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 | * The minimum message length (input and output length), in bytes, for all |
23 | * filenames encryption modes. Filenames shorter than this will be zero-padded |
24 | * before being encrypted. |
25 | */ |
26 | #define FSCRYPT_FNAME_MIN_MSG_LEN 16 |
27 | |
28 | /* |
29 | * struct fscrypt_nokey_name - identifier for directory entry when key is absent |
30 | * |
31 | * When userspace lists an encrypted directory without access to the key, the |
32 | * filesystem must present a unique "no-key name" for each filename that allows |
33 | * it to find the directory entry again if requested. Naively, that would just |
34 | * mean using the ciphertext filenames. However, since the ciphertext filenames |
35 | * can contain illegal characters ('\0' and '/'), they must be encoded in some |
36 | * way. We use base64url. But that can cause names to exceed NAME_MAX (255 |
37 | * bytes), so we also need to use a strong hash to abbreviate long names. |
38 | * |
39 | * The filesystem may also need another kind of hash, the "dirhash", to quickly |
40 | * find the directory entry. Since filesystems normally compute the dirhash |
41 | * over the on-disk filename (i.e. the ciphertext), it's not computable from |
42 | * no-key names that abbreviate the ciphertext using the strong hash to fit in |
43 | * NAME_MAX. It's also not computable if it's a keyed hash taken over the |
44 | * plaintext (but it may still be available in the on-disk directory entry); |
45 | * casefolded directories use this type of dirhash. At least in these cases, |
46 | * each no-key name must include the name's dirhash too. |
47 | * |
48 | * To meet all these requirements, we base64url-encode the following |
49 | * variable-length structure. It contains the dirhash, or 0's if the filesystem |
50 | * didn't provide one; up to 149 bytes of the ciphertext name; and for |
51 | * ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes. |
52 | * |
53 | * This ensures that each no-key name contains everything needed to find the |
54 | * directory entry again, contains only legal characters, doesn't exceed |
55 | * NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only |
56 | * take the performance hit of SHA-256 on very long filenames (which are rare). |
57 | */ |
58 | struct fscrypt_nokey_name { |
59 | u32 dirhash[2]; |
60 | u8 bytes[149]; |
61 | u8 sha256[SHA256_DIGEST_SIZE]; |
62 | }; /* 189 bytes => 252 bytes base64url-encoded, which is <= NAME_MAX (255) */ |
63 | |
64 | /* |
65 | * Decoded size of max-size no-key name, i.e. a name that was abbreviated using |
66 | * the strong hash and thus includes the 'sha256' field. This isn't simply |
67 | * sizeof(struct fscrypt_nokey_name), as the padding at the end isn't included. |
68 | */ |
69 | #define FSCRYPT_NOKEY_NAME_MAX offsetofend(struct fscrypt_nokey_name, sha256) |
70 | |
71 | /* Encoded size of max-size no-key name */ |
72 | #define FSCRYPT_NOKEY_NAME_MAX_ENCODED \ |
73 | FSCRYPT_BASE64URL_CHARS(FSCRYPT_NOKEY_NAME_MAX) |
74 | |
75 | static inline bool fscrypt_is_dot_dotdot(const struct qstr *str) |
76 | { |
77 | if (str->len == 1 && str->name[0] == '.') |
78 | return true; |
79 | |
80 | if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.') |
81 | return true; |
82 | |
83 | return false; |
84 | } |
85 | |
86 | /** |
87 | * fscrypt_fname_encrypt() - encrypt a filename |
88 | * @inode: inode of the parent directory (for regular filenames) |
89 | * or of the symlink (for symlink targets). Key must already be |
90 | * set up. |
