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ab3c3587 DH |
1 | /* Large capacity key type |
2 | * | |
3 | * Copyright (C) 2013 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 | ||
ab3c3587 DH |
12 | #include <linux/init.h> |
13 | #include <linux/seq_file.h> | |
14 | #include <linux/file.h> | |
15 | #include <linux/shmem_fs.h> | |
16 | #include <linux/err.h> | |
13100a72 | 17 | #include <linux/scatterlist.h> |
ab3c3587 DH |
18 | #include <keys/user-type.h> |
19 | #include <keys/big_key-type.h> | |
13100a72 | 20 | #include <crypto/rng.h> |
d56d72c6 | 21 | #include <crypto/skcipher.h> |
ab3c3587 | 22 | |
146aa8b1 DH |
23 | /* |
24 | * Layout of key payload words. | |
25 | */ | |
26 | enum { | |
27 | big_key_data, | |
28 | big_key_path, | |
29 | big_key_path_2nd_part, | |
30 | big_key_len, | |
31 | }; | |
32 | ||
13100a72 KM |
33 | /* |
34 | * Crypto operation with big_key data | |
35 | */ | |
36 | enum big_key_op { | |
37 | BIG_KEY_ENC, | |
38 | BIG_KEY_DEC, | |
39 | }; | |
40 | ||
ab3c3587 DH |
41 | /* |
42 | * If the data is under this limit, there's no point creating a shm file to | |
43 | * hold it as the permanently resident metadata for the shmem fs will be at | |
44 | * least as large as the data. | |
45 | */ | |
46 | #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) | |
47 | ||
13100a72 KM |
48 | /* |
49 | * Key size for big_key data encryption | |
50 | */ | |
51 | #define ENC_KEY_SIZE 16 | |
52 | ||
ab3c3587 DH |
53 | /* |
54 | * big_key defined keys take an arbitrary string as the description and an | |
55 | * arbitrary blob of data as the payload | |
56 | */ | |
57 | struct key_type key_type_big_key = { | |
58 | .name = "big_key", | |
002edaf7 DH |
59 | .preparse = big_key_preparse, |
60 | .free_preparse = big_key_free_preparse, | |
61 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
62 | .revoke = big_key_revoke, |
63 | .destroy = big_key_destroy, | |
64 | .describe = big_key_describe, | |
65 | .read = big_key_read, | |
66 | }; | |
67 | ||
13100a72 KM |
68 | /* |
69 | * Crypto names for big_key data encryption | |
70 | */ | |
71 | static const char big_key_rng_name[] = "stdrng"; | |
72 | static const char big_key_alg_name[] = "ecb(aes)"; | |
73 | ||
74 | /* | |
75 | * Crypto algorithms for big_key data encryption | |
76 | */ | |
77 | static struct crypto_rng *big_key_rng; | |
d56d72c6 | 78 | static struct crypto_skcipher *big_key_skcipher; |
13100a72 KM |
79 | |
80 | /* | |
81 | * Generate random key to encrypt big_key data | |
82 | */ | |
83 | static inline int big_key_gen_enckey(u8 *key) | |
84 | { | |
85 | return crypto_rng_get_bytes(big_key_rng, key, ENC_KEY_SIZE); | |
86 | } | |
87 | ||
88 | /* | |
89 | * Encrypt/decrypt big_key data | |
90 | */ | |
91 | static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) | |
92 | { | |
93 | int ret = -EINVAL; | |
94 | struct scatterlist sgio; | |
d56d72c6 | 95 | SKCIPHER_REQUEST_ON_STACK(req, big_key_skcipher); |
13100a72 | 96 | |
d56d72c6 | 97 | if (crypto_skcipher_setkey(big_key_skcipher, key, ENC_KEY_SIZE)) { |
13100a72 KM |
98 | ret = -EAGAIN; |
99 | goto error; | |
100 | } | |
101 | ||
d56d72c6 HX |
102 | skcipher_request_set_tfm(req, big_key_skcipher); |
103 | skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, | |
104 | NULL, NULL); | |
13100a72 KM |
105 | |
106 | sg_init_one(&sgio, data, datalen); | |
d56d72c6 | 107 | skcipher_request_set_crypt(req, &sgio, &sgio, datalen, NULL); |
13100a72 KM |
108 | |
109 | if (op == BIG_KEY_ENC) | |
d56d72c6 | 110 | ret = crypto_skcipher_encrypt(req); |
13100a72 | 111 | else |
d56d72c6 HX |
112 | ret = crypto_skcipher_decrypt(req); |
113 | ||
114 | skcipher_request_zero(req); | |
13100a72 KM |
115 | |
116 | error: | |
117 | return ret; | |
118 | } | |
119 | ||
ab3c3587 | 120 | /* |
002edaf7 | 121 | * Preparse a big key |
ab3c3587 | 122 | */ |
002edaf7 | 123 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 124 | { |
146aa8b1 | 125 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
ab3c3587 | 126 | struct file *file; |
13100a72 KM |
127 | u8 *enckey; |
128 | u8 *data = NULL; | |
ab3c3587 DH |
129 | ssize_t written; |
