1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
|
/*
* linux/fs/ext4/crypto_fname.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains functions for filename crypto management in ext4
*
* Written by Uday Savagaonkar, 2014.
*
* This has not yet undergone a rigorous security audit.
*
*/
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <keys/encrypted-type.h>
#include <keys/user-type.h>
#include <linux/crypto.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/key.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>
#include "ext4.h"
#include "ext4_crypto.h"
#include "xattr.h"
/**
* ext4_dir_crypt_complete() -
*/
static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
{
struct ext4_completion_result *ecr = req->data;
if (res == -EINPROGRESS)
return;
ecr->res = res;
complete(&ecr->completion);
}
bool ext4_valid_filenames_enc_mode(uint32_t mode)
{
return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
}
static unsigned max_name_len(struct inode *inode)
{
return S_ISLNK(inode->i_mode) ? inode->i_sb->s_blocksize :
EXT4_NAME_LEN;
}
/**
* ext4_fname_encrypt() -
*
* This function encrypts the input filename, and returns the length of the
* ciphertext. Errors are returned as negative numbers. We trust the caller to
* allocate sufficient memory to oname string.
*/
static int ext4_fname_encrypt(struct inode *inode,
const struct qstr *iname,
struct ext4_str *oname)
{
u32 ciphertext_len;
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
struct crypto_ablkcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[EXT4_CRYPTO_BLOCK_SIZE];
struct scatterlist src_sg, dst_sg;
int padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
char *workbuf, buf[32], *alloc_buf = NULL;
unsigned lim = max_name_len(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
EXT4_CRYPTO_BLOCK_SIZE : iname->len;
ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
ciphertext_len = (ciphertext_len > lim)
? lim : ciphertext_len;
if (ciphertext_len <= sizeof(buf)) {
workbuf = buf;
} else {
alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
if (!alloc_buf)
return -ENOMEM;
workbuf = alloc_buf;
}
/* Allocate request */
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(
KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
kfree(alloc_buf);
return -ENOMEM;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
ext4_dir_crypt_complete, &ecr);
/* Copy the input */
memcpy(workbuf, iname->name, iname->len);
if (iname->len < ciphertext_len)
memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
/* Initialize IV */
memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
/* Create encryption request */
sg_init_one(&src_sg, workbuf, ciphertext_len);
sg_init_one(&dst_sg, oname->name, ciphertext_len);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
res = crypto_ablkcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
wait_for_completion(&ecr.completion);
res = ecr.res;
}
kfree(alloc_buf);
ablkcipher_request_free(req);
if (res < 0) {
printk_ratelimited(
KERN_ERR "%s: Error (error code %d)\n", __func__, res);
}
oname->len = ciphertext_len;
return res;
}
/*
* ext4_fname_decrypt()
* This function decrypts the input filename, and returns
* the length of the plaintext.
* Errors are returned as negative numbers.
* We trust the caller to allocate sufficient memory to oname string.
*/
static int ext4_fname_decrypt(struct inode *inode,
const struct ext4_str *iname,
struct ext4_str *oname)
{
struct ext4_str tmp_in[2], tmp_out[1];
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
struct crypto_ablkcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[EXT4_CRYPTO_BLOCK_SIZE];
unsigned lim = max_name_len(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
tmp_in[0].name = iname->name;
tmp_in[0].len = iname->len;
tmp_out[0].name = oname->name;
/* Allocate request */
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(
KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
return -ENOMEM;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
ext4_dir_crypt_complete, &ecr);
/* Initialize IV */
memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
/* Create encryption request */
sg_init_one(&src_sg, iname->name, iname->len);
sg_init_one(&dst_sg, oname->name, oname->len);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
res = crypto_ablkcipher_decrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
wait_for_completion(&ecr.completion);
res = ecr.res;
}
ablkcipher_request_free(req);
if (res < 0) {
printk_ratelimited(
KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
__func__, res);
return res;
}
oname->len = strnlen(oname->name, iname->len);
return oname->len;
}
static const char *lookup_table =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
/**
* ext4_fname_encode_digest() -
*
* Encodes the input digest using characters from the set [a-zA-Z0-9_+].
* The encoded string is roughly 4/3 times the size of the input string.
*/
static int digest_encode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
char *cp = dst;
while (i < len) {
ac += (((unsigned char) src[i]) << bits);
bits += 8;
do {
*cp++ = lookup_table[ac & 0x3f];
ac >>= 6;
bits -= 6;
} while (bits >= 6);
i++;
}
if (bits)
*cp++ = lookup_table[ac & 0x3f];
return cp - dst;
}
static int digest_decode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
const char *p;
char *cp = dst;
while (i < len) {
p = strchr(lookup_table, src[i]);
if (p == NULL || src[i] == 0)
return -2;
ac += (p - lookup_table) << bits;
bits += 6;
if (bits >= 8) {
*cp++ = ac & 0xff;
ac >>= 8;
bits -= 8;
}
i++;
}
if (ac)
return -1;
return cp - dst;
}
/**
* ext4_fname_crypto_round_up() -
*
* Return: The next multiple of block size
*/
u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
{
return ((size+blksize-1)/blksize)*blksize;
}
unsigned ext4_fname_encrypted_size(struct inode *inode, u32 ilen)
{
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
int padding = 32;
if (ci)
padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
if (ilen < EXT4_CRYPTO_BLOCK_SIZE)
ilen = EXT4_CRYPTO_BLOCK_SIZE;
return ext4_fname_crypto_round_up(ilen, padding);
}
/*
* ext4_fname_crypto_alloc_buffer() -
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
*/
int ext4_fname_crypto_alloc_buffer(struct inode *inode,
u32 ilen, struct ext4_str *crypto_str)
{
unsigned int olen = ext4_fname_encrypted_size(inode, ilen);
crypto_str->len = olen;
if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
/* Allocated buffer can hold one more character to null-terminate the
* string */
crypto_str->name = kmalloc(olen+1, GFP_NOFS);
if (!(crypto_str->name))
return -ENOMEM;
return 0;
}
/**
* ext4_fname_crypto_free_buffer() -
*
* Frees the buffer allocated for crypto operation.
