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
15 static bool use_builtin_keys;
16 static struct asymmetric_key_id *ca_keyid;
17
18 #ifndef MODULE
19 static struct {
20 struct asymmetric_key_id id;
21 unsigned char data[10];
22 } cakey;
23
ca_keys_setup(char * str)24 static 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(str + 3, 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 */
restrict_link_by_signature(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trust_keyring)70 int 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(sig->auth_ids[1], ca_keyid))
94 return -EPERM;
95
96 /* See if we have a key that signed this one. */
97 key = find_asymmetric_key(trust_keyring,
98 sig->auth_ids[0], sig->auth_ids[1],
99 sig->auth_ids[2], false);
100 if (IS_ERR(key))
101 return -ENOKEY;
102
103 if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
104 ret = -ENOKEY;
105 else
106 ret = verify_signature(key, sig);
107 key_put(key);
108 return ret;
109 }
110
111 /**
112 * restrict_link_by_ca - Restrict additions to a ring of CA keys
113 * @dest_keyring: Keyring being linked to.
114 * @type: The type of key being added.
115 * @payload: The payload of the new key.
116 * @trust_keyring: Unused.
117 *
118 * Check if the new certificate is a CA. If it is a CA, then mark the new
119 * certificate as being ok to link.
120 *
121 * Returns 0 if the new certificate was accepted, -ENOKEY if the
122 * certificate is not a CA. -ENOPKG if the signature uses unsupported
123 * crypto, or some other error if there is a matching certificate but
124 * the signature check cannot be performed.
125 */
restrict_link_by_ca(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trust_keyring)126 int restrict_link_by_ca(struct key *dest_keyring,
127 const struct key_type *type,
128 const union key_payload *payload,
129 struct key *trust_keyring)
130 {
131 const struct public_key *pkey;
132
133 if (type != &key_type_asymmetric)
134 return -EOPNOTSUPP;
135
136 pkey = payload->data[asym_crypto];
137 if (!pkey)
138 return -ENOPKG;
139 if (!test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
140 return -ENOKEY;
141 if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
142 return -ENOKEY;
143 if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX))
144 return 0;
145 if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
146 return -ENOKEY;
147
148 return 0;
149 }
150
151 /**
152 * restrict_link_by_digsig - Restrict additions to a ring of digsig keys
153 * @dest_keyring: Keyring being linked to.
154 * @type: The type of key being added.
155 * @payload: The payload of the new key.
156 * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
157 *
158 * Check if the new certificate has digitalSignature usage set. If it is,
159 * then mark the new certificate as being ok to link. Afterwards verify
160 * the new certificate against the ones in the trust_keyring.
161 *
162 * Returns 0 if the new certificate was accepted, -ENOKEY if the
163 * certificate is not a digsig. -ENOPKG if the signature uses unsupported
164 * crypto, or some other error if there is a matching certificate but
165 * the signature check cannot be performed.
166 */
restrict_link_by_digsig(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trust_keyring)167 int restrict_link_by_digsig(struct key *dest_keyring,
168 const struct key_type *type,
169 const union key_payload *payload,
170 struct key *trust_keyring)
171 {
172 const struct public_key *pkey;
173
174 if (type != &key_type_asymmetric)
175 return -EOPNOTSUPP;
176
177 pkey = payload->data[asym_crypto];
178
179 if (!pkey)
180 return -ENOPKG;
181
182 if (!test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
183 return -ENOKEY;
184
185 if (test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
186 return -ENOKEY;
187
188 if (test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
189 return -ENOKEY;
190
191 return restrict_link_by_signature(dest_keyring, type, payload,
192 trust_keyring);
193 }
194
match_either_id(const struct asymmetric_key_id ** pair,const struct asymmetric_key_id * single)195 static bool match_either_id(const struct asymmetric_key_id **pair,
196 const struct asymmetric_key_id *single)
197 {
198 return (asymmetric_key_id_same(pair[0], single) ||
199 asymmetric_key_id_same(pair[1], single));
200 }
201
key_or_keyring_common(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trusted,bool check_dest)202 static int key_or_keyring_common(struct key *dest_keyring,
203 const struct key_type *type,
204 const union key_payload *payload,
205 struct key *trusted, bool check_dest)
206 {
207 const struct public_key_signature *sig;
208 struct key *key = NULL;
209 int ret;
210
211 pr_devel("==>%s()\n", __func__);
212
213 if (!dest_keyring)
214 return -ENOKEY;
215 else if (dest_keyring->type != &key_type_keyring)
216 return -EOPNOTSUPP;
217
218 if (!trusted && !check_dest)
219 return -ENOKEY;
220
221 if (type != &key_type_asymmetric)
222 return -EOPNOTSUPP;
223
224 sig = payload->data[asym_auth];
225 if (!sig)
226 return -ENOPKG;
227 if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
228 return -ENOKEY;
229
230 if (trusted) {
231 if (trusted->type == &key_type_keyring) {
232 /* See if we have a key that signed this one. */
233 key = find_asymmetric_key(trusted, sig->auth_ids[0],
234 sig->auth_ids[1],
235 sig->auth_ids[2], false);
236 if (IS_ERR(key))
237 key = NULL;
238 } else if (trusted->type == &key_type_asymmetric) {
239 const struct asymmetric_key_id **signer_ids;
240
241 signer_ids = (const struct asymmetric_key_id **)
242 asymmetric_key_ids(trusted)->id;
243
244 /*
245 * The auth_ids come from the candidate key (the
246 * one that is being considered for addition to
247 * dest_keyring) and identify the key that was
248 * used to sign.
