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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 i = match_string(hash_algo_name, HASH_ALGO__LAST,
145 sinfo->sig->hash_algo);
146 if (i >= 0)
147 *hash_algo = i;
148
149 return 0;
150}
151
152/*
153 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
154 * uses the issuer's name and the issuing certificate serial number for
155 * matching purposes. These must match the certificate issuer's name (not
156 * subject's name) and the certificate serial number [RFC 2315 6.7].
157 */
158static int pkcs7_find_key(struct pkcs7_message *pkcs7,
159 struct pkcs7_signed_info *sinfo)
160{
161 struct x509_certificate *x509;
162 unsigned certix = 1;
163
164 kenter("%u", sinfo->index);
165
166 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
167 /* I'm _assuming_ that the generator of the PKCS#7 message will
168 * encode the fields from the X.509 cert in the same way in the
169 * PKCS#7 message - but I can't be 100% sure of that. It's
170 * possible this will need element-by-element comparison.
171 */
172 if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0]))
173 continue;
174 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
175 sinfo->index, certix);
176
177 sinfo->signer = x509;
178 return 0;
179 }
180
181 /* The relevant X.509 cert isn't found here, but it might be found in
182 * the trust keyring.
183 */
184 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
185 sinfo->index,
186 sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data);
187 return 0;
188}
189
190/*
191 * Verify the internal certificate chain as best we can.
192 */
193static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
194 struct pkcs7_signed_info *sinfo)
195{
196 struct public_key_signature *sig;
197 struct x509_certificate *x509 = sinfo->signer, *p;
198 struct asymmetric_key_id *auth;
199 int ret;
200
201 kenter("");
202
203 for (p = pkcs7->certs; p; p = p->next)
204 p->seen = false;
205
206 for (;;) {
207 pr_debug("verify %s: %*phN\n",
208 x509->subject,
209 x509->raw_serial_size, x509->raw_serial);
210 x509->seen = true;
211
212 if (x509->blacklisted) {
213 /* If this cert is blacklisted, then mark everything
214 * that depends on this as blacklisted too.
215 */
216 sinfo->blacklisted = true;
217 for (p = sinfo->signer; p != x509; p = p->signer)
218 p->blacklisted = true;
219 pr_debug("- blacklisted\n");
220 return 0;
221 }
222
223 pr_debug("- issuer %s\n", x509->issuer);
224 sig = x509->sig;
225 if (sig->auth_ids[0])
226 pr_debug("- authkeyid.id %*phN\n",
227 sig->auth_ids[0]->len, sig->auth_ids[0]->data);
228 if (sig->auth_ids[1])
229 pr_debug("- authkeyid.skid %*phN\n",
230 sig->auth_ids[1]->len, sig->auth_ids[1]->data);
231
232 if (x509->self_signed) {
233 /* If there's no authority certificate specified, then
234 * the certificate must be self-signed and is the root
235 * of the chain. Likewise if the cert is its own
236 * authority.
237 */
238 if (x509->unsupported_sig)
239 goto unsupported_sig_in_x509;
240 x509->signer = x509;
241 pr_debug("- self-signed\n");
242 return 0;
243 }
244
245 /* Look through the X.509 certificates in the PKCS#7 message's
246 * list to see if the next one is there.
247 */
248 auth = sig->auth_ids[0];
249 if (auth) {
250 pr_debug("- want %*phN\n", auth->len, auth->data);
251 for (p = pkcs7->certs; p; p = p->next) {
252 pr_debug("- cmp [%u] %*phN\n",
253 p->index, p->id->len, p->id->data);
254 if (asymmetric_key_id_same(p->id, auth))
255 goto found_issuer_check_skid;
256 }
257 } else if (sig->auth_ids[1]) {
258 auth = sig->auth_ids[1];
259 pr_debug("- want %*phN\n", auth->len, auth->data);
260 for (p = pkcs7->certs; p; p = p->next) {
261 if (!p->skid)
262 continue;
263 pr_debug("- cmp [%u] %*phN\n",
264 p->index, p->skid->len, p->skid->data);
265 if (asymmetric_key_id_same(p->skid, auth))
266 goto found_issuer;
267 }
268 }
269
270 /* We didn't find the root of this chain */
271 pr_debug("- top\n");
272 return 0;
273
274 found_issuer_check_skid:
275 /* We matched issuer + serialNumber, but if there's an
276 * authKeyId.keyId, that must match the CA subjKeyId also.
