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
20 static 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 */
blacklist_vet_description(const char * desc)26 static 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
37 found_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 */
blacklist_preparse(struct key_preparsed_payload * prep)54 static int blacklist_preparse(struct key_preparsed_payload *prep)
55 {
56 if (prep->datalen > 0)
57 return -EINVAL;
58 return 0;
59 }
60
blacklist_free_preparse(struct key_preparsed_payload * prep)61 static void blacklist_free_preparse(struct key_preparsed_payload *prep)
62 {
63 }
64
blacklist_describe(const struct key * key,struct seq_file * m)65 static void blacklist_describe(const struct key *key, struct seq_file *m)
66 {
67 seq_puts(m, key->description);
68 }
69
70 static 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 */
mark_hash_blacklisted(const char * hash)83 int 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 */
is_hash_blacklisted(const u8 * hash,size_t hash_len,const char * type)109 int 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 }
136 EXPORT_SYMBOL_GPL(is_hash_blacklisted);
137
is_binary_blacklisted(const u8 * hash,size_t hash_len)138 int is_binary_blacklisted(const u8 *hash, size_t hash_len)
139 {
140 if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
141 return -EPERM;
142
143 return 0;
144 }
145 EXPORT_SYMBOL_GPL(is_binary_blacklisted);
146
147 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
148 /**
149 * add_key_to_revocation_list - Add a revocation certificate to the blacklist
150 * @data: The data blob containing the certificate
151 * @size: The size of data blob
152 */
add_key_to_revocation_list(const char * data,size_t size)153 int add_key_to_revocation_list(const char *data, size_t size)
154 {
155 key_ref_t key;
156
157 key = key_create_or_update(make_key_ref(blacklist_keyring, true),
158 "asymmetric",
159 NULL,
160 data,
161 size,
162 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW),
163 KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN);
164
165 if (IS_ERR(key)) {
166 pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));
167 return PTR_ERR(key);
168 }
169
170 return 0;
171 }
172
173 /**
174 * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
175 * @pkcs7: The PKCS#7 message to check
176 */
is_key_on_revocation_list(struct pkcs7_message * pkcs7)177 int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
178 {
179 int ret;
180
181 ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
182
183 if (ret == 0)
184 return -EKEYREJECTED;
185
186 return -ENOKEY;
187 }
188 #endif
189
190 /*
191 * Initialise the blacklist
192 */
blacklist_init(void)193 static int __init blacklist_init(void)
194 {
195 const char *const *bl;
196
197 if (register_key_type(&key_type_blacklist) < 0)
198 panic("Can't allocate system blacklist key type\n");
199
200 blacklist_keyring =
201 keyring_alloc(".blacklist",
202 KUIDT_INIT(0), KGIDT_INIT(0),
203 current_cred(),
204 (KEY_POS_ALL & ~KEY_POS_SETATTR) |
205 KEY_USR_VIEW | KEY_USR_READ |
206 KEY_USR_SEARCH,
207 KEY_ALLOC_NOT_IN_QUOTA |
208 KEY_ALLOC_SET_KEEP,
209 NULL, NULL);
210 if (IS_ERR(blacklist_keyring))
211 panic("Can't allocate system blacklist keyring\n");
212
213 for (bl = blacklist_hashes; *bl; bl++)
214 if (mark_hash_blacklisted(*bl) < 0)
215 pr_err("- blacklisting failed\n");
216 return 0;
217 }
218
219 /*
220 * Must be initialised before we try and load the keys into the keyring.
221 */
222 device_initcall(blacklist_init);
223