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1/*
2 * This contains functions for filename crypto management
3 *
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
6 *
7 * Written by Uday Savagaonkar, 2014.
8 * Modified by Jaegeuk Kim, 2015.
9 *
10 * This has not yet undergone a rigorous security audit.
11 */
12
13#include <keys/encrypted-type.h>
14#include <keys/user-type.h>
15#include <linux/scatterlist.h>
16#include <linux/ratelimit.h>
17#include <linux/fscrypto.h>
18
19static u32 size_round_up(size_t size, size_t blksize)
20{
21 return ((size + blksize - 1) / blksize) * blksize;
22}
23
24/**
25 * dir_crypt_complete() -
26 */
27static void dir_crypt_complete(struct crypto_async_request *req, int res)
28{
29 struct fscrypt_completion_result *ecr = req->data;
30
31 if (res == -EINPROGRESS)
32 return;
33 ecr->res = res;
34 complete(&ecr->completion);
35}
36
37/**
38 * fname_encrypt() -
39 *
40 * This function encrypts the input filename, and returns the length of the
41 * ciphertext. Errors are returned as negative numbers. We trust the caller to
42 * allocate sufficient memory to oname string.
43 */
44static int fname_encrypt(struct inode *inode,
45 const struct qstr *iname, struct fscrypt_str *oname)
46{
47 u32 ciphertext_len;
48 struct skcipher_request *req = NULL;
49 DECLARE_FS_COMPLETION_RESULT(ecr);
50 struct fscrypt_info *ci = inode->i_crypt_info;
51 struct crypto_skcipher *tfm = ci->ci_ctfm;
52 int res = 0;
53 char iv[FS_CRYPTO_BLOCK_SIZE];
54 struct scatterlist src_sg, dst_sg;
55 int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
56 char *workbuf, buf[32], *alloc_buf = NULL;
57 unsigned lim;
58
59 lim = inode->i_sb->s_cop->max_namelen(inode);
60 if (iname->len <= 0 || iname->len > lim)
61 return -EIO;
62
63 ciphertext_len = (iname->len < FS_CRYPTO_BLOCK_SIZE) ?
64 FS_CRYPTO_BLOCK_SIZE : iname->len;
65 ciphertext_len = size_round_up(ciphertext_len, padding);
66 ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;
67
68 if (ciphertext_len <= sizeof(buf)) {
69 workbuf = buf;
70 } else {
71 alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
72 if (!alloc_buf)
73 return -ENOMEM;
74 workbuf = alloc_buf;
75 }
76
77 /* Allocate request */
78 req = skcipher_request_alloc(tfm, GFP_NOFS);
79 if (!req) {
80 printk_ratelimited(KERN_ERR
81 "%s: crypto_request_alloc() failed\n", __func__);
82 kfree(alloc_buf);
83 return -ENOMEM;
84 }
85 skcipher_request_set_callback(req,
86 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
87 dir_crypt_complete, &ecr);
88
89 /* Copy the input */
90 memcpy(workbuf, iname->name, iname->len);
91 if (iname->len < ciphertext_len)
92 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
93
94 /* Initialize IV */
95 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
96
97 /* Create encryption request */
98 sg_init_one(&src_sg, workbuf, ciphertext_len);
99 sg_init_one(&dst_sg, oname->name, ciphertext_len);
100 skcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
101 res = crypto_skcipher_encrypt(req);
102 if (res == -EINPROGRESS || res == -EBUSY) {
103 wait_for_completion(&ecr.completion);
104 res = ecr.res;
105 }
106 kfree(alloc_buf);
107 skcipher_request_free(req);
108 if (res < 0)
109 printk_ratelimited(KERN_ERR
110 "%s: Error (error code %d)\n", __func__, res);
111
112 oname->len = ciphertext_len;
113 return res;
114}
115
116/*
117 * fname_decrypt()
118 * This function decrypts the input filename, and returns
119 * the length of the plaintext.
120 * Errors are returned as negative numbers.
121 * We trust the caller to allocate sufficient memory to oname string.
