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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);
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/namei.h>
15#include <linux/scatterlist.h>
16#include <crypto/hash.h>
17#include <crypto/sha2.h>
18#include <crypto/skcipher.h>
19#include "fscrypt_private.h"
20
21/*
22 * struct fscrypt_nokey_name - identifier for directory entry when key is absent
23 *
24 * When userspace lists an encrypted directory without access to the key, the
25 * filesystem must present a unique "no-key name" for each filename that allows
26 * it to find the directory entry again if requested. Naively, that would just
27 * mean using the ciphertext filenames. However, since the ciphertext filenames
28 * can contain illegal characters ('\0' and '/'), they must be encoded in some
29 * way. We use base64. But that can cause names to exceed NAME_MAX (255
30 * bytes), so we also need to use a strong hash to abbreviate long names.
31 *
32 * The filesystem may also need another kind of hash, the "dirhash", to quickly
33 * find the directory entry. Since filesystems normally compute the dirhash
34 * over the on-disk filename (i.e. the ciphertext), it's not computable from
35 * no-key names that abbreviate the ciphertext using the strong hash to fit in
36 * NAME_MAX. It's also not computable if it's a keyed hash taken over the
37 * plaintext (but it may still be available in the on-disk directory entry);
38 * casefolded directories use this type of dirhash. At least in these cases,
39 * each no-key name must include the name's dirhash too.
40 *
41 * To meet all these requirements, we base64-encode the following
42 * variable-length structure. It contains the dirhash, or 0's if the filesystem
43 * didn't provide one; up to 149 bytes of the ciphertext name; and for
44 * ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes.
45 *
46 * This ensures that each no-key name contains everything needed to find the
47 * directory entry again, contains only legal characters, doesn't exceed
48 * NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only
49 * take the performance hit of SHA-256 on very long filenames (which are rare).
50 */
51struct fscrypt_nokey_name {
52 u32 dirhash[2];
53 u8 bytes[149];
54 u8 sha256[SHA256_DIGEST_SIZE];
55}; /* 189 bytes => 252 bytes base64-encoded, which is <= NAME_MAX (255) */
56
57/*
58 * Decoded size of max-size nokey name, i.e. a name that was abbreviated using
59 * the strong hash and thus includes the 'sha256' field. This isn't simply
60 * sizeof(struct fscrypt_nokey_name), as the padding at the end isn't included.
61 */
62#define FSCRYPT_NOKEY_NAME_MAX offsetofend(struct fscrypt_nokey_name, sha256)
63
64static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
65{
66 if (str->len == 1 && str->name[0] == '.')
67 return true;
68
69 if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
70 return true;
71
72 return false;
73}
74
75/**
76 * fscrypt_fname_encrypt() - encrypt a filename
77 * @inode: inode of the parent directory (for regular filenames)
78 * or of the symlink (for symlink targets)
79 * @iname: the filename to encrypt
80 * @out: (output) the encrypted filename
81 * @olen: size of the encrypted filename. It must be at least @iname->len.
82 * Any extra space is filled with NUL padding before encryption.
83 *
84 * Return: 0 on success, -errno on failure
85 */
86int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
87 u8 *out, unsigned int olen)
88{
89 struct skcipher_request *req = NULL;
90 DECLARE_CRYPTO_WAIT(wait);
91 const struct fscrypt_info *ci = inode->i_crypt_info;
92 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
93 union fscrypt_iv iv;
94 struct scatterlist sg;
95 int res;
96
97 /*
98 * Copy the filename to the output buffer for encrypting in-place and
99 * pad it with the needed number of NUL bytes.
