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, 2016 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#define pr_fmt(fmt) "ASYM: "fmt
9#include <linux/module.h>
10#include <linux/kernel.h>
11#include <linux/err.h>
12#include <crypto/public_key.h>
13#include "asymmetric_keys.h"
14
15static bool use_builtin_keys;
16static struct asymmetric_key_id *ca_keyid;
17
18#ifndef MODULE
19static struct {
20 struct asymmetric_key_id id;
21 unsigned char data[10];
22} cakey;
23
24static int __init ca_keys_setup(char *str)
25{
26 if (!str) /* default system keyring */
27 return 1;
28
29 if (strncmp(str, "id:", 3) == 0) {
30 struct asymmetric_key_id *p = &cakey.id;
31 size_t hexlen = (strlen(str) - 3) / 2;
32 int ret;
33
34 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
35 pr_err("Missing or invalid ca_keys id\n");
36 return 1;
37 }
38
39 ret = __asymmetric_key_hex_to_key_id(id: str + 3, match_id: p, hexlen);
40 if (ret < 0)
41 pr_err("Unparsable ca_keys id hex string\n");
42 else
43 ca_keyid = p; /* owner key 'id:xxxxxx' */
44 } else if (strcmp(str, "builtin") == 0) {
45 use_builtin_keys = true;
46 }
47
48 return 1;
49}
50__setup("ca_keys=", ca_keys_setup);
51#endif
52
53/**
54 * restrict_link_by_signature - Restrict additions to a ring of public keys
55 * @dest_keyring: Keyring being linked to.
56 * @type: The type of key being added.
57 * @payload: The payload of the new key.
58 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
59 *
60 * Check the new certificate against the ones in the trust keyring. If one of
61 * those is the signing key and validates the new certificate, then mark the
62 * new certificate as being trusted.
63 *
64 * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
65 * matching parent certificate in the trusted list, -EKEYREJECTED if the
66 * signature check fails or the key is blacklisted, -ENOPKG if the signature
67 * uses unsupported crypto, or some other error if there is a matching
68 * certificate but the signature check cannot be performed.
69 */
70int restrict_link_by_signature(struct key *dest_keyring,
71 const struct key_type *type,
72 const union key_payload *payload,
73 struct key *trust_keyring)
74{
75 const struct public_key_signature *sig;
76 struct key *key;
77 int ret;
78
79 pr_devel("==>%s()\n", __func__);
80
81 if (!trust_keyring)
82 return -ENOKEY;
83
84 if (type != &key_type_asymmetric)
85 return -EOPNOTSUPP;
86
87 sig = payload->data[asym_auth];
88 if (!sig)
89 return -ENOPKG;
90 if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
91 return -ENOKEY;
92
93 if (ca_keyid && !asymmetric_key_id_partial(kid1: sig->auth_ids[1], kid2: ca_keyid))
94 return -EPERM;
95
96 /* See if we have a key that signed this one. */
97 key = find_asymmetric_key(keyring: trust_keyring,
98 id_0: sig->auth_ids[0], id_1: sig->auth_ids[1],
99 id_2: sig->auth_ids[2], partial: false);
100 if (IS_ERR(ptr: key))
101 return -ENOKEY;
102
103 if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
104 ret = -ENOKEY;
105 else if (IS_BUILTIN(CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN) &&
106 !strcmp(dest_keyring->description, ".secondary_trusted_keys") &&
107 !test_bit(KEY_FLAG_BUILTIN, &key->flags))
108 ret = -ENOKEY;
109 else
110 ret = verify_signature(key, sig);
111 key_put(key);
112 return ret;
113}
114
115/**
116 * restrict_link_by_ca - Restrict additions to a ring of CA keys
117 * @dest_keyring: Keyring being linked to.
118 * @type: The type of key being added.
119 * @payload: The payload of the new key.
120 * @trust_keyring: Unused.
121 *
122 * Check if the new certificate is a CA. If it is a CA, then mark the new
123 * certificate as being ok to link.
