1 /* $OpenBSD: tls13_lib.c,v 1.67 2022/07/20 06:32:24 jsing Exp $ */ 2 /* 3 * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org> 4 * Copyright (c) 2019 Bob Beck <beck@openbsd.org> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include <stddef.h> 20 21 #include <openssl/evp.h> 22 23 #include "ssl_locl.h" 24 #include "ssl_tlsext.h" 25 #include "tls13_internal.h" 26 27 /* 28 * Downgrade sentinels - RFC 8446 section 4.1.3, magic values which must be set 29 * by the server in server random if it is willing to downgrade but supports 30 * TLSv1.3 31 */ 32 const uint8_t tls13_downgrade_12[8] = { 33 0x44, 0x4f, 0x57, 0x4e, 0x47, 0x52, 0x44, 0x01, 34 }; 35 const uint8_t tls13_downgrade_11[8] = { 36 0x44, 0x4f, 0x57, 0x4e, 0x47, 0x52, 0x44, 0x00, 37 }; 38 39 /* 40 * HelloRetryRequest hash - RFC 8446 section 4.1.3. 41 */ 42 const uint8_t tls13_hello_retry_request_hash[32] = { 43 0xcf, 0x21, 0xad, 0x74, 0xe5, 0x9a, 0x61, 0x11, 44 0xbe, 0x1d, 0x8c, 0x02, 0x1e, 0x65, 0xb8, 0x91, 45 0xc2, 0xa2, 0x11, 0x16, 0x7a, 0xbb, 0x8c, 0x5e, 46 0x07, 0x9e, 0x09, 0xe2, 0xc8, 0xa8, 0x33, 0x9c, 47 }; 48 49 /* 50 * Certificate Verify padding - RFC 8446 section 4.4.3. 51 */ 52 const uint8_t tls13_cert_verify_pad[64] = { 53 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 54 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 55 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 56 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 57 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 58 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 59 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 60 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 61 }; 62 63 const uint8_t tls13_cert_client_verify_context[] = 64 "TLS 1.3, client CertificateVerify"; 65 const uint8_t tls13_cert_server_verify_context[] = 66 "TLS 1.3, server CertificateVerify"; 67 68 const EVP_AEAD * 69 tls13_cipher_aead(const SSL_CIPHER *cipher) 70 { 71 if (cipher == NULL) 72 return NULL; 73 if (cipher->algorithm_ssl != SSL_TLSV1_3) 74 return NULL; 75 76 switch (cipher->algorithm_enc) { 77 case SSL_AES128GCM: 78 return EVP_aead_aes_128_gcm(); 79 case SSL_AES256GCM: 80 return EVP_aead_aes_256_gcm(); 81 case SSL_CHACHA20POLY1305: 82 return EVP_aead_chacha20_poly1305(); 83 } 84 85 return NULL; 86 } 87 88 const EVP_MD * 89 tls13_cipher_hash(const SSL_CIPHER *cipher) 90 { 91 if (cipher == NULL) 92 return NULL; 93 if (cipher->algorithm_ssl != SSL_TLSV1_3) 94 return NULL; 95 96 switch (cipher->algorithm2) { 97 case SSL_HANDSHAKE_MAC_SHA256: 98 return EVP_sha256(); 99 case SSL_HANDSHAKE_MAC_SHA384: 100 return EVP_sha384(); 101 } 102 103 return NULL; 104 } 105 106 static void 107 tls13_alert_received_cb(uint8_t alert_desc, void *arg) 108 { 109 struct tls13_ctx *ctx = arg; 110 111 if (alert_desc == TLS13_ALERT_CLOSE_NOTIFY) { 112 ctx->close_notify_recv = 1; 113 ctx->ssl->internal->shutdown |= SSL_RECEIVED_SHUTDOWN; 114 ctx->ssl->s3->warn_alert = alert_desc; 115 return; 116 } 117 118 if (alert_desc == TLS13_ALERT_USER_CANCELED) { 119 /* 120 * We treat this as advisory, since a close_notify alert 121 * SHOULD follow this alert (RFC 8446 section 6.1). 