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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Verify the signature on a PKCS#7 message.
3 *
4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#define pr_fmt(fmt) "PKCS7: "fmt
9#include <linux/kernel.h>
10#include <linux/export.h>
11#include <linux/slab.h>
12#include <linux/err.h>
13#include <linux/asn1.h>
14#include <crypto/hash.h>
15#include <crypto/hash_info.h>
16#include <crypto/public_key.h>
17#include "pkcs7_parser.h"
18
19/*
20 * Digest the relevant parts of the PKCS#7 data
21 */
22static int pkcs7_digest(struct pkcs7_message *pkcs7,
23 struct pkcs7_signed_info *sinfo)
24{
25 struct public_key_signature *sig = sinfo->sig;
26 struct crypto_shash *tfm;
27 struct shash_desc *desc;
28 size_t desc_size;
29 int ret;
30
31 kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo);
32
33 /* The digest was calculated already. */
34 if (sig->digest)
35 return 0;
36
37 if (!sinfo->sig->hash_algo)
38 return -ENOPKG;
39
40 /* Allocate the hashing algorithm we're going to need and find out how
41 * big the hash operational data will be.
42 */
43 tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0);
44 if (IS_ERR(tfm))
45 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
46
47 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
48 sig->digest_size = crypto_shash_digestsize(tfm);
49
50 ret = -ENOMEM;
51 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
52 if (!sig->digest)
53 goto error_no_desc;
54
55 desc = kzalloc(desc_size, GFP_KERNEL);
56 if (!desc)
57 goto error_no_desc;
58
59 desc->tfm = tfm;
60
61 /* Digest the message [RFC2315 9.3] */
62 ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len,
63 sig->digest);
64 if (ret < 0)
65 goto error;
66 pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest);
67
68 /* However, if there are authenticated attributes, there must be a
69 * message digest attribute amongst them which corresponds to the
70 * digest we just calculated.
71 */
72 if (sinfo->authattrs) {
73 u8 tag;
74
75 if (!sinfo->msgdigest) {
76 pr_warn("Sig %u: No messageDigest\n", sinfo->index);
77 ret = -EKEYREJECTED;
78 goto error;
79 }
80
81 if (sinfo->msgdigest_len != sig->digest_size) {
82 pr_debug("Sig %u: Invalid digest size (%u)\n",
83 sinfo->index, sinfo->msgdigest_len);
84 ret = -EBADMSG;
85 goto error;
86 }
87
88 if (memcmp(sig->digest, sinfo->msgdigest,
89 sinfo->msgdigest_len) != 0) {
90 pr_debug("Sig %u: Message digest doesn't match\n",
91 sinfo->index);
92 ret = -EKEYREJECTED;
93 goto error;
94 }
95
96 /* We then calculate anew, using the authenticated attributes
97 * as the contents of the digest instead. Note that we need to
98 * convert the attributes from a CONT.0 into a SET before we
99 * hash it.
100 */
101 memset(sig->digest, 0, sig->digest_size);
102
103 ret = crypto_shash_init(desc);
104 if (ret < 0)
105 goto error;
106 tag = ASN1_CONS_BIT | ASN1_SET;
107 ret = crypto_shash_update(desc, &tag, 1);
108 if (ret < 0)
109 goto error;
110 ret = crypto_shash_finup(desc, sinfo->authattrs,
111 sinfo->authattrs_len, sig->digest);
112 if (ret < 0)
113 goto error;
114 pr_devel("AADigest = [%*ph]\n", 8, sig->digest);
115 }
116
117error:
118 kfree(desc);
119error_no_desc:
120 crypto_free_shash(tfm);
121 kleave(" = %d", ret);
122 return ret;
123}
124
125int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len,
126 enum hash_algo *hash_algo)
127{
128 struct pkcs7_signed_info *sinfo = pkcs7->signed_infos;
129 int i, ret;
130
131 /*
132 * This function doesn't support messages with more than one signature.
