1 /* $OpenBSD: tls_ocsp.c,v 1.19 2019/12/03 14:56:42 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;
132 X509_OBJECT tmpobj;
133 OCSP_CERTID *cid = NULL;
134 X509_STORE *store;
135
136 if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
137 return NULL;
138
139 if (extra_certs != NULL) {
140 issuer = X509_find_by_subject(extra_certs, issuer_name);
141 if (issuer != NULL)
142 return OCSP_cert_to_id(NULL, main_cert, issuer);
143 }
144
145 if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
146 return NULL;
147 if (X509_STORE_CTX_init(&storectx, store, main_cert, extra_certs) != 1)
148 return NULL;
149 if (X509_STORE_get_by_subject(&storectx, X509_LU_X509, issuer_name,
150 &tmpobj) == 1) {
151 cid = OCSP_cert_to_id(NULL, main_cert, tmpobj.data.x509);
152 X509_OBJECT_free_contents(&tmpobj);
153 }
154 X509_STORE_CTX_cleanup(&storectx);
155 return cid;
156 }
157
158 struct tls_ocsp *
tls_ocsp_setup_from_peer(struct tls * ctx)159 tls_ocsp_setup_from_peer(struct tls *ctx)
160 {
161 struct tls_ocsp *ocsp = NULL;
162 STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
163
164 if ((ocsp = tls_ocsp_new()) == NULL)
165 goto err;
166
167 /* steal state from ctx struct */
168 ocsp->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
169 ocsp->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
170 if (ocsp->main_cert == NULL) {
171 tls_set_errorx(ctx, "no peer certificate for OCSP");
172 goto err;
173 }
174
175 ocsp_urls = X509_get1_ocsp(ocsp->main_cert);
176 if (ocsp_urls == NULL) {
177 tls_set_errorx(ctx, "no OCSP URLs in peer certificate");
178 goto err;
179 }
180
181 ocsp->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
182 if (ocsp->ocsp_url == NULL) {
183 tls_set_errorx(ctx, "out of memory");
184 goto err;
185 }
186
187 X509_email_free(ocsp_urls);
188 return ocsp;
189
190 err:
191 tls_ocsp_free(ocsp);
192 X509_email_free(ocsp_urls);
193 return NULL;
194 }
195
196 static int
tls_ocsp_verify_response(struct tls * ctx,OCSP_RESPONSE * resp)197 tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
198 {
199 OCSP_BASICRESP *br = NULL;
200 ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
201 OCSP_CERTID *cid = NULL;
202 STACK_OF(X509) *combined = NULL;
203 int response_status=0, cert_status=0, crl_reason=0;
204 int ret = -1;
205 unsigned long flags;
206
207 if ((br = OCSP_response_get1_basic(resp)) == NULL) {
208 tls_set_errorx(ctx, "cannot load ocsp reply");
209 goto err;
210 }
211
212 /*
213 * Skip validation of 'extra_certs' as this should be done
214 * already as part of main handshake.
215 */
216 flags = OCSP_TRUSTOTHER;
217
218 /* now verify */
219 if (OCSP_basic_verify(br, ctx->ocsp->extra_certs,
220 SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
221 tls_set_error(ctx, "ocsp verify failed");
222 goto err;
223 }
224
225 /* signature OK, look inside */
226 response_status = OCSP_response_status(resp);
227 if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
228 tls_set_errorx(ctx, "ocsp verify failed: response - %s",
229 OCSP_response_status_str(response_status));
230 goto err;
231 }
232
233 cid = tls_ocsp_get_certid(ctx->ocsp->main_cert,
234 ctx->ocsp->extra_certs, ctx->ssl_ctx);
235 if (cid == NULL) {
236 tls_set_errorx(ctx, "ocsp verify failed: no issuer cert");
237 goto err;
238 }
239
240 if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
241 &revtime, &thisupd, &nextupd) != 1) {
242 tls_set_errorx(ctx, "ocsp verify failed: no result for cert");
243 goto err;
244 }
245
246 if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
247 MAXAGE_SEC) != 1) {
248 tls_set_errorx(ctx,
249 "ocsp verify failed: ocsp response not current");
250 goto err;
251 }
252
253 if (tls_ocsp_fill_info(ctx, response_status, cert_status,
254 crl_reason, revtime, thisupd, nextupd) != 0)
255 goto err;
256
257 /* finally can look at status */
258 if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
259 V_OCSP_CERTSTATUS_UNKNOWN) {
260 tls_set_errorx(ctx, "ocsp verify failed: revoked cert - %s",
261 OCSP_crl_reason_str(crl_reason));
262 goto err;
263 }
264 ret = 0;
265
266 err:
267 sk_X509_free(combined);
268 OCSP_CERTID_free(cid);
269 OCSP_BASICRESP_free(br);
270 return ret;
271 }
272
273 /*
274 * Process a raw OCSP response from an OCSP server request.
275 * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
276 * returns 0 if certificate ok, -1 otherwise.
