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 */
25int 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
94error_2:
95	kfree(desc);
96error:
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 */
106int 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
150out:
151	pr_devel("<==%s() = %d\n", __func__, ret);
152	return ret;
153
154not_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 */
162static 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
247error_free_kids:
248	kfree(kids);
249error_free_desc:
250	kfree(desc);
251error_free_cert:
252	x509_free_certificate(cert);
253	return ret;
254}
255
256static 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 */
265static int __init x509_key_init(void)
266{
267	return register_asymmetric_key_parser(&x509_key_parser);
268}
269
270static void __exit x509_key_exit(void)
271{
272	unregister_asymmetric_key_parser(&x509_key_parser);
273}
274
275module_init(x509_key_init);
276module_exit(x509_key_exit);
277
278MODULE_DESCRIPTION("X.509 certificate parser");
279MODULE_AUTHOR("Red Hat, Inc.");
280MODULE_LICENSE("GPL");
281