133 */
134 if (sinfo == NULL || sinfo->next != NULL)
135 return -EBADMSG;
136
137 ret = pkcs7_digest(pkcs7, sinfo);
138 if (ret)
139 return ret;
140
141 *buf = sinfo->sig->digest;
142 *len = sinfo->sig->digest_size;
143
144 for (i = 0; i < HASH_ALGO__LAST; i++)
145 if (!strcmp(hash_algo_name[i], sinfo->sig->hash_algo)) {
146 *hash_algo = i;
147 break;
148 }
149
150 return 0;
151}
152
153/*
154 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
155 * uses the issuer's name and the issuing certificate serial number for
156 * matching purposes. These must match the certificate issuer's name (not
157 * subject's name) and the certificate serial number [RFC 2315 6.7].
158 */
159static int pkcs7_find_key(struct pkcs7_message *pkcs7,
160 struct pkcs7_signed_info *sinfo)
161{
162 struct x509_certificate *x509;
163 unsigned certix = 1;
164
165 kenter("%u", sinfo->index);
166
167 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
168 /* I'm _assuming_ that the generator of the PKCS#7 message will
169 * encode the fields from the X.509 cert in the same way in the
170 * PKCS#7 message - but I can't be 100% sure of that. It's
171 * possible this will need element-by-element comparison.
172 */
173 if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0]))
174 continue;
175 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
176 sinfo->index, certix);
177
178 if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) {
179 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
180 sinfo->index);
181 continue;
182 }
183
184 sinfo->signer = x509;
185 return 0;
186 }
187
188 /* The relevant X.509 cert isn't found here, but it might be found in
189 * the trust keyring.
190 */
191 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
192 sinfo->index,
193 sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data);
194 return 0;
195}
196
197/*
198 * Verify the internal certificate chain as best we can.
199 */
200static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
201 struct pkcs7_signed_info *sinfo)
202{
203 struct public_key_signature *sig;
204 struct x509_certificate *x509 = sinfo->signer, *p;
205 struct asymmetric_key_id *auth;
206 int ret;
207
208 kenter("");
209
210 for (p = pkcs7->certs; p; p = p->next)
211 p->seen = false;
212
213 for (;;) {
214 pr_debug("verify %s: %*phN\n",
215 x509->subject,
216 x509->raw_serial_size, x509->raw_serial);
217 x509->seen = true;
218
219 if (x509->blacklisted) {
220 /* If this cert is blacklisted, then mark everything
221 * that depends on this as blacklisted too.
222 */
223 sinfo->blacklisted = true;
224 for (p = sinfo->signer; p != x509; p = p->signer)
225 p->blacklisted = true;
226 pr_debug("- blacklisted\n");
227 return 0;
228 }
229
230 if (x509->unsupported_key)
231 goto unsupported_crypto_in_x509;
232
233 pr_debug("- issuer %s\n", x509->issuer);
234 sig = x509->sig;
235 if (sig->auth_ids[0])
236 pr_debug("- authkeyid.id %*phN\n",
237 sig->auth_ids[0]->len, sig->auth_ids[0]->data);
238 if (sig->auth_ids[1])
239 pr_debug("- authkeyid.skid %*phN\n",
240 sig->auth_ids[1]->len, sig->auth_ids[1]->data);
241
242 if (x509->self_signed) {
243 /* If there's no authority certificate specified, then
244 * the certificate must be self-signed and is the root
245 * of the chain. Likewise if the cert is its own
246 * authority.
247 */
248 if (x509->unsupported_sig)
249 goto unsupported_crypto_in_x509;
250 x509->signer = x509;
251 pr_debug("- self-signed\n");
252 return 0;
253 }
254
255 /* Look through the X.509 certificates in the PKCS#7 message's
256 * list to see if the next one is there.
257 */
258 auth = sig->auth_ids[0];
259 if (auth) {
260 pr_debug("- want %*phN\n", auth->len, auth->data);
261 for (p = pkcs7->certs; p; p = p->next) {
262 pr_debug("- cmp [%u] %*phN\n",
263 p->index, p->id->len, p->id->data);
264 if (asymmetric_key_id_same(p->id, auth))
265 goto found_issuer_check_skid;
266 }
267 } else if (sig->auth_ids[1]) {
268 auth = sig->auth_ids[1];
269 pr_debug("- want %*phN\n", auth->len, auth->data);
270 for (p = pkcs7->certs; p; p = p->next) {
271 if (!p->skid)
272 continue;
273 pr_debug("- cmp [%u] %*phN\n",
274 p->index, p->skid->len, p->skid->data);
275 if (asymmetric_key_id_same(p->skid, auth))
276 goto found_issuer;
277 }
278 }
279
280 /* We didn't find the root of this chain */
281 pr_debug("- top\n");
282 return 0;
283
284 found_issuer_check_skid:
285 /* We matched issuer + serialNumber, but if there's an
286 * authKeyId.keyId, that must match the CA subjKeyId also.
