1 /* Instantiate a public key crypto key from an X.509 Certificate
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) "X.509: "fmt
13 #include <linux/module.h>
14 #include <linux/kernel.h>
15 #include <linux/slab.h>
16 #include <linux/err.h>
17 #include <linux/mpi.h>
18 #include <linux/asn1_decoder.h>
19 #include <keys/asymmetric-subtype.h>
20 #include <keys/asymmetric-parser.h>
21 #include <keys/system_keyring.h>
22 #include <crypto/hash.h>
23 #include "asymmetric_keys.h"
24 #include "public_key.h"
25 #include "x509_parser.h"
28 * Find a key in the given keyring by issuer and authority.
30 static struct key
*x509_request_asymmetric_key(
32 const char *signer
, size_t signer_len
,
33 const char *authority
, size_t auth_len
)
38 /* Construct an identifier. */
39 id
= kmalloc(signer_len
+ 2 + auth_len
+ 1, GFP_KERNEL
);
41 return ERR_PTR(-ENOMEM
);
43 memcpy(id
, signer
, signer_len
);
44 id
[signer_len
+ 0] = ':';
45 id
[signer_len
+ 1] = ' ';
46 memcpy(id
+ signer_len
+ 2, authority
, auth_len
);
47 id
[signer_len
+ 2 + auth_len
] = 0;
49 pr_debug("Look up: \"%s\"\n", id
);
51 key
= keyring_search(make_key_ref(keyring
, 1),
52 &key_type_asymmetric
, id
);
54 pr_debug("Request for module key '%s' err %ld\n",
59 switch (PTR_ERR(key
)) {
60 /* Hide some search errors */
64 return ERR_PTR(-ENOKEY
);
70 pr_devel("<==%s() = 0 [%x]\n", __func__
, key_serial(key_ref_to_ptr(key
)));
71 return key_ref_to_ptr(key
);
75 * Set up the signature parameters in an X.509 certificate. This involves
76 * digesting the signed data and extracting the signature.
78 int x509_get_sig_params(struct x509_certificate
*cert
)
80 struct crypto_shash
*tfm
;
81 struct shash_desc
*desc
;
82 size_t digest_size
, desc_size
;
86 pr_devel("==>%s()\n", __func__
);
91 cert
->sig
.rsa
.s
= mpi_read_raw_data(cert
->raw_sig
, cert
->raw_sig_size
);
96 /* Allocate the hashing algorithm we're going to need and find out how
97 * big the hash operational data will be.
99 tfm
= crypto_alloc_shash(hash_algo_name
[cert
->sig
.pkey_hash_algo
], 0, 0);
101 return (PTR_ERR(tfm
) == -ENOENT
) ? -ENOPKG
: PTR_ERR(tfm
);
103 desc_size
= crypto_shash_descsize(tfm
) + sizeof(*desc
);
104 digest_size
= crypto_shash_digestsize(tfm
);
106 /* We allocate the hash operational data storage on the end of the
107 * digest storage space.
110 digest
= kzalloc(digest_size
+ desc_size
, GFP_KERNEL
);
114 cert
->sig
.digest
= digest
;
115 cert
->sig
.digest_size
= digest_size
;
117 desc
= digest
+ digest_size
;
119 desc
->flags
= CRYPTO_TFM_REQ_MAY_SLEEP
;
121 ret
= crypto_shash_init(desc
);
125 ret
= crypto_shash_finup(desc
, cert
->tbs
, cert
->tbs_size
, digest
);
127 crypto_free_shash(tfm
);
128 pr_devel("<==%s() = %d\n", __func__
, ret
);
131 EXPORT_SYMBOL_GPL(x509_get_sig_params
);
134 * Check the signature on a certificate using the provided public key
136 int x509_check_signature(const struct public_key
*pub
,
137 struct x509_certificate
*cert
)
141 pr_devel("==>%s()\n", __func__
);
143 ret
= x509_get_sig_params(cert
);
147 ret
= public_key_verify_signature(pub
, &cert
->sig
);
148 pr_debug("Cert Verification: %d\n", ret
);
151 EXPORT_SYMBOL_GPL(x509_check_signature
);
154 * Check the new certificate against the ones in the trust keyring. If one of
155 * those is the signing key and validates the new certificate, then mark the
156 * new certificate as being trusted.
158 * Return 0 if the new certificate was successfully validated, 1 if we couldn't
159 * find a matching parent certificate in the trusted list and an error if there
160 * is a matching certificate but the signature check fails.
