fscrypt: avoid collisions when presenting long encrypted filenames
[linux-block.git] / fs / crypto / fname.c
CommitLineData
6b3bd08f 1/*
0b81d077 2 * This contains functions for filename crypto management
6b3bd08f
JK
3 *
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
6 *
6b3bd08f 7 * Written by Uday Savagaonkar, 2014.
0b81d077 8 * Modified by Jaegeuk Kim, 2015.
6b3bd08f
JK
9 *
10 * This has not yet undergone a rigorous security audit.
11 */
0b81d077 12
6b3bd08f 13#include <linux/scatterlist.h>
6b3bd08f 14#include <linux/ratelimit.h>
3325bea5 15#include "fscrypt_private.h"
6b3bd08f 16
6b3bd08f 17/**
53fd7550
EB
18 * fname_crypt_complete() - completion callback for filename crypto
19 * @req: The asynchronous cipher request context
20 * @res: The result of the cipher operation
6b3bd08f 21 */
53fd7550 22static void fname_crypt_complete(struct crypto_async_request *req, int res)
6b3bd08f 23{
0b81d077 24 struct fscrypt_completion_result *ecr = req->data;
6b3bd08f
JK
25
26 if (res == -EINPROGRESS)
27 return;
28 ecr->res = res;
29 complete(&ecr->completion);
30}
31
6b3bd08f 32/**
ef1eb3aa 33 * fname_encrypt() - encrypt a filename
6b3bd08f 34 *
ef1eb3aa
EB
35 * The caller must have allocated sufficient memory for the @oname string.
36 *
37 * Return: 0 on success, -errno on failure
6b3bd08f 38 */
0b81d077
JK
39static int fname_encrypt(struct inode *inode,
40 const struct qstr *iname, struct fscrypt_str *oname)
6b3bd08f 41{
2731a944 42 struct skcipher_request *req = NULL;
0b81d077
JK
43 DECLARE_FS_COMPLETION_RESULT(ecr);
44 struct fscrypt_info *ci = inode->i_crypt_info;
2731a944 45 struct crypto_skcipher *tfm = ci->ci_ctfm;
6b3bd08f 46 int res = 0;
0b81d077 47 char iv[FS_CRYPTO_BLOCK_SIZE];
08ae877f 48 struct scatterlist sg;
0b81d077 49 int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
08ae877f
EB
50 unsigned int lim;
51 unsigned int cryptlen;
6b3bd08f 52
0b81d077 53 lim = inode->i_sb->s_cop->max_namelen(inode);
6b3bd08f
JK
54 if (iname->len <= 0 || iname->len > lim)
55 return -EIO;
56
08ae877f
EB
57 /*
58 * Copy the filename to the output buffer for encrypting in-place and
59 * pad it with the needed number of NUL bytes.
60 */
61 cryptlen = max_t(unsigned int, iname->len, FS_CRYPTO_BLOCK_SIZE);
62 cryptlen = round_up(cryptlen, padding);
63 cryptlen = min(cryptlen, lim);
64 memcpy(oname->name, iname->name, iname->len);
65 memset(oname->name + iname->len, 0, cryptlen - iname->len);
6b3bd08f 66
08ae877f
EB
67 /* Initialize the IV */
68 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
6b3bd08f 69
08ae877f 70 /* Set up the encryption request */
2731a944 71 req = skcipher_request_alloc(tfm, GFP_NOFS);
6b3bd08f
JK
72 if (!req) {
73 printk_ratelimited(KERN_ERR
08ae877f 74 "%s: skcipher_request_alloc() failed\n", __func__);
6b3bd08f
JK
75 return -ENOMEM;
76 }
2731a944 77 skcipher_request_set_callback(req,
6b3bd08f 78 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
53fd7550 79 fname_crypt_complete, &ecr);
08ae877f
EB
80 sg_init_one(&sg, oname->name, cryptlen);
81 skcipher_request_set_crypt(req, &sg, &sg, cryptlen, iv);
6b3bd08f 82
08ae877f 83 /* Do the encryption */
2731a944 84 res = crypto_skcipher_encrypt(req);
6b3bd08f 85 if (res == -EINPROGRESS || res == -EBUSY) {
08ae877f 86 /* Request is being completed asynchronously; wait for it */
6b3bd08f
JK
87 wait_for_completion(&ecr.completion);
88 res = ecr.res;
89 }
2731a944 90 skcipher_request_free(req);
ef1eb3aa 91 if (res < 0) {
6b3bd08f
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92 printk_ratelimited(KERN_ERR
93 "%s: Error (error code %d)\n", __func__, res);
ef1eb3aa
EB
94 return res;
95 }
0b81d077 96
08ae877f 97 oname->len = cryptlen;
ef1eb3aa 98 return 0;
6b3bd08f
JK
99}
100
ef1eb3aa
EB
101/**
102 * fname_decrypt() - decrypt a filename
103 *
104 * The caller must have allocated sufficient memory for the @oname string.