122 */
123static int fname_decrypt(struct inode *inode,
124 const struct fscrypt_str *iname,
125 struct fscrypt_str *oname)
126{
127 struct skcipher_request *req = NULL;
128 DECLARE_FS_COMPLETION_RESULT(ecr);
129 struct scatterlist src_sg, dst_sg;
130 struct fscrypt_info *ci = inode->i_crypt_info;
131 struct crypto_skcipher *tfm = ci->ci_ctfm;
132 int res = 0;
133 char iv[FS_CRYPTO_BLOCK_SIZE];
134 unsigned lim;
135
136 lim = inode->i_sb->s_cop->max_namelen(inode);
137 if (iname->len <= 0 || iname->len > lim)
138 return -EIO;
139
140 /* Allocate request */
141 req = skcipher_request_alloc(tfm, GFP_NOFS);
142 if (!req) {
143 printk_ratelimited(KERN_ERR
144 "%s: crypto_request_alloc() failed\n", __func__);
145 return -ENOMEM;
146 }
147 skcipher_request_set_callback(req,
148 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
149 dir_crypt_complete, &ecr);
150
151 /* Initialize IV */
152 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
153
154 /* Create decryption request */
155 sg_init_one(&src_sg, iname->name, iname->len);
156 sg_init_one(&dst_sg, oname->name, oname->len);
157 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
158 res = crypto_skcipher_decrypt(req);
159 if (res == -EINPROGRESS || res == -EBUSY) {
160 wait_for_completion(&ecr.completion);
161 res = ecr.res;
162 }
163 skcipher_request_free(req);
164 if (res < 0) {
165 printk_ratelimited(KERN_ERR
166 "%s: Error (error code %d)\n", __func__, res);
167 return res;
168 }
169
170 oname->len = strnlen(oname->name, iname->len);
171 return oname->len;
172}
173
174static const char *lookup_table =
175 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
176
177/**
178 * digest_encode() -
179 *
180 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
181 * The encoded string is roughly 4/3 times the size of the input string.
182 */
183static int digest_encode(const char *src, int len, char *dst)
184{
185 int i = 0, bits = 0, ac = 0;
186 char *cp = dst;
187
188 while (i < len) {
189 ac += (((unsigned char) src[i]) << bits);
190 bits += 8;
191 do {
192 *cp++ = lookup_table[ac & 0x3f];
193 ac >>= 6;
194 bits -= 6;
195 } while (bits >= 6);
196 i++;
197 }
198 if (bits)
199 *cp++ = lookup_table[ac & 0x3f];
200 return cp - dst;
201}
202
203static int digest_decode(const char *src, int len, char *dst)
204{
205 int i = 0, bits = 0, ac = 0;
206 const char *p;
207 char *cp = dst;
208
209 while (i < len) {
210 p = strchr(lookup_table, src[i]);
211 if (p == NULL || src[i] == 0)
212 return -2;
213 ac += (p - lookup_table) << bits;
214 bits += 6;
215 if (bits >= 8) {
216 *cp++ = ac & 0xff;
217 ac >>= 8;
218 bits -= 8;
219 }
220 i++;
221 }
222 if (ac)
223 return -1;
224 return cp - dst;
225}
226
227u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen)
228{
229 int padding = 32;
230 struct fscrypt_info *ci = inode->i_crypt_info;
231
232 if (ci)
233 padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
234 if (ilen < FS_CRYPTO_BLOCK_SIZE)
235 ilen = FS_CRYPTO_BLOCK_SIZE;
236 return size_round_up(ilen, padding);
237}
238EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
239
240/**
241 * fscrypt_fname_crypto_alloc_obuff() -
242 *
243 * Allocates an output buffer that is sufficient for the crypto operation
244 * specified by the context and the direction.
245 */
246int fscrypt_fname_alloc_buffer(struct inode *inode,
247 u32 ilen, struct fscrypt_str *crypto_str)
248{
249 unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);
250
251 crypto_str->len = olen;
252 if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
253 olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
254 /*
255 * Allocated buffer can hold one more character to null-terminate the
256 * string
257 */
258 crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
259 if (!(crypto_str->name))
260 return -ENOMEM;
261 return 0;
262}
263EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
264
265/**
266 * fscrypt_fname_crypto_free_buffer() -
267 *
268 * Frees the buffer allocated for crypto operation.
