crypto/asymmetric_keys/restrict.c

   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 }