287 */
288 if (sig->auth_ids[1] &&
289 !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
290 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
291 sinfo->index, x509->index, p->index);
292 return -EKEYREJECTED;
293 }
294 found_issuer:
295 pr_debug("- subject %s\n", p->subject);
296 if (p->seen) {
297 pr_warn("Sig %u: X.509 chain contains loop\n",
298 sinfo->index);
299 return 0;
300 }
301 ret = public_key_verify_signature(p->pub, x509->sig);
302 if (ret < 0)
303 return ret;
304 x509->signer = p;
305 if (x509 == p) {
306 pr_debug("- self-signed\n");
307 return 0;
308 }
309 x509 = p;
310 might_sleep();
311 }
312
313unsupported_crypto_in_x509:
314 /* Just prune the certificate chain at this point if we lack some
315 * crypto module to go further. Note, however, we don't want to set
316 * sinfo->unsupported_crypto as the signed info block may still be
317 * validatable against an X.509 cert lower in the chain that we have a
318 * trusted copy of.
319 */
320 return 0;
321}
322
323/*
324 * Verify one signed information block from a PKCS#7 message.
325 */
326static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
327 struct pkcs7_signed_info *sinfo)
328{
329 int ret;
330
331 kenter(",%u", sinfo->index);
332
333 /* First of all, digest the data in the PKCS#7 message and the
334 * signed information block
335 */
336 ret = pkcs7_digest(pkcs7, sinfo);
337 if (ret < 0)
338 return ret;
339
340 /* Find the key for the signature if there is one */
341 ret = pkcs7_find_key(pkcs7, sinfo);
342 if (ret < 0)
343 return ret;
344
345 if (!sinfo->signer)
346 return 0;
347
348 pr_devel("Using X.509[%u] for sig %u\n",
349 sinfo->signer->index, sinfo->index);
350
351 /* Check that the PKCS#7 signing time is valid according to the X.509
352 * certificate. We can't, however, check against the system clock
353 * since that may not have been set yet and may be wrong.
354 */
355 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
356 if (sinfo->signing_time < sinfo->signer->valid_from ||
357 sinfo->signing_time > sinfo->signer->valid_to) {
358 pr_warn("Message signed outside of X.509 validity window\n");
359 return -EKEYREJECTED;
360 }
361 }
362
363 /* Verify the PKCS#7 binary against the key */
364 ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig);
365 if (ret < 0)
366 return ret;
367
368 pr_devel("Verified signature %u\n", sinfo->index);
369
370 /* Verify the internal certificate chain */
371 return pkcs7_verify_sig_chain(pkcs7, sinfo);
372}
373
374/**
375 * pkcs7_verify - Verify a PKCS#7 message
376 * @pkcs7: The PKCS#7 message to be verified
377 * @usage: The use to which the key is being put
378 *
379 * Verify a PKCS#7 message is internally consistent - that is, the data digest
380 * matches the digest in the AuthAttrs and any signature in the message or one
381 * of the X.509 certificates it carries that matches another X.509 cert in the
382 * message can be verified.
383 *
384 * This does not look to match the contents of the PKCS#7 message against any
385 * external public keys.
386 *
387 * Returns, in order of descending priority:
388 *
389 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
390 * odds with the specified usage, or:
391 *
392 * (*) -EKEYREJECTED if a signature failed to match for which we found an
393 * appropriate X.509 certificate, or:
394 *
395 * (*) -EBADMSG if some part of the message was invalid, or:
396 *
397 * (*) 0 if a signature chain passed verification, or:
398 *
399 * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
400 *
401 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
402 * crypto modules couldn't be found.
