1/* System trusted keyring for trusted public keys
  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/export.h>
 13#include <linux/kernel.h>
 14#include <linux/sched.h>
 15#include <linux/cred.h>
 16#include <linux/err.h>
 17#include <keys/asymmetric-type.h>
 18#include <keys/system_keyring.h>
 19#include <crypto/pkcs7.h>
 20
 21struct key *system_trusted_keyring;
 22EXPORT_SYMBOL_GPL(system_trusted_keyring);
 23
 24extern __initconst const u8 system_certificate_list[];
 25extern __initconst const unsigned long system_certificate_list_size;
 26
 27/*
 28 * Load the compiled-in keys
 29 */
 30static __init int system_trusted_keyring_init(void)
 31{
 32	pr_notice("Initialise system trusted keyring\n");
 33
 34	system_trusted_keyring =
 35		keyring_alloc(".system_keyring",
 36			      KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 37			      ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 38			      KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 39			      KEY_ALLOC_NOT_IN_QUOTA, NULL);
 40	if (IS_ERR(system_trusted_keyring))
 41		panic("Can't allocate system trusted keyring\n");
 42
 43	set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
 44	return 0;
 45}
 46
 47/*
 48 * Must be initialised before we try and load the keys into the keyring.
 49 */
 50device_initcall(system_trusted_keyring_init);
 51
 52/*
 53 * Load the compiled-in list of X.509 certificates.
 54 */
 55static __init int load_system_certificate_list(void)
 56{
 57	key_ref_t key;
 58	const u8 *p, *end;
 59	size_t plen;
 60
 61	pr_notice("Loading compiled-in X.509 certificates\n");
 62
 63	p = system_certificate_list;
 64	end = p + system_certificate_list_size;
 65	while (p < end) {
 66		/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 67		 * than 256 bytes in size.
 68		 */
 69		if (end - p < 4)
 70			goto dodgy_cert;
 71		if (p[0] != 0x30 &&
 72		    p[1] != 0x82)
 73			goto dodgy_cert;
 74		plen = (p[2] << 8) | p[3];
 75		plen += 4;
 76		if (plen > end - p)
 77			goto dodgy_cert;
 78
 79		key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
 80					   "asymmetric",
 81					   NULL,
 82					   p,
 83					   plen,
 84					   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 85					   KEY_USR_VIEW | KEY_USR_READ),
 86					   KEY_ALLOC_NOT_IN_QUOTA |
 87					   KEY_ALLOC_TRUSTED |
 88					   KEY_ALLOC_BUILT_IN);
 89		if (IS_ERR(key)) {
 90			pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 91			       PTR_ERR(key));
 92		} else {
 93			pr_notice("Loaded X.509 cert '%s'\n",
 94				  key_ref_to_ptr(key)->description);
 95			key_ref_put(key);
 96		}
 97		p += plen;
 98	}
 99
100	return 0;
101
102dodgy_cert:
103	pr_err("Problem parsing in-kernel X.509 certificate list\n");
104	return 0;
105}
106late_initcall(load_system_certificate_list);
107
108#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
109
110/**
111 * Verify a PKCS#7-based signature on system data.
112 * @data: The data to be verified.
113 * @len: Size of @data.
114 * @raw_pkcs7: The PKCS#7 message that is the signature.
115 * @pkcs7_len: The size of @raw_pkcs7.
116 * @usage: The use to which the key is being put.
117 */
118int system_verify_data(const void *data, unsigned long len,
119		       const void *raw_pkcs7, size_t pkcs7_len,
120		       enum key_being_used_for usage)
121{
122	struct pkcs7_message *pkcs7;
123	bool trusted;
124	int ret;
125
126	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
127	if (IS_ERR(pkcs7))
128		return PTR_ERR(pkcs7);
129
130	/* The data should be detached - so we need to supply it. */
131	if (pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
132		pr_err("PKCS#7 signature with non-detached data\n");
133		ret = -EBADMSG;
134		goto error;
135	}
136
137	ret = pkcs7_verify(pkcs7, usage);
138	if (ret < 0)
139		goto error;
140
141	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
142	if (ret < 0)
143		goto error;
144
145	if (!trusted) {
146		pr_err("PKCS#7 signature not signed with a trusted key\n");
147		ret = -ENOKEY;
148	}
149
150error:
151	pkcs7_free_message(pkcs7);
152	pr_devel("<==%s() = %d\n", __func__, ret);
153	return ret;
154}
155EXPORT_SYMBOL_GPL(system_verify_data);
156
157#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */