1 /* Testing module to load key from trusted PKCS#7 message
2  *
3  * Copyright (C) 2014 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) "PKCS7key: "fmt
13 #include <linux/key.h>
14 #include <linux/err.h>
15 #include <linux/module.h>
16 #include <linux/key-type.h>
17 #include <keys/asymmetric-type.h>
18 #include <crypto/pkcs7.h>
19 #include <keys/user-type.h>
20 #include <keys/system_keyring.h>
21 #include "pkcs7_parser.h"
22 
23 MODULE_LICENSE("GPL");
24 MODULE_DESCRIPTION("PKCS#7 testing key type");
25 
26 static unsigned pkcs7_usage;
27 module_param_named(usage, pkcs7_usage, uint, S_IWUSR | S_IRUGO);
28 MODULE_PARM_DESC(pkcs7_usage,
29 		 "Usage to specify when verifying the PKCS#7 message");
30 
31 /*
32  * Preparse a PKCS#7 wrapped and validated data blob.
33  */
34 static int pkcs7_preparse(struct key_preparsed_payload *prep)
35 {
36 	enum key_being_used_for usage = pkcs7_usage;
37 	struct pkcs7_message *pkcs7;
38 	const void *data, *saved_prep_data;
39 	size_t datalen, saved_prep_datalen;
40 	bool trusted;
41 	int ret;
42 
43 	kenter("");
44 
45 	if (usage >= NR__KEY_BEING_USED_FOR) {
46 		pr_err("Invalid usage type %d\n", usage);
47 		return -EINVAL;
48 	}
49 
50 	saved_prep_data = prep->data;
51 	saved_prep_datalen = prep->datalen;
52 	pkcs7 = pkcs7_parse_message(saved_prep_data, saved_prep_datalen);
53 	if (IS_ERR(pkcs7)) {
54 		ret = PTR_ERR(pkcs7);
55 		goto error;
56 	}
57 
58 	ret = pkcs7_verify(pkcs7, usage);
59 	if (ret < 0)
60 		goto error_free;
61 
62 	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
63 	if (ret < 0)
64 		goto error_free;
65 	if (!trusted)
66 		pr_warn("PKCS#7 message doesn't chain back to a trusted key\n");
67 
68 	ret = pkcs7_get_content_data(pkcs7, &data, &datalen, false);
69 	if (ret < 0)
70 		goto error_free;
71 
72 	prep->data = data;
73 	prep->datalen = datalen;
74 	ret = user_preparse(prep);
75 	prep->data = saved_prep_data;
76 	prep->datalen = saved_prep_datalen;
77 
78 error_free:
79 	pkcs7_free_message(pkcs7);
80 error:
81 	kleave(" = %d", ret);
82 	return ret;
83 }
84 
85 /*
86  * user defined keys take an arbitrary string as the description and an
87  * arbitrary blob of data as the payload
88  */
89 static struct key_type key_type_pkcs7 = {
90 	.name			= "pkcs7_test",
91 	.preparse		= pkcs7_preparse,
92 	.free_preparse		= user_free_preparse,
93 	.instantiate		= generic_key_instantiate,
94 	.revoke			= user_revoke,
95 	.destroy		= user_destroy,
96 	.describe		= user_describe,
97 	.read			= user_read,
98 };
99 
100 /*
101  * Module stuff
102  */
103 static int __init pkcs7_key_init(void)
104 {
105 	return register_key_type(&key_type_pkcs7);
106 }
107 
108 static void __exit pkcs7_key_cleanup(void)
109 {
110 	unregister_key_type(&key_type_pkcs7);
111 }
112 
113 module_init(pkcs7_key_init);
114 module_exit(pkcs7_key_cleanup);
115