1 /* $OpenBSD: tls_ocsp.c,v 1.26 2024/03/26 06:24:52 joshua 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 <string.h>
25
26 #include <openssl/err.h>
27 #include <openssl/ocsp.h>
28 #include <openssl/posix_time.h>
29 #include <openssl/x509.h>
30
31 #include <tls.h>
32 #include "tls_internal.h"
33
34 #define MAXAGE_SEC (14*24*60*60)
35 #define JITTER_SEC (60)
36
37 /*
38 * State for request.
39 */
40
41 static struct tls_ocsp *
tls_ocsp_new(void)42 tls_ocsp_new(void)
43 {
44 return (calloc(1, sizeof(struct tls_ocsp)));
45 }
46
47 void
tls_ocsp_free(struct tls_ocsp * ocsp)48 tls_ocsp_free(struct tls_ocsp *ocsp)
49 {
50 if (ocsp == NULL)
51 return;
52
53 X509_free(ocsp->main_cert);
54 free(ocsp->ocsp_result);
55 free(ocsp->ocsp_url);
56
57 free(ocsp);
58 }
59
60 static int
tls_ocsp_asn1_parse_time(struct tls * ctx,ASN1_GENERALIZEDTIME * gt,time_t * gt_time)61 tls_ocsp_asn1_parse_time(struct tls *ctx, ASN1_GENERALIZEDTIME *gt, time_t *gt_time)
62 {
63 struct tm tm;
64
65 if (gt == NULL)
66 return -1;
67 /* RFC 6960 specifies that all times in OCSP must be GENERALIZEDTIME */
68 if (!ASN1_GENERALIZEDTIME_check(gt))
69 return -1;
70 if (!ASN1_TIME_to_tm(gt, &tm))
71 return -1;
72 if (!OPENSSL_timegm(&tm, gt_time))
73 return -1;
74 return 0;
75 }
76
77 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)78 tls_ocsp_fill_info(struct tls *ctx, int response_status, int cert_status,
79 int crl_reason, ASN1_GENERALIZEDTIME *revtime,
80 ASN1_GENERALIZEDTIME *thisupd, ASN1_GENERALIZEDTIME *nextupd)
81 {
82 struct tls_ocsp_result *info = NULL;
83
84 free(ctx->ocsp->ocsp_result);
85 ctx->ocsp->ocsp_result = NULL;
86
87 if ((info = calloc(1, sizeof (struct tls_ocsp_result))) == NULL) {
88 tls_set_error(ctx, TLS_ERROR_OUT_OF_MEMORY, "out of memory");
89 return -1;
90 }
91 info->response_status = response_status;
92 info->cert_status = cert_status;
93 info->crl_reason = crl_reason;
94 if (info->response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
95 info->result_msg =
96 OCSP_response_status_str(info->response_status);
97 } else if (info->cert_status != V_OCSP_CERTSTATUS_REVOKED) {
98 info->result_msg = OCSP_cert_status_str(info->cert_status);
99 } else {
100 info->result_msg = OCSP_crl_reason_str(info->crl_reason);
101 }
102 info->revocation_time = info->this_update = info->next_update = -1;
103 if (revtime != NULL &&
104 tls_ocsp_asn1_parse_time(ctx, revtime, &info->revocation_time) != 0) {
105 tls_set_error(ctx, TLS_ERROR_UNKNOWN,
106 "unable to parse revocation time in OCSP reply");
107 goto err;
108 }
109 if (thisupd != NULL &&
110 tls_ocsp_asn1_parse_time(ctx, thisupd, &info->this_update) != 0) {
111 tls_set_error(ctx, TLS_ERROR_UNKNOWN,
112 "unable to parse this update time in OCSP reply");
113 goto err;
114 }
115 if (nextupd != NULL &&
116 tls_ocsp_asn1_parse_time(ctx, nextupd, &info->next_update) != 0) {
117 tls_set_error(ctx, TLS_ERROR_UNKNOWN,
118 "unable to parse next update time in OCSP reply");
119 goto err;
120 }
121 ctx->ocsp->ocsp_result = info;
122 return 0;