269 */
270void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
271{
272 if (!crypto_str)
273 return;
274 kfree(crypto_str->name);
275 crypto_str->name = NULL;
276}
277EXPORT_SYMBOL(fscrypt_fname_free_buffer);
278
279/**
280 * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
281 * space
282 */
283int fscrypt_fname_disk_to_usr(struct inode *inode,
284 u32 hash, u32 minor_hash,
285 const struct fscrypt_str *iname,
286 struct fscrypt_str *oname)
287{
288 const struct qstr qname = FSTR_TO_QSTR(iname);
289 char buf[24];
290 int ret;
291
292 if (fscrypt_is_dot_dotdot(&qname)) {
293 oname->name[0] = '.';
294 oname->name[iname->len - 1] = '.';
295 oname->len = iname->len;
296 return oname->len;
297 }
298
299 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
300 return -EUCLEAN;
301
302 if (inode->i_crypt_info)
303 return fname_decrypt(inode, iname, oname);
304
305 if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
306 ret = digest_encode(iname->name, iname->len, oname->name);
307 oname->len = ret;
308 return ret;
309 }
310 if (hash) {
311 memcpy(buf, &hash, 4);
312 memcpy(buf + 4, &minor_hash, 4);
313 } else {
314 memset(buf, 0, 8);
315 }
316 memcpy(buf + 8, iname->name + iname->len - 16, 16);
317 oname->name[0] = '_';
318 ret = digest_encode(buf, 24, oname->name + 1);
319 oname->len = ret + 1;
320 return ret + 1;
321}
322EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
323
324/**
325 * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
326 * space
327 */
328int fscrypt_fname_usr_to_disk(struct inode *inode,
329 const struct qstr *iname,
330 struct fscrypt_str *oname)
331{
332 if (fscrypt_is_dot_dotdot(iname)) {
333 oname->name[0] = '.';
334 oname->name[iname->len - 1] = '.';
335 oname->len = iname->len;
336 return oname->len;
337 }
338 if (inode->i_crypt_info)
339 return fname_encrypt(inode, iname, oname);
340 /*
341 * Without a proper key, a user is not allowed to modify the filenames
342 * in a directory. Consequently, a user space name cannot be mapped to
343 * a disk-space name
344 */
345 return -EACCES;
346}
347EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
348
349int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
350 int lookup, struct fscrypt_name *fname)
351{
352 int ret = 0, bigname = 0;
353
354 memset(fname, 0, sizeof(struct fscrypt_name));
355 fname->usr_fname = iname;
356
357 if (!dir->i_sb->s_cop->is_encrypted(dir) ||
358 fscrypt_is_dot_dotdot(iname)) {
359 fname->disk_name.name = (unsigned char *)iname->name;
360 fname->disk_name.len = iname->len;
361 return 0;
362 }
363 ret = get_crypt_info(dir);
364 if (ret && ret != -EOPNOTSUPP)
365 return ret;
366
367 if (dir->i_crypt_info) {
368 ret = fscrypt_fname_alloc_buffer(dir, iname->len,
369 &fname->crypto_buf);
370 if (ret < 0)
371 return ret;
372 ret = fname_encrypt(dir, iname, &fname->crypto_buf);
373 if (ret < 0)
374 goto errout;
375 fname->disk_name.name = fname->crypto_buf.name;
376 fname->disk_name.len = fname->crypto_buf.len;
377 return 0;
378 }
379 if (!lookup)
380 return -EACCES;
381
382 /*
383 * We don't have the key and we are doing a lookup; decode the
384 * user-supplied name
385 */
386 if (iname->name[0] == '_')
387 bigname = 1;
388 if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
389 return -ENOENT;
390
391 fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
392 if (fname->crypto_buf.name == NULL)
393 return -ENOMEM;
394
395 ret = digest_decode(iname->name + bigname, iname->len - bigname,
396 fname->crypto_buf.name);
397 if (ret < 0) {
398 ret = -ENOENT;
399 goto errout;
400 }
401 fname->crypto_buf.len = ret;
402 if (bigname) {
403 memcpy(&fname->hash, fname->crypto_buf.name, 4);
404 memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
405 } else {
406 fname->disk_name.name = fname->crypto_buf.name;
407 fname->disk_name.len = fname->crypto_buf.len;
408 }
409 return 0;
410
411errout:
412 fscrypt_fname_free_buffer(&fname->crypto_buf);
413 return ret;
414}
415EXPORT_SYMBOL(fscrypt_setup_filename);
416
417void fscrypt_free_filename(struct fscrypt_name *fname)
418{
419 kfree(fname->crypto_buf.name);
420 fname->crypto_buf.name = NULL;
421 fname->usr_fname = NULL;
422 fname->disk_name.name = NULL;
423}
424EXPORT_SYMBOL(fscrypt_free_filename);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This contains functions for filename crypto management
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
7 *
8 * Written by Uday Savagaonkar, 2014.
