lib/libtls/tls_ocsp.c

   1 /*
   2  * Copyright (c) 2015 Marko Kreen <markokr@gmail.com>
   3  * Copyright (c) 2016 Bob Beck <beck@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #include <sys/types.h>
  19
  20 #include <arpa/inet.h>
  21 #include <netinet/in.h>
  22
  23 #include <openssl/err.h>
  24 #include <openssl/ocsp.h>
  25 #include <openssl/x509.h>
  26
  27 #include <tls.h>
  28 #include "tls_internal.h"
  29
  30 #define MAXAGE_SEC (14*24*60*60)
  31 #define JITTER_SEC (60)
  32
  33 /*
  34  * State for request.
  35  */
  36
  37 static struct tls_ocsp *
  38 tls_ocsp_new(void)
  39 {
  40         return (calloc(1, sizeof(struct tls_ocsp)));
  41 }
  42
  43 void
  44 tls_ocsp_free(struct tls_ocsp *ocsp)
  45 {
  46         if (ocsp == NULL)
  47                 return;
  48
  49         free(ocsp->ocsp_result);
  50         ocsp->ocsp_result = NULL;
  51         free(ocsp->ocsp_url);
  52         ocsp->ocsp_url = NULL;
  53         free(ocsp);
  54 }
  55
  56 static int
  57 tls_ocsp_asn1_parse_time(struct tls *ctx, ASN1_GENERALIZEDTIME *gt, time_t *gt_time)
  58 {
  59         struct tm tm;
  60
  61         if (gt == NULL)
  62                 return -1;
  63         /* RFC 6960 specifies that all times in OCSP must be GENERALIZEDTIME */
  64         if (ASN1_time_parse(gt->data, gt->length, &tm,
  65                 V_ASN1_GENERALIZEDTIME) == -1)
  66                 return -1;
  67         if ((*gt_time = timegm(&tm)) == -1)
  68                 return -1;
  69         return 0;
  70 }
  71
  72 static int
  73 tls_ocsp_fill_info(struct tls *ctx, int response_status, int cert_status,
  74     int crl_reason, ASN1_GENERALIZEDTIME *revtime,
  75     ASN1_GENERALIZEDTIME *thisupd, ASN1_GENERALIZEDTIME *nextupd)
  76 {
  77         struct tls_ocsp_result *info = NULL;
  78
  79         free(ctx->ocsp->ocsp_result);
  80         ctx->ocsp->ocsp_result = NULL;
  81
  82         if ((info = calloc(1, sizeof (struct tls_ocsp_result))) == NULL) {
  83                 tls_set_error(ctx, "calloc");
  84                 return -1;
  85         }
  86         info->response_status = response_status;
  87         info->cert_status = cert_status;
  88         info->crl_reason = crl_reason;
  89         if (info->response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
  90                 info->result_msg =
  91                     OCSP_response_status_str(info->response_status);
  92         } else if (info->cert_status != V_OCSP_CERTSTATUS_REVOKED) {
  93                 info->result_msg = OCSP_cert_status_str(info->cert_status);
  94         } else {
  95                 info->result_msg = OCSP_crl_reason_str(info->crl_reason);
  96         }
  97         info->revocation_time = info->this_update = info->next_update = -1;
  98         if (revtime != NULL &&
  99             tls_ocsp_asn1_parse_time(ctx, revtime, &info->revocation_time) != 0) {
 100                 tls_set_error(ctx,
 101                     "unable to parse revocation time in OCSP reply");
 102                 goto error;
 103         }
 104         if (thisupd != NULL &&
 105             tls_ocsp_asn1_parse_time(ctx, thisupd, &info->this_update) != 0) {
 106                 tls_set_error(ctx,
 107                     "unable to parse this update time in OCSP reply");
 108                 goto error;
 109         }
 110         if (nextupd != NULL &&
 111             tls_ocsp_asn1_parse_time(ctx, nextupd, &info->next_update) != 0) {
 112                 tls_set_error(ctx,
 113                     "unable to parse next update time in OCSP reply");
 114                 goto error;
 115         }
 116         ctx->ocsp->ocsp_result = info;
 117         return 0;
 118  error:
 119         free(info);
 120         return -1;
 121 }
 122
 123 static OCSP_CERTID *
 124 tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
 125     SSL_CTX *ssl_ctx)
 126 {
 127         X509_NAME *issuer_name;
 128         X509 *issuer;
 129         X509_STORE_CTX storectx;
 130         X509_OBJECT tmpobj;
 131         OCSP_CERTID *cid = NULL;
 132         X509_STORE *store;
 133
 134         if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
 135                 return NULL;
 136
 137         if (extra_certs != NULL) {
 138                 issuer = X509_find_by_subject(extra_certs, issuer_name);
 139                 if (issuer != NULL)
 140                         return OCSP_cert_to_id(NULL, main_cert, issuer);
 141         }
 142
 143         if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
 144                 return NULL;
 145         if (X509_STORE_CTX_init(&storectx, store, main_cert, extra_certs) != 1)
 146                 return NULL;
 147         if (X509_STORE_get_by_subject(&storectx, X509_LU_X509, issuer_name,
 148                 &tmpobj) == 1) {
 149                 cid = OCSP_cert_to_id(NULL, main_cert, tmpobj.data.x509);
 150                 X509_OBJECT_free_contents(&tmpobj);
 151         }
 152         X509_STORE_CTX_cleanup(&storectx);
 153         return cid;
 154 }
 155
 156 struct tls_ocsp *
 157 tls_ocsp_setup_from_peer(struct tls *ctx)
 158 {
 159         struct tls_ocsp *ocsp = NULL;
 160         STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
 161
 162         if ((ocsp = tls_ocsp_new()) == NULL)
 163                 goto failed;
 164
 165         /* steal state from ctx struct */
 166         ocsp->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
 167         ocsp->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
 168         if (ocsp->main_cert == NULL) {
 169                 tls_set_errorx(ctx, "no peer certificate for OCSP");
 170                 goto failed;
 171         }
 172
 173         ocsp_urls = X509_get1_ocsp(ocsp->main_cert);
 174         if (ocsp_urls == NULL)
 175                 goto failed;
 176         ocsp->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
 177         if (ocsp->ocsp_url == NULL) {
 178                 tls_set_errorx(ctx, "out of memory");
 179                 goto failed;
 180         }
 181
 182         X509_email_free(ocsp_urls);
 183         return ocsp;
 184
 185  failed:
 186         tls_ocsp_free(ocsp);
 187         X509_email_free(ocsp_urls);
 188         return NULL;
 189 }
 190
 191 static int
 192 tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
 193 {
 194         OCSP_BASICRESP *br = NULL;
 195         ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
 196         OCSP_CERTID *cid = NULL;
 197         STACK_OF(X509) *combined = NULL;
 198         int response_status=0, cert_status=0, crl_reason=0;
 199         int ret = -1;
 200         unsigned long flags;
 201
 202         if ((br = OCSP_response_get1_basic(resp)) == NULL) {
 203                 tls_set_errorx(ctx, "cannot load ocsp reply");
 204                 goto error;
 205         }
 206
 207         /*
 208          * Skip validation of 'extra_certs' as this should be done
 209          * already as part of main handshake.