403 */
404int pkcs7_verify(struct pkcs7_message *pkcs7,
405 enum key_being_used_for usage)
406{
407 struct pkcs7_signed_info *sinfo;
408 int actual_ret = -ENOPKG;
409 int ret;
410
411 kenter("");
412
413 switch (usage) {
414 case VERIFYING_MODULE_SIGNATURE:
415 if (pkcs7->data_type != OID_data) {
416 pr_warn("Invalid module sig (not pkcs7-data)\n");
417 return -EKEYREJECTED;
418 }
419 if (pkcs7->have_authattrs) {
420 pr_warn("Invalid module sig (has authattrs)\n");
421 return -EKEYREJECTED;
422 }
423 break;
424 case VERIFYING_FIRMWARE_SIGNATURE:
425 if (pkcs7->data_type != OID_data) {
426 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
427 return -EKEYREJECTED;
428 }
429 if (!pkcs7->have_authattrs) {
430 pr_warn("Invalid firmware sig (missing authattrs)\n");
431 return -EKEYREJECTED;
432 }
433 break;
434 case VERIFYING_KEXEC_PE_SIGNATURE:
435 if (pkcs7->data_type != OID_msIndirectData) {
436 pr_warn("Invalid kexec sig (not Authenticode)\n");
437 return -EKEYREJECTED;
438 }
439 /* Authattr presence checked in parser */
440 break;
441 case VERIFYING_UNSPECIFIED_SIGNATURE:
442 if (pkcs7->data_type != OID_data) {
443 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
444 return -EKEYREJECTED;
445 }
446 break;
447 default:
448 return -EINVAL;
449 }
450
451 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
452 ret = pkcs7_verify_one(pkcs7, sinfo);
453 if (sinfo->blacklisted) {
454 if (actual_ret == -ENOPKG)
455 actual_ret = -EKEYREJECTED;
456 continue;
457 }
458 if (ret < 0) {
459 if (ret == -ENOPKG) {
460 sinfo->unsupported_crypto = true;
461 continue;
462 }
463 kleave(" = %d", ret);
464 return ret;
465 }
466 actual_ret = 0;
467 }
468
469 kleave(" = %d", actual_ret);
470 return actual_ret;
471}
472EXPORT_SYMBOL_GPL(pkcs7_verify);
473
474/**
475 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
476 * @pkcs7: The PKCS#7 message
477 * @data: The data to be verified
478 * @datalen: The amount of data
479 *
480 * Supply the detached data needed to verify a PKCS#7 message. Note that no
481 * attempt to retain/pin the data is made. That is left to the caller. The
482 * data will not be modified by pkcs7_verify() and will not be freed when the
483 * PKCS#7 message is freed.
484 *
485 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
486 */
487int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
488 const void *data, size_t datalen)
489{
490 if (pkcs7->data) {
491 pr_debug("Data already supplied\n");
492 return -EINVAL;
493 }
494 pkcs7->data = data;
495 pkcs7->data_len = datalen;
496 return 0;
497}
1/* Verify the signature on a PKCS#7 message.
2 *
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#define pr_fmt(fmt) "PKCS7: "fmt
13#include <linux/kernel.h>
14#include <linux/export.h>
15#include <linux/slab.h>
16#include <linux/err.h>
17#include <linux/asn1.h>
18#include <crypto/hash.h>
19#include <crypto/public_key.h>
20#include "pkcs7_parser.h"
21
22/*
23 * Digest the relevant parts of the PKCS#7 data
24 */
25static int pkcs7_digest(struct pkcs7_message *pkcs7,
26 struct pkcs7_signed_info *sinfo)
27{
28 struct public_key_signature *sig = sinfo->sig;
29 struct crypto_shash *tfm;
30 struct shash_desc *desc;
31 size_t desc_size;
32 int ret;
33
34 kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo);
35
36 if (!sinfo->sig->hash_algo)
37 return -ENOPKG;
38
39 /* Allocate the hashing algorithm we're going to need and find out how
40 * big the hash operational data will be.
41 */
42 tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0);
43 if (IS_ERR(tfm))
44 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
45
46 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
47 sig->digest_size = crypto_shash_digestsize(tfm);
48
49 ret = -ENOMEM;
50 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
51 if (!sig->digest)
52 goto error_no_desc;
53
54 desc = kzalloc(desc_size, GFP_KERNEL);
55 if (!desc)
56 goto error_no_desc;
57
58 desc->tfm = tfm;
59 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
60
61 /* Digest the message [RFC2315 9.3] */
62 ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len,
63 sig->digest);
64 if (ret < 0)
65 goto error;
66 pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest);
67
68 /* However, if there are authenticated attributes, there must be a
69 * message digest attribute amongst them which corresponds to the
70 * digest we just calculated.
