ssl/statem/extensions_cust.c

   1 /*
   2  * Copyright 2014-2021 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 "statem_local.h"
  16
  17 typedef struct {
  18     void *add_arg;
  19     custom_ext_add_cb add_cb;
  20     custom_ext_free_cb free_cb;
  21 } custom_ext_add_cb_wrap;
  22
  23 typedef struct {
  24     void *parse_arg;
  25     custom_ext_parse_cb parse_cb;
  26 } custom_ext_parse_cb_wrap;
  27
  28 /*
  29  * Provide thin wrapper callbacks which convert new style arguments to old style
  30  */
  31 static int custom_ext_add_old_cb_wrap(SSL *s, unsigned int ext_type,
  32                                       unsigned int context,
  33                                       const unsigned char **out,
  34                                       size_t *outlen, X509 *x, size_t chainidx,
  35                                       int *al, void *add_arg)
  36 {
  37     custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg;
  38
  39     if (add_cb_wrap->add_cb == NULL)
  40         return 1;
  41
  42     return add_cb_wrap->add_cb(s, ext_type, out, outlen, al,
  43                                add_cb_wrap->add_arg);
  44 }
  45
  46 static void custom_ext_free_old_cb_wrap(SSL *s, unsigned int ext_type,
  47                                         unsigned int context,
  48                                         const unsigned char *out, void *add_arg)
  49 {
  50     custom_ext_add_cb_wrap *add_cb_wrap = (custom_ext_add_cb_wrap *)add_arg;
  51
  52     if (add_cb_wrap->free_cb == NULL)
  53         return;
  54
  55     add_cb_wrap->free_cb(s, ext_type, out, add_cb_wrap->add_arg);
  56 }
  57
  58 static int custom_ext_parse_old_cb_wrap(SSL *s, unsigned int ext_type,
  59                                         unsigned int context,
  60                                         const unsigned char *in,
  61                                         size_t inlen, X509 *x, size_t chainidx,
  62                                         int *al, void *parse_arg)
  63 {
  64     custom_ext_parse_cb_wrap *parse_cb_wrap =
  65         (custom_ext_parse_cb_wrap *)parse_arg;
  66
  67     if (parse_cb_wrap->parse_cb == NULL)
  68         return 1;
  69
  70     return parse_cb_wrap->parse_cb(s, ext_type, in, inlen, al,
  71                                    parse_cb_wrap->parse_arg);
  72 }
  73
  74 /*
  75  * Find a custom extension from the list. The |role| param is there to
  76  * support the legacy API where custom extensions for client and server could
  77  * be set independently on the same SSL_CTX. It is set to ENDPOINT_SERVER if we
  78  * are trying to find a method relevant to the server, ENDPOINT_CLIENT for the
  79  * client, or ENDPOINT_BOTH for either
  80  */
  81 custom_ext_method *custom_ext_find(const custom_ext_methods *exts,
  82                                    ENDPOINT role, unsigned int ext_type,
  83                                    size_t *idx)
  84 {
  85     size_t i;
  86     custom_ext_method *meth = exts->meths;
  87
  88     for (i = 0; i < exts->meths_count; i++, meth++) {
  89         if (ext_type == meth->ext_type
  90                 && (role == ENDPOINT_BOTH || role == meth->role
  91                     || meth->role == ENDPOINT_BOTH)) {
  92             if (idx != NULL)
  93                 *idx = i;
  94             return meth;
  95         }
  96     }
  97     return NULL;
  98 }
  99
 100 /*
 101  * Initialise custom extensions flags to indicate neither sent nor received.