105 *
106 * Return: 0 on success, -errno on failure
6b3bd08f 107 */
0b81d077
JK
108static int fname_decrypt(struct inode *inode,
109 const struct fscrypt_str *iname,
110 struct fscrypt_str *oname)
6b3bd08f 111{
2731a944 112 struct skcipher_request *req = NULL;
0b81d077 113 DECLARE_FS_COMPLETION_RESULT(ecr);
6b3bd08f 114 struct scatterlist src_sg, dst_sg;
0b81d077 115 struct fscrypt_info *ci = inode->i_crypt_info;
2731a944 116 struct crypto_skcipher *tfm = ci->ci_ctfm;
6b3bd08f 117 int res = 0;
0b81d077
JK
118 char iv[FS_CRYPTO_BLOCK_SIZE];
119 unsigned lim;
6b3bd08f 120
0b81d077 121 lim = inode->i_sb->s_cop->max_namelen(inode);
6b3bd08f
JK
122 if (iname->len <= 0 || iname->len > lim)
123 return -EIO;
124
125 /* Allocate request */
2731a944 126 req = skcipher_request_alloc(tfm, GFP_NOFS);
6b3bd08f
JK
127 if (!req) {
128 printk_ratelimited(KERN_ERR
129 "%s: crypto_request_alloc() failed\n", __func__);
130 return -ENOMEM;
131 }
2731a944 132 skcipher_request_set_callback(req,
6b3bd08f 133 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
53fd7550 134 fname_crypt_complete, &ecr);
6b3bd08f
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135
136 /* Initialize IV */
0b81d077 137 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
6b3bd08f
JK
138
139 /* Create decryption request */
140 sg_init_one(&src_sg, iname->name, iname->len);
141 sg_init_one(&dst_sg, oname->name, oname->len);
2731a944
HX
142 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
143 res = crypto_skcipher_decrypt(req);
6b3bd08f 144 if (res == -EINPROGRESS || res == -EBUSY) {
6b3bd08f
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145 wait_for_completion(&ecr.completion);
146 res = ecr.res;
147 }
2731a944 148 skcipher_request_free(req);
6b3bd08f
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149 if (res < 0) {
150 printk_ratelimited(KERN_ERR
0b81d077 151 "%s: Error (error code %d)\n", __func__, res);
6b3bd08f
JK
152 return res;
153 }
154
155 oname->len = strnlen(oname->name, iname->len);
ef1eb3aa 156 return 0;
6b3bd08f
JK
157}
158
159static const char *lookup_table =
160 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
161
162/**
0b81d077 163 * digest_encode() -
6b3bd08f
JK
164 *
165 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
166 * The encoded string is roughly 4/3 times the size of the input string.
167 */
168static int digest_encode(const char *src, int len, char *dst)
169{
170 int i = 0, bits = 0, ac = 0;
171 char *cp = dst;
172
173 while (i < len) {
174 ac += (((unsigned char) src[i]) << bits);
175 bits += 8;
176 do {
177 *cp++ = lookup_table[ac & 0x3f];
178 ac >>= 6;
179 bits -= 6;
180 } while (bits >= 6);
181 i++;
182 }
183 if (bits)
184 *cp++ = lookup_table[ac & 0x3f];
185 return cp - dst;
186}
187
188static int digest_decode(const char *src, int len, char *dst)
189{
190 int i = 0, bits = 0, ac = 0;
191 const char *p;
192 char *cp = dst;
193
194 while (i < len) {
195 p = strchr(lookup_table, src[i]);
196 if (p == NULL || src[i] == 0)
197 return -2;
198 ac += (p - lookup_table) << bits;
199 bits += 6;
200 if (bits >= 8) {
201 *cp++ = ac & 0xff;
202 ac >>= 8;
203 bits -= 8;
204 }
205 i++;
206 }
207 if (ac)
208 return -1;
209 return cp - dst;
210}
211
0b93e1b9 212u32 fscrypt_fname_encrypted_size(const struct inode *inode, u32 ilen)
6b3bd08f 213{
922ec355 214 int padding = 32;
0b81d077 215 struct fscrypt_info *ci = inode->i_crypt_info;
922ec355
CY
216
217 if (ci)
0b81d077 218 padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
55be3145
EB
219 ilen = max(ilen, (u32)FS_CRYPTO_BLOCK_SIZE);
220 return round_up(ilen, padding);
6b3bd08f 221}
0b81d077 222EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
6b3bd08f
JK
223
224/**
0b81d077 225 * fscrypt_fname_crypto_alloc_obuff() -
6b3bd08f
JK
226 *
227 * Allocates an output buffer that is sufficient for the crypto operation
228 * specified by the context and the direction.