71 */
72 if (sinfo->authattrs) {
73 u8 tag;
74
75 if (!sinfo->msgdigest) {
76 pr_warn("Sig %u: No messageDigest\n", sinfo->index);
77 ret = -EKEYREJECTED;
78 goto error;
79 }
80
81 if (sinfo->msgdigest_len != sig->digest_size) {
82 pr_debug("Sig %u: Invalid digest size (%u)\n",
83 sinfo->index, sinfo->msgdigest_len);
84 ret = -EBADMSG;
85 goto error;
86 }
87
88 if (memcmp(sig->digest, sinfo->msgdigest,
89 sinfo->msgdigest_len) != 0) {
90 pr_debug("Sig %u: Message digest doesn't match\n",
91 sinfo->index);
92 ret = -EKEYREJECTED;
93 goto error;
94 }
95
96 /* We then calculate anew, using the authenticated attributes
97 * as the contents of the digest instead. Note that we need to
98 * convert the attributes from a CONT.0 into a SET before we
99 * hash it.
100 */
101 memset(sig->digest, 0, sig->digest_size);
102
103 ret = crypto_shash_init(desc);
104 if (ret < 0)
105 goto error;
106 tag = ASN1_CONS_BIT | ASN1_SET;
107 ret = crypto_shash_update(desc, &tag, 1);
108 if (ret < 0)
109 goto error;
110 ret = crypto_shash_finup(desc, sinfo->authattrs,
111 sinfo->authattrs_len, sig->digest);
112 if (ret < 0)
113 goto error;
114 pr_devel("AADigest = [%*ph]\n", 8, sig->digest);
115 }
116
117error:
118 kfree(desc);
119error_no_desc:
120 crypto_free_shash(tfm);
121 kleave(" = %d", ret);
122 return ret;
123}
124
125/*
126 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
127 * uses the issuer's name and the issuing certificate serial number for
128 * matching purposes. These must match the certificate issuer's name (not
129 * subject's name) and the certificate serial number [RFC 2315 6.7].
130 */
131static int pkcs7_find_key(struct pkcs7_message *pkcs7,
132 struct pkcs7_signed_info *sinfo)
133{
134 struct x509_certificate *x509;
135 unsigned certix = 1;
136
137 kenter("%u", sinfo->index);
138
139 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
140 /* I'm _assuming_ that the generator of the PKCS#7 message will
141 * encode the fields from the X.509 cert in the same way in the
142 * PKCS#7 message - but I can't be 100% sure of that. It's
143 * possible this will need element-by-element comparison.
144 */
145 if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0]))
146 continue;
147 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
148 sinfo->index, certix);
149
150 if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) {
151 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
152 sinfo->index);
153 continue;
154 }
155
156 sinfo->signer = x509;
157 return 0;
158 }
159
160 /* The relevant X.509 cert isn't found here, but it might be found in
161 * the trust keyring.
162 */
163 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
164 sinfo->index,
165 sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data);
166 return 0;
167}
168
169/*
170 * Verify the internal certificate chain as best we can.
171 */
172static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
173 struct pkcs7_signed_info *sinfo)
174{
175 struct public_key_signature *sig;
176 struct x509_certificate *x509 = sinfo->signer, *p;
177 struct asymmetric_key_id *auth;
178 int ret;
179
180 kenter("");
181
182 for (p = pkcs7->certs; p; p = p->next)
183 p->seen = false;
184
185 for (;;) {
186 pr_debug("verify %s: %*phN\n",
187 x509->subject,
188 x509->raw_serial_size, x509->raw_serial);
189 x509->seen = true;
190
191 if (x509->blacklisted) {
192 /* If this cert is blacklisted, then mark everything
193 * that depends on this as blacklisted too.