 102  */
 103 void custom_ext_init(custom_ext_methods *exts)
 104 {
 105     size_t i;
 106     custom_ext_method *meth = exts->meths;
 107
 108     for (i = 0; i < exts->meths_count; i++, meth++)
 109         meth->ext_flags = 0;
 110 }
 111
 112 /* Pass received custom extension data to the application for parsing. */
 113 int custom_ext_parse(SSL_CONNECTION *s, unsigned int context,
 114                      unsigned int ext_type,
 115                      const unsigned char *ext_data, size_t ext_size, X509 *x,
 116                      size_t chainidx)
 117 {
 118     int al;
 119     custom_ext_methods *exts = &s->cert->custext;
 120     custom_ext_method *meth;
 121     ENDPOINT role = ENDPOINT_BOTH;
 122
 123     if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_2_SERVER_HELLO)) != 0)
 124         role = s->server ? ENDPOINT_SERVER : ENDPOINT_CLIENT;
 125
 126     meth = custom_ext_find(exts, role, ext_type, NULL);
 127     /* If not found return success */
 128     if (!meth)
 129         return 1;
 130
 131     /* Check if extension is defined for our protocol. If not, skip */
 132     if (!extension_is_relevant(s, meth->context, context))
 133         return 1;
 134
 135     if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO
 136                     | SSL_EXT_TLS1_3_SERVER_HELLO
 137                     | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS)) != 0) {
 138         /*
 139          * If it's ServerHello or EncryptedExtensions we can't have any
 140          * extensions not sent in ClientHello.
 141          */
 142         if ((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0) {
 143             SSLfatal(s, TLS1_AD_UNSUPPORTED_EXTENSION, SSL_R_BAD_EXTENSION);
 144             return 0;
 145         }
 146     }
 147
 148     /*
 149      * Extensions received in the ClientHello or CertificateRequest are marked
 150      * with the SSL_EXT_FLAG_RECEIVED. This is so we know to add the equivalent
 151      * extensions in the response messages
 152      */
 153     if ((context & (SSL_EXT_CLIENT_HELLO | SSL_EXT_TLS1_3_CERTIFICATE_REQUEST))
 154             != 0)
 155         meth->ext_flags |= SSL_EXT_FLAG_RECEIVED;
 156
 157     /* If no parse function set return success */
 158     if (meth->parse_cb == NULL)
 159         return 1;
 160
 161     if (meth->parse_cb(SSL_CONNECTION_GET_SSL(s), ext_type, context, ext_data,
 162                        ext_size, x, chainidx, &al, meth->parse_arg) <= 0) {
 163         SSLfatal(s, al, SSL_R_BAD_EXTENSION);
 164         return 0;
 165     }
 166
 167     return 1;
 168 }
 169
 170 /*
 171  * Request custom extension data from the application and add to the return
 172  * buffer.
 173  */
 174 int custom_ext_add(SSL_CONNECTION *s, int context, WPACKET *pkt, X509 *x,
 175                    size_t chainidx, int maxversion)
 176 {
 177     custom_ext_methods *exts = &s->cert->custext;
 178     custom_ext_method *meth;
 179     size_t i;
 180     int al;
 181     int for_comp = (context & SSL_EXT_TLS1_3_CERTIFICATE_COMPRESSION) != 0;
 182
 183     for (i = 0; i < exts->meths_count; i++) {
 184         const unsigned char *out = NULL;
 185         size_t outlen = 0;
 186
 187         meth = exts->meths + i;
 188
 189         if (!should_add_extension(s, meth->context, context, maxversion))
 190             continue;
 191
 192         if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO
 193                         | SSL_EXT_TLS1_3_SERVER_HELLO
 194                         | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS
 195                         | SSL_EXT_TLS1_3_CERTIFICATE
 196                         | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST)) != 0) {
 197             /* Only send extensions present in ClientHello/CertificateRequest */
 198             if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED))
 199                 continue;
 200         }
 201         /*
 202          * We skip it if the callback is absent - except for a ClientHello where
 203          * we add an empty extension.
 204          */
 205         if ((context & SSL_EXT_CLIENT_HELLO) == 0 && meth->add_cb == NULL)
 206             continue;
 207
 208         if (meth->add_cb != NULL) {
 209             int cb_retval = meth->add_cb(SSL_CONNECTION_GET_SSL(s),
 210                                          meth->ext_type, context, &out,
 211                                          &outlen, x, chainidx, &al,
 212                                          meth->add_arg);
 213
 214             if (cb_retval < 0) {
 215                 if (!for_comp)
 216                     SSLfatal(s, al, SSL_R_CALLBACK_FAILED);
 217                 return 0;       /* error */
 218             }
 219             if (cb_retval == 0)
 220                 continue;       /* skip this extension */
 221         }
 222
 223         if (!WPACKET_put_bytes_u16(pkt, meth->ext_type)
 224                 || !WPACKET_start_sub_packet_u16(pkt)
 225                 || (outlen > 0 && !WPACKET_memcpy(pkt, out, outlen))
 226                 || !WPACKET_close(pkt)) {
 227             if (!for_comp)
 228                 SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
 229             return 0;
 230         }
 231         if ((context & SSL_EXT_CLIENT_HELLO) != 0) {
 232             /*
 233              * We can't send duplicates: code logic should prevent this.
