1 /* Verify the signature on a PKCS#7 message.
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
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"
23 * Digest the relevant parts of the PKCS#7 data
25 static int pkcs7_digest(struct pkcs7_message *pkcs7,
26 struct pkcs7_signed_info *sinfo)
28 struct crypto_shash *tfm;
29 struct shash_desc *desc;
30 size_t digest_size, desc_size;
34 kenter(",%u,%s", sinfo->index, sinfo->sig.hash_algo);
36 if (!sinfo->sig.hash_algo)
39 /* Allocate the hashing algorithm we're going to need and find out how
40 * big the hash operational data will be.
42 tfm = crypto_alloc_shash(sinfo->sig.hash_algo, 0, 0);
44 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
46 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
47 sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm);
50 digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
55 desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
57 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
59 /* Digest the message [RFC2315 9.3] */
60 ret = crypto_shash_init(desc);
63 ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest);
66 pr_devel("MsgDigest = [%*ph]\n", 8, digest);
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.
72 if (sinfo->authattrs) {
75 if (!sinfo->msgdigest) {
76 pr_warn("Sig %u: No messageDigest\n", sinfo->index);
81 if (sinfo->msgdigest_len != sinfo->sig.digest_size) {
82 pr_debug("Sig %u: Invalid digest size (%u)\n",
83 sinfo->index, sinfo->msgdigest_len);
88 if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) {
89 pr_debug("Sig %u: Message digest doesn't match\n",
95 /* We then calculate anew, using the authenticated attributes
96 * as the contents of the digest instead. Note that we need to
97 * convert the attributes from a CONT.0 into a SET before we
100 memset(digest, 0, sinfo->sig.digest_size);
102 ret = crypto_shash_init(desc);
105 tag = ASN1_CONS_BIT | ASN1_SET;
106 ret = crypto_shash_update(desc, &tag, 1);
109 ret = crypto_shash_finup(desc, sinfo->authattrs,
110 sinfo->authattrs_len, digest);
113 pr_devel("AADigest = [%*ph]\n", 8, digest);
116 sinfo->sig.digest = digest;
122 crypto_free_shash(tfm);
123 kleave(" = %d", ret);
128 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
129 * uses the issuer's name and the issuing certificate serial number for
130 * matching purposes. These must match the certificate issuer's name (not
131 * subject's name) and the certificate serial number [RFC 2315 6.7].
133 static int pkcs7_find_key(struct pkcs7_message *pkcs7,
134 struct pkcs7_signed_info *sinfo)
136 struct x509_certificate *x509;
139 kenter("%u", sinfo->index);
141 for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
142 /* I'm _assuming_ that the generator of the PKCS#7 message will
143 * encode the fields from the X.509 cert in the same way in the
144 * PKCS#7 message - but I can't be 100% sure of that. It's
145 * possible this will need element-by-element comparison.
147 if (!asymmetric_key_id_same(x509->id, sinfo->signing_cert_id))
149 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
150 sinfo->index, certix);
152 if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
153 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
158 sinfo->signer = x509;
162 /* The relevant X.509 cert isn't found here, but it might be found in
165 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
167 sinfo->signing_cert_id->len, sinfo->signing_cert_id->data);
172 * Verify the internal certificate chain as best we can.
174 static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
175 struct pkcs7_signed_info *sinfo)
177 struct x509_certificate *x509 = sinfo->signer, *p;
178 struct asymmetric_key_id *auth;
183 for (p = pkcs7->certs; p; p = p->next)
187 pr_debug("verify %s: %*phN\n",
189 x509->raw_serial_size, x509->raw_serial);
191 ret = x509_get_sig_params(x509);
193 goto maybe_missing_crypto_in_x509;
195 pr_debug("- issuer %s\n", x509->issuer);
197 pr_debug("- authkeyid.id %*phN\n",
198 x509->akid_id->len, x509->akid_id->data);
200 pr_debug("- authkeyid.skid %*phN\n",
201 x509->akid_skid->len, x509->akid_skid->data);
203 if ((!x509->akid_id && !x509->akid_skid) ||
204 strcmp(x509->subject, x509->issuer) == 0) {
205 /* If there's no authority certificate specified, then
206 * the certificate must be self-signed and is the root
207 * of the chain. Likewise if the cert is its own
210 pr_debug("- no auth?\n");
211 if (x509->raw_subject_size != x509->raw_issuer_size ||
212 memcmp(x509->raw_subject, x509->raw_issuer,
213 x509->raw_issuer_size) != 0)
216 ret = x509_check_signature(x509->pub, x509);
218 goto maybe_missing_crypto_in_x509;
220 pr_debug("- self-signed\n");
224 /* Look through the X.509 certificates in the PKCS#7 message's
225 * list to see if the next one is there.
227 auth = x509->akid_id;
229 pr_debug("- want %*phN\n", auth->len, auth->data);
230 for (p = pkcs7->certs; p; p = p->next) {
231 pr_debug("- cmp [%u] %*phN\n",
232 p->index, p->id->len, p->id->data);
233 if (asymmetric_key_id_same(p->id, auth))
234 goto found_issuer_check_skid;
237 auth = x509->akid_skid;
238 pr_debug("- want %*phN\n", auth->len, auth->data);
239 for (p = pkcs7->certs; p; p = p->next) {
242 pr_debug("- cmp [%u] %*phN\n",
243 p->index, p->skid->len, p->skid->data);
244 if (asymmetric_key_id_same(p->skid, auth))
249 /* We didn't find the root of this chain */
253 found_issuer_check_skid:
254 /* We matched issuer + serialNumber, but if there's an
255 * authKeyId.keyId, that must match the CA subjKeyId also.