162 static int x509_validate_trust(struct x509_certificate
*cert
,
163 struct key
*trust_keyring
)
165 const struct public_key
*pk
;
169 key
= x509_request_asymmetric_key(trust_keyring
,
170 cert
->issuer
, strlen(cert
->issuer
),
172 strlen(cert
->authority
));
174 pk
= key
->payload
.data
;
175 ret
= x509_check_signature(pk
, cert
);
181 * Attempt to parse a data blob for a key as an X509 certificate.
183 static int x509_key_preparse(struct key_preparsed_payload
*prep
)
185 struct x509_certificate
*cert
;
190 cert
= x509_cert_parse(prep
->data
, prep
->datalen
);
192 return PTR_ERR(cert
);
194 pr_devel("Cert Issuer: %s\n", cert
->issuer
);
195 pr_devel("Cert Subject: %s\n", cert
->subject
);
197 if (cert
->pub
->pkey_algo
>= PKEY_ALGO__LAST
||
198 cert
->sig
.pkey_algo
>= PKEY_ALGO__LAST
||
199 cert
->sig
.pkey_hash_algo
>= PKEY_HASH__LAST
||
200 !pkey_algo
[cert
->pub
->pkey_algo
] ||
201 !pkey_algo
[cert
->sig
.pkey_algo
] ||
202 !hash_algo_name
[cert
->sig
.pkey_hash_algo
]) {
204 goto error_free_cert
;
207 pr_devel("Cert Key Algo: %s\n", pkey_algo_name
[cert
->pub
->pkey_algo
]);
208 pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
209 cert
->valid_from
.tm_year
+ 1900, cert
->valid_from
.tm_mon
+ 1,
210 cert
->valid_from
.tm_mday
, cert
->valid_from
.tm_hour
,
211 cert
->valid_from
.tm_min
, cert
->valid_from
.tm_sec
);
212 pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
213 cert
->valid_to
.tm_year
+ 1900, cert
->valid_to
.tm_mon
+ 1,
214 cert
->valid_to
.tm_mday
, cert
->valid_to
.tm_hour
,
215 cert
->valid_to
.tm_min
, cert
->valid_to
.tm_sec
);
216 pr_devel("Cert Signature: %s + %s\n",
217 pkey_algo_name
[cert
->sig
.pkey_algo
],
218 hash_algo_name
[cert
->sig
.pkey_hash_algo
]);
220 if (!cert
->fingerprint
) {
221 pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
224 goto error_free_cert
;
227 cert
->pub
->algo
= pkey_algo
[cert
->pub
->pkey_algo
];
228 cert
->pub
->id_type
= PKEY_ID_X509
;
230 /* Check the signature on the key if it appears to be self-signed */
231 if (!cert
->authority
||
232 strcmp(cert
->fingerprint
, cert
->authority
) == 0) {
233 ret
= x509_check_signature(cert
->pub
, cert
); /* self-signed */
235 goto error_free_cert
;
237 ret
= x509_validate_trust(cert
, system_trusted_keyring
);
242 /* Propose a description */
243 sulen
= strlen(cert
->subject
);
244 srlen
= strlen(cert
->fingerprint
);
246 desc
= kmalloc(sulen
+ 2 + srlen
+ 1, GFP_KERNEL
);
248 goto error_free_cert
;
249 memcpy(desc
, cert
->subject
, sulen
);
251 desc
[sulen
+ 1] = ' ';
252 memcpy(desc
+ sulen
+ 2, cert
->fingerprint
, srlen
);
253 desc
[sulen
+ 2 + srlen
] = 0;
255 /* We're pinning the module by being linked against it */
256 __module_get(public_key_subtype
.owner
);
257 prep
->type_data
[0] = &public_key_subtype
;
258 prep
->type_data
[1] = cert
->fingerprint
;
259 prep
->payload
= cert
->pub
;
260 prep
->description
= desc
;
261 prep
->quotalen
= 100;
263 /* We've finished with the certificate */
265 cert
->fingerprint
= NULL
;
270 x509_free_certificate(cert
);
274 static struct asymmetric_key_parser x509_key_parser
= {
275 .owner
= THIS_MODULE
,
277 .parse
= x509_key_preparse
,
283 static int __init
x509_key_init(void)
285 return register_asymmetric_key_parser(&x509_key_parser
);
288 static void __exit
x509_key_exit(void)
290 unregister_asymmetric_key_parser(&x509_key_parser
);
293 module_init(x509_key_init
);
294 module_exit(x509_key_exit
);
296 MODULE_DESCRIPTION("X.509 certificate parser");
297 MODULE_LICENSE("GPL");