1 /* 2 * Copyright 2022-2025 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 #ifndef OSSL_QUIC_RECORD_RX_H 11 # define OSSL_QUIC_RECORD_RX_H 12 13 # include <openssl/ssl.h> 14 # include "internal/quic_wire_pkt.h" 15 # include "internal/quic_types.h" 16 # include "internal/quic_predef.h" 17 # include "internal/quic_record_util.h" 18 # include "internal/quic_demux.h" 19 20 # ifndef OPENSSL_NO_QUIC 21 22 /* 23 * QUIC Record Layer - RX 24 * ====================== 25 */ 26 27 typedef struct ossl_qrx_args_st { 28 OSSL_LIB_CTX *libctx; 29 const char *propq; 30 31 /* Demux which owns the URXEs passed to us. */ 32 QUIC_DEMUX *demux; 33 34 /* Length of connection IDs used in short-header packets in bytes. */ 35 size_t short_conn_id_len; 36 37 /* 38 * Maximum number of deferred datagrams buffered at any one time. 39 * Suggested value: 32. 40 */ 41 size_t max_deferred; 42 43 /* Initial reference PN used for RX. */ 44 QUIC_PN init_largest_pn[QUIC_PN_SPACE_NUM]; 45 46 /* Initial key phase. For debugging use only; always 0 in real use. */ 47 unsigned char init_key_phase_bit; 48 } OSSL_QRX_ARGS; 49 50 /* Instantiates a new QRX. */ 51 OSSL_QRX *ossl_qrx_new(const OSSL_QRX_ARGS *args); 52 53 /* 54 * Frees the QRX. All packets obtained using ossl_qrx_read_pkt must already 55 * have been released by calling ossl_qrx_release_pkt. 56 * 57 * You do not need to call ossl_qrx_remove_dst_conn_id first; this function will 58 * unregister the QRX from the demuxer for all registered destination connection 59 * IDs (DCIDs) automatically. 60 */ 61 void ossl_qrx_free(OSSL_QRX *qrx); 62 63 /* Setters for the msg_callback and msg_callback_arg */ 64 void ossl_qrx_set_msg_callback(OSSL_QRX *qrx, ossl_msg_cb msg_callback, 65 SSL *msg_callback_ssl); 66 void ossl_qrx_set_msg_callback_arg(OSSL_QRX *qrx, 67 void *msg_callback_arg); 68 69 /* 70 * Get the short header connection id len from this qrx 71 */ 72 size_t ossl_qrx_get_short_hdr_conn_id_len(OSSL_QRX *qrx); 73 74 /* 75 * Secret Management 76 * ================= 77 * 78 * A QRX has several encryption levels (Initial, Handshake, 0-RTT, 1-RTT) and 79 * two directions (RX, TX). At any given time, key material is managed for each 80 * (EL, RX/TX) combination. 81 * 82 * Broadly, for a given (EL, RX/TX), the following state machine is applicable: 83 * 84 * WAITING_FOR_KEYS --[Provide]--> HAVE_KEYS --[Discard]--> | DISCARDED | 85 * \-------------------------------------[Discard]--> | | 86 * 87 * To transition the RX side of an EL from WAITING_FOR_KEYS to HAVE_KEYS, call 88 * ossl_qrx_provide_secret (for the INITIAL EL, use of 89 * ossl_quic_provide_initial_secret is recommended). 90 * 91 * Once keys have been provisioned for an EL, you call 92 * ossl_qrx_discard_enc_level to transition the EL to the DISCARDED state. You 93 * can also call this function to transition directly to the DISCARDED state 94 * even before any keys have been provisioned for that EL. 95 * 96 * The DISCARDED state is terminal for a given EL; you cannot provide a secret 97 * again for that EL after reaching it. 98 * 99 * Incoming packets cannot be processed and decrypted if they target an EL 100 * not in the HAVE_KEYS state. However, there is a distinction between 101 * the WAITING_FOR_KEYS and DISCARDED states: 102 * 103 * - In the WAITING_FOR_KEYS state, the QRX assumes keys for the given 104 * EL will eventually arrive. Therefore, if it receives any packet 105 * for an EL in this state, it buffers it and tries to process it 106 * again once the EL reaches HAVE_KEYS. 107 * 108 * - In the DISCARDED state, the QRX assumes no keys for the given 109 * EL will ever arrive again. If it receives any packet for an EL 110 * in this state, it is simply discarded. 