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 /* Must be last as it ends in a flexible-array member. */
21 TRAILING_OVERLAP(struct asymmetric_key_id, id, data,
22 unsigned char data[10];
23 );
24} cakey;
25static_assert(offsetof(typeof(cakey), id.data) == offsetof(typeof(cakey), data));
26
27static int __init ca_keys_setup(char *str)
28{
29 if (!str) /* default system keyring */
30 return 1;
31
32 if (strncmp(str, "id:", 3) == 0) {
33 struct asymmetric_key_id *p = &cakey.id;
34 size_t hexlen = (strlen(str) - 3) / 2;
35 int ret;
36
37 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
38 pr_err("Missing or invalid ca_keys id\n");
39 return 1;
40 }
41
42 ret = __asymmetric_key_hex_to_key_id(id: str + 3, match_id: p, hexlen);
43 if (ret < 0)
44 pr_err("Unparsable ca_keys id hex string\n");
45 else
46 ca_keyid = p; /* owner key 'id:xxxxxx' */
47 } else if (strcmp(str, "builtin") == 0) {
48 use_builtin_keys = true;
49 }
50
51 return 1;
52}
53__setup("ca_keys=", ca_keys_setup);
54#endif
55
56/**
57 * restrict_link_by_signature - Restrict additions to a ring of public keys
58 * @dest_keyring: Keyring being linked to.
59 * @type: The type of key being added.
60 * @payload: The payload of the new key.
61 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
62 *
63 * Check the new certificate against the ones in the trust keyring. If one of
64 * those is the signing key and validates the new certificate, then mark the
65 * new certificate as being trusted.
66 *
67 * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
68 * matching parent certificate in the trusted list, -EKEYREJECTED if the
69 * signature check fails or the key is blacklisted, -ENOPKG if the signature
70 * uses unsupported crypto, or some other error if there is a matching
71 * certificate but the signature check cannot be performed.
72 */
73int restrict_link_by_signature(struct key *dest_keyring,
74 const struct key_type *type,
75 const union key_payload *payload,
76 struct key *trust_keyring)
77{
78 const struct public_key_signature *sig;
79 struct key *key;
80 int ret;
81
82 pr_devel("==>%s()\n", __func__);
83
84 if (!trust_keyring)
85 return -ENOKEY;
86
87 if (type != &key_type_asymmetric)
88 return -EOPNOTSUPP;
89
90 sig = payload->data[asym_auth];
91 if (!sig)
92 return -ENOPKG;
93 if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
94 return -ENOKEY;
95
96 if (ca_keyid && !asymmetric_key_id_partial(kid1: sig->auth_ids[1], kid2: ca_keyid))
97 return -EPERM;
98
99 /* See if we have a key that signed this one. */
100 key = find_asymmetric_key(keyring: trust_keyring,
101 id_0: sig->auth_ids[0], id_1: sig->auth_ids[1],
102 id_2: sig->auth_ids[2], partial: false);
103 if (IS_ERR(ptr: key))
104 return -ENOKEY;
105
106 if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
107 ret = -ENOKEY;
108 else if (IS_BUILTIN(CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN) &&
109 !strcmp(dest_keyring->description, ".secondary_trusted_keys") &&
110 !test_bit(KEY_FLAG_BUILTIN, &key->flags))
111 ret = -ENOKEY;
112 else
113 ret = verify_signature(key, sig);
114 key_put(key);
115 return ret;
116}
117
118/**
119 * restrict_link_by_ca - Restrict additions to a ring of CA keys
120 * @dest_keyring: Keyring being linked to.
121 * @type: The type of key being added.
122 * @payload: The payload of the new key.
123 * @trust_keyring: Unused.
124 *
125 * Check if the new certificate is a CA. If it is a CA, then mark the new
126 * certificate as being ok to link.
127 *
128 * Returns 0 if the new certificate was accepted, -ENOKEY if the
129 * certificate is not a CA. -ENOPKG if the signature uses unsupported
130 * crypto, or some other error if there is a matching certificate but
131 * the signature check cannot be performed.
