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