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);
175