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12#include <keys/user-type.h>
13#include <linux/scatterlist.h>
14#include <linux/ratelimit.h>
15#include <crypto/aes.h>
16#include <crypto/sha.h>
17#include "fscrypt_private.h"
18
19static struct crypto_shash *essiv_hash_tfm;
20
21static void derive_crypt_complete(struct crypto_async_request *req, int rc)
22{
23 struct fscrypt_completion_result *ecr = req->data;
24
25 if (rc == -EINPROGRESS)
26 return;
27
28 ecr->res = rc;
29 complete(&ecr->completion);
30}
31
32
33
34
35
36
37
38
39
40static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
41 const struct fscrypt_key *source_key,
42 u8 derived_raw_key[FS_MAX_KEY_SIZE])
43{
44 int res = 0;
45 struct skcipher_request *req = NULL;
46 DECLARE_FS_COMPLETION_RESULT(ecr);
47 struct scatterlist src_sg, dst_sg;
48 struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
49
50 if (IS_ERR(tfm)) {
51 res = PTR_ERR(tfm);
52 tfm = NULL;
53 goto out;
54 }
55 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
56 req = skcipher_request_alloc(tfm, GFP_NOFS);
57 if (!req) {
58 res = -ENOMEM;
59 goto out;
60 }
61 skcipher_request_set_callback(req,
62 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
63 derive_crypt_complete, &ecr);
64 res = crypto_skcipher_setkey(tfm, deriving_key,
65 FS_AES_128_ECB_KEY_SIZE);
66 if (res < 0)
67 goto out;
68
69 sg_init_one(&src_sg, source_key->raw, source_key->size);
70 sg_init_one(&dst_sg, derived_raw_key, source_key->size);
71 skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
72 NULL);
73 res = crypto_skcipher_encrypt(req);
74 if (res == -EINPROGRESS || res == -EBUSY) {
75 wait_for_completion(&ecr.completion);
76 res = ecr.res;
77 }
78out:
79 skcipher_request_free(req);
80 crypto_free_skcipher(tfm);
81 return res;
82}
83
84static int validate_user_key(struct fscrypt_info *crypt_info,
85 struct fscrypt_context *ctx, u8 *raw_key,
86 const char *prefix, int min_keysize)
87{
88 char *description;
89 struct key *keyring_key;
90 struct fscrypt_key *master_key;
91 const struct user_key_payload *ukp;
92 int res;
93
94 description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
95 FS_KEY_DESCRIPTOR_SIZE,
96 ctx->master_key_descriptor);
97 if (!description)
98 return -ENOMEM;
99
100 keyring_key = request_key(&key_type_logon, description, NULL);
101 kfree(description);
102 if (IS_ERR(keyring_key))
103 return PTR_ERR(keyring_key);
104 down_read(&keyring_key->sem);
105
106 if (keyring_key->type != &key_type_logon) {
107 printk_once(KERN_WARNING
108 "%s: key type must be logon\n", __func__);
109 res = -ENOKEY;
110 goto out;
111 }
112 ukp = user_key_payload_locked(keyring_key);
113 if (!ukp) {
114
115 res = -EKEYREVOKED;
116 goto out;
117 }
118 if (ukp->datalen != sizeof(struct fscrypt_key)) {
119 res = -EINVAL;
120 goto out;
121 }
122 master_key = (struct fscrypt_key *)ukp->data;
123 BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
124
125 if (master_key->size < min_keysize || master_key->size > FS_MAX_KEY_SIZE
126 || master_key->size % AES_BLOCK_SIZE != 0) {
127 printk_once(KERN_WARNING
128 "%s: key size incorrect: %d\n",
129 __func__, master_key->size);
130 res = -ENOKEY;
131 goto out;
132 }
133 res = derive_key_aes(ctx->nonce, master_key, raw_key);
134out:
135 up_read(&keyring_key->sem);
136 key_put(keyring_key);
137 return res;
138}
139
140static const struct {
141 const char *cipher_str;
142 int keysize;
143} available_modes[] = {
144 [FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
145 FS_AES_256_XTS_KEY_SIZE },
146 [FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
147 FS_AES_256_CTS_KEY_SIZE },
148 [FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
149 FS_AES_128_CBC_KEY_SIZE },
150 [FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
151 FS_AES_128_CTS_KEY_SIZE },
152};
153
154static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
155 const char **cipher_str_ret, int *keysize_ret)
156{
157 u32 mode;
158
159 if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
160 pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
161 inode->i_ino,
162 ci->ci_data_mode, ci->ci_filename_mode);
163 return -EINVAL;
164 }
165
166 if (S_ISREG(inode->i_mode)) {
167 mode = ci->ci_data_mode;
168 } else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
169 mode = ci->ci_filename_mode;
170 } else {
171 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
172 inode->i_ino, (inode->i_mode & S_IFMT));
173 return -EINVAL;
174 }
175
176 *cipher_str_ret = available_modes[mode].cipher_str;
177 *keysize_ret = available_modes[mode].keysize;
178 return 0;
179}
180
181static void put_crypt_info(struct fscrypt_info *ci)
182{
183 if (!ci)
184 return;
185
186 crypto_free_skcipher(ci->ci_ctfm);
187 crypto_free_cipher(ci->ci_essiv_tfm);
188 kmem_cache_free(fscrypt_info_cachep, ci);
189}
190
191static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