123
124 err:
125 free(info);
126 return -1;
127 }
128
129 static OCSP_CERTID *
tls_ocsp_get_certid(X509 * main_cert,STACK_OF (X509)* extra_certs,SSL_CTX * ssl_ctx)130 tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
131 SSL_CTX *ssl_ctx)
132 {
133 X509_NAME *issuer_name;
134 X509 *issuer;
135 X509_STORE_CTX *storectx = NULL;
136 X509_OBJECT *obj = NULL;
137 OCSP_CERTID *cid = NULL;
138 X509_STORE *store;
139
140 if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
141 goto out;
142
143 if (extra_certs != NULL) {
144 issuer = X509_find_by_subject(extra_certs, issuer_name);
145 if (issuer != NULL) {
146 cid = OCSP_cert_to_id(NULL, main_cert, issuer);
147 goto out;
148 }
149 }
150
151 if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
152 goto out;
153 if ((storectx = X509_STORE_CTX_new()) == NULL)
154 goto out;
155 if (X509_STORE_CTX_init(storectx, store, main_cert, extra_certs) != 1)
156 goto out;
157 if ((obj = X509_STORE_CTX_get_obj_by_subject(storectx, X509_LU_X509,
158 issuer_name)) == NULL)
159 goto out;
160
161 cid = OCSP_cert_to_id(NULL, main_cert, X509_OBJECT_get0_X509(obj));
162
163 out:
164 X509_STORE_CTX_free(storectx);
165 X509_OBJECT_free(obj);
166
167 return cid;
168 }
169
170 struct tls_ocsp *
tls_ocsp_setup_from_peer(struct tls * ctx)171 tls_ocsp_setup_from_peer(struct tls *ctx)
172 {
173 struct tls_ocsp *ocsp = NULL;
174 STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
175
176 if ((ocsp = tls_ocsp_new()) == NULL)
177 goto err;
178
179 /* steal state from ctx struct */
180 ocsp->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
181 ocsp->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
182 if (ocsp->main_cert == NULL) {
183 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
184 "no peer certificate for OCSP");
185 goto err;
186 }
187
188 ocsp_urls = X509_get1_ocsp(ocsp->main_cert);
189 if (ocsp_urls == NULL) {
190 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
191 "no OCSP URLs in peer certificate");
192 goto err;
193 }
194
195 ocsp->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
196 if (ocsp->ocsp_url == NULL) {
197 tls_set_errorx(ctx, TLS_ERROR_OUT_OF_MEMORY, "out of memory");
198 goto err;
199 }
200
201 X509_email_free(ocsp_urls);
202 return ocsp;
203
204 err:
205 tls_ocsp_free(ocsp);
206 X509_email_free(ocsp_urls);
207 return NULL;
208 }
209
210 static int
tls_ocsp_verify_response(struct tls * ctx,OCSP_RESPONSE * resp)211 tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
212 {
213 OCSP_BASICRESP *br = NULL;
214 ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
215 OCSP_CERTID *cid = NULL;
216 STACK_OF(X509) *combined = NULL;
217 int response_status=0, cert_status=0, crl_reason=0;
218 int ret = -1;
219 unsigned long flags;
220
221 if ((br = OCSP_response_get1_basic(resp)) == NULL) {
222 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "cannot load ocsp reply");
223 goto err;
224 }
225
226 /*
227 * Skip validation of 'extra_certs' as this should be done
228 * already as part of main handshake.
