1 /*	$OpenBSD: tls_ocsp.c,v 1.24 2023/11/13 10:56:19 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 "config.h"
20 
21 #include <sys/types.h>
22 
23 #include <arpa/inet.h>
24 #include <netinet/in.h>
25 
26 #include <string.h>
27 
28 #include <openssl/err.h>
29 #include <openssl/ocsp.h>
30 #include <openssl/x509.h>
31 
32 #include <tls.h>
33 #include "tls_internal.h"
34 
35 #define MAXAGE_SEC (14*24*60*60)
36 #define JITTER_SEC (60)
37 
38 /*
39  * State for request.
40  */
41 
42 static struct tls_ocsp *
43 tls_ocsp_new(void)
44 {
45 	return (calloc(1, sizeof(struct tls_ocsp)));
46 }
47 
48 void
49 tls_ocsp_free(struct tls_ocsp *ocsp)
50 {
51 	if (ocsp == NULL)
52 		return;
53 
54 	X509_free(ocsp->main_cert);
55 	free(ocsp->ocsp_result);
56 	free(ocsp->ocsp_url);
57 
58 	free(ocsp);
59 }
60 
61 static int
62 tls_ocsp_asn1_parse_time(struct tls *ctx, ASN1_GENERALIZEDTIME *gt, time_t *gt_time)
63 {
64 	struct tm tm;
65 
66 	if (gt == NULL)
67 		return -1;
68 	/* RFC 6960 specifies that all times in OCSP must be GENERALIZEDTIME */
69 	if (!ASN1_GENERALIZEDTIME_check(gt))
70 		return -1;
71 	if (!ASN1_TIME_to_tm(gt, &tm))
72 		return -1;
73 	if ((*gt_time = timegm(&tm)) == -1)
74 		return -1;
75 	return 0;
76 }
77 
78 static int
79 tls_ocsp_fill_info(struct tls *ctx, int response_status, int cert_status,
80     int crl_reason, ASN1_GENERALIZEDTIME *revtime,
81     ASN1_GENERALIZEDTIME *thisupd, ASN1_GENERALIZEDTIME *nextupd)
82 {
83 	struct tls_ocsp_result *info = NULL;
84 
85 	free(ctx->ocsp->ocsp_result);
86 	ctx->ocsp->ocsp_result = NULL;
87 
88 	if ((info = calloc(1, sizeof (struct tls_ocsp_result))) == NULL) {
89 		tls_set_error(ctx, "calloc");
90 		return -1;
91 	}
92 	info->response_status = response_status;
93 	info->cert_status = cert_status;
94 	info->crl_reason = crl_reason;
95 	if (info->response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
96 		info->result_msg =
97 		    OCSP_response_status_str(info->response_status);
98 	} else if (info->cert_status != V_OCSP_CERTSTATUS_REVOKED) {
99 		info->result_msg = OCSP_cert_status_str(info->cert_status);
100 	} else {
101 		info->result_msg = OCSP_crl_reason_str(info->crl_reason);
102 	}
103 	info->revocation_time = info->this_update = info->next_update = -1;
104 	if (revtime != NULL &&
105 	    tls_ocsp_asn1_parse_time(ctx, revtime, &info->revocation_time) != 0) {
106 		tls_set_error(ctx,
107 		    "unable to parse revocation time in OCSP reply");
108 		goto err;
109 	}
110 	if (thisupd != NULL &&
111 	    tls_ocsp_asn1_parse_time(ctx, thisupd, &info->this_update) != 0) {
112 		tls_set_error(ctx,
113 		    "unable to parse this update time in OCSP reply");
114 		goto err;
115 	}
116 	if (nextupd != NULL &&
117 	    tls_ocsp_asn1_parse_time(ctx, nextupd, &info->next_update) != 0) {
118 		tls_set_error(ctx,
119 		    "unable to parse next update time in OCSP reply");
120 		goto err;
121 	}
122 	ctx->ocsp->ocsp_result = info;
123 	return 0;
124 
125  err:
126 	free(info);
127 	return -1;
128 }
129 
130 static OCSP_CERTID *
131 tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
132     SSL_CTX *ssl_ctx)
133 {
134 	X509_NAME *issuer_name;
135 	X509 *issuer;
136 	X509_STORE_CTX *storectx = NULL;
137 	X509_OBJECT *obj = NULL;
138 	OCSP_CERTID *cid = NULL;
139 	X509_STORE *store;
140 
141 	if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
142 		goto out;
143 
144 	if (extra_certs != NULL) {
145 		issuer = X509_find_by_subject(extra_certs, issuer_name);
146 		if (issuer != NULL) {
147 			cid = OCSP_cert_to_id(NULL, main_cert, issuer);
148 			goto out;
149 		}
150 	}
151 
152 	if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
153 		goto out;
154 	if ((storectx = X509_STORE_CTX_new()) == NULL)
155 		goto out;
156 	if (X509_STORE_CTX_init(storectx, store, main_cert, extra_certs) != 1)
