1 /* 2 * Copyright 2014-2025 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 /* Custom extension utility functions */ 11 12 #include <openssl/ct.h> 13 #include "../ssl_local.h" 14 #include "internal/cryptlib.h" 15 #include "internal/ssl_unwrap.h" 16 #include "statem_local.h" 17 18 typedef struct { 19 void *add_arg; 20 custom_ext_add_cb add_cb; 21 custom_ext_free_cb free_cb; 22 } custom_ext_add_cb_wrap; 23 24 typedef struct { 25 void *parse_arg; 26 custom_ext_parse_cb parse_cb; 27 } custom_ext_parse_cb_wrap; 28 29 /* 30 * Provide thin wrapper callbacks which convert new style arguments to old style 31 */ 32 static int custom_ext_add_old_cb_wrap(SSL *s, unsigned int ext_type, 33 unsigned int context, 34 const unsigned char **out, 35 size_t *outlen, X509 *x, size_t chainidx, 36 int *al, void *add_arg) 37 { 38 custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg; 39 40 if (add_cb_wrap->add_cb == NULL) 41 return 1; 42 43 return add_cb_wrap->add_cb(s, ext_type, out, outlen, al, 44 add_cb_wrap->add_arg); 45 } 46 47 static void custom_ext_free_old_cb_wrap(SSL *s, unsigned int ext_type, 48 unsigned int context, 49 const unsigned char *out, void *add_arg) 50 { 51 custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg; 52 53 if (add_cb_wrap->free_cb == NULL) 54 return; 55 56 add_cb_wrap->free_cb(s, ext_type, out, add_cb_wrap->add_arg); 57 } 58 59 static int custom_ext_parse_old_cb_wrap(SSL *s, unsigned int ext_type, 60 unsigned int context, 61 const unsigned char *in, 62 size_t inlen, X509 *x, size_t chainidx, 63 int *al, void *parse_arg) 64 { 65 custom_ext_parse_cb_wrap *parse_cb_wrap = 66 (custom_ext_parse_cb_wrap *)parse_arg; 67 68 if (parse_cb_wrap->parse_cb == NULL) 69 return 1; 70 71 return parse_cb_wrap->parse_cb(s, ext_type, in, inlen, al, 72 parse_cb_wrap->parse_arg); 73 } 74 75 /* 76 * Find a custom extension from the list. The |role| param is there to 77 * support the legacy API where custom extensions for client and server could 78 * be set independently on the same SSL_CTX. It is set to ENDPOINT_SERVER if we 79 * are trying to find a method relevant to the server, ENDPOINT_CLIENT for the 80 * client, or ENDPOINT_BOTH for either 81 */ 82 custom_ext_method *custom_ext_find(const custom_ext_methods *exts, 83 ENDPOINT role, unsigned int ext_type, 84 size_t *idx) 85 { 86 size_t i; 87 custom_ext_method *meth = exts->meths; 88 89 for (i = 0; i < exts->meths_count; i++, meth++) { 90 if (ext_type == meth->ext_type 91 && (role == ENDPOINT_BOTH || role == meth->role 92 || meth->role == ENDPOINT_BOTH)) { 93 if (idx != NULL) 94 *idx = i; 95 return meth; 96 } 97 } 98 return NULL; 99 } 100 101 /* 102 * Initialise custom extensions flags to indicate neither sent nor received. 103 */ 104 void custom_ext_init(custom_ext_methods *exts) 105 { 106 size_t i; 107 custom_ext_method *meth = exts->meths; 108 109 for (i = 0; i < exts->meths_count; i++, meth++) 110 meth->ext_flags &= ~(SSL_EXT_FLAG_SENT | SSL_EXT_FLAG_RECEIVED); 111 } 112 113 /* Pass received custom extension data to the application for parsing. */ 114 int custom_ext_parse(SSL_CONNECTION *s, unsigned int context, 115 unsigned int ext_type, 116 const unsigned char *ext_data, size_t ext_size, X509 *x, 117 size_t chainidx) 118 { 119 int al = 0; 120 custom_ext_methods *exts = &s->cert->custext; 121 custom_ext_method *meth; 122 ENDPOINT role = ENDPOINT_BOTH; 123 124 if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO)) != 0) 125 role = s->server ? ENDPOINT_SERVER : ENDPOINT_CLIENT; 126 127 meth = custom_ext_find(exts, role, ext_type, NULL); 128 /* If not found return success */ 129 if (!meth) 130 return 1; 131 132 /* Check if extension is defined for our protocol. If not, skip */ 133 if (!extension_is_relevant(s, meth->context, context)) 134 return 1; 135 136 if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO 137 | SSL_EXT_TLS1_3_SERVER_HELLO 138 | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS)) != 0) { 139 /* 140 * If it's ServerHello or EncryptedExtensions we can't have any 141 * extensions not sent in ClientHello. 142 */ 143 if ((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0) { 144 SSLfatal(s, TLS1_AD_UNSUPPORTED_EXTENSION, SSL_R_BAD_EXTENSION); 145 return 0; 146 } 147 } 148 149 /* 150 * Extensions received in the ClientHello or CertificateRequest are marked 151 * with the SSL_EXT_FLAG_RECEIVED. This is so we know to add the equivalent 152 * extensions in the response messages 153 */ 154 if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST)) 155 != 0) 156 meth->ext_flags |= SSL_EXT_FLAG_RECEIVED; 157 158 /* If no parse function set return success */ 159 if (meth->parse_cb == NULL) 160 return 1; 161 162 if (meth->parse_cb(SSL_CONNECTION_GET_USER_SSL(s), ext_type, context, ext_data, 163 ext_size, x, chainidx, &al, meth->parse_arg) <= 0) { 164 SSLfatal(s, al, SSL_R_BAD_EXTENSION); 165 return 0; 166 } 167 168 return 1; 169 } 170 171 /* 172 * Request custom extension data from the application and add to the return 173 * buffer. 174 */ 175 int custom_ext_add(SSL_CONNECTION *s, int context, WPACKET *pkt, X509 *x, 176 size_t chainidx, int maxversion) 177 { 178 custom_ext_methods *exts = &s->cert->custext; 179 custom_ext_method *meth; 180 size_t i; 181 int al; 182 int for_comp = (context & SSL_EXT_TLS1_3_CERTIFICATE_COMPRESSION) != 0; 183 184 for (i = 0; i < exts->meths_count; i++) { 185 const unsigned char *out = NULL; 186 size_t outlen = 0; 187 188 meth = exts->meths + i; 189 190 if (!should_add_extension(s, meth->context, context, maxversion)) 191 continue; 192 193 if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO 194 | SSL_EXT_TLS1_3_SERVER_HELLO 195 | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS 196 | SSL_EXT_TLS1_3_CERTIFICATE 197 | SSL_EXT_TLS1_3_RAW_PUBLIC_KEY 198 | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST)) != 0) { 199 /* Only send extensions present in ClientHello/CertificateRequest */ 200 if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED)) 201 continue; 202 } 203 /* 204 * We skip it if the callback is absent - except for a ClientHello where 205 * we add an empty extension. 206 */ 207 if ((context & SSL_EXT_CLIENT_HELLO) == 0 && meth->add_cb == NULL) 208 continue; 209 210 if (meth->add_cb != NULL) { 211 int cb_retval = meth->add_cb(SSL_CONNECTION_GET_USER_SSL(s), 212 meth->ext_type, context, &out, 213 &outlen, x, chainidx, &al, 214 meth->add_arg); 215 216 if (cb_retval < 0) { 217 if (!for_comp) 218 SSLfatal(s, al, SSL_R_CALLBACK_FAILED); 219 return 0; /* error */ 220 } 221 if (cb_retval == 0) 222 continue; /* skip this extension */ 223 } 224 225 if (!WPACKET_put_bytes_u16(pkt, meth->ext_type) 226 || !WPACKET_start_sub_packet_u16(pkt) 227 || (outlen > 0 && !WPACKET_memcpy(pkt, out, outlen)) 228 || !WPACKET_close(pkt)) { 229 if (meth->free_cb != NULL) 230 meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type, 231 context, out, meth->add_arg); 232 if (!for_comp) 233 SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR); 234 return 0; 235 } 236 if ((context & SSL_EXT_CLIENT_HELLO) != 0) { 237 /* 238 * We can't send duplicates: code logic should prevent this. 239 */ 240 if (!ossl_assert((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0)) { 241 if (meth->free_cb != NULL) 242 meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type, 243 context, out, meth->add_arg); 244 if (!for_comp) 245 SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR); 246 return 0; 247 } 248 /* 249 * Indicate extension has been sent: this is both a sanity check to 250 * ensure we don't send duplicate extensions and indicates that it 251 * is not an error if the extension is present in ServerHello. 252 */ 253 meth->ext_flags |= SSL_EXT_FLAG_SENT; 254 } 255 if (meth->free_cb != NULL) 256 meth->free_cb(SSL_CONNECTION_GET_USER_SSL(s), meth->ext_type, 257 context, out, meth->add_arg); 258 } 259 return 1; 260 } 261 262 /* Copy the flags from src to dst for any extensions that exist in both */ 263 int custom_exts_copy_flags(custom_ext_methods *dst, 264 const custom_ext_methods *src) 265 { 266 size_t i; 267 custom_ext_method *methsrc = src->meths; 268 269 for (i = 0; i < src->meths_count; i++, methsrc++) { 270 custom_ext_method *methdst = custom_ext_find(dst, methsrc->role, 271 methsrc->ext_type, NULL); 272 273 if (methdst == NULL) 274 continue; 275 276 methdst->ext_flags = methsrc->ext_flags; 277 } 278 279 return 1; 280 } 281 282 /* Copy old style API wrapper arguments */ 283 static void custom_ext_copy_old_cb(custom_ext_method *methdst, 284 const custom_ext_method *methsrc, 285 int *err) 286 { 287 if (methsrc->add_cb != custom_ext_add_old_cb_wrap) 288 return; 289 290 if (*err) { 291 methdst->add_arg = NULL; 292 methdst->parse_arg = NULL; 293 return; 294 } 295 296 methdst->add_arg = OPENSSL_memdup(methsrc->add_arg, 297 sizeof(custom_ext_add_cb_wrap)); 298 methdst->parse_arg = OPENSSL_memdup(methsrc->parse_arg, 299 sizeof(custom_ext_parse_cb_wrap)); 300 301 if (methdst->add_arg == NULL || methdst->parse_arg == NULL) 302 *err = 1; 303 304 return; 305 } 306 307 /* Copy table of custom extensions */ 308 int custom_exts_copy(custom_ext_methods *dst, const custom_ext_methods *src) 309 { 310 size_t i; 311 int err = 0; 312 313 if (src->meths_count > 0) { 314 dst->meths = 315 OPENSSL_memdup(src->meths, 316 sizeof(*src->meths) * src->meths_count); 317 if (dst->meths == NULL) 318 return 0; 319 dst->meths_count = src->meths_count; 320 321 for (i = 0; i < src->meths_count; i++) 322 custom_ext_copy_old_cb(&dst->meths[i], &src->meths[i], &err); 323 } 324 325 if (err) { 326 custom_exts_free(dst); 327 return 0; 328 } 329 330 return 1; 331 } 332 333 /* Copy custom extensions that were set on connection */ 334 int custom_exts_copy_conn(custom_ext_methods *dst, 335 const custom_ext_methods *src) 336 { 337 size_t i; 338 int err = 0; 339 340 if (src->meths_count > 0) { 341 size_t meths_count = 0; 342 343 for (i = 0; i < src->meths_count; i++) 344 if ((src->meths[i].ext_flags & SSL_EXT_FLAG_CONN) != 0) 345 meths_count++; 346 347 if (meths_count > 0) { 348 custom_ext_method *methdst = 349 OPENSSL_realloc(dst->meths, 350 (dst->meths_count + meths_count) * 351 sizeof(custom_ext_method)); 352 353 if (methdst == NULL) 354 return 0; 355 356 for (i = 0; i < dst->meths_count; i++) 357 custom_ext_copy_old_cb(&methdst[i], &dst->meths[i], &err); 358 359 dst->meths = methdst; 360 methdst += dst->meths_count; 361 362 for (i = 0; i < src->meths_count; i++) { 363 custom_ext_method *methsrc = &src->meths[i]; 364 365 if ((methsrc->ext_flags & SSL_EXT_FLAG_CONN) == 0) 366 continue; 367 368 memcpy(methdst, methsrc, sizeof(custom_ext_method)); 369 custom_ext_copy_old_cb(methdst, methsrc, &err); 370 methdst++; 371 } 372 373 dst->meths_count += meths_count; 374 } 375 } 376 377 if (err) { 378 custom_exts_free(dst); 379 return 0; 380 } 381 382 return 1; 383 } 384 385 void custom_exts_free(custom_ext_methods *exts) 386 { 387 size_t i; 388 custom_ext_method *meth; 389 390 for (i = 0, meth = exts->meths; i < exts->meths_count; i++, meth++) { 391 if (meth->add_cb != custom_ext_add_old_cb_wrap) 392 continue; 393 394 /* Old style API wrapper. Need to free the arguments too */ 395 OPENSSL_free(meth->add_arg); 396 OPENSSL_free(meth->parse_arg); 397 } 398 OPENSSL_free(exts->meths); 399 exts->meths = NULL; 400 exts->meths_count = 0; 401 } 402 403 /* Return true if a client custom extension exists, false otherwise */ 404 int SSL_CTX_has_client_custom_ext(const SSL_CTX *ctx, unsigned int ext_type) 405 { 406 return custom_ext_find(&ctx->cert->custext, ENDPOINT_CLIENT, ext_type, 407 NULL) != NULL; 408 } 409 410 int ossl_tls_add_custom_ext_intern(SSL_CTX *ctx, custom_ext_methods *exts, 411 ENDPOINT role, unsigned int ext_type, 412 unsigned int context, 413 SSL_custom_ext_add_cb_ex add_cb, 414 SSL_custom_ext_free_cb_ex free_cb, 415 void *add_arg, 416 SSL_custom_ext_parse_cb_ex parse_cb, 417 void *parse_arg) 418 { 419 custom_ext_method *meth, *tmp; 420 421 /* 422 * Check application error: if add_cb is not set free_cb will never be 423 * called. 424 */ 425 if (add_cb == NULL && free_cb != NULL) 426 return 0; 427 428 if (exts == NULL) 429 exts = &ctx->cert->custext; 430 431 #ifndef OPENSSL_NO_CT 432 /* 433 * We don't want applications registering callbacks for SCT extensions 434 * whilst simultaneously using the built-in SCT validation features, as 435 * these two things may not play well together. 436 */ 437 if (ext_type == TLSEXT_TYPE_signed_certificate_timestamp 438 && (context & SSL_EXT_CLIENT_HELLO) != 0 439 && ctx != NULL 440 && SSL_CTX_ct_is_enabled(ctx)) 441 return 0; 442 #endif 443 444 /* 445 * Don't add if extension supported internally, but make exception 446 * for extension types that previously were not supported, but now are. 447 */ 448 if (SSL_extension_supported(ext_type) 449 && ext_type != TLSEXT_TYPE_signed_certificate_timestamp) 450 return 0; 451 452 /* Extension type must fit in 16 bits */ 453 if (ext_type > 0xffff) 454 return 0; 455 /* Search for duplicate */ 456 if (custom_ext_find(exts, role, ext_type, NULL)) 457 return 0; 458 tmp = OPENSSL_realloc(exts->meths, 459 (exts->meths_count + 1) * sizeof(custom_ext_method)); 460 if (tmp == NULL) 461 return 0; 462 463 exts->meths = tmp; 464 meth = exts->meths + exts->meths_count; 465 memset(meth, 0, sizeof(*meth)); 466 meth->role = role; 467 meth->context = context; 468 meth->parse_cb = parse_cb; 469 meth->add_cb = add_cb; 470 meth->free_cb = free_cb; 471 meth->ext_type = ext_type; 472 meth->ext_flags = (ctx == NULL) ? SSL_EXT_FLAG_CONN : 0; 473 meth->add_arg = add_arg; 474 meth->parse_arg = parse_arg; 475 exts->meths_count++; 476 return 1; 477 } 478 479 static int add_old_custom_ext(SSL_CTX *ctx, ENDPOINT role, 480 unsigned int ext_type, 481 unsigned int context, 482 custom_ext_add_cb add_cb, 483 custom_ext_free_cb free_cb, 484 void *add_arg, 485 custom_ext_parse_cb parse_cb, void *parse_arg) 486 { 487 custom_ext_add_cb_wrap *add_cb_wrap 488 = OPENSSL_malloc(sizeof(*add_cb_wrap)); 489 custom_ext_parse_cb_wrap *parse_cb_wrap 490 = OPENSSL_malloc(sizeof(*parse_cb_wrap)); 