ssl/statem/extensions_cust.c

   1 /*
   2  * Copyright 2014-2018 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_locl.h"
  14 #include "internal/cryptlib.h"
  15 #include "statem_locl.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_F_CUSTOM_EXT_PARSE,
 143                      SSL_R_BAD_EXTENSION);
 144             return 0;
 145         }
 146     }
 147
 148     /*
 149      * Extensions received in the ClientHello are marked with the
 150      * SSL_EXT_FLAG_RECEIVED. This is so we know to add the equivalent
 151      * extensions in the ServerHello/EncryptedExtensions message
 152      */
 153     if ((context & SSL_EXT_CLIENT_HELLO) != 0)
 154         meth->ext_flags |= SSL_EXT_FLAG_RECEIVED;
 155
 156     /* If no parse function set return success */
 157     if (!meth->parse_cb)
 158         return 1;
 159
 160     if (meth->parse_cb(s, ext_type, context, ext_data, ext_size, x, chainidx,
 161                        &al, meth->parse_arg) <= 0) {
 162         SSLfatal(s, al, SSL_F_CUSTOM_EXT_PARSE, SSL_R_BAD_EXTENSION);
 163         return 0;
 164     }
 165
 166     return 1;
 167 }
 168
 169 /*
 170  * Request custom extension data from the application and add to the return
 171  * buffer.
 172  */
 173 int custom_ext_add(SSL *s, int context, WPACKET *pkt, X509 *x, size_t chainidx,
 174                    int maxversion)
 175 {
 176     custom_ext_methods *exts = &s->cert->custext;
 177     custom_ext_method *meth;
 178     size_t i;
 179     int al;
 180
 181     for (i = 0; i < exts->meths_count; i++) {
 182         const unsigned char *out = NULL;
 183         size_t outlen = 0;
 184
 185         meth = exts->meths + i;
 186
 187         if (!should_add_extension(s, meth->context, context, maxversion))
 188             continue;
 189
 190         if ((context & (SSL_EXT_TLS1_2_SERVER_HELLO
 191                         | SSL_EXT_TLS1_3_SERVER_HELLO
 192                         | SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS
 193                         | SSL_EXT_TLS1_3_CERTIFICATE
 194                         | SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST)) != 0) {
 195             /* Only send extensions present in ClientHello. */
 196             if (!(meth->ext_flags & SSL_EXT_FLAG_RECEIVED))
 197                 continue;
 198         }
 199         /*
 200          * We skip it if the callback is absent - except for a ClientHello where
 201          * we add an empty extension.
 202          */
 203         if ((context & SSL_EXT_CLIENT_HELLO) == 0 && meth->add_cb == NULL)
 204             continue;
 205
 206         if (meth->add_cb != NULL) {
 207             int cb_retval = meth->add_cb(s, meth->ext_type, context, &out,
 208                                          &outlen, x, chainidx, &al,
 209                                          meth->add_arg);
 210
 211             if (cb_retval < 0) {
 212                 SSLfatal(s, al, SSL_F_CUSTOM_EXT_ADD, SSL_R_CALLBACK_FAILED);
 213                 return 0;       /* error */
 214             }
 215             if (cb_retval == 0)
 216                 continue;       /* skip this extension */
 217         }
 218
 219         if (!WPACKET_put_bytes_u16(pkt, meth->ext_type)
 220                 || !WPACKET_start_sub_packet_u16(pkt)
 221                 || (outlen > 0 && !WPACKET_memcpy(pkt, out, outlen))
 222                 || !WPACKET_close(pkt)) {
 223             SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_CUSTOM_EXT_ADD,
 224                      ERR_R_INTERNAL_ERROR);
 225             return 0;
 226         }
 227         if ((context & SSL_EXT_CLIENT_HELLO) != 0) {
 228             /*
 229              * We can't send duplicates: code logic should prevent this.
 230              */
 231             if (!ossl_assert((meth->ext_flags & SSL_EXT_FLAG_SENT) == 0)) {
 232                 SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_CUSTOM_EXT_ADD,
 233                          ERR_R_INTERNAL_ERROR);
 234                 return 0;
 235             }
 236             /*
 237              * Indicate extension has been sent: this is both a sanity check to
 238              * ensure we don't send duplicate extensions and indicates that it
 239              * is not an error if the extension is present in ServerHello.
