1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Instantiate a public key crypto key from an X.509 Certificate
3 *
4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #define pr_fmt(fmt) "X.509: "fmt
9 #include <crypto/hash.h>
10 #include <crypto/sm2.h>
11 #include <keys/asymmetric-parser.h>
12 #include <keys/asymmetric-subtype.h>
13 #include <keys/system_keyring.h>
14 #include <linux/module.h>
15 #include <linux/kernel.h>
16 #include <linux/slab.h>
17 #include <linux/string.h>
18 #include "asymmetric_keys.h"
19 #include "x509_parser.h"
20
21 /*
22 * Set up the signature parameters in an X.509 certificate. This involves
23 * digesting the signed data and extracting the signature.
24 */
x509_get_sig_params(struct x509_certificate * cert)25 int x509_get_sig_params(struct x509_certificate *cert)
26 {
27 struct public_key_signature *sig = cert->sig;
28 struct crypto_shash *tfm;
29 struct shash_desc *desc;
30 size_t desc_size;
31 int ret;
32
33 pr_devel("==>%s()\n", __func__);
34
35 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
36 if (!sig->s)
37 return -ENOMEM;
38
39 sig->s_size = cert->raw_sig_size;
40
41 /* Allocate the hashing algorithm we're going to need and find out how
42 * big the hash operational data will be.
43 */
44 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
45 if (IS_ERR(tfm)) {
46 if (PTR_ERR(tfm) == -ENOENT) {
47 cert->unsupported_sig = true;
48 return 0;
49 }
50 return PTR_ERR(tfm);
51 }
52
53 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
54 sig->digest_size = crypto_shash_digestsize(tfm);
55
56 ret = -ENOMEM;
57 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
58 if (!sig->digest)
59 goto error;
60
61 desc = kzalloc(desc_size, GFP_KERNEL);
62 if (!desc)
63 goto error;
64
65 desc->tfm = tfm;
66
67 if (strcmp(cert->pub->pkey_algo, "sm2") == 0) {
68 ret = strcmp(sig->hash_algo, "sm3") != 0 ? -EINVAL :
69 crypto_shash_init(desc) ?:
70 sm2_compute_z_digest(desc, cert->pub->key,
71 cert->pub->keylen, sig->digest) ?:
72 crypto_shash_init(desc) ?:
73 crypto_shash_update(desc, sig->digest,
74 sig->digest_size) ?:
75 crypto_shash_finup(desc, cert->tbs, cert->tbs_size,
76 sig->digest);
77 } else {
78 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size,
79 sig->digest);
80 }
81
82 if (ret < 0)
83 goto error_2;
84
85 ret = is_hash_blacklisted(sig->digest, sig->digest_size,
86 BLACKLIST_HASH_X509_TBS);
87 if (ret == -EKEYREJECTED) {
88 pr_err("Cert %*phN is blacklisted\n",
89 sig->digest_size, sig->digest);
90 cert->blacklisted = true;
91 ret = 0;
92 }
93
94 error_2:
95 kfree(desc);
96 error:
97 crypto_free_shash(tfm);
98 pr_devel("<==%s() = %d\n", __func__, ret);
99 return ret;
100 }
101
102 /*
103 * Check for self-signedness in an X.509 cert and if found, check the signature
104 * immediately if we can.
105 */
x509_check_for_self_signed(struct x509_certificate * cert)106 int x509_check_for_self_signed(struct x509_certificate *cert)
107 {
108 int ret = 0;
109
110 pr_devel("==>%s()\n", __func__);
111
112 if (cert->raw_subject_size != cert->raw_issuer_size ||
113 memcmp(cert->raw_subject, cert->raw_issuer,
114 cert->raw_issuer_size) != 0)
115 goto not_self_signed;
116
117 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
118 /* If the AKID is present it may have one or two parts. If
119 * both are supplied, both must match.
120 */
121 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
122 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
123
124 if (!a && !b)
125 goto not_self_signed;
126
127 ret = -EKEYREJECTED;
128 if (((a && !b) || (b && !a)) &&
129 cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
130 goto out;
131 }
132
133 if (cert->unsupported_sig) {
134 ret = 0;
135 goto out;
136 }
137
138 ret = public_key_verify_signature(cert->pub, cert->sig);
139 if (ret < 0) {
140 if (ret == -ENOPKG) {
141 cert->unsupported_sig = true;
142 ret = 0;
143 }
144 goto out;
145 }
146
147 pr_devel("Cert Self-signature verified");
148 cert->self_signed = true;
149
150 out:
151 pr_devel("<==%s() = %d\n", __func__, ret);
152 return ret;
153
154 not_self_signed:
155 pr_devel("<==%s() = 0 [not]\n", __func__);
156 return 0;
157 }
158
159 /*
160 * Attempt to parse a data blob for a key as an X509 certificate.