277 */
278 if (sig->auth_ids[1] &&
279 !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
280 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
281 sinfo->index, x509->index, p->index);
282 return -EKEYREJECTED;
283 }
284 found_issuer:
285 pr_debug("- subject %s\n", p->subject);
286 if (p->seen) {
287 pr_warn("Sig %u: X.509 chain contains loop\n",
288 sinfo->index);
289 return 0;
290 }
291 ret = public_key_verify_signature(p->pub, x509->sig);
292 if (ret < 0)
293 return ret;
294 x509->signer = p;
295 if (x509 == p) {
296 pr_debug("- self-signed\n");
297 return 0;
298 }
299 x509 = p;
300 might_sleep();
301 }
302
303unsupported_sig_in_x509:
304 /* Just prune the certificate chain at this point if we lack some
305 * crypto module to go further. Note, however, we don't want to set
306 * sinfo->unsupported_crypto as the signed info block may still be
307 * validatable against an X.509 cert lower in the chain that we have a
308 * trusted copy of.
309 */
310 return 0;
311}
312
313/*
314 * Verify one signed information block from a PKCS#7 message.
315 */
316static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
317 struct pkcs7_signed_info *sinfo)
318{
319 int ret;
320
321 kenter(",%u", sinfo->index);
322
323 /* First of all, digest the data in the PKCS#7 message and the
324 * signed information block
325 */
326 ret = pkcs7_digest(pkcs7, sinfo);
327 if (ret < 0)
328 return ret;
329
330 /* Find the key for the signature if there is one */
331 ret = pkcs7_find_key(pkcs7, sinfo);
332 if (ret < 0)
333 return ret;
334
335 if (!sinfo->signer)
336 return 0;
337
338 pr_devel("Using X.509[%u] for sig %u\n",
339 sinfo->signer->index, sinfo->index);
340
341 /* Check that the PKCS#7 signing time is valid according to the X.509
342 * certificate. We can't, however, check against the system clock
343 * since that may not have been set yet and may be wrong.
344 */
345 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
346 if (sinfo->signing_time < sinfo->signer->valid_from ||
347 sinfo->signing_time > sinfo->signer->valid_to) {
348 pr_warn("Message signed outside of X.509 validity window\n");
349 return -EKEYREJECTED;
350 }
351 }
352
353 /* Verify the PKCS#7 binary against the key */
354 ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig);
355 if (ret < 0)
356 return ret;
357
358 pr_devel("Verified signature %u\n", sinfo->index);
359
360 /* Verify the internal certificate chain */
361 return pkcs7_verify_sig_chain(pkcs7, sinfo);
362}
363
364/**
365 * pkcs7_verify - Verify a PKCS#7 message
366 * @pkcs7: The PKCS#7 message to be verified
367 * @usage: The use to which the key is being put
368 *
369 * Verify a PKCS#7 message is internally consistent - that is, the data digest
370 * matches the digest in the AuthAttrs and any signature in the message or one
371 * of the X.509 certificates it carries that matches another X.509 cert in the
372 * message can be verified.
373 *
374 * This does not look to match the contents of the PKCS#7 message against any
375 * external public keys.
376 *
377 * Returns, in order of descending priority:
378 *
379 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
380 * odds with the specified usage, or:
381 *
382 * (*) -EKEYREJECTED if a signature failed to match for which we found an
383 * appropriate X.509 certificate, or:
384 *
385 * (*) -EBADMSG if some part of the message was invalid, or:
386 *
387 * (*) 0 if a signature chain passed verification, or:
388 *
389 * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
390 *
391 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
392 * crypto modules couldn't be found.
