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 */
28 struct 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 */
mod_verify_sig(const void * mod,unsigned long * _modlen)41 int 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