229 */
0b93e1b9 230int fscrypt_fname_alloc_buffer(const struct inode *inode,
0b81d077 231 u32 ilen, struct fscrypt_str *crypto_str)
6b3bd08f 232{
0b81d077 233 unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);
6b3bd08f 234
6b3bd08f 235 crypto_str->len = olen;
0b81d077
JK
236 if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
237 olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
238 /*
239 * Allocated buffer can hold one more character to null-terminate the
240 * string
241 */
6b3bd08f
JK
242 crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
243 if (!(crypto_str->name))
244 return -ENOMEM;
245 return 0;
246}
0b81d077 247EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
6b3bd08f
JK
248
249/**
0b81d077 250 * fscrypt_fname_crypto_free_buffer() -
6b3bd08f
JK
251 *
252 * Frees the buffer allocated for crypto operation.
253 */
0b81d077 254void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
6b3bd08f
JK
255{
256 if (!crypto_str)
257 return;
258 kfree(crypto_str->name);
259 crypto_str->name = NULL;
260}
0b81d077 261EXPORT_SYMBOL(fscrypt_fname_free_buffer);
6b3bd08f
JK
262
263/**
0b81d077
JK
264 * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
265 * space
ef1eb3aa
EB
266 *
267 * The caller must have allocated sufficient memory for the @oname string.
268 *
269 * Return: 0 on success, -errno on failure
6b3bd08f 270 */
0b81d077
JK
271int fscrypt_fname_disk_to_usr(struct inode *inode,
272 u32 hash, u32 minor_hash,
273 const struct fscrypt_str *iname,
274 struct fscrypt_str *oname)
6b3bd08f
JK
275{
276 const struct qstr qname = FSTR_TO_QSTR(iname);
277 char buf[24];
6b3bd08f 278
0b81d077 279 if (fscrypt_is_dot_dotdot(&qname)) {
6b3bd08f
JK
280 oname->name[0] = '.';
281 oname->name[iname->len - 1] = '.';
282 oname->len = iname->len;
ef1eb3aa 283 return 0;
6b3bd08f
JK
284 }
285
0b81d077 286 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
1dafa51d 287 return -EUCLEAN;
6b3bd08f 288
0b81d077
JK
289 if (inode->i_crypt_info)
290 return fname_decrypt(inode, iname, oname);
291
292 if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
ef1eb3aa
EB
293 oname->len = digest_encode(iname->name, iname->len,
294 oname->name);
295 return 0;
6b3bd08f
JK
296 }
297 if (hash) {
0b81d077
JK
298 memcpy(buf, &hash, 4);
299 memcpy(buf + 4, &minor_hash, 4);
300 } else {
6b3bd08f 301 memset(buf, 0, 8);
0b81d077 302 }
6b06cdee 303 memcpy(buf + 8, iname->name + ((iname->len - 17) & ~15), 16);
6b3bd08f 304 oname->name[0] = '_';
ef1eb3aa
EB
305 oname->len = 1 + digest_encode(buf, 24, oname->name + 1);
306 return 0;
6b3bd08f 307}
0b81d077 308EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
6b3bd08f
JK
309
310/**
0b81d077
JK
311 * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
312 * space
ef1eb3aa
EB
313 *
314 * The caller must have allocated sufficient memory for the @oname string.
