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 }
109