111 * 112 * If the user wishes to instantiate a new QRX to replace an old one for 113 * whatever reason, for example to take over for an already established QUIC 114 * connection, it is important that all ELs no longer being used (i.e., INITIAL, 115 * 0-RTT, 1-RTT) are transitioned to the DISCARDED state. Otherwise, the QRX 116 * will assume that keys for these ELs will arrive in future, and will buffer 117 * any received packets for those ELs perpetually. This can be done by calling 118 * ossl_qrx_discard_enc_level for all non-1-RTT ELs immediately after 119 * instantiating the QRX. 120 * 121 * The INITIAL EL is not setup automatically when the QRX is instantiated. This 122 * allows the caller to instead discard it immediately after instantiation of 123 * the QRX if it is not needed, for example if the QRX is being instantiated to 124 * take over handling of an existing connection which has already passed the 125 * INITIAL phase. This avoids the unnecessary derivation of INITIAL keys where 126 * they are not needed. In the ordinary case, ossl_quic_provide_initial_secret 127 * should be called immediately after instantiation. 128 */ 129 130 /* 131 * Provides a secret to the QRX, which arises due to an encryption level change. 132 * enc_level is a QUIC_ENC_LEVEL_* value. To initialise the INITIAL encryption 133 * level, it is recommended to use ossl_quic_provide_initial_secret instead. 134 * 135 * You should seek to call this function for a given EL before packets of that 136 * EL arrive and are processed by the QRX. However, if packets have already 137 * arrived for a given EL, the QRX will defer processing of them and perform 138 * processing of them when this function is eventually called for the EL in 139 * question. 140 * 141 * suite_id is a QRL_SUITE_* value which determines the AEAD function used for 142 * the QRX. 143 * 144 * The secret passed is used directly to derive the "quic key", "quic iv" and 145 * "quic hp" values. 146 * 147 * secret_len is the length of the secret buffer in bytes. The buffer must be 148 * sized correctly to the chosen suite, else the function fails. 149 * 150 * This function can only be called once for a given EL, except for the INITIAL 151 * EL, which can need rekeying when a connection retry occurs. Subsequent calls 152 * for non-INITIAL ELs fail, as do calls made after a corresponding call to 153 * ossl_qrx_discard_enc_level for that EL. The secret for a non-INITIAL EL 154 * cannot be changed after it is set because QUIC has no facility for 155 * introducing additional key material after an EL is setup. QUIC key updates 156 * are managed semi-automatically by the QRX but do require some caller handling 157 * (see below). 158 * 159 * md is for internal use and should be NULL. 160 * 161 * Returns 1 on success or 0 on failure. 162 */ 163 int ossl_qrx_provide_secret(OSSL_QRX *qrx, 164 uint32_t enc_level, 165 uint32_t suite_id, 166 EVP_MD *md, 167 const unsigned char *secret, 168 size_t secret_len); 169 170 /* 171 * Informs the QRX that it can now discard key material for a given EL. The QRX 172 * will no longer be able to process incoming packets received at that 173 * encryption level. This function is idempotent and succeeds if the EL has 174 * already been discarded. 175 * 176 * Returns 1 on success and 0 on failure. 177 */ 178 int ossl_qrx_discard_enc_level(OSSL_QRX *qrx, uint32_t enc_level); 179 180 /* 181 * Packet Reception 182 * ================ 183 */ 184 185 /* Information about a received packet. */ 186 struct ossl_qrx_pkt_st { 187 /* 188 * Points to a logical representation of the decoded QUIC packet header. The 189 * data and len fields point to the decrypted QUIC payload (i.e., to a 190 * sequence of zero or more (potentially malformed) frames to be decoded). 191 */ 192 QUIC_PKT_HDR *hdr; 193 194 /* 195 * Address the packet was received from. If this is not available for this 196 * packet, this field is NULL (but this can only occur for manually injected 197 * packets). 