122 */ 123 return; 124 } 125 126 /* All other alerts are treated as fatal in TLSv1.3. */ 127 ctx->ssl->s3->fatal_alert = alert_desc; 128 129 SSLerror(ctx->ssl, SSL_AD_REASON_OFFSET + alert_desc); 130 ERR_asprintf_error_data("SSL alert number %d", alert_desc); 131 132 SSL_CTX_remove_session(ctx->ssl->ctx, ctx->ssl->session); 133 } 134 135 static void 136 tls13_alert_sent_cb(uint8_t alert_desc, void *arg) 137 { 138 struct tls13_ctx *ctx = arg; 139 140 if (alert_desc == TLS13_ALERT_CLOSE_NOTIFY) { 141 ctx->close_notify_sent = 1; 142 return; 143 } 144 145 if (alert_desc == TLS13_ALERT_USER_CANCELED) { 146 return; 147 } 148 149 /* All other alerts are treated as fatal in TLSv1.3. */ 150 if (ctx->error.code == 0) 151 SSLerror(ctx->ssl, SSL_AD_REASON_OFFSET + alert_desc); 152 } 153 154 static void 155 tls13_legacy_handshake_message_recv_cb(void *arg) 156 { 157 struct tls13_ctx *ctx = arg; 158 SSL *s = ctx->ssl; 159 CBS cbs; 160 161 if (s->internal->msg_callback == NULL) 162 return; 163 164 tls13_handshake_msg_data(ctx->hs_msg, &cbs); 165 ssl_msg_callback(s, 0, SSL3_RT_HANDSHAKE, CBS_data(&cbs), CBS_len(&cbs)); 166 } 167 168 static void 169 tls13_legacy_handshake_message_sent_cb(void *arg) 170 { 171 struct tls13_ctx *ctx = arg; 172 SSL *s = ctx->ssl; 173 CBS cbs; 174 175 if (s->internal->msg_callback == NULL) 176 return; 177 178 tls13_handshake_msg_data(ctx->hs_msg, &cbs); 179 ssl_msg_callback(s, 1, SSL3_RT_HANDSHAKE, CBS_data(&cbs), CBS_len(&cbs)); 180 } 181 182 static void 183 tls13_legacy_info_cb(void *arg, int state, int ret) 184 { 185 struct tls13_ctx *ctx = arg; 186 SSL *s = ctx->ssl; 187 188 ssl_info_callback(s, state, ret); 189 } 190 191 static int 192 tls13_legacy_ocsp_status_recv_cb(void *arg) 193 { 194 struct tls13_ctx *ctx = arg; 195 SSL *s = ctx->ssl; 196 int ret; 197 198 if (s->ctx->internal->tlsext_status_cb == NULL) 199 return 1; 200 201 ret = s->ctx->internal->tlsext_status_cb(s, 202 s->ctx->internal->tlsext_status_arg); 203 if (ret < 0) { 204 ctx->alert = TLS13_ALERT_INTERNAL_ERROR; 205 SSLerror(s, ERR_R_MALLOC_FAILURE); 206 return 0; 207 } 208 if (ret == 0) { 209 ctx->alert = TLS13_ALERT_BAD_CERTIFICATE_STATUS_RESPONSE; 210 SSLerror(s, SSL_R_INVALID_STATUS_RESPONSE); 211 return 0; 212 } 213 214 return 1; 215 } 216 217 static int 218 tls13_phh_update_read_traffic_secret(struct tls13_ctx *ctx) 219 { 220 struct tls13_secrets *secrets = ctx->hs->tls13.secrets; 221 struct tls13_secret *secret; 222 223 if (ctx->mode == TLS13_HS_CLIENT) { 224 secret = &secrets->server_application_traffic; 225 if (!tls13_update_server_traffic_secret(secrets)) 226 return 0; 227 } else { 228 secret = &secrets->client_application_traffic; 229 if (!tls13_update_client_traffic_secret(secrets)) 230 return 0; 231 } 232 233 return tls13_record_layer_set_read_traffic_key(ctx->rl, secret); 234 } 235 236 static int 237 tls13_phh_update_write_traffic_secret(struct tls13_ctx *ctx) 238 { 239 struct tls13_secrets *secrets = ctx->hs->tls13.secrets; 240 struct tls13_secret *secret; 241 242 if (ctx->mode == TLS13_HS_CLIENT) { 243 secret = &secrets->client_application_traffic; 244 if (!tls13_update_client_traffic_secret(secrets)) 245 return 0; 246 } else { 247 secret = &secrets->server_application_traffic; 248 if (!tls13_update_server_traffic_secret(secrets)) 249 return 0; 250 } 251 252 return tls13_record_layer_set_write_traffic_key(ctx->rl, secret); 253 } 254 255 /* 256 * XXX arbitrarily chosen limit of 100 post handshake handshake 257 * messages in an hour - to avoid a hostile peer from constantly 258 * requesting certificates or key renegotiaitons, etc. 259 */ 260 static int 261 tls13_phh_limit_check(struct tls13_ctx *ctx) 262 { 263 time_t now = time(NULL); 264 265 if (ctx->phh_last_seen > now - TLS13_PHH_LIMIT_TIME) { 266 if (ctx->phh_count > TLS13_PHH_LIMIT) 267 return 0; 268 } else 269 ctx->phh_count = 0; 270 ctx->phh_count++; 271 ctx->phh_last_seen = now; 272 return 1; 273 } 274 275 static ssize_t 276 tls13_key_update_recv(struct tls13_ctx *ctx, CBS *cbs) 277 { 278 struct tls13_handshake_msg *hs_msg = NULL; 279 CBB cbb_hs; 280 CBS cbs_hs; 281 uint8_t alert = TLS13_ALERT_INTERNAL_ERROR; 282 uint8_t key_update_request; 283 ssize_t ret; 284 285 if (!CBS_get_u8(cbs, &key_update_request)) { 286 alert = TLS13_ALERT_DECODE_ERROR; 287 goto err; 288 } 289 if (CBS_len(cbs) != 0) { 290 alert = TLS13_ALERT_DECODE_ERROR; 291 goto err; 292 } 293 if (key_update_request > 1) { 294 alert = TLS13_ALERT_ILLEGAL_PARAMETER; 295 goto err; 296 } 297 298 if (!tls13_phh_update_read_traffic_secret(ctx)) 299 goto err; 300 301 if (key_update_request == 0) 302 return TLS13_IO_SUCCESS; 303 304 /* Our peer requested that we update our write traffic keys. */ 305 if ((hs_msg = tls13_handshake_msg_new()) == NULL) 306 goto err; 307 if (!tls13_handshake_msg_start(hs_msg, &cbb_hs, TLS13_MT_KEY_UPDATE)) 308 goto err; 309 if (!CBB_add_u8(&cbb_hs, 0)) 310 goto err; 311 if (!tls13_handshake_msg_finish(hs_msg)) 312 goto err; 313 314 ctx->key_update_request = 1; 315 tls13_handshake_msg_data(hs_msg, &cbs_hs); 316 ret = tls13_record_layer_phh(ctx->rl, &cbs_hs); 317 318 tls13_handshake_msg_free(hs_msg); 319 hs_msg = NULL; 320 321 return ret; 322 323 err: 324 tls13_handshake_msg_free(hs_msg); 325 326 return tls13_send_alert(ctx->rl, alert); 327 } 328 329 static void 330 tls13_phh_done_cb(void *cb_arg) 331 { 332 struct