157 		goto out;
158 	if ((obj = X509_STORE_CTX_get_obj_by_subject(storectx, X509_LU_X509,
159 	    issuer_name)) == NULL)
160 		goto out;
161 
162 	cid = OCSP_cert_to_id(NULL, main_cert, X509_OBJECT_get0_X509(obj));
163 
164  out:
165 	X509_STORE_CTX_free(storectx);
166 	X509_OBJECT_free(obj);
167 
168 	return cid;
169 }
170 
171 struct tls_ocsp *
172 tls_ocsp_setup_from_peer(struct tls *ctx)
173 {
174 	struct tls_ocsp *ocsp = NULL;
175 	STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
176 
177 	if ((ocsp = tls_ocsp_new()) == NULL)
178 		goto err;
179 
180 	/* steal state from ctx struct */
181 	ocsp->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
182 	ocsp->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
183 	if (ocsp->main_cert == NULL) {
184 		tls_set_errorx(ctx, "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, "no OCSP URLs in peer certificate");
191 		goto err;
192 	}
193 
194 	ocsp->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
195 	if (ocsp->ocsp_url == NULL) {
196 		tls_set_errorx(ctx, "out of memory");
197 		goto err;
198 	}
199 
200 	X509_email_free(ocsp_urls);
201 	return ocsp;
202 
203  err:
204 	tls_ocsp_free(ocsp);
205 	X509_email_free(ocsp_urls);
206 	return NULL;
207 }
208 
209 static int
210 tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
211 {
212 	OCSP_BASICRESP *br = NULL;
213 	ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
214 	OCSP_CERTID *cid = NULL;
215 	STACK_OF(X509) *combined = NULL;
216 	int response_status=0, cert_status=0, crl_reason=0;
217 	int ret = -1;
218 	unsigned long flags;
219 
220 	if ((br = OCSP_response_get1_basic(resp)) == NULL) {
221 		tls_set_errorx(ctx, "cannot load ocsp reply");
222 		goto err;
223 	}
224 
225 	/*
226 	 * Skip validation of 'extra_certs' as this should be done
227 	 * already as part of main handshake.
228 	 */
229 	flags = OCSP_TRUSTOTHER;
230 
231 	/* now verify */
232 	if (OCSP_basic_verify(br, ctx->ocsp->extra_certs,
233 		SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
234 		tls_set_errorx(ctx, "ocsp verify failed");
235 		goto err;
236 	}
237 
238 	/* signature OK, look inside */
239 	response_status = OCSP_response_status(resp);
240 	if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
241 		tls_set_errorx(ctx, "ocsp verify failed: response - %s",
242 		    OCSP_response_status_str(response_status));
243 		goto err;
244 	}
245 
246 	cid = tls_ocsp_get_certid(ctx->ocsp->main_cert,
247 	    ctx->ocsp->extra_certs, ctx->ssl_ctx);
248 	if (cid == NULL) {
249 		tls_set_errorx(ctx, "ocsp verify failed: no issuer cert");
250 		goto err;
251 	}
252 
253 	if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
254 	    &revtime, &thisupd, &nextupd) != 1) {
255 		tls_set_errorx(ctx, "ocsp verify failed: no result for cert");
256 		goto err;
257 	}
258 
259 	if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
260 	    MAXAGE_SEC) != 1) {
261 		tls_set_errorx(ctx,
262 		    "ocsp verify failed: ocsp response not current");
263 		goto err;
264 	}
265 
266 	if (tls_ocsp_fill_info(ctx, response_status, cert_status,
267 	    crl_reason, revtime, thisupd, nextupd) != 0)
268 		goto err;
269 
270 	/* finally can look at status */
271 	if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
272 	    V_OCSP_CERTSTATUS_UNKNOWN) {
273 		tls_set_errorx(ctx, "ocsp verify failed: revoked cert - %s",
274 			       OCSP_crl_reason_str(crl_reason));
275 		goto err;
276 	}
277 	ret = 0;
278 
279  err:
280 	sk_X509_free(combined);
281 	OCSP_CERTID_free(cid);
282 	OCSP_BASICRESP_free(br);
283 	return ret;
284 }
285 
286 /*
287  * Process a raw OCSP response from an OCSP server request.
288  * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
289  * returns 0 if certificate ok, -1 otherwise.
