1 // SPDX-License-Identifier: GPL-2.0-or-later 1
2 /* System hash blacklist.
3 *
4 * Copyright (C) 2016 Red Hat, Inc. All Rights
5 * Written by David Howells (dhowells@redhat.c
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 <linux/uidgid.h>
18 #include <keys/asymmetric-type.h>
19 #include <keys/system_keyring.h>
20 #include "blacklist.h"
21
22 /*
23 * According to crypto/asymmetric_keys/x509_ce
24 * the size of the currently longest supported
25 * which translates into 128 hex characters.
26 */
27 #define MAX_HASH_LEN 128
28
29 #define BLACKLIST_KEY_PERM (KEY_POS_SEARCH | K
30 KEY_USR_SEARCH | K
31
32 static const char tbs_prefix[] = "tbs";
33 static const char bin_prefix[] = "bin";
34
35 static struct key *blacklist_keyring;
36
37 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
38 extern __initconst const u8 revocation_certifi
39 extern __initconst const unsigned long revocat
40 #endif
41
42 /*
43 * The description must be a type prefix, a co
44 * hex digits. The hash is kept in the descri
45 */
46 static int blacklist_vet_description(const cha
47 {
48 int i, prefix_len, tbs_step = 0, bin_s
49
50 /* The following algorithm only works
51 BUILD_BUG_ON(sizeof(tbs_prefix) != siz
52 prefix_len = sizeof(tbs_prefix) - 1;
53 for (i = 0; *desc; desc++, i++) {
54 if (*desc == ':') {
55 if (tbs_step == prefix
56 goto found_col
57 if (bin_step == prefix
58 goto found_col
59 return -EINVAL;
60 }
61 if (i >= prefix_len)
62 return -EINVAL;
63 if (*desc == tbs_prefix[i])
64 tbs_step++;
65 if (*desc == bin_prefix[i])
66 bin_step++;
67 }
68 return -EINVAL;
69
70 found_colon:
71 desc++;
72 for (i = 0; *desc && i < MAX_HASH_LEN;
73 if (!isxdigit(*desc) || isuppe
74 return -EINVAL;
75 }
76 if (*desc)
77 /* The hash is greater than MA
78 return -ENOPKG;
79
80 /* Checks for an even number of hexade
81 if (i == 0 || i & 1)
82 return -EINVAL;
83 return 0;
84 }
85
86 static int blacklist_key_instantiate(struct ke
87 struct key_preparsed_payload *
88 {
89 #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE
90 int err;
91 #endif
92
93 /* Sets safe default permissions for k
94 key->perm = BLACKLIST_KEY_PERM;
95
96 /*
97 * Skips the authentication step for b
98 * signed but still trusted.
99 */
100 if (key->flags & (1 << KEY_FLAG_BUILTI
101 goto out;
102
103 #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE
104 /*
105 * Verifies the description's PKCS#7 s
106 * trusted keyring.
107 */
108 err = verify_pkcs7_signature(key->desc
109 strlen(key->descriptio
110 NULL, VERIFYING_UNSPEC
111 if (err)
112 return err;
113 #else
114 /*
115 * It should not be possible to come h
116 * have KEY_USR_WRITE and the only oth
117 * for builtin hashes.
118 */
119 WARN_ON_ONCE(1);
120 return -EPERM;
121 #endif
122
123 out:
124 return generic_key_instantiate(key, pr
125 }
126
127 static int blacklist_key_update(struct key *ke
128 struct key_preparsed_payload *
129 {
130 return -EPERM;
131 }
132
133 static void blacklist_describe(const struct ke
134 {
135 seq_puts(m, key->description);
136 }
137
138 static struct key_type key_type_blacklist = {
139 .name = "blacklist",
140 .vet_description = blacklist_ve
141 .instantiate = blacklist_ke
142 .update = blacklist_ke
143 .describe = blacklist_de
144 };
145
146 static char *get_raw_hash(const u8 *hash, size
147 enum blacklist_hash_type hash_
148 {
149 size_t type_len;
150 const char *type_prefix;
151 char *buffer, *p;
152
153 switch (hash_type) {
154 case BLACKLIST_HASH_X509_TBS:
155 type_len = sizeof(tbs_prefix)
156 type_prefix = tbs_prefix;
157 break;
158 case BLACKLIST_HASH_BINARY:
159 type_len = sizeof(bin_prefix)
160 type_prefix = bin_prefix;
161 break;
162 default:
163 WARN_ON_ONCE(1);
164 return ERR_PTR(-EINVAL);
165 }
166 buffer = kmalloc(type_len + 1 + hash_l
167 if (!buffer)
168 return ERR_PTR(-ENOMEM);
169 p = memcpy(buffer, type_prefix, type_l
170 p += type_len;
171 *p++ = ':';
172 bin2hex(p, hash, hash_len);
173 p += hash_len * 2;
174 *p = '\0';
175 return buffer;
176 }
177
178 /**
179 * mark_raw_hash_blacklisted - Add a hash to t
180 * @hash: The hash as a hex string with a type
181 */
182 static int mark_raw_hash_blacklisted(const cha
183 {
184 key_ref_t key;
185
186 key = key_create(make_key_ref(blacklis
187 "blacklist",
188 hash,
189 NULL,
190 0,
191 BLACKLIST_KEY_PERM,
192 KEY_ALLOC_NOT_IN_QUOT
