1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* System hash blacklist.
  3 *
  4 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7
  8#define pr_fmt(fmt) "blacklist: "fmt
  9#include <linux/module.h>
 10#include <linux/slab.h>
 11#include <linux/key.h>
 12#include <linux/key-type.h>
 13#include <linux/sched.h>
 14#include <linux/ctype.h>
 15#include <linux/err.h>
 16#include <linux/seq_file.h>
 17#include <keys/system_keyring.h>
 18#include "blacklist.h"
 19
 20static struct key *blacklist_keyring;
 21
 22/*
 23 * The description must be a type prefix, a colon and then an even number of
 24 * hex digits.  The hash is kept in the description.
 25 */
 26static int blacklist_vet_description(const char *desc)
 27{
 28	int n = 0;
 29
 30	if (*desc == ':')
 31		return -EINVAL;
 32	for (; *desc; desc++)
 33		if (*desc == ':')
 34			goto found_colon;
 35	return -EINVAL;
 36
 37found_colon:
 38	desc++;
 39	for (; *desc; desc++) {
 40		if (!isxdigit(*desc))
 41			return -EINVAL;
 42		n++;
 43	}
 44
 45	if (n == 0 || n & 1)
 46		return -EINVAL;
 47	return 0;
 48}
 49
 50/*
 51 * The hash to be blacklisted is expected to be in the description.  There will
 52 * be no payload.
 53 */
 54static int blacklist_preparse(struct key_preparsed_payload *prep)
 55{
 56	if (prep->datalen > 0)
 57		return -EINVAL;
 58	return 0;
 59}
 60
 61static void blacklist_free_preparse(struct key_preparsed_payload *prep)
 62{
 63}
 64
 65static void blacklist_describe(const struct key *key, struct seq_file *m)
 66{
 67	seq_puts(m, key->description);
 68}
 69
 70static struct key_type key_type_blacklist = {
 71	.name			= "blacklist",
 72	.vet_description	= blacklist_vet_description,
 73	.preparse		= blacklist_preparse,
 74	.free_preparse		= blacklist_free_preparse,
 75	.instantiate		= generic_key_instantiate,
 76	.describe		= blacklist_describe,
 77};
 78
 79/**
 80 * mark_hash_blacklisted - Add a hash to the system blacklist
 81 * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
 82 */
 83int mark_hash_blacklisted(const char *hash)
 84{
 85	key_ref_t key;
 86
 87	key = key_create_or_update(make_key_ref(blacklist_keyring, true),
 88				   "blacklist",
 89				   hash,
 90				   NULL,
 91				   0,
 92				   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 93				    KEY_USR_VIEW),
 94				   KEY_ALLOC_NOT_IN_QUOTA |
 95				   KEY_ALLOC_BUILT_IN);
 96	if (IS_ERR(key)) {
 97		pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
 98		return PTR_ERR(key);
 99	}
100	return 0;
101}
102
103/**
104 * is_hash_blacklisted - Determine if a hash is blacklisted
105 * @hash: The hash to be checked as a binary blob
106 * @hash_len: The length of the binary hash
107 * @type: Type of hash
108 */
109int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
110{
111	key_ref_t kref;
112	size_t type_len = strlen(type);
113	char *buffer, *p;
114	int ret = 0;
115
116	buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
117	if (!buffer)
118		return -ENOMEM;
119	p = memcpy(buffer, type, type_len);
120	p += type_len;
121	*p++ = ':';
122	bin2hex(p, hash, hash_len);
123	p += hash_len * 2;
124	*p = 0;
125
126	kref = keyring_search(make_key_ref(blacklist_keyring, true),
127			      &key_type_blacklist, buffer, false);
128	if (!IS_ERR(kref)) {
129		key_ref_put(kref);
130		ret = -EKEYREJECTED;
131	}
132
133	kfree(buffer);
134	return ret;
135}
136EXPORT_SYMBOL_GPL(is_hash_blacklisted);
137
138/*
139 * Initialise the blacklist
140 */
141static int __init blacklist_init(void)
142{
143	const char *const *bl;
144
145	if (register_key_type(&key_type_blacklist) < 0)
146		panic("Can't allocate system blacklist key type\n");
147
148	blacklist_keyring =
149		keyring_alloc(".blacklist",
150			      KUIDT_INIT(0), KGIDT_INIT(0),
151			      current_cred(),
152			      (KEY_POS_ALL & ~KEY_POS_SETATTR) |
153			      KEY_USR_VIEW | KEY_USR_READ |
154			      KEY_USR_SEARCH,
155			      KEY_ALLOC_NOT_IN_QUOTA |
156			      KEY_FLAG_KEEP,
157			      NULL, NULL);
158	if (IS_ERR(blacklist_keyring))
159		panic("Can't allocate system blacklist keyring\n");
160
161	for (bl = blacklist_hashes; *bl; bl++)
162		if (mark_hash_blacklisted(*bl) < 0)
163			pr_err("- blacklisting failed\n");
164	return 0;
165}
166
167/*
168 * Must be initialised before we try and load the keys into the keyring.
169 */
170device_initcall(blacklist_init);