crypto/ts/ts_rsp_verify.c

   1 /*
   2  * Copyright 2006-2020 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 #include <stdio.h>
  11 #include "internal/cryptlib.h"
  12 #include <openssl/objects.h>
  13 #include <openssl/ts.h>
  14 #include <openssl/pkcs7.h>
  15 #include "ts_local.h"
  16 #include "crypto/ess.h"
  17
  18 DEFINE_STACK_OF(ESS_CERT_ID)
  19 DEFINE_STACK_OF(ESS_CERT_ID_V2)
  20
  21 static int ts_verify_cert(X509_STORE *store, STACK_OF(X509) *untrusted,
  22                           X509 *signer, STACK_OF(X509) **chain);
  23 static int ts_check_signing_certs(PKCS7_SIGNER_INFO *si,
  24                                   STACK_OF(X509) *chain);
  25
  26 static int int_ts_RESP_verify_token(TS_VERIFY_CTX *ctx,
  27                                     PKCS7 *token, TS_TST_INFO *tst_info);
  28 static int ts_check_status_info(TS_RESP *response);
  29 static char *ts_get_status_text(STACK_OF(ASN1_UTF8STRING) *text);
  30 static int ts_check_policy(const ASN1_OBJECT *req_oid,
  31                            const TS_TST_INFO *tst_info);
  32 static int ts_compute_imprint(BIO *data, TS_TST_INFO *tst_info,
  33                               X509_ALGOR **md_alg,
  34                               unsigned char **imprint, unsigned *imprint_len);
  35 static int ts_check_imprints(X509_ALGOR *algor_a,
  36                              const unsigned char *imprint_a, unsigned len_a,
  37                              TS_TST_INFO *tst_info);
  38 static int ts_check_nonces(const ASN1_INTEGER *a, TS_TST_INFO *tst_info);
  39 static int ts_check_signer_name(GENERAL_NAME *tsa_name, X509 *signer);
  40 static int ts_find_name(STACK_OF(GENERAL_NAME) *gen_names,
  41                         GENERAL_NAME *name);
  42
  43 /*
  44  * This must be large enough to hold all values in ts_status_text (with
  45  * comma separator) or all text fields in ts_failure_info (also with comma).
  46  */
  47 #define TS_STATUS_BUF_SIZE      256
  48
  49 /*
  50  * Local mapping between response codes and descriptions.
  51  */
  52 static const char *ts_status_text[] = {
  53     "granted",
  54     "grantedWithMods",
  55     "rejection",
  56     "waiting",
  57     "revocationWarning",
  58     "revocationNotification"
  59 };
  60
  61 #define TS_STATUS_TEXT_SIZE     OSSL_NELEM(ts_status_text)
  62
  63 static struct {
  64     int code;
  65     const char *text;
  66 } ts_failure_info[] = {
  67     {TS_INFO_BAD_ALG, "badAlg"},
  68     {TS_INFO_BAD_REQUEST, "badRequest"},
  69     {TS_INFO_BAD_DATA_FORMAT, "badDataFormat"},
  70     {TS_INFO_TIME_NOT_AVAILABLE, "timeNotAvailable"},
  71     {TS_INFO_UNACCEPTED_POLICY, "unacceptedPolicy"},
  72     {TS_INFO_UNACCEPTED_EXTENSION, "unacceptedExtension"},
  73     {TS_INFO_ADD_INFO_NOT_AVAILABLE, "addInfoNotAvailable"},
  74     {TS_INFO_SYSTEM_FAILURE, "systemFailure"}
  75 };
  76
  77
  78 /*-
  79  * This function carries out the following tasks:
  80  *      - Checks if there is one and only one signer.
  81  *      - Search for the signing certificate in 'certs' and in the response.
  82  *      - Check the extended key usage and key usage fields of the signer
  83  *      certificate (done by the path validation).
  84  *      - Build and validate the certificate path.
  85  *      - Check if the certificate path meets the requirements of the
  86  *      SigningCertificate ESS signed attribute.
  87  *      - Verify the signature value.
  88  *      - Returns the signer certificate in 'signer', if 'signer' is not NULL.