tls13_ctx *ctx = cb_arg; 333 334 if (ctx->key_update_request) { 335 tls13_phh_update_write_traffic_secret(ctx); 336 ctx->key_update_request = 0; 337 } 338 } 339 340 static ssize_t 341 tls13_phh_received_cb(void *cb_arg) 342 { 343 ssize_t ret = TLS13_IO_FAILURE; 344 struct tls13_ctx *ctx = cb_arg; 345 CBS cbs; 346 347 if (!tls13_phh_limit_check(ctx)) 348 return tls13_send_alert(ctx->rl, TLS13_ALERT_UNEXPECTED_MESSAGE); 349 350 if ((ctx->hs_msg == NULL) && 351 ((ctx->hs_msg = tls13_handshake_msg_new()) == NULL)) 352 return TLS13_IO_FAILURE; 353 354 if ((ret = tls13_handshake_msg_recv(ctx->hs_msg, ctx->rl)) != 355 TLS13_IO_SUCCESS) 356 return ret; 357 358 if (!tls13_handshake_msg_content(ctx->hs_msg, &cbs)) 359 return TLS13_IO_FAILURE; 360 361 switch(tls13_handshake_msg_type(ctx->hs_msg)) { 362 case TLS13_MT_KEY_UPDATE: 363 ret = tls13_key_update_recv(ctx, &cbs); 364 break; 365 case TLS13_MT_NEW_SESSION_TICKET: 366 /* XXX do nothing for now and ignore this */ 367 break; 368 case TLS13_MT_CERTIFICATE_REQUEST: 369 /* XXX add support if we choose to advertise this */ 370 /* FALLTHROUGH */ 371 default: 372 ret = TLS13_IO_FAILURE; /* XXX send alert */ 373 break; 374 } 375 376 tls13_handshake_msg_free(ctx->hs_msg); 377 ctx->hs_msg = NULL; 378 return ret; 379 } 380 381 static const struct tls13_record_layer_callbacks rl_callbacks = { 382 .wire_read = tls13_legacy_wire_read_cb, 383 .wire_write = tls13_legacy_wire_write_cb, 384 .wire_flush = tls13_legacy_wire_flush_cb, 385 .alert_recv = tls13_alert_received_cb, 386 .alert_sent = tls13_alert_sent_cb, 387 .phh_recv = tls13_phh_received_cb, 388 .phh_sent = tls13_phh_done_cb, 389 }; 390 391 struct tls13_ctx * 392 tls13_ctx_new(int mode, SSL *ssl) 393 { 394 struct tls13_ctx *ctx = NULL; 395 396 if ((ctx = calloc(sizeof(struct tls13_ctx), 1)) == NULL) 397 goto err; 398 399 ctx->hs = &ssl->s3->hs; 400 ctx->mode = mode; 401 ctx->ssl = ssl; 402 403 if ((ctx->rl = tls13_record_layer_new(&rl_callbacks, ctx)) == NULL) 404 goto err; 405 406 ctx->handshake_message_sent_cb = tls13_legacy_handshake_message_sent_cb; 407 ctx->handshake_message_recv_cb = tls13_legacy_handshake_message_recv_cb; 408 ctx->info_cb = tls13_legacy_info_cb; 409 ctx->ocsp_status_recv_cb = tls13_legacy_ocsp_status_recv_cb; 410 411 if (!SSL_is_quic(ssl)) 412 ctx->middlebox_compat = 1; 413 414 ssl->internal->tls13 = ctx; 415 416 return ctx; 417 418 err: 419 tls13_ctx_free(ctx); 420 421 return NULL; 422 } 423 424 void 425 tls13_ctx_free(struct tls13_ctx *ctx) 426 { 427 if (ctx == NULL) 428 return; 429 430 tls13_error_clear(&ctx->error); 431 tls13_record_layer_free(ctx->rl); 432 tls13_handshake_msg_free(ctx->hs_msg); 433 434 freezero(ctx, sizeof(struct tls13_ctx)); 435 } 436 437 int 438 tls13_cert_add(struct tls13_ctx *ctx, CBB *cbb, X509 *cert, 439 int (*build_extensions)(SSL *s, uint16_t