132 */
133int restrict_link_by_ca(struct key *dest_keyring,
134 const struct key_type *type,
135 const union key_payload *payload,
136 struct key *trust_keyring)
137{
138 const struct public_key *pkey;
139
140 if (type != &key_type_asymmetric)
141 return -EOPNOTSUPP;
142
143 pkey = payload->data[asym_crypto];
144 if (!pkey)
145 return -ENOPKG;
146 if (!test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
147 return -ENOKEY;
148 if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
149 return -ENOKEY;
150 if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX))
151 return 0;
152 if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
153 return -ENOKEY;
154
155 return 0;
156}
157
158/**
159 * restrict_link_by_digsig - Restrict additions to a ring of digsig keys
160 * @dest_keyring: Keyring being linked to.
161 * @type: The type of key being added.
162 * @payload: The payload of the new key.
163 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
164 *
165 * Check if the new certificate has digitalSignature usage set. If it is,
166 * then mark the new certificate as being ok to link. Afterwards verify
167 * the new certificate against the ones in the trust_keyring.
168 *
169 * Returns 0 if the new certificate was accepted, -ENOKEY if the
170 * certificate is not a digsig. -ENOPKG if the signature uses unsupported
171 * crypto, or some other error if there is a matching certificate but
172 * the signature check cannot be performed.
173 */
174int restrict_link_by_digsig(struct key *dest_keyring,
175 const struct key_type *type,
176 const union key_payload *payload,
177 struct key *trust_keyring)
178{
179 const struct public_key *pkey;
180
181 if (type != &key_type_asymmetric)
182 return -EOPNOTSUPP;
183
184 pkey = payload->data[asym_crypto];
185
186 if (!pkey)
187 return -ENOPKG;
188
189 if (!test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
190 return -ENOKEY;
191
192 if (test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
193 return -ENOKEY;
194
195 if (test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
196 return -ENOKEY;
197
198 return restrict_link_by_signature(dest_keyring, type, payload,
199 trust_keyring);
200}
201
202static bool match_either_id(const struct asymmetric_key_id **pair,
203 const struct asymmetric_key_id *single)
204{
205 return (asymmetric_key_id_same(kid1: pair[0], kid2: single) ||
206 asymmetric_key_id_same(kid1: pair[1], kid2: single));
207}
208
209static int key_or_keyring_common(struct key *dest_keyring,
210 const struct key_type *type,
211 const union key_payload *payload,
212 struct key *trusted, bool check_dest)
213{
214 const struct public_key_signature *sig;
215 struct key *key = NULL;
216 int ret;
217
218 pr_devel("==>%s()\n", __func__);
219
220 if (!dest_keyring)
221 return -ENOKEY;
222 else if (dest_keyring->type != &key_type_keyring)
223 return -EOPNOTSUPP;
224
225 if (!trusted && !check_dest)
226 return -ENOKEY;
227
228 if (type != &key_type_asymmetric)
229 return -EOPNOTSUPP;
230
231 sig = payload->data[asym_auth];
232 if (!sig)
233 return -ENOPKG;
234 if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
235 return -ENOKEY;
236
237 if (trusted) {
238 if (trusted->type == &key_type_keyring) {
239 /* See if we have a key that signed this one. */
240 key = find_asymmetric_key(keyring: trusted, id_0: sig->auth_ids[0],
241 id_1: sig->auth_ids[1],
242 id_2: sig->auth_ids[2], partial: false);
243 if (IS_ERR(ptr: key))
244 key = NULL;
245 } else if (trusted->type == &key_type_asymmetric) {
246 const struct asymmetric_key_id **signer_ids;
247
248 signer_ids = (const struct asymmetric_key_id **)
249 asymmetric_key_ids(key: trusted)->id;
250
251 /*
252 * The auth_ids come from the candidate key (the
253 * one that is being considered for addition to
254 * dest_keyring) and identify the key that was
255 * used to sign.