193 KEY_ALLOC_BUILT_IN);
194 if (IS_ERR(key)) {
195 if (PTR_ERR(key) == -EEXIST)
196 pr_warn("Duplicate bla
197 else
198 pr_err("Problem blackl
199 return PTR_ERR(key);
200 }
201 return 0;
202 }
203
204 int mark_hash_blacklisted(const u8 *hash, size
205 enum blacklist_hash_type hash_
206 {
207 const char *buffer;
208 int err;
209
210 buffer = get_raw_hash(hash, hash_len,
211 if (IS_ERR(buffer))
212 return PTR_ERR(buffer);
213 err = mark_raw_hash_blacklisted(buffer
214 kfree(buffer);
215 return err;
216 }
217
218 /**
219 * is_hash_blacklisted - Determine if a hash i
220 * @hash: The hash to be checked as a binary b
221 * @hash_len: The length of the binary hash
222 * @hash_type: Type of hash
223 */
224 int is_hash_blacklisted(const u8 *hash, size_t
225 enum blacklist_hash_type hash_
226 {
227 key_ref_t kref;
228 const char *buffer;
229 int ret = 0;
230
231 buffer = get_raw_hash(hash, hash_len,
232 if (IS_ERR(buffer))
233 return PTR_ERR(buffer);
234 kref = keyring_search(make_key_ref(bla
235 &key_type_blackl
236 if (!IS_ERR(kref)) {
237 key_ref_put(kref);
238 ret = -EKEYREJECTED;
239 }
240
241 kfree(buffer);
242 return ret;
243 }
244 EXPORT_SYMBOL_GPL(is_hash_blacklisted);
245
246 int is_binary_blacklisted(const u8 *hash, size
247 {
248 if (is_hash_blacklisted(hash, hash_len
249 -EKEYREJECTED)
250 return -EPERM;
251
252 return 0;
253 }
254 EXPORT_SYMBOL_GPL(is_binary_blacklisted);
255
256 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
257 /**
258 * add_key_to_revocation_list - Add a revocati
259 * @data: The data blob containing the certifi
260 * @size: The size of data blob
261 */
262 int add_key_to_revocation_list(const char *dat
263 {
264 key_ref_t key;
265
266 key = key_create_or_update(make_key_re
267 "asymmetric
268 NULL,
269 data,
270 size,
271 KEY_POS_VIE
272 | KEY_USR_V
273 KEY_ALLOC_N
274 | KEY_ALLOC
275
276 if (IS_ERR(key)) {
277 pr_err("Problem with revocatio
278 return PTR_ERR(key);
279 }
280
281 return 0;
282 }
283
284 /**
285 * is_key_on_revocation_list - Determine if th
286 * @pkcs7: The PKCS#7 message to check
287 */
288 int is_key_on_revocation_list(struct pkcs7_mes
289 {
290 int ret;
291
292 ret = pkcs7_validate_trust(pkcs7, blac
293
294 if (ret == 0)
295 return -EKEYREJECTED;
296
297 return -ENOKEY;
298 }
299 #endif
300
301 static int restrict_link_for_blacklist(struct
302 const struct key_type *type, c
303 struct key *restrict_key)
304 {
305 if (type == &key_type_blacklist)
306 return 0;
307 return -EOPNOTSUPP;
308 }
309
310 /*
311 * Initialise the blacklist
312 *
313 * The blacklist_init() function is registered
314 * device_initcall(). As a result if the blac
315 * any reason the kernel continues to execute.
316 * could be acceptable for some non-critical k
317 * keyring fails to load it defeats the certif
318 * signed modules. If a critical piece of sec
319 * expect to be present fails to initialize, p
320 * thing to do.
321 */
322 static int __init blacklist_init(void)
323 {
324 const char *const *bl;
325 struct key_restriction *restriction;
326
327 if (register_key_type(&key_type_blackl
328 panic("Can't allocate system b
329
330 restriction = kzalloc(sizeof(*restrict
331 if (!restriction)
332 panic("Can't allocate blacklis
333 restriction->check = restrict_link_for
334
335 blacklist_keyring =
336 keyring_alloc(".blacklist",
337 GLOBAL_ROOT_UID,
338 KEY_POS_VIEW | K
339 KEY_POS_WRITE |
340 KEY_USR_VIEW | K
341 #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE
342 | KEY_USR_WRITE
343 #endif
344 , KEY_ALLOC_NOT_
345 KEY_ALLOC_SET_KE
346 restriction, NUL
347 if (IS_ERR(blacklist_keyring))
348 panic("Can't allocate system b
349
350 for (bl = blacklist_hashes; *bl; bl++)
351 if (mark_raw_hash_blacklisted(
352 pr_err("- blacklisting
353 return 0;
354 }
355
356 /*
357 * Must be initialised before we try and load
358 */
359 device_initcall(blacklist_init);
360
361 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
362 /*
363 * Load the compiled-in list of revocation X.5
364 */
365 static __init int load_revocation_certificate_
366 {
367 if (revocation_certificate_list_size)
368 pr_notice("Loading compiled-in
369
370 return x509_load_certificate_list(revo
371 revo
372 blac
373 }
374 late_initcall(load_revocation_certificate_list
375 #endif
376
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