msg_type, CBB *cbb)) 440 { 441 CBB cert_data, cert_exts; 442 uint8_t *data; 443 int cert_len; 444 445 if ((cert_len = i2d_X509(cert, NULL)) < 0) 446 return 0; 447 448 if (!CBB_add_u24_length_prefixed(cbb, &cert_data)) 449 return 0; 450 if (!CBB_add_space(&cert_data, &data, cert_len)) 451 return 0; 452 if (i2d_X509(cert, &data) != cert_len) 453 return 0; 454 if (build_extensions != NULL) { 455 if (!build_extensions(ctx->ssl, SSL_TLSEXT_MSG_CT, cbb)) 456 return 0; 457 } else { 458 if (!CBB_add_u16_length_prefixed(cbb, &cert_exts)) 459 return 0; 460 } 461 if (!CBB_flush(cbb)) 462 return 0; 463 464 return 1; 465 } 466 467 int 468 tls13_synthetic_handshake_message(struct tls13_ctx *ctx) 469 { 470 struct tls13_handshake_msg *hm = NULL; 471 unsigned char buf[EVP_MAX_MD_SIZE]; 472 size_t hash_len; 473 CBB cbb; 474 CBS cbs; 475 SSL *s = ctx->ssl; 476 int ret = 0; 477 478 /* 479 * Replace ClientHello with synthetic handshake message - see 480 * RFC 8446 section 4.4.1. 481 */ 482 if (!tls1_transcript_hash_init(s)) 483 goto err; 484 if (!tls1_transcript_hash_value(s, buf, sizeof(buf), &hash_len)) 485 goto err; 486 487 if ((hm = tls13_handshake_msg_new()) == NULL) 488 goto err; 489 if (!tls13_handshake_msg_start(hm, &cbb, TLS13_MT_MESSAGE_HASH)) 490 goto err; 491 if (!CBB_add_bytes(&cbb, buf, hash_len)) 492 goto err; 493 if (!tls13_handshake_msg_finish(hm)) 494 goto err; 495 496 tls13_handshake_msg_data(hm, &cbs); 497 498 tls1_transcript_reset(ctx->ssl); 499 if (!tls1_transcript_record(ctx->ssl, CBS_data(&cbs), CBS_len(&cbs))) 500 goto err; 501 502 ret = 1; 503 504 err: 505 tls13_handshake_msg_free(hm); 506 507 return ret; 508 } 509 510 int 511 tls13_clienthello_hash_init(struct tls13_ctx *ctx) 512 { 513 if (ctx->hs->tls13.clienthello_md_ctx != NULL) 514 return 0; 515 if ((ctx->hs->tls13.clienthello_md_ctx = EVP_MD_CTX_new()) == NULL) 516 return 0; 517 if (!EVP_DigestInit_ex(ctx->hs->tls13.clienthello_md_ctx, 518 EVP_sha256(), NULL)) 519 return 0; 520 521 if ((ctx->hs->tls13.clienthello_hash == NULL) && 522 (ctx->hs->tls13.clienthello_hash = calloc(1, EVP_MAX_MD_SIZE)) == 523 NULL) 524 return 0; 525 526 return 1; 527 } 528 529 void 530 tls13_clienthello_hash_clear(struct ssl_handshake_tls13_st *hs) /* XXX */ 531 { 532 EVP_MD_CTX_free(hs->clienthello_md_ctx); 533 hs->clienthello_md_ctx = NULL; 534 freezero(hs->clienthello_hash, EVP_MAX_MD_SIZE); 535 hs->clienthello_hash = NULL; 536 } 537 538 int 539 tls13_clienthello_hash_update_bytes(struct tls13_ctx *ctx, void *data, 540 size_t len) 541 { 542 return EVP_DigestUpdate(ctx->hs->tls13.clienthello_md_ctx, data, len); 543 } 544 545 int 546 tls13_clienthello_hash_update(struct tls13_ctx *ctx, CBS *cbs) 547 { 548 return tls13_clienthello_hash_update_bytes(ctx, (void *)CBS_data(cbs), 549 CBS_len(cbs)); 550 } 551 552 int 553 tls13_clienthello_hash_finalize(struct