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 <linux/string.h>
15 #include <linux/verification.h>
16 #include <crypto/public_key.h>
17 #include "module-internal.h"
18
19 enum pkey_id_type {
20 PKEY_ID_PGP, /* OpenPGP generated key ID */
21 PKEY_ID_X509, /* X.509 arbitrary subjectKeyIdentifier */
22 PKEY_ID_PKCS7, /* Signature in PKCS#7 message */
23 };
24
25 /*
26 * Module signature information block.
27 *
28 * The constituents of the signature section are, in order:
29 *
30 * - Signer's name
31 * - Key identifier
32 * - Signature data
33 * - Information block
34 */
35 struct module_signature {
36 u8 algo; /* Public-key crypto algorithm [0] */
37 u8 hash; /* Digest algorithm [0] */
38 u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */
39 u8 signer_len; /* Length of signer's name [0] */
40 u8 key_id_len; /* Length of key identifier [0] */
41 u8 __pad[3];
42 __be32 sig_len; /* Length of signature data */
43 };
44
45 /*
46 * Verify the signature on a module.
47 */
mod_verify_sig(const void * mod,unsigned long * _modlen)48 int mod_verify_sig(const void *mod, unsigned long *_modlen)
49 {
50 struct module_signature ms;
51 size_t modlen = *_modlen, sig_len;
52
53 pr_devel("==>%s(,%zu)\n", __func__, modlen);
54
55 if (modlen <= sizeof(ms))
56 return -EBADMSG;
57
58 memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
59 modlen -= sizeof(ms);
60
61 sig_len = be32_to_cpu(ms.sig_len);
62 if (sig_len >= modlen)
63 return -EBADMSG;
64 modlen -= sig_len;
65 *_modlen = modlen;
66
67 if (ms.id_type != PKEY_ID_PKCS7) {
68 pr_err("Module is not signed with expected PKCS#7 message\n");
69 return -ENOPKG;
70 }
71
72 if (ms.algo != 0 ||
73 ms.hash != 0 ||
74 ms.signer_len != 0 ||
75 ms.key_id_len != 0 ||
76 ms.__pad[0] != 0 ||
77 ms.__pad[1] != 0 ||
78 ms.__pad[2] != 0) {
79 pr_err("PKCS#7 signature info has unexpected non-zero params\n");
80 return -EBADMSG;
81 }
82
83 return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
84 NULL, VERIFYING_MODULE_SIGNATURE,
85 NULL, NULL);
86 }
87