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, -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 }