229 */
230 flags = OCSP_TRUSTOTHER;
231
232 /* now verify */
233 if (OCSP_basic_verify(br, ctx->ocsp->extra_certs,
234 SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
235 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "ocsp verify failed");
236 goto err;
237 }
238
239 /* signature OK, look inside */
240 response_status = OCSP_response_status(resp);
241 if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
242 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
243 "ocsp verify failed: response - %s",
244 OCSP_response_status_str(response_status));
245 goto err;
246 }
247
248 cid = tls_ocsp_get_certid(ctx->ocsp->main_cert,
249 ctx->ocsp->extra_certs, ctx->ssl_ctx);
250 if (cid == NULL) {
251 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
252 "ocsp verify failed: no issuer cert");
253 goto err;
254 }
255
256 if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
257 &revtime, &thisupd, &nextupd) != 1) {
258 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
259 "ocsp verify failed: no result for cert");
260 goto err;
261 }
262
263 if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
264 MAXAGE_SEC) != 1) {
265 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
266 "ocsp verify failed: ocsp response not current");
267 goto err;
268 }
269
270 if (tls_ocsp_fill_info(ctx, response_status, cert_status,
271 crl_reason, revtime, thisupd, nextupd) != 0)
272 goto err;
273
274 /* finally can look at status */
275 if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
276 V_OCSP_CERTSTATUS_UNKNOWN) {
277 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
278 "ocsp verify failed: revoked cert - %s",
279 OCSP_crl_reason_str(crl_reason));
280 goto err;
281 }
282 ret = 0;
283
284 err:
285 sk_X509_free(combined);
286 OCSP_CERTID_free(cid);
287 OCSP_BASICRESP_free(br);
288 return ret;
289 }
290
291 /*
292 * Process a raw OCSP response from an OCSP server request.
293 * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
294 * returns 0 if certificate ok, -1 otherwise.
295 */
296 static int
tls_ocsp_process_response_internal(struct tls * ctx,const unsigned char * response,size_t size)297 tls_ocsp_process_response_internal(struct tls *ctx, const unsigned char *response,
298 size_t size)
299 {
300 int ret;
301 OCSP_RESPONSE *resp;
302
303 resp = d2i_OCSP_RESPONSE(NULL, &response, size);
304 if (resp == NULL) {
305 tls_ocsp_free(ctx->ocsp);
306 ctx->ocsp = NULL;
307 tls_set_error(ctx, TLS_ERROR_UNKNOWN,
308 "unable to parse OCSP response");
309 return -1;
310 }
311 ret = tls_ocsp_verify_response(ctx, resp);
312 OCSP_RESPONSE_free(resp);
313 return ret;
314 }
315
316 /* TLS handshake verification callback for stapled requests */
317 int
tls_ocsp_verify_cb(SSL * ssl,void * arg)318 tls_ocsp_verify_cb(SSL *ssl, void *arg)
319 {
320 const unsigned char *raw = NULL;
321 int size, res = -1;
322 struct tls *ctx;
323
324 if ((ctx = SSL_get_app_data(ssl)) == NULL)
325 return -1;
326
327 size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
328 if (size <= 0) {
329 if (ctx->config->ocsp_require_stapling) {
330 tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
331 "no stapled OCSP response provided");
332 return 0;
333 }
334 return 1;
335 }
336
337 tls_ocsp_free(ctx->ocsp);
338 if ((ctx->ocsp = tls_ocsp_setup_from_peer(ctx)) == NULL)
339 return 0;
340
341 if (ctx->config->verify_cert == 0 || ctx->config->verify_time == 0)
342 return 1;
343
344 res = tls_ocsp_process_response_internal(ctx, raw, size);