491 int ret; 492 493 if (add_cb_wrap == NULL || parse_cb_wrap == NULL) { 494 OPENSSL_free(add_cb_wrap); 495 OPENSSL_free(parse_cb_wrap); 496 return 0; 497 } 498 499 add_cb_wrap->add_arg = add_arg; 500 add_cb_wrap->add_cb = add_cb; 501 add_cb_wrap->free_cb = free_cb; 502 parse_cb_wrap->parse_arg = parse_arg; 503 parse_cb_wrap->parse_cb = parse_cb; 504 505 ret = ossl_tls_add_custom_ext_intern(ctx, NULL, role, ext_type, 506 context, 507 custom_ext_add_old_cb_wrap, 508 custom_ext_free_old_cb_wrap, 509 add_cb_wrap, 510 custom_ext_parse_old_cb_wrap, 511 parse_cb_wrap); 512 513 if (!ret) { 514 OPENSSL_free(add_cb_wrap); 515 OPENSSL_free(parse_cb_wrap); 516 } 517 518 return ret; 519 } 520 521 /* Application level functions to add the old custom extension callbacks */ 522 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type, 523 custom_ext_add_cb add_cb, 524 custom_ext_free_cb free_cb, 525 void *add_arg, 526 custom_ext_parse_cb parse_cb, void *parse_arg) 527 { 528 return add_old_custom_ext(ctx, ENDPOINT_CLIENT, ext_type, 529 SSL_EXT_TLS1_2_AND_BELOW_ONLY 530 | SSL_EXT_CLIENT_HELLO 531 | SSL_EXT_TLS1_2_SERVER_HELLO 532 | SSL_EXT_IGNORE_ON_RESUMPTION, 533 add_cb, free_cb, add_arg, parse_cb, parse_arg); 534 } 535 536 int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type, 537 custom_ext_add_cb add_cb, 538 custom_ext_free_cb free_cb, 539 void *add_arg, 540 custom_ext_parse_cb parse_cb, void *parse_arg) 541 { 542 return add_old_custom_ext(ctx, ENDPOINT_SERVER, ext_type, 543 SSL_EXT_TLS1_2_AND_BELOW_ONLY 544 | SSL_EXT_CLIENT_HELLO 545 | SSL_EXT_TLS1_2_SERVER_HELLO 546 | SSL_EXT_IGNORE_ON_RESUMPTION, 547 add_cb, free_cb, add_arg, parse_cb, parse_arg); 548 } 549 550 int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type, 551 unsigned int context, 552 SSL_custom_ext_add_cb_ex add_cb, 553 SSL_custom_ext_free_cb_ex free_cb, 554 void *add_arg, 555 SSL_custom_ext_parse_cb_ex parse_cb, void *parse_arg) 556 { 557 return ossl_tls_add_custom_ext_intern(ctx, NULL, ENDPOINT_BOTH, ext_type, 558 context, add_cb, free_cb, add_arg, 559 parse_cb, parse_arg); 560 } 561 562 int SSL_extension_supported(unsigned int ext_type) 563 { 564 switch (ext_type) { 565 /* Internally supported extensions. */ 566 case TLSEXT_TYPE_application_layer_protocol_negotiation: 567 case TLSEXT_TYPE_ec_point_formats: 568 case TLSEXT_TYPE_supported_groups: 569 case TLSEXT_TYPE_key_share: 570 #ifndef OPENSSL_NO_NEXTPROTONEG 571 case TLSEXT_TYPE_next_proto_neg: 572 #endif 573 case TLSEXT_TYPE_padding: 574 case TLSEXT_TYPE_renegotiate: 575 case TLSEXT_TYPE_max_fragment_length: 576 case TLSEXT_TYPE_server_name: 577 case TLSEXT_TYPE_session_ticket: 578 case TLSEXT_TYPE_signature_algorithms: 579 #ifndef OPENSSL_NO_SRP 580 case TLSEXT_TYPE_srp: 581 #endif 582 #ifndef OPENSSL_NO_OCSP 583 case TLSEXT_TYPE_status_request: 584 #endif 585 #ifndef OPENSSL_NO_CT 586 case TLSEXT_TYPE_signed_certificate_timestamp: 587 #endif 588 #ifndef OPENSSL_NO_SRTP 589 case TLSEXT_TYPE_use_srtp: 590 #endif 591 case TLSEXT_TYPE_encrypt_then_mac: 592 case TLSEXT_TYPE_supported_versions: 593 case TLSEXT_TYPE_extended_master_secret: 594 case TLSEXT_TYPE_psk_kex_modes: 595 case TLSEXT_TYPE_cookie: 596 case TLSEXT_TYPE_early_data: 597 case TLSEXT_TYPE_certificate_authorities: 598 case TLSEXT_TYPE_psk: 599 case TLSEXT_TYPE_post_handshake_auth: 600 case TLSEXT_TYPE_compress_certificate: 601 case TLSEXT_TYPE_client_cert_type: 602 case TLSEXT_TYPE_server_cert_type: 603 return 1; 604 default: 605 return 0; 606 } 607 } 608