blob: 325575caf6b452ba89ef84985c13d504e956f86e [file] [log] [blame]
David Howells9f0d3312014-07-01 16:40:19 +01001/* 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 "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 crypto_shash *tfm;
29 struct shash_desc *desc;
30 size_t digest_size, desc_size;
31 void *digest;
32 int ret;
33
34 kenter(",%u,%u", sinfo->index, sinfo->sig.pkey_hash_algo);
35
36 if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
37 !hash_algo_name[sinfo->sig.pkey_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(hash_algo_name[sinfo->sig.pkey_hash_algo],
44 0, 0);
45 if (IS_ERR(tfm))
46 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
47
48 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
49 sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm);
50
51 ret = -ENOMEM;
Sowmini Varadhan62f57d02015-10-13 10:54:01 -040052 digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
53 GFP_KERNEL);
David Howells9f0d3312014-07-01 16:40:19 +010054 if (!digest)
55 goto error_no_desc;
56
Sowmini Varadhan62f57d02015-10-13 10:54:01 -040057 desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
David Howells9f0d3312014-07-01 16:40:19 +010058 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, digest);
66 if (ret < 0)
67 goto error;
68 pr_devel("MsgDigest = [%*ph]\n", 8, digest);
69
70 /* However, if there are authenticated attributes, there must be a
71 * message digest attribute amongst them which corresponds to the
72 * digest we just calculated.
73 */
David Howells99db4432015-08-05 15:22:27 +010074 if (sinfo->authattrs) {
David Howells9f0d3312014-07-01 16:40:19 +010075 u8 tag;
76
David Howells99db4432015-08-05 15:22:27 +010077 if (!sinfo->msgdigest) {
78 pr_warn("Sig %u: No messageDigest\n", sinfo->index);
79 ret = -EKEYREJECTED;
80 goto error;
81 }
82
David Howells9f0d3312014-07-01 16:40:19 +010083 if (sinfo->msgdigest_len != sinfo->sig.digest_size) {
84 pr_debug("Sig %u: Invalid digest size (%u)\n",
85 sinfo->index, sinfo->msgdigest_len);
86 ret = -EBADMSG;
87 goto error;
88 }
89
90 if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) {
91 pr_debug("Sig %u: Message digest doesn't match\n",
92 sinfo->index);
93 ret = -EKEYREJECTED;
94 goto error;
95 }
96
97 /* We then calculate anew, using the authenticated attributes
98 * as the contents of the digest instead. Note that we need to
99 * convert the attributes from a CONT.0 into a SET before we
100 * hash it.
101 */
102 memset(digest, 0, sinfo->sig.digest_size);
103
104 ret = crypto_shash_init(desc);
105 if (ret < 0)
106 goto error;
107 tag = ASN1_CONS_BIT | ASN1_SET;
108 ret = crypto_shash_update(desc, &tag, 1);
109 if (ret < 0)
110 goto error;
111 ret = crypto_shash_finup(desc, sinfo->authattrs,
112 sinfo->authattrs_len, digest);
113 if (ret < 0)
114 goto error;
115 pr_devel("AADigest = [%*ph]\n", 8, digest);
116 }
117
118 sinfo->sig.digest = digest;
119 digest = NULL;
120
121error:
122 kfree(digest);
123error_no_desc:
124 crypto_free_shash(tfm);
125 kleave(" = %d", ret);
126 return ret;
127}
128
129/*
David Howellsa4730352014-07-01 16:40:19 +0100130 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
131 * uses the issuer's name and the issuing certificate serial number for
132 * matching purposes. These must match the certificate issuer's name (not
133 * subject's name) and the certificate serial number [RFC 2315 6.7].
134 */
135static int pkcs7_find_key(struct pkcs7_message *pkcs7,
136 struct pkcs7_signed_info *sinfo)
137{
138 struct x509_certificate *x509;
139 unsigned certix = 1;
140
David Howells46963b72014-09-16 17:36:13 +0100141 kenter("%u", sinfo->index);
David Howellsa4730352014-07-01 16:40:19 +0100142
143 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
144 /* I'm _assuming_ that the generator of the PKCS#7 message will
145 * encode the fields from the X.509 cert in the same way in the
146 * PKCS#7 message - but I can't be 100% sure of that. It's
147 * possible this will need element-by-element comparison.
