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"
27 static bool use_builtin_keys;
28 static char *ca_keyid;
31 static int __init ca_keys_setup(char *str)
33 if (!str) /* default system keyring */
36 if (strncmp(str, "id:", 3) == 0)
37 ca_keyid = str; /* owner key 'id:xxxxxx' */
38 else if (strcmp(str, "builtin") == 0)
39 use_builtin_keys = true;
43 __setup("ca_keys=", ca_keys_setup);
47 * Find a key in the given keyring by issuer and authority.
49 static struct key *x509_request_asymmetric_key(struct key *keyring,
52 const char *authority,
58 /* Construct an identifier. */
59 id = kmalloc(signer_len + 2 + auth_len + 1, GFP_KERNEL);
61 return ERR_PTR(-ENOMEM);
63 memcpy(id, signer, signer_len);
64 id[signer_len + 0] = ':';
65 id[signer_len + 1] = ' ';
66 memcpy(id + signer_len + 2, authority, auth_len);
67 id[signer_len + 2 + auth_len] = 0;
69 pr_debug("Look up: \"%s\"\n", id);
71 key = keyring_search(make_key_ref(keyring, 1),
72 &key_type_asymmetric, id);
74 pr_debug("Request for module key '%s' err %ld\n",
79 switch (PTR_ERR(key)) {
80 /* Hide some search errors */
84 return ERR_PTR(-ENOKEY);
90 pr_devel("<==%s() = 0 [%x]\n", __func__,
91 key_serial(key_ref_to_ptr(key)));
92 return key_ref_to_ptr(key);
96 * Set up the signature parameters in an X.509 certificate. This involves
97 * digesting the signed data and extracting the signature.
99 int x509_get_sig_params(struct x509_certificate *cert)
101 struct crypto_shash *tfm;
102 struct shash_desc *desc;
103 size_t digest_size, desc_size;
107 pr_devel("==>%s()\n", __func__);
112 cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
113 if (!cert->sig.rsa.s)
115 cert->sig.nr_mpi = 1;
117 /* Allocate the hashing algorithm we're going to need and find out how
118 * big the hash operational data will be.
120 tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
122 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
124 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
125 digest_size = crypto_shash_digestsize(tfm);
127 /* We allocate the hash operational data storage on the end of the
128 * digest storage space.
131 digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
135 cert->sig.digest = digest;
136 cert->sig.digest_size = digest_size;
138 desc = digest + digest_size;
140 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
142 ret = crypto_shash_init(desc);
146 ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
148 crypto_free_shash(tfm);
149 pr_devel("<==%s() = %d\n", __func__, ret);
152 EXPORT_SYMBOL_GPL(x509_get_sig_params);
155 * Check the signature on a certificate using the provided public key
157 int x509_check_signature(const struct public_key *pub,
158 struct x509_certificate *cert)
162 pr_devel("==>%s()\n", __func__);
164 ret = x509_get_sig_params(cert);
168 ret = public_key_verify_signature(pub, &cert->sig);
169 pr_debug("Cert Verification: %d\n", ret);
172 EXPORT_SYMBOL_GPL(x509_check_signature);
175 * Check the new certificate against the ones in the trust keyring. If one of
176 * those is the signing key and validates the new certificate, then mark the
177 * new certificate as being trusted.
179 * Return 0 if the new certificate was successfully validated, 1 if we couldn't
180 * find a matching parent certificate in the trusted list and an error if there
181 * is a matching certificate but the signature check fails.
183 static int x509_validate_trust(struct x509_certificate *cert,
184 struct key *trust_keyring)
192 if (ca_keyid && !asymmetric_keyid_match(cert->authority, ca_keyid))
195 key = x509_request_asymmetric_key(trust_keyring,
196 cert->issuer, strlen(cert->issuer),
198 strlen(cert->authority));
200 if (!use_builtin_keys
201 || test_bit(KEY_FLAG_BUILTIN, &key->flags))
202 ret = x509_check_signature(key->payload.data, cert);
209 * Attempt to parse a data blob for a key as an X509 certificate.
211 static int x509_key_preparse(struct key_preparsed_payload *prep)
213 struct x509_certificate *cert;
218 cert = x509_cert_parse(prep->data, prep->datalen);
220 return PTR_ERR(cert);
222 pr_devel("Cert Issuer: %s\n", cert->issuer);
223 pr_devel("Cert Subject: %s\n", cert->subject);
225 if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
226 cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
227 cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
228 !pkey_algo[cert->pub->pkey_algo] ||
229 !pkey_algo[cert->sig.pkey_algo] ||
230 !hash_algo_name[cert->sig.pkey_hash_algo]) {
232 goto error_free_cert;
235 pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
236 pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
237 cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
238 cert->valid_from.tm_mday, cert->valid_from.tm_hour,
239 cert->valid_from.tm_min, cert->valid_from.tm_sec);
240 pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
241 cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
242 cert->valid_to.tm_mday, cert->valid_to.tm_hour,
243 cert->valid_to.tm_min, cert->valid_to.tm_sec);
244 pr_devel("Cert Signature: %s + %s\n",
245 pkey_algo_name[cert->sig.pkey_algo],
246 hash_algo_name[cert->sig.pkey_hash_algo]);
248 if (!cert->fingerprint) {
249 pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
252 goto error_free_cert;
255 cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
256 cert->pub->id_type = PKEY_ID_X509;
258 /* Check the signature on the key if it appears to be self-signed */
259 if (!cert->authority ||
260 strcmp(cert->fingerprint, cert->authority) == 0) {
261 ret = x509_check_signature(cert->pub, cert); /* self-signed */
263 goto error_free_cert;
264 } else if (!prep->trusted) {
265 ret = x509_validate_trust(cert, get_system_trusted_keyring());
270 /* Propose a description */
271 sulen = strlen(cert->subject);
272 srlen = strlen(cert->fingerprint);
274 desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
276 goto error_free_cert;
277 memcpy(desc, cert->subject, sulen);
279 desc[sulen + 1] = ' ';
280 memcpy(desc + sulen + 2, cert->fingerprint, srlen);
281 desc[sulen + 2 + srlen] = 0;
283 /* We're pinning the module by being linked against it */
284 __module_get(public_key_subtype.owner);
285 prep->type_data[0] = &public_key_subtype;
286 prep->type_data[1] = cert->fingerprint;
287 prep->payload[0] = cert->pub;
288 prep->description = desc;
289 prep->quotalen = 100;
291 /* We've finished with the certificate */
293 cert->fingerprint = NULL;
298 x509_free_certificate(cert);
302 static struct asymmetric_key_parser x509_key_parser = {
303 .owner = THIS_MODULE,
305 .parse = x509_key_preparse,
311 static int __init x509_key_init(void)
313 return register_asymmetric_key_parser(&x509_key_parser);
316 static void __exit x509_key_exit(void)
318 unregister_asymmetric_key_parser(&x509_key_parser);
321 module_init(x509_key_init);
322 module_exit(x509_key_exit);
324 MODULE_DESCRIPTION("X.509 certificate parser");
325 MODULE_LICENSE("GPL");