 210          */
 211         flags = OCSP_TRUSTOTHER;
 212
 213         /* now verify */
 214         if (OCSP_basic_verify(br, ctx->ocsp->extra_certs,
 215                 SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
 216                 tls_set_error(ctx, "ocsp verify failed");
 217                 goto error;
 218         }
 219
 220         /* signature OK, look inside */
 221         response_status = OCSP_response_status(resp);
 222         if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
 223                 tls_set_errorx(ctx, "ocsp verify failed: response - %s",
 224                     OCSP_response_status_str(response_status));
 225                 goto error;
 226         }
 227
 228         cid = tls_ocsp_get_certid(ctx->ocsp->main_cert,
 229             ctx->ocsp->extra_certs, ctx->ssl_ctx);
 230         if (cid == NULL) {
 231                 tls_set_errorx(ctx, "ocsp verify failed: no issuer cert");
 232                 goto error;
 233         }
 234
 235         if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
 236             &revtime, &thisupd, &nextupd) != 1) {
 237                 tls_set_errorx(ctx, "ocsp verify failed: no result for cert");
 238                 goto error;
 239         }
 240
 241         if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
 242             MAXAGE_SEC) != 1) {
 243                 tls_set_errorx(ctx,
 244                     "ocsp verify failed: ocsp response not current");
 245                 goto error;
 246         }
 247
 248         if (tls_ocsp_fill_info(ctx, response_status, cert_status,
 249             crl_reason, revtime, thisupd, nextupd) != 0)
 250                 goto error;
 251
 252         /* finally can look at status */
 253         if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
 254             V_OCSP_CERTSTATUS_UNKNOWN) {
 255                 tls_set_errorx(ctx, "ocsp verify failed: revoked cert - %s",
 256                                OCSP_crl_reason_str(crl_reason));
 257                 goto error;
 258         }
 259         ret = 0;
 260
 261  error:
 262         sk_X509_free(combined);
 263         OCSP_CERTID_free(cid);
 264         OCSP_BASICRESP_free(br);
 265         return ret;
 266 }
 267
 268 /*
 269  * Process a raw OCSP response from an OCSP server request.
 270  * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
 271  * returns 0 if certificate ok, -1 otherwise.
 272  */
 273 static int
 274 tls_ocsp_process_response_internal(struct tls *ctx, const unsigned char *response,
 275     size_t size)
 276 {
 277         int ret;
 278         OCSP_RESPONSE *resp;
 279
 280         resp = d2i_OCSP_RESPONSE(NULL, &response, size);
 281         if (resp == NULL) {
 282                 tls_ocsp_free(ctx->ocsp);
 283                 ctx->ocsp = NULL;
 284                 tls_set_error(ctx, "unable to parse OCSP response");
 285                 return -1;
 286         }
 287         ret = tls_ocsp_verify_response(ctx, resp);
 288         OCSP_RESPONSE_free(resp);
 289         return ret;
 290 }
 291
 292 /* TLS handshake verification callback for stapled requests */
 293 int
 294 tls_ocsp_verify_cb(SSL *ssl, void *arg)
 295 {
 296         const unsigned char *raw = NULL;
 297         int size, res = -1;
 298         struct tls *ctx;
 299
 300         if ((ctx = SSL_get_app_data(ssl)) == NULL)
 301                 return -1;
 302
 303         size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
 304         if (size <= 0) {
 305                 if (ctx->config->ocsp_require_stapling) {
 306                         tls_set_errorx(ctx, "no stapled OCSP response provided");
 307                         return 0;
 308                 }
 309                 return 1;
 310         }
 311
 312         tls_ocsp_free(ctx->ocsp);
 313         ctx->ocsp = tls_ocsp_setup_from_peer(ctx);
 314         if (ctx->ocsp != NULL) {
 315                 if (ctx->config->verify_cert == 0 || ctx->config->verify_time == 0)
