1 /* $OpenBSD: tls_ocsp.c,v 1.22 2021/10/31 16:39:32 tb Exp $ */
2 /*
3 * Copyright (c) 2015 Marko Kreen <markokr@gmail.com>
4 * Copyright (c) 2016 Bob Beck <beck@openbsd.org>
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19 #include <sys/types.h>
20
21 #include <arpa/inet.h>
22 #include <netinet/in.h>
23
24 #include <openssl/err.h>
25 #include <openssl/ocsp.h>
26 #include <openssl/x509.h>
27
28 #include <tls.h>
29 #include "tls_internal.h"
30
31 #define MAXAGE_SEC (14*24*60*60)
32 #define JITTER_SEC (60)
33
34 /*
35 * State for request.
36 */
37
38 static struct tls_ocsp *
tls_ocsp_new(void)39 tls_ocsp_new(void)
40 {
41 return (calloc(1, sizeof(struct tls_ocsp)));
42 }
43
44 void
tls_ocsp_free(struct tls_ocsp * ocsp)45 tls_ocsp_free(struct tls_ocsp *ocsp)
46 {
47 if (ocsp == NULL)
48 return;
49
50 X509_free(ocsp->main_cert);
51 free(ocsp->ocsp_result);
52 free(ocsp->ocsp_url);
53
54 free(ocsp);
55 }
56
57 static int
tls_ocsp_asn1_parse_time(struct tls * ctx,ASN1_GENERALIZEDTIME * gt,time_t * gt_time)58 tls_ocsp_asn1_parse_time(struct tls *ctx, ASN1_GENERALIZEDTIME *gt, time_t *gt_time)
59 {
60 struct tm tm;
61
62 if (gt == NULL)
63 return -1;
64 /* RFC 6960 specifies that all times in OCSP must be GENERALIZEDTIME */
65 if (ASN1_time_parse(gt->data, gt->length, &tm,
66 V_ASN1_GENERALIZEDTIME) == -1)
67 return -1;
68 if ((*gt_time = timegm(&tm)) == -1)
69 return -1;
70 return 0;
71 }
72
73 static int
tls_ocsp_fill_info(struct tls * ctx,int response_status,int cert_status,int crl_reason,ASN1_GENERALIZEDTIME * revtime,ASN1_GENERALIZEDTIME * thisupd,ASN1_GENERALIZEDTIME * nextupd)74 tls_ocsp_fill_info(struct tls *ctx, int response_status, int cert_status,
75 int crl_reason, ASN1_GENERALIZEDTIME *revtime,
76 ASN1_GENERALIZEDTIME *thisupd, ASN1_GENERALIZEDTIME *nextupd)
77 {
78 struct tls_ocsp_result *info = NULL;
79
80 free(ctx->ocsp->ocsp_result);
81 ctx->ocsp->ocsp_result = NULL;
82
83 if ((info = calloc(1, sizeof (struct tls_ocsp_result))) == NULL) {
84 tls_set_error(ctx, "calloc");
85 return -1;
86 }
87 info->response_status = response_status;
88 info->cert_status = cert_status;
89 info->crl_reason = crl_reason;
90 if (info->response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
91 info->result_msg =
92 OCSP_response_status_str(info->response_status);
93 } else if (info->cert_status != V_OCSP_CERTSTATUS_REVOKED) {
94 info->result_msg = OCSP_cert_status_str(info->cert_status);
95 } else {
96 info->result_msg = OCSP_crl_reason_str(info->crl_reason);
97 }
98 info->revocation_time = info->this_update = info->next_update = -1;
99 if (revtime != NULL &&
100 tls_ocsp_asn1_parse_time(ctx, revtime, &info->revocation_time) != 0) {
101 tls_set_error(ctx,
102 "unable to parse revocation time in OCSP reply");
103 goto err;
104 }
105 if (thisupd != NULL &&
106 tls_ocsp_asn1_parse_time(ctx, thisupd, &info->this_update) != 0) {
107 tls_set_error(ctx,
108 "unable to parse this update time in OCSP reply");
109 goto err;
110 }
111 if (nextupd != NULL &&
112 tls_ocsp_asn1_parse_time(ctx, nextupd, &info->next_update) != 0) {
113 tls_set_error(ctx,
114 "unable to parse next update time in OCSP reply");
115 goto err;
116 }
117 ctx->ocsp->ocsp_result = info;
118 return 0;
119
120 err:
121 free(info);
122 return -1;
123 }
124
125 static OCSP_CERTID *
tls_ocsp_get_certid(X509 * main_cert,STACK_OF (X509)* extra_certs,SSL_CTX * ssl_ctx)126 tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
127 SSL_CTX *ssl_ctx)
128 {
129 X509_NAME *issuer_name;
130 X509 *issuer;
131 X509_STORE_CTX *storectx = NULL;
132 X509_OBJECT *obj = NULL;
133 OCSP_CERTID *cid = NULL;
134 X509_STORE *store;
135
136 if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
137 goto out;
138
139 if (extra_certs != NULL) {
140 issuer = X509_find_by_subject(extra_certs, issuer_name);
141 if (issuer != NULL) {
142 cid = OCSP_cert_to_id(NULL, main_cert, issuer);
143 goto out;
144 }
145 }
146
147 if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
148 goto out;
149 if ((storectx = X509_STORE_CTX_new()) == NULL)
150 goto out;
151 if (X509_STORE_CTX_init(storectx, store, main_cert, extra_certs) != 1)
152 goto out;
153 if ((obj = X509_STORE_CTX_get_obj_by_subject(storectx, X509_LU_X509,
154 issuer_name)) == NULL)
155 goto out;
156
157 cid = OCSP_cert_to_id(NULL, main_cert, X509_OBJECT_get0_X509(obj));
158
159 out:
160 X509_STORE_CTX_free(storectx);
161 X509_OBJECT_free(obj);
162
163 return cid;
164 }
165
166 struct tls_ocsp *
tls_ocsp_setup_from_peer(struct tls * ctx)167 tls_ocsp_setup_from_peer(struct tls *ctx)
168 {
169 struct tls_ocsp *ocsp = NULL;
170 STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
171
172 if ((ocsp = tls_ocsp_new()) == NULL)
173 goto err;
174
175 /* steal state from ctx struct */
176 ocsp->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
177 ocsp->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
178 if (ocsp->main_cert == NULL) {
179 tls_set_errorx(ctx, "no peer certificate for OCSP");
180 goto err;
181 }
182
183 ocsp_urls = X509_get1_ocsp(ocsp->main_cert);
184 if (ocsp_urls == NULL) {
185 tls_set_errorx(ctx, "no OCSP URLs in peer certificate");
186 goto err;
187 }
188
189 ocsp->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
190 if (ocsp->ocsp_url == NULL) {
191 tls_set_errorx(ctx, "out of memory");
192 goto err;
193 }
194
195 X509_email_free(ocsp_urls);
196 return ocsp;
197
198 err:
199 tls_ocsp_free(ocsp);
200 X509_email_free(ocsp_urls);
201 return NULL;
202 }
203
204 static int
tls_ocsp_verify_response(struct tls * ctx,OCSP_RESPONSE * resp)205 tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
206 {
207 OCSP_BASICRESP *br = NULL;
208 ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
209 OCSP_CERTID *cid = NULL;
210 STACK_OF(X509) *combined = NULL;
211 int response_status=0, cert_status=0, crl_reason=0;
212 int ret = -1;
213 unsigned long flags;
214
215 if ((br = OCSP_response_get1_basic(resp)) == NULL) {
216 tls_set_errorx(ctx, "cannot load ocsp reply");
217 goto err;
218 }
219
220 /*
221 * Skip validation of 'extra_certs' as this should be done
222 * already as part of main handshake.
