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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 | ||
7df3e59c | 12 | #define pr_fmt(fmt) "big_key: "fmt |
ab3c3587 DH |
13 | #include <linux/init.h> |
14 | #include <linux/seq_file.h> | |
15 | #include <linux/file.h> | |
16 | #include <linux/shmem_fs.h> | |
17 | #include <linux/err.h> | |
13100a72 | 18 | #include <linux/scatterlist.h> |
ab3c3587 DH |
19 | #include <keys/user-type.h> |
20 | #include <keys/big_key-type.h> | |
13100a72 | 21 | #include <crypto/rng.h> |
d56d72c6 | 22 | #include <crypto/skcipher.h> |
ab3c3587 | 23 | |
146aa8b1 DH |
24 | /* |
25 | * Layout of key payload words. | |
26 | */ | |
27 | enum { | |
28 | big_key_data, | |
29 | big_key_path, | |
30 | big_key_path_2nd_part, | |
31 | big_key_len, | |
32 | }; | |
33 | ||
13100a72 KM |
34 | /* |
35 | * Crypto operation with big_key data | |
36 | */ | |
37 | enum big_key_op { | |
38 | BIG_KEY_ENC, | |
39 | BIG_KEY_DEC, | |
40 | }; | |
41 | ||
ab3c3587 DH |
42 | /* |
43 | * If the data is under this limit, there's no point creating a shm file to | |
44 | * hold it as the permanently resident metadata for the shmem fs will be at | |
45 | * least as large as the data. | |
46 | */ | |
47 | #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) | |
48 | ||
13100a72 KM |
49 | /* |
50 | * Key size for big_key data encryption | |
51 | */ | |
52 | #define ENC_KEY_SIZE 16 | |
53 | ||
ab3c3587 DH |
54 | /* |
55 | * big_key defined keys take an arbitrary string as the description and an | |
56 | * arbitrary blob of data as the payload | |
57 | */ | |
58 | struct key_type key_type_big_key = { | |
59 | .name = "big_key", | |
002edaf7 DH |
60 | .preparse = big_key_preparse, |
61 | .free_preparse = big_key_free_preparse, | |
62 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
63 | .revoke = big_key_revoke, |
64 | .destroy = big_key_destroy, | |
65 | .describe = big_key_describe, | |
66 | .read = big_key_read, | |
67 | }; | |
68 | ||
13100a72 KM |
69 | /* |
70 | * Crypto names for big_key data encryption | |
71 | */ | |
72 | static const char big_key_rng_name[] = "stdrng"; | |
73 | static const char big_key_alg_name[] = "ecb(aes)"; | |
74 | ||
75 | /* | |
76 | * Crypto algorithms for big_key data encryption | |
77 | */ | |
78 | static struct crypto_rng *big_key_rng; | |
d56d72c6 | 79 | static struct crypto_skcipher *big_key_skcipher; |
13100a72 KM |
80 | |
81 | /* | |
82 | * Generate random key to encrypt big_key data | |
83 | */ | |
84 | static inline int big_key_gen_enckey(u8 *key) | |
85 | { | |
86 | return crypto_rng_get_bytes(big_key_rng, key, ENC_KEY_SIZE); | |
87 | } | |
88 | ||
89 | /* | |
90 | * Encrypt/decrypt big_key data | |
91 | */ | |
92 | static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) | |
93 | { | |
94 | int ret = -EINVAL; | |
95 | struct scatterlist sgio; | |
d56d72c6 | 96 | SKCIPHER_REQUEST_ON_STACK(req, big_key_skcipher); |
13100a72 | 97 | |
d56d72c6 | 98 | if (crypto_skcipher_setkey(big_key_skcipher, key, ENC_KEY_SIZE)) { |
13100a72 KM |
99 | ret = -EAGAIN; |
100 | goto error; | |
101 | } | |
102 | ||
d56d72c6 HX |
103 | skcipher_request_set_tfm(req, big_key_skcipher); |
