crypto/asymmetric_keys/restrict.c

   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 and some other error if
  71  * there is a matching certificate but the signature check cannot be performed.
  72  */
  73 int 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->auth_ids[0] && !sig->auth_ids[1])
  92                 return -ENOKEY;
  93
  94         if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
  95                 return -EPERM;
  96
  97         /* See if we have a key that signed this one. */
  98         key = find_asymmetric_key(trust_keyring,
  99                                   sig->auth_ids[0], sig->auth_ids[1],
 100                                   false);
 101         if (IS_ERR(key))
 102                 return -ENOKEY;
 103
 104         if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
 105                 ret = -ENOKEY;
 106         else
 107                 ret = verify_signature(key, sig);
 108         key_put(key);
 109         return ret;
 110 }
 111
 112 static bool match_either_id(const struct asymmetric_key_ids *pair,
 113                             const struct asymmetric_key_id *single)
 114 {
 115         return (asymmetric_key_id_same(pair->id[0], single) ||
 116                 asymmetric_key_id_same(pair->id[1], single));
 117 }
 118
 119 static int key_or_keyring_common(struct key *dest_keyring,
 120                                  const struct key_type *type,
 121                                  const union key_payload *payload,
 122                                  struct key *trusted, bool check_dest)
 123 {
 124         const struct public_key_signature *sig;
 125         struct key *key = NULL;
 126         int ret;
 127
 128         pr_devel("==>%s()\n", __func__);
 129
 130         if (!dest_keyring)
 131                 return -ENOKEY;
 132         else if (dest_keyring->type != &key_type_keyring)
 133                 return -EOPNOTSUPP;
 134
 135         if (!trusted && !check_dest)
 136                 return -ENOKEY;
 137
 138         if (type != &key_type_asymmetric)
 139                 return -EOPNOTSUPP;
 140
 141         sig = payload->data[asym_auth];
 142         if (!sig->auth_ids[0] && !sig->auth_ids[1])
 143                 return -ENOKEY;
 144
 145         if (trusted) {
 146                 if (trusted->type == &key_type_keyring) {
 147                         /* See if we have a key that signed this one. */
 148                         key = find_asymmetric_key(trusted, sig->auth_ids[0],
 149                                                   sig->auth_ids[1], false);
 150                         if (IS_ERR(key))
 151                                 key = NULL;
 152                 } else if (trusted->type == &key_type_asymmetric) {
 153                         const struct asymmetric_key_ids *signer_ids;
 154
 155                         signer_ids = asymmetric_key_ids(trusted);
 156
 157                         /*
 158                          * The auth_ids come from the candidate key (the
 159                          * one that is being considered for addition to
 160                          * dest_keyring) and identify the key that was
 161                          * used to sign.
 162                          *
 163                          * The signer_ids are identifiers for the
 164                          * signing key specified for dest_keyring.
 165                          *
 166                          * The first auth_id is the preferred id, and
 167                          * the second is the fallback. If only one
 168                          * auth_id is present, it may match against
 169                          * either signer_id. If two auth_ids are
 170                          * present, the first auth_id must match one
 171                          * signer_id and the second auth_id must match
 172                          * the second signer_id.
 173                          */
 174                         if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
 175                                 const struct asymmetric_key_id *auth_id;
 176
 177                                 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
 178                                 if (match_either_id(signer_ids, auth_id))
 179                                         key = __key_get(trusted);
 180
 181                         } else if (asymmetric_key_id_same(signer_ids->id[1],
 182                                                           sig->auth_ids[1]) &&
 183                                    match_either_id(signer_ids,
 184                                                    sig->auth_ids[0])) {
 185                                 key = __key_get(trusted);
 186                         }
 187                 } else {
 188                         return -EOPNOTSUPP;
 189                 }
 190         }
 191
 192         if (check_dest && !key) {
 193                 /* See if the destination has a key that signed this one. */
 194                 key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
 195                                           sig->auth_ids[1], false);
 196                 if (IS_ERR(key))
 197                         key = NULL;
 198         }
 199
 200         if (!key)
 201                 return -ENOKEY;
 202
 203         ret = key_validate(key);
 204         if (ret == 0)
 205                 ret = verify_signature(key, sig);
 206
 207         key_put(key);
 208         return ret;
 209 }
 210
 211 /**
 212  * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
 213  * keys using the restrict_key information stored in the ring.
 214  * @dest_keyring: Keyring being linked to.
 215  * @type: The type of key being added.
 216  * @payload: The payload of the new key.
 217  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 218  *
 219  * Check the new certificate only against the key or keys passed in the data
 220  * parameter. If one of those is the signing key and validates the new
 221  * certificate, then mark the new certificate as being ok to link.
 222  *
 223  * Returns 0 if the new certificate was accepted, -ENOKEY if we
 224  * couldn't find a matching parent certificate in the trusted list,
 225  * -EKEYREJECTED if the signature check fails, and some other error if
 226  * there is a matching certificate but the signature check cannot be
 227  * performed.
 228  */
 229 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
 230                                     const struct key_type *type,
 231                                     const union key_payload *payload,
 232                                     struct key *trusted)
 233 {
 234         return key_or_keyring_common(dest_keyring, type, payload, trusted,
 235                                      false);
 236 }
 237
 238 /**
 239  * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
 240  * public keys using the restrict_key information stored in the ring.
 241  * @dest_keyring: Keyring being linked to.
 242  * @type: The type of key being added.
 243  * @payload: The payload of the new key.
 244  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 245  *
 246  * Check the new certificate only against the key or keys passed in the data
 247  * parameter. If one of those is the signing key and validates the new
 248  * certificate, then mark the new certificate as being ok to link.
 249  *
 250  * Returns 0 if the new certificate was accepted, -ENOKEY if we
 251  * couldn't find a matching parent certificate in the trusted list,
 252  * -EKEYREJECTED if the signature check fails, and some other error if
 253  * there is a matching certificate but the signature check cannot be
 254  * performed.
 255  */
 256 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
 257                                           const struct key_type *type,
 258                                           const union key_payload *payload,
 259                                           struct key *trusted)
 260 {
 261         return key_or_keyring_common(dest_keyring, type, payload, trusted,
 262                                      true);
 263 }