345
346 return (res == 0) ? 1 : 0;
347 }
348
349
350 /* Staple the OCSP information in ctx->ocsp to the server handshake. */
351 int
tls_ocsp_stapling_cb(SSL * ssl,void * arg)352 tls_ocsp_stapling_cb(SSL *ssl, void *arg)
353 {
354 int ret = SSL_TLSEXT_ERR_ALERT_FATAL;
355 unsigned char *ocsp_staple = NULL;
356 struct tls *ctx;
357
358 if ((ctx = SSL_get_app_data(ssl)) == NULL)
359 goto err;
360
361 if (ctx->keypair == NULL || ctx->keypair->ocsp_staple == NULL ||
362 ctx->keypair->ocsp_staple_len == 0)
363 return SSL_TLSEXT_ERR_NOACK;
364
365 if ((ocsp_staple = malloc(ctx->keypair->ocsp_staple_len)) == NULL)
366 goto err;
367
368 memcpy(ocsp_staple, ctx->keypair->ocsp_staple,
369 ctx->keypair->ocsp_staple_len);
370
371 if (SSL_set_tlsext_status_ocsp_resp(ctx->ssl_conn, ocsp_staple,
372 ctx->keypair->ocsp_staple_len) != 1)
373 goto err;
374
375 ret = SSL_TLSEXT_ERR_OK;
376 err:
377 if (ret != SSL_TLSEXT_ERR_OK)
378 free(ocsp_staple);
379
380 return ret;
381 }
382
383 /*
384 * Public API
385 */
386
387 /* Retrieve OCSP URL from peer certificate, if present. */
388 const char *
tls_peer_ocsp_url(struct tls * ctx)389 tls_peer_ocsp_url(struct tls *ctx)
390 {
391 if (ctx->ocsp == NULL)
392 return NULL;
393 return ctx->ocsp->ocsp_url;
394 }
395
396 const char *
tls_peer_ocsp_result(struct tls * ctx)397 tls_peer_ocsp_result(struct tls *ctx)
398 {
399 if (ctx->ocsp == NULL)
400 return NULL;
401 if (ctx->ocsp->ocsp_result == NULL)
402 return NULL;
403 return ctx->ocsp->ocsp_result->result_msg;
404 }
405
406 int
tls_peer_ocsp_response_status(struct tls * ctx)407 tls_peer_ocsp_response_status(struct tls *ctx)
408 {
409 if (ctx->ocsp == NULL)
410 return -1;
411 if (ctx->ocsp->ocsp_result == NULL)
412 return -1;
413 return ctx->ocsp->ocsp_result->response_status;
414 }
415
416 int
tls_peer_ocsp_cert_status(struct tls * ctx)417 tls_peer_ocsp_cert_status(struct tls *ctx)
418 {
419 if (ctx->ocsp == NULL)
420 return -1;
421 if (ctx->ocsp->ocsp_result == NULL)
422 return -1;
423 return ctx->ocsp->ocsp_result->cert_status;
424 }
425
426 int
tls_peer_ocsp_crl_reason(struct tls * ctx)427 tls_peer_ocsp_crl_reason(struct tls *ctx)
428 {
429 if (ctx->ocsp == NULL)
430 return -1;
431 if (ctx->ocsp->ocsp_result == NULL)
432 return -1;
433 return ctx->ocsp->ocsp_result->crl_reason;
434 }
435
436 time_t
tls_peer_ocsp_this_update(struct tls * ctx)437 tls_peer_ocsp_this_update(struct tls *ctx)
438 {
439 if (ctx->ocsp == NULL)
440 return -1;
441 if (ctx->ocsp->ocsp_result == NULL)
442 return -1;
443 return ctx->ocsp->ocsp_result->this_update;
444 }
445
446 time_t
tls_peer_ocsp_next_update(struct tls * ctx)447 tls_peer_ocsp_next_update(struct tls *ctx)
448 {
449 if (ctx->ocsp == NULL)
450 return -1;
451 if (ctx->ocsp->ocsp_result == NULL)
452 return -1;
453 return ctx->ocsp->ocsp_result->next_update;
454 }
455
456 time_t
tls_peer_ocsp_revocation_time(struct tls * ctx)457 tls_peer_ocsp_revocation_time(struct tls *ctx)
458 {
459 if (ctx->ocsp == NULL)
460 return -1;
461 if (ctx->ocsp->ocsp_result == NULL)
462 return -1;
463 return ctx->ocsp->ocsp_result->revocation_time;
464 }
465
466 int
tls_ocsp_process_response(struct tls * ctx,const unsigned char * response,size_t size)467 tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
468 size_t size)
469 {
470 if ((ctx->state & TLS_HANDSHAKE_COMPLETE) == 0)
471 return -1;
472 return tls_ocsp_process_response_internal(ctx, response, size);
473 }
474