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