 316                         return 1;
 317                 res = tls_ocsp_process_response_internal(ctx, raw, size);
 318         }
 319
 320         return (res == 0) ? 1 : 0;
 321 }
 322
 323
 324 /* Staple the OCSP information in ctx->ocsp to the server handshake. */
 325 int
 326 tls_ocsp_stapling_cb(SSL *ssl, void *arg)
 327 {
 328         struct tls *ctx;
 329         unsigned char *ocsp_staple = NULL;
 330         int ret = SSL_TLSEXT_ERR_ALERT_FATAL;
 331
 332         if ((ctx = SSL_get_app_data(ssl)) == NULL)
 333                 goto err;
 334
 335         if (ctx->config->keypair == NULL ||
 336             ctx->config->keypair->ocsp_staple == NULL ||
 337             ctx->config->keypair->ocsp_staple_len == 0)
 338                 return SSL_TLSEXT_ERR_NOACK;
 339
 340         if ((ocsp_staple = malloc(ctx->config->keypair->ocsp_staple_len)) ==
 341             NULL)
 342                 goto err;
 343
 344         memcpy(ocsp_staple, ctx->config->keypair->ocsp_staple,
 345             ctx->config->keypair->ocsp_staple_len);
 346         if (SSL_set_tlsext_status_ocsp_resp(ctx->ssl_conn, ocsp_staple,
 347                 ctx->config->keypair->ocsp_staple_len) != 1)
 348                 goto err;
 349
 350         ret = SSL_TLSEXT_ERR_OK;
 351  err:
 352         if (ret != SSL_TLSEXT_ERR_OK)
 353                 free(ocsp_staple);
 354         return ret;
 355 }
 356
 357 /*
 358  * Public API
 359  */
 360
 361 /* Retrieve OCSP URL from peer certificate, if present */
 362 const char *
 363 tls_peer_ocsp_url(struct tls *ctx)
 364 {
 365         if (ctx->ocsp == NULL)
 366                 return NULL;
 367         return ctx->ocsp->ocsp_url;
 368 }
 369
 370 const char *
 371 tls_peer_ocsp_result(struct tls *ctx)
 372 {
 373         if (ctx->ocsp == NULL)
 374                 return NULL;
 375         if (ctx->ocsp->ocsp_result == NULL)
 376                 return NULL;
 377         return ctx->ocsp->ocsp_result->result_msg;
 378 }
 379
 380 int
 381 tls_peer_ocsp_response_status(struct tls *ctx)
 382 {
 383         if (ctx->ocsp == NULL)
 384                 return -1;
 385         if (ctx->ocsp->ocsp_result == NULL)
 386                 return -1;
 387         return ctx->ocsp->ocsp_result->response_status;
 388 }
 389
 390 int
 391 tls_peer_ocsp_cert_status(struct tls *ctx)
 392 {
 393         if (ctx->ocsp == NULL)
 394                 return -1;
 395         if (ctx->ocsp->ocsp_result == NULL)
 396                 return -1;
 397         return ctx->ocsp->ocsp_result->cert_status;
 398 }
 399
 400 int
 401 tls_peer_ocsp_crl_reason(struct tls *ctx)
 402 {
 403         if (ctx->ocsp == NULL)
 404                 return -1;
 405         if (ctx->ocsp->ocsp_result == NULL)
 406                 return -1;
 407         return ctx->ocsp->ocsp_result->crl_reason;
 408 }
 409
 410 time_t
 411 tls_peer_ocsp_this_update(struct tls *ctx)
 412 {
 413         if (ctx->ocsp == NULL)
 414                 return -1;
 415         if (ctx->ocsp->ocsp_result == NULL)
 416                 return -1;
 417         return ctx->ocsp->ocsp_result->this_update;
 418 }
 419
 420 time_t
 421 tls_peer_ocsp_next_update(struct tls *ctx)
 422 {
 423         if (ctx->ocsp == NULL)
 424                 return -1;
 425         if (ctx->ocsp->ocsp_result == NULL)
 426                 return -1;
 427         return ctx->ocsp->ocsp_result->next_update;
 428 }
 429
 430 time_t
 431 tls_peer_ocsp_revocation_time(struct tls *ctx)
 432 {
 433         if (ctx->ocsp == NULL)
 434                 return -1;
 435         if (ctx->ocsp->ocsp_result == NULL)
 436                 return -1;
 437         return ctx->ocsp->ocsp_result->revocation_time;
 438 }
 439
 440 int
 441 tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
 442     size_t size)
 443 {
 444         if ((ctx->state & TLS_HANDSHAKE_COMPLETE) == 0)
 445                 return -1;
 446         return tls_ocsp_process_response_internal(ctx, response, size);
 447 }