aboutsummaryrefslogtreecommitdiff
path: root/crypto/asymmetric_keys/restrict.c
blob: 77ebebada29c44095a0bd548c5606766bd3f7bf9 (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
// SPDX-License-Identifier: GPL-2.0-or-later
/* Instantiate a public key crypto key from an X.509 Certificate
 *
 * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) "ASYM: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <crypto/public_key.h>
#include "asymmetric_keys.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

/**
 * restrict_link_by_signature - Restrict additions to a ring of public keys
 * @dest_keyring: Keyring being linked to.
 * @type: The type of key being added.
 * @payload: The payload of the new key.
 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
 *
 * 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.
 *
 * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
 * matching parent certificate in the trusted list, -EKEYREJECTED if the
 * signature check fails or the key is blacklisted, -ENOPKG if the signature
 * uses unsupported crypto, or some other error if there is a matching
 * certificate but the signature check cannot be performed.
 */
int restrict_link_by_signature(struct key *dest_keyring,
			       const struct key_type *type,
			       const union key_payload *payload,
			       struct key *trust_keyring)
{
	const struct public_key_signature *sig;
	struct key *key;
	int ret;

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

	if (!trust_keyring)
		return -ENOKEY;

	if (type != &key_type_asymmetric)
		return -EOPNOTSUPP;

	sig = payload->data[asym_auth];
	if (!sig)
		return -ENOPKG;
	if (!sig->auth_ids[0] && !sig->auth_ids[1])
		return -ENOKEY;

	if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
		return -EPERM;

	/* See if we have a key that signed this one. */
	key = find_asymmetric_key(trust_keyring,
				  sig->auth_ids[0], sig->auth_ids[1],
				  false);
	if (IS_ERR(key))
		return -ENOKEY;

	if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
		ret = -ENOKEY;
	else
		ret = verify_signature(key, sig);
	key_put(key);
	return ret;
}

static bool match_either_id(const struct asymmetric_key_ids *pair,
			    const struct asymmetric_key_id *single)
{
	return (asymmetric_key_id_same(pair->id[0], single) ||
		asymmetric_key_id_same(pair->id[1], single));
}

static int key_or_keyring_common(struct key *dest_keyring,
				 const struct key_type *type,
				 const union key_payload *payload,
				 struct key *trusted, bool check_dest)
{
	const struct public_key_signature *sig;
	struct key *key = NULL;
	int ret;

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

	if (!dest_keyring)
		return -ENOKEY;
	else if (dest_keyring->type != &key_type_keyring)
		return -EOPNOTSUPP;

	if (!trusted && !check_dest)
		return -ENOKEY;

	if (type != &key_type_asymmetric)
		return -EOPNOTSUPP;

	sig = payload->data[asym_auth];
	if (!sig)
		return -ENOPKG;
	if (!sig->auth_ids[0] && !sig->auth_ids[1])
		return -ENOKEY;

	if (trusted) {
		if (trusted->type == &key_type_keyring) {
			/* See if we have a key that signed this one. */
			key = find_asymmetric_key(trusted, sig->auth_ids[0],
						  sig->auth_ids[1], false);
			if (IS_ERR(key))
				key = NULL;
		} else if (trusted->type == &key_type_asymmetric) {
			const struct asymmetric_key_ids *signer_ids;

			signer_ids = asymmetric_key_ids(trusted);

			/*
			 * The auth_ids come from the candidate key (the
			 * one that is being considered for addition to
			 * dest_keyring) and identify the key that was
			 * used to sign.
			 *
			 * The signer_ids are identifiers for the
			 * signing key specified for dest_keyring.
			 *
			 * The first auth_id is the preferred id, and
			 * the second is the fallback. If only one
			 * auth_id is present, it may match against
			 * either signer_id. If two auth_ids are
			 * present, the first auth_id must match one
			 * signer_id and the second auth_id must match
			 * the second signer_id.
			 */
			if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
				const struct asymmetric_key_id *auth_id;

				auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
				if (match_either_id(signer_ids, auth_id))
					key = __key_get(trusted);

			} else if (asymmetric_key_id_same(signer_ids->id[1],
							  sig->auth_ids[1]) &&
				   match_either_id(signer_ids,
						   sig->auth_ids[0])) {
				key = __key_get(trusted);
			}
		} else {
			return -EOPNOTSUPP;
		}
	}

	if (check_dest && !key) {
		/* See if the destination has a key that signed this one. */
		key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
					  sig->auth_ids[1], false);
		if (IS_ERR(key))
			key = NULL;
	}

	if (!key)
		return -ENOKEY;

	ret = key_validate(key);
	if (ret == 0)
		ret = verify_signature(key, sig);

	key_put(key);
	return ret;
}

/**
 * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
 * keys using the restrict_key information stored in the ring.
 * @dest_keyring: Keyring being linked to.
 * @type: The type of key being added.
 * @payload: The payload of the new key.
 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 *
 * Check the new certificate only against the key or keys passed in the data
 * parameter. If one of those is the signing key and validates the new
 * certificate, then mark the new certificate as being ok to link.
 *
 * Returns 0 if the new certificate was accepted, -ENOKEY if we
 * couldn't find a matching parent certificate in the trusted list,
 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
 * unsupported crypto, or some other error if there is a matching certificate
 * but the signature check cannot be performed.
 */
int restrict_link_by_key_or_keyring(struct key *dest_keyring,
				    const struct key_type *type,
				    const union key_payload *payload,
				    struct key *trusted)
{
	return key_or_keyring_common(dest_keyring, type, payload, trusted,
				     false);
}

/**
 * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
 * public keys using the restrict_key information stored in the ring.
 * @dest_keyring: Keyring being linked to.
 * @type: The type of key being added.
 * @payload: The payload of the new key.
 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 *
 * Check the new certificate only against the key or keys passed in the data
 * parameter. If one of those is the signing key and validates the new
 * certificate, then mark the new certificate as being ok to link.
 *
 * Returns 0 if the new certificate was accepted, -ENOKEY if we
 * couldn't find a matching parent certificate in the trusted list,
 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
 * unsupported crypto, or some other error if there is a matching certificate
 * but the signature check cannot be performed.
 */
int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
					  const struct key_type *type,
					  const union key_payload *payload,
					  struct key *trusted)
{
	return key_or_keyring_common(dest_keyring, type, payload, trusted,
				     true);
}