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 "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,%u", sinfo
->index
, sinfo
->sig
.pkey_hash_algo
);
36 if (sinfo
->sig
.pkey_hash_algo
>= PKEY_HASH__LAST
||
37 !hash_algo_name
[sinfo
->sig
.pkey_hash_algo
])
40 /* Allocate the hashing algorithm we're going to need and find out how
41 * big the hash operational data will be.
43 tfm
= crypto_alloc_shash(hash_algo_name
[sinfo
->sig
.pkey_hash_algo
],
46 return (PTR_ERR(tfm
) == -ENOENT
) ? -ENOPKG
: PTR_ERR(tfm
);
48 desc_size
= crypto_shash_descsize(tfm
) + sizeof(*desc
);
49 sinfo
->sig
.digest_size
= digest_size
= crypto_shash_digestsize(tfm
);
52 digest
= kzalloc(digest_size
+ desc_size
, GFP_KERNEL
);
56 desc
= digest
+ digest_size
;
58 desc
->flags
= CRYPTO_TFM_REQ_MAY_SLEEP
;
60 /* Digest the message [RFC2315 9.3] */
61 ret
= crypto_shash_init(desc
);
64 ret
= crypto_shash_finup(desc
, pkcs7
->data
, pkcs7
->data_len
, digest
);
67 pr_devel("MsgDigest = [%*ph]\n", 8, digest
);
69 /* However, if there are authenticated attributes, there must be a
70 * message digest attribute amongst them which corresponds to the
71 * digest we just calculated.
73 if (sinfo
->msgdigest
) {
76 if (sinfo
->msgdigest_len
!= sinfo
->sig
.digest_size
) {
77 pr_debug("Sig %u: Invalid digest size (%u)\n",
78 sinfo
->index
, sinfo
->msgdigest_len
);
83 if (memcmp(digest
, sinfo
->msgdigest
, sinfo
->msgdigest_len
) != 0) {
84 pr_debug("Sig %u: Message digest doesn't match\n",
90 /* We then calculate anew, using the authenticated attributes
91 * as the contents of the digest instead. Note that we need to
92 * convert the attributes from a CONT.0 into a SET before we
95 memset(digest
, 0, sinfo
->sig
.digest_size
);
97 ret
= crypto_shash_init(desc
);
100 tag
= ASN1_CONS_BIT
| ASN1_SET
;
101 ret
= crypto_shash_update(desc
, &tag
, 1);
104 ret
= crypto_shash_finup(desc
, sinfo
->authattrs
,
105 sinfo
->authattrs_len
, digest
);
108 pr_devel("AADigest = [%*ph]\n", 8, digest
);
111 sinfo
->sig
.digest
= digest
;
117 crypto_free_shash(tfm
);
118 kleave(" = %d", ret
);
123 * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
124 * uses the issuer's name and the issuing certificate serial number for
125 * matching purposes. These must match the certificate issuer's name (not
126 * subject's name) and the certificate serial number [RFC 2315 6.7].
128 static int pkcs7_find_key(struct pkcs7_message
*pkcs7
,
129 struct pkcs7_signed_info
*sinfo
)
131 struct x509_certificate
*x509
;
135 sinfo
->index
, sinfo
->raw_serial_size
, sinfo
->raw_issuer_size
);
137 for (x509
= pkcs7
->certs
; x509
; x509
= x509
->next
, certix
++) {
138 /* I'm _assuming_ that the generator of the PKCS#7 message will
139 * encode the fields from the X.509 cert in the same way in the
140 * PKCS#7 message - but I can't be 100% sure of that. It's
141 * possible this will need element-by-element comparison.
143 if (x509
->raw_serial_size
!= sinfo
->raw_serial_size
||
144 memcmp(x509
->raw_serial
, sinfo
->raw_serial
,
145 sinfo
->raw_serial_size
) != 0)
147 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
148 sinfo
->index
, certix
);
150 if (x509
->raw_issuer_size
!= sinfo
->raw_issuer_size
||
151 memcmp(x509
->raw_issuer
, sinfo
->raw_issuer
,
152 sinfo
->raw_issuer_size
) != 0) {
153 pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n",
158 if (x509
->pub
->pkey_algo
!= sinfo
->sig
.pkey_algo
) {
159 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
164 sinfo
->signer
= x509
;
167 pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n",
168 sinfo
->index
, sinfo
->raw_serial_size
, sinfo
->raw_serial
);
173 * Verify the internal certificate chain as best we can.