192{
193 struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
194
195
196 if (unlikely(!tfm)) {
197 struct crypto_shash *prev_tfm;
198
199 tfm = crypto_alloc_shash("sha256", 0, 0);
200 if (IS_ERR(tfm)) {
201 pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
202 PTR_ERR(tfm));
203 return PTR_ERR(tfm);
204 }
205 prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
206 if (prev_tfm) {
207 crypto_free_shash(tfm);
208 tfm = prev_tfm;
209 }
210 }
211
212 {
213 SHASH_DESC_ON_STACK(desc, tfm);
214 desc->tfm = tfm;
215 desc->flags = 0;
216
217 return crypto_shash_digest(desc, key, keysize, salt);
218 }
219}
220
221static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
222 int keysize)
223{
224 int err;
225 struct crypto_cipher *essiv_tfm;
226 u8 salt[SHA256_DIGEST_SIZE];
227
228 essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
229 if (IS_ERR(essiv_tfm))
230 return PTR_ERR(essiv_tfm);
231
232 ci->ci_essiv_tfm = essiv_tfm;
233
234 err = derive_essiv_salt(raw_key, keysize, salt);
235 if (err)
236 goto out;
237
238
239
240
241
242
243 err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
244 if (err)
245 goto out;
246
247out:
248 memzero_explicit(salt, sizeof(salt));
249 return err;
250}
251
252void __exit fscrypt_essiv_cleanup(void)
253{
254 crypto_free_shash(essiv_hash_tfm);
255}
256
257int fscrypt_get_encryption_info(struct inode *inode)
258{
259 struct fscrypt_info *crypt_info;
260 struct fscrypt_context ctx;
261 struct crypto_skcipher *ctfm;
262 const char *cipher_str;
263 int keysize;
264 u8 *raw_key = NULL;
265 int res;
266
267 if (inode->i_crypt_info)
268 return 0;
269
270 res = fscrypt_initialize(inode->i_sb->s_cop->flags);
271 if (res)
272 return res;
273
274 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
275 if (res < 0) {
276 if (!fscrypt_dummy_context_enabled(inode) ||
277 inode->i_sb->s_cop->is_encrypted(inode))
278 return res;
279
280 memset(&ctx, 0, sizeof(ctx));
281 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
282 ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
283 ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
284 memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
285 } else if (res != sizeof(ctx)) {
286 return -EINVAL;
287 }
288
289 if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
290 return -EINVAL;
291
292 if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
293 return -EINVAL;
294
295 crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
296 if (!crypt_info)
297 return -ENOMEM;
298
299 crypt_info->ci_flags = ctx.flags;
300 crypt_info->ci_data_mode = ctx.contents_encryption_mode;
301 crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
302 crypt_info->ci_ctfm = NULL;
303 crypt_info->ci_essiv_tfm = NULL;
304 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
305 sizeof(crypt_info->ci_master_key));
306
307 res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
308 if (res)
309 goto out;
310
311
312
313
314
315 res = -ENOMEM;
316 raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
317 if (!raw_key)
318 goto out;
319
320 res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
321 keysize);
322 if (res && inode->i_sb->s_cop->key_prefix) {
323 int res2 = validate_user_key(crypt_info, &ctx, raw_key,
324 inode->i_sb->s_cop->key_prefix,
325 keysize);
326 if (res2) {
327 if (res2 == -ENOKEY)
328 res = -ENOKEY;
329 goto out;
330 }
331 } else if (res) {
332 goto out;
333 }
334 ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
335 if (!ctfm || IS_ERR(ctfm)) {
336 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
337 pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
338 __func__, res, inode->i_ino);
339 goto out;
340 }
341 crypt_info->ci_ctfm = ctfm;
342 crypto_skcipher_clear_flags(ctfm, ~0);
343 crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
344
345
346
347
348 res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
349 if (res)
350 goto out;
351
352 if (S_ISREG(inode->i_mode) &&
353 crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
354 res = init_essiv_generator(crypt_info, raw_key, keysize);
355 if (res) {
356 pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
357 __func__, res, inode->i_ino);
358 goto out;
359 }
360 }
361 if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
362 crypt_info = NULL;
363out:
364 if (res == -ENOKEY)
365 res = 0;
366 put_crypt_info(crypt_info);
367 kzfree(raw_key);
368 return res;
369}
370EXPORT_SYMBOL(fscrypt_get_encryption_info);
371
372void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
373{
374 struct fscrypt_info *prev;
375
376 if (ci == NULL)
377 ci = ACCESS_ONCE(inode->i_crypt_info);
378 if (ci == NULL)
379 return;
380
381 prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
382 if (prev != ci)
383 return;
384
385 put_crypt_info(ci);
386}
387EXPORT_SYMBOL(fscrypt_put_encryption_info);
388
