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 <keys/asymmetric-parser.h>
11 #include <keys/asymmetric-subtype.h>
12 #include <keys/system_keyring.h>
13 #include <linux/hex.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 /* Calculate a SHA256 hash of the TBS and check it against the
36 * blacklist.
37 */
38 sha256(cert->tbs, cert->tbs_size, cert->sha256);
39 ret = is_hash_blacklisted(cert->sha256, sizeof(cert->sha256),
40 BLACKLIST_HASH_X509_TBS);
41 if (ret == -EKEYREJECTED) {
42 pr_err("Cert %*phN is blacklisted\n",
43 (int)sizeof(cert->sha256), cert->sha256);
44 cert->blacklisted = true;
45 ret = 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 if (sig->algo_takes_data) {
55 /* The signature algorithm does whatever passes for hashing. */
56 sig->m = (u8 *)cert->tbs;
57 sig->m_size = cert->tbs_size;
58 sig->m_free = false;
59 goto out;
60 }
61
62 /* Allocate the hashing algorithm we're going to need and find out how
63 * big the hash operational data will be.
64 */
65 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
66 if (IS_ERR(tfm)) {
67 if (PTR_ERR(tfm) == -ENOENT) {
68 cert->unsupported_sig = true;
69 return 0;
70 }
71 return PTR_ERR(tfm);
72 }
73
74 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
75 sig->m_size = crypto_shash_digestsize(tfm);
76
77 ret = -ENOMEM;
78 sig->m = kmalloc(sig->m_size, GFP_KERNEL);
79 if (!sig->m)
80 goto error;
81 sig->m_free = true;
82
83 desc = kzalloc(desc_size, GFP_KERNEL);
84 if (!desc)
85 goto error;
86
87 desc->tfm = tfm;
88
89 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->m);
90 if (ret < 0)
91 goto error_2;
92
93 error_2:
94 kfree(desc);
95 error:
96 crypto_free_shash(tfm);
97 out:
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 x509_certificate *cert __free(x509_free_certificate) = NULL;
165 struct asymmetric_key_ids *kids __free(kfree) = NULL;
166 char *p, *desc __free(kfree) = NULL;
167 const char *q;
168 size_t srlen, sulen;
169
170 cert = x509_cert_parse(prep->data, prep->datalen);
171 if (IS_ERR(cert))
172 return PTR_ERR(cert);
173
174 pr_devel("Cert Issuer: %s\n", cert->issuer);
175 pr_devel("Cert Subject: %s\n", cert->subject);
176 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
177 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
178
179 cert->pub->id_type = "X509";
180
181 if (cert->unsupported_sig) {
182 public_key_signature_free(cert->sig);
183 cert->sig = NULL;
184 } else {
185 pr_devel("Cert Signature: %s + %s\n",
186 cert->sig->pkey_algo, cert->sig->hash_algo);
187 }
188
189 /* Don't permit addition of blacklisted keys */
190 if (cert->blacklisted)
191 return -EKEYREJECTED;
192
193 /* Propose a description */
194 sulen = strlen(cert->subject);
195 if (cert->raw_skid) {
196 srlen = cert->raw_skid_size;
197 q = cert->raw_skid;
198 } else {
199 srlen = cert->raw_serial_size;
200 q = cert->raw_serial;
201 }
202
203 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
204 if (!desc)
205 return -ENOMEM;
206 p = memcpy(desc, cert->subject, sulen);
207 p += sulen;
208 *p++ = ':';
209 *p++ = ' ';
210 p = bin2hex(p, q, srlen);
211 *p = 0;
212
213 kids = kmalloc_obj(struct asymmetric_key_ids);
214 if (!kids)
215 return -ENOMEM;
216 kids->id[0] = cert->id;
217 kids->id[1] = cert->skid;
218 kids->id[2] = asymmetric_key_generate_id(cert->raw_subject,
219 cert->raw_subject_size,
220 "", 0);
221 if (IS_ERR(kids->id[2]))
222 return PTR_ERR(kids->id[2]);
223
224 /* We're pinning the module by being linked against it */
225 __module_get(public_key_subtype.owner);
226 prep->payload.data[asym_subtype] = &public_key_subtype;
227 prep->payload.data[asym_key_ids] = kids;
228 prep->payload.data[asym_crypto] = cert->pub;
229 prep->payload.data[asym_auth] = cert->sig;
230 prep->description = desc;
231 prep->quotalen = 100;
232
233 /* We've finished with the certificate */
234 cert->pub = NULL;
235 cert->id = NULL;
236 cert->skid = NULL;
237 cert->sig = NULL;
238 desc = NULL;
239 kids = NULL;
240 return 0;
241 }
242
243 static struct asymmetric_key_parser x509_key_parser = {
244 .owner = THIS_MODULE,
245 .name = "x509",
246 .parse = x509_key_preparse,
247 };
248
249 /*
250 * Module stuff
251 */
x509_key_init(void)252 static int __init x509_key_init(void)
253 {
254 return register_asymmetric_key_parser(&x509_key_parser);
255 }
256
x509_key_exit(void)257 static void __exit x509_key_exit(void)
258 {
259 unregister_asymmetric_key_parser(&x509_key_parser);
260 }
261
262 module_init(x509_key_init);
263 module_exit(x509_key_exit);
264
265 MODULE_DESCRIPTION("X.509 certificate parser");
266 MODULE_AUTHOR("Red Hat, Inc.");
267 MODULE_LICENSE("GPL");
268