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Linux/crypto/asymmetric_keys/restrict.c

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  1 /* Instantiate a public key crypto key from an X.509 Certificate
  2  *
  3  * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public Licence
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the Licence, or (at your option) any later version.
 10  */
 11 
 12 #define pr_fmt(fmt) "ASYM: "fmt
 13 #include <linux/module.h>
 14 #include <linux/kernel.h>
 15 #include <linux/err.h>
 16 #include <crypto/public_key.h>
 17 #include "asymmetric_keys.h"
 18 
 19 static bool use_builtin_keys;
 20 static struct asymmetric_key_id *ca_keyid;
 21 
 22 #ifndef MODULE
 23 static struct {
 24         struct asymmetric_key_id id;
 25         unsigned char data[10];
 26 } cakey;
 27 
 28 static int __init ca_keys_setup(char *str)
 29 {
 30         if (!str)               /* default system keyring */
 31                 return 1;
 32 
 33         if (strncmp(str, "id:", 3) == 0) {
 34                 struct asymmetric_key_id *p = &cakey.id;
 35                 size_t hexlen = (strlen(str) - 3) / 2;
 36                 int ret;
 37 
 38                 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
 39                         pr_err("Missing or invalid ca_keys id\n");
 40                         return 1;
 41                 }
 42 
 43                 ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
 44                 if (ret < 0)
 45                         pr_err("Unparsable ca_keys id hex string\n");
 46                 else
 47                         ca_keyid = p;   /* owner key 'id:xxxxxx' */
 48         } else if (strcmp(str, "builtin") == 0) {
 49                 use_builtin_keys = true;
 50         }
 51 
 52         return 1;
 53 }
 54 __setup("ca_keys=", ca_keys_setup);
 55 #endif
 56 
 57 /**
 58  * restrict_link_by_signature - Restrict additions to a ring of public keys
 59  * @dest_keyring: Keyring being linked to.
 60  * @type: The type of key being added.
 61  * @payload: The payload of the new key.
 62  * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
 63  *
 64  * Check the new certificate against the ones in the trust keyring.  If one of
 65  * those is the signing key and validates the new certificate, then mark the
 66  * new certificate as being trusted.
 67  *
 68  * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
 69  * matching parent certificate in the trusted list, -EKEYREJECTED if the
 70  * signature check fails or the key is blacklisted, -ENOPKG if the signature
 71  * uses unsupported crypto, or some other error if there is a matching
 72  * certificate but the signature check cannot be performed.
 73  */
 74 int restrict_link_by_signature(struct key *dest_keyring,
 75                                const struct key_type *type,
 76                                const union key_payload *payload,
 77                                struct key *trust_keyring)
 78 {
 79         const struct public_key_signature *sig;
 80         struct key *key;
 81         int ret;
 82 
 83         pr_devel("==>%s()\n", __func__);
 84 
 85         if (!trust_keyring)
 86                 return -ENOKEY;
 87 
 88         if (type != &key_type_asymmetric)
 89                 return -EOPNOTSUPP;
 90 
 91         sig = payload->data[asym_auth];
 92         if (!sig)
 93                 return -ENOPKG;
 94         if (!sig->auth_ids[0] && !sig->auth_ids[1])
 95                 return -ENOKEY;
 96 
 97         if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
 98                 return -EPERM;
 99 
100         /* See if we have a key that signed this one. */
101         key = find_asymmetric_key(trust_keyring,
102                                   sig->auth_ids[0], sig->auth_ids[1],
103                                   false);
104         if (IS_ERR(key))
105                 return -ENOKEY;
106 
107         if (use_builtin_keys && !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 static bool match_either_id(const struct asymmetric_key_ids *pair,
116                             const struct asymmetric_key_id *single)
117 {
118         return (asymmetric_key_id_same(pair->id[0], single) ||
119                 asymmetric_key_id_same(pair->id[1], single));
120 }
121 
122 static int key_or_keyring_common(struct key *dest_keyring,
123                                  const struct key_type *type,
124                                  const union key_payload *payload,
125                                  struct key *trusted, bool check_dest)
126 {
127         const struct public_key_signature *sig;
128         struct key *key = NULL;
129         int ret;
130 
131         pr_devel("==>%s()\n", __func__);
132 
133         if (!dest_keyring)
134                 return -ENOKEY;
135         else if (dest_keyring->type != &key_type_keyring)
136                 return -EOPNOTSUPP;
137 
138         if (!trusted && !check_dest)
139                 return -ENOKEY;
140 
141         if (type != &key_type_asymmetric)
142                 return -EOPNOTSUPP;
143 
144         sig = payload->data[asym_auth];
145         if (!sig)
146                 return -ENOPKG;
147         if (!sig->auth_ids[0] && !sig->auth_ids[1])
148                 return -ENOKEY;
149 
150         if (trusted) {
151                 if (trusted->type == &key_type_keyring) {
152                         /* See if we have a key that signed this one. */
153                         key = find_asymmetric_key(trusted, sig->auth_ids[0],
154                                                   sig->auth_ids[1], false);
155                         if (IS_ERR(key))
156                                 key = NULL;
157                 } else if (trusted->type == &key_type_asymmetric) {
158                         const struct asymmetric_key_ids *signer_ids;
159 
160                         signer_ids = asymmetric_key_ids(trusted);
161 
162                         /*
163                          * The auth_ids come from the candidate key (the
164                          * one that is being considered for addition to
165                          * dest_keyring) and identify the key that was
166                          * used to sign.