 234              */
 235             if (!ossl_assert((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0)) {
 236                 if (!for_comp)
 237                     SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
 238                 return 0;
 239             }
 240             /*
 241              * Indicate extension has been sent: this is both a sanity check to
 242              * ensure we don't send duplicate extensions and indicates that it
 243              * is not an error if the extension is present in ServerHello.
 244              */
 245             meth->ext_flags |= SSL_EXT_FLAG_SENT;
 246         }
 247         if (meth->free_cb != NULL)
 248             meth->free_cb(SSL_CONNECTION_GET_SSL(s), meth->ext_type, context,
 249                           out, meth->add_arg);
 250     }
 251     return 1;
 252 }
 253
 254 /* Copy the flags from src to dst for any extensions that exist in both */
 255 int custom_exts_copy_flags(custom_ext_methods *dst,
 256                            const custom_ext_methods *src)
 257 {
 258     size_t i;
 259     custom_ext_method *methsrc = src->meths;
 260
 261     for (i = 0; i < src->meths_count; i++, methsrc++) {
 262         custom_ext_method *methdst = custom_ext_find(dst, methsrc->role,
 263                                                      methsrc->ext_type, NULL);
 264
 265         if (methdst == NULL)
 266             continue;
 267
 268         methdst->ext_flags = methsrc->ext_flags;
 269     }
 270
 271     return 1;
 272 }
 273
 274 /* Copy table of custom extensions */
 275 int custom_exts_copy(custom_ext_methods *dst, const custom_ext_methods *src)
 276 {
 277     size_t i;
 278     int err = 0;
 279
 280     if (src->meths_count > 0) {
 281         dst->meths =
 282             OPENSSL_memdup(src->meths,
 283                            sizeof(*src->meths) * src->meths_count);
 284         if (dst->meths == NULL)
 285             return 0;
 286         dst->meths_count = src->meths_count;
 287
 288         for (i = 0; i < src->meths_count; i++) {
 289             custom_ext_method *methsrc = src->meths + i;
 290             custom_ext_method *methdst = dst->meths + i;
 291
 292             if (methsrc->add_cb != custom_ext_add_old_cb_wrap)
 293                 continue;
 294
 295             /*
 296              * We have found an old style API wrapper. We need to copy the
 297              * arguments too.
 298              */
 299
 300             if (err) {
 301                 methdst->add_arg = NULL;
 302                 methdst->parse_arg = NULL;
 303                 continue;
 304             }
 305
 306             methdst->add_arg = OPENSSL_memdup(methsrc->add_arg,
 307                                               sizeof(custom_ext_add_cb_wrap));
 308             methdst->parse_arg = OPENSSL_memdup(methsrc->parse_arg,
 309                                             sizeof(custom_ext_parse_cb_wrap));
 310
 311             if (methdst->add_arg == NULL || methdst->parse_arg == NULL)
 312                 err = 1;
 313         }
 314     }
 315
 316     if (err) {
 317         custom_exts_free(dst);
 318         return 0;
 319     }
 320
 321     return 1;
 322 }
 323
 324 void custom_exts_free(custom_ext_methods *exts)
 325 {
 326     size_t i;
 327     custom_ext_method *meth;
 328
 329     for (i = 0, meth = exts->meths; i < exts->meths_count; i++, meth++) {
 330         if (meth->add_cb != custom_ext_add_old_cb_wrap)
 331             continue;
 332
 333         /* Old style API wrapper. Need to free the arguments too */
 334         OPENSSL_free(meth->add_arg);
 335         OPENSSL_free(meth->parse_arg);
 336     }
 337     OPENSSL_free(exts->meths);
 338 }
 339
 340 /* Return true if a client custom extension exists, false otherwise */
 341 int SSL_CTX_has_client_custom_ext(const SSL_CTX *ctx, unsigned int ext_type)
 342 {
 343     return custom_ext_find(&ctx->cert->custext, ENDPOINT_CLIENT, ext_type,
 344                            NULL) != NULL;
 345 }
 346
 347 int ossl_tls_add_custom_ext_intern(SSL_CTX *ctx, custom_ext_methods *exts,
 348                                    ENDPOINT role, unsigned int ext_type,
 349                                    unsigned int context,
 350                                    SSL_custom_ext_add_cb_ex add_cb,
 351                                    SSL_custom_ext_free_cb_ex free_cb,
 352                                    void *add_arg,
 353                                    SSL_custom_ext_parse_cb_ex parse_cb,
 354                                    void *parse_arg)
 355 {
 356     custom_ext_method *meth, *tmp;
 357
 358     /*
 359      * Check application error: if add_cb is not set free_cb will never be
 360      * called.