 240              */
 241             meth->ext_flags |= SSL_EXT_FLAG_SENT;
 242         }
 243         if (meth->free_cb != NULL)
 244             meth->free_cb(s, meth->ext_type, context, out, meth->add_arg);
 245     }
 246     return 1;
 247 }
 248
 249 /* Copy the flags from src to dst for any extensions that exist in both */
 250 int custom_exts_copy_flags(custom_ext_methods *dst,
 251                            const custom_ext_methods *src)
 252 {
 253     size_t i;
 254     custom_ext_method *methsrc = src->meths;
 255
 256     for (i = 0; i < src->meths_count; i++, methsrc++) {
 257         custom_ext_method *methdst = custom_ext_find(dst, methsrc->role,
 258                                                      methsrc->ext_type, NULL);
 259
 260         if (methdst == NULL)
 261             continue;
 262
 263         methdst->ext_flags = methsrc->ext_flags;
 264     }
 265
 266     return 1;
 267 }
 268
 269 /* Copy table of custom extensions */
 270 int custom_exts_copy(custom_ext_methods *dst, const custom_ext_methods *src)
 271 {
 272     size_t i;
 273     int err = 0;
 274
 275     if (src->meths_count > 0) {
 276         dst->meths =
 277             OPENSSL_memdup(src->meths,
 278                            sizeof(*src->meths) * src->meths_count);
 279         if (dst->meths == NULL)
 280             return 0;
 281         dst->meths_count = src->meths_count;
 282
 283         for (i = 0; i < src->meths_count; i++) {
 284             custom_ext_method *methsrc = src->meths + i;
 285             custom_ext_method *methdst = dst->meths + i;
 286
 287             if (methsrc->add_cb != custom_ext_add_old_cb_wrap)
 288                 continue;
 289
 290             /*
 291              * We have found an old style API wrapper. We need to copy the
 292              * arguments too.
 293              */
 294
 295             if (err) {
 296                 methdst->add_arg = NULL;
 297                 methdst->parse_arg = NULL;
 298                 continue;
 299             }
 300
 301             methdst->add_arg = OPENSSL_memdup(methsrc->add_arg,
 302                                               sizeof(custom_ext_add_cb_wrap));
 303             methdst->parse_arg = OPENSSL_memdup(methsrc->parse_arg,
 304                                             sizeof(custom_ext_parse_cb_wrap));
 305
 306             if (methdst->add_arg == NULL || methdst->parse_arg == NULL)
 307                 err = 1;
 308         }
 309     }
 310
 311     if (err) {
 312         custom_exts_free(dst);
 313         return 0;
 314     }
 315
 316     return 1;
 317 }
 318
 319 void custom_exts_free(custom_ext_methods *exts)
 320 {
 321     size_t i;
 322     custom_ext_method *meth;
 323
 324     for (i = 0, meth = exts->meths; i < exts->meths_count; i++, meth++) {
 325         if (meth->add_cb != custom_ext_add_old_cb_wrap)
 326             continue;
 327
 328         /* Old style API wrapper. Need to free the arguments too */
 329         OPENSSL_free(meth->add_arg);
 330         OPENSSL_free(meth->parse_arg);
 331     }
 332     OPENSSL_free(exts->meths);
 333 }
 334
 335 /* Return true if a client custom extension exists, false otherwise */
 336 int SSL_CTX_has_client_custom_ext(const SSL_CTX *ctx, unsigned int ext_type)
 337 {
 338     return custom_ext_find(&ctx->cert->custext, ENDPOINT_CLIENT, ext_type,
 339                            NULL) != NULL;
 340 }
 341
 342 static int add_custom_ext_intern(SSL_CTX *ctx, ENDPOINT role,
 343                                  unsigned int ext_type,
 344                                  unsigned int context,
 345                                  SSL_custom_ext_add_cb_ex add_cb,
 346                                  SSL_custom_ext_free_cb_ex free_cb,
 347                                  void *add_arg,
 348                                  SSL_custom_ext_parse_cb_ex parse_cb,
 349                                  void *parse_arg)
 350 {
 351     custom_ext_methods *exts = &ctx->cert->custext;
 352     custom_ext_method *meth, *tmp;
 353
 354     /*
 355      * Check application error: if add_cb is not set free_cb will never be
 356      * called.
