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Linux/crypto/asymmetric_keys/restrict.c

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  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 
 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  */
 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])
 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                                   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 static bool match_either_id(const struct asymmetric_key_ids *pair,
112                             const struct asymmetric_key_id *single)
113 {
114         return (asymmetric_key_id_same(pair->id[0], single) ||
115                 asymmetric_key_id_same(pair->id[1], single));
116 }
117 
118 static int key_or_keyring_common(struct key *dest_keyring,
119                                  const struct key_type *type,
120                                  const union key_payload *payload,
121                                  struct key *trusted, bool check_dest)
122 {
123         const struct public_key_signature *sig;
124         struct key *key = NULL;
125         int ret;
126 
127         pr_devel("==>%s()\n", __func__);
128 
129         if (!dest_keyring)
130                 return -ENOKEY;
131         else if (dest_keyring->type != &key_type_keyring)
132                 return -EOPNOTSUPP;
133 
134         if (!trusted && !check_dest)
135                 return -ENOKEY;
136 
137         if (type != &key_type_asymmetric)
138                 return -EOPNOTSUPP;
139 
140         sig = payload->data[asym_auth];
141         if (!sig)
142                 return -ENOPKG;
143         if (!sig->auth_ids[0] && !sig->auth_ids[1])
144                 return -ENOKEY;
145 
146         if (trusted) {
147                 if (trusted->type == &key_type_keyring) {
148                         /* See if we have a key that signed this one. */
149                         key = find_asymmetric_key(trusted, sig->auth_ids[0],
150                                                   sig->auth_ids[1], false);
151                         if (IS_ERR(key))
152                                 key = NULL;
153                 } else if (trusted->type == &key_type_asymmetric) {
154                         const struct asymmetric_key_ids *signer_ids;
155 
156                         signer_ids = asymmetric_key_ids(trusted);
157 
158                         /*
159                          * The auth_ids come from the candidate key (the
160                          * one that is being considered for addition to
161                          * dest_keyring) and identify the key that was
162                          * used to sign.
163                          *
164                          * The signer_ids are identifiers for the
165                          * signing key specified for dest_keyring.
166                          *
167                          * The first auth_id is the preferred id, and
168                          * the second is the fallback. If only one
169                          * auth_id is present, it may match against
170                          * either signer_id. If two auth_ids are
171                          * present, the first auth_id must match one
172                          * signer_id and the second auth_id must match
173                          * the second signer_id.
174                          */
175                         if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
176                                 const struct asymmetric_key_id *auth_id;
177 
178                                 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
179                                 if (match_either_id(signer_ids, auth_id))
180                                         key = __key_get(trusted);
181 
182                         } else if (asymmetric_key_id_same(signer_ids->id[1],
183                                                           sig->auth_ids[1]) &&
184                                    match_either_id(signer_ids,
185                                                    sig->auth_ids[0])) {
186                                 key = __key_get(trusted);
187                         }
188                 } else {
189                         return -EOPNOTSUPP;
190                 }
191         }
192 
193         if (check_dest && !key) {
194                 /* See if the destination has a key that signed this one. */
195                 key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
196                                           sig->auth_ids[1], false);
197                 if (IS_ERR(key))
198                         key = NULL;
199         }
200 
201         if (!key)
202                 return -ENOKEY;
203 
204         ret = key_validate(key);
205         if (ret == 0)
206                 ret = verify_signature(key, sig);
207 
208         key_put(key);
209         return ret;
210 }
211 
212 /**
213  * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
214  * keys using the restrict_key information stored in the ring.
215  * @dest_keyring: Keyring being linked to.
216  * @type: The type of key being added.
217  * @payload: The payload of the new key.
218  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
219  *
220  * Check the new certificate only against the key or keys passed in the data
221  * parameter. If one of those is the signing key and validates the new
222  * certificate, then mark the new certificate as being ok to link.
223  *
224  * Returns 0 if the new certificate was accepted, -ENOKEY if we
225  * couldn't find a matching parent certificate in the trusted list,
226  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
227  * unsupported crypto, or some other error if there is a matching certificate
228  * but the signature check cannot be performed.
229  */
230 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
231                                     const struct key_type *type,
232                                     const union key_payload *payload,
233                                     struct key *trusted)
234 {
235         return key_or_keyring_common(dest_keyring, type, payload, trusted,
236                                      false);
237 }
238 
239 /**
240  * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
241  * public keys using the restrict_key information stored in the ring.
242  * @dest_keyring: Keyring being linked to.
243  * @type: The type of key being added.
244  * @payload: The payload of the new key.
245  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
246  *
247  * Check the new certificate only against the key or keys passed in the data
248  * parameter. If one of those is the signing key and validates the new
249  * certificate, then mark the new certificate as being ok to link.
250  *
251  * Returns 0 if the new certificate was accepted, -ENOKEY if we
252  * couldn't find a matching parent certificate in the trusted list,
253  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
254  * unsupported crypto, or some other error if there is a matching certificate
255  * but the signature check cannot be performed.
256  */
257 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
258                                           const struct key_type *type,
259                                           const union key_payload *payload,
260                                           struct key *trusted)
261 {
262         return key_or_keyring_common(dest_keyring, type, payload, trusted,
263                                      true);
264 }
265 

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