*/
void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
{
if (!crypto_str)
return;
kfree(crypto_str->name);
crypto_str->name = NULL;
}
/**
* ext4_fname_disk_to_usr() - converts a filename from disk space to user space
*/
int _ext4_fname_disk_to_usr(struct inode *inode,
struct dx_hash_info *hinfo,
const struct ext4_str *iname,
struct ext4_str *oname)
{
char buf[24];
int ret;
if (iname->len < 3) {
/*Check for . and .. */
if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
oname->name[0] = '.';
oname->name[iname->len-1] = '.';
oname->len = iname->len;
return oname->len;
}
}
if (iname->len < EXT4_CRYPTO_BLOCK_SIZE) {
EXT4_ERROR_INODE(inode, "encrypted inode too small");
return -EUCLEAN;
}
if (EXT4_I(inode)->i_crypt_info)
return ext4_fname_decrypt(inode, iname, oname);
if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
ret = digest_encode(iname->name, iname->len, oname->name);
oname->len = ret;
return ret;
}
if (hinfo) {
memcpy(buf, &hinfo->hash, 4);
memcpy(buf+4, &hinfo->minor_hash, 4);
} else
memset(buf, 0, 8);
memcpy(buf + 8, iname->name + ((iname->len - 17) & ~15), 16);
oname->name[0] = '_';
ret = digest_encode(buf, 24, oname->name+1);
oname->len = ret + 1;
return ret + 1;
}
int ext4_fname_disk_to_usr(struct inode *inode,
struct dx_hash_info *hinfo,
const struct ext4_dir_entry_2 *de,
struct ext4_str *oname)
{
struct ext4_str iname = {.name = (unsigned char *) de->name,
.len = de->name_len };
return _ext4_fname_disk_to_usr(inode, hinfo, &iname, oname);
}
/**
* ext4_fname_usr_to_disk() - converts a filename from user space to disk space
*/
int ext4_fname_usr_to_disk(struct inode *inode,
const struct qstr *iname,
struct ext4_str *oname)
{
int res;
struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
if (iname->len < 3) {
/*Check for . and .. */
if (iname->name[0] == '.' &&
iname->name[iname->len-1] == '.') {
oname->name[0] = '.';
oname->name[iname->len-1] = '.';
oname->len = iname->len;
return oname->len;
}
}
if (ci) {
res = ext4_fname_encrypt(inode, iname, oname);
return res;
}
/* Without a proper key, a user is not allowed to modify the filenames
* in a directory. Consequently, a user space name cannot be mapped to
* a disk-space name */
return -EACCES;
}
int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
int lookup, struct ext4_filename *fname)
{
struct ext4_crypt_info *ci;
int ret = 0, bigname = 0;
memset(fname, 0, sizeof(struct ext4_filename));
fname->usr_fname = iname;
if (!ext4_encrypted_inode(dir) ||
((iname->name[0] == '.') &&
((iname->len == 1) ||
((iname->name[1] == '.') && (iname->len == 2))))) {
fname->disk_name.name = (unsigned char *) iname->name;
fname->disk_name.len = iname->len;
return 0;
}
ret = ext4_get_encryption_info(dir);
if (ret)
return ret;
ci = EXT4_I(dir)->i_crypt_info;
if (ci) {
ret = ext4_fname_crypto_alloc_buffer(dir, iname->len,
&fname->crypto_buf);
if (ret < 0)
return ret;
ret = ext4_fname_encrypt(dir, iname, &fname->crypto_buf);
if (ret < 0)
goto errout;
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
return 0;
}
if (!lookup)
return -EACCES;
/* We don't have the key and we are doing a lookup; decode the
* user-supplied name
*/
if (iname->name[0] == '_')
bigname = 1;
if ((bigname && (iname->len != 33)) ||
(!bigname && (iname->len > 43)))
return -ENOENT;
fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
ret = digest_decode(iname->name + bigname, iname->len - bigname,
fname->crypto_buf.name);
if (ret < 0) {
ret = -ENOENT;
goto errout;
}
fname->crypto_buf.len = ret;
if (bigname) {
memcpy(&fname->hinfo.hash, fname->crypto_buf.name, 4);
memcpy(&fname->hinfo.minor_hash, fname->crypto_buf.name + 4, 4);
} else {
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
}
return 0;
errout:
kfree(fname->crypto_buf.name);
fname->crypto_buf.name = NULL;
return ret;
}
void ext4_fname_free_filename(struct ext4_filename *fname)
{
kfree(fname->crypto_buf.name);
fname->crypto_buf.name = NULL;
fname->usr_fname = NULL;
fname->disk_name.name = NULL;
}
|