 357      */
 358     if (add_cb == NULL && free_cb != NULL)
 359         return 0;
 360
 361 #ifndef OPENSSL_NO_CT
 362     /*
 363      * We don't want applications registering callbacks for SCT extensions
 364      * whilst simultaneously using the built-in SCT validation features, as
 365      * these two things may not play well together.
 366      */
 367     if (ext_type == TLSEXT_TYPE_signed_certificate_timestamp
 368             && (context & SSL_EXT_CLIENT_HELLO) != 0
 369             && SSL_CTX_ct_is_enabled(ctx))
 370         return 0;
 371 #endif
 372
 373     /*
 374      * Don't add if extension supported internally, but make exception
 375      * for extension types that previously were not supported, but now are.
 376      */
 377     if (SSL_extension_supported(ext_type)
 378             && ext_type != TLSEXT_TYPE_signed_certificate_timestamp)
 379         return 0;
 380
 381     /* Extension type must fit in 16 bits */
 382     if (ext_type > 0xffff)
 383         return 0;
 384     /* Search for duplicate */
 385     if (custom_ext_find(exts, role, ext_type, NULL))
 386         return 0;
 387     tmp = OPENSSL_realloc(exts->meths,
 388                           (exts->meths_count + 1) * sizeof(custom_ext_method));
 389     if (tmp == NULL)
 390         return 0;
 391
 392     exts->meths = tmp;
 393     meth = exts->meths + exts->meths_count;
 394     memset(meth, 0, sizeof(*meth));
 395     meth->role = role;
 396     meth->context = context;
 397     meth->parse_cb = parse_cb;
 398     meth->add_cb = add_cb;
 399     meth->free_cb = free_cb;
 400     meth->ext_type = ext_type;
 401     meth->add_arg = add_arg;
 402     meth->parse_arg = parse_arg;
 403     exts->meths_count++;
 404     return 1;
 405 }
 406
 407 static int add_old_custom_ext(SSL_CTX *ctx, ENDPOINT role,
 408                               unsigned int ext_type,
 409                               unsigned int context,
 410                               custom_ext_add_cb add_cb,
 411                               custom_ext_free_cb free_cb,
 412                               void *add_arg,
 413                               custom_ext_parse_cb parse_cb, void *parse_arg)
 414 {
 415     custom_ext_add_cb_wrap *add_cb_wrap
 416         = OPENSSL_malloc(sizeof(*add_cb_wrap));
 417     custom_ext_parse_cb_wrap *parse_cb_wrap
 418         = OPENSSL_malloc(sizeof(*parse_cb_wrap));
 419     int ret;
 420
 421     if (add_cb_wrap == NULL || parse_cb_wrap == NULL) {
 422         OPENSSL_free(add_cb_wrap);
 423         OPENSSL_free(parse_cb_wrap);
 424         return 0;
 425     }
 426
 427     add_cb_wrap->add_arg = add_arg;
 428     add_cb_wrap->add_cb = add_cb;
 429     add_cb_wrap->free_cb = free_cb;
 430     parse_cb_wrap->parse_arg = parse_arg;
 431     parse_cb_wrap->parse_cb = parse_cb;
 432
 433     ret = add_custom_ext_intern(ctx, role, ext_type,
 434                                 context,
 435                                 custom_ext_add_old_cb_wrap,
 436                                 custom_ext_free_old_cb_wrap,
 437                                 add_cb_wrap,
 438                                 custom_ext_parse_old_cb_wrap,
 439                                 parse_cb_wrap);
 440
 441     if (!ret) {
 442         OPENSSL_free(add_cb_wrap);
 443         OPENSSL_free(parse_cb_wrap);
 444     }
 445
 446     return ret;
 447 }
 448
 449 /* Application level functions to add the old custom extension callbacks */
