summaryrefslogtreecommitdiff
path: root/crypto/asymmetric_keys/x509_public_key.c
blob: 2fcf707fb20867ab92281b4655a2a143f66dd5f2 (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
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
/* 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)
 *
 * 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) "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"

static bool use_builtin_keys;
static struct asymmetric_key_id *ca_keyid;

#ifndef MODULE
static struct {
	struct asymmetric_key_id id;
	unsigned char data[10];
} cakey;

static int __init ca_keys_setup(char *str)
{
	if (!str)		/* default system keyring */
		return 1;

	if (strncmp(str, "id:", 3) == 0) {
		struct asymmetric_key_id *p = &cakey.id;
		size_t hexlen = (strlen(str) - 3) / 2;
		int ret;

		if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
			pr_err("Missing or invalid ca_keys id\n");
			return 1;
		}

		ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
		if (ret < 0)
			pr_err("Unparsable ca_keys id hex string\n");
		else
			ca_keyid = p;	/* owner key 'id:xxxxxx' */
	} else if (strcmp(str, "builtin") == 0) {
		use_builtin_keys = true;
	}

	return 1;
}
__setup("ca_keys=", ca_keys_setup);
#endif

/**
 * x509_request_asymmetric_key - Request a key by X.509 certificate params.
 * @keyring: The keys to search.
 * @id: The issuer & serialNumber to look for or NULL.
 * @skid: The subjectKeyIdentifier to look for or NULL.
 * @partial: Use partial match if true, exact if false.
 *
 * Find a key in the given keyring by identifier.  The preferred identifier is
 * the issuer + serialNumber and the fallback identifier is the
 * subjectKeyIdentifier.  If both are given, the lookup is by the former, but
 * the latter must also match.
 */
struct key *x509_request_asymmetric_key(struct key *keyring,
					const struct asymmetric_key_id *id,
					const struct asymmetric_key_id *skid,
					bool partial)
{
	struct key *key;
	key_ref_t ref;
	const char *lookup;
	char *req, *p;
	int len;

	if (id) {
		lookup = id->data;
		len = id->len;
	} else {
		lookup = skid->data;
		len = skid->len;
	}

	/* Construct an identifier "id:<keyid>". */
	p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
	if (!req)
		return ERR_PTR(-ENOMEM);

	if (partial) {
		*p++ = 'i';
		*p++ = 'd';
	} else {
		*p++ = 'e';
		*p++ = 'x';
	}
	*p++ = ':';
	p = bin2hex(p, lookup, len);
	*p = 0;

	pr_debug("Look up: \"%s\"\n", req);

	ref = keyring_search(make_key_ref(keyring, 1),
			     &key_type_asymmetric, req);
	if (IS_ERR(ref))
		pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
	kfree(req);

	if (IS_ERR(ref)) {
		switch (PTR_ERR(ref)) {
			/* Hide some search errors */
		case -EACCES:
		case -ENOTDIR:
		case -EAGAIN:
			return ERR_PTR(-ENOKEY);
		default:
			return ERR_CAST(ref);
		}
	}

	key = key_ref_to_ptr(ref);
	if (id && skid) {
		const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
		if (!kids->id[1]) {
			pr_debug("issuer+serial match, but expected SKID missing\n");
			goto reject;
		}
		if (!asymmetric_key_id_same(skid, kids->id[1])) {
			pr_debug("issuer+serial match, but SKID does not\n");
			goto reject;
		}
	}

	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
	return key;

reject:
	key_put(key);
	return ERR_PTR(-EKEYREJECTED);
}
EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);

/*
 * 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 crypto_shash *tfm;
	struct shash_desc *desc;
	size_t digest_size, desc_size;
	void *digest;
	int ret;

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

	if (cert->unsupported_crypto)
		return -ENOPKG;
	if (cert->sig.s)
		return 0;

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

	cert->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(cert->sig.hash_algo, 0, 0);
	if (IS_ERR(tfm)) {
		if (PTR_ERR(tfm) == -ENOENT) {
			cert->unsupported_crypto = true;
			return -ENOPKG;
		}
		return PTR_ERR(tfm);
	}

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

	/* We allocate the hash operational data storage on the end of the
	 * digest storage space.
	 */
	ret = -ENOMEM;
	digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
			 GFP_KERNEL);
	if (!digest)
		goto error;

	cert->sig.digest = digest;
	cert->sig.digest_size = digest_size;

	desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
	desc->tfm = tfm;
	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

	ret = crypto_shash_init(desc);
	if (ret < 0)
		goto error;
	might_sleep();
	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
error:
	crypto_free_shash(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
}
EXPORT_SYMBOL_GPL(x509_get_sig_params);

/*
 * Check the signature on a certificate using the provided public key
 */
int x509_check_signature(const struct public_key *pub,
			 struct x509_certificate *cert)
{
	int ret;

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

	ret = x509_get_sig_params(cert);
	if (ret < 0)
		return ret;

	ret = public_key_verify_signature(pub, &cert->sig);
	if (ret == -ENOPKG)
		cert->unsupported_crypto = true;
	pr_debug("Cert Verification: %d\n", ret);
	return ret;
}
EXPORT_SYMBOL_GPL(x509_check_signature);

/*
 * Check the new certificate against the ones in the trust keyring.  If one of
 * those is the signing key and validates the new certificate, then mark the
 * new certificate as being trusted.
 *
 * Return 0 if the new certificate was successfully validated, 1 if we couldn't
 * find a matching parent certificate in the trusted list and an error if there
 * is a matching certificate but the signature check fails.
 */
static int x509_validate_trust(struct x509_certificate *cert,
			       struct key *trust_keyring)
{
	struct key *key;
	int ret = 1;

	if (!trust_keyring)
		return -EOPNOTSUPP;

	if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
		return -EPERM;

	key = x509_request_asymmetric_key(trust_keyring,
					  cert->akid_id, cert->akid_skid,
					  false);
	if (!IS_ERR(key))  {
		if (!use_builtin_keys
		    || test_bit(KEY_FLAG_BUILTIN, &key->flags))
			ret = x509_check_signature(key->payload.data[asym_crypto],
						   cert);
		key_put(key);
	}
	return ret;
}

/*
 * 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->pub->pkey_algo ||
	    !cert->sig.pkey_algo ||
	    !cert->sig.hash_algo) {
		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);
	pr_devel("Cert Signature: %s + %s\n",
		 cert->sig.pkey_algo,
		 cert->sig.hash_algo);

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

	/* Check the signature on the key if it appears to be self-signed */
	if ((!cert->akid_skid && !cert->akid_id) ||
	    asymmetric_key_id_same(cert->skid, cert->akid_skid) ||
	    asymmetric_key_id_same(cert->id, cert->akid_id)) {
		ret = x509_check_signature(cert->pub, cert); /* self-signed */
		if (ret < 0)
			goto error_free_cert;
	} else if (!prep->trusted) {
		ret = x509_validate_trust(cert, get_system_trusted_keyring());
		if (ret)
			ret = x509_validate_trust(cert, get_ima_mok_keyring());
		if (!ret)
			prep->trusted = 1;
	}

	/* 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->description = desc;
	prep->quotalen = 100;

	/* We've finished with the certificate */
	cert->pub = NULL;
	cert->id = NULL;
	cert->skid = 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_LICENSE("GPL");