91 | * @iname: the filename to encrypt |
92 | * @out: (output) the encrypted filename |
93 | * @olen: size of the encrypted filename. It must be at least @iname->len. |
94 | * Any extra space is filled with NUL padding before encryption. |
95 | * |
96 | * Return: 0 on success, -errno on failure |
97 | */ |
98 | int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname, |
99 | u8 *out, unsigned int olen) |
100 | { |
101 | struct skcipher_request *req = NULL; |
102 | DECLARE_CRYPTO_WAIT(wait); |
103 | const struct fscrypt_inode_info *ci = inode->i_crypt_info; |
104 | struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; |
105 | union fscrypt_iv iv; |
106 | struct scatterlist sg; |
107 | int res; |
108 | |
109 | /* |
110 | * Copy the filename to the output buffer for encrypting in-place and |
111 | * pad it with the needed number of NUL bytes. |
112 | */ |
113 | if (WARN_ON_ONCE(olen < iname->len)) |
114 | return -ENOBUFS; |
115 | memcpy(out, iname->name, iname->len); |
116 | memset(out + iname->len, 0, olen - iname->len); |
117 | |
118 | /* Initialize the IV */ |
119 | fscrypt_generate_iv(iv: &iv, index: 0, ci); |
120 | |
121 | /* Set up the encryption request */ |
122 | req = skcipher_request_alloc(tfm, GFP_NOFS); |
123 | if (!req) |
124 | return -ENOMEM; |
125 | skcipher_request_set_callback(req, |
126 | CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
127 | compl: crypto_req_done, data: &wait); |
128 | sg_init_one(&sg, out, olen); |
129 | skcipher_request_set_crypt(req, src: &sg, dst: &sg, cryptlen: olen, iv: &iv); |
130 | |
131 | /* Do the encryption */ |
132 | res = crypto_wait_req(err: crypto_skcipher_encrypt(req), wait: &wait); |
133 | skcipher_request_free(req); |
134 | if (res < 0) { |
135 | fscrypt_err(inode, "Filename encryption failed: %d" , res); |
136 | return res; |
137 | } |
138 | |
139 | return 0; |
140 | } |
141 | EXPORT_SYMBOL_GPL(fscrypt_fname_encrypt); |
142 | |
143 | /** |
144 | * fname_decrypt() - decrypt a filename |
145 | * @inode: inode of the parent directory (for regular filenames) |
146 | * or of the symlink (for symlink targets) |
147 | * @iname: the encrypted filename to decrypt |
148 | * @oname: (output) the decrypted filename. The caller must have allocated |
149 | * enough space for this, e.g. using fscrypt_fname_alloc_buffer(). |
150 | * |
151 | * Return: 0 on success, -errno on failure |
152 | */ |
153 | static int fname_decrypt(const struct inode *inode, |
154 | const struct fscrypt_str *iname, |
155 | struct fscrypt_str *oname) |
156 | { |
157 | struct skcipher_request *req = NULL; |
158 | DECLARE_CRYPTO_WAIT(wait); |
159 | struct scatterlist src_sg, dst_sg; |
160 | const struct fscrypt_inode_info *ci = inode->i_crypt_info; |
161 | struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; |
162 | union fscrypt_iv iv; |
163 | int res; |
164 | |
165 | /* Allocate request */ |
166 | req = skcipher_request_alloc(tfm, GFP_NOFS); |
167 | if (!req) |
168 | return -ENOMEM; |
169 | skcipher_request_set_callback(req, |
170 | CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
171 | compl: crypto_req_done, data: &wait); |
172 | |
173 | /* Initialize IV */ |
174 | fscrypt_generate_iv(iv: &iv, index: 0, ci); |
175 | |
176 | /* Create decryption request */ |
177 | sg_init_one(&src_sg, iname->name, iname->len); |
178 | sg_init_one(&dst_sg, oname->name, oname->len); |
179 | skcipher_request_set_crypt(req, src: &src_sg, dst: &dst_sg, cryptlen: iname->len, iv: &iv); |
180 | res = crypto_wait_req(err: crypto_skcipher_decrypt(req), wait: &wait); |
181 | skcipher_request_free(req); |