  89  */
  90 int TS_RESP_verify_signature(PKCS7 *token, STACK_OF(X509) *certs,
  91                              X509_STORE *store, X509 **signer_out)
  92 {
  93     STACK_OF(PKCS7_SIGNER_INFO) *sinfos = NULL;
  94     PKCS7_SIGNER_INFO *si;
  95     STACK_OF(X509) *signers = NULL;
  96     X509 *signer;
  97     STACK_OF(X509) *chain = NULL;
  98     char buf[4096];
  99     int i, j = 0, ret = 0;
 100     BIO *p7bio = NULL;
 101
 102     /* Some sanity checks first. */
 103     if (!token) {
 104         TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_INVALID_NULL_POINTER);
 105         goto err;
 106     }
 107     if (!PKCS7_type_is_signed(token)) {
 108         TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_WRONG_CONTENT_TYPE);
 109         goto err;
 110     }
 111     sinfos = PKCS7_get_signer_info(token);
 112     if (!sinfos || sk_PKCS7_SIGNER_INFO_num(sinfos) != 1) {
 113         TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_THERE_MUST_BE_ONE_SIGNER);
 114         goto err;
 115     }
 116     si = sk_PKCS7_SIGNER_INFO_value(sinfos, 0);
 117     if (PKCS7_get_detached(token)) {
 118         TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_NO_CONTENT);
 119         goto err;
 120     }
 121
 122     /*
 123      * Get hold of the signer certificate, search only internal certificates
 124      * if it was requested.
 125      */
 126     signers = PKCS7_get0_signers(token, certs, 0);
 127     if (!signers || sk_X509_num(signers) != 1)
 128         goto err;
 129     signer = sk_X509_value(signers, 0);
 130
 131     if (!ts_verify_cert(store, certs, signer, &chain))
 132         goto err;
 133     if (!ts_check_signing_certs(si, chain))
 134         goto err;
 135     p7bio = PKCS7_dataInit(token, NULL);
 136
 137     /* We now have to 'read' from p7bio to calculate digests etc. */
 138     while ((i = BIO_read(p7bio, buf, sizeof(buf))) > 0)
 139         continue;
 140
 141     j = PKCS7_signatureVerify(p7bio, token, si, signer);
 142     if (j <= 0) {
 143         TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_SIGNATURE_FAILURE);
 144         goto err;
 145     }
 146
 147     if (signer_out) {
 148         *signer_out = signer;
 149         X509_up_ref(signer);
 150     }
 151     ret = 1;
 152
 153  err:
 154     BIO_free_all(p7bio);
 155     sk_X509_pop_free(chain, X509_free);
 156     sk_X509_free(signers);
 157
 158     return ret;
 159 }
 160
 161 /*
 162  * The certificate chain is returned in chain. Caller is responsible for
 163  * freeing the vector.
 164  */
 165 static int ts_verify_cert(X509_STORE *store, STACK_OF(X509) *untrusted,
 166                           X509 *signer, STACK_OF(X509) **chain)
 167 {
 168     X509_STORE_CTX *cert_ctx = NULL;
 169     int i;
 170     int ret = 0;
 171
 172     *chain = NULL;
 173     cert_ctx = X509_STORE_CTX_new();
 174     if (cert_ctx == NULL) {
 175         TSerr(TS_F_TS_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
 176         goto err;
 177     }
 178     if (!X509_STORE_CTX_init(cert_ctx, store, signer, untrusted))
 179         goto end;
 180     X509_STORE_CTX_set_purpose(cert_ctx, X509_PURPOSE_TIMESTAMP_SIGN);
 181     i = X509_verify_cert(cert_ctx);
 182     if (i <= 0) {
 183         int j = X509_STORE_CTX_get_error(cert_ctx);
 184         TSerr(TS_F_TS_VERIFY_CERT, TS_R_CERTIFICATE_VERIFY_ERROR);
 185         ERR_add_error_data(2, "Verify error:",
 186                            X509_verify_cert_error_string(j));
 187         goto err;
 188     }
 189     *chain = X509_STORE_CTX_get1_chain(cert_ctx);
 190     ret = 1;
 191     goto end;
 192
 193 err:
 194     ret = 0;
 195
 196 end:
 197     X509_STORE_CTX_free(cert_ctx);
 198     return ret;
 199 }
 200
 201 static int ts_check_signing_certs(PKCS7_SIGNER_INFO *si,
 202                                   STACK_OF(X509) *chain)
 203 {
 204     ESS_SIGNING_CERT *ss = ESS_SIGNING_CERT_get(si);
 205     STACK_OF(ESS_CERT_ID) *cert_ids = NULL;
 206     ESS_SIGNING_CERT_V2 *ssv2 = ESS_SIGNING_CERT_V2_get(si);
 207     STACK_OF(ESS_CERT_ID_V2) *cert_ids_v2 = NULL;
 208     X509 *cert;
 209     int i = 0;
 210     int ret = 0;
 211
 212     if (ss != NULL) {
 213         cert_ids = ss->cert_ids;
 214         cert = sk_X509_value(chain, 0);
 215         if (ess_find_cert(cert_ids, cert) != 0)
 216             goto err;
 217
 218         /*
 219          * Check the other certificates of the chain if there are more than one
 220          * certificate ids in cert_ids.