9 * Modified by Jaegeuk Kim, 2015.
10 *
11 * This has not yet undergone a rigorous security audit.
12 */
13
14#include <linux/scatterlist.h>
15#include <linux/ratelimit.h>
16#include <crypto/skcipher.h>
17#include "fscrypt_private.h"
18
19static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
20{
21 if (str->len == 1 && str->name[0] == '.')
22 return true;
23
24 if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
25 return true;
26
27 return false;
28}
29
30/**
31 * fname_encrypt() - encrypt a filename
32 *
33 * The output buffer must be at least as large as the input buffer.
34 * Any extra space is filled with NUL padding before encryption.
35 *
36 * Return: 0 on success, -errno on failure
37 */
38int fname_encrypt(struct inode *inode, const struct qstr *iname,
39 u8 *out, unsigned int olen)
40{
41 struct skcipher_request *req = NULL;
42 DECLARE_CRYPTO_WAIT(wait);
43 struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm;
44 int res = 0;
45 char iv[FS_CRYPTO_BLOCK_SIZE];
46 struct scatterlist sg;
47
48 /*
49 * Copy the filename to the output buffer for encrypting in-place and
50 * pad it with the needed number of NUL bytes.
51 */
52 if (WARN_ON(olen < iname->len))
53 return -ENOBUFS;
54 memcpy(out, iname->name, iname->len);
55 memset(out + iname->len, 0, olen - iname->len);
56
57 /* Initialize the IV */
58 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
59
60 /* Set up the encryption request */
61 req = skcipher_request_alloc(tfm, GFP_NOFS);
62 if (!req) {
63 printk_ratelimited(KERN_ERR
64 "%s: skcipher_request_alloc() failed\n", __func__);
65 return -ENOMEM;
66 }
67 skcipher_request_set_callback(req,
68 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
69 crypto_req_done, &wait);
70 sg_init_one(&sg, out, olen);
71 skcipher_request_set_crypt(req, &sg, &sg, olen, iv);
72
73 /* Do the encryption */
74 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
75 skcipher_request_free(req);
76 if (res < 0) {
77 printk_ratelimited(KERN_ERR
78 "%s: Error (error code %d)\n", __func__, res);
79 return res;
80 }
81
82 return 0;
83}
84
85/**
86 * fname_decrypt() - decrypt a filename
87 *
88 * The caller must have allocated sufficient memory for the @oname string.
89 *
90 * Return: 0 on success, -errno on failure
91 */
92static int fname_decrypt(struct inode *inode,
93 const struct fscrypt_str *iname,
94 struct fscrypt_str *oname)
95{
96 struct skcipher_request *req = NULL;
97 DECLARE_CRYPTO_WAIT(wait);
98 struct scatterlist src_sg, dst_sg;
99 struct fscrypt_info *ci = inode->i_crypt_info;
100 struct crypto_skcipher *tfm = ci->ci_ctfm;
101 int res = 0;
102 char iv[FS_CRYPTO_BLOCK_SIZE];
103 unsigned lim;
104
105 lim = inode->i_sb->s_cop->max_namelen(inode);
106 if (iname->len <= 0 || iname->len > lim)
107 return -EIO;
108
109 /* Allocate request */
110 req = skcipher_request_alloc(tfm, GFP_NOFS);
111 if (!req) {
112 printk_ratelimited(KERN_ERR
113 "%s: crypto_request_alloc() failed\n", __func__);
114 return -ENOMEM;
115 }
116 skcipher_request_set_callback(req,
117 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
118 crypto_req_done, &wait);
119
120 /* Initialize IV */
121 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
122
123 /* Create decryption request */
124 sg_init_one(&src_sg, iname->name, iname->len);
125 sg_init_one(&dst_sg, oname->name, oname->len);
126 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
127 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
128 skcipher_request_free(req);
129 if (res < 0) {
130 printk_ratelimited(KERN_ERR
131 "%s: Error (error code %d)\n", __func__, res);
132 return res;
133 }
134
135 oname->len = strnlen(oname->name, iname->len);
136 return 0;
137}
138
139static const char *lookup_table =
140 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
141
142#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
143
144/**
145 * digest_encode() -
146 *
147 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
148 * The encoded string is roughly 4/3 times the size of the input string.