 361      */
 362     if (add_cb == NULL && free_cb != NULL)
 363         return 0;
 364
 365     if (exts == NULL)
 366         exts = &ctx->cert->custext;
 367
 368 #ifndef OPENSSL_NO_CT
 369     /*
 370      * We don't want applications registering callbacks for SCT extensions
 371      * whilst simultaneously using the built-in SCT validation features, as
 372      * these two things may not play well together.
 373      */
 374     if (ext_type == TLSEXT_TYPE_signed_certificate_timestamp
 375             && (context & SSL_EXT_CLIENT_HELLO) != 0
 376             && ctx != NULL
 377             && SSL_CTX_ct_is_enabled(ctx))
 378         return 0;
 379 #endif
 380
 381     /*
 382      * Don't add if extension supported internally, but make exception
 383      * for extension types that previously were not supported, but now are.
 384      */
 385     if (SSL_extension_supported(ext_type)
 386             && ext_type != TLSEXT_TYPE_signed_certificate_timestamp)
 387         return 0;
 388
 389     /* Extension type must fit in 16 bits */
 390     if (ext_type > 0xffff)
 391         return 0;
 392     /* Search for duplicate */
 393     if (custom_ext_find(exts, role, ext_type, NULL))
 394         return 0;
 395     tmp = OPENSSL_realloc(exts->meths,
 396                           (exts->meths_count + 1) * sizeof(custom_ext_method));
 397     if (tmp == NULL)
 398         return 0;
 399
 400     exts->meths = tmp;
 401     meth = exts->meths + exts->meths_count;
 402     memset(meth, 0, sizeof(*meth));
 403     meth->role = role;
 404     meth->context = context;
 405     meth->parse_cb = parse_cb;
 406     meth->add_cb = add_cb;
 407     meth->free_cb = free_cb;
 408     meth->ext_type = ext_type;
 409     meth->add_arg = add_arg;
 410     meth->parse_arg = parse_arg;
 411     exts->meths_count++;
 412     return 1;
 413 }
 414
 415 static int add_old_custom_ext(SSL_CTX *ctx, ENDPOINT role,
 416                               unsigned int ext_type,
 417                               unsigned int context,
 418                               custom_ext_add_cb add_cb,
 419                               custom_ext_free_cb free_cb,
 420                               void *add_arg,
 421                               custom_ext_parse_cb parse_cb, void *parse_arg)
 422 {
 423     custom_ext_add_cb_wrap *add_cb_wrap
 424         = OPENSSL_malloc(sizeof(*add_cb_wrap));
 425     custom_ext_parse_cb_wrap *parse_cb_wrap
 426         = OPENSSL_malloc(sizeof(*parse_cb_wrap));
 427     int ret;
 428
 429     if (add_cb_wrap == NULL || parse_cb_wrap == NULL) {
 430         OPENSSL_free(add_cb_wrap);
 431         OPENSSL_free(parse_cb_wrap);
 432         return 0;
 433     }
 434
 435     add_cb_wrap->add_arg = add_arg;
 436     add_cb_wrap->add_cb = add_cb;
 437     add_cb_wrap->free_cb = free_cb;
 438     parse_cb_wrap->parse_arg = parse_arg;
 439     parse_cb_wrap->parse_cb = parse_cb;
 440
 441     ret = ossl_tls_add_custom_ext_intern(ctx, NULL, role, ext_type,
 442                                          context,
 443                                          custom_ext_add_old_cb_wrap,
 444                                          custom_ext_free_old_cb_wrap,
 445                                          add_cb_wrap,
 446                                          custom_ext_parse_old_cb_wrap,
 447                                          parse_cb_wrap);
 448
 449     if (!ret) {
 450         OPENSSL_free(add_cb_wrap);
 451         OPENSSL_free(parse_cb_wrap);
 452     }
 453
 454     return ret;
 455 }
 456
 457 /* Application level functions to add the old custom extension callbacks */