124 *
125 * Returns 0 if the new certificate was accepted, -ENOKEY if the
126 * certificate is not a CA. -ENOPKG if the signature uses unsupported
127 * crypto, or some other error if there is a matching certificate but
128 * the signature check cannot be performed.
129 */
130int restrict_link_by_ca(struct key *dest_keyring,
131 const struct key_type *type,
132 const union key_payload *payload,
133 struct key *trust_keyring)
134{
135 const struct public_key *pkey;
136
137 if (type != &key_type_asymmetric)
138 return -EOPNOTSUPP;
139
140 pkey = payload->data[asym_crypto];
141 if (!pkey)
142 return -ENOPKG;
143 if (!test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
144 return -ENOKEY;
145 if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
146 return -ENOKEY;
147 if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX))
148 return 0;
149 if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
150 return -ENOKEY;
151
152 return 0;
153}
154
155/**
156 * restrict_link_by_digsig - Restrict additions to a ring of digsig keys
157 * @dest_keyring: Keyring being linked to.
158 * @type: The type of key being added.
159 * @payload: The payload of the new key.
160 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
161 *
162 * Check if the new certificate has digitalSignature usage set. If it is,
163 * then mark the new certificate as being ok to link. Afterwards verify
164 * the new certificate against the ones in the trust_keyring.
165 *
166 * Returns 0 if the new certificate was accepted, -ENOKEY if the
167 * certificate is not a digsig. -ENOPKG if the signature uses unsupported
168 * crypto, or some other error if there is a matching certificate but
169 * the signature check cannot be performed.
170 */
171int restrict_link_by_digsig(struct key *dest_keyring,
172 const struct key_type *type,
173 const union key_payload *payload,
174 struct key *trust_keyring)
175{
176 const struct public_key *pkey;
177
178 if (type != &key_type_asymmetric)
179 return -EOPNOTSUPP;
180
181 pkey = payload->data[asym_crypto];
182
183 if (!pkey)
184 return -ENOPKG;
185
186 if (!test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
187 return -ENOKEY;
188
189 if (test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
190 return -ENOKEY;
191
192 if (test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
193 return -ENOKEY;
194
195 return restrict_link_by_signature(dest_keyring, type, payload,
196 trust_keyring);
197}
198
199static bool match_either_id(const struct asymmetric_key_id **pair,
200 const struct asymmetric_key_id *single)
201{
202 return (asymmetric_key_id_same(kid1: pair[0], kid2: single) ||
203 asymmetric_key_id_same(kid1: pair[1], kid2: single));
204}
205
206static int key_or_keyring_common(struct key *dest_keyring,
207 const struct key_type *type,
208 const union key_payload *payload,
209 struct key *trusted, bool check_dest)
210{
211 const struct public_key_signature *sig;
212 struct key *key = NULL;
213 int ret;
214
215 pr_devel("==>%s()\n", __func__);
216
217 if (!dest_keyring)
218 return -ENOKEY;
219 else if (dest_keyring->type != &key_type_keyring)
220 return -EOPNOTSUPP;
221
222 if (!trusted && !check_dest)
223 return -ENOKEY;
224
225 if (type != &key_type_asymmetric)
226 return -EOPNOTSUPP;
227
228 sig = payload->data[asym_auth];
229 if (!sig)
230 return -ENOPKG;
231 if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
232 return -ENOKEY;
233
234 if (trusted) {
235 if (trusted->type == &key_type_keyring) {
236 /* See if we have a key that signed this one. */
237 key = find_asymmetric_key(keyring: trusted, id_0: sig->auth_ids[0],
238 id_1: sig->auth_ids[1],
239 id_2: sig->auth_ids[2], partial: false);
240 if (IS_ERR(ptr: key))
241 key = NULL;
242 } else if (trusted->type == &key_type_asymmetric) {
243 const struct asymmetric_key_id **signer_ids;
244
245 signer_ids = (const struct asymmetric_key_id **)
246 asymmetric_key_ids(key: trusted)->id;
247
248 /*
249 * The auth_ids come from the candidate key (the
250 * one that is being considered for addition to
251 * dest_keyring) and identify the key that was
252 * used to sign.