149 */
150static int digest_encode(const char *src, int len, char *dst)
151{
152 int i = 0, bits = 0, ac = 0;
153 char *cp = dst;
154
155 while (i < len) {
156 ac += (((unsigned char) src[i]) << bits);
157 bits += 8;
158 do {
159 *cp++ = lookup_table[ac & 0x3f];
160 ac >>= 6;
161 bits -= 6;
162 } while (bits >= 6);
163 i++;
164 }
165 if (bits)
166 *cp++ = lookup_table[ac & 0x3f];
167 return cp - dst;
168}
169
170static int digest_decode(const char *src, int len, char *dst)
171{
172 int i = 0, bits = 0, ac = 0;
173 const char *p;
174 char *cp = dst;
175
176 while (i < len) {
177 p = strchr(lookup_table, src[i]);
178 if (p == NULL || src[i] == 0)
179 return -2;
180 ac += (p - lookup_table) << bits;
181 bits += 6;
182 if (bits >= 8) {
183 *cp++ = ac & 0xff;
184 ac >>= 8;
185 bits -= 8;
186 }
187 i++;
188 }
189 if (ac)
190 return -1;
191 return cp - dst;
192}
193
194bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
195 u32 max_len, u32 *encrypted_len_ret)
196{
197 int padding = 4 << (inode->i_crypt_info->ci_flags &
198 FS_POLICY_FLAGS_PAD_MASK);
199 u32 encrypted_len;
200
201 if (orig_len > max_len)
202 return false;
203 encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
204 encrypted_len = round_up(encrypted_len, padding);
205 *encrypted_len_ret = min(encrypted_len, max_len);
206 return true;
207}
208
209/**
210 * fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames
211 *
212 * Allocate a buffer that is large enough to hold any decrypted or encoded
213 * filename (null-terminated), for the given maximum encrypted filename length.
214 *
215 * Return: 0 on success, -errno on failure
216 */
217int fscrypt_fname_alloc_buffer(const struct inode *inode,
218 u32 max_encrypted_len,
219 struct fscrypt_str *crypto_str)
220{
221 const u32 max_encoded_len =
222 max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
223 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
224 u32 max_presented_len;
225
226 max_presented_len = max(max_encoded_len, max_encrypted_len);
227
228 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
229 if (!crypto_str->name)
230 return -ENOMEM;
231 crypto_str->len = max_presented_len;
232 return 0;
233}
234EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
235
236/**
237 * fscrypt_fname_free_buffer - free the buffer for presented filenames
238 *
239 * Free the buffer allocated by fscrypt_fname_alloc_buffer().
240 */
241void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
242{
243 if (!crypto_str)
244 return;
245 kfree(crypto_str->name);
246 crypto_str->name = NULL;
247}
248EXPORT_SYMBOL(fscrypt_fname_free_buffer);
249
250/**
251 * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
252 * space
253 *
254 * The caller must have allocated sufficient memory for the @oname string.
255 *
256 * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
257 * it for presentation. Short names are directly base64-encoded, while long
258 * names are encoded in fscrypt_digested_name format.
