2822 C.25. Since draft-ietf-quic-tls-03 2824 No significant changes. 2826 C.26. Since draft-ietf-quic-tls-02 2828 * Updates to match changes in transport draft 2830 C.27. Since draft-ietf-quic-tls-01 2832 * Use TLS alerts to signal TLS errors (#272, #374) 2834 * Require ClientHello to fit in a single packet (#338) 2836 * The second client handshake flight is now sent in the clear (#262, 2837 #337) 2839 * The QUIC header is included as AEAD Associated Data (#226, #243, 2840 #302) 2842 * Add interface necessary for client address validation (#275) 2844 * Define peer authentication (#140) 2846 * Require at least TLS 1.3 (#138) 2848 * Define transport parameters as a TLS extension (#122) 2850 * Define handling for protected packets before the handshake 2851 completes (#39) 2853 * Decouple QUIC version and ALPN (#12) 2855 C.28. Since draft-ietf-quic-tls-00 2857 * Changed bit used to signal key phase 2859 * Updated key phase markings during the handshake 2861 * Added TLS interface requirements section 2863 * Moved to use of TLS exporters for key derivation 2865 * Moved TLS error code definitions into this document 2867 C.29. Since draft-thomson-quic-tls-01 2869 * Adopted as base for draft-ietf-quic-tls 2871 * Updated authors/editors list 2873 * Added status note 2875 Contributors 2877 The IETF QUIC Working Group received an enormous amount of support 2878 from many people. The following people provided substantive 2879 contributions to this document: 2881 * Adam Langley 2883 * Alessandro Ghedini 2885 * Christian Huitema 2887 * Christopher Wood 2889 * David Schinazi 2891 * Dragana Damjanovic 2893 * Eric Rescorla 2895 * Felix Guenther 2897 * Ian Swett 2899 * Jana Iyengar 2901 * 奥 一穂 (Kazuho Oku) 2903 * Marten Seemann 2905 * Martin Duke 2907 * Mike Bishop 2909 * Mikkel Fahnøe Jørgensen 2911 * Nick Banks 2913 * Nick Harper 2914 * Roberto Peon 2916 * Rui Paulo 2918 * Ryan Hamilton 2920 * Victor Vasiliev 2922 Authors' Addresses 2924 Martin Thomson (editor) 2925 Mozilla 2927 Email: mt@lowentropy.net 2929 Sean Turner (editor) 2930 sn3rd 2932 Email: sean@sn3rd.com