130 | size_t datalen = prep->datalen; | |
131 | int ret; | |
132 | ||
133 | ret = -EINVAL; | |
134 | if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) | |
135 | goto error; | |
136 | ||
137 | /* Set an arbitrary quota */ | |
002edaf7 | 138 | prep->quotalen = 16; |
ab3c3587 | 139 | |
146aa8b1 | 140 | prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; |
ab3c3587 DH |
141 | |
142 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
143 | /* Create a shmem file to store the data in. This will permit the data | |
144 | * to be swapped out if needed. | |
145 | * | |
13100a72 | 146 | * File content is stored encrypted with randomly generated key. |
ab3c3587 | 147 | */ |
d56d72c6 | 148 | size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher)); |
13100a72 KM |
149 | |
150 | /* prepare aligned data to encrypt */ | |
151 | data = kmalloc(enclen, GFP_KERNEL); | |
152 | if (!data) | |
153 | return -ENOMEM; | |
154 | ||
155 | memcpy(data, prep->data, datalen); | |
156 | memset(data + datalen, 0x00, enclen - datalen); | |
157 | ||
158 | /* generate random key */ | |
159 | enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL); | |
160 | if (!enckey) { | |
161 | ret = -ENOMEM; | |
162 | goto error; | |
163 | } | |
164 | ||
165 | ret = big_key_gen_enckey(enckey); | |
166 | if (ret) | |
167 | goto err_enckey; | |
168 | ||
169 | /* encrypt aligned data */ | |
170 | ret = big_key_crypt(BIG_KEY_ENC, data, enclen, enckey); | |
171 | if (ret) | |
172 | goto err_enckey; | |
173 | ||
174 | /* save aligned data to file */ | |
175 | file = shmem_kernel_file_setup("", enclen, 0); | |
d2b86970 WY |
176 | if (IS_ERR(file)) { |
177 | ret = PTR_ERR(file); | |
13100a72 | 178 | goto err_enckey; |
d2b86970 | 179 | } |
ab3c3587 | 180 | |
13100a72 KM |
181 | written = kernel_write(file, data, enclen, 0); |
182 | if (written != enclen) { | |
97826c82 | 183 | ret = written; |
ab3c3587 DH |
184 | if (written >= 0) |
185 | ret = -ENOMEM; | |
186 | goto err_fput; | |
187 | } | |
188 | ||
189 | /* Pin the mount and dentry to the key so that we can open it again | |
190 | * later | |
191 | */ | |
13100a72 | 192 | prep->payload.data[big_key_data] = enckey; |
ab3c3587 DH |
193 | *path = file->f_path; |
194 | path_get(path); | |
195 | fput(file); | |
13100a72 | 196 | kfree(data); |
ab3c3587 DH |
197 | } else { |
198 | /* Just store the data in a buffer */ | |
199 | void *data = kmalloc(datalen, GFP_KERNEL); | |
13100a72 | 200 | |
002edaf7 DH |
201 | if (!data) |
202 | return -ENOMEM; | |
ab3c3587 | 203 | |
146aa8b1 DH |
204 | prep->payload.data[big_key_data] = data; |
205 | memcpy(data, prep->data, prep->datalen); | |
ab3c3587 DH |
206 | } |
207 | return 0; | |
208 | ||
209 | err_fput: | |
210 | fput(file); | |
13100a72 KM |
211 | err_enckey: |
212 | kfree(enckey); | |
ab3c3587 | 213 | error: |
13100a72 | 214 | kfree(data); |
ab3c3587 DH |
215 | return ret; |
216 | } | |
217 | ||
002edaf7 DH |
218 | /* |
219 | * Clear preparsement. | |
220 | */ | |
221 | void big_key_free_preparse(struct key_preparsed_payload *prep) | |
222 | { | |
223 | if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 224 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
13100a72 | 225 | |
002edaf7 | 226 | path_put(path); |
002edaf7 | 227 | } |
13100a72 | 228 | kfree(prep->payload.data[big_key_data]); |
002edaf7 DH |
229 | } |
230 | ||
ab3c3587 DH |
231 | /* |
232 | * dispose of the links from a revoked keyring | |
233 | * - called with the key sem write-locked | |
234 | */ | |
235 | void big_key_revoke(struct key *key) | |
236 | { | |
146aa8b1 | 237 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
238 | |
239 | /* clear the quota */ | |
240 | key_payload_reserve(key, 0); | |
146aa8b1 DH |
241 | if (key_is_instantiated(key) && |
242 | (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) | |
ab3c3587 DH |
243 | vfs_truncate(path, 0); |
244 | } | |
245 | ||
246 | /* | |
247 | * dispose of the data dangling from the corpse of a big_key key | |
248 | */ | |
249 | void big_key_destroy(struct key *key) | |
250 | { | |
146aa8b1 DH |
251 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
252 | ||
