xref: /openbsd-src/lib/libtls/tls_ocsp.c (revision 3d61058aa5c692477b6d18acfbbdb653a9930ff9) 
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 *
42 tls_ocsp_new(void)
43 {
44 	return (calloc(1, sizeof(struct tls_ocsp)));
45 }
46 
47 void
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
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
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 *
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 *
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
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
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
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
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 *
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 *
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
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
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
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
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
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
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
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