104 | skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, | |
105 | NULL, NULL); | |
13100a72 KM |
106 | |
107 | sg_init_one(&sgio, data, datalen); | |
d56d72c6 | 108 | skcipher_request_set_crypt(req, &sgio, &sgio, datalen, NULL); |
13100a72 KM |
109 | |
110 | if (op == BIG_KEY_ENC) | |
d56d72c6 | 111 | ret = crypto_skcipher_encrypt(req); |
13100a72 | 112 | else |
d56d72c6 HX |
113 | ret = crypto_skcipher_decrypt(req); |
114 | ||
115 | skcipher_request_zero(req); | |
13100a72 KM |
116 | |
117 | error: | |
118 | return ret; | |
119 | } | |
120 | ||
ab3c3587 | 121 | /* |
002edaf7 | 122 | * Preparse a big key |
ab3c3587 | 123 | */ |
002edaf7 | 124 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 125 | { |
146aa8b1 | 126 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
ab3c3587 | 127 | struct file *file; |
13100a72 KM |
128 | u8 *enckey; |
129 | u8 *data = NULL; | |
ab3c3587 DH |
130 | ssize_t written; |
131 | size_t datalen = prep->datalen; | |
132 | int ret; | |
133 | ||
134 | ret = -EINVAL; | |
135 | if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) | |
136 | goto error; | |
137 | ||
138 | /* Set an arbitrary quota */ | |
002edaf7 | 139 | prep->quotalen = 16; |
ab3c3587 | 140 | |
146aa8b1 | 141 | prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; |
ab3c3587 DH |
142 | |
143 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
144 | /* Create a shmem file to store the data in. This will permit the data | |
145 | * to be swapped out if needed. | |
146 | * | |
13100a72 | 147 | * File content is stored encrypted with randomly generated key. |
ab3c3587 | 148 | */ |
d56d72c6 | 149 | size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher)); |
13100a72 KM |
150 | |
151 | /* prepare aligned data to encrypt */ | |
152 | data = kmalloc(enclen, GFP_KERNEL); | |
153 | if (!data) | |
154 | return -ENOMEM; | |
155 | ||
156 | memcpy(data, prep->data, datalen); | |
157 | memset(data + datalen, 0x00, enclen - datalen); | |
158 | ||
159 | /* generate random key */ | |
160 | enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL); | |
161 | if (!enckey) { | |
162 | ret = -ENOMEM; | |
163 | goto error; | |
164 | } | |
165 | ||
166 | ret = big_key_gen_enckey(enckey); | |
167 | if (ret) | |
168 | goto err_enckey; | |
169 | ||
170 | /* encrypt aligned data */ | |
171 | ret = big_key_crypt(BIG_KEY_ENC, data, enclen, enckey); | |
172 | if (ret) | |
173 | goto err_enckey; | |
174 | ||
175 | /* save aligned data to file */ | |
176 | file = shmem_kernel_file_setup("", enclen, 0); | |
d2b86970 WY |
177 | if (IS_ERR(file)) { |
178 | ret = PTR_ERR(file); | |
13100a72 | 179 | goto err_enckey; |
d2b86970 | 180 | } |
ab3c3587 | 181 | |
13100a72 KM |
182 | written = kernel_write(file, data, enclen, 0); |
183 | if (written != enclen) { | |
97826c82 | 184 | ret = written; |
ab3c3587 DH |
185 | if (written >= 0) |
186 | ret = -ENOMEM; | |
187 | goto err_fput; | |
188 | } | |
189 | ||
190 | /* Pin the mount and dentry to the key so that we can open it again | |
191 | * later | |
192 | */ | |
13100a72 | 193 | prep->payload.data[big_key_data] = enckey; |
ab3c3587 DH |
194 | *path = file->f_path; |
195 | path_get(path); | |
