summaryrefslogtreecommitdiffstats
path: root/crypto/asymmetric_keys/pkcs7_verify.c
blob: 51ff36f3a9131e12584c93097900e40b4c1cfc3a (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
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
/* Verify the signature on a PKCS#7 message.
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define pr_fmt(fmt) "PKCS7: "fmt
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/asn1.h>
#include <crypto/hash.h>
#include "public_key.h"
#include "pkcs7_parser.h"

/*
 * Digest the relevant parts of the PKCS#7 data
 */
static int pkcs7_digest(struct pkcs7_message *pkcs7,
			struct pkcs7_signed_info *sinfo)
{
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t digest_size, desc_size;
	void *digest;
	int ret;

	kenter(",%u,%u", sinfo->index, sinfo->sig.pkey_hash_algo);

	if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
	    !hash_algo_name[sinfo->sig.pkey_hash_algo])
		return -ENOPKG;

	/* Allocate the hashing algorithm we're going to need and find out how
	 * big the hash operational data will be.
	 */
	tfm = crypto_alloc_shash(hash_algo_name[sinfo->sig.pkey_hash_algo],
				 0, 0);
	if (IS_ERR(tfm))
		return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);

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

	ret = -ENOMEM;
	digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
	if (!digest)
		goto error_no_desc;

	desc = digest + digest_size;
	desc->tfm   = tfm;
	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

	/* Digest the message [RFC2315 9.3] */
	ret = crypto_shash_init(desc);
	if (ret < 0)
		goto error;
	ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest);
	if (ret < 0)
		goto error;
	pr_devel("MsgDigest = [%*ph]\n", 8, digest);

	/* However, if there are authenticated attributes, there must be a
	 * message digest attribute amongst them which corresponds to the
	 * digest we just calculated.
	 */
	if (sinfo->msgdigest) {
		u8 tag;

		if (sinfo->msgdigest_len != sinfo->sig.digest_size) {
			pr_debug("Sig %u: Invalid digest size (%u)\n",
				 sinfo->index, sinfo->msgdigest_len);
			ret = -EBADMSG;
			goto error;
		}

		if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) {
			pr_debug("Sig %u: Message digest doesn't match\n",
				 sinfo->index);
			ret = -EKEYREJECTED;
			goto error;
		}

		/* We then calculate anew, using the authenticated attributes
		 * as the contents of the digest instead.  Note that we need to
		 * convert the attributes from a CONT.0 into a SET before we
		 * hash it.
		 */
		memset(digest, 0, sinfo->sig.digest_size);

		ret = crypto_shash_init(desc);
		if (ret < 0)
			goto error;
		tag = ASN1_CONS_BIT | ASN1_SET;
		ret = crypto_shash_update(desc, &tag, 1);
		if (ret < 0)
			goto error;
		ret = crypto_shash_finup(desc, sinfo->authattrs,
					 sinfo->authattrs_len, digest);
		if (ret < 0)
			goto error;
		pr_devel("AADigest = [%*ph]\n", 8, digest);
	}

	sinfo->sig.digest = digest;
	digest = NULL;

error:
	kfree(digest);
error_no_desc:
	crypto_free_shash(tfm);
	kleave(" = %d", ret);
	return ret;
}

/*
 * Find the key (X.509 certificate) to use to verify a PKCS#7 message.  PKCS#7
 * uses the issuer's name and the issuing certificate serial number for
 * matching purposes.  These must match the certificate issuer's name (not
 * subject's name) and the certificate serial number [RFC 2315 6.7].
 */
static int pkcs7_find_key(struct pkcs7_message *pkcs7,
			  struct pkcs7_signed_info *sinfo)
{
	struct x509_certificate *x509;
	unsigned certix = 1;

	kenter("%u,%u,%u",
	       sinfo->index, sinfo->raw_serial_size, sinfo->raw_issuer_size);

	for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
		/* I'm _assuming_ that the generator of the PKCS#7 message will
		 * encode the fields from the X.509 cert in the same way in the
		 * PKCS#7 message - but I can't be 100% sure of that.  It's
		 * possible this will need element-by-element comparison.
		 */
		if (x509->raw_serial_size != sinfo->raw_serial_size ||
		    memcmp(x509->raw_serial, sinfo->raw_serial,
			   sinfo->raw_serial_size) != 0)
			continue;
		pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
			 sinfo->index, certix);

		if (x509->raw_issuer_size != sinfo->raw_issuer_size ||
		    memcmp(x509->raw_issuer, sinfo->raw_issuer,
			   sinfo->raw_issuer_size) != 0) {
			pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n",
				sinfo->index);
			continue;
		}

		if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
			pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
				sinfo->index);
			continue;
		}

		sinfo->signer = x509;
		return 0;
	}
	pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n",
		sinfo->index, sinfo->raw_serial_size, sinfo->raw_serial);
	return -ENOKEY;
}