13100a72 | 253 | if (datalen > BIG_KEY_FILE_THRESHOLD) { |
146aa8b1 | 254 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
13100a72 | 255 | |
ab3c3587 DH |
256 | path_put(path); |
257 | path->mnt = NULL; | |
258 | path->dentry = NULL; | |
ab3c3587 | 259 | } |
13100a72 KM |
260 | kfree(key->payload.data[big_key_data]); |
261 | key->payload.data[big_key_data] = NULL; | |
ab3c3587 DH |
262 | } |
263 | ||
264 | /* | |
265 | * describe the big_key key | |
266 | */ | |
267 | void big_key_describe(const struct key *key, struct seq_file *m) | |
268 | { | |
146aa8b1 | 269 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
270 | |
271 | seq_puts(m, key->description); | |
272 | ||
273 | if (key_is_instantiated(key)) | |
146aa8b1 | 274 | seq_printf(m, ": %zu [%s]", |
ab3c3587 DH |
275 | datalen, |
276 | datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
277 | } | |
278 | ||
279 | /* | |
280 | * read the key data | |
281 | * - the key's semaphore is read-locked | |
282 | */ | |
283 | long big_key_read(const struct key *key, char __user *buffer, size_t buflen) | |
284 | { | |
146aa8b1 | 285 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
286 | long ret; |
287 | ||
288 | if (!buffer || buflen < datalen) | |
289 | return datalen; | |
290 | ||
291 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 292 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 | 293 | struct file *file; |
13100a72 KM |
294 | u8 *data; |
295 | u8 *enckey = (u8 *)key->payload.data[big_key_data]; | |
d56d72c6 | 296 | size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher)); |
13100a72 KM |
297 | |
298 | data = kmalloc(enclen, GFP_KERNEL); | |
299 | if (!data) | |
300 | return -ENOMEM; | |
ab3c3587 DH |
301 | |
302 | file = dentry_open(path, O_RDONLY, current_cred()); | |
13100a72 KM |
303 | if (IS_ERR(file)) { |
304 | ret = PTR_ERR(file); | |
305 | goto error; | |
306 | } | |
ab3c3587 | 307 | |
13100a72 KM |
308 | /* read file to kernel and decrypt */ |
309 | ret = kernel_read(file, 0, data, enclen); | |
310 | if (ret >= 0 && ret != enclen) { | |
ab3c3587 | 311 | ret = -EIO; |
13100a72 KM |
312 | goto err_fput; |
313 | } | |
314 | ||
315 | ret = big_key_crypt(BIG_KEY_DEC, data, enclen, enckey); | |
316 | if (ret) | |
317 | goto err_fput; | |
318 | ||
319 | ret = datalen; | |
320 | ||
321 | /* copy decrypted data to user */ | |
322 | if (copy_to_user(buffer, data, datalen) != 0) | |
323 | ret = -EFAULT; | |
324 | ||
325 | err_fput: | |
326 | fput(file); | |
327 | error: | |
328 | kfree(data); | |
ab3c3587 DH |
329 | } else { |
330 | ret = datalen; | |
146aa8b1 DH |
331 | if (copy_to_user(buffer, key->payload.data[big_key_data], |
332 | datalen) != 0) | |
ab3c3587 DH |
333 | ret = -EFAULT; |
334 | } | |
335 | ||
336 | return ret; | |
337 | } | |
338 | ||
13100a72 KM |
339 | /* |
340 | * Register key type | |
341 | */ | |
ab3c3587 DH |
342 | static int __init big_key_init(void) |
343 | { | |
344 | return register_key_type(&key_type_big_key); | |
345 | } | |
13100a72 KM |
346 | |
347 | /* | |
348 | * Initialize big_key crypto and RNG algorithms | |
349 | */ | |
350 | static int __init big_key_crypto_init(void) | |
351 | { | |
352 | int ret = -EINVAL; | |
353 | ||
354 | /* init RNG */ | |
355 | big_key_rng = crypto_alloc_rng(big_key_rng_name, 0, 0); | |
356 | if (IS_ERR(big_key_rng)) { | |
357 | big_key_rng = NULL; | |
358 | return -EFAULT; | |
359 | } | |
360 | ||
361 | /* seed RNG */ | |
362 | ret = crypto_rng_reset(big_key_rng, NULL, crypto_rng_seedsize(big_key_rng)); | |
363 | if (ret) | |
364 | goto error; | |
365 | ||
366 | /* init block cipher */ | |
d56d72c6 HX |
367 | big_key_skcipher = crypto_alloc_skcipher(big_key_alg_name, |
368 | 0, CRYPTO_ALG_ASYNC); | |
369 | if (IS_ERR(big_key_skcipher)) { | |
370 | big_key_skcipher = NULL; | |
13100a72 KM |
371 | ret = -EFAULT; |
372 | goto error; | |
373 | } | |
374 | ||
375 | return 0; | |
376 | ||
377 | error: | |
378 | crypto_free_rng(big_key_rng); | |
379 | big_key_rng = NULL; | |
380 | return ret; | |
381 | } | |
382 | ||
a1f2bdf3 | 383 | device_initcall(big_key_init); |
13100a72 | 384 | late_initcall(big_key_crypto_init); |