194 */
195 sinfo->blacklisted = true;
196 for (p = sinfo->signer; p != x509; p = p->signer)
197 p->blacklisted = true;
198 pr_debug("- blacklisted\n");
199 return 0;
200 }
201
202 if (x509->unsupported_key)
203 goto unsupported_crypto_in_x509;
204
205 pr_debug("- issuer %s\n", x509->issuer);
206 sig = x509->sig;
207 if (sig->auth_ids[0])
208 pr_debug("- authkeyid.id %*phN\n",
209 sig->auth_ids[0]->len, sig->auth_ids[0]->data);
210 if (sig->auth_ids[1])
211 pr_debug("- authkeyid.skid %*phN\n",
212 sig->auth_ids[1]->len, sig->auth_ids[1]->data);
213
214 if (x509->self_signed) {
215 /* If there's no authority certificate specified, then
216 * the certificate must be self-signed and is the root
217 * of the chain. Likewise if the cert is its own
218 * authority.
219 */
220 if (x509->unsupported_sig)
221 goto unsupported_crypto_in_x509;
222 x509->signer = x509;
223 pr_debug("- self-signed\n");
224 return 0;
225 }
226
227 /* Look through the X.509 certificates in the PKCS#7 message's
228 * list to see if the next one is there.
229 */
230 auth = sig->auth_ids[0];
231 if (auth) {
232 pr_debug("- want %*phN\n", auth->len, auth->data);
233 for (p = pkcs7->certs; p; p = p->next) {
234 pr_debug("- cmp [%u] %*phN\n",
235 p->index, p->id->len, p->id->data);
236 if (asymmetric_key_id_same(p->id, auth))
237 goto found_issuer_check_skid;
238 }
239 } else if (sig->auth_ids[1]) {
240 auth = sig->auth_ids[1];
241 pr_debug("- want %*phN\n", auth->len, auth->data);
242 for (p = pkcs7->certs; p; p = p->next) {
243 if (!p->skid)
244 continue;
245 pr_debug("- cmp [%u] %*phN\n",
246 p->index, p->skid->len, p->skid->data);
247 if (asymmetric_key_id_same(p->skid, auth))
248 goto found_issuer;
249 }
250 }
251
252 /* We didn't find the root of this chain */
253 pr_debug("- top\n");
254 return 0;
255
256 found_issuer_check_skid:
257 /* We matched issuer + serialNumber, but if there's an
258 * authKeyId.keyId, that must match the CA subjKeyId also.
259 */
260 if (sig->auth_ids[1] &&
261 !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
262 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
263 sinfo->index, x509->index, p->index);
264 return -EKEYREJECTED;
265 }
266 found_issuer:
267 pr_debug("- subject %s\n", p->subject);
268 if (p->seen) {
269 pr_warn("Sig %u: X.509 chain contains loop\n",
270 sinfo->index);
271 return 0;
272 }
273 ret = public_key_verify_signature(p->pub, x509->sig);
274 if (ret < 0)
275 return ret;
276 x509->signer = p;
277 if (x509 == p) {
278 pr_debug("- self-signed\n");
279 return 0;
280 }
281 x509 = p;
282 might_sleep();
283 }
284
285unsupported_crypto_in_x509:
286 /* Just prune the certificate chain at this point if we lack some
287 * crypto module to go further. Note, however, we don't want to set
288 * sinfo->unsupported_crypto as the signed info block may still be
289 * validatable against an X.509 cert lower in the chain that we have a
290 * trusted copy of.
291 */
292 return 0;
293}
294
295/*
296 * Verify one signed information block from a PKCS#7 message.
297 */
298static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
299 struct pkcs7_signed_info *sinfo)
300{
301 int ret;
302
303 kenter(",%u", sinfo->index);
304
305 /* First of all, digest the data in the PKCS#7 message and the
306 * signed information block
307 */
308 ret = pkcs7_digest(pkcs7, sinfo);
309 if (ret < 0)
310 return ret;
311
312 /* Find the key for the signature if there is one */
313 ret = pkcs7_find_key(pkcs7, sinfo);
314 if (ret < 0)
315 return ret;
316
317 if (!sinfo->signer)
318 return 0;
319
320 pr_devel("Using X.509[%u] for sig %u\n",
321 sinfo->signer->index, sinfo->index);
322
323 /* Check that the PKCS#7 signing time is valid according to the X.509
324 * certificate. We can't, however, check against the system clock
325 * since that may not have been set yet and may be wrong.