167                          *
168                          * The signer_ids are identifiers for the
169                          * signing key specified for dest_keyring.
170                          *
171                          * The first auth_id is the preferred id, and
172                          * the second is the fallback. If only one
173                          * auth_id is present, it may match against
174                          * either signer_id. If two auth_ids are
175                          * present, the first auth_id must match one
176                          * signer_id and the second auth_id must match
177                          * the second signer_id.
178                          */
179                         if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
180                                 const struct asymmetric_key_id *auth_id;
181 
182                                 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
183                                 if (match_either_id(signer_ids, auth_id))
184                                         key = __key_get(trusted);
185 
186                         } else if (asymmetric_key_id_same(signer_ids->id[1],
187                                                           sig->auth_ids[1]) &&
188                                    match_either_id(signer_ids,
189                                                    sig->auth_ids[0])) {
190                                 key = __key_get(trusted);
191                         }
192                 } else {
193                         return -EOPNOTSUPP;
194                 }
195         }
196 
197         if (check_dest && !key) {
198                 /* See if the destination has a key that signed this one. */
199                 key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
200                                           sig->auth_ids[1], false);
201                 if (IS_ERR(key))
202                         key = NULL;
203         }
204 
205         if (!key)
206                 return -ENOKEY;
207 
208         ret = key_validate(key);
209         if (ret == 0)
210                 ret = verify_signature(key, sig);
211 
212         key_put(key);
213         return ret;
214 }
215 
216 /**
217  * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
218  * keys using the restrict_key information stored in the ring.
219  * @dest_keyring: Keyring being linked to.
220  * @type: The type of key being added.
221  * @payload: The payload of the new key.
222  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
223  *
224  * Check the new certificate only against the key or keys passed in the data
225  * parameter. If one of those is the signing key and validates the new
226  * certificate, then mark the new certificate as being ok to link.
227  *
228  * Returns 0 if the new certificate was accepted, -ENOKEY if we
229  * couldn't find a matching parent certificate in the trusted list,
230  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
231  * unsupported crypto, or some other error if there is a matching certificate
232  * but the signature check cannot be performed.
233  */
234 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
235                                     const struct key_type *type,
236                                     const union key_payload *payload,
237                                     struct key *trusted)
238 {
239         return key_or_keyring_common(dest_keyring, type, payload, trusted,
240                                      false);
241 }
242 
243 /**
244  * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
245  * public keys using the restrict_key information stored in the ring.
246  * @dest_keyring: Keyring being linked to.
247  * @type: The type of key being added.
248  * @payload: The payload of the new key.
249  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
250  *
251  * Check the new certificate only against the key or keys passed in the data
252  * parameter. If one of those is the signing key and validates the new
253  * certificate, then mark the new certificate as being ok to link.
254  *
255  * Returns 0 if the new certificate was accepted, -ENOKEY if we
256  * couldn't find a matching parent certificate in the trusted list,
257  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
258  * unsupported crypto, or some other error if there is a matching certificate
259  * but the signature check cannot be performed.
260  */
261 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
262                                           const struct key_type *type,
263                                           const union key_payload *payload,
264                                           struct key *trusted)
265 {
266         return key_or_keyring_common(dest_keyring, type, payload, trusted,
267                                      true);
268 }
269 

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