198 */ 199 const BIO_ADDR *peer; 200 201 /* 202 * Local address the packet was sent to. If this is not available for this 203 * packet, this field is NULL. 204 */ 205 const BIO_ADDR *local; 206 207 /* 208 * This is the length of the datagram which contained this packet. Note that 209 * the datagram may have contained other packets than this. The intended use 210 * for this is so that the user can enforce minimum datagram sizes (e.g. for 211 * datagrams containing INITIAL packets), as required by RFC 9000. 212 */ 213 size_t datagram_len; 214 215 /* The PN which was decoded for the packet, if the packet has a PN field. */ 216 QUIC_PN pn; 217 218 /* 219 * Time the packet was received, or ossl_time_zero() if the demuxer is not 220 * using a now() function. 221 */ 222 OSSL_TIME time; 223 224 /* The QRX which was used to receive the packet. */ 225 OSSL_QRX *qrx; 226 227 /* 228 * The key epoch the packet was received with. Always 0 for non-1-RTT 229 * packets. 230 */ 231 uint64_t key_epoch; 232 233 /* 234 * This monotonically increases with each datagram received. 235 * It is for diagnostic use only. 236 */ 237 uint64_t datagram_id; 238 }; 239 240 /* 241 * Tries to read a new decrypted packet from the QRX. 242 * 243 * On success, *pkt points to a OSSL_QRX_PKT structure. The structure should be 244 * freed when no longer needed by calling ossl_qrx_pkt_release(). The structure 245 * is refcounted; to gain extra references, call ossl_qrx_pkt_up_ref(). This 246 * will cause a corresponding number of calls to ossl_qrx_pkt_release() to be 247 * ignored. 248 * 249 * The resources referenced by (*pkt)->hdr, (*pkt)->hdr->data and (*pkt)->peer 250 * have the same lifetime as *pkt. 251 * 252 * Returns 1 on success and 0 on failure. 253 */ 254 int ossl_qrx_read_pkt(OSSL_QRX *qrx, OSSL_QRX_PKT **pkt); 255 256 /* 257 * Decrement the reference count for the given packet and frees it if the 258 * reference count drops to zero. No-op if pkt is NULL. 259 */ 260 void ossl_qrx_pkt_release(OSSL_QRX_PKT *pkt); 261 262 /* 263 * Like ossl_qrx_pkt_release, but just ensures that the refcount is dropped 264 * on this qrx_pkt, and ensure its not on any list 265 */ 266 void ossl_qrx_pkt_orphan(OSSL_QRX_PKT *pkt); 267 268 /* Increments the reference count for the given packet. */ 269 void ossl_qrx_pkt_up_ref(OSSL_QRX_PKT *pkt); 270 271 /* 272 * Returns 1 if there are any already processed (i.e. decrypted) packets waiting 273 * to be read from the QRX. 274 */ 275 int ossl_qrx_processed_read_pending(OSSL_QRX *qrx); 276 277 /* 278 * Returns 1 if there are any unprocessed (i.e. not yet decrypted) packets 279 * waiting to be processed by the QRX. These may or may not result in 280 * successfully decrypted packets once processed. This indicates whether 281 * unprocessed data is buffered by the QRX, not whether any data is available in 282 * a kernel socket buffer. 283 */ 284 int ossl_qrx_unprocessed_read_pending(OSSL_QRX *qrx); 285 286 /* 287 * Returns the number of UDP payload bytes received from the network so far 288 * since the last time this counter was cleared. If clear is 1, clears the 289 * counter and returns the old value. 290 * 291 * The intended use of this is to allow callers to determine how much credit to 292 * add to their anti-amplification budgets. This is reported separately instead 293 * of in the OSSL_QRX_PKT structure so that a caller can apply 294 * anti-amplification credit as soon as a datagram is received, before it has 295 * necessarily read all processed packets contained within that datagram from 296 * the QRX. 297 */ 298 uint64_t ossl_qrx_get_bytes_received(OSSL_QRX *qrx, int clear); 299 300 /* 301 * Sets a callback which is called when a packet is received and being validated 302 * before being queued in the read queue. This is called after packet body 303 * decryption and authentication to prevent exposing side channels. pn_space is 304 * a QUIC_PN_SPACE_* value denoting which PN space the PN belongs to. 305 * 306 * If this callback returns 1, processing continues normally. 307 * If this callback returns 0, the packet is discarded. 308 * 309 * Other packets in the same datagram will still be processed where possible. 