100 */
101 if (WARN_ON(olen < iname->len))
102 return -ENOBUFS;
103 memcpy(out, iname->name, iname->len);
104 memset(out + iname->len, 0, olen - iname->len);
105
106 /* Initialize the IV */
107 fscrypt_generate_iv(&iv, 0, ci);
108
109 /* Set up the encryption request */
110 req = skcipher_request_alloc(tfm, GFP_NOFS);
111 if (!req)
112 return -ENOMEM;
113 skcipher_request_set_callback(req,
114 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
115 crypto_req_done, &wait);
116 sg_init_one(&sg, out, olen);
117 skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
118
119 /* Do the encryption */
120 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
121 skcipher_request_free(req);
122 if (res < 0) {
123 fscrypt_err(inode, "Filename encryption failed: %d", res);
124 return res;
125 }
126
127 return 0;
128}
129
130/**
131 * fname_decrypt() - decrypt a filename
132 * @inode: inode of the parent directory (for regular filenames)
133 * or of the symlink (for symlink targets)
134 * @iname: the encrypted filename to decrypt
135 * @oname: (output) the decrypted filename. The caller must have allocated
136 * enough space for this, e.g. using fscrypt_fname_alloc_buffer().
137 *
138 * Return: 0 on success, -errno on failure
139 */
140static int fname_decrypt(const struct inode *inode,
141 const struct fscrypt_str *iname,
142 struct fscrypt_str *oname)
143{
144 struct skcipher_request *req = NULL;
145 DECLARE_CRYPTO_WAIT(wait);
146 struct scatterlist src_sg, dst_sg;
147 const struct fscrypt_info *ci = inode->i_crypt_info;
148 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
149 union fscrypt_iv iv;
150 int res;
151
152 /* Allocate request */
153 req = skcipher_request_alloc(tfm, GFP_NOFS);
154 if (!req)
155 return -ENOMEM;
156 skcipher_request_set_callback(req,
157 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
158 crypto_req_done, &wait);
159
160 /* Initialize IV */
161 fscrypt_generate_iv(&iv, 0, ci);
162
163 /* Create decryption request */
164 sg_init_one(&src_sg, iname->name, iname->len);
165 sg_init_one(&dst_sg, oname->name, oname->len);
166 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
167 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
168 skcipher_request_free(req);
169 if (res < 0) {
170 fscrypt_err(inode, "Filename decryption failed: %d", res);
171 return res;
172 }
173
174 oname->len = strnlen(oname->name, iname->len);
175 return 0;
176}
177
178static const char lookup_table[65] =
179 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
180
181#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
182
183/**
184 * base64_encode() - base64-encode some bytes
185 * @src: the bytes to encode
186 * @len: number of bytes to encode
187 * @dst: (output) the base64-encoded string. Not NUL-terminated.
188 *
189 * Encodes the input string using characters from the set [A-Za-z0-9+,].
190 * The encoded string is roughly 4/3 times the size of the input string.
191 *
192 * Return: length of the encoded string
193 */
194static int base64_encode(const u8 *src, int len, char *dst)
195{
196 int i, bits = 0, ac = 0;
197 char *cp = dst;
198
199 for (i = 0; i < len; i++) {
200 ac += src[i] << bits;
201 bits += 8;
202 do {
203 *cp++ = lookup_table[ac & 0x3f];
204 ac >>= 6;
205 bits -= 6;
206 } while (bits >= 6);
207 }
208 if (bits)
209 *cp++ = lookup_table[ac & 0x3f];
210 return cp - dst;
211}
212
213static int base64_decode(const char *src, int len, u8 *dst)
214{
215 int i, bits = 0, ac = 0;
216 const char *p;
217 u8 *cp = dst;
218
219 for (i = 0; i < len; i++) {
220 p = strchr(lookup_table, src[i]);
221 if (p == NULL || src[i] == 0)
222 return -2;
223 ac += (p - lookup_table) << bits;
224 bits += 6;
225 if (bits >= 8) {
226 *cp++ = ac & 0xff;
227 ac >>= 8;
228 bits -= 8;
229 }
230 }
231 if (ac)
232 return -1;
233 return cp - dst;
234}
235
236bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
237 u32 orig_len, u32 max_len,
238 u32 *encrypted_len_ret)
239{
240 int padding = 4 << (fscrypt_policy_flags(policy) &
241 FSCRYPT_POLICY_FLAGS_PAD_MASK);
242 u32 encrypted_len;
243
244 if (orig_len > max_len)
245 return false;
246 encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
247 encrypted_len = round_up(encrypted_len, padding);
248 *encrypted_len_ret = min(encrypted_len, max_len);
249 return true;
250}
251
252/**
253 * fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames
254 * @max_encrypted_len: maximum length of encrypted filenames the buffer will be
255 * used to present
256 * @crypto_str: (output) buffer to allocate
257 *
258 * Allocate a buffer that is large enough to hold any decrypted or encoded
259 * filename (null-terminated), for the given maximum encrypted filename length.
