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  * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
  60  * @type: The type of key being added.
  61  * @payload: The payload of the new key.
  62  *
  63  * Check the new certificate against the ones in the trust keyring.  If one of
  64  * those is the signing key and validates the new certificate, then mark the
  65  * new certificate as being trusted.
  66  *
  67  * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
  68  * matching parent certificate in the trusted list, -EKEYREJECTED if the
  69  * signature check fails or the key is blacklisted and some other error if
  70  * there is a matching certificate but the signature check cannot be performed.
  71  */
  72 int restrict_link_by_signature(struct key *trust_keyring,
  73                                const struct key_type *type,
  74                                const union key_payload *payload)
  75 {
  76         const struct public_key_signature *sig;
  77         struct key *key;
  78         int ret;
  79
  80         pr_devel("==>%s()\n", __func__);
  81
  82         if (!trust_keyring)
  83                 return -ENOKEY;
  84
  85         if (type != &key_type_asymmetric)
  86                 return -EOPNOTSUPP;
  87
  88         sig = payload->data[asym_auth];
  89         if (!sig->auth_ids[0] && !sig->auth_ids[1])
  90                 return -ENOKEY;
  91
  92         if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
  93                 return -EPERM;
  94
  95         /* See if we have a key that signed this one. */
  96         key = find_asymmetric_key(trust_keyring,
  97                                   sig->auth_ids[0], sig->auth_ids[1],
  98                                   false);
  99         if (IS_ERR(key))
 100                 return -ENOKEY;
 101
 102         if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
 103                 ret = -ENOKEY;
 104         else
 105                 ret = verify_signature(key, sig);
 106         key_put(key);
 107         return ret;
 108 }