1 /* Signature verification with an asymmetric key
2  *
3  * See Documentation/security/asymmetric-keys.txt
4  *
5  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
6  * Written by David Howells (dhowells@redhat.com)
7  *
8  * This program is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU General Public Licence
10  * as published by the Free Software Foundation; either version
11  * 2 of the Licence, or (at your option) any later version.
12  */
13 
14 #define pr_fmt(fmt) "SIG: "fmt
15 #include <keys/asymmetric-subtype.h>
16 #include <linux/export.h>
17 #include <linux/err.h>
18 #include <linux/slab.h>
19 #include <crypto/public_key.h>
20 #include "asymmetric_keys.h"
21 
22 /*
23  * Destroy a public key signature.
24  */
25 void public_key_signature_free(struct public_key_signature *sig)
26 {
27 	int i;
28 
29 	if (sig) {
30 		for (i = 0; i < ARRAY_SIZE(sig->auth_ids); i++)
31 			kfree(sig->auth_ids[i]);
32 		kfree(sig->s);
33 		kfree(sig->digest);
34 		kfree(sig);
35 	}
36 }
37 EXPORT_SYMBOL_GPL(public_key_signature_free);
38 
39 /**
40  * verify_signature - Initiate the use of an asymmetric key to verify a signature
41  * @key: The asymmetric key to verify against
42  * @sig: The signature to check
43  *
44  * Returns 0 if successful or else an error.
45  */
46 int verify_signature(const struct key *key,
47 		     const struct public_key_signature *sig)
48 {
49 	const struct asymmetric_key_subtype *subtype;
50 	int ret;
51 
52 	pr_devel("==>%s()\n", __func__);
53 
54 	if (key->type != &key_type_asymmetric)
55 		return -EINVAL;
56 	subtype = asymmetric_key_subtype(key);
57 	if (!subtype ||
58 	    !key->payload.data[0])
59 		return -EINVAL;
60 	if (!subtype->verify_signature)
61 		return -ENOTSUPP;
62 
63 	ret = subtype->verify_signature(key, sig);
64 
65 	pr_devel("<==%s() = %d\n", __func__, ret);
66 	return ret;
67 }
68 EXPORT_SYMBOL_GPL(verify_signature);
69