290  */
291 static int
292 tls_ocsp_process_response_internal(struct tls *ctx, const unsigned char *response,
293     size_t size)
294 {
295 	int ret;
296 	OCSP_RESPONSE *resp;
297 
298 	resp = d2i_OCSP_RESPONSE(NULL, &response, size);
299 	if (resp == NULL) {
300 		tls_ocsp_free(ctx->ocsp);
301 		ctx->ocsp = NULL;
302 		tls_set_error(ctx, "unable to parse OCSP response");
303 		return -1;
304 	}
305 	ret = tls_ocsp_verify_response(ctx, resp);
306 	OCSP_RESPONSE_free(resp);
307 	return ret;
308 }
309 
310 /* TLS handshake verification callback for stapled requests */
311 int
312 tls_ocsp_verify_cb(SSL *ssl, void *arg)
313 {
314 	const unsigned char *raw = NULL;
315 	int size, res = -1;
316 	struct tls *ctx;
317 
318 	if ((ctx = SSL_get_app_data(ssl)) == NULL)
319 		return -1;
320 
321 	size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
322 	if (size <= 0) {
323 		if (ctx->config->ocsp_require_stapling) {
324 			tls_set_errorx(ctx, "no stapled OCSP response provided");
325 			return 0;
326 		}
327 		return 1;
328 	}
329 
330 	tls_ocsp_free(ctx->ocsp);
331 	if ((ctx->ocsp = tls_ocsp_setup_from_peer(ctx)) == NULL)
332 		return 0;
333 
334 	if (ctx->config->verify_cert == 0 || ctx->config->verify_time == 0)
335 		return 1;
336 
337 	res = tls_ocsp_process_response_internal(ctx, raw, size);
338 
339 	return (res == 0) ? 1 : 0;
340 }
341 
342 
343 /* Staple the OCSP information in ctx->ocsp to the server handshake. */
344 int
345 tls_ocsp_stapling_cb(SSL *ssl, void *arg)
346 {
347 	int ret = SSL_TLSEXT_ERR_ALERT_FATAL;
348 	unsigned char *ocsp_staple = NULL;
349 	struct tls *ctx;
350 
351 	if ((ctx = SSL_get_app_data(ssl)) == NULL)
352 		goto err;
353 
354 	if (ctx->keypair == NULL || ctx->keypair->ocsp_staple == NULL ||
355 	    ctx->keypair->ocsp_staple_len == 0)
356 		return SSL_TLSEXT_ERR_NOACK;
357 
358 	if ((ocsp_staple = malloc(ctx->keypair->ocsp_staple_len)) == NULL)
359 		goto err;
360 
361 	memcpy(ocsp_staple, ctx->keypair->ocsp_staple,
362 	    ctx->keypair->ocsp_staple_len);
363 
364 	if (SSL_set_tlsext_status_ocsp_resp(ctx->ssl_conn, ocsp_staple,
365 	    ctx->keypair->ocsp_staple_len) != 1)
366 		goto err;
367 
368 	ret = SSL_TLSEXT_ERR_OK;
369  err:
370 	if (ret != SSL_TLSEXT_ERR_OK)
371 		free(ocsp_staple);
372 
373 	return ret;
374 }
375 
376 /*
377  * Public API
378  */
379 
380 /* Retrieve OCSP URL from peer certificate, if present. */
381 const char *
382 tls_peer_ocsp_url(struct tls *ctx)
383 {
384 	if (ctx->ocsp == NULL)
385 		return NULL;
386 	return ctx->ocsp->ocsp_url;
387 }
388 
389 const char *
390 tls_peer_ocsp_result(struct tls *ctx)
391 {
392 	if (ctx->ocsp == NULL)
393 		return NULL;
394 	if (ctx->ocsp->ocsp_result == NULL)
395 		return NULL;
396 	return ctx->ocsp->ocsp_result->result_msg;
397 }
398 
399 int
400 tls_peer_ocsp_response_status(struct tls *ctx)
401 {
402 	if (ctx->ocsp == NULL)
403 		return -1;
404 	if (ctx->ocsp->ocsp_result == NULL)
405 		return -1;
406 	return ctx->ocsp->ocsp_result->response_status;
407 }
408 
409 int
410 tls_peer_ocsp_cert_status(struct tls *ctx)
411 {
412 	if (ctx->ocsp == NULL)
413 		return -1;
414 	if (ctx->ocsp->ocsp_result == NULL)
415 		return -1;
416 	return ctx->ocsp->ocsp_result->cert_status;
417 }
418 
419 int
420 tls_peer_ocsp_crl_reason(struct tls *ctx)
421 {
422 	if (ctx->ocsp == NULL)
423 		return -1;
424 	if (ctx->ocsp->ocsp_result == NULL)
425 		return -1;
426 	return ctx->ocsp->ocsp_result->crl_reason;
427 }
428 
429 time_t
430 tls_peer_ocsp_this_update(struct tls *ctx)
431 {
432 	if (ctx->ocsp == NULL)
433 		return -1;
434 	if (ctx->ocsp->ocsp_result == NULL)
435 		return -1;
436 	return ctx->ocsp->ocsp_result->this_update;
437 }
438 
439 time_t
440 tls_peer_ocsp_next_update(struct tls *ctx)
441 {
442 	if (ctx->ocsp == NULL)
443 		return -1;
444 	if (ctx->ocsp->ocsp_result == NULL)
445 		return -1;
446 	return ctx->ocsp->ocsp_result->next_update;
447 }
448 
449 time_t
450 tls_peer_ocsp_revocation_time(struct tls *ctx)
451 {
452 	if (ctx->ocsp == NULL)
453 		return -1;
454 	if (ctx->ocsp->ocsp_result == NULL)
455 		return -1;
456 	return ctx->ocsp->ocsp_result->revocation_time;
457 }
458 
459 int
460 tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
461     size_t size)
462 {
463 	if ((ctx->state & TLS_HANDSHAKE_COMPLETE) == 0)
464 		return -1;
465 	return tls_ocsp_process_response_internal(ctx, response, size);
466 }