260 *
261 * Return: 0 on success, -errno on failure
262 */
263int fscrypt_fname_alloc_buffer(u32 max_encrypted_len,
264 struct fscrypt_str *crypto_str)
265{
266 const u32 max_encoded_len = BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX);
267 u32 max_presented_len;
268
269 max_presented_len = max(max_encoded_len, max_encrypted_len);
270
271 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
272 if (!crypto_str->name)
273 return -ENOMEM;
274 crypto_str->len = max_presented_len;
275 return 0;
276}
277EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
278
279/**
280 * fscrypt_fname_free_buffer() - free a buffer for presented filenames
281 * @crypto_str: the buffer to free
282 *
283 * Free a buffer that was allocated by fscrypt_fname_alloc_buffer().
284 */
285void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
286{
287 if (!crypto_str)
288 return;
289 kfree(crypto_str->name);
290 crypto_str->name = NULL;
291}
292EXPORT_SYMBOL(fscrypt_fname_free_buffer);
293
294/**
295 * fscrypt_fname_disk_to_usr() - convert an encrypted filename to
296 * user-presentable form
297 * @inode: inode of the parent directory (for regular filenames)
298 * or of the symlink (for symlink targets)
299 * @hash: first part of the name's dirhash, if applicable. This only needs to
300 * be provided if the filename is located in an indexed directory whose
301 * encryption key may be unavailable. Not needed for symlink targets.
302 * @minor_hash: second part of the name's dirhash, if applicable
303 * @iname: encrypted filename to convert. May also be "." or "..", which
304 * aren't actually encrypted.
305 * @oname: output buffer for the user-presentable filename. The caller must
306 * have allocated enough space for this, e.g. using
307 * fscrypt_fname_alloc_buffer().
308 *
309 * If the key is available, we'll decrypt the disk name. Otherwise, we'll
310 * encode it for presentation in fscrypt_nokey_name format.
311 * See struct fscrypt_nokey_name for details.
312 *
313 * Return: 0 on success, -errno on failure
314 */
315int fscrypt_fname_disk_to_usr(const struct inode *inode,
316 u32 hash, u32 minor_hash,
317 const struct fscrypt_str *iname,
318 struct fscrypt_str *oname)
319{
320 const struct qstr qname = FSTR_TO_QSTR(iname);
321 struct fscrypt_nokey_name nokey_name;
322 u32 size; /* size of the unencoded no-key name */
323
324 if (fscrypt_is_dot_dotdot(&qname)) {
325 oname->name[0] = '.';
326 oname->name[iname->len - 1] = '.';
327 oname->len = iname->len;
328 return 0;
329 }
330
331 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
332 return -EUCLEAN;
333
334 if (fscrypt_has_encryption_key(inode))
335 return fname_decrypt(inode, iname, oname);
336
337 /*
338 * Sanity check that struct fscrypt_nokey_name doesn't have padding
339 * between fields and that its encoded size never exceeds NAME_MAX.
340 */
341 BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, dirhash) !=
342 offsetof(struct fscrypt_nokey_name, bytes));
343 BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) !=
344 offsetof(struct fscrypt_nokey_name, sha256));
345 BUILD_BUG_ON(BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX);
346
347 nokey_name.dirhash[0] = hash;
348 nokey_name.dirhash[1] = minor_hash;
349
350 if (iname->len <= sizeof(nokey_name.bytes)) {
351 memcpy(nokey_name.bytes, iname->name, iname->len);
352 size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]);
353 } else {
354 memcpy(nokey_name.bytes, iname->name, sizeof(nokey_name.bytes));
355 /* Compute strong hash of remaining part of name. */
356 sha256(&iname->name[sizeof(nokey_name.bytes)],
357 iname->len - sizeof(nokey_name.bytes),
358 nokey_name.sha256);
359 size = FSCRYPT_NOKEY_NAME_MAX;
360 }
361 oname->len = base64_encode((const u8 *)&nokey_name, size, oname->name);
362 return 0;
363}
364EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
365
366/**
367 * fscrypt_setup_filename() - prepare to search a possibly encrypted directory
368 * @dir: the directory that will be searched
369 * @iname: the user-provided filename being searched for
370 * @lookup: 1 if we're allowed to proceed without the key because it's
371 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
372 * proceed without the key because we're going to create the dir_entry.
373 * @fname: the filename information to be filled in
374 *
375 * Given a user-provided filename @iname, this function sets @fname->disk_name
376 * to the name that would be stored in the on-disk directory entry, if possible.
377 * If the directory is unencrypted this is simply @iname. Else, if we have the
378 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
379 * get the disk_name.
380 *
381 * Else, for keyless @lookup operations, @iname should be a no-key name, so we
382 * decode it to get the struct fscrypt_nokey_name. Non-@lookup operations will
383 * be impossible in this case, so we fail them with ENOKEY.
384 *
385 * If successful, fscrypt_free_filename() must be called later to clean up.
386 *
387 * Return: 0 on success, -errno on failure
388 */
389int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
390 int lookup, struct fscrypt_name *fname)
391{
392 struct fscrypt_nokey_name *nokey_name;
393 int ret;
394
395 memset(fname, 0, sizeof(struct fscrypt_name));
396 fname->usr_fname = iname;
397
398 if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
399 fname->disk_name.name = (unsigned char *)iname->name;
400 fname->disk_name.len = iname->len;
401 return 0;
402 }
403 ret = fscrypt_get_encryption_info(dir, lookup);
404 if (ret)
405 return ret;
406
407 if (fscrypt_has_encryption_key(dir)) {
408 if (!fscrypt_fname_encrypted_size(&dir->i_crypt_info->ci_policy,
409 iname->len,
410 dir->i_sb->s_cop->max_namelen,
411 &fname->crypto_buf.len))
412 return -ENAMETOOLONG;
413 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
414 GFP_NOFS);
415 if (!fname->crypto_buf.name)
416 return -ENOMEM;
417
418 ret = fscrypt_fname_encrypt(dir, iname, fname->crypto_buf.name,
419 fname->crypto_buf.len);
420 if (ret)
421 goto errout;
422 fname->disk_name.name = fname->crypto_buf.name;
423 fname->disk_name.len = fname->crypto_buf.len;
424 return 0;
425 }
426 if (!lookup)
427 return -ENOKEY;
428 fname->is_nokey_name = true;
429
430 /*
431 * We don't have the key and we are doing a lookup; decode the
432 * user-supplied name
433 */
434
435 if (iname->len > BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX))
436 return -ENOENT;
437
438 fname->crypto_buf.name = kmalloc(FSCRYPT_NOKEY_NAME_MAX, GFP_KERNEL);
439 if (fname->crypto_buf.name == NULL)
440 return -ENOMEM;
441
442 ret = base64_decode(iname->name, iname->len, fname->crypto_buf.name);
443 if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) ||
444 (ret > offsetof(struct fscrypt_nokey_name, sha256) &&
445 ret != FSCRYPT_NOKEY_NAME_MAX)) {
446 ret = -ENOENT;
447 goto errout;
448 }
449 fname->crypto_buf.len = ret;
450
451 nokey_name = (void *)fname->crypto_buf.name;
452 fname->hash = nokey_name->dirhash[0];
453 fname->minor_hash = nokey_name->dirhash[1];
454 if (ret != FSCRYPT_NOKEY_NAME_MAX) {
455 /* The full ciphertext filename is available. */
456 fname->disk_name.name = nokey_name->bytes;
457 fname->disk_name.len =
458 ret - offsetof(struct fscrypt_nokey_name, bytes);
459 }
460 return 0;
461
462errout:
463 kfree(fname->crypto_buf.name);
464 return ret;
465}
466EXPORT_SYMBOL(fscrypt_setup_filename);
467
468/**
469 * fscrypt_match_name() - test whether the given name matches a directory entry
470 * @fname: the name being searched for
471 * @de_name: the name from the directory entry
472 * @de_name_len: the length of @de_name in bytes
473 *
474 * Normally @fname->disk_name will be set, and in that case we simply compare
475 * that to the name stored in the directory entry. The only exception is that
476 * if we don't have the key for an encrypted directory and the name we're
477 * looking for is very long, then we won't have the full disk_name and instead
478 * we'll need to match against a fscrypt_nokey_name that includes a strong hash.
