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9f0d3314 DH |
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> | |
db6c43bd | 19 | #include <crypto/public_key.h> |
9f0d3314 DH |
20 | #include "pkcs7_parser.h" |
21 | ||
22 | /* | |
23 | * Digest the relevant parts of the PKCS#7 data | |
24 | */ | |
25 | static int pkcs7_digest(struct pkcs7_message *pkcs7, | |
26 | struct pkcs7_signed_info *sinfo) | |
27 | { | |
566a117a | 28 | struct public_key_signature *sig = sinfo->sig; |
9f0d3314 DH |
29 | struct crypto_shash *tfm; |
30 | struct shash_desc *desc; | |
566a117a | 31 | size_t desc_size; |
9f0d3314 DH |
32 | int ret; |
33 | ||
566a117a | 34 | kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo); |
9f0d3314 | 35 | |
566a117a | 36 | if (!sinfo->sig->hash_algo) |
9f0d3314 DH |
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 | */ | |
566a117a | 42 | tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0); |
9f0d3314 DH |
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); | |
566a117a | 47 | sig->digest_size = crypto_shash_digestsize(tfm); |
9f0d3314 DH |
48 | |
49 | ret = -ENOMEM; | |
566a117a DH |
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) | |
9f0d3314 DH |
56 | goto error_no_desc; |
57 | ||
9f0d3314 DH |
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; | |
566a117a DH |
65 | ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, |
66 | sig->digest); | |
9f0d3314 DH |
67 | if (ret < 0) |
68 | goto error; | |
566a117a | 69 | pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest); |
9f0d3314 DH |
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 | */ | |
99db4435 | 75 | if (sinfo->authattrs) { |
9f0d3314 DH |
76 | u8 tag; |
77 | ||
99db4435 DH |
78 | if (!sinfo->msgdigest) { |
79 | pr_warn("Sig %u: No messageDigest\n", sinfo->index); | |
80 | ret = -EKEYREJECTED; | |
81 | goto error; | |
82 | } | |
83 | ||
566a117a | 84 | if (sinfo->msgdigest_len != sig->digest_size) { |
9f0d3314 DH |
85 | pr_debug("Sig %u: Invalid digest size (%u)\n", |
86 | sinfo->index, sinfo->msgdigest_len); | |
87 | ret = -EBADMSG; | |
88 | goto error; | |
89 | } | |
90 | ||
566a117a DH |
91 | if (memcmp(sig->digest, sinfo->msgdigest, |
92 | sinfo->msgdigest_len) != 0) { | |
9f0d3314 DH |
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 | */ | |
566a117a | 104 | memset(sig->digest, 0, sig->digest_size); |
9f0d3314 DH |
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, | |
566a117a | 114 | sinfo->authattrs_len, sig->digest); |
9f0d3314 DH |
115 | if (ret < 0) |
116 | goto error; | |
566a117a | 117 | pr_devel("AADigest = [%*ph]\n", 8, sig->digest); |
9f0d3314 DH |
118 | } |
119 | ||
9f0d3314 | 120 | error: |
566a117a | 121 | kfree(desc); |
9f0d3314 DH |
122 | error_no_desc: |
123 | crypto_free_shash(tfm); | |
124 | kleave(" = %d", ret); | |
125 | return ret; | |
126 | } | |
127 | ||
128 | /* | |
a4730357 DH |
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 | */ | |
134 | static 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 | ||
46963b77 | 140 | kenter("%u", sinfo->index); |
a4730357 DH |
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 | */ | |
566a117a | 148 | if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0])) |
a4730357 DH |
149 | continue; |
150 | pr_devel("Sig %u: Found cert serial match X.509[%u]\n", | |
151 | sinfo->index, certix); | |
152 | ||
566a117a | 153 | if (x509->pub->pkey_algo != sinfo->sig->pkey_algo) { |
a4730357 DH |
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 | } | |
46963b77 | 162 | |
757932e6 DH |
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, | |
566a117a | 168 | sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data); |
757932e6 | 169 | return 0; |
a4730357 DH |
170 | } |
171 | ||
8c76d793 DH |
172 | /* |
173 | * Verify the internal certificate chain as best we can. | |
174 | */ | |
175 | static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7, | |
176 | struct pkcs7_signed_info *sinfo) | |
177 | { | |
77d0910d | 178 | struct public_key_signature *sig; |
8c76d793 | 179 | struct x509_certificate *x509 = sinfo->signer, *p; |
4573b64a | 180 | struct asymmetric_key_id *auth; |
8c76d793 DH |
181 | int ret; |
182 | ||
183 | kenter(""); | |
184 | ||
185 | for (p = pkcs7->certs; p; p = p->next) | |
186 | p->seen = false; | |
187 | ||
188 | for (;;) { | |
46963b77 DH |
189 | pr_debug("verify %s: %*phN\n", |
190 | x509->subject, | |
191 | x509->raw_serial_size, x509->raw_serial); | |
8c76d793 | 192 | x509->seen = true; |
6c2dc5ae DH |
193 | if (x509->unsupported_key) |
194 | goto unsupported_crypto_in_x509; | |
8c76d793 | 195 | |
412eccba | 196 | pr_debug("- issuer %s\n", x509->issuer); |
77d0910d DH |
197 | sig = x509->sig; |
198 | if (sig->auth_ids[0]) | |