182 | if (res < 0) { |
183 | fscrypt_err(inode, "Filename decryption failed: %d" , res); |
184 | return res; |
185 | } |
186 | |
187 | oname->len = strnlen(p: oname->name, maxlen: iname->len); |
188 | return 0; |
189 | } |
190 | |
191 | static const char base64url_table[65] = |
192 | "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_" ; |
193 | |
194 | #define FSCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3) |
195 | |
196 | /** |
197 | * fscrypt_base64url_encode() - base64url-encode some binary data |
198 | * @src: the binary data to encode |
199 | * @srclen: the length of @src in bytes |
200 | * @dst: (output) the base64url-encoded string. Not NUL-terminated. |
201 | * |
202 | * Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL |
203 | * and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used, |
204 | * as it's unneeded and not required by the RFC. base64url is used instead of |
205 | * base64 to avoid the '/' character, which isn't allowed in filenames. |
206 | * |
207 | * Return: the length of the resulting base64url-encoded string in bytes. |
208 | * This will be equal to FSCRYPT_BASE64URL_CHARS(srclen). |
209 | */ |
210 | static int fscrypt_base64url_encode(const u8 *src, int srclen, char *dst) |
211 | { |
212 | u32 ac = 0; |
213 | int bits = 0; |
214 | int i; |
215 | char *cp = dst; |
216 | |
217 | for (i = 0; i < srclen; i++) { |
218 | ac = (ac << 8) | src[i]; |
219 | bits += 8; |
220 | do { |
221 | bits -= 6; |
222 | *cp++ = base64url_table[(ac >> bits) & 0x3f]; |
223 | } while (bits >= 6); |
224 | } |
225 | if (bits) |
226 | *cp++ = base64url_table[(ac << (6 - bits)) & 0x3f]; |
227 | return cp - dst; |
228 | } |
229 | |
230 | /** |
231 | * fscrypt_base64url_decode() - base64url-decode a string |
232 | * @src: the string to decode. Doesn't need to be NUL-terminated. |
233 | * @srclen: the length of @src in bytes |
234 | * @dst: (output) the decoded binary data |
235 | * |
236 | * Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with |
237 | * URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't |
238 | * accepted, nor are non-encoding characters such as whitespace. |
239 | * |
240 | * This implementation hasn't been optimized for performance. |
241 | * |
242 | * Return: the length of the resulting decoded binary data in bytes, |
243 | * or -1 if the string isn't a valid base64url string. |
244 | */ |
245 | static int fscrypt_base64url_decode(const char *src, int srclen, u8 *dst) |
246 | { |
247 | u32 ac = 0; |
248 | int bits = 0; |
249 | int i; |
250 | u8 *bp = dst; |
251 | |
252 | for (i = 0; i < srclen; i++) { |
253 | const char *p = strchr(base64url_table, src[i]); |
254 | |
255 | if (p == NULL || src[i] == 0) |
256 | return -1; |
257 | ac = (ac << 6) | (p - base64url_table); |
258 | bits += 6; |
259 | if (bits >= 8) { |
260 | bits -= 8; |
261 | *bp++ = (u8)(ac >> bits); |
262 | } |
263 | } |
264 | if (ac & ((1 << bits) - 1)) |
265 | return -1; |
266 | return bp - dst; |
267 | } |
268 | |
269 | bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy, |
270 | u32 orig_len, u32 max_len, |
271 | u32 *encrypted_len_ret) |
272 | { |
273 | int padding = 4 << (fscrypt_policy_flags(policy) & |
274 | FSCRYPT_POLICY_FLAGS_PAD_MASK); |
275 | u32 encrypted_len; |
276 | |
277 | if (orig_len > max_len) |
278 | return false; |
279 | encrypted_len = max_t(u32, orig_len, FSCRYPT_FNAME_MIN_MSG_LEN); |
280 | encrypted_len = round_up(encrypted_len, padding); |
281 | *encrypted_len_ret = min(encrypted_len, max_len); |
282 | return true; |
283 | } |
284 | |
285 | /** |
