summaryrefslogtreecommitdiffstats
path: root/certs/system_keyring.c
blob: 4e2fa8ab01d651c8d177a2f33dcdda22a03e805a (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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
/* System trusted keyring for trusted public keys
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>
#include <crypto/pkcs7.h>

static struct key *system_trusted_keyring;

extern __initconst const u8 system_certificate_list[];
extern __initconst const unsigned long system_certificate_list_size;

/**
 * restrict_link_by_builtin_trusted - Restrict keyring addition by system CA
 *
 * Restrict the addition of keys into a keyring based on the key-to-be-added
 * being vouched for by a key in the system keyring.
 */
int restrict_link_by_builtin_trusted(struct key *keyring,
				     const struct key_type *type,
				     unsigned long flags,
				     const union key_payload *payload)
{
	return restrict_link_by_signature(system_trusted_keyring,
					  type, payload);
}

/*
 * Load the compiled-in keys
 */
static __init int system_trusted_keyring_init(void)
{
	pr_notice("Initialise system trusted keyring\n");

	system_trusted_keyring =
		keyring_alloc(".system_keyring",
			      KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
			      ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
			      KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
			      KEY_ALLOC_NOT_IN_QUOTA,
			      restrict_link_by_builtin_trusted, NULL);
	if (IS_ERR(system_trusted_keyring))
		panic("Can't allocate system trusted keyring\n");
	return 0;
}

/*
 * Must be initialised before we try and load the keys into the keyring.
 */
device_initcall(system_trusted_keyring_init);

/*
 * Load the compiled-in list of X.509 certificates.
 */
static __init int load_system_certificate_list(void)
{
	key_ref_t key;
	const u8 *p, *end;
	size_t plen;

	pr_notice("Loading compiled-in X.509 certificates\n");

	p = system_certificate_list;
	end = p + system_certificate_list_size;
	while (p < end) {
		/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
		 * than 256 bytes in size.
		 */
		if (end - p < 4)
			goto dodgy_cert;
		if (p[0] != 0x30 &&
		    p[1] != 0x82)
			goto dodgy_cert;
		plen = (p[2] << 8) | p[3];
		plen += 4;
		if (plen > end - p)
			goto dodgy_cert;

		key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
					   "asymmetric",
					   NULL,
					   p,
					   plen,
					   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
					   KEY_USR_VIEW | KEY_USR_READ),
					   KEY_ALLOC_NOT_IN_QUOTA |
					   KEY_ALLOC_TRUSTED |
					   KEY_ALLOC_BUILT_IN |
					   KEY_ALLOC_BYPASS_RESTRICTION);
		if (IS_ERR(key)) {
			pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
			       PTR_ERR(key));
		} else {
			pr_notice("Loaded X.509 cert '%s'\n",
				  key_ref_to_ptr(key)->description);
			key_ref_put(key);
		}
		p += plen;
	}

	return 0;

dodgy_cert:
	pr_err("Problem parsing in-kernel X.509 certificate list\n");
	return 0;
}
late_initcall(load_system_certificate_list);

#ifdef CONFIG_SYSTEM_DATA_VERIFICATION

/**
 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 * @data: The data to be verified (NULL if expecting internal data).
 * @len: Size of @data.
 * @raw_pkcs7: The PKCS#7 message that is the signature.
 * @pkcs7_len: The size of @raw_pkcs7.
 * @trusted_keys: Trusted keys to use (NULL for system_trusted_keyring).
 * @usage: The use to which the key is being put.
 * @view_content: Callback to gain access to content.
 * @ctx: Context for callback.
 */
int verify_pkcs7_signature(const void *data, size_t len,
			   const void *raw_pkcs7, size_t pkcs7_len,
			   struct key *trusted_keys,
			   enum key_being_used_for usage,
			   int (*view_content)(void *ctx,
					       const void *data, size_t len,
					       size_t asn1hdrlen),
			   void *ctx)
{
	struct pkcs7_message *pkcs7;
	int ret;

	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
	if (IS_ERR(pkcs7))
		return PTR_ERR(pkcs7);

	/* The data should be detached - so we need to supply it. */
	if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
		pr_err("PKCS#7 signature with non-detached data\n");
		ret = -EBADMSG;
		goto error;
	}

	ret = pkcs7_verify(pkcs7, usage);
	if (ret < 0)
		goto error;

	if (!trusted_keys)
		trusted_keys = system_trusted_keyring;
	ret = pkcs7_validate_trust(pkcs7, trusted_keys);
	if (ret < 0) {
		if (ret == -ENOKEY)
			pr_err("PKCS#7 signature not signed with a trusted key\n");
		goto error;
	}

	if (view_content) {
		size_t asn1hdrlen;

		ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
		if (ret < 0) {
			if (ret == -ENODATA)
				pr_devel("PKCS#7 message does not contain data\n");
			goto error;
		}

		ret = view_content(ctx, data, len, asn1hdrlen);
	}

error:
	pkcs7_free_message(pkcs7);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
}
EXPORT_SYMBOL_GPL(verify_pkcs7_signature);

#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */