crypto/ocsp/ocsp_vfy.c

   1 /*
   2  * Copyright 2001-2021 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 #include <string.h>
  11 #include <openssl/ocsp.h>
  12 #include <openssl/err.h>
  13 #include "internal/sizes.h"
  14 #include "ocsp_local.h"
  15
  16 static int ocsp_find_signer(X509 **psigner, OCSP_BASICRESP *bs,
  17                             STACK_OF(X509) *certs, unsigned long flags);
  18 static X509 *ocsp_find_signer_sk(STACK_OF(X509) *certs, OCSP_RESPID *id);
  19 static int ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain);
  20 static int ocsp_check_ids(STACK_OF(OCSP_SINGLERESP) *sresp,
  21                           OCSP_CERTID **ret);
  22 static int ocsp_match_issuerid(X509 *cert, OCSP_CERTID *cid,
  23                                STACK_OF(OCSP_SINGLERESP) *sresp);
  24 static int ocsp_check_delegated(X509 *x);
  25 static int ocsp_req_find_signer(X509 **psigner, OCSP_REQUEST *req,
  26                                 const X509_NAME *nm, STACK_OF(X509) *certs,
  27                                 unsigned long flags);
  28
  29 /* Returns 1 on success, 0 on failure, or -1 on fatal error */
  30 static int ocsp_verify_signer(X509 *signer, int response,
  31                               X509_STORE *st, unsigned long flags,
  32                               STACK_OF(X509) *untrusted, STACK_OF(X509) **chain)
  33 {
  34     X509_STORE_CTX *ctx = X509_STORE_CTX_new();
  35     X509_VERIFY_PARAM *vp;
  36     int ret = -1;
  37
  38     if (ctx == NULL) {
  39         ERR_raise(ERR_LIB_OCSP, ERR_R_MALLOC_FAILURE);
  40         goto end;
  41     }
  42     if (!X509_STORE_CTX_init(ctx, st, signer, untrusted)) {
  43         ERR_raise(ERR_LIB_OCSP, ERR_R_X509_LIB);
  44         goto end;
  45     }
  46     if ((vp = X509_STORE_CTX_get0_param(ctx)) == NULL)
  47         goto end;
  48     if ((flags & OCSP_PARTIAL_CHAIN) != 0)
  49         X509_VERIFY_PARAM_set_flags(vp, X509_V_FLAG_PARTIAL_CHAIN);
  50     if (response
  51             && X509_get_ext_by_NID(signer, NID_id_pkix_OCSP_noCheck, -1) >= 0)
  52         /*
  53          * Locally disable revocation status checking for OCSP responder cert.
  54          * Done here for CRLs; TODO should be done also for OCSP-based checks.
  55          */
  56         X509_VERIFY_PARAM_clear_flags(vp, X509_V_FLAG_CRL_CHECK);
  57     X509_STORE_CTX_set_purpose(ctx, X509_PURPOSE_OCSP_HELPER);
  58     X509_STORE_CTX_set_trust(ctx, X509_TRUST_OCSP_REQUEST);
  59     /* TODO: why is X509_TRUST_OCSP_REQUEST set? Seems to get ignored. */
  60
  61     ret = X509_verify_cert(ctx);
  62     if (ret <= 0) {
  63         ret = X509_STORE_CTX_get_error(ctx);
  64         ERR_raise_data(ERR_LIB_OCSP, OCSP_R_CERTIFICATE_VERIFY_ERROR,
  65                        "Verify error: %s", X509_verify_cert_error_string(ret));
  66         goto end;
  67     }
  68     if (chain != NULL)
  69         *chain = X509_STORE_CTX_get1_chain(ctx);
  70
  71  end:
  72     X509_STORE_CTX_free(ctx);
  73     return ret;
  74 }
  75
  76 static int ocsp_verify(OCSP_REQUEST *req, OCSP_BASICRESP *bs,
  77                        X509 *signer, unsigned long flags)
  78 {
  79     EVP_PKEY *skey;
  80     int ret = 1;
  81
  82     if ((flags & OCSP_NOSIGS) == 0) {
  83         if ((skey = X509_get0_pubkey(signer)) == NULL) {
  84             ERR_raise(ERR_LIB_OCSP, OCSP_R_NO_SIGNER_KEY);
  85             return -1;
  86         }
  87         if (req != NULL)
  88             ret = OCSP_REQUEST_verify(req, skey, signer->libctx, signer->propq);
  89         else
  90             ret = OCSP_BASICRESP_verify(bs, skey, signer->libctx, signer->propq);