175 static int pkcs7_verify_sig_chain(struct pkcs7_message
*pkcs7
,
176 struct pkcs7_signed_info
*sinfo
)
178 struct x509_certificate
*x509
= sinfo
->signer
, *p
;
183 for (p
= pkcs7
->certs
; p
; p
= p
->next
)
187 pr_debug("verify %s: %s\n", x509
->subject
, x509
->fingerprint
);
189 ret
= x509_get_sig_params(x509
);
193 pr_debug("- issuer %s\n", x509
->issuer
);
195 pr_debug("- authkeyid %s\n", x509
->authority
);
197 if (!x509
->authority
||
198 strcmp(x509
->subject
, x509
->issuer
) == 0) {
199 /* If there's no authority certificate specified, then
200 * the certificate must be self-signed and is the root
201 * of the chain. Likewise if the cert is its own
204 pr_debug("- no auth?\n");
205 if (x509
->raw_subject_size
!= x509
->raw_issuer_size
||
206 memcmp(x509
->raw_subject
, x509
->raw_issuer
,
207 x509
->raw_issuer_size
) != 0)
210 ret
= x509_check_signature(x509
->pub
, x509
);
214 pr_debug("- self-signed\n");
218 /* Look through the X.509 certificates in the PKCS#7 message's
219 * list to see if the next one is there.
221 pr_debug("- want %s\n", x509
->authority
);
222 for (p
= pkcs7
->certs
; p
; p
= p
->next
) {
223 pr_debug("- cmp [%u] %s\n", p
->index
, p
->fingerprint
);
224 if (p
->raw_subject_size
== x509
->raw_issuer_size
&&
225 strcmp(p
->fingerprint
, x509
->authority
) == 0 &&
226 memcmp(p
->raw_subject
, x509
->raw_issuer
,
227 x509
->raw_issuer_size
) == 0)
231 /* We didn't find the root of this chain */
236 pr_debug("- issuer %s\n", p
->subject
);
238 pr_warn("Sig %u: X.509 chain contains loop\n",
242 ret
= x509_check_signature(p
->pub
, x509
);
247 pr_debug("- self-signed\n");
256 * Verify one signed information block from a PKCS#7 message.
258 static int pkcs7_verify_one(struct pkcs7_message
*pkcs7
,
259 struct pkcs7_signed_info
*sinfo
)
263 kenter(",%u", sinfo
->index
);
265 /* First of all, digest the data in the PKCS#7 message and the
266 * signed information block
268 ret
= pkcs7_digest(pkcs7
, sinfo
);
272 /* Find the key for the signature */
273 ret
= pkcs7_find_key(pkcs7
, sinfo
);
277 pr_devel("Using X.509[%u] for sig %u\n",
278 sinfo
->signer
->index
, sinfo
->index
);
280 /* Verify the PKCS#7 binary against the key */
281 ret
= public_key_verify_signature(sinfo
->signer
->pub
, &sinfo
->sig
);
285 pr_devel("Verified signature %u\n", sinfo
->index
);
287 /* Verify the internal certificate chain */
288 return pkcs7_verify_sig_chain(pkcs7
, sinfo
);
292 * pkcs7_verify - Verify a PKCS#7 message
293 * @pkcs7: The PKCS#7 message to be verified
295 int pkcs7_verify(struct pkcs7_message
*pkcs7
)
297 struct pkcs7_signed_info
*sinfo
;
298 struct x509_certificate
*x509
;
303 for (n
= 0, x509
= pkcs7
->certs
; x509
; x509
= x509
->next
, n
++) {
304 ret
= x509_get_sig_params(x509
);
307 pr_debug("X.509[%u] %s\n", n
, x509
->authority
);
310 for (sinfo
= pkcs7
->signed_infos
; sinfo
; sinfo
= sinfo
->next
) {
311 ret
= pkcs7_verify_one(pkcs7
, sinfo
);
313 kleave(" = %d", ret
);
321 EXPORT_SYMBOL_GPL(pkcs7_verify
);
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