286 | * fscrypt_fname_encrypted_size() - calculate length of encrypted filename |
287 | * @inode: parent inode of dentry name being encrypted. Key must |
288 | * already be set up. |
289 | * @orig_len: length of the original filename |
290 | * @max_len: maximum length to return |
291 | * @encrypted_len_ret: where calculated length should be returned (on success) |
292 | * |
293 | * Filenames that are shorter than the maximum length may have their lengths |
294 | * increased slightly by encryption, due to padding that is applied. |
295 | * |
296 | * Return: false if the orig_len is greater than max_len. Otherwise, true and |
297 | * fill out encrypted_len_ret with the length (up to max_len). |
298 | */ |
299 | bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, |
300 | u32 max_len, u32 *encrypted_len_ret) |
301 | { |
302 | return __fscrypt_fname_encrypted_size(policy: &inode->i_crypt_info->ci_policy, |
303 | orig_len, max_len, |
304 | encrypted_len_ret); |
305 | } |
306 | EXPORT_SYMBOL_GPL(fscrypt_fname_encrypted_size); |
307 | |
308 | /** |
309 | * fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames |
310 | * @max_encrypted_len: maximum length of encrypted filenames the buffer will be |
311 | * used to present |
312 | * @crypto_str: (output) buffer to allocate |
313 | * |
314 | * Allocate a buffer that is large enough to hold any decrypted or encoded |
315 | * filename (null-terminated), for the given maximum encrypted filename length. |
316 | * |
317 | * Return: 0 on success, -errno on failure |
318 | */ |
319 | int fscrypt_fname_alloc_buffer(u32 max_encrypted_len, |
320 | struct fscrypt_str *crypto_str) |
321 | { |
322 | u32 max_presented_len = max_t(u32, FSCRYPT_NOKEY_NAME_MAX_ENCODED, |
323 | max_encrypted_len); |
324 | |
325 | crypto_str->name = kmalloc(size: max_presented_len + 1, GFP_NOFS); |
326 | if (!crypto_str->name) |
327 | return -ENOMEM; |
328 | crypto_str->len = max_presented_len; |
329 | return 0; |
330 | } |
331 | EXPORT_SYMBOL(fscrypt_fname_alloc_buffer); |
332 | |
333 | /** |
334 | * fscrypt_fname_free_buffer() - free a buffer for presented filenames |
335 | * @crypto_str: the buffer to free |
336 | * |
337 | * Free a buffer that was allocated by fscrypt_fname_alloc_buffer(). |
338 | */ |
339 | void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) |
340 | { |
341 | if (!crypto_str) |
342 | return; |
343 | kfree(objp: crypto_str->name); |
344 | crypto_str->name = NULL; |
345 | } |
346 | EXPORT_SYMBOL(fscrypt_fname_free_buffer); |
347 | |
348 | /** |
349 | * fscrypt_fname_disk_to_usr() - convert an encrypted filename to |
350 | * user-presentable form |
351 | * @inode: inode of the parent directory (for regular filenames) |
352 | * or of the symlink (for symlink targets) |
353 | * @hash: first part of the name's dirhash, if applicable. This only needs to |
354 | * be provided if the filename is located in an indexed directory whose |
355 | * encryption key may be unavailable. Not needed for symlink targets. |
356 | * @minor_hash: second part of the name's dirhash, if applicable |
357 | * @iname: encrypted filename to convert. May also be "." or "..", which |
358 | * aren't actually encrypted. |
359 | * @oname: output buffer for the user-presentable filename. The caller must |
360 | * have allocated enough space for this, e.g. using |
361 | * fscrypt_fname_alloc_buffer(). |
362 | * |
363 | * If the key is available, we'll decrypt the disk name. Otherwise, we'll |
364 | * encode it for presentation in fscrypt_nokey_name format. |
365 | * See struct fscrypt_nokey_name for details. |
