1/* Module signature checker
2 *
3 * Copyright (C) 2012 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#include <linux/kernel.h>
13#include <linux/errno.h>
14#include <keys/system_keyring.h>
15#include <crypto/public_key.h>
16#include "module-internal.h"
17
18/*
19 * Module signature information block.
20 *
21 * The constituents of the signature section are, in order:
22 *
23 *	- Signer's name
24 *	- Key identifier
25 *	- Signature data
26 *	- Information block
27 */
28struct module_signature {
29	u8	algo;		/* Public-key crypto algorithm [0] */
30	u8	hash;		/* Digest algorithm [0] */
31	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
32	u8	signer_len;	/* Length of signer's name [0] */
33	u8	key_id_len;	/* Length of key identifier [0] */
34	u8	__pad[3];
35	__be32	sig_len;	/* Length of signature data */
36};
37
38/*
39 * Verify the signature on a module.
40 */
41int mod_verify_sig(const void *mod, unsigned long *_modlen)
42{
43	struct module_signature ms;
44	size_t modlen = *_modlen, sig_len;
45
46	pr_devel("==>%s(,%zu)\n", __func__, modlen);
47
48	if (modlen <= sizeof(ms))
49		return -EBADMSG;
50
51	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
52	modlen -= sizeof(ms);
53
54	sig_len = be32_to_cpu(ms.sig_len);
55	if (sig_len >= modlen)
56		return -EBADMSG;
57	modlen -= sig_len;
58	*_modlen = modlen;
59
60	if (ms.id_type != PKEY_ID_PKCS7) {
61		pr_err("Module is not signed with expected PKCS#7 message\n");
62		return -ENOPKG;
63	}
64
65	if (ms.algo != 0 ||
66	    ms.hash != 0 ||
67	    ms.signer_len != 0 ||
68	    ms.key_id_len != 0 ||
69	    ms.__pad[0] != 0 ||
70	    ms.__pad[1] != 0 ||
71	    ms.__pad[2] != 0) {
72		pr_err("PKCS#7 signature info has unexpected non-zero params\n");
73		return -EBADMSG;
74	}
75
76	return system_verify_data(mod, modlen, mod + modlen, sig_len,
77				  VERIFYING_MODULE_SIGNATURE);
78}
79