393 */
394int pkcs7_verify(struct pkcs7_message *pkcs7,
395 enum key_being_used_for usage)
396{
397 struct pkcs7_signed_info *sinfo;
398 int actual_ret = -ENOPKG;
399 int ret;
400
401 kenter("");
402
403 switch (usage) {
404 case VERIFYING_MODULE_SIGNATURE:
405 if (pkcs7->data_type != OID_data) {
406 pr_warn("Invalid module sig (not pkcs7-data)\n");
407 return -EKEYREJECTED;
408 }
409 if (pkcs7->have_authattrs) {
410 pr_warn("Invalid module sig (has authattrs)\n");
411 return -EKEYREJECTED;
412 }
413 break;
414 case VERIFYING_FIRMWARE_SIGNATURE:
415 if (pkcs7->data_type != OID_data) {
416 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
417 return -EKEYREJECTED;
418 }
419 if (!pkcs7->have_authattrs) {
420 pr_warn("Invalid firmware sig (missing authattrs)\n");
421 return -EKEYREJECTED;
422 }
423 break;
424 case VERIFYING_KEXEC_PE_SIGNATURE:
425 if (pkcs7->data_type != OID_msIndirectData) {
426 pr_warn("Invalid kexec sig (not Authenticode)\n");
427 return -EKEYREJECTED;
428 }
429 /* Authattr presence checked in parser */
430 break;
431 case VERIFYING_UNSPECIFIED_SIGNATURE:
432 if (pkcs7->data_type != OID_data) {
433 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
434 return -EKEYREJECTED;
435 }
436 break;
437 default:
438 return -EINVAL;
439 }
440
441 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
442 ret = pkcs7_verify_one(pkcs7, sinfo);
443 if (sinfo->blacklisted) {
444 if (actual_ret == -ENOPKG)
445 actual_ret = -EKEYREJECTED;
446 continue;
447 }
448 if (ret < 0) {
449 if (ret == -ENOPKG) {
450 sinfo->unsupported_crypto = true;
451 continue;
452 }
453 kleave(" = %d", ret);
454 return ret;
455 }
456 actual_ret = 0;
457 }
458
459 kleave(" = %d", actual_ret);
460 return actual_ret;
461}
462EXPORT_SYMBOL_GPL(pkcs7_verify);
463
464/**
465 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
466 * @pkcs7: The PKCS#7 message
467 * @data: The data to be verified
468 * @datalen: The amount of data
469 *
470 * Supply the detached data needed to verify a PKCS#7 message. Note that no
471 * attempt to retain/pin the data is made. That is left to the caller. The
472 * data will not be modified by pkcs7_verify() and will not be freed when the
473 * PKCS#7 message is freed.
474 *
475 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
476 */
477int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
478 const void *data, size_t datalen)
479{
480 if (pkcs7->data) {
481 pr_debug("Data already supplied\n");
482 return -EINVAL;
483 }
484 pkcs7->data = data;
485 pkcs7->data_len = datalen;
486 return 0;
487}
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_init(desc);
63 if (ret < 0)
64 goto error;
65 ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len,
66 sig->digest);
67 if (ret < 0)
68 goto error;
69 pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest);
70
71 /* However, if there are authenticated attributes, there must be a
72 * message digest attribute amongst them which corresponds to the
73 * digest we just calculated.