161 */
x509_key_preparse(struct key_preparsed_payload * prep)162 static int x509_key_preparse(struct key_preparsed_payload *prep)
163 {
164 struct asymmetric_key_ids *kids;
165 struct x509_certificate *cert;
166 const char *q;
167 size_t srlen, sulen;
168 char *desc = NULL, *p;
169 int ret;
170
171 cert = x509_cert_parse(prep->data, prep->datalen);
172 if (IS_ERR(cert))
173 return PTR_ERR(cert);
174
175 pr_devel("Cert Issuer: %s\n", cert->issuer);
176 pr_devel("Cert Subject: %s\n", cert->subject);
177 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
178 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
179
180 cert->pub->id_type = "X509";
181
182 if (cert->unsupported_sig) {
183 public_key_signature_free(cert->sig);
184 cert->sig = NULL;
185 } else {
186 pr_devel("Cert Signature: %s + %s\n",
187 cert->sig->pkey_algo, cert->sig->hash_algo);
188 }
189
190 /* Don't permit addition of blacklisted keys */
191 ret = -EKEYREJECTED;
192 if (cert->blacklisted)
193 goto error_free_cert;
194
195 /* Propose a description */
196 sulen = strlen(cert->subject);
197 if (cert->raw_skid) {
198 srlen = cert->raw_skid_size;
199 q = cert->raw_skid;
200 } else {
201 srlen = cert->raw_serial_size;
202 q = cert->raw_serial;
203 }
204
205 ret = -ENOMEM;
206 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
207 if (!desc)
208 goto error_free_cert;
209 p = memcpy(desc, cert->subject, sulen);
210 p += sulen;
211 *p++ = ':';
212 *p++ = ' ';
213 p = bin2hex(p, q, srlen);
214 *p = 0;
215
216 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
217 if (!kids)
218 goto error_free_desc;
219 kids->id[0] = cert->id;
220 kids->id[1] = cert->skid;
221 kids->id[2] = asymmetric_key_generate_id(cert->raw_subject,
222 cert->raw_subject_size,
223 "", 0);
224 if (IS_ERR(kids->id[2])) {
225 ret = PTR_ERR(kids->id[2]);
226 goto error_free_kids;
227 }
228
229 /* We're pinning the module by being linked against it */
230 __module_get(public_key_subtype.owner);
231 prep->payload.data[asym_subtype] = &public_key_subtype;
232 prep->payload.data[asym_key_ids] = kids;
233 prep->payload.data[asym_crypto] = cert->pub;
234 prep->payload.data[asym_auth] = cert->sig;
235 prep->description = desc;
236 prep->quotalen = 100;
237
238 /* We've finished with the certificate */
239 cert->pub = NULL;
240 cert->id = NULL;
241 cert->skid = NULL;
242 cert->sig = NULL;
243 desc = NULL;
244 kids = NULL;
245 ret = 0;
246
247 error_free_kids:
248 kfree(kids);
249 error_free_desc:
250 kfree(desc);
251 error_free_cert:
252 x509_free_certificate(cert);
253 return ret;
254 }
255
256 static struct asymmetric_key_parser x509_key_parser = {
257 .owner = THIS_MODULE,
258 .name = "x509",
259 .parse = x509_key_preparse,
260 };
261
262 /*
263 * Module stuff
264 */
x509_key_init(void)265 static int __init x509_key_init(void)
266 {
267 return register_asymmetric_key_parser(&x509_key_parser);
268 }
269
x509_key_exit(void)270 static void __exit x509_key_exit(void)
271 {
272 unregister_asymmetric_key_parser(&x509_key_parser);
273 }
274
275 module_init(x509_key_init);
276 module_exit(x509_key_exit);
277
278 MODULE_DESCRIPTION("X.509 certificate parser");
279 MODULE_AUTHOR("Red Hat, Inc.");
280 MODULE_LICENSE("GPL");
281