253 *
254 * The signer_ids are identifiers for the
255 * signing key specified for dest_keyring.
256 *
257 * The first auth_id is the preferred id, 2nd and
258 * 3rd are the fallbacks. If exactly one of
259 * auth_ids[0] and auth_ids[1] is present, it may
260 * match either signer_ids[0] or signed_ids[1].
261 * If both are present the first one may match
262 * either signed_id but the second one must match
263 * the second signer_id. If neither of them is
264 * available, auth_ids[2] is matched against
265 * signer_ids[2] as a fallback.
266 */
267 if (!sig->auth_ids[0] && !sig->auth_ids[1]) {
268 if (asymmetric_key_id_same(kid1: signer_ids[2],
269 kid2: sig->auth_ids[2]))
270 key = __key_get(key: trusted);
271
272 } else if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
273 const struct asymmetric_key_id *auth_id;
274
275 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
276 if (match_either_id(pair: signer_ids, single: auth_id))
277 key = __key_get(key: trusted);
278
279 } else if (asymmetric_key_id_same(kid1: signer_ids[1],
280 kid2: sig->auth_ids[1]) &&
281 match_either_id(pair: signer_ids,
282 single: sig->auth_ids[0])) {
283 key = __key_get(key: trusted);
284 }
285 } else {
286 return -EOPNOTSUPP;
287 }
288 }
289
290 if (check_dest && !key) {
291 /* See if the destination has a key that signed this one. */
292 key = find_asymmetric_key(keyring: dest_keyring, id_0: sig->auth_ids[0],
293 id_1: sig->auth_ids[1], id_2: sig->auth_ids[2],
294 partial: false);
295 if (IS_ERR(ptr: key))
296 key = NULL;
297 }
298
299 if (!key)
300 return -ENOKEY;
301
302 ret = key_validate(key);
303 if (ret == 0)
304 ret = verify_signature(key, sig);
305
306 key_put(key);
307 return ret;
308}
309
310/**
311 * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
312 * keys using the restrict_key information stored in the ring.
313 * @dest_keyring: Keyring being linked to.
314 * @type: The type of key being added.
315 * @payload: The payload of the new key.
316 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
317 *
318 * Check the new certificate only against the key or keys passed in the data
319 * parameter. If one of those is the signing key and validates the new
320 * certificate, then mark the new certificate as being ok to link.
321 *
322 * Returns 0 if the new certificate was accepted, -ENOKEY if we
323 * couldn't find a matching parent certificate in the trusted list,
324 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
325 * unsupported crypto, or some other error if there is a matching certificate
326 * but the signature check cannot be performed.
327 */
328int restrict_link_by_key_or_keyring(struct key *dest_keyring,
329 const struct key_type *type,
330 const union key_payload *payload,
331 struct key *trusted)
332{
333 return key_or_keyring_common(dest_keyring, type, payload, trusted,
334 check_dest: false);
335}
336
337/**
338 * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
339 * public keys using the restrict_key information stored in the ring.
340 * @dest_keyring: Keyring being linked to.
341 * @type: The type of key being added.
342 * @payload: The payload of the new key.
343 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
344 *
345 * Check the new certificate against the key or keys passed in the data
346 * parameter and against the keys already linked to the destination keyring. If
347 * one of those is the signing key and validates the new certificate, then mark
348 * the new certificate as being ok to link.
349 *
350 * Returns 0 if the new certificate was accepted, -ENOKEY if we
351 * couldn't find a matching parent certificate in the trusted list,
352 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
353 * unsupported crypto, or some other error if there is a matching certificate
354 * but the signature check cannot be performed.
355 */
356int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
357 const struct key_type *type,
358 const union key_payload *payload,
359 struct key *trusted)
360{
361 return key_or_keyring_common(dest_keyring, type, payload, trusted,
362 check_dest: true);
363}
364