74 */
75 if (sinfo->authattrs) {
76 u8 tag;
77
78 if (!sinfo->msgdigest) {
79 pr_warn("Sig %u: No messageDigest\n", sinfo->index);
80 ret = -EKEYREJECTED;
81 goto error;
82 }
83
84 if (sinfo->msgdigest_len != sig->digest_size) {
85 pr_debug("Sig %u: Invalid digest size (%u)\n",
86 sinfo->index, sinfo->msgdigest_len);
87 ret = -EBADMSG;
88 goto error;
89 }
90
91 if (memcmp(sig->digest, sinfo->msgdigest,
92 sinfo->msgdigest_len) != 0) {
93 pr_debug("Sig %u: Message digest doesn't match\n",
94 sinfo->index);
95 ret = -EKEYREJECTED;
96 goto error;
97 }
98
99 /* We then calculate anew, using the authenticated attributes
100 * as the contents of the digest instead. Note that we need to
101 * convert the attributes from a CONT.0 into a SET before we
102 * hash it.
103 */
104 memset(sig->digest, 0, sig->digest_size);
105
106 ret = crypto_shash_init(desc);
107 if (ret < 0)
108 goto error;
109 tag = ASN1_CONS_BIT | ASN1_SET;
110 ret = crypto_shash_update(desc, &tag, 1);
111 if (ret < 0)
112 goto error;
113 ret = crypto_shash_finup(desc, sinfo->authattrs,
114 sinfo->authattrs_len, sig->digest);
115 if (ret < 0)
116 goto error;
117 pr_devel("AADigest = [%*ph]\n", 8, sig->digest);
118 }
119
120error:
121 kfree(desc);
122error_no_desc:
123 crypto_free_shash(tfm);
124 kleave(" = %d", ret);
125 return ret;
126}
127
128/*
129 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
130 * uses the issuer's name and the issuing certificate serial number for
131 * matching purposes. These must match the certificate issuer's name (not
132 * subject's name) and the certificate serial number [RFC 2315 6.7].
133 */
134static int pkcs7_find_key(struct pkcs7_message *pkcs7,
135 struct pkcs7_signed_info *sinfo)
136{
137 struct x509_certificate *x509;
138 unsigned certix = 1;
139
140 kenter("%u", sinfo->index);
141
142 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
143 /* I'm _assuming_ that the generator of the PKCS#7 message will
144 * encode the fields from the X.509 cert in the same way in the
145 * PKCS#7 message - but I can't be 100% sure of that. It's
146 * possible this will need element-by-element comparison.
147 */
148 if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0]))
149 continue;
150 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
151 sinfo->index, certix);
152
153 if (x509->pub->pkey_algo != sinfo->sig->pkey_algo) {
154 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
155 sinfo->index);
156 continue;
157 }
158
159 sinfo->signer = x509;
160 return 0;
161 }
162
163 /* The relevant X.509 cert isn't found here, but it might be found in
164 * the trust keyring.
165 */
166 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
167 sinfo->index,
168 sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data);
169 return 0;
170}
171
172/*
173 * Verify the internal certificate chain as best we can.
174 */
175static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
176 struct pkcs7_signed_info *sinfo)
177{
178 struct public_key_signature *sig;
179 struct x509_certificate *x509 = sinfo->signer, *p;
180 struct asymmetric_key_id *auth;
181 int ret;
182
183 kenter("");
184
185 for (p = pkcs7->certs; p; p = p->next)
186 p->seen = false;
187
188 for (;;) {
189 pr_debug("verify %s: %*phN\n",
190 x509->subject,
191 x509->raw_serial_size, x509->raw_serial);
192 x509->seen = true;
193 if (x509->unsupported_key)
194 goto unsupported_crypto_in_x509;
195
196 pr_debug("- issuer %s\n", x509->issuer);
197 sig = x509->sig;
198 if (sig->auth_ids[0])
199 pr_debug("- authkeyid.id %*phN\n",
200 sig->auth_ids[0]->len, sig->auth_ids[0]->data);
201 if (sig->auth_ids[1])
202 pr_debug("- authkeyid.skid %*phN\n",
203 sig->auth_ids[1]->len, sig->auth_ids[1]->data);
204
205 if (x509->self_signed) {
206 /* If there's no authority certificate specified, then
207 * the certificate must be self-signed and is the root
208 * of the chain. Likewise if the cert is its own
209 * authority.