277 */
278 static int
tls_ocsp_process_response_internal(struct tls * ctx,const unsigned char * response,size_t size)279 tls_ocsp_process_response_internal(struct tls *ctx, const unsigned char *response,
280 size_t size)
281 {
282 int ret;
283 OCSP_RESPONSE *resp;
284
285 resp = d2i_OCSP_RESPONSE(NULL, &response, size);
286 if (resp == NULL) {
287 tls_ocsp_free(ctx->ocsp);
288 ctx->ocsp = NULL;
289 tls_set_error(ctx, "unable to parse OCSP response");
290 return -1;
291 }
292 ret = tls_ocsp_verify_response(ctx, resp);
293 OCSP_RESPONSE_free(resp);
294 return ret;
295 }
296
297 /* TLS handshake verification callback for stapled requests */
298 int
tls_ocsp_verify_cb(SSL * ssl,void * arg)299 tls_ocsp_verify_cb(SSL *ssl, void *arg)
300 {
301 const unsigned char *raw = NULL;
302 int size, res = -1;
303 struct tls *ctx;
304
305 if ((ctx = SSL_get_app_data(ssl)) == NULL)
306 return -1;
307
308 size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
309 if (size <= 0) {
310 if (ctx->config->ocsp_require_stapling) {
311 tls_set_errorx(ctx, "no stapled OCSP response provided");
312 return 0;
313 }
314 return 1;
315 }
316
317 tls_ocsp_free(ctx->ocsp);
318 if ((ctx->ocsp = tls_ocsp_setup_from_peer(ctx)) == NULL)
319 return 0;
320
321 if (ctx->config->verify_cert == 0 || ctx->config->verify_time == 0)
322 return 1;
323
324 res = tls_ocsp_process_response_internal(ctx, raw, size);
325
326 return (res == 0) ? 1 : 0;
327 }
328
329
330 /* Staple the OCSP information in ctx->ocsp to the server handshake. */
331 int
tls_ocsp_stapling_cb(SSL * ssl,void * arg)332 tls_ocsp_stapling_cb(SSL *ssl, void *arg)
333 {
334 int ret = SSL_TLSEXT_ERR_ALERT_FATAL;
335 unsigned char *ocsp_staple = NULL;
336 struct tls *ctx;
337
338 if ((ctx = SSL_get_app_data(ssl)) == NULL)
339 goto err;
340
341 if (ctx->keypair == NULL || ctx->keypair->ocsp_staple == NULL ||
342 ctx->keypair->ocsp_staple_len == 0)
343 return SSL_TLSEXT_ERR_NOACK;
344
345 if ((ocsp_staple = malloc(ctx->keypair->ocsp_staple_len)) == NULL)
346 goto err;
347
348 memcpy(ocsp_staple, ctx->keypair->ocsp_staple,
349 ctx->keypair->ocsp_staple_len);
350
351 if (SSL_set_tlsext_status_ocsp_resp(ctx->ssl_conn, ocsp_staple,
352 ctx->keypair->ocsp_staple_len) != 1)
353 goto err;
354
355 ret = SSL_TLSEXT_ERR_OK;
356 err:
357 if (ret != SSL_TLSEXT_ERR_OK)
358 free(ocsp_staple);
359
360 return ret;
361 }
362
363 /*
364 * Public API
365 */
366
367 /* Retrieve OCSP URL from peer certificate, if present. */
368 const char *
tls_peer_ocsp_url(struct tls * ctx)369 tls_peer_ocsp_url(struct tls *ctx)
370 {
371 if (ctx->ocsp == NULL)
372 return NULL;
373 return ctx->ocsp->ocsp_url;
374 }
375
376 const char *
tls_peer_ocsp_result(struct tls * ctx)377 tls_peer_ocsp_result(struct tls *ctx)
378 {
379 if (ctx->ocsp == NULL)
380 return NULL;
381 if (ctx->ocsp->ocsp_result == NULL)
382 return NULL;
383 return ctx->ocsp->ocsp_result->result_msg;
384 }
385
386 int
tls_peer_ocsp_response_status(struct tls * ctx)387 tls_peer_ocsp_response_status(struct tls *ctx)
388 {
389 if (ctx->ocsp == NULL)
390 return -1;
391 if (ctx->ocsp->ocsp_result == NULL)
392 return -1;
393 return ctx->ocsp->ocsp_result->response_status;
394 }
395
396 int
tls_peer_ocsp_cert_status(struct tls * ctx)397 tls_peer_ocsp_cert_status(struct tls *ctx)
398 {
399 if (ctx->ocsp == NULL)
400 return -1;
401 if (ctx->ocsp->ocsp_result == NULL)
402 return -1;
403 return ctx->ocsp->ocsp_result->cert_status;
404 }
405
406 int
tls_peer_ocsp_crl_reason(struct tls * ctx)407 tls_peer_ocsp_crl_reason(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->crl_reason;
414 }
415
416 time_t
tls_peer_ocsp_this_update(struct tls * ctx)417 tls_peer_ocsp_this_update(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->this_update;
424 }
425
426 time_t
tls_peer_ocsp_next_update(struct tls * ctx)427 tls_peer_ocsp_next_update(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->next_update;
434 }
435
436 time_t
tls_peer_ocsp_revocation_time(struct tls * ctx)437 tls_peer_ocsp_revocation_time(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->revocation_time;
444 }
445
446 int
tls_ocsp_process_response(struct tls * ctx,const unsigned char * response,size_t size)447 tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
448 size_t size)
449 {
450 if ((ctx->state & TLS_HANDSHAKE_COMPLETE) == 0)
451 return -1;
452 return tls_ocsp_process_response_internal(ctx, response, size);
453 }
454