summaryrefslogtreecommitdiff
path: root/security/integrity/digsig_asymmetric.c
blob: a29df775fdd8db55b17ac9ed27985be33eface11 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2013 Intel Corporation
 *
 * Author:
 * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/err.h>
#include <linux/ratelimit.h>
#include <linux/key-type.h>
#include <crypto/public_key.h>
#include <crypto/hash_info.h>
#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>

#include "integrity.h"

/*
 * Request an asymmetric key.
 */
static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
{
	struct key *key;
	char name[12];

	sprintf(name, "id:%08x", keyid);

	pr_debug("key search: \"%s\"\n", name);

	key = get_ima_blacklist_keyring();
	if (key) {
		key_ref_t kref;

		kref = keyring_search(make_key_ref(key, 1),
				      &key_type_asymmetric, name, true);
		if (!IS_ERR(kref)) {
			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
			return ERR_PTR(-EKEYREJECTED);
		}
	}

	if (keyring) {
		/* search in specific keyring */
		key_ref_t kref;

		kref = keyring_search(make_key_ref(keyring, 1),
				      &key_type_asymmetric, name, true);
		if (IS_ERR(kref))
			key = ERR_CAST(kref);
		else
			key = key_ref_to_ptr(kref);
	} else {
		key = request_key(&key_type_asymmetric, name, NULL, NULL);
	}

	if (IS_ERR(key)) {
		pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
				   name, PTR_ERR(key));
		switch (PTR_ERR(key)) {
			/* Hide some search errors */
		case -EACCES:
		case -ENOTDIR:
		case -EAGAIN:
			return ERR_PTR(-ENOKEY);
		default:
			return key;
		}
	}

	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));

	return key;
}

int asymmetric_verify(struct key *keyring, const char *sig,
		      int siglen, const char *data, int datalen)
{
	struct public_key_signature pks;
	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
	struct key *key;
	int ret = -ENOMEM;

	if (siglen <= sizeof(*hdr))
		return -EBADMSG;

	siglen -= sizeof(*hdr);

	if (siglen != be16_to_cpu(hdr->sig_size))
		return -EBADMSG;

	if (hdr->hash_algo >= HASH_ALGO__LAST)
		return -ENOPKG;

	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
	if (IS_ERR(key))
		return PTR_ERR(key);

	memset(&pks, 0, sizeof(pks));

	pks.hash_algo = hash_algo_name[hdr->hash_algo];
	if (hdr->hash_algo == HASH_ALGO_STREEBOG_256 ||
	    hdr->hash_algo == HASH_ALGO_STREEBOG_512) {
		/* EC-RDSA and Streebog should go together. */
		pks.pkey_algo = "ecrdsa";
		pks.encoding = "raw";
	} else {
		pks.pkey_algo = "rsa";
		pks.encoding = "pkcs1";
	}
	pks.digest = (u8 *)data;
	pks.digest_size = datalen;
	pks.s = hdr->sig;
	pks.s_size = siglen;
	ret = verify_signature(key, &pks);
	key_put(key);
	pr_debug("%s() = %d\n", __func__, ret);
	return ret;
}

/**
 * integrity_kernel_module_request - prevent crypto-pkcs1pad(rsa,*) requests
 * @kmod_name: kernel module name
 *
 * We have situation, when public_key_verify_signature() in case of RSA
 * algorithm use alg_name to store internal information in order to
 * construct an algorithm on the fly, but crypto_larval_lookup() will try
 * to use alg_name in order to load kernel module with same name.
 * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
 * we are safe to fail such module request from crypto_larval_lookup().
 *
 * In this way we prevent modprobe execution during digsig verification
 * and avoid possible deadlock if modprobe and/or it's dependencies
 * also signed with digsig.
 */
int integrity_kernel_module_request(char *kmod_name)
{
	if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
		return -EINVAL;

	return 0;
}