223 */
224 flags = OCSP_TRUSTOTHER;
225
226 /* now verify */
227 if (OCSP_basic_verify(br, ctx->ocsp->extra_certs,
228 SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
229 tls_set_errorx(ctx, "ocsp verify failed");
230 goto err;
231 }
232
233 /* signature OK, look inside */
234 response_status = OCSP_response_status(resp);
235 if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
236 tls_set_errorx(ctx, "ocsp verify failed: response - %s",
237 OCSP_response_status_str(response_status));
238 goto err;
239 }
240
241 cid = tls_ocsp_get_certid(ctx->ocsp->main_cert,
242 ctx->ocsp->extra_certs, ctx->ssl_ctx);
243 if (cid == NULL) {
244 tls_set_errorx(ctx, "ocsp verify failed: no issuer cert");
245 goto err;
246 }
247
248 if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
249 &revtime, &thisupd, &nextupd) != 1) {
250 tls_set_errorx(ctx, "ocsp verify failed: no result for cert");
251 goto err;
252 }
253
254 if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
255 MAXAGE_SEC) != 1) {
256 tls_set_errorx(ctx,
257 "ocsp verify failed: ocsp response not current");
258 goto err;
259 }
260
261 if (tls_ocsp_fill_info(ctx, response_status, cert_status,
262 crl_reason, revtime, thisupd, nextupd) != 0)
263 goto err;
264
265 /* finally can look at status */
266 if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
267 V_OCSP_CERTSTATUS_UNKNOWN) {
268 tls_set_errorx(ctx, "ocsp verify failed: revoked cert - %s",
269 OCSP_crl_reason_str(crl_reason));
270 goto err;
271 }
272 ret = 0;
273
274 err:
275 sk_X509_free(combined);
276 OCSP_CERTID_free(cid);
277 OCSP_BASICRESP_free(br);
278 return ret;
279 }
280
281 /*
282 * Process a raw OCSP response from an OCSP server request.
283 * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
284 * returns 0 if certificate ok, -1 otherwise.
285 */
286 static int
tls_ocsp_process_response_internal(struct tls * ctx,const unsigned char * response,size_t size)287 tls_ocsp_process_response_internal(struct tls *ctx, const unsigned char *response,
288 size_t size)
289 {
290 int ret;
291 OCSP_RESPONSE *resp;
292
293 resp = d2i_OCSP_RESPONSE(NULL, &response, size);
294 if (resp == NULL) {
295 tls_ocsp_free(ctx->ocsp);
296 ctx->ocsp = NULL;
297 tls_set_error(ctx, "unable to parse OCSP response");
298 return -1;
299 }
300 ret = tls_ocsp_verify_response(ctx, resp);
301 OCSP_RESPONSE_free(resp);
302 return ret;
303 }
304
305 /* TLS handshake verification callback for stapled requests */
306 int
tls_ocsp_verify_cb(SSL * ssl,void * arg)307 tls_ocsp_verify_cb(SSL *ssl, void *arg)
308 {
309 const unsigned char *raw = NULL;
310 int size, res = -1;
311 struct tls *ctx;
312
313 if ((ctx = SSL_get_app_data(ssl)) == NULL)
314 return -1;
315
316 size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
317 if (size <= 0) {
318 if (ctx->config->ocsp_require_stapling) {
319 tls_set_errorx(ctx, "no stapled OCSP response provided");
320 return 0;
321 }
322 return 1;
323 }
324
325 tls_ocsp_free(ctx->ocsp);
326 if ((ctx->ocsp = tls_ocsp_setup_from_peer(ctx)) == NULL)
327 return 0;
328
329 if (ctx->config->verify_cert == 0 || ctx->config->verify_time == 0)
330 return 1;
331
332 res = tls_ocsp_process_response_internal(ctx, raw, size);
333
334 return (res == 0) ? 1 : 0;
335 }
336
337
338 /* Staple the OCSP information in ctx->ocsp to the server handshake. */