4573b64a | 199 | pr_debug("- authkeyid.id %*phN\n", |
77d0910d DH |
200 | sig->auth_ids[0]->len, sig->auth_ids[0]->data); |
201 | if (sig->auth_ids[1]) | |
4573b64a | 202 | pr_debug("- authkeyid.skid %*phN\n", |
77d0910d | 203 | sig->auth_ids[1]->len, sig->auth_ids[1]->data); |
8c76d793 | 204 | |
6c2dc5ae | 205 | if (x509->self_signed) { |
8c76d793 DH |
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 | */ | |
6c2dc5ae DH |
211 | if (x509->unsupported_sig) |
212 | goto unsupported_crypto_in_x509; | |
8c76d793 DH |
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 | */ | |
77d0910d | 221 | auth = sig->auth_ids[0]; |
4573b64a DH |
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 | } | |
a46e6678 | 230 | } else if (sig->auth_ids[1]) { |
77d0910d | 231 | auth = sig->auth_ids[1]; |
4573b64a DH |
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 | } | |
8c76d793 DH |
241 | } |
242 | ||
243 | /* We didn't find the root of this chain */ | |
244 | pr_debug("- top\n"); | |
245 | return 0; | |
246 | ||
4573b64a DH |
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 | */ | |
77d0910d DH |
251 | if (sig->auth_ids[1] && |
252 | !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) { | |
4573b64a DH |
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 | } | |
8c76d793 | 257 | found_issuer: |
46963b77 | 258 | pr_debug("- subject %s\n", p->subject); |
8c76d793 DH |
259 | if (p->seen) { |
260 | pr_warn("Sig %u: X.509 chain contains loop\n", | |
261 | sinfo->index); | |
262 | return 0; | |
263 | } | |
6c2dc5ae | 264 | ret = public_key_verify_signature(p->pub, p->sig); |
8c76d793 DH |
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 | } | |
41559420 | 275 | |
6c2dc5ae | 276 | unsupported_crypto_in_x509: |
41559420 DH |
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 | |
6c2dc5ae | 279 | * sinfo->unsupported_crypto as the signed info block may still be |
41559420 DH |
280 | * validatable against an X.509 cert lower in the chain that we have a |
281 | * trusted copy of. | |
282 | */ | |
6c2dc5ae | 283 | return 0; |
8c76d793 DH |
284 | } |
285 | ||
9f0d3314 DH |
286 | /* |
287 | * Verify one signed information block from a PKCS#7 message. | |
288 | */ | |
289 | static 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 | ||
757932e6 | 303 | /* Find the key for the signature if there is one */ |
a4730357 DH |
304 | ret = pkcs7_find_key(pkcs7, sinfo); |
305 | if (ret < 0) | |
306 | return ret; | |
307 | ||
757932e6 DH |
308 | if (!sinfo->signer) |
309 | return 0; | |
310 | ||
a4730357 DH |
311 | pr_devel("Using X.509[%u] for sig %u\n", |
312 | sinfo->signer->index, sinfo->index); | |
313 | ||
99db4435 DH |
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 | ||
a4730357 | 326 | /* Verify the PKCS#7 binary against the key */ |
566a117a | 327 | ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig); |
a4730357 DH |
328 | if (ret < 0) |
329 | return ret; | |
330 | ||
331 | pr_devel("Verified signature %u\n", sinfo->index); | |
332 | ||
8c76d793 DH |
333 | /* Verify the internal certificate chain */ |
334 | return pkcs7_verify_sig_chain(pkcs7, sinfo); | |
9f0d3314 DH |
335 | } |
336 | ||
337 | /** | |
338 | * pkcs7_verify - Verify a PKCS#7 message | |
339 | * @pkcs7: The PKCS#7 message to be verified | |
99db4435 | 340 | * @usage: The use to which the key is being put |
41559420 DH |
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 | * | |
99db4435 DH |
352 | * (*) -EKEYREJECTED if a key was selected that had a usage restriction at |
353 | * odds with the specified usage, or: | |
354 | * | |
41559420 DH |
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: | |
9f0d3314 | 365 | */ |
99db4435 DH |
366 | int pkcs7_verify(struct pkcs7_message *pkcs7, |
367 | enum key_being_used_for usage) | |
9f0d3314 DH |
368 | { |
369 | struct pkcs7_signed_info *sinfo; | |
41559420 | 370 | int enopkg = -ENOPKG; |
6c2dc5ae | 371 | int ret; |
9f0d3314 DH |
372 | |
373 | kenter(""); | |
374 | ||
99db4435 DH |
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 | ||
9f0d3314 DH |
413 | for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { |
414 | ret = pkcs7_verify_one(pkcs7, sinfo); | |
415 | if (ret < 0) { | |
41559420 DH |
416 | if (ret == -ENOPKG) { |
417 | sinfo->unsupported_crypto = true; | |
418 | continue; | |
419 | } | |
9f0d3314 DH |
420 | kleave(" = %d", ret); |
421 | return ret; | |
422 | } | |
41559420 | 423 | enopkg = 0; |
9f0d3314 DH |
424 | } |
425 | ||
41559420 DH |
426 | kleave(" = %d", enopkg); |
427 | return enopkg; | |
9f0d3314 DH |
428 | } |
429 | EXPORT_SYMBOL_GPL(pkcs7_verify); | |
4ebdb76f DH |
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 | */ | |
444 | int 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 | } |