479 *
480 * Return: %true if the name matches, otherwise %false.
481 */
482bool fscrypt_match_name(const struct fscrypt_name *fname,
483 const u8 *de_name, u32 de_name_len)
484{
485 const struct fscrypt_nokey_name *nokey_name =
486 (const void *)fname->crypto_buf.name;
487 u8 digest[SHA256_DIGEST_SIZE];
488
489 if (likely(fname->disk_name.name)) {
490 if (de_name_len != fname->disk_name.len)
491 return false;
492 return !memcmp(de_name, fname->disk_name.name, de_name_len);
493 }
494 if (de_name_len <= sizeof(nokey_name->bytes))
495 return false;
496 if (memcmp(de_name, nokey_name->bytes, sizeof(nokey_name->bytes)))
497 return false;
498 sha256(&de_name[sizeof(nokey_name->bytes)],
499 de_name_len - sizeof(nokey_name->bytes), digest);
500 return !memcmp(digest, nokey_name->sha256, sizeof(digest));
501}
502EXPORT_SYMBOL_GPL(fscrypt_match_name);
503
504/**
505 * fscrypt_fname_siphash() - calculate the SipHash of a filename
506 * @dir: the parent directory
507 * @name: the filename to calculate the SipHash of
508 *
509 * Given a plaintext filename @name and a directory @dir which uses SipHash as
510 * its dirhash method and has had its fscrypt key set up, this function
511 * calculates the SipHash of that name using the directory's secret dirhash key.
512 *
513 * Return: the SipHash of @name using the hash key of @dir
514 */
515u64 fscrypt_fname_siphash(const struct inode *dir, const struct qstr *name)
516{
517 const struct fscrypt_info *ci = dir->i_crypt_info;
518
519 WARN_ON(!ci->ci_dirhash_key_initialized);
520
521 return siphash(name->name, name->len, &ci->ci_dirhash_key);
522}
523EXPORT_SYMBOL_GPL(fscrypt_fname_siphash);
524
525/*
526 * Validate dentries in encrypted directories to make sure we aren't potentially
527 * caching stale dentries after a key has been added.
528 */
529int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
530{
531 struct dentry *dir;
532 int err;
533 int valid;
534
535 /*
536 * Plaintext names are always valid, since fscrypt doesn't support
537 * reverting to no-key names without evicting the directory's inode
538 * -- which implies eviction of the dentries in the directory.
539 */
540 if (!(dentry->d_flags & DCACHE_NOKEY_NAME))
541 return 1;
542
543 /*
544 * No-key name; valid if the directory's key is still unavailable.
545 *
546 * Although fscrypt forbids rename() on no-key names, we still must use
547 * dget_parent() here rather than use ->d_parent directly. That's
548 * because a corrupted fs image may contain directory hard links, which
549 * the VFS handles by moving the directory's dentry tree in the dcache
550 * each time ->lookup() finds the directory and it already has a dentry
551 * elsewhere. Thus ->d_parent can be changing, and we must safely grab
552 * a reference to some ->d_parent to prevent it from being freed.
553 */
554
555 if (flags & LOOKUP_RCU)
556 return -ECHILD;
557
558 dir = dget_parent(dentry);
559 /*
560 * Pass allow_unsupported=true, so that files with an unsupported
561 * encryption policy can be deleted.
562 */
563 err = fscrypt_get_encryption_info(d_inode(dir), true);
564 valid = !fscrypt_has_encryption_key(d_inode(dir));
565 dput(dir);
566
567 if (err < 0)
568 return err;
569
570 return valid;
571}
572EXPORT_SYMBOL_GPL(fscrypt_d_revalidate);