summaryrefslogtreecommitdiffstats
path: root/crypto/asymmetric_keys/x509_public_key.c
blob: ae450eb8be144fbe41596d75d04f811ff6864521 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
// SPDX-License-Identifier: GPL-2.0-or-later
/* Instantiate a public key crypto key from an X.509 Certificate
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) "X.509: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <keys/asymmetric-subtype.h>
#include <keys/asymmetric-parser.h>
#include <keys/system_keyring.h>
#include <crypto/hash.h>
#include "asymmetric_keys.h"
#include "x509_parser.h"

/*
 * Set up the signature parameters in an X.509 certificate.  This involves
 * digesting the signed data and extracting the signature.
 */
int x509_get_sig_params(struct x509_certificate *cert)
{
	struct public_key_signature *sig = cert->sig;
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t desc_size;
	int ret;

	pr_devel("==>%s()\n", __func__);

	sig->data = cert->tbs;
	sig->data_size = cert->tbs_size;

	if (!cert->pub->pkey_algo)
		cert->unsupported_key = true;

	if (!sig->pkey_algo)
		cert->unsupported_sig = true;

	/* We check the hash if we can - even if we can't then verify it */
	if (!sig->hash_algo) {
		cert->unsupported_sig = true;
		return 0;
	}

	sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
	if (!sig->s)
		return -ENOMEM;

	sig->s_size = cert->raw_sig_size;

	/* Allocate the hashing algorithm we're going to need and find out how
	 * big the hash operational data will be.
	 */
	tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
	if (IS_ERR(tfm)) {
		if (PTR_ERR(tfm) == -ENOENT) {
			cert->unsupported_sig = true;
			return 0;
		}
		return PTR_ERR(tfm);
	}

	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
	sig->digest_size = crypto_shash_digestsize(tfm);

	ret = -ENOMEM;
	sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
	if (!sig->digest)
		goto error;

	desc = kzalloc(desc_size, GFP_KERNEL);
	if (!desc)
		goto error;

	desc->tfm = tfm;

	ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
	if (ret < 0)
		goto error_2;

	ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
	if (ret == -EKEYREJECTED) {
		pr_err("Cert %*phN is blacklisted\n",
		       sig->digest_size, sig->digest);
		cert->blacklisted = true;
		ret = 0;
	}

error_2:
	kfree(desc);
error:
	crypto_free_shash(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
}

/*
 * Check for self-signedness in an X.509 cert and if found, check the signature
 * immediately if we can.
 */
int x509_check_for_self_signed(struct x509_certificate *cert)
{
	int ret = 0;

	pr_devel("==>%s()\n", __func__);

	if (cert->raw_subject_size != cert->raw_issuer_size ||
	    memcmp(cert->raw_subject, cert->raw_issuer,
		   cert->raw_issuer_size) != 0)
		goto not_self_signed;

	if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
		/* If the AKID is present it may have one or two parts.  If
		 * both are supplied, both must match.
		 */
		bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
		bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);

		if (!a && !b)
			goto not_self_signed;

		ret = -EKEYREJECTED;
		if (((a && !b) || (b && !a)) &&
		    cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
			goto out;
	}

	ret = -EKEYREJECTED;
	if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
		goto out;

	ret = public_key_verify_signature(cert->pub, cert->sig);
	if (ret < 0) {
		if (ret == -ENOPKG) {
			cert->unsupported_sig = true;
			ret = 0;
		}
		goto out;
	}

	pr_devel("Cert Self-signature verified");
	cert->self_signed = true;

out:
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;

not_self_signed:
	pr_devel("<==%s() = 0 [not]\n", __func__);
	return 0;
}

/*
 * Attempt to parse a data blob for a key as an X509 certificate.
 */
static int x509_key_preparse(struct key_preparsed_payload *prep)
{
	struct asymmetric_key_ids *kids;
	struct x509_certificate *cert;
	const char *q;
	size_t srlen, sulen;
	char *desc = NULL, *p;
	int ret;

	cert = x509_cert_parse(prep->data, prep->datalen);
	if (IS_ERR(cert))
		return PTR_ERR(cert);

	pr_devel("Cert Issuer: %s\n", cert->issuer);
	pr_devel("Cert Subject: %s\n", cert->subject);

	if (cert->unsupported_key) {
		ret = -ENOPKG;
		goto error_free_cert;
	}

	pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
	pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);

	cert->pub->id_type = "X509";

	if (cert->unsupported_sig) {
		public_key_signature_free(cert->sig);
		cert->sig = NULL;
	} else {
		pr_devel("Cert Signature: %s + %s\n",
			 cert->sig->pkey_algo, cert->sig->hash_algo);
	}

	/* Don't permit addition of blacklisted keys */
	ret = -EKEYREJECTED;
	if (cert->blacklisted)
		goto error_free_cert;

	/* Propose a description */
	sulen = strlen(cert->subject);
	if (cert->raw_skid) {
		srlen = cert->raw_skid_size;
		q = cert->raw_skid;
	} else {
		srlen = cert->raw_serial_size;
		q = cert->raw_serial;
	}

	ret = -ENOMEM;
	desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
	if (!desc)
		goto error_free_cert;
	p = memcpy(desc, cert->subject, sulen);
	p += sulen;
	*p++ = ':';
	*p++ = ' ';
	p = bin2hex(p, q, srlen);
	*p = 0;

	kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
	if (!kids)
		goto error_free_desc;
	kids->id[0] = cert->id;
	kids->id[1] = cert->skid;

	/* We're pinning the module by being linked against it */
	__module_get(public_key_subtype.owner);
	prep->payload.data[asym_subtype] = &public_key_subtype;
	prep->payload.data[asym_key_ids] = kids;
	prep->payload.data[asym_crypto] = cert->pub;
	prep->payload.data[asym_auth] = cert->sig;
	prep->description = desc;
	prep->quotalen = 100;

	/* We've finished with the certificate */
	cert->pub = NULL;
	cert->id = NULL;
	cert->skid = NULL;
	cert->sig = NULL;
	desc = NULL;
	ret = 0;

error_free_desc:
	kfree(desc);
error_free_cert:
	x509_free_certificate(cert);
	return ret;
}

static struct asymmetric_key_parser x509_key_parser = {
	.owner	= THIS_MODULE,
	.name	= "x509",
	.parse	= x509_key_preparse,
};

/*
 * Module stuff
 */
static int __init x509_key_init(void)
{
	return register_asymmetric_key_parser(&x509_key_parser);
}

static void __exit x509_key_exit(void)
{
	unregister_asymmetric_key_parser(&x509_key_parser);
}

module_init(x509_key_init);
module_exit(x509_key_exit);

MODULE_DESCRIPTION("X.509 certificate parser");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");