 221          */
 222         if (sk_ESS_CERT_ID_num(cert_ids) > 1) {
 223             for (i = 1; i < sk_X509_num(chain); ++i) {
 224                 cert = sk_X509_value(chain, i);
 225                 if (ess_find_cert(cert_ids, cert) < 0)
 226                     goto err;
 227             }
 228         }
 229     } else if (ssv2 != NULL) {
 230         cert_ids_v2 = ssv2->cert_ids;
 231         cert = sk_X509_value(chain, 0);
 232         if (ess_find_cert_v2(cert_ids_v2, cert) != 0)
 233             goto err;
 234
 235         /*
 236          * Check the other certificates of the chain if there are more than one
 237          * certificate ids in cert_ids.
 238          */
 239         if (sk_ESS_CERT_ID_V2_num(cert_ids_v2) > 1) {
 240             for (i = 1; i < sk_X509_num(chain); ++i) {
 241                 cert = sk_X509_value(chain, i);
 242                 if (ess_find_cert_v2(cert_ids_v2, cert) < 0)
 243                     goto err;
 244             }
 245         }
 246     } else {
 247         goto err;
 248     }
 249
 250     ret = 1;
 251  err:
 252     if (!ret)
 253         TSerr(TS_F_TS_CHECK_SIGNING_CERTS,
 254               TS_R_ESS_SIGNING_CERTIFICATE_ERROR);
 255     ESS_SIGNING_CERT_free(ss);
 256     ESS_SIGNING_CERT_V2_free(ssv2);
 257     return ret;
 258 }
 259
 260 /*-
 261  * Verifies whether 'response' contains a valid response with regards
 262  * to the settings of the context:
 263  *      - Gives an error message if the TS_TST_INFO is not present.
 264  *      - Calls _TS_RESP_verify_token to verify the token content.
 265  */
 266 int TS_RESP_verify_response(TS_VERIFY_CTX *ctx, TS_RESP *response)
 267 {
 268     PKCS7 *token = response->token;
 269     TS_TST_INFO *tst_info = response->tst_info;
 270     int ret = 0;
 271
 272     if (!ts_check_status_info(response))
 273         goto err;
 274     if (!int_ts_RESP_verify_token(ctx, token, tst_info))
 275         goto err;
 276     ret = 1;
 277
 278  err:
 279     return ret;
 280 }
 281
 282 /*
 283  * Tries to extract a TS_TST_INFO structure from the PKCS7 token and
 284  * calls the internal int_TS_RESP_verify_token function for verifying it.