196 | fput(file); | |
13100a72 | 197 | kfree(data); |
ab3c3587 DH |
198 | } else { |
199 | /* Just store the data in a buffer */ | |
200 | void *data = kmalloc(datalen, GFP_KERNEL); | |
13100a72 | 201 | |
002edaf7 DH |
202 | if (!data) |
203 | return -ENOMEM; | |
ab3c3587 | 204 | |
146aa8b1 DH |
205 | prep->payload.data[big_key_data] = data; |
206 | memcpy(data, prep->data, prep->datalen); | |
ab3c3587 DH |
207 | } |
208 | return 0; | |
209 | ||
210 | err_fput: | |
211 | fput(file); | |
13100a72 KM |
212 | err_enckey: |
213 | kfree(enckey); | |
ab3c3587 | 214 | error: |
13100a72 | 215 | kfree(data); |
ab3c3587 DH |
216 | return ret; |
217 | } | |
218 | ||
002edaf7 DH |
219 | /* |
220 | * Clear preparsement. | |
221 | */ | |
222 | void big_key_free_preparse(struct key_preparsed_payload *prep) | |
223 | { | |
224 | if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 225 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
13100a72 | 226 | |
002edaf7 | 227 | path_put(path); |
002edaf7 | 228 | } |
13100a72 | 229 | kfree(prep->payload.data[big_key_data]); |
002edaf7 DH |
230 | } |
231 | ||
ab3c3587 DH |
232 | /* |
233 | * dispose of the links from a revoked keyring | |
234 | * - called with the key sem write-locked | |
235 | */ | |
236 | void big_key_revoke(struct key *key) | |
237 | { | |
146aa8b1 | 238 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
239 | |
240 | /* clear the quota */ | |
241 | key_payload_reserve(key, 0); | |
146aa8b1 DH |
242 | if (key_is_instantiated(key) && |
243 | (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) | |
ab3c3587 DH |
244 | vfs_truncate(path, 0); |
245 | } | |
246 | ||
247 | /* | |
248 | * dispose of the data dangling from the corpse of a big_key key | |
249 | */ | |
250 | void big_key_destroy(struct key *key) | |
251 | { | |
146aa8b1 DH |
252 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
253 | ||
13100a72 | 254 | if (datalen > BIG_KEY_FILE_THRESHOLD) { |
146aa8b1 | 255 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
13100a72 | 256 | |
ab3c3587 DH |
257 | path_put(path); |
258 | path->mnt = NULL; | |
259 | path->dentry = NULL; | |
ab3c3587 | 260 | } |
13100a72 KM |
261 | kfree(key->payload.data[big_key_data]); |
262 | key->payload.data[big_key_data] = NULL; | |
ab3c3587 DH |
263 | } |
264 | ||
265 | /* | |
266 | * describe the big_key key | |
267 | */ | |
268 | void big_key_describe(const struct key *key, struct seq_file *m) | |
269 | { | |
146aa8b1 | 270 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
271 | |
272 | seq_puts(m, key->description); | |
273 | ||
274 | if (key_is_instantiated(key)) | |
146aa8b1 | 275 | seq_printf(m, ": %zu [%s]", |
ab3c3587 DH |
276 | datalen, |
277 | datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
278 | } | |
279 | ||
280 | /* | |
281 | * read the key data | |
282 | * - the key's semaphore is read-locked | |
283 | */ | |
284 | long big_key_read(const struct key *key, char __user *buffer, size_t buflen) | |
285 | { | |
146aa8b1 | 286 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
287 | long ret; |
288 | ||
289 | if (!buffer || buflen < datalen) | |
290 | return datalen; | |
291 | ||