310 * 311 * The callback is optional and can be unset by passing NULL for cb. 312 * cb_arg is an opaque value passed to cb. 313 */ 314 typedef int (ossl_qrx_late_validation_cb)(QUIC_PN pn, int pn_space, 315 void *arg); 316 317 int ossl_qrx_set_late_validation_cb(OSSL_QRX *qrx, 318 ossl_qrx_late_validation_cb *cb, 319 void *cb_arg); 320 321 /* 322 * Forcibly injects a URXE which has been issued by the DEMUX into the QRX for 323 * processing. This can be used to pass a received datagram to the QRX if it 324 * would not be correctly routed to the QRX via standard DCID-based routing; for 325 * example, when handling an incoming Initial packet which is attempting to 326 * establish a new connection. 327 */ 328 void ossl_qrx_inject_urxe(OSSL_QRX *qrx, QUIC_URXE *e); 329 void ossl_qrx_inject_pkt(OSSL_QRX *qrx, OSSL_QRX_PKT *pkt); 330 int ossl_qrx_validate_initial_packet(OSSL_QRX *qrx, QUIC_URXE *urxe, 331 const QUIC_CONN_ID *dcid); 332 333 /* 334 * Decryption of 1-RTT packets must be explicitly enabled by calling this 335 * function. This is to comply with the requirement that we not process 1-RTT 336 * packets until the handshake is complete, even if we already have 1-RTT 337 * secrets. Even if a 1-RTT secret is provisioned for the QRX, incoming 1-RTT 338 * packets will be handled as though no key is available until this function is 339 * called. Calling this function will then requeue any such deferred packets for 340 * processing. 341 */ 342 void ossl_qrx_allow_1rtt_processing(OSSL_QRX *qrx); 343 344 /* 345 * Key Update (RX) 346 * =============== 347 * 348 * Key update on the RX side is a largely but not entirely automatic process. 349 * 350 * Key update is initially triggered by receiving a 1-RTT packet with a 351 * different Key Phase value. This could be caused by an attacker in the network 352 * flipping random bits, therefore such a key update is tentative until the 353 * packet payload is successfully decrypted and authenticated by the AEAD with 354 * the 'next' keys. These 'next' keys then become the 'current' keys and the 355 * 'current' keys then become the 'previous' keys. The 'previous' keys must be 356 * kept around temporarily as some packets may still be in flight in the network 357 * encrypted with the old keys. If the old Key Phase value is X and the new Key 358 * Phase Value is Y (where obviously X != Y), this creates an ambiguity as any 359 * new packet received with a KP of X could either be an attempt to initiate yet 360 * another key update right after the last one, or an old packet encrypted 361 * before the key update. 362 * 363 * RFC 9001 provides some guidance on handling this issue: 364 * 365 * Strategy 1: 366 * Three keys, disambiguation using packet numbers 367 * 368 * "A recovered PN that is lower than any PN from the current KP uses the 369 * previous packet protection keys; a recovered PN that is higher than any 370 * PN from the current KP requires use of the next packet protection 371 * keys." 372 * 373 * Strategy 2: 374 * Two keys and a timer 375 * 376 * "Alternatively, endpoints can retain only two sets of packet protection 377 * keys, swapping previous keys for next after enough time has passed to 378 * allow for reordering in the network. In this case, the KP bit alone can 379 * be used to select keys." 380 * 381 * Strategy 2 is more efficient (we can keep fewer cipher contexts around) and 382 * should cover all actually possible network conditions. It also allows a delay 383 * after we make the 'next' keys our 'current' keys before we generate new 384 * 'next' keys, which allows us to mitigate against malicious peers who try to 385 * initiate an excessive number of key updates. 