 285  */
 286 int TS_RESP_verify_token(TS_VERIFY_CTX *ctx, PKCS7 *token)
 287 {
 288     TS_TST_INFO *tst_info = PKCS7_to_TS_TST_INFO(token);
 289     int ret = 0;
 290     if (tst_info) {
 291         ret = int_ts_RESP_verify_token(ctx, token, tst_info);
 292         TS_TST_INFO_free(tst_info);
 293     }
 294     return ret;
 295 }
 296
 297 /*-
 298  * Verifies whether the 'token' contains a valid time stamp token
 299  * with regards to the settings of the context. Only those checks are
 300  * carried out that are specified in the context:
 301  *      - Verifies the signature of the TS_TST_INFO.
 302  *      - Checks the version number of the response.
 303  *      - Check if the requested and returned policies math.
 304  *      - Check if the message imprints are the same.
 305  *      - Check if the nonces are the same.
 306  *      - Check if the TSA name matches the signer.
 307  *      - Check if the TSA name is the expected TSA.
 308  */
 309 static int int_ts_RESP_verify_token(TS_VERIFY_CTX *ctx,
 310                                     PKCS7 *token, TS_TST_INFO *tst_info)
 311 {
 312     X509 *signer = NULL;
 313     GENERAL_NAME *tsa_name = tst_info->tsa;
 314     X509_ALGOR *md_alg = NULL;
 315     unsigned char *imprint = NULL;
 316     unsigned imprint_len = 0;
 317     int ret = 0;
 318     int flags = ctx->flags;
 319
 320     /* Some options require us to also check the signature */
 321     if (((flags & TS_VFY_SIGNER) && tsa_name != NULL)
 322             || (flags & TS_VFY_TSA_NAME)) {
 323         flags |= TS_VFY_SIGNATURE;
 324     }
 325
 326     if ((flags & TS_VFY_SIGNATURE)
 327         && !TS_RESP_verify_signature(token, ctx->certs, ctx->store, &signer))
 328         goto err;
 329     if ((flags & TS_VFY_VERSION)
 330         && TS_TST_INFO_get_version(tst_info) != 1) {
 331         TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_UNSUPPORTED_VERSION);
 332         goto err;
 333     }
 334     if ((flags & TS_VFY_POLICY)
 335         && !ts_check_policy(ctx->policy, tst_info))
 336         goto err;
 337     if ((flags & TS_VFY_IMPRINT)
 338         && !ts_check_imprints(ctx->md_alg, ctx->imprint, ctx->imprint_len,
 339                               tst_info))
 340         goto err;
 341     if ((flags & TS_VFY_DATA)
 342         && (!ts_compute_imprint(ctx->data, tst_info,
 343                                 &md_alg, &imprint, &imprint_len)
 344             || !ts_check_imprints(md_alg, imprint, imprint_len, tst_info)))
 345         goto err;
 346     if ((flags & TS_VFY_NONCE)
 347         && !ts_check_nonces(ctx->nonce, tst_info))
 348         goto err;
 349     if ((flags & TS_VFY_SIGNER)
 350         && tsa_name && !ts_check_signer_name(tsa_name, signer)) {
 351         TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_TSA_NAME_MISMATCH);
 352         goto err;
 353     }
 354     if ((flags & TS_VFY_TSA_NAME)
 355         && !ts_check_signer_name(ctx->tsa_name, signer)) {
 356         TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_TSA_UNTRUSTED);
 357         goto err;
 358     }
 359     ret = 1;
 360
 361  err:
 362     X509_free(signer);
 363     X509_ALGOR_free(md_alg);
 364     OPENSSL_free(imprint);
 365     return ret;
 366 }
 367
 368 static int ts_check_status_info(TS_RESP *response)
 369 {
 370     TS_STATUS_INFO *info = response->status_info;
 371     long status = ASN1_INTEGER_get(info->status);
 372     const char *status_text = NULL;
 373     char *embedded_status_text = NULL;
 374     char failure_text[TS_STATUS_BUF_SIZE] = "";
 375
 376     if (status == 0 || status == 1)
 377         return 1;
 378
 379     /* There was an error, get the description in status_text. */
 380     if (0 <= status && status < (long) OSSL_NELEM(ts_status_text))
 381         status_text = ts_status_text[status];
 382     else
 383         status_text = "unknown code";
 384
 385     if (sk_ASN1_UTF8STRING_num(info->text) > 0
 386         && (embedded_status_text = ts_get_status_text(info->text)) == NULL)
 387         return 0;
 388
 389     /* Fill in failure_text with the failure information. */
 390     if (info->failure_info) {
 391         int i;
 392         int first = 1;
 393         for (i = 0; i < (int)OSSL_NELEM(ts_failure_info); ++i) {
 394             if (ASN1_BIT_STRING_get_bit(info->failure_info,
 395                                         ts_failure_info[i].code)) {
 396                 if (!first)
 397                     strcat(failure_text, ",");
 398                 else
 399                     first = 0;
 400                 strcat(failure_text, ts_failure_info[i].text);
 401             }
 402         }
 403     }
 404     if (failure_text[0] == '\0')
 405         strcpy(failure_text, "unspecified");
 406
 407     TSerr(TS_F_TS_CHECK_STATUS_INFO, TS_R_NO_TIME_STAMP_TOKEN);
 408     ERR_add_error_data(6,
 409                        "status code: ", status_text,
 410                        ", status text: ", embedded_status_text ?
