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