386 * 387 * We therefore model the following state machine: 388 * 389 * 390 * PROVISIONED 391 * _______________________________ 392 * | | 393 * UNPROVISIONED --|----> NORMAL <----------\ |------> DISCARDED 394 * | | | | 395 * | | | | 396 * | v | | 397 * | UPDATING | | 398 * | | | | 399 * | | | | 400 * | v | | 401 * | COOLDOWN | | 402 * | | | | 403 * | | | | 404 * | \---------------| | 405 * |_______________________________| 406 * 407 * 408 * The RX starts (once a secret has been provisioned) in the NORMAL state. In 409 * the NORMAL state, the current expected value of the Key Phase bit is 410 * recorded. When a flipped Key Phase bit is detected, the RX attempts to 411 * decrypt and authenticate the received packet with the 'next' keys rather than 412 * the 'current' keys. If (and only if) this authentication is successful, we 413 * move to the UPDATING state. (An attacker in the network could flip 414 * the Key Phase bit randomly, so it is essential we do nothing until AEAD 415 * authentication is complete.) 416 * 417 * In the UPDATING state, we know a key update is occurring and record 418 * the new Key Phase bit value as the newly current value, but we still keep the 419 * old keys around so that we can still process any packets which were still in 420 * flight when the key update was initiated. In the UPDATING state, a 421 * Key Phase bit value different to the current expected value is treated not as 422 * the initiation of another key update, but a reference to our old keys. 423 * 424 * Eventually we will be reasonably sure we are not going to receive any more 425 * packets with the old keys. At this point, we can transition to the COOLDOWN 426 * state. This transition occurs automatically after a certain amount of time; 427 * RFC 9001 recommends it be the PTO interval, which relates to our RTT to the 428 * peer. The duration also SHOULD NOT exceed three times the PTO to assist with 429 * maintaining PFS. 430 * 431 * In the COOLDOWN phase, the old keys have been securely erased and only one 432 * set of keys can be used: the current keys. If a packet is received with a Key 433 * Phase bit value different to the current Key Phase Bit value, this is treated 434 * as a request for a Key Update, but this request is ignored and the packet is 435 * treated as malformed. We do this to allow mitigation against malicious peers 436 * trying to initiate an excessive number of Key Updates. The timeout for the 437 * transition from UPDATING to COOLDOWN is recommended as adequate for 438 * this purpose in itself by the RFC, so the normal additional timeout value for 439 * the transition from COOLDOWN to normal is zero (immediate transition). 440 * 441 * A summary of each state: 442 * 443 * Epoch Exp KP Uses Keys KS0 KS1 If Non-Expected KP Bit 444 * ----- ------ --------- ------ ----- ---------------------- 445 * NORMAL 0 0 Keyset 0 Gen 0 Gen 1 → UPDATING 446 * UPDATING 1 1 Keyset 1 Gen 0 Gen 1 Use Keyset 0 447 * COOLDOWN 1 1 Keyset 1 Erased Gen 1 Ignore Packet (*) 448 * 449 * NORMAL 1 1 Keyset 1 Gen 2 Gen 1 → UPDATING 450 * UPDATING 2 0 Keyset 0 Gen 2 Gen 1 Use Keyset 1 451 * COOLDOWN 2 0 Keyset 0 Gen 2 Erased Ignore Packet (*) 452 * 453 * (*) Actually implemented by attempting to decrypt the packet with the 454 * wrong keys (which ultimately has the same outcome), as recommended 455 * by RFC 9001 to avoid creating timing channels. 456 * 457 * Note that the key material for the next key generation ("key epoch") is 458 * always kept in the NORMAL state (necessary to avoid side-channel attacks). 459 * This material is derived during the transition from COOLDOWN to NORMAL. 460 * 461 * Note that when a peer initiates a Key Update, we MUST also initiate a Key 462 * Update as per the RFC. The caller is responsible for detecting this condition 463 * and making the necessary calls to the TX side by detecting changes to the 464 * return value of ossl_qrx_get_key_epoch(). 465 * 466 * The above states (NORMAL, UPDATING, COOLDOWN) can themselves be 467 * considered substates of the PROVISIONED state. Providing a secret to the QRX 468 * for an EL transitions from UNPROVISIONED, the initial state, to PROVISIONED 469 * (NORMAL). Dropping key material for an EL transitions from whatever the 470 * current substate of the PROVISIONED state is to the DISCARDED state, which is 471 * the terminal state. 