Commit | Line | Data |
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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
9f0d3314 DH |
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) | |
9f0d3314 DH |
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> | |
e201af16 | 15 | #include <crypto/hash_info.h> |
db6c43bd | 16 | #include <crypto/public_key.h> |
9f0d3314 DH |
17 | #include "pkcs7_parser.h" |
18 | ||
19 | /* | |
20 | * Digest the relevant parts of the PKCS#7 data | |
21 | */ | |
22 | static int pkcs7_digest(struct pkcs7_message *pkcs7, | |
23 | struct pkcs7_signed_info *sinfo) | |
24 | { | |
566a117a | 25 | struct public_key_signature *sig = sinfo->sig; |
9f0d3314 DH |
26 | struct crypto_shash *tfm; |
27 | struct shash_desc *desc; | |
566a117a | 28 | size_t desc_size; |
9f0d3314 DH |
29 | int ret; |
30 | ||
566a117a | 31 | kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo); |
9f0d3314 | 32 | |
e201af16 TJB |
33 | /* The digest was calculated already. */ |
34 | if (sig->digest) | |
35 | return 0; | |
36 | ||
566a117a | 37 | if (!sinfo->sig->hash_algo) |
9f0d3314 DH |
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 | */ | |
566a117a | 43 | tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0); |
9f0d3314 DH |
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); | |
566a117a | 48 | sig->digest_size = crypto_shash_digestsize(tfm); |
9f0d3314 DH |
49 | |
50 | ret = -ENOMEM; | |
566a117a DH |
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) | |
9f0d3314 DH |
57 | goto error_no_desc; |
58 | ||
9f0d3314 | 59 | desc->tfm = tfm; |
9f0d3314 DH |
60 | |
61 | /* Digest the message [RFC2315 9.3] */ | |
a80745a6 EB |
62 | ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len, |
63 | sig->digest); | |
9f0d3314 DH |
64 | if (ret < 0) |
65 | goto error; | |
566a117a | 66 | pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest); |
9f0d3314 DH |
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 | */ | |
99db4435 | 72 | if (sinfo->authattrs) { |
9f0d3314 DH |
73 | u8 tag; |
74 | ||
99db4435 DH |
75 | if (!sinfo->msgdigest) { |
76 | pr_warn("Sig %u: No messageDigest\n", sinfo->index); | |
77 | ret = -EKEYREJECTED; | |
78 | goto error; | |
79 | } | |
80 | ||
566a117a | 81 | if (sinfo->msgdigest_len != sig->digest_size) { |
3584c1db RH |
82 | pr_warn("Sig %u: Invalid digest size (%u)\n", |
83 | sinfo->index, sinfo->msgdigest_len); | |
9f0d3314 DH |
84 | ret = -EBADMSG; |
85 | goto error; | |
86 | } | |
87 | ||
566a117a DH |
88 | if (memcmp(sig->digest, sinfo->msgdigest, |
89 | sinfo->msgdigest_len) != 0) { | |
3584c1db RH |
90 | pr_warn("Sig %u: Message digest doesn't match\n", |
91 | sinfo->index); | |
9f0d3314 DH |
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 | */ | |
566a117a | 101 | memset(sig->digest, 0, sig->digest_size); |
9f0d3314 DH |
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, | |
566a117a | 111 | sinfo->authattrs_len, sig->digest); |
9f0d3314 DH |
112 | if (ret < 0) |
113 | goto error; | |
566a117a | 114 | pr_devel("AADigest = [%*ph]\n", 8, sig->digest); |
9f0d3314 DH |
115 | } |
116 | ||
9f0d3314 | 117 | error: |
566a117a | 118 | kfree(desc); |
9f0d3314 DH |
119 | error_no_desc: |
120 | crypto_free_shash(tfm); | |
121 | kleave(" = %d", ret); | |
122 | return ret; | |
123 | } | |
124 | ||
e201af16 TJB |
125 | int 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 | ||
3c0940c4 Y |
144 | i = match_string(hash_algo_name, HASH_ALGO__LAST, |
145 | sinfo->sig->hash_algo); | |
146 | if (i >= 0) | |
147 | *hash_algo = i; | |
e201af16 TJB |
148 | |
149 | return 0; | |
150 | } | |
151 | ||