259 *
260 * Return: 0 on success, -errno on failure
261 */
262int fscrypt_fname_disk_to_usr(struct inode *inode,
263 u32 hash, u32 minor_hash,
264 const struct fscrypt_str *iname,
265 struct fscrypt_str *oname)
266{
267 const struct qstr qname = FSTR_TO_QSTR(iname);
268 struct fscrypt_digested_name digested_name;
269
270 if (fscrypt_is_dot_dotdot(&qname)) {
271 oname->name[0] = '.';
272 oname->name[iname->len - 1] = '.';
273 oname->len = iname->len;
274 return 0;
275 }
276
277 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
278 return -EUCLEAN;
279
280 if (inode->i_crypt_info)
281 return fname_decrypt(inode, iname, oname);
282
283 if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
284 oname->len = digest_encode(iname->name, iname->len,
285 oname->name);
286 return 0;
287 }
288 if (hash) {
289 digested_name.hash = hash;
290 digested_name.minor_hash = minor_hash;
291 } else {
292 digested_name.hash = 0;
293 digested_name.minor_hash = 0;
294 }
295 memcpy(digested_name.digest,
296 FSCRYPT_FNAME_DIGEST(iname->name, iname->len),
297 FSCRYPT_FNAME_DIGEST_SIZE);
298 oname->name[0] = '_';
299 oname->len = 1 + digest_encode((const char *)&digested_name,
300 sizeof(digested_name), oname->name + 1);
301 return 0;
302}
303EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
304
305/**
306 * fscrypt_setup_filename() - prepare to search a possibly encrypted directory
307 * @dir: the directory that will be searched
308 * @iname: the user-provided filename being searched for
309 * @lookup: 1 if we're allowed to proceed without the key because it's
310 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
311 * proceed without the key because we're going to create the dir_entry.
312 * @fname: the filename information to be filled in
313 *
314 * Given a user-provided filename @iname, this function sets @fname->disk_name
315 * to the name that would be stored in the on-disk directory entry, if possible.
316 * If the directory is unencrypted this is simply @iname. Else, if we have the
317 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
318 * get the disk_name.
319 *
320 * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
321 * we decode it to get either the ciphertext disk_name (for short names) or the
322 * fscrypt_digested_name (for long names). Non-@lookup operations will be
323 * impossible in this case, so we fail them with ENOKEY.
324 *
325 * If successful, fscrypt_free_filename() must be called later to clean up.
326 *
327 * Return: 0 on success, -errno on failure
328 */
329int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
330 int lookup, struct fscrypt_name *fname)
331{
332 int ret;
333 int digested;
334
335 memset(fname, 0, sizeof(struct fscrypt_name));
336 fname->usr_fname = iname;
337
338 if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
339 fname->disk_name.name = (unsigned char *)iname->name;
340 fname->disk_name.len = iname->len;
341 return 0;
342 }
343 ret = fscrypt_get_encryption_info(dir);
344 if (ret && ret != -EOPNOTSUPP)
345 return ret;
346
347 if (dir->i_crypt_info) {
348 if (!fscrypt_fname_encrypted_size(dir, iname->len,
349 dir->i_sb->s_cop->max_namelen(dir),
350 &fname->crypto_buf.len))
351 return -ENAMETOOLONG;
352 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
353 GFP_NOFS);
354 if (!fname->crypto_buf.name)
355 return -ENOMEM;
356
357 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
358 fname->crypto_buf.len);
359 if (ret)
360 goto errout;
361 fname->disk_name.name = fname->crypto_buf.name;
362 fname->disk_name.len = fname->crypto_buf.len;
363 return 0;
364 }
365 if (!lookup)
366 return -ENOKEY;
367
368 /*
369 * We don't have the key and we are doing a lookup; decode the
370 * user-supplied name
371 */
372 if (iname->name[0] == '_') {
373 if (iname->len !=
374 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)))
375 return -ENOENT;
376 digested = 1;
377 } else {
378 if (iname->len >
379 BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
380 return -ENOENT;
381 digested = 0;
382 }
383
384 fname->crypto_buf.name =
385 kmalloc(max_t(size_t, FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
386 sizeof(struct fscrypt_digested_name)),
387 GFP_KERNEL);
388 if (fname->crypto_buf.name == NULL)
389 return -ENOMEM;
390
391 ret = digest_decode(iname->name + digested, iname->len - digested,
392 fname->crypto_buf.name);
393 if (ret < 0) {
394 ret = -ENOENT;
395 goto errout;
396 }
397 fname->crypto_buf.len = ret;
398 if (digested) {
399 const struct fscrypt_digested_name *n =
400 (const void *)fname->crypto_buf.name;
401 fname->hash = n->hash;
402 fname->minor_hash = n->minor_hash;
403 } else {
404 fname->disk_name.name = fname->crypto_buf.name;
405 fname->disk_name.len = fname->crypto_buf.len;
406 }
407 return 0;
408
409errout:
410 kfree(fname->crypto_buf.name);
411 return ret;
412}
413EXPORT_SYMBOL(fscrypt_setup_filename);