 450 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 451                                   custom_ext_add_cb add_cb,
 452                                   custom_ext_free_cb free_cb,
 453                                   void *add_arg,
 454                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 455 {
 456     return add_old_custom_ext(ctx, ENDPOINT_CLIENT, ext_type,
 457                               SSL_EXT_TLS1_2_AND_BELOW_ONLY
 458                               | SSL_EXT_CLIENT_HELLO
 459                               | SSL_EXT_TLS1_2_SERVER_HELLO
 460                               | SSL_EXT_IGNORE_ON_RESUMPTION,
 461                               add_cb, free_cb, add_arg, parse_cb, parse_arg);
 462 }
 463
 464 int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 465                                   custom_ext_add_cb add_cb,
 466                                   custom_ext_free_cb free_cb,
 467                                   void *add_arg,
 468                                   custom_ext_parse_cb parse_cb, void *parse_arg)
 469 {
 470     return add_old_custom_ext(ctx, ENDPOINT_SERVER, ext_type,
 471                               SSL_EXT_TLS1_2_AND_BELOW_ONLY
 472                               | SSL_EXT_CLIENT_HELLO
 473                               | SSL_EXT_TLS1_2_SERVER_HELLO
 474                               | SSL_EXT_IGNORE_ON_RESUMPTION,
 475                               add_cb, free_cb, add_arg, parse_cb, parse_arg);
 476 }
 477
 478 int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
 479                            unsigned int context,
 480                            SSL_custom_ext_add_cb_ex add_cb,
 481                            SSL_custom_ext_free_cb_ex free_cb,
 482                            void *add_arg,
 483                            SSL_custom_ext_parse_cb_ex parse_cb, void *parse_arg)
 484 {
 485     return add_custom_ext_intern(ctx, ENDPOINT_BOTH, ext_type, context, add_cb,
 486                                  free_cb, add_arg, parse_cb, parse_arg);
 487 }
 488
 489 int SSL_extension_supported(unsigned int ext_type)
 490 {
 491     switch (ext_type) {
 492         /* Internally supported extensions. */
 493     case TLSEXT_TYPE_application_layer_protocol_negotiation:
 494 #ifndef OPENSSL_NO_EC
 495     case TLSEXT_TYPE_ec_point_formats:
 496     case TLSEXT_TYPE_supported_groups:
 497     case TLSEXT_TYPE_key_share:
 498 #endif
 499 #ifndef OPENSSL_NO_NEXTPROTONEG
 500     case TLSEXT_TYPE_next_proto_neg:
 501 #endif
 502     case TLSEXT_TYPE_padding:
 503     case TLSEXT_TYPE_renegotiate:
 504     case TLSEXT_TYPE_max_fragment_length:
 505     case TLSEXT_TYPE_server_name:
 506     case TLSEXT_TYPE_session_ticket:
 507     case TLSEXT_TYPE_signature_algorithms:
 508 #ifndef OPENSSL_NO_SRP
 509     case TLSEXT_TYPE_srp:
 510 #endif
 511 #ifndef OPENSSL_NO_OCSP
 512     case TLSEXT_TYPE_status_request:
 513 #endif
 514 #ifndef OPENSSL_NO_CT
 515     case TLSEXT_TYPE_signed_certificate_timestamp:
 516 #endif
 517 #ifndef OPENSSL_NO_SRTP
 518     case TLSEXT_TYPE_use_srtp:
 519 #endif
 520     case TLSEXT_TYPE_encrypt_then_mac:
 521     case TLSEXT_TYPE_supported_versions:
 522     case TLSEXT_TYPE_extended_master_secret:
 523     case TLSEXT_TYPE_psk_kex_modes:
 524     case TLSEXT_TYPE_cookie:
 525     case TLSEXT_TYPE_early_data:
 526     case TLSEXT_TYPE_certificate_authorities:
 527     case TLSEXT_TYPE_psk:
 528     case TLSEXT_TYPE_post_handshake_auth:
 529         return 1;
 530     default:
 531         return 0;
 532     }
 533 }