326 */
327 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
328 if (sinfo->signing_time < sinfo->signer->valid_from ||
329 sinfo->signing_time > sinfo->signer->valid_to) {
330 pr_warn("Message signed outside of X.509 validity window\n");
331 return -EKEYREJECTED;
332 }
333 }
334
335 /* Verify the PKCS#7 binary against the key */
336 ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig);
337 if (ret < 0)
338 return ret;
339
340 pr_devel("Verified signature %u\n", sinfo->index);
341
342 /* Verify the internal certificate chain */
343 return pkcs7_verify_sig_chain(pkcs7, sinfo);
344}
345
346/**
347 * pkcs7_verify - Verify a PKCS#7 message
348 * @pkcs7: The PKCS#7 message to be verified
349 * @usage: The use to which the key is being put
350 *
351 * Verify a PKCS#7 message is internally consistent - that is, the data digest
352 * matches the digest in the AuthAttrs and any signature in the message or one
353 * of the X.509 certificates it carries that matches another X.509 cert in the
354 * message can be verified.
355 *
356 * This does not look to match the contents of the PKCS#7 message against any
357 * external public keys.
358 *
359 * Returns, in order of descending priority:
360 *
361 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
362 * odds with the specified usage, or:
363 *
364 * (*) -EKEYREJECTED if a signature failed to match for which we found an
365 * appropriate X.509 certificate, or:
366 *
367 * (*) -EBADMSG if some part of the message was invalid, or:
368 *
369 * (*) 0 if a signature chain passed verification, or:
370 *
371 * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
372 *
373 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
374 * crypto modules couldn't be found.
375 */
376int pkcs7_verify(struct pkcs7_message *pkcs7,
377 enum key_being_used_for usage)
378{
379 struct pkcs7_signed_info *sinfo;
380 int actual_ret = -ENOPKG;
381 int ret;
382
383 kenter("");
384
385 switch (usage) {
386 case VERIFYING_MODULE_SIGNATURE:
387 if (pkcs7->data_type != OID_data) {
388 pr_warn("Invalid module sig (not pkcs7-data)\n");
389 return -EKEYREJECTED;
390 }
391 if (pkcs7->have_authattrs) {
392 pr_warn("Invalid module sig (has authattrs)\n");
393 return -EKEYREJECTED;
394 }
395 break;
396 case VERIFYING_FIRMWARE_SIGNATURE:
397 if (pkcs7->data_type != OID_data) {
398 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
399 return -EKEYREJECTED;
400 }
401 if (!pkcs7->have_authattrs) {
402 pr_warn("Invalid firmware sig (missing authattrs)\n");
403 return -EKEYREJECTED;
404 }
405 break;
406 case VERIFYING_KEXEC_PE_SIGNATURE:
407 if (pkcs7->data_type != OID_msIndirectData) {
408 pr_warn("Invalid kexec sig (not Authenticode)\n");
409 return -EKEYREJECTED;
410 }
411 /* Authattr presence checked in parser */
412 break;
413 case VERIFYING_UNSPECIFIED_SIGNATURE:
414 if (pkcs7->data_type != OID_data) {
415 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
416 return -EKEYREJECTED;
417 }
418 break;
419 default:
420 return -EINVAL;
421 }
422
423 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
424 ret = pkcs7_verify_one(pkcs7, sinfo);
425 if (sinfo->blacklisted) {
426 if (actual_ret == -ENOPKG)
427 actual_ret = -EKEYREJECTED;
428 continue;
429 }
430 if (ret < 0) {
431 if (ret == -ENOPKG) {
432 sinfo->unsupported_crypto = true;
433 continue;
434 }
435 kleave(" = %d", ret);
436 return ret;
437 }
438 actual_ret = 0;
439 }
440
441 kleave(" = %d", actual_ret);
442 return actual_ret;
443}
444EXPORT_SYMBOL_GPL(pkcs7_verify);
445
446/**
447 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
448 * @pkcs7: The PKCS#7 message
449 * @data: The data to be verified
450 * @datalen: The amount of data
451 *
452 * Supply the detached data needed to verify a PKCS#7 message. Note that no
453 * attempt to retain/pin the data is made. That is left to the caller. The
454 * data will not be modified by pkcs7_verify() and will not be freed when the
455 * PKCS#7 message is freed.
456 *
457 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
458 */
459int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
460 const void *data, size_t datalen)
461{
462 if (pkcs7->data) {
463 pr_debug("Data already supplied\n");
464 return -EINVAL;
465 }
466 pkcs7->data = data;
467 pkcs7->data_len = datalen;
468 return 0;
469}