9f0d3314 | 152 | /* |
a4730357 DH |
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 | */ | |
158 | static 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 | ||
46963b77 | 164 | kenter("%u", sinfo->index); |
a4730357 DH |
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 | */ | |
566a117a | 172 | if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0])) |
a4730357 DH |
173 | continue; |
174 | pr_devel("Sig %u: Found cert serial match X.509[%u]\n", | |
175 | sinfo->index, certix); | |
176 | ||
a4730357 DH |
177 | sinfo->signer = x509; |
178 | return 0; | |
179 | } | |
46963b77 | 180 | |
757932e6 DH |
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, | |
566a117a | 186 | sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data); |
757932e6 | 187 | return 0; |
a4730357 DH |
188 | } |
189 | ||
8c76d793 DH |
190 | /* |
191 | * Verify the internal certificate chain as best we can. | |
192 | */ | |
193 | static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7, | |
194 | struct pkcs7_signed_info *sinfo) | |
195 | { | |
77d0910d | 196 | struct public_key_signature *sig; |
8c76d793 | 197 | struct x509_certificate *x509 = sinfo->signer, *p; |
4573b64a | 198 | struct asymmetric_key_id *auth; |
8c76d793 DH |
199 | int ret; |
200 | ||
201 | kenter(""); | |
202 | ||
203 | for (p = pkcs7->certs; p; p = p->next) | |
204 | p->seen = false; | |
205 | ||
206 | for (;;) { | |
46963b77 DH |
207 | pr_debug("verify %s: %*phN\n", |
208 | x509->subject, | |
209 | x509->raw_serial_size, x509->raw_serial); | |
8c76d793 | 210 | x509->seen = true; |
03bb7931 DH |
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 | ||
412eccba | 223 | pr_debug("- issuer %s\n", x509->issuer); |
77d0910d DH |
224 | sig = x509->sig; |
225 | if (sig->auth_ids[0]) | |
4573b64a | 226 | pr_debug("- authkeyid.id %*phN\n", |
77d0910d DH |
227 | sig->auth_ids[0]->len, sig->auth_ids[0]->data); |
228 | if (sig->auth_ids[1]) | |
4573b64a | 229 | pr_debug("- authkeyid.skid %*phN\n", |
77d0910d | 230 | sig->auth_ids[1]->len, sig->auth_ids[1]->data); |
8c76d793 | 231 | |
6c2dc5ae | 232 | if (x509->self_signed) { |
8c76d793 DH |
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 | */ | |
6c2dc5ae | 238 | if (x509->unsupported_sig) |
9f8b3f32 | 239 | goto unsupported_sig_in_x509; |
8c76d793 DH |
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 | */ | |
77d0910d | 248 | auth = sig->auth_ids[0]; |
4573b64a DH |
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 | } | |
a46e6678 | 257 | } else if (sig->auth_ids[1]) { |
77d0910d | 258 | auth = sig->auth_ids[1]; |
4573b64a DH |
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 | } | |
8c76d793 DH |
268 | } |
269 | ||
270 | /* We didn't find the root of this chain */ | |
271 | pr_debug("- top\n"); | |
272 | return 0; | |
273 | ||
4573b64a DH |
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 | */ | |
77d0910d DH |
278 | if (sig->auth_ids[1] && |
279 | !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) { | |
4573b64a DH |
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 | } | |
8c76d793 | 284 | found_issuer: |
46963b77 | 285 | pr_debug("- subject %s\n", p->subject); |
8c76d793 DH |
286 | if (p->seen) { |
287 | pr_warn("Sig %u: X.509 chain contains loop\n", | |
288 | sinfo->index); | |
289 | return 0; | |
290 | } | |
971b42c0 | 291 | ret = public_key_verify_signature(p->pub, x509->sig); |
8c76d793 DH |
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 | } | |
41559420 | 302 | |
9f8b3f32 | 303 | unsupported_sig_in_x509: |
41559420 DH |
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 | |