  91         if (ret <= 0)
  92             ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNATURE_FAILURE);
  93     }
  94     return ret;
  95 }
  96
  97 /* Verify a basic response message */
  98 int OCSP_basic_verify(OCSP_BASICRESP *bs, STACK_OF(X509) *certs,
  99                       X509_STORE *st, unsigned long flags)
 100 {
 101     X509 *signer, *x;
 102     STACK_OF(X509) *chain = NULL;
 103     STACK_OF(X509) *untrusted = NULL;
 104     int ret = ocsp_find_signer(&signer, bs, certs, flags);
 105
 106     if (ret == 0) {
 107         ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);
 108         goto end;
 109     }
 110     if ((ret == 2) && (flags & OCSP_TRUSTOTHER) != 0)
 111         flags |= OCSP_NOVERIFY;
 112
 113     if ((ret = ocsp_verify(NULL, bs, signer, flags)) <= 0)
 114         goto end;
 115     if ((flags & OCSP_NOVERIFY) == 0) {
 116         ret = -1;
 117         if ((flags & OCSP_NOCHAIN) == 0) {
 118             if ((untrusted = sk_X509_dup(bs->certs)) == NULL)
 119                 goto end;
 120             if (!X509_add_certs(untrusted, certs, X509_ADD_FLAG_DEFAULT))
 121                 goto end;
 122         }
 123         ret = ocsp_verify_signer(signer, 1, st, flags, untrusted, &chain);
 124         if (ret <= 0)
 125             goto end;
 126         if ((flags & OCSP_NOCHECKS) != 0) {
 127             ret = 1;
 128             goto end;
 129         }
 130         /*
 131          * At this point we have a valid certificate chain need to verify it
 132          * against the OCSP issuer criteria.
 133          */
 134         ret = ocsp_check_issuer(bs, chain);
 135
 136         /* If fatal error or valid match then finish */
 137         if (ret != 0)
 138             goto end;
 139
 140         /*
 141          * Easy case: explicitly trusted. Get root CA and check for explicit
 142          * trust
 143          */
 144         if ((flags & OCSP_NOEXPLICIT) != 0)
 145             goto end;
 146
 147         x = sk_X509_value(chain, sk_X509_num(chain) - 1);
 148         if (X509_check_trust(x, NID_OCSP_sign, 0) != X509_TRUST_TRUSTED) {
 149             ERR_raise(ERR_LIB_OCSP, OCSP_R_ROOT_CA_NOT_TRUSTED);
 150             ret = 0;
 151             goto end;
 152         }
 153         ret = 1;
 154     }
 155
 156  end:
 157     sk_X509_pop_free(chain, X509_free);
 158     sk_X509_free(untrusted);
 159     return ret;
 160 }
 161
 162 int OCSP_resp_get0_signer(OCSP_BASICRESP *bs, X509 **signer,
 163                           STACK_OF(X509) *extra_certs)
 164 {
 165     return ocsp_find_signer(signer, bs, extra_certs, 0) > 0;
 166 }
 167
 168 static int ocsp_find_signer(X509 **psigner, OCSP_BASICRESP *bs,
 169                             STACK_OF(X509) *certs, unsigned long flags)
 170 {
 171     X509 *signer;
 172     OCSP_RESPID *rid = &bs->tbsResponseData.responderId;
 173
 174     if ((signer = ocsp_find_signer_sk(certs, rid)) != NULL) {
 175         *psigner = signer;
 176         return 2;
 177     }
 178     if ((flags & OCSP_NOINTERN) == 0 &&
 179         (signer = ocsp_find_signer_sk(bs->certs, rid))) {
 180         *psigner = signer;
 181         return 1;
 182     }
 183     /* Maybe lookup from store if by subject name */
 184
 185     *psigner = NULL;
 186     return 0;
 187 }
 188
 189 static X509 *ocsp_find_signer_sk(STACK_OF(X509) *certs, OCSP_RESPID *id)
 190 {
 191     int i, r;
 192     unsigned char tmphash[SHA_DIGEST_LENGTH], *keyhash;
 193     EVP_MD *md;
 194     X509 *x;
 195
 196     /* Easy if lookup by name */
 197     if (id->type == V_OCSP_RESPID_NAME)
 198         return X509_find_by_subject(certs, id->value.byName);
 199
 200     /* Lookup by key hash */
 201
 202     /* If key hash isn't SHA1 length then forget it */
 203     if (id->value.byKey->length != SHA_DIGEST_LENGTH)
 204         return NULL;
 205     keyhash = id->value.byKey->data;
 206     /* Calculate hash of each key and compare */
 207     for (i = 0; i < sk_X509_num(certs); i++) {
 208         if ((x = sk_X509_value(certs, i)) != NULL) {
 209             if ((md = EVP_MD_fetch(x->libctx, SN_sha1, x->propq)) == NULL)
 210                 break;
 211             r = X509_pubkey_digest(x, md, tmphash, NULL);
 212             EVP_MD_free(md);
 213             if (!r)
 214                 break;
 215             if (memcmp(keyhash, tmphash, SHA_DIGEST_LENGTH) == 0)
 216                 return x;
 217         }
 218     }
 219     return NULL;
 220 }
 221
 222 static int ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain)
 223 {
 224     STACK_OF(OCSP_SINGLERESP) *sresp = bs->tbsResponseData.responses;
 225     X509 *signer, *sca;
 226     OCSP_CERTID *caid = NULL;
 227     int ret;
 228
 229     if (sk_X509_num(chain) <= 0) {
 230         ERR_raise(ERR_LIB_OCSP, OCSP_R_NO_CERTIFICATES_IN_CHAIN);
 231         return -1;
 232     }
 233
 234     /* See if the issuer IDs match. */
 235     ret = ocsp_check_ids(sresp, &caid);
 236
 237     /* If ID mismatch or other error then return */
 238     if (ret <= 0)
 239         return ret;
 240
 241     signer = sk_X509_value(chain, 0);
 242     /* Check to see if OCSP responder CA matches request CA */
 243     if (sk_X509_num(chain) > 1) {
 244         sca = sk_X509_value(chain, 1);
 245         ret = ocsp_match_issuerid(sca, caid, sresp);
 246         if (ret < 0)
 247             return ret;
 248         if (ret != 0) {
 249             /* We have a match, if extensions OK then success */
 250             if (ocsp_check_delegated(signer))
 251                 return 1;
 252             return 0;
 253         }
 254     }
 255
 256     /* Otherwise check if OCSP request signed directly by request CA */
 257     return ocsp_match_issuerid(signer, caid, sresp);
 258 }
 259
 260 /*
 261  * Check the issuer certificate IDs for equality. If there is a mismatch with
 262  * the same algorithm then there's no point trying to match any certificates
 263  * against the issuer. If the issuer IDs all match then we just need to check
 264  * equality against one of them.
 265  */
 266
 267 static int ocsp_check_ids(STACK_OF(OCSP_SINGLERESP) *sresp, OCSP_CERTID **ret)
 268 {
 269     OCSP_CERTID *tmpid, *cid;
 270     int i, idcount;
 271
 272     idcount = sk_OCSP_SINGLERESP_num(sresp);
 273     if (idcount <= 0) {
 274         ERR_raise(ERR_LIB_OCSP, OCSP_R_RESPONSE_CONTAINS_NO_REVOCATION_DATA);
 275         return -1;
 276     }
 277
 278     cid = sk_OCSP_SINGLERESP_value(sresp, 0)->certId;
 279
 280     *ret = NULL;
 281     for (i = 1; i < idcount; i++) {
 282         tmpid = sk_OCSP_SINGLERESP_value(sresp, i)->certId;
 283         /* Check to see if IDs match */
 284         if (OCSP_id_issuer_cmp(cid, tmpid)) {
 285             /* If algorithm mismatch let caller deal with it */
 286             if (OBJ_cmp(tmpid->hashAlgorithm.algorithm,
 287                         cid->hashAlgorithm.algorithm))
 288                 return 2;
 289             /* Else mismatch */
 290             return 0;
 291         }
 292     }
 293
 294     /* All IDs match: only need to check one ID */
 295     *ret = cid;
 296     return 1;
 297 }
 298
 299 /*
 300  * Match the certificate issuer ID.
 301  * Returns -1 on fatal error, 0 if there is no match and 1 if there is a match.