 458 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 459                                   custom_ext_add_cb add_cb,
 460                                   custom_ext_free_cb free_cb,
 461                                   void *add_arg,
 462                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 463 {
 464     return add_old_custom_ext(ctx, ENDPOINT_CLIENT, ext_type,
 465                               SSL_EXT_TLS1_2_AND_BELOW_ONLY
 466                               | SSL_EXT_CLIENT_HELLO
 467                               | SSL_EXT_TLS1_2_SERVER_HELLO
 468                               | SSL_EXT_IGNORE_ON_RESUMPTION,
 469                               add_cb, free_cb, add_arg, parse_cb, parse_arg);
 470 }
 471
 472 int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 473                                   custom_ext_add_cb add_cb,
 474                                   custom_ext_free_cb free_cb,
 475                                   void *add_arg,
 476                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 477 {
 478     return add_old_custom_ext(ctx, ENDPOINT_SERVER, ext_type,
 479                               SSL_EXT_TLS1_2_AND_BELOW_ONLY
 480                               | SSL_EXT_CLIENT_HELLO
 481                               | SSL_EXT_TLS1_2_SERVER_HELLO
 482                               | SSL_EXT_IGNORE_ON_RESUMPTION,
 483                               add_cb, free_cb, add_arg, parse_cb, parse_arg);
 484 }
 485
 486 int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 487                            unsigned int context,
 488                            SSL_custom_ext_add_cb_ex add_cb,
 489                            SSL_custom_ext_free_cb_ex free_cb,
 490                            void *add_arg,
 491                            SSL_custom_ext_parse_cb_ex parse_cb, void *parse_arg)
 492 {
 493     return ossl_tls_add_custom_ext_intern(ctx, NULL, ENDPOINT_BOTH, ext_type,
 494                                           context, add_cb, free_cb, add_arg,
 495                                           parse_cb, parse_arg);
 496 }
 497
 498 int SSL_extension_supported(unsigned int ext_type)
 499 {
 500     switch (ext_type) {
 501         /* Internally supported extensions. */
 502     case TLSEXT_TYPE_application_layer_protocol_negotiation:
 503     case TLSEXT_TYPE_ec_point_formats:
 504     case TLSEXT_TYPE_supported_groups:
 505     case TLSEXT_TYPE_key_share:
 506 #ifndef OPENSSL_NO_NEXTPROTONEG
 507     case TLSEXT_TYPE_next_proto_neg:
 508 #endif
 509     case TLSEXT_TYPE_padding:
 510     case TLSEXT_TYPE_renegotiate:
 511     case TLSEXT_TYPE_max_fragment_length:
 512     case TLSEXT_TYPE_server_name:
 513     case TLSEXT_TYPE_session_ticket:
 514     case TLSEXT_TYPE_signature_algorithms:
 515 #ifndef OPENSSL_NO_SRP
 516     case TLSEXT_TYPE_srp:
 517 #endif
 518 #ifndef OPENSSL_NO_OCSP
 519     case TLSEXT_TYPE_status_request:
 520 #endif
 521 #ifndef OPENSSL_NO_CT
 522     case TLSEXT_TYPE_signed_certificate_timestamp:
 523 #endif
 524 #ifndef OPENSSL_NO_SRTP
 525     case TLSEXT_TYPE_use_srtp:
 526 #endif
 527     case TLSEXT_TYPE_encrypt_then_mac:
 528     case TLSEXT_TYPE_supported_versions:
 529     case TLSEXT_TYPE_extended_master_secret:
 530     case TLSEXT_TYPE_psk_kex_modes:
 531     case TLSEXT_TYPE_cookie:
 532     case TLSEXT_TYPE_early_data:
 533     case TLSEXT_TYPE_certificate_authorities:
 534     case TLSEXT_TYPE_psk:
 535     case TLSEXT_TYPE_post_handshake_auth:
 536     case TLSEXT_TYPE_compress_certificate:
 537         return 1;
 538     default:
 539         return 0;
 540     }
 541 }