xref: /openbsd/lib/libtls/tls_ocsp.c (revision 905646f0) 
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 *
39 tls_ocsp_new(void)
40 {
41 	return (calloc(1, sizeof(struct tls_ocsp)));
42 }
43 
44 void
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
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
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 *
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 *
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
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
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
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
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 *
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 *
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
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
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
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
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
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
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
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