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 public_key_signature
*sig
= sinfo
->sig
;
29 struct crypto_shash
*tfm
;
30 struct shash_desc
*desc
;
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 sig
->digest_size
= crypto_shash_digestsize(tfm
);
50 sig
->digest
= kmalloc(sig
->digest_size
, GFP_KERNEL
);
54 desc
= kzalloc(desc_size
, GFP_KERNEL
);
59 desc
->flags
= CRYPTO_TFM_REQ_MAY_SLEEP
;
61 /* Digest the message [RFC2315 9.3] */
62 ret
= crypto_shash_init(desc
);
65 ret
= crypto_shash_finup(desc
, pkcs7
->data
, pkcs7
->data_len
,
69 pr_devel("MsgDigest = [%*ph]\n", 8, sig
->digest
);
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.
75 if (sinfo
->authattrs
) {
78 if (!sinfo
->msgdigest
) {
79 pr_warn("Sig %u: No messageDigest\n", sinfo
->index
);
84 if (sinfo
->msgdigest_len
!= sig
->digest_size
) {
85 pr_debug("Sig %u: Invalid digest size (%u)\n",
86 sinfo
->index
, sinfo
->msgdigest_len
);
91 if (memcmp(sig
->digest
, sinfo
->msgdigest
,
92 sinfo
->msgdigest_len
) != 0) {
93 pr_debug("Sig %u: Message digest doesn't match\n",
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
104 memset(sig
->digest
, 0, sig
->digest_size
);
106 ret
= crypto_shash_init(desc
);
109 tag
= ASN1_CONS_BIT
| ASN1_SET
;
110 ret
= crypto_shash_update(desc
, &tag
, 1);
113 ret
= crypto_shash_finup(desc
, sinfo
->authattrs
,
114 sinfo
->authattrs_len
, sig
->digest
);
117 pr_devel("AADigest = [%*ph]\n", 8, sig
->digest
);
123 crypto_free_shash(tfm
);
124 kleave(" = %d", ret
);
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].
134 static int pkcs7_find_key(struct pkcs7_message
*pkcs7
,
135 struct pkcs7_signed_info
*sinfo
)
137 struct x509_certificate
*x509
;
140 kenter("%u", sinfo
->index
);
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.
148 if (!asymmetric_key_id_same(x509
->id
, sinfo
->sig
->auth_ids
[0]))
150 pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
151 sinfo
->index
, certix
);
153 if (x509
->pub
->pkey_algo
!= sinfo
->sig
->pkey_algo
) {
154 pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
159 sinfo
->signer
= x509
;
163 /* The relevant X.509 cert isn't found here, but it might be found in
166 pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
168 sinfo
->sig
->auth_ids
[0]->len
, sinfo
->sig
->auth_ids
[0]->data
);
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 public_key_signature
*sig
;
179 struct x509_certificate
*x509
= sinfo
->signer
, *p
;
180 struct asymmetric_key_id
*auth
;
185 for (p
= pkcs7
->certs
; p
; p
= p
->next
)
189 pr_debug("verify %s: %*phN\n",
191 x509
->raw_serial_size
, x509
->raw_serial
);
194 if (x509
->blacklisted
) {
195 /* If this cert is blacklisted, then mark everything
196 * that depends on this as blacklisted too.
198 sinfo
->blacklisted
= true;
199 for (p
= sinfo
->signer
; p
!= x509
; p
= p
->signer
)
200 p
->blacklisted
= true;
201 pr_debug("- blacklisted\n");
205 if (x509
->unsupported_key
)
206 goto unsupported_crypto_in_x509
;
208 pr_debug("- issuer %s\n", x509
->issuer
);
210 if (sig
->auth_ids
[0])
211 pr_debug("- authkeyid.id %*phN\n",
212 sig
->auth_ids
[0]->len
, sig
->auth_ids
[0]->data
);
213 if (sig
->auth_ids
[1])
214 pr_debug("- authkeyid.skid %*phN\n",
215 sig
->auth_ids
[1]->len
, sig
->auth_ids
[1]->data
);
217 if (x509
->self_signed
) {
218 /* If there's no authority certificate specified, then
219 * the certificate must be self-signed and is the root
220 * of the chain. Likewise if the cert is its own
223 if (x509
->unsupported_sig
)
224 goto unsupported_crypto_in_x509
;
226 pr_debug("- self-signed\n");
230 /* Look through the X.509 certificates in the PKCS#7 message's
231 * list to see if the next one is there.