6c2dc5ae | 306 | * sinfo->unsupported_crypto as the signed info block may still be |
41559420 DH |
307 | * validatable against an X.509 cert lower in the chain that we have a |
308 | * trusted copy of. | |
309 | */ | |
6c2dc5ae | 310 | return 0; |
8c76d793 DH |
311 | } |
312 | ||
9f0d3314 DH |
313 | /* |
314 | * Verify one signed information block from a PKCS#7 message. | |
315 | */ | |
316 | static 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 | ||
757932e6 | 330 | /* Find the key for the signature if there is one */ |
a4730357 DH |
331 | ret = pkcs7_find_key(pkcs7, sinfo); |
332 | if (ret < 0) | |
333 | return ret; | |
334 | ||
757932e6 DH |
335 | if (!sinfo->signer) |
336 | return 0; | |
337 | ||
a4730357 DH |
338 | pr_devel("Using X.509[%u] for sig %u\n", |
339 | sinfo->signer->index, sinfo->index); | |
340 | ||
99db4435 DH |
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 | ||
a4730357 | 353 | /* Verify the PKCS#7 binary against the key */ |
566a117a | 354 | ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig); |
a4730357 DH |
355 | if (ret < 0) |
356 | return ret; | |
357 | ||
358 | pr_devel("Verified signature %u\n", sinfo->index); | |
359 | ||
8c76d793 DH |
360 | /* Verify the internal certificate chain */ |
361 | return pkcs7_verify_sig_chain(pkcs7, sinfo); | |
9f0d3314 DH |
362 | } |
363 | ||
364 | /** | |
365 | * pkcs7_verify - Verify a PKCS#7 message | |
366 | * @pkcs7: The PKCS#7 message to be verified | |
99db4435 | 367 | * @usage: The use to which the key is being put |
41559420 DH |
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 | * | |
99db4435 DH |
379 | * (*) -EKEYREJECTED if a key was selected that had a usage restriction at |
380 | * odds with the specified usage, or: | |
381 | * | |
41559420 DH |
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 | * | |
29f4a67c | 387 | * (*) 0 if a signature chain passed verification, or: |
41559420 | 388 | * |
03bb7931 DH |
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. | |
9f0d3314 | 393 | */ |
99db4435 DH |
394 | int pkcs7_verify(struct pkcs7_message *pkcs7, |
395 | enum key_being_used_for usage) | |
9f0d3314 DH |
396 | { |
397 | struct pkcs7_signed_info *sinfo; | |
03bb7931 | 398 | int actual_ret = -ENOPKG; |
6c2dc5ae | 399 | int ret; |
9f0d3314 DH |
400 | |
401 | kenter(""); | |
402 | ||
99db4435 DH |
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 | ||
9f0d3314 DH |
441 | for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { |
442 | ret = pkcs7_verify_one(pkcs7, sinfo); | |
29f4a67c EB |
443 | if (sinfo->blacklisted) { |
444 | if (actual_ret == -ENOPKG) | |
445 | actual_ret = -EKEYREJECTED; | |
446 | continue; | |
447 | } | |
9f0d3314 | 448 | if (ret < 0) { |
41559420 DH |
449 | if (ret == -ENOPKG) { |
450 | sinfo->unsupported_crypto = true; | |
451 | continue; | |
452 | } | |
9f0d3314 DH |
453 | kleave(" = %d", ret); |
454 | return ret; | |
455 | } | |
03bb7931 | 456 | actual_ret = 0; |
9f0d3314 DH |
457 | } |
458 | ||
03bb7931 DH |
459 | kleave(" = %d", actual_ret); |
460 | return actual_ret; | |
9f0d3314 DH |
461 | } |
462 | EXPORT_SYMBOL_GPL(pkcs7_verify); | |
4ebdb76f DH |
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 | */ | |
477 | int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7, | |
478 | const void *data, size_t datalen) | |
479 | { | |
480 | if (pkcs7->data) { | |
3584c1db | 481 | pr_warn("Data already supplied\n"); |
4ebdb76f DH |
482 | return -EINVAL; |
483 | } | |
484 | pkcs7->data = data; | |
485 | pkcs7->data_len = datalen; | |
486 | return 0; | |
487 | } | |
0f5d4a0b | 488 | EXPORT_SYMBOL_GPL(pkcs7_supply_detached_data); |