339 int
tls_ocsp_stapling_cb(SSL * ssl,void * arg)340 tls_ocsp_stapling_cb(SSL *ssl, void *arg)
341 {
342 int ret = SSL_TLSEXT_ERR_ALERT_FATAL;
343 unsigned char *ocsp_staple = NULL;
344 struct tls *ctx;
345
346 if ((ctx = SSL_get_app_data(ssl)) == NULL)
347 goto err;
348
349 if (ctx->keypair == NULL || ctx->keypair->ocsp_staple == NULL ||
350 ctx->keypair->ocsp_staple_len == 0)
351 return SSL_TLSEXT_ERR_NOACK;
352
353 if ((ocsp_staple = malloc(ctx->keypair->ocsp_staple_len)) == NULL)
354 goto err;
355
356 memcpy(ocsp_staple, ctx->keypair->ocsp_staple,
357 ctx->keypair->ocsp_staple_len);
358
359 if (SSL_set_tlsext_status_ocsp_resp(ctx->ssl_conn, ocsp_staple,
360 ctx->keypair->ocsp_staple_len) != 1)
361 goto err;
362
363 ret = SSL_TLSEXT_ERR_OK;
364 err:
365 if (ret != SSL_TLSEXT_ERR_OK)
366 free(ocsp_staple);
367
368 return ret;
369 }
370
371 /*
372 * Public API
373 */
374
375 /* Retrieve OCSP URL from peer certificate, if present. */
376 const char *
tls_peer_ocsp_url(struct tls * ctx)377 tls_peer_ocsp_url(struct tls *ctx)
378 {
379 if (ctx->ocsp == NULL)
380 return NULL;
381 return ctx->ocsp->ocsp_url;
382 }
383
384 const char *
tls_peer_ocsp_result(struct tls * ctx)385 tls_peer_ocsp_result(struct tls *ctx)
386 {
387 if (ctx->ocsp == NULL)
388 return NULL;
389 if (ctx->ocsp->ocsp_result == NULL)
390 return NULL;
391 return ctx->ocsp->ocsp_result->result_msg;
392 }
393
394 int
tls_peer_ocsp_response_status(struct tls * ctx)395 tls_peer_ocsp_response_status(struct tls *ctx)
396 {
397 if (ctx->ocsp == NULL)
398 return -1;
399 if (ctx->ocsp->ocsp_result == NULL)
400 return -1;
401 return ctx->ocsp->ocsp_result->response_status;
402 }
403
404 int
tls_peer_ocsp_cert_status(struct tls * ctx)405 tls_peer_ocsp_cert_status(struct tls *ctx)
406 {
407 if (ctx->ocsp == NULL)
408 return -1;
409 if (ctx->ocsp->ocsp_result == NULL)
410 return -1;
411 return ctx->ocsp->ocsp_result->cert_status;
412 }
413
414 int
tls_peer_ocsp_crl_reason(struct tls * ctx)415 tls_peer_ocsp_crl_reason(struct tls *ctx)
416 {
417 if (ctx->ocsp == NULL)
418 return -1;
419 if (ctx->ocsp->ocsp_result == NULL)
420 return -1;
421 return ctx->ocsp->ocsp_result->crl_reason;
422 }
423
424 time_t
tls_peer_ocsp_this_update(struct tls * ctx)425 tls_peer_ocsp_this_update(struct tls *ctx)
426 {
427 if (ctx->ocsp == NULL)
428 return -1;
429 if (ctx->ocsp->ocsp_result == NULL)
430 return -1;
431 return ctx->ocsp->ocsp_result->this_update;
432 }
433
434 time_t
tls_peer_ocsp_next_update(struct tls * ctx)435 tls_peer_ocsp_next_update(struct tls *ctx)
436 {
437 if (ctx->ocsp == NULL)
438 return -1;
439 if (ctx->ocsp->ocsp_result == NULL)
440 return -1;
441 return ctx->ocsp->ocsp_result->next_update;
442 }
443
444 time_t
tls_peer_ocsp_revocation_time(struct tls * ctx)445 tls_peer_ocsp_revocation_time(struct tls *ctx)
446 {
447 if (ctx->ocsp == NULL)
448 return -1;
449 if (ctx->ocsp->ocsp_result == NULL)
450 return -1;
451 return ctx->ocsp->ocsp_result->revocation_time;
452 }
453
454 int
tls_ocsp_process_response(struct tls * ctx,const unsigned char * response,size_t size)455 tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
456 size_t size)
457 {
458 if ((ctx->state & TLS_HANDSHAKE_COMPLETE) == 0)
459 return -1;
460 return tls_ocsp_process_response_internal(ctx, response, size);
461 }
462