233 auth
= sig
->auth_ids
[0];
235 pr_debug("- want %*phN\n", auth
->len
, auth
->data
);
236 for (p
= pkcs7
->certs
; p
; p
= p
->next
) {
237 pr_debug("- cmp [%u] %*phN\n",
238 p
->index
, p
->id
->len
, p
->id
->data
);
239 if (asymmetric_key_id_same(p
->id
, auth
))
240 goto found_issuer_check_skid
;
242 } else if (sig
->auth_ids
[1]) {
243 auth
= sig
->auth_ids
[1];
244 pr_debug("- want %*phN\n", auth
->len
, auth
->data
);
245 for (p
= pkcs7
->certs
; p
; p
= p
->next
) {
248 pr_debug("- cmp [%u] %*phN\n",
249 p
->index
, p
->skid
->len
, p
->skid
->data
);
250 if (asymmetric_key_id_same(p
->skid
, auth
))
255 /* We didn't find the root of this chain */
259 found_issuer_check_skid
:
260 /* We matched issuer + serialNumber, but if there's an
261 * authKeyId.keyId, that must match the CA subjKeyId also.
263 if (sig
->auth_ids
[1] &&
264 !asymmetric_key_id_same(p
->skid
, sig
->auth_ids
[1])) {
265 pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
266 sinfo
->index
, x509
->index
, p
->index
);
267 return -EKEYREJECTED
;
270 pr_debug("- subject %s\n", p
->subject
);
272 pr_warn("Sig %u: X.509 chain contains loop\n",
276 ret
= public_key_verify_signature(p
->pub
, p
->sig
);
281 pr_debug("- self-signed\n");
288 unsupported_crypto_in_x509
:
289 /* Just prune the certificate chain at this point if we lack some
290 * crypto module to go further. Note, however, we don't want to set
291 * sinfo->unsupported_crypto as the signed info block may still be
292 * validatable against an X.509 cert lower in the chain that we have a
299 * Verify one signed information block from a PKCS#7 message.
301 static int pkcs7_verify_one(struct pkcs7_message
*pkcs7
,
302 struct pkcs7_signed_info
*sinfo
)
306 kenter(",%u", sinfo
->index
);
308 /* First of all, digest the data in the PKCS#7 message and the
309 * signed information block
311 ret
= pkcs7_digest(pkcs7
, sinfo
);
315 /* Find the key for the signature if there is one */
316 ret
= pkcs7_find_key(pkcs7
, sinfo
);
323 pr_devel("Using X.509[%u] for sig %u\n",
324 sinfo
->signer
->index
, sinfo
->index
);
326 /* Check that the PKCS#7 signing time is valid according to the X.509
327 * certificate. We can't, however, check against the system clock
328 * since that may not have been set yet and may be wrong.
330 if (test_bit(sinfo_has_signing_time
, &sinfo
->aa_set
)) {
331 if (sinfo
->signing_time
< sinfo
->signer
->valid_from
||
332 sinfo
->signing_time
> sinfo
->signer
->valid_to
) {
333 pr_warn("Message signed outside of X.509 validity window\n");
334 return -EKEYREJECTED
;
338 /* Verify the PKCS#7 binary against the key */
339 ret
= public_key_verify_signature(sinfo
->signer
->pub
, sinfo
->sig
);
343 pr_devel("Verified signature %u\n", sinfo
->index
);
345 /* Verify the internal certificate chain */
346 return pkcs7_verify_sig_chain(pkcs7
, sinfo
);
350 * pkcs7_verify - Verify a PKCS#7 message
351 * @pkcs7: The PKCS#7 message to be verified
352 * @usage: The use to which the key is being put
354 * Verify a PKCS#7 message is internally consistent - that is, the data digest
355 * matches the digest in the AuthAttrs and any signature in the message or one
356 * of the X.509 certificates it carries that matches another X.509 cert in the
357 * message can be verified.