472 * 473 * Note that non-1RTT ELs cannot undergo key update, therefore a non-1RTT EL is 474 * always in the NORMAL substate if it is in the PROVISIONED state. 475 */ 476 477 /* 478 * Return the current RX key epoch for the 1-RTT encryption level. This is 479 * initially zero and is incremented by one for every Key Update successfully 480 * signalled by the peer. If the 1-RTT EL has not yet been provisioned or has 481 * been discarded, returns UINT64_MAX. 482 * 483 * A necessary implication of this API is that the least significant bit of the 484 * returned value corresponds to the currently expected Key Phase bit, though 485 * callers are not anticipated to have any need of this information. 486 * 487 * It is not possible for the returned value to overflow, as a QUIC connection 488 * cannot support more than 2**62 packet numbers, and a connection must be 489 * terminated if this limit is reached. 490 * 491 * The caller should use this function to detect when the key epoch has changed 492 * and use it to initiate a key update on the TX side. 493 * 494 * The value returned by this function increments specifically at the transition 495 * from the NORMAL to the UPDATING state discussed above. 496 */ 497 uint64_t ossl_qrx_get_key_epoch(OSSL_QRX *qrx); 498 499 /* 500 * Sets an optional callback which will be called when the key epoch changes. 501 * 502 * The callback is optional and can be unset by passing NULL for cb. 503 * cb_arg is an opaque value passed to cb. pn is the PN of the packet. 504 * Since key update is only supported for 1-RTT packets, the PN is always 505 * in the Application Data PN space. 506 */ 507 typedef void (ossl_qrx_key_update_cb)(QUIC_PN pn, void *arg); 508 509 int ossl_qrx_set_key_update_cb(OSSL_QRX *qrx, 510 ossl_qrx_key_update_cb *cb, void *cb_arg); 511 512 /* 513 * Relates to the 1-RTT encryption level. The caller should call this after the 514 * UPDATING state is reached, after a timeout to be determined by the caller. 515 * 516 * This transitions from the UPDATING state to the COOLDOWN state (if 517 * still in the UPDATING state). If normal is 1, then transitions from 518 * the COOLDOWN state to the NORMAL state. Both transitions can be performed at 519 * once if desired. 520 * 521 * If in the normal state, or if in the COOLDOWN state and normal is 0, this is 522 * a no-op and returns 1. Returns 0 if the 1-RTT EL has not been provisioned or 523 * has been dropped. 524 * 525 * It is essential that the caller call this within a few PTO intervals of a key 526 * update occurring (as detected by the caller in a call to 527 * ossl_qrx_key_get_key_epoch()), as otherwise the peer will not be able to 528 * perform a Key Update ever again. 529 */ 530 int ossl_qrx_key_update_timeout(OSSL_QRX *qrx, int normal); 531 532 533 /* 534 * Key Expiration 535 * ============== 536 */ 537 538 /* 539 * Returns the number of seemingly forged packets which have been received by 540 * the QRX. If this value reaches the value returned by 541 * ossl_qrx_get_max_epoch_forged_pkt_count() for a given EL, all further 542 * received encrypted packets for that EL will be discarded without processing. 543 * 544 * Note that the forged packet limit is for the connection lifetime, thus it is 545 * not reset by a key update. It is suggested that the caller terminate the 546 * connection a reasonable margin before the limit is reached. However, the 547 * exact limit imposed does vary by EL due to the possibility that different ELs 548 * use different AEADs. 549 */ 550 uint64_t ossl_qrx_get_cur_forged_pkt_count(OSSL_QRX *qrx); 551 552 /* 553 * Returns the maximum number of forged packets which the record layer will 554 * permit to be verified using this QRX instance. 555 */ 556 uint64_t ossl_qrx_get_max_forged_pkt_count(OSSL_QRX *qrx, 557 uint32_t enc_level); 558 559 # endif 560 561 #endif 562