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David Howellscfb664f2016-04-06 16:14:26 +01001/* Instantiate a public key crypto key from an X.509 Certificate
2 *
David Howellsa511e1a2016-04-06 16:14:26 +01003 * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
David Howellscfb664f2016-04-06 16:14:26 +01004 * 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
David Howellsa511e1a2016-04-06 16:14:26 +010012#define pr_fmt(fmt) "ASYM: "fmt
David Howellscfb664f2016-04-06 16:14:26 +010013#include <linux/module.h>
14#include <linux/kernel.h>
David Howellscfb664f2016-04-06 16:14:26 +010015#include <linux/err.h>
David Howellscfb664f2016-04-06 16:14:26 +010016#include <crypto/public_key.h>
17#include "asymmetric_keys.h"
David Howellscfb664f2016-04-06 16:14:26 +010018
19static bool use_builtin_keys;
20static struct asymmetric_key_id *ca_keyid;
21
22#ifndef MODULE
23static struct {
24 struct asymmetric_key_id id;
25 unsigned char data[10];
26} cakey;
27
28static 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
David Howellsa511e1a2016-04-06 16:14:26 +010057/**
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 *
David Howellscfb664f2016-04-06 16:14:26 +010063 * 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 *
David Howellsa511e1a2016-04-06 16:14:26 +010067 * 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.
David Howellscfb664f2016-04-06 16:14:26 +010071 */
David Howellsa511e1a2016-04-06 16:14:26 +010072int restrict_link_by_signature(struct key *trust_keyring,
73 const struct key_type *type,
74 const union key_payload *payload)
David Howellscfb664f2016-04-06 16:14:26 +010075{
David Howellsa511e1a2016-04-06 16:14:26 +010076 const struct public_key_signature *sig;
David Howellscfb664f2016-04-06 16:14:26 +010077 struct key *key;
David Howellsa511e1a2016-04-06 16:14:26 +010078 int ret;
David Howellscfb664f2016-04-06 16:14:26 +010079
David Howellsa511e1a2016-04-06 16:14:26 +010080 pr_devel("==>%s()\n", __func__);
David Howellscfb664f2016-04-06 16:14:26 +010081
82 if (!trust_keyring)
David Howellsa511e1a2016-04-06 16:14:26 +010083 return -ENOKEY;
84
85 if (type != &key_type_asymmetric)
David Howellscfb664f2016-04-06 16:14:26 +010086 return -EOPNOTSUPP;
David Howellsa511e1a2016-04-06 16:14:26 +010087
88 sig = payload->data[asym_auth];
89 if (!sig->auth_ids[0] && !sig->auth_ids[1])
90 return 0;
91
David Howellscfb664f2016-04-06 16:14:26 +010092 if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
93 return -EPERM;
David Howellscfb664f2016-04-06 16:14:26 +010094
David Howellsa511e1a2016-04-06 16:14:26 +010095 /* See if we have a key that signed this one. */
David Howellscfb664f2016-04-06 16:14:26 +010096 key = find_asymmetric_key(trust_keyring,
97 sig->auth_ids[0], sig->auth_ids[1],
98 false);
99 if (IS_ERR(key))
David Howellsa511e1a2016-04-06 16:14:26 +0100100 return -ENOKEY;
David Howellscfb664f2016-04-06 16:14:26 +0100101
David Howellsa511e1a2016-04-06 16:14:26 +0100102 if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
103 ret = -ENOKEY;
104 else
105 ret = verify_signature(key, sig);
David Howellscfb664f2016-04-06 16:14:26 +0100106 key_put(key);
107 return ret;
108}