359 * This does not look to match the contents of the PKCS#7 message against any
360 * external public keys.
362 * Returns, in order of descending priority:
364 * (*) -EKEYREJECTED if a key was selected that had a usage restriction at
365 * odds with the specified usage, or:
367 * (*) -EKEYREJECTED if a signature failed to match for which we found an
368 * appropriate X.509 certificate, or:
370 * (*) -EBADMSG if some part of the message was invalid, or:
372 * (*) 0 if no signature chains were found to be blacklisted or to contain
373 * unsupported crypto, or:
375 * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
377 * (*) -ENOPKG if none of the signature chains are verifiable because suitable
378 * crypto modules couldn't be found.
380 int pkcs7_verify(struct pkcs7_message
*pkcs7
,
381 enum key_being_used_for usage
)
383 struct pkcs7_signed_info
*sinfo
;
384 int actual_ret
= -ENOPKG
;
390 case VERIFYING_MODULE_SIGNATURE
:
391 if (pkcs7
->data_type
!= OID_data
) {
392 pr_warn("Invalid module sig (not pkcs7-data)\n");
393 return -EKEYREJECTED
;
395 if (pkcs7
->have_authattrs
) {
396 pr_warn("Invalid module sig (has authattrs)\n");
397 return -EKEYREJECTED
;
400 case VERIFYING_FIRMWARE_SIGNATURE
:
401 if (pkcs7
->data_type
!= OID_data
) {
402 pr_warn("Invalid firmware sig (not pkcs7-data)\n");
403 return -EKEYREJECTED
;
405 if (!pkcs7
->have_authattrs
) {
406 pr_warn("Invalid firmware sig (missing authattrs)\n");
407 return -EKEYREJECTED
;
410 case VERIFYING_KEXEC_PE_SIGNATURE
:
411 if (pkcs7
->data_type
!= OID_msIndirectData
) {
412 pr_warn("Invalid kexec sig (not Authenticode)\n");
413 return -EKEYREJECTED
;
415 /* Authattr presence checked in parser */
417 case VERIFYING_UNSPECIFIED_SIGNATURE
:
418 if (pkcs7
->data_type
!= OID_data
) {
419 pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
420 return -EKEYREJECTED
;
427 for (sinfo
= pkcs7
->signed_infos
; sinfo
; sinfo
= sinfo
->next
) {
428 ret
= pkcs7_verify_one(pkcs7
, sinfo
);
429 if (sinfo
->blacklisted
&& actual_ret
== -ENOPKG
)
430 actual_ret
= -EKEYREJECTED
;
432 if (ret
== -ENOPKG
) {
433 sinfo
->unsupported_crypto
= true;
436 kleave(" = %d", ret
);
442 kleave(" = %d", actual_ret
);
445 EXPORT_SYMBOL_GPL(pkcs7_verify
);
448 * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
449 * @pkcs7: The PKCS#7 message
450 * @data: The data to be verified
451 * @datalen: The amount of data
453 * Supply the detached data needed to verify a PKCS#7 message. Note that no
454 * attempt to retain/pin the data is made. That is left to the caller. The
455 * data will not be modified by pkcs7_verify() and will not be freed when the
456 * PKCS#7 message is freed.
458 * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
460 int pkcs7_supply_detached_data(struct pkcs7_message
*pkcs7
,
461 const void *data
, size_t datalen
)
464 pr_debug("Data already supplied\n");
468 pkcs7
->data_len
= datalen
;