249 *
250 * The signer_ids are identifiers for the
251 * signing key specified for dest_keyring.
252 *
253 * The first auth_id is the preferred id, 2nd and
254 * 3rd are the fallbacks. If exactly one of
255 * auth_ids[0] and auth_ids[1] is present, it may
256 * match either signer_ids[0] or signed_ids[1].
257 * If both are present the first one may match
258 * either signed_id but the second one must match
259 * the second signer_id. If neither of them is
260 * available, auth_ids[2] is matched against
261 * signer_ids[2] as a fallback.
262 */
263 if (!sig->auth_ids[0] && !sig->auth_ids[1]) {
264 if (asymmetric_key_id_same(signer_ids[2],
265 sig->auth_ids[2]))
266 key = __key_get(trusted);
267
268 } else if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
269 const struct asymmetric_key_id *auth_id;
270
271 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
272 if (match_either_id(signer_ids, auth_id))
273 key = __key_get(trusted);
274
275 } else if (asymmetric_key_id_same(signer_ids[1],
276 sig->auth_ids[1]) &&
277 match_either_id(signer_ids,
278 sig->auth_ids[0])) {
279 key = __key_get(trusted);
280 }
281 } else {
282 return -EOPNOTSUPP;
283 }
284 }
285
286 if (check_dest && !key) {
287 /* See if the destination has a key that signed this one. */
288 key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
289 sig->auth_ids[1], sig->auth_ids[2],
290 false);
291 if (IS_ERR(key))
292 key = NULL;
293 }
294
295 if (!key)
296 return -ENOKEY;
297
298 ret = key_validate(key);
299 if (ret == 0)
300 ret = verify_signature(key, sig);
301
302 key_put(key);
303 return ret;
304 }
305
306 /**
307 * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
308 * keys using the restrict_key information stored in the ring.
309 * @dest_keyring: Keyring being linked to.
310 * @type: The type of key being added.
311 * @payload: The payload of the new key.
312 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
313 *
314 * Check the new certificate only against the key or keys passed in the data
315 * parameter. If one of those is the signing key and validates the new
316 * certificate, then mark the new certificate as being ok to link.
317 *
318 * Returns 0 if the new certificate was accepted, -ENOKEY if we
319 * couldn't find a matching parent certificate in the trusted list,
320 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
321 * unsupported crypto, or some other error if there is a matching certificate
322 * but the signature check cannot be performed.
323 */
restrict_link_by_key_or_keyring(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trusted)324 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
325 const struct key_type *type,
326 const union key_payload *payload,
327 struct key *trusted)
328 {
329 return key_or_keyring_common(dest_keyring, type, payload, trusted,
330 false);
331 }
332
333 /**
334 * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
335 * public keys using the restrict_key information stored in the ring.
336 * @dest_keyring: Keyring being linked to.
337 * @type: The type of key being added.
338 * @payload: The payload of the new key.
339 * @trusted: A key or ring of keys that can be used to vouch for the new cert.
340 *
341 * Check the new certificate against the key or keys passed in the data
342 * parameter and against the keys already linked to the destination keyring. If
343 * one of those is the signing key and validates the new certificate, then mark
344 * the new certificate as being ok to link.
345 *
346 * Returns 0 if the new certificate was accepted, -ENOKEY if we
347 * couldn't find a matching parent certificate in the trusted list,
348 * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
349 * unsupported crypto, or some other error if there is a matching certificate
350 * but the signature check cannot be performed.
351 */
restrict_link_by_key_or_keyring_chain(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * trusted)352 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
353 const struct key_type *type,
354 const union key_payload *payload,
355 struct key *trusted)
356 {
357 return key_or_keyring_common(dest_keyring, type, payload, trusted,
358 true);
359 }
360