315 *
316 * Return: 0 on success, -errno on failure
6b3bd08f 317 */
0b81d077 318int fscrypt_fname_usr_to_disk(struct inode *inode,
6b3bd08f 319 const struct qstr *iname,
0b81d077 320 struct fscrypt_str *oname)
6b3bd08f 321{
0b81d077 322 if (fscrypt_is_dot_dotdot(iname)) {
6b3bd08f
JK
323 oname->name[0] = '.';
324 oname->name[iname->len - 1] = '.';
325 oname->len = iname->len;
ef1eb3aa 326 return 0;
6b3bd08f 327 }
0b81d077
JK
328 if (inode->i_crypt_info)
329 return fname_encrypt(inode, iname, oname);
330 /*
331 * Without a proper key, a user is not allowed to modify the filenames
6b3bd08f 332 * in a directory. Consequently, a user space name cannot be mapped to
0b81d077
JK
333 * a disk-space name
334 */
54475f53 335 return -ENOKEY;
6b3bd08f 336}
0b81d077 337EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
6b3bd08f 338
0b81d077
JK
339int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
340 int lookup, struct fscrypt_name *fname)
6b3bd08f 341{
6b3bd08f
JK
342 int ret = 0, bigname = 0;
343
0b81d077 344 memset(fname, 0, sizeof(struct fscrypt_name));
6b3bd08f
JK
345 fname->usr_fname = iname;
346
0b81d077
JK
347 if (!dir->i_sb->s_cop->is_encrypted(dir) ||
348 fscrypt_is_dot_dotdot(iname)) {
6b3bd08f
JK
349 fname->disk_name.name = (unsigned char *)iname->name;
350 fname->disk_name.len = iname->len;
7bf4b557 351 return 0;
6b3bd08f 352 }
1b53cf98 353 ret = fscrypt_get_encryption_info(dir);
0b81d077 354 if (ret && ret != -EOPNOTSUPP)
6b3bd08f 355 return ret;
0b81d077
JK
356
357 if (dir->i_crypt_info) {
358 ret = fscrypt_fname_alloc_buffer(dir, iname->len,
359 &fname->crypto_buf);
ef1eb3aa 360 if (ret)
7bf4b557 361 return ret;
0b81d077 362 ret = fname_encrypt(dir, iname, &fname->crypto_buf);
ef1eb3aa 363 if (ret)
e5e0906b 364 goto errout;
6b3bd08f
JK
365 fname->disk_name.name = fname->crypto_buf.name;
366 fname->disk_name.len = fname->crypto_buf.len;
7bf4b557 367 return 0;
6b3bd08f 368 }
e5e0906b 369 if (!lookup)
54475f53 370 return -ENOKEY;
6b3bd08f 371
0b81d077
JK
372 /*
373 * We don't have the key and we are doing a lookup; decode the
6b3bd08f
JK
374 * user-supplied name
375 */
376 if (iname->name[0] == '_')
377 bigname = 1;
0b81d077 378 if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
e5e0906b
JK
379 return -ENOENT;
380
6b3bd08f 381 fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
e5e0906b
JK
382 if (fname->crypto_buf.name == NULL)
383 return -ENOMEM;
0b81d077 384
6b3bd08f
JK
385 ret = digest_decode(iname->name + bigname, iname->len - bigname,
386 fname->crypto_buf.name);
387 if (ret < 0) {
388 ret = -ENOENT;
e5e0906b 389 goto errout;
6b3bd08f
JK
390 }
391 fname->crypto_buf.len = ret;
392 if (bigname) {
393 memcpy(&fname->hash, fname->crypto_buf.name, 4);
0b81d077 394 memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
6b3bd08f
JK
395 } else {
396 fname->disk_name.name = fname->crypto_buf.name;
397 fname->disk_name.len = fname->crypto_buf.len;
398 }
7bf4b557 399 return 0;
0b81d077 400
e5e0906b 401errout:
0b81d077 402 fscrypt_fname_free_buffer(&fname->crypto_buf);
6b3bd08f
JK
403 return ret;
404}
0b81d077 405EXPORT_SYMBOL(fscrypt_setup_filename);
6b3bd08f 406
0b81d077 407void fscrypt_free_filename(struct fscrypt_name *fname)
6b3bd08f
JK
408{
409 kfree(fname->crypto_buf.name);
410 fname->crypto_buf.name = NULL;
411 fname->usr_fname = NULL;
412 fname->disk_name.name = NULL;
413}
0b81d077 414EXPORT_SYMBOL(fscrypt_free_filename);