 411                        embedded_status_text : "unspecified",
 412                        ", failure codes: ", failure_text);
 413     OPENSSL_free(embedded_status_text);
 414
 415     return 0;
 416 }
 417
 418 static char *ts_get_status_text(STACK_OF(ASN1_UTF8STRING) *text)
 419 {
 420     return sk_ASN1_UTF8STRING2text(text, "/", TS_MAX_STATUS_LENGTH);
 421 }
 422
 423 static int ts_check_policy(const ASN1_OBJECT *req_oid,
 424                            const TS_TST_INFO *tst_info)
 425 {
 426     const ASN1_OBJECT *resp_oid = tst_info->policy_id;
 427
 428     if (OBJ_cmp(req_oid, resp_oid) != 0) {
 429         TSerr(TS_F_TS_CHECK_POLICY, TS_R_POLICY_MISMATCH);
 430         return 0;
 431     }
 432
 433     return 1;
 434 }
 435
 436 static int ts_compute_imprint(BIO *data, TS_TST_INFO *tst_info,
 437                               X509_ALGOR **md_alg,
 438                               unsigned char **imprint, unsigned *imprint_len)
 439 {
 440     TS_MSG_IMPRINT *msg_imprint = tst_info->msg_imprint;
 441     X509_ALGOR *md_alg_resp = msg_imprint->hash_algo;
 442     const EVP_MD *md;
 443     EVP_MD_CTX *md_ctx = NULL;
 444     unsigned char buffer[4096];
 445     int length;
 446
 447     *md_alg = NULL;
 448     *imprint = NULL;
 449
 450     if ((*md_alg = X509_ALGOR_dup(md_alg_resp)) == NULL)
 451         goto err;
 452     if ((md = EVP_get_digestbyobj((*md_alg)->algorithm)) == NULL) {
 453         TSerr(TS_F_TS_COMPUTE_IMPRINT, TS_R_UNSUPPORTED_MD_ALGORITHM);
 454         goto err;
 455     }
 456     length = EVP_MD_size(md);
 457     if (length < 0)
 458         goto err;
 459     *imprint_len = length;
 460     if ((*imprint = OPENSSL_malloc(*imprint_len)) == NULL) {
 461         TSerr(TS_F_TS_COMPUTE_IMPRINT, ERR_R_MALLOC_FAILURE);
 462         goto err;
 463     }
 464
 465     md_ctx = EVP_MD_CTX_new();
 466     if (md_ctx == NULL) {
 467         TSerr(TS_F_TS_COMPUTE_IMPRINT, ERR_R_MALLOC_FAILURE);
 468         goto err;
 469     }
 470     if (!EVP_DigestInit(md_ctx, md))
 471         goto err;
 472     while ((length = BIO_read(data, buffer, sizeof(buffer))) > 0) {
 473         if (!EVP_DigestUpdate(md_ctx, buffer, length))
 474             goto err;
 475     }
 476     if (!EVP_DigestFinal(md_ctx, *imprint, NULL))
 477         goto err;
 478     EVP_MD_CTX_free(md_ctx);
 479
 480     return 1;
 481  err:
 482     EVP_MD_CTX_free(md_ctx);
 483     X509_ALGOR_free(*md_alg);
 484     OPENSSL_free(*imprint);
 485     *imprint_len = 0;
 486     *imprint = 0;
 487     return 0;
 488 }
 489
 490 static int ts_check_imprints(X509_ALGOR *algor_a,
 491                              const unsigned char *imprint_a, unsigned len_a,
 492                              TS_TST_INFO *tst_info)
 493 {
 494     TS_MSG_IMPRINT *b = tst_info->msg_imprint;