210 */
211 if (x509->unsupported_sig)
212 goto unsupported_crypto_in_x509;
213 x509->signer = x509;
214 pr_debug("- self-signed\n");
215 return 0;
216 }
217
218 /* Look through the X.509 certificates in the PKCS#7 message's
219 * list to see if the next one is there.
220 */
221 auth = sig->auth_ids[0];
222 if (auth) {
223 pr_debug("- want %*phN\n", auth->len, auth->data);
224 for (p = pkcs7->certs; p; p = p->next) {
225 pr_debug("- cmp [%u] %*phN\n",
226 p->index, p->id->len, p->id->data);
227 if (asymmetric_key_id_same(p->id, auth))
228 goto found_issuer_check_skid;
229 }
230 } else if (sig->auth_ids[1]) {
231 auth = sig->auth_ids[1];
232 pr_debug("- want %*phN\n", auth->len, auth->data);
233 for (p = pkcs7->certs; p; p = p->next) {
234 if (!p->skid)
235 continue;
236 pr_debug("- cmp [%u] %*phN\n",
237 p->index, p->skid->len, p->skid->data);
238 if (asymmetric_key_id_same(p->skid, auth))
239 goto found_issuer;
240 }
241 }
242
243 /* We didn't find the root of this chain */
244 pr_debug("- top\n");
245 return 0;
246
247 found_issuer_check_skid:
248 /* We matched issuer + serialNumber, but if there's an
249 * authKeyId.keyId, that must match the CA subjKeyId also.
250 */
251 if (sig->auth_ids[1] &&
252 !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
253 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
254 sinfo->index, x509->index, p->index);
255 return -EKEYREJECTED;
256 }
257 found_issuer:
258 pr_debug("- subject %s\n", p->subject);
259 if (p->seen) {
260 pr_warn("Sig %u: X.509 chain contains loop\n",
261 sinfo->index);
262 return 0;
263 }
264 ret = public_key_verify_signature(p->pub, p->sig);
265 if (ret < 0)
266 return ret;
267 x509->signer = p;
268 if (x509 == p) {
269 pr_debug("- self-signed\n");
270 return 0;
271 }
272 x509 = p;
273 might_sleep();
274 }
275
276unsupported_crypto_in_x509:
277 /* Just prune the certificate chain at this point if we lack some
278 * crypto module to go further. Note, however, we don't want to set
279 * sinfo->unsupported_crypto as the signed info block may still be
280 * validatable against an X.509 cert lower in the chain that we have a
281 * trusted copy of.
282 */
283 return 0;
284}
285
286/*
287 * Verify one signed information block from a PKCS#7 message.
288 */
289static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
290 struct pkcs7_signed_info *sinfo)
291{
292 int ret;
293
294 kenter(",%u", sinfo->index);
295
296 /* First of all, digest the data in the PKCS#7 message and the
297 * signed information block
298 */
299 ret = pkcs7_digest(pkcs7, sinfo);
300 if (ret < 0)
301 return ret;
302
303 /* Find the key for the signature if there is one */
304 ret = pkcs7_find_key(pkcs7, sinfo);
305 if (ret < 0)
306 return ret;
307
308 if (!sinfo->signer)
309 return 0;
310
311 pr_devel("Using X.509[%u] for sig %u\n",
312 sinfo->signer->index, sinfo->index);
313
314 /* Check that the PKCS#7 signing time is valid according to the X.509
315 * certificate. We can't, however, check against the system clock
316 * since that may not have been set yet and may be wrong.