292 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 293 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 | 294 | struct file *file; |
13100a72 KM |
295 | u8 *data; |
296 | u8 *enckey = (u8 *)key->payload.data[big_key_data]; | |
d56d72c6 | 297 | size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher)); |
bdd1d2d3 | 298 | loff_t pos = 0; |
13100a72 KM |
299 | |
300 | data = kmalloc(enclen, GFP_KERNEL); | |
301 | if (!data) | |
302 | return -ENOMEM; | |
ab3c3587 DH |
303 | |
304 | file = dentry_open(path, O_RDONLY, current_cred()); | |
13100a72 KM |
305 | if (IS_ERR(file)) { |
306 | ret = PTR_ERR(file); | |
307 | goto error; | |
308 | } | |
ab3c3587 | 309 | |
13100a72 | 310 | /* read file to kernel and decrypt */ |
bdd1d2d3 | 311 | ret = kernel_read(file, data, enclen, &pos); |
13100a72 | 312 | if (ret >= 0 && ret != enclen) { |
ab3c3587 | 313 | ret = -EIO; |
13100a72 KM |
314 | goto err_fput; |
315 | } | |
316 | ||
317 | ret = big_key_crypt(BIG_KEY_DEC, data, enclen, enckey); | |
318 | if (ret) | |
319 | goto err_fput; | |
320 | ||
321 | ret = datalen; | |
322 | ||
323 | /* copy decrypted data to user */ | |
324 | if (copy_to_user(buffer, data, datalen) != 0) | |
325 | ret = -EFAULT; | |
326 | ||
327 | err_fput: | |
328 | fput(file); | |
329 | error: | |
330 | kfree(data); | |
ab3c3587 DH |
331 | } else { |
332 | ret = datalen; | |
146aa8b1 DH |
333 | if (copy_to_user(buffer, key->payload.data[big_key_data], |
334 | datalen) != 0) | |
ab3c3587 DH |
335 | ret = -EFAULT; |
336 | } | |
337 | ||
338 | return ret; | |
339 | } | |
340 | ||
13100a72 KM |
341 | /* |
342 | * Register key type | |
343 | */ | |
ab3c3587 DH |
344 | static int __init big_key_init(void) |
345 | { | |
7df3e59c DH |
346 | struct crypto_skcipher *cipher; |
347 | struct crypto_rng *rng; | |
348 | int ret; | |
13100a72 | 349 | |
7df3e59c DH |
350 | rng = crypto_alloc_rng(big_key_rng_name, 0, 0); |
351 | if (IS_ERR(rng)) { | |
352 | pr_err("Can't alloc rng: %ld\n", PTR_ERR(rng)); | |
353 | return PTR_ERR(rng); | |
13100a72 KM |
354 | } |
355 | ||
7df3e59c DH |
356 | big_key_rng = rng; |
357 | ||
13100a72 | 358 | /* seed RNG */ |
7df3e59c DH |
359 | ret = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng)); |
360 | if (ret) { | |
361 | pr_err("Can't reset rng: %d\n", ret); | |
362 | goto error_rng; | |
363 | } | |
13100a72 KM |
364 | |
365 | /* init block cipher */ | |
7df3e59c DH |
366 | cipher = crypto_alloc_skcipher(big_key_alg_name, 0, CRYPTO_ALG_ASYNC); |
367 | if (IS_ERR(cipher)) { | |
368 | ret = PTR_ERR(cipher); | |
369 | pr_err("Can't alloc crypto: %d\n", ret); | |
370 | goto error_rng; | |
371 | } | |
372 | ||
373 | big_key_skcipher = cipher; | |
374 | ||
375 | ret = register_key_type(&key_type_big_key); | |
376 | if (ret < 0) { | |
377 | pr_err("Can't register type: %d\n", ret); | |
378 | goto error_cipher; | |
13100a72 KM |
379 | } |
380 | ||
381 | return 0; | |
382 | ||
7df3e59c DH |
383 | error_cipher: |
384 | crypto_free_skcipher(big_key_skcipher); | |
385 | error_rng: | |
13100a72 | 386 | crypto_free_rng(big_key_rng); |
13100a72 KM |
387 | return ret; |
388 | } | |
389 | ||
7df3e59c | 390 | late_initcall(big_key_init); |