1/* System hash blacklist.
  2 *
  3 * Copyright (C) 2016 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#define pr_fmt(fmt) "blacklist: "fmt
 13#include <linux/module.h>
 14#include <linux/slab.h>
 15#include <linux/key.h>
 16#include <linux/key-type.h>
 17#include <linux/sched.h>
 18#include <linux/ctype.h>
 19#include <linux/err.h>
 20#include <linux/seq_file.h>
 21#include <keys/system_keyring.h>
 22#include "blacklist.h"
 23
 24static struct key *blacklist_keyring;
 25
 26/*
 27 * The description must be a type prefix, a colon and then an even number of
 28 * hex digits.  The hash is kept in the description.
 29 */
 30static int blacklist_vet_description(const char *desc)
 31{
 32	int n = 0;
 33
 34	if (*desc == ':')
 35		return -EINVAL;
 36	for (; *desc; desc++)
 37		if (*desc == ':')
 38			goto found_colon;
 39	return -EINVAL;
 40
 41found_colon:
 42	desc++;
 43	for (; *desc; desc++) {
 44		if (!isxdigit(*desc))
 45			return -EINVAL;
 46		n++;
 47	}
 48
 49	if (n == 0 || n & 1)
 50		return -EINVAL;
 51	return 0;
 52}
 53
 54/*
 55 * The hash to be blacklisted is expected to be in the description.  There will
 56 * be no payload.
 57 */
 58static int blacklist_preparse(struct key_preparsed_payload *prep)
 59{
 60	if (prep->datalen > 0)
 61		return -EINVAL;
 62	return 0;
 63}
 64
 65static void blacklist_free_preparse(struct key_preparsed_payload *prep)
 66{
 67}
 68
 69static void blacklist_describe(const struct key *key, struct seq_file *m)
 70{
 71	seq_puts(m, key->description);
 72}
 73
 74static struct key_type key_type_blacklist = {
 75	.name			= "blacklist",
 76	.vet_description	= blacklist_vet_description,
 77	.preparse		= blacklist_preparse,
 78	.free_preparse		= blacklist_free_preparse,
 79	.instantiate		= generic_key_instantiate,
 80	.describe		= blacklist_describe,
 81};
 82
 83/**
 84 * mark_hash_blacklisted - Add a hash to the system blacklist
 85 * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
 86 */
 87int mark_hash_blacklisted(const char *hash)
 88{
 89	key_ref_t key;
 90
 91	key = key_create_or_update(make_key_ref(blacklist_keyring, true),
 92				   "blacklist",
 93				   hash,
 94				   NULL,
 95				   0,
 96				   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 97				    KEY_USR_VIEW),
 98				   KEY_ALLOC_NOT_IN_QUOTA |
 99				   KEY_ALLOC_BUILT_IN);
100	if (IS_ERR(key)) {
101		pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
102		return PTR_ERR(key);
103	}
104	return 0;
105}
106
107/**
108 * is_hash_blacklisted - Determine if a hash is blacklisted
109 * @hash: The hash to be checked as a binary blob
110 * @hash_len: The length of the binary hash
111 * @type: Type of hash
112 */
113int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
114{
115	key_ref_t kref;
116	size_t type_len = strlen(type);
117	char *buffer, *p;
118	int ret = 0;
119
120	buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
121	if (!buffer)
122		return -ENOMEM;
123	p = memcpy(buffer, type, type_len);
124	p += type_len;
125	*p++ = ':';
126	bin2hex(p, hash, hash_len);
127	p += hash_len * 2;
128	*p = 0;
129
130	kref = keyring_search(make_key_ref(blacklist_keyring, true),
131			      &key_type_blacklist, buffer);
132	if (!IS_ERR(kref)) {
133		key_ref_put(kref);
134		ret = -EKEYREJECTED;
135	}
136
137	kfree(buffer);
138	return ret;
139}
140EXPORT_SYMBOL_GPL(is_hash_blacklisted);
141
142/*
143 * Initialise the blacklist
144 */
145static int __init blacklist_init(void)
146{
147	const char *const *bl;
148
149	if (register_key_type(&key_type_blacklist) < 0)
150		panic("Can't allocate system blacklist key type\n");
151
152	blacklist_keyring =
153		keyring_alloc(".blacklist",
154			      KUIDT_INIT(0), KGIDT_INIT(0),
155			      current_cred(),
156			      (KEY_POS_ALL & ~KEY_POS_SETATTR) |
157			      KEY_USR_VIEW | KEY_USR_READ |
158			      KEY_USR_SEARCH,
159			      KEY_ALLOC_NOT_IN_QUOTA |
160			      KEY_FLAG_KEEP,
161			      NULL, NULL);
162	if (IS_ERR(blacklist_keyring))
163		panic("Can't allocate system blacklist keyring\n");
164
165	for (bl = blacklist_hashes; *bl; bl++)
166		if (mark_hash_blacklisted(*bl) < 0)
167			pr_err("- blacklisting failed\n");
168	return 0;
169}
170
171/*
172 * Must be initialised before we try and load the keys into the keyring.
173 */
174device_initcall(blacklist_init);