148 */
David Howells46963b72014-09-16 17:36:13 +0100149 if (!asymmetric_key_id_same(x509->id, sinfo->signing_cert_id))
David Howellsa4730352014-07-01 16:40:19 +0100150 continue;
151 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
152 sinfo->index, certix);
153
David Howellsa4730352014-07-01 16:40:19 +0100154 if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
155 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
156 sinfo->index);
157 continue;
158 }
159
160 sinfo->signer = x509;
161 return 0;
162 }
David Howells46963b72014-09-16 17:36:13 +0100163
David Howells757932e2014-09-16 17:36:17 +0100164 /* The relevant X.509 cert isn't found here, but it might be found in
165 * the trust keyring.
166 */
167 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
168 sinfo->index,
169 sinfo->signing_cert_id->len, sinfo->signing_cert_id->data);
170 return 0;
David Howellsa4730352014-07-01 16:40:19 +0100171}
172
David Howells9f0d3312014-07-01 16:40:19 +0100173/*
David Howells8c76d792014-07-01 16:40:19 +0100174 * Verify the internal certificate chain as best we can.
175 */
176static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
177 struct pkcs7_signed_info *sinfo)
178{
179 struct x509_certificate *x509 = sinfo->signer, *p;
David Howells4573b642015-07-20 21:16:26 +0100180 struct asymmetric_key_id *auth;
David Howells8c76d792014-07-01 16:40:19 +0100181 int ret;
182
183 kenter("");
184
185 for (p = pkcs7->certs; p; p = p->next)
186 p->seen = false;
187
188 for (;;) {
David Howells46963b72014-09-16 17:36:13 +0100189 pr_debug("verify %s: %*phN\n",
190 x509->subject,
191 x509->raw_serial_size, x509->raw_serial);
David Howells8c76d792014-07-01 16:40:19 +0100192 x509->seen = true;
193 ret = x509_get_sig_params(x509);
194 if (ret < 0)
David Howells41559422014-09-16 17:36:15 +0100195 goto maybe_missing_crypto_in_x509;
David Howells8c76d792014-07-01 16:40:19 +0100196
David Howells412eccb2014-07-31 14:46:44 +0100197 pr_debug("- issuer %s\n", x509->issuer);
David Howells4573b642015-07-20 21:16:26 +0100198 if (x509->akid_id)
199 pr_debug("- authkeyid.id %*phN\n",
200 x509->akid_id->len, x509->akid_id->data);
David Howellsb92e6572015-07-20 21:16:26 +0100201 if (x509->akid_skid)
David Howells4573b642015-07-20 21:16:26 +0100202 pr_debug("- authkeyid.skid %*phN\n",
David Howellsb92e6572015-07-20 21:16:26 +0100203 x509->akid_skid->len, x509->akid_skid->data);
David Howells8c76d792014-07-01 16:40:19 +0100204
David Howells4573b642015-07-20 21:16:26 +0100205 if ((!x509->akid_id && !x509->akid_skid) ||
David Howells412eccb2014-07-31 14:46:44 +0100206 strcmp(x509->subject, x509->issuer) == 0) {
David Howells8c76d792014-07-01 16:40:19 +0100207 /* If there's no authority certificate specified, then
208 * the certificate must be self-signed and is the root
209 * of the chain. Likewise if the cert is its own
210 * authority.
211 */
212 pr_debug("- no auth?\n");
213 if (x509->raw_subject_size != x509->raw_issuer_size ||
214 memcmp(x509->raw_subject, x509->raw_issuer,
215 x509->raw_issuer_size) != 0)
216 return 0;
217
218 ret = x509_check_signature(x509->pub, x509);
219 if (ret < 0)
David Howells41559422014-09-16 17:36:15 +0100220 goto maybe_missing_crypto_in_x509;
David Howells8c76d792014-07-01 16:40:19 +0100221 x509->signer = x509;
222 pr_debug("- self-signed\n");
223 return 0;
224 }
225
226 /* Look through the X.509 certificates in the PKCS#7 message's
227 * list to see if the next one is there.
228 */
David Howells4573b642015-07-20 21:16:26 +0100229 auth = x509->akid_id;
230 if (auth) {
231 pr_debug("- want %*phN\n", auth->len, auth->data);
232 for (p = pkcs7->certs; p; p = p->next) {
233 pr_debug("- cmp [%u] %*phN\n",
234 p->index, p->id->len, p->id->data);
235 if (asymmetric_key_id_same(p->id, auth))
236 goto found_issuer_check_skid;
237 }
238 } else {
239 auth = x509->akid_skid;
240 pr_debug("- want %*phN\n", auth->len, auth->data);
241 for (p = pkcs7->certs; p; p = p->next) {
242 if (!p->skid)
243 continue;
244 pr_debug("- cmp [%u] %*phN\n",
245 p->index, p->skid->len, p->skid->data);
246 if (asymmetric_key_id_same(p->skid, auth))
247 goto found_issuer;
248 }
David Howells8c76d792014-07-01 16:40:19 +0100249 }
250
251 /* We didn't find the root of this chain */
252 pr_debug("- top\n");
253 return 0;
254
David Howells4573b642015-07-20 21:16:26 +0100255 found_issuer_check_skid:
256 /* We matched issuer + serialNumber, but if there's an
257 * authKeyId.keyId, that must match the CA subjKeyId also.
258 */
259 if (x509->akid_skid &&
260 !asymmetric_key_id_same(p->skid, x509->akid_skid)) {
261 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
262 sinfo->index, x509->index, p->index);
263 return -EKEYREJECTED;
264 }
David Howells8c76d792014-07-01 16:40:19 +0100265 found_issuer:
David Howells46963b72014-09-16 17:36:13 +0100266 pr_debug("- subject %s\n", p->subject);
David Howells8c76d792014-07-01 16:40:19 +0100267 if (p->seen) {
268 pr_warn("Sig %u: X.509 chain contains loop\n",
269 sinfo->index);
270 return 0;
271 }
272 ret = x509_check_signature(p->pub, x509);
273 if (ret < 0)
274 return ret;
275 x509->signer = p;
276 if (x509 == p) {
277 pr_debug("- self-signed\n");
278 return 0;
279 }
280 x509 = p;
281 might_sleep();
282 }
David Howells41559422014-09-16 17:36:15 +0100283
284maybe_missing_crypto_in_x509:
285 /* Just prune the certificate chain at this point if we lack some
286 * crypto module to go further. Note, however, we don't want to set
287 * sinfo->missing_crypto as the signed info block may still be
288 * validatable against an X.509 cert lower in the chain that we have a
289 * trusted copy of.
290 */
291 if (ret == -ENOPKG)
292 return 0;
293 return ret;
David Howells8c76d792014-07-01 16:40:19 +0100294}
295
296/*
David Howells9f0d3312014-07-01 16:40:19 +0100297 * Verify one signed information block from a PKCS#7 message.
298 */
299static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
300 struct pkcs7_signed_info *sinfo)
301{
302 int ret;
303
304 kenter(",%u", sinfo->index);
305
306 /* First of all, digest the data in the PKCS#7 message and the
307 * signed information block
308 */
309 ret = pkcs7_digest(pkcs7, sinfo);
310 if (ret < 0)
311 return ret;
312
David Howells757932e2014-09-16 17:36:17 +0100313 /* Find the key for the signature if there is one */
David Howellsa4730352014-07-01 16:40:19 +0100314 ret = pkcs7_find_key(pkcs7, sinfo);
315 if (ret < 0)
316 return ret;
317
David Howells757932e2014-09-16 17:36:17 +0100318 if (!sinfo->signer)
319 return 0;
320
David Howellsa4730352014-07-01 16:40:19 +0100321 pr_devel("Using X.509[%u] for sig %u\n",
322 sinfo->signer->index, sinfo->index);
323
David Howells99db4432015-08-05 15:22:27 +0100324 /* Check that the PKCS#7 signing time is valid according to the X.509
325 * certificate. We can't, however, check against the system clock
326 * since that may not have been set yet and may be wrong.
327 */
328 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
329 if (sinfo->signing_time < sinfo->signer->valid_from ||
330 sinfo->signing_time > sinfo->signer->valid_to) {
331 pr_warn("Message signed outside of X.509 validity window\n");
332 return -EKEYREJECTED;
333 }
334 }
335
David Howellsa4730352014-07-01 16:40:19 +0100336 /* Verify the PKCS#7 binary against the key */
337 ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
338 if (ret < 0)
339 return ret;
340
341 pr_devel("Verified signature %u\n", sinfo->index);
342
David Howells8c76d792014-07-01 16:40:19 +0100343 /* Verify the internal certificate chain */
344 return pkcs7_verify_sig_chain(pkcs7, sinfo);
David Howells9f0d3312014-07-01 16:40:19 +0100345}
346
347/**
348 * pkcs7_verify - Verify a PKCS#7 message
349 * @pkcs7: The PKCS#7 message to be verified
David Howells99db4432015-08-05 15:22:27 +0100350 * @usage: The use to which the key is being put
David Howells41559422014-09-16 17:36:15 +0100351 *
352 * Verify a PKCS#7 message is internally consistent - that is, the data digest
353 * matches the digest in the AuthAttrs and any signature in the message or one
354 * of the X.509 certificates it carries that matches another X.509 cert in the
355 * message can be verified.
356 *
357 * This does not look to match the contents of the PKCS#7 message against any
358 * external public keys.
359 *
360 * Returns, in order of descending priority:
361 *
David Howells99db4432015-08-05 15:22:27 +0100362 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
363 * odds with the specified usage, or:
364 *
David Howells41559422014-09-16 17:36:15 +0100365 * (*) -EKEYREJECTED if a signature failed to match for which we found an
366 * appropriate X.509 certificate, or:
367 *
368 * (*) -EBADMSG if some part of the message was invalid, or:
369 *
370 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
371 * crypto modules couldn't be found, or:
372 *
373 * (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
374 * (note that a signature chain may be of zero length), or:
David Howells9f0d3312014-07-01 16:40:19 +0100375 */
David Howells99db4432015-08-05 15:22:27 +0100376int pkcs7_verify(struct pkcs7_message *pkcs7,
377 enum key_being_used_for usage)
David Howells9f0d3312014-07-01 16:40:19 +0100378{
379 struct pkcs7_signed_info *sinfo;
380 struct x509_certificate *x509;
David Howells41559422014-09-16 17:36:15 +0100381 int enopkg = -ENOPKG;
David Howells9f0d3312014-07-01 16:40:19 +0100382 int ret, n;
383
384 kenter("");
385
David Howells99db4432015-08-05 15:22:27 +0100386 switch (usage) {
387 case VERIFYING_MODULE_SIGNATURE:
388 if (pkcs7->data_type != OID_data) {
389 pr_warn("Invalid module sig (not pkcs7-data)\n");
390 return -EKEYREJECTED;
391 }
392 if (pkcs7->have_authattrs) {
393 pr_warn("Invalid module sig (has authattrs)\n");
394 return -EKEYREJECTED;
395 }
396 break;
397 case VERIFYING_FIRMWARE_SIGNATURE:
398 if (pkcs7->data_type != OID_data) {
399 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
400 return -EKEYREJECTED;
401 }
402 if (!pkcs7->have_authattrs) {
403 pr_warn("Invalid firmware sig (missing authattrs)\n");
404 return -EKEYREJECTED;
405 }
406 break;
407 case VERIFYING_KEXEC_PE_SIGNATURE:
408 if (pkcs7->data_type != OID_msIndirectData) {
409 pr_warn("Invalid kexec sig (not Authenticode)\n");
410 return -EKEYREJECTED;
411 }
412 /* Authattr presence checked in parser */
413 break;
414 case VERIFYING_UNSPECIFIED_SIGNATURE:
415 if (pkcs7->data_type != OID_data) {
416 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
417 return -EKEYREJECTED;
418 }
419 break;
420 default:
421 return -EINVAL;
422 }
423
David Howells9f0d3312014-07-01 16:40:19 +0100424 for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
425 ret = x509_get_sig_params(x509);
426 if (ret < 0)
427 return ret;
David Howells9f0d3312014-07-01 16:40:19 +0100428 }
429
430 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
431 ret = pkcs7_verify_one(pkcs7, sinfo);
432 if (ret < 0) {
David Howells41559422014-09-16 17:36:15 +0100433 if (ret == -ENOPKG) {
434 sinfo->unsupported_crypto = true;
435 continue;
436 }
David Howells9f0d3312014-07-01 16:40:19 +0100437 kleave(" = %d", ret);
438 return ret;
439 }
David Howells41559422014-09-16 17:36:15 +0100440 enopkg = 0;
David Howells9f0d3312014-07-01 16:40:19 +0100441 }
442
David Howells41559422014-09-16 17:36:15 +0100443 kleave(" = %d", enopkg);
444 return enopkg;
David Howells9f0d3312014-07-01 16:40:19 +0100445}
446EXPORT_SYMBOL_GPL(pkcs7_verify);
David Howells4ebdb76f2015-07-20 21:16:26 +0100447
448/**
449 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
450 * @pkcs7: The PKCS#7 message
451 * @data: The data to be verified
452 * @datalen: The amount of data
453 *
454 * Supply the detached data needed to verify a PKCS#7 message. Note that no
455 * attempt to retain/pin the data is made. That is left to the caller. The
456 * data will not be modified by pkcs7_verify() and will not be freed when the
457 * PKCS#7 message is freed.
458 *
459 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
460 */
461int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
462 const void *data, size_t datalen)
463{
464 if (pkcs7->data) {
465 pr_debug("Data already supplied\n");
466 return -EINVAL;
467 }
468 pkcs7->data = data;
469 pkcs7->data_len = datalen;
470 return 0;
471}