317 */
318 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
319 if (sinfo->signing_time < sinfo->signer->valid_from ||
320 sinfo->signing_time > sinfo->signer->valid_to) {
321 pr_warn("Message signed outside of X.509 validity window\n");
322 return -EKEYREJECTED;
323 }
324 }
325
326 /* Verify the PKCS#7 binary against the key */
327 ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig);
328 if (ret < 0)
329 return ret;
330
331 pr_devel("Verified signature %u\n", sinfo->index);
332
333 /* Verify the internal certificate chain */
334 return pkcs7_verify_sig_chain(pkcs7, sinfo);
335}
336
337/**
338 * pkcs7_verify - Verify a PKCS#7 message
339 * @pkcs7: The PKCS#7 message to be verified
340 * @usage: The use to which the key is being put
341 *
342 * Verify a PKCS#7 message is internally consistent - that is, the data digest
343 * matches the digest in the AuthAttrs and any signature in the message or one
344 * of the X.509 certificates it carries that matches another X.509 cert in the
345 * message can be verified.
346 *
347 * This does not look to match the contents of the PKCS#7 message against any
348 * external public keys.
349 *
350 * Returns, in order of descending priority:
351 *
352 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
353 * odds with the specified usage, or:
354 *
355 * (*) -EKEYREJECTED if a signature failed to match for which we found an
356 * appropriate X.509 certificate, or:
357 *
358 * (*) -EBADMSG if some part of the message was invalid, or:
359 *
360 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
361 * crypto modules couldn't be found, or:
362 *
363 * (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
364 * (note that a signature chain may be of zero length), or:
365 */
366int pkcs7_verify(struct pkcs7_message *pkcs7,
367 enum key_being_used_for usage)
368{
369 struct pkcs7_signed_info *sinfo;
370 int enopkg = -ENOPKG;
371 int ret;
372
373 kenter("");
374
375 switch (usage) {
376 case VERIFYING_MODULE_SIGNATURE:
377 if (pkcs7->data_type != OID_data) {
378 pr_warn("Invalid module sig (not pkcs7-data)\n");
379 return -EKEYREJECTED;
380 }
381 if (pkcs7->have_authattrs) {
382 pr_warn("Invalid module sig (has authattrs)\n");
383 return -EKEYREJECTED;
384 }
385 break;
386 case VERIFYING_FIRMWARE_SIGNATURE:
387 if (pkcs7->data_type != OID_data) {
388 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
389 return -EKEYREJECTED;
390 }
391 if (!pkcs7->have_authattrs) {
392 pr_warn("Invalid firmware sig (missing authattrs)\n");
393 return -EKEYREJECTED;
394 }
395 break;
396 case VERIFYING_KEXEC_PE_SIGNATURE:
397 if (pkcs7->data_type != OID_msIndirectData) {
398 pr_warn("Invalid kexec sig (not Authenticode)\n");
399 return -EKEYREJECTED;
400 }
401 /* Authattr presence checked in parser */
402 break;
403 case VERIFYING_UNSPECIFIED_SIGNATURE:
404 if (pkcs7->data_type != OID_data) {
405 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
406 return -EKEYREJECTED;
407 }
408 break;
409 default:
410 return -EINVAL;
411 }
412
413 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
414 ret = pkcs7_verify_one(pkcs7, sinfo);
415 if (ret < 0) {
416 if (ret == -ENOPKG) {
417 sinfo->unsupported_crypto = true;
418 continue;
419 }
420 kleave(" = %d", ret);
421 return ret;
422 }
423 enopkg = 0;
424 }
425
426 kleave(" = %d", enopkg);
427 return enopkg;
428}
429EXPORT_SYMBOL_GPL(pkcs7_verify);
430
431/**
432 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
433 * @pkcs7: The PKCS#7 message
434 * @data: The data to be verified
435 * @datalen: The amount of data
436 *
437 * Supply the detached data needed to verify a PKCS#7 message. Note that no
438 * attempt to retain/pin the data is made. That is left to the caller. The
439 * data will not be modified by pkcs7_verify() and will not be freed when the
440 * PKCS#7 message is freed.
441 *
442 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
443 */
444int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
445 const void *data, size_t datalen)
446{
447 if (pkcs7->data) {
448 pr_debug("Data already supplied\n");
449 return -EINVAL;
450 }
451 pkcs7->data = data;
452 pkcs7->data_len = datalen;
453 return 0;
454}