256 *
257 * The signer_ids are identifiers for the
258 * signing key specified for dest_keyring.
259 *
260 * The first auth_id is the preferred id, 2nd and
261 * 3rd are the fallbacks. If exactly one of
262 * auth_ids[0] and auth_ids[1] is present, it may
263 * match either signer_ids[0] or signed_ids[1].
264 * If both are present the first one may match
265 * either signed_id but the second one must match
266 * the second signer_id. If neither of them is
267 * available, auth_ids[2] is matched against
268 * signer_ids[2] as a fallback.
269 */
270 if (!sig->auth_ids[0] && !sig->auth_ids[1]) {
271 if (asymmetric_key_id_same(kid1: signer_ids[2],
272 kid2: sig->auth_ids[2]))
273 key = __key_get(key: trusted);
274
275 } else if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
276 const struct asymmetric_key_id *auth_id;
277
278 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
279 if (match_either_id(pair: signer_ids, single: auth_id))
280 key = __key_get(key: trusted);
281
282 } else if (asymmetric_key_id_same(kid1: signer_ids[1],
283 kid2: sig->auth_ids[1]) &&
284 match_either_id(pair: signer_ids,
285 single: sig->auth_ids[0])) {
286 key = __key_get(key: trusted);
287 }
288 } else {
289 return -EOPNOTSUPP;
290 }
291 }
292
293 if (check_dest && !key) {
294 /* See if the destination has a key that signed this one. */
295 key = find_asymmetric_key(keyring: dest_keyring, id_0: sig->auth_ids[0],
296 id_1: sig->auth_ids[1], id_2: sig->auth_ids[2],
297 partial: false);
298 if (IS_ERR(ptr: key))
299 key = NULL;
300 }
301
302 if (!key)
303 return -ENOKEY;
304
305 ret = key_validate(key);
306 if (ret == 0)
307 ret = verify_signature(key, sig);
308
309 key_put(key);
310 return ret;
311}
312
313/**
314 * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
315 * keys using the restrict_key information stored in the ring.
316 * @dest_keyring: Keyring being linked to.
317 * @type: The type of key being added.
318 * @payload: The payload of the new key.
319 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
320 *
321 * Check the new certificate only against the key or keys passed in the data
322 * parameter. If one of those is the signing key and validates the new
323 * certificate, then mark the new certificate as being ok to link.
324 *
325 * Returns 0 if the new certificate was accepted, -ENOKEY if we
326 * couldn't find a matching parent certificate in the trusted list,
327 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
328 * unsupported crypto, or some other error if there is a matching certificate
329 * but the signature check cannot be performed.
330 */
331int restrict_link_by_key_or_keyring(struct key *dest_keyring,
332 const struct key_type *type,
333 const union key_payload *payload,
334 struct key *trusted)
335{
336 return key_or_keyring_common(dest_keyring, type, payload, trusted,
337 check_dest: false);
338}
339
340/**
341 * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
342 * public keys using the restrict_key information stored in the ring.
343 * @dest_keyring: Keyring being linked to.
344 * @type: The type of key being added.
345 * @payload: The payload of the new key.
346 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
347 *
348 * Check the new certificate against the key or keys passed in the data
349 * parameter and against the keys already linked to the destination keyring. If
350 * one of those is the signing key and validates the new certificate, then mark
351 * the new certificate as being ok to link.
352 *
353 * Returns 0 if the new certificate was accepted, -ENOKEY if we
354 * couldn't find a matching parent certificate in the trusted list,
355 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
356 * unsupported crypto, or some other error if there is a matching certificate
357 * but the signature check cannot be performed.
358 */
359int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
360 const struct key_type *type,
361 const union key_payload *payload,
362 struct key *trusted)
363{
364 return key_or_keyring_common(dest_keyring, type, payload, trusted,
365 check_dest: true);
366}
367

source code of linux/crypto/asymmetric_keys/restrict.c