 302  */
 303 static int ocsp_match_issuerid(X509 *cert, OCSP_CERTID *cid,
 304                                STACK_OF(OCSP_SINGLERESP) *sresp)
 305 {
 306     int ret = -1;
 307     EVP_MD *dgst = NULL;
 308
 309     /* If only one ID to match then do it */
 310     if (cid != NULL) {
 311         char name[OSSL_MAX_NAME_SIZE];
 312         const X509_NAME *iname;
 313         int mdlen;
 314         unsigned char md[EVP_MAX_MD_SIZE];
 315
 316         OBJ_obj2txt(name, sizeof(name), cid->hashAlgorithm.algorithm, 0);
 317
 318         (void)ERR_set_mark();
 319         dgst = EVP_MD_fetch(NULL, name, NULL);
 320         if (dgst == NULL)
 321             dgst = (EVP_MD *)EVP_get_digestbyname(name);
 322
 323         if (dgst == NULL) {
 324             (void)ERR_clear_last_mark();
 325             ERR_raise(ERR_LIB_OCSP, OCSP_R_UNKNOWN_MESSAGE_DIGEST);
 326             goto end;
 327         }
 328         (void)ERR_pop_to_mark();
 329
 330         mdlen = EVP_MD_size(dgst);
 331         if (mdlen < 0) {
 332             ERR_raise(ERR_LIB_OCSP, OCSP_R_DIGEST_SIZE_ERR);
 333             goto end;
 334         }
 335         if (cid->issuerNameHash.length != mdlen ||
 336             cid->issuerKeyHash.length != mdlen) {
 337             ret = 0;
 338             goto end;
 339         }
 340         iname = X509_get_subject_name(cert);
 341         if (!X509_NAME_digest(iname, dgst, md, NULL))
 342             goto end;
 343         if (memcmp(md, cid->issuerNameHash.data, mdlen) != 0) {
 344             ret = 0;
 345             goto end;
 346         }
 347         if (!X509_pubkey_digest(cert, dgst, md, NULL)) {
 348             ERR_raise(ERR_LIB_OCSP, OCSP_R_DIGEST_ERR);
 349             goto end;
 350         }
 351         ret = memcmp(md, cid->issuerKeyHash.data, mdlen) == 0;
 352         goto end;
 353     } else {
 354         /* We have to match the whole lot */
 355         int i;
 356         OCSP_CERTID *tmpid;
 357
 358         for (i = 0; i < sk_OCSP_SINGLERESP_num(sresp); i++) {
 359             tmpid = sk_OCSP_SINGLERESP_value(sresp, i)->certId;
 360             ret = ocsp_match_issuerid(cert, tmpid, NULL);
 361             if (ret <= 0)
 362                 return ret;
 363         }
 364     }
 365     return 1;
 366 end:
 367     EVP_MD_free(dgst);
 368     return ret;
 369 }
 370
 371 static int ocsp_check_delegated(X509 *x)
 372 {
 373     if ((X509_get_extension_flags(x) & EXFLAG_XKUSAGE)
 374         && (X509_get_extended_key_usage(x) & XKU_OCSP_SIGN))
 375         return 1;
 376     ERR_raise(ERR_LIB_OCSP, OCSP_R_MISSING_OCSPSIGNING_USAGE);
 377     return 0;
 378 }
 379
 380 /*
 381  * Verify an OCSP request. This is much easier than OCSP response verify.
 382  * Just find the signer's certificate and verify it against a given trust value.
 383  * Returns 1 on success, 0 on failure and on fatal error.
 384  */
 385 int OCSP_request_verify(OCSP_REQUEST *req, STACK_OF(X509) *certs,
 386                         X509_STORE *store, unsigned long flags)
 387 {
 388     X509 *signer;
 389     const X509_NAME *nm;
 390     GENERAL_NAME *gen;
 391     int ret;
 392
 393     if (!req->optionalSignature) {
 394         ERR_raise(ERR_LIB_OCSP, OCSP_R_REQUEST_NOT_SIGNED);
 395         return 0;
 396     }
 397     gen = req->tbsRequest.requestorName;
 398     if (!gen || gen->type != GEN_DIRNAME) {
 399         ERR_raise(ERR_LIB_OCSP, OCSP_R_UNSUPPORTED_REQUESTORNAME_TYPE);
 400         return 0; /* not returning -1 here for backward compatibility*/
 401     }
 402     nm = gen->d.directoryName;
 403     ret = ocsp_req_find_signer(&signer, req, nm, certs, flags);
 404     if (ret <= 0) {
 405         ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);
 406         return 0; /* not returning -1 here for backward compatibility*/
 407     }
 408     if ((ret == 2) && (flags & OCSP_TRUSTOTHER) != 0)
 409         flags |= OCSP_NOVERIFY;
 410
 411     if ((ret = ocsp_verify(req, NULL, signer, flags)) <= 0)
 412         return 0; /* not returning 'ret' here for backward compatibility*/
 413     if ((flags & OCSP_NOVERIFY) != 0)
 414         return 1;
 415     return ocsp_verify_signer(signer, 0, store, flags,
 416                               (flags & OCSP_NOCHAIN) != 0 ?
 417                               NULL : req->optionalSignature->certs, NULL) > 0;
 418     /* using '> 0' here to avoid breaking backward compatibility returning -1 */
 419 }
 420
 421 static int ocsp_req_find_signer(X509 **psigner, OCSP_REQUEST *req,
 422                                 const X509_NAME *nm, STACK_OF(X509) *certs,
 423                                 unsigned long flags)
 424 {
 425     X509 *signer;
 426
 427     if ((flags & OCSP_NOINTERN) == 0) {
 428         signer = X509_find_by_subject(req->optionalSignature->certs, nm);
 429         if (signer != NULL) {
 430             *psigner = signer;
 431             return 1;
 432         }
 433     }
 434
 435     if ((signer = X509_find_by_subject(certs, nm)) != NULL) {
 436         *psigner = signer;
 437         return 2;
 438     }
 439     return 0;
 440 }