 495     X509_ALGOR *algor_b = b->hash_algo;
 496     int ret = 0;
 497
 498     if (algor_a) {
 499         if (OBJ_cmp(algor_a->algorithm, algor_b->algorithm))
 500             goto err;
 501
 502         /* The parameter must be NULL in both. */
 503         if ((algor_a->parameter
 504              && ASN1_TYPE_get(algor_a->parameter) != V_ASN1_NULL)
 505             || (algor_b->parameter
 506                 && ASN1_TYPE_get(algor_b->parameter) != V_ASN1_NULL))
 507             goto err;
 508     }
 509
 510     ret = len_a == (unsigned)ASN1_STRING_length(b->hashed_msg) &&
 511         memcmp(imprint_a, ASN1_STRING_get0_data(b->hashed_msg), len_a) == 0;
 512  err:
 513     if (!ret)
 514         TSerr(TS_F_TS_CHECK_IMPRINTS, TS_R_MESSAGE_IMPRINT_MISMATCH);
 515     return ret;
 516 }
 517
 518 static int ts_check_nonces(const ASN1_INTEGER *a, TS_TST_INFO *tst_info)
 519 {
 520     const ASN1_INTEGER *b = tst_info->nonce;
 521
 522     if (!b) {
 523         TSerr(TS_F_TS_CHECK_NONCES, TS_R_NONCE_NOT_RETURNED);
 524         return 0;
 525     }
 526
 527     /* No error if a nonce is returned without being requested. */
 528     if (ASN1_INTEGER_cmp(a, b) != 0) {
 529         TSerr(TS_F_TS_CHECK_NONCES, TS_R_NONCE_MISMATCH);
 530         return 0;
 531     }
 532
 533     return 1;
 534 }
 535
 536 /*
 537  * Check if the specified TSA name matches either the subject or one of the
 538  * subject alternative names of the TSA certificate.
 539  */
 540 static int ts_check_signer_name(GENERAL_NAME *tsa_name, X509 *signer)
 541 {
 542     STACK_OF(GENERAL_NAME) *gen_names = NULL;
 543     int idx = -1;
 544     int found = 0;
 545
 546     if (tsa_name->type == GEN_DIRNAME
 547         && X509_name_cmp(tsa_name->d.dirn, X509_get_subject_name(signer)) == 0)
 548         return 1;
 549     gen_names = X509_get_ext_d2i(signer, NID_subject_alt_name, NULL, &idx);
 550     while (gen_names != NULL) {
 551         found = ts_find_name(gen_names, tsa_name) >= 0;
 552         if (found)
 553             break;
 554         /*
 555          * Get the next subject alternative name, although there should be no
 556          * more than one.
 557          */
 558         GENERAL_NAMES_free(gen_names);
 559         gen_names = X509_get_ext_d2i(signer, NID_subject_alt_name, NULL, &idx);
 560     }
 561     GENERAL_NAMES_free(gen_names);
 562
 563     return found;
 564 }
 565
 566 /* Returns 1 if name is in gen_names, 0 otherwise. */
 567 static int ts_find_name(STACK_OF(GENERAL_NAME) *gen_names, GENERAL_NAME *name)
 568 {
 569     int i, found;
 570     for (i = 0, found = 0; !found && i < sk_GENERAL_NAME_num(gen_names); ++i) {
 571         GENERAL_NAME *current = sk_GENERAL_NAME_value(gen_names, i);
 572         found = GENERAL_NAME_cmp(current, name) == 0;
 573     }
 574     return found ? i - 1 : -1;
 575 }