/*
 * Verify the internal certificate chain as best we can.
 */
static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
				  struct pkcs7_signed_info *sinfo)
{
	struct x509_certificate *x509 = sinfo->signer, *p;
	int ret;

	kenter("");

	for (p = pkcs7->certs; p; p = p->next)
		p->seen = false;

	for (;;) {
		pr_debug("verify %s: %s\n", x509->subject, x509->fingerprint);
		x509->seen = true;
		ret = x509_get_sig_params(x509);
		if (ret < 0)
			return ret;

		if (x509->issuer)
			pr_debug("- issuer %s\n", x509->issuer);
		if (x509->authority)
			pr_debug("- authkeyid %s\n", x509->authority);

		if (!x509->authority ||
		    (x509->subject &&
		     strcmp(x509->subject, x509->issuer) == 0)) {
			/* If there's no authority certificate specified, then
			 * the certificate must be self-signed and is the root
			 * of the chain.  Likewise if the cert is its own
			 * authority.
			 */
			pr_debug("- no auth?\n");
			if (x509->raw_subject_size != x509->raw_issuer_size ||
			    memcmp(x509->raw_subject, x509->raw_issuer,
				   x509->raw_issuer_size) != 0)
				return 0;

			ret = x509_check_signature(x509->pub, x509);
			if (ret < 0)
				return ret;
			x509->signer = x509;
			pr_debug("- self-signed\n");
			return 0;
		}

		/* Look through the X.509 certificates in the PKCS#7 message's
		 * list to see if the next one is there.
		 */
		pr_debug("- want %s\n", x509->authority);
		for (p = pkcs7->certs; p; p = p->next) {
			pr_debug("- cmp [%u] %s\n", p->index, p->fingerprint);
			if (p->raw_subject_size == x509->raw_issuer_size &&
			    strcmp(p->fingerprint, x509->authority) == 0 &&
			    memcmp(p->raw_subject, x509->raw_issuer,
				   x509->raw_issuer_size) == 0)
				goto found_issuer;
		}

		/* We didn't find the root of this chain */
		pr_debug("- top\n");
		return 0;

	found_issuer:
		pr_debug("- issuer %s\n", p->subject);
		if (p->seen) {
			pr_warn("Sig %u: X.509 chain contains loop\n",
				sinfo->index);
			return 0;
		}
		ret = x509_check_signature(p->pub, x509);
		if (ret < 0)
			return ret;
		x509->signer = p;
		if (x509 == p) {
			pr_debug("- self-signed\n");
			return 0;
		}
		x509 = p;
		might_sleep();
	}
}

/*
 * Verify one signed information block from a PKCS#7 message.
 */
static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
			    struct pkcs7_signed_info *sinfo)
{
	int ret;

	kenter(",%u", sinfo->index);

	/* First of all, digest the data in the PKCS#7 message and the
	 * signed information block
	 */
	ret = pkcs7_digest(pkcs7, sinfo);
	if (ret < 0)
		return ret;

	/* Find the key for the signature */
	ret = pkcs7_find_key(pkcs7, sinfo);
	if (ret < 0)
		return ret;

	pr_devel("Using X.509[%u] for sig %u\n",
		 sinfo->signer->index, sinfo->index);

	/* Verify the PKCS#7 binary against the key */
	ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
	if (ret < 0)
		return ret;

	pr_devel("Verified signature %u\n", sinfo->index);

	/* Verify the internal certificate chain */
	return pkcs7_verify_sig_chain(pkcs7, sinfo);
}

/**
 * pkcs7_verify - Verify a PKCS#7 message
 * @pkcs7: The PKCS#7 message to be verified
 */
int pkcs7_verify(struct pkcs7_message *pkcs7)
{
	struct pkcs7_signed_info *sinfo;
	struct x509_certificate *x509;
	int ret, n;

	kenter("");

	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
		ret = x509_get_sig_params(x509);
		if (ret < 0)
			return ret;
		pr_debug("X.509[%u] %s\n", n, x509->authority);
	}

	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
		ret = pkcs7_verify_one(pkcs7, sinfo);
		if (ret < 0) {
			kleave(" = %d", ret);
			return ret;
		}
	}

	kleave(" = 0");
	return 0;
}
EXPORT_SYMBOL_GPL(pkcs7_verify);