257 if (x509->akid_skid &&
258 !asymmetric_key_id_same(p->skid, x509->akid_skid)) {
259 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
260 sinfo->index, x509->index, p->index);
261 return -EKEYREJECTED;
264 pr_debug("- subject %s\n", p->subject);
266 pr_warn("Sig %u: X.509 chain contains loop\n",
270 ret = x509_check_signature(p->pub, x509);
275 pr_debug("- self-signed\n");
282 maybe_missing_crypto_in_x509:
283 /* Just prune the certificate chain at this point if we lack some
284 * crypto module to go further. Note, however, we don't want to set
285 * sinfo->missing_crypto as the signed info block may still be
286 * validatable against an X.509 cert lower in the chain that we have a
295 * Verify one signed information block from a PKCS#7 message.
297 static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
298 struct pkcs7_signed_info *sinfo)
302 kenter(",%u", sinfo->index);
304 /* First of all, digest the data in the PKCS#7 message and the
305 * signed information block
307 ret = pkcs7_digest(pkcs7, sinfo);
311 /* Find the key for the signature if there is one */
312 ret = pkcs7_find_key(pkcs7, sinfo);
319 pr_devel("Using X.509[%u] for sig %u\n",
320 sinfo->signer->index, sinfo->index);
322 /* Check that the PKCS#7 signing time is valid according to the X.509
323 * certificate. We can't, however, check against the system clock
324 * since that may not have been set yet and may be wrong.
326 if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
327 if (sinfo->signing_time < sinfo->signer->valid_from ||
328 sinfo->signing_time > sinfo->signer->valid_to) {
329 pr_warn("Message signed outside of X.509 validity window\n");
330 return -EKEYREJECTED;
334 /* Verify the PKCS#7 binary against the key */
335 ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
339 pr_devel("Verified signature %u\n", sinfo->index);
341 /* Verify the internal certificate chain */
342 return pkcs7_verify_sig_chain(pkcs7, sinfo);
346 * pkcs7_verify - Verify a PKCS#7 message
347 * @pkcs7: The PKCS#7 message to be verified
348 * @usage: The use to which the key is being put
350 * Verify a PKCS#7 message is internally consistent - that is, the data digest
351 * matches the digest in the AuthAttrs and any signature in the message or one
352 * of the X.509 certificates it carries that matches another X.509 cert in the
353 * message can be verified.
355 * This does not look to match the contents of the PKCS#7 message against any
356 * external public keys.
358 * Returns, in order of descending priority:
360 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
361 * odds with the specified usage, or:
363 * (*) -EKEYREJECTED if a signature failed to match for which we found an
364 * appropriate X.509 certificate, or:
366 * (*) -EBADMSG if some part of the message was invalid, or:
368 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
369 * crypto modules couldn't be found, or:
371 * (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
372 * (note that a signature chain may be of zero length), or:
374 int pkcs7_verify(struct pkcs7_message *pkcs7,
375 enum key_being_used_for usage)
377 struct pkcs7_signed_info *sinfo;
378 struct x509_certificate *x509;
379 int enopkg = -ENOPKG;
385 case VERIFYING_MODULE_SIGNATURE:
386 if (pkcs7->data_type != OID_data) {
387 pr_warn("Invalid module sig (not pkcs7-data)\n");
388 return -EKEYREJECTED;
390 if (pkcs7->have_authattrs) {
391 pr_warn("Invalid module sig (has authattrs)\n");
392 return -EKEYREJECTED;
395 case VERIFYING_FIRMWARE_SIGNATURE:
396 if (pkcs7->data_type != OID_data) {
397 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
398 return -EKEYREJECTED;
400 if (!pkcs7->have_authattrs) {
401 pr_warn("Invalid firmware sig (missing authattrs)\n");
402 return -EKEYREJECTED;
405 case VERIFYING_KEXEC_PE_SIGNATURE:
406 if (pkcs7->data_type != OID_msIndirectData) {
407 pr_warn("Invalid kexec sig (not Authenticode)\n");
408 return -EKEYREJECTED;
410 /* Authattr presence checked in parser */
412 case VERIFYING_UNSPECIFIED_SIGNATURE:
413 if (pkcs7->data_type != OID_data) {
414 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
415 return -EKEYREJECTED;
422 for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
423 ret = x509_get_sig_params(x509);
428 for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
429 ret = pkcs7_verify_one(pkcs7, sinfo);
431 if (ret == -ENOPKG) {
432 sinfo->unsupported_crypto = true;
435 kleave(" = %d", ret);
441 kleave(" = %d", enopkg);
444 EXPORT_SYMBOL_GPL(pkcs7_verify);
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
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.
457 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
459 int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
460 const void *data, size_t datalen)
463 pr_debug("Data already supplied\n");
467 pkcs7->data_len = datalen;