tls13_ctx *ctx) 554 { 555 if (!EVP_DigestFinal_ex(ctx->hs->tls13.clienthello_md_ctx, 556 ctx->hs->tls13.clienthello_hash, 557 &ctx->hs->tls13.clienthello_hash_len)) 558 return 0; 559 EVP_MD_CTX_free(ctx->hs->tls13.clienthello_md_ctx); 560 ctx->hs->tls13.clienthello_md_ctx = NULL; 561 return 1; 562 } 563 564 int 565 tls13_clienthello_hash_validate(struct tls13_ctx *ctx) 566 { 567 unsigned char new_ch_hash[EVP_MAX_MD_SIZE]; 568 unsigned int new_ch_hash_len; 569 570 if (ctx->hs->tls13.clienthello_hash == NULL) 571 return 0; 572 573 if (!EVP_DigestFinal_ex(ctx->hs->tls13.clienthello_md_ctx, 574 new_ch_hash, &new_ch_hash_len)) 575 return 0; 576 EVP_MD_CTX_free(ctx->hs->tls13.clienthello_md_ctx); 577 ctx->hs->tls13.clienthello_md_ctx = NULL; 578 579 if (ctx->hs->tls13.clienthello_hash_len != new_ch_hash_len) 580 return 0; 581 if (memcmp(ctx->hs->tls13.clienthello_hash, new_ch_hash, 582 new_ch_hash_len) != 0) 583 return 0; 584 585 return 1; 586 } 587 588 int 589 tls13_exporter(struct tls13_ctx *ctx, const uint8_t *label, size_t label_len, 590 const uint8_t *context_value, size_t context_value_len, uint8_t *out, 591 size_t out_len) 592 { 593 struct tls13_secret context, export_out, export_secret; 594 struct tls13_secrets *secrets = ctx->hs->tls13.secrets; 595 EVP_MD_CTX *md_ctx = NULL; 596 unsigned int md_out_len; 597 int md_len; 598 int ret = 0; 599 600 /* 601 * RFC 8446 Section 7.5. 602 */ 603 604 memset(&context, 0, sizeof(context)); 605 memset(&export_secret, 0, sizeof(export_secret)); 606 607 export_out.data = out; 608 export_out.len = out_len; 609 610 if (!ctx->handshake_completed) 611 return 0; 612 613 md_len = EVP_MD_size(secrets->digest); 614 if (md_len <= 0 || md_len > EVP_MAX_MD_SIZE) 615 goto err; 616 617 if (!tls13_secret_init(&export_secret, md_len)) 618 goto err; 619 if (!tls13_secret_init(&context, md_len)) 620 goto err; 621 622 /* In TLSv1.3 no context is equivalent to an empty context. */ 623 if (context_value == NULL) { 624 context_value = ""; 625 context_value_len = 0; 626 } 627 628 if ((md_ctx = EVP_MD_CTX_new()) == NULL) 629 goto err; 630 if (!EVP_DigestInit_ex(md_ctx, secrets->digest, NULL)) 631 goto err; 632 if (!EVP_DigestUpdate(md_ctx, context_value, context_value_len)) 633 goto err; 634 if (!EVP_DigestFinal_ex(md_ctx, context.data, &md_out_len)) 635 goto err; 636 if (md_len != md_out_len) 637 goto err; 638 639 if (!tls13_derive_secret_with_label_length(&export_secret, 640 secrets->digest, &secrets->exporter_master, label, label_len, 641 &secrets->empty_hash)) 642 goto err; 643 644 if (!tls13_hkdf_expand_label(&export_out, secrets->digest, 645 &export_secret, "exporter", &context)) 646 goto err; 647 648 ret = 1; 649 650 err: 651 EVP_MD_CTX_free(md_ctx); 652 tls13_secret_cleanup(&context); 653 tls13_secret_cleanup(&export_secret); 654 655 return ret; 656 } 657