366 | * |
367 | * Return: 0 on success, -errno on failure |
368 | */ |
369 | int fscrypt_fname_disk_to_usr(const struct inode *inode, |
370 | u32 hash, u32 minor_hash, |
371 | const struct fscrypt_str *iname, |
372 | struct fscrypt_str *oname) |
373 | { |
374 | const struct qstr qname = FSTR_TO_QSTR(iname); |
375 | struct fscrypt_nokey_name nokey_name; |
376 | u32 size; /* size of the unencoded no-key name */ |
377 | |
378 | if (fscrypt_is_dot_dotdot(str: &qname)) { |
379 | oname->name[0] = '.'; |
380 | oname->name[iname->len - 1] = '.'; |
381 | oname->len = iname->len; |
382 | return 0; |
383 | } |
384 | |
385 | if (iname->len < FSCRYPT_FNAME_MIN_MSG_LEN) |
386 | return -EUCLEAN; |
387 | |
388 | if (fscrypt_has_encryption_key(inode)) |
389 | return fname_decrypt(inode, iname, oname); |
390 | |
391 | /* |
392 | * Sanity check that struct fscrypt_nokey_name doesn't have padding |
393 | * between fields and that its encoded size never exceeds NAME_MAX. |
394 | */ |
395 | BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, dirhash) != |
396 | offsetof(struct fscrypt_nokey_name, bytes)); |
397 | BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) != |
398 | offsetof(struct fscrypt_nokey_name, sha256)); |
399 | BUILD_BUG_ON(FSCRYPT_NOKEY_NAME_MAX_ENCODED > NAME_MAX); |
400 | |
401 | nokey_name.dirhash[0] = hash; |
402 | nokey_name.dirhash[1] = minor_hash; |
403 | |
404 | if (iname->len <= sizeof(nokey_name.bytes)) { |
405 | memcpy(nokey_name.bytes, iname->name, iname->len); |
406 | size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]); |
407 | } else { |
408 | memcpy(nokey_name.bytes, iname->name, sizeof(nokey_name.bytes)); |
409 | /* Compute strong hash of remaining part of name. */ |
410 | sha256(data: &iname->name[sizeof(nokey_name.bytes)], |
411 | len: iname->len - sizeof(nokey_name.bytes), |
412 | out: nokey_name.sha256); |
413 | size = FSCRYPT_NOKEY_NAME_MAX; |
414 | } |
415 | oname->len = fscrypt_base64url_encode(src: (const u8 *)&nokey_name, srclen: size, |
416 | dst: oname->name); |
417 | return 0; |
418 | } |
419 | EXPORT_SYMBOL(fscrypt_fname_disk_to_usr); |
420 | |
421 | /** |
422 | * fscrypt_setup_filename() - prepare to search a possibly encrypted directory |
423 | * @dir: the directory that will be searched |
424 | * @iname: the user-provided filename being searched for |
425 | * @lookup: 1 if we're allowed to proceed without the key because it's |
426 | * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot |
427 | * proceed without the key because we're going to create the dir_entry. |
428 | * @fname: the filename information to be filled in |
429 | * |
430 | * Given a user-provided filename @iname, this function sets @fname->disk_name |
431 | * to the name that would be stored in the on-disk directory entry, if possible. |
432 | * If the directory is unencrypted this is simply @iname. Else, if we have the |
433 | * directory's encryption key, then @iname is the plaintext, so we encrypt it to |
434 | * get the disk_name. |
435 | * |
436 | * Else, for keyless @lookup operations, @iname should be a no-key name, so we |
437 | * decode it to get the struct fscrypt_nokey_name. Non-@lookup operations will |
438 | * be impossible in this case, so we fail them with ENOKEY. |
439 | * |
440 | * If successful, fscrypt_free_filename() must be called later to clean up. |
441 | * |
442 | * Return: 0 on success, -errno on failure |
443 | */ |
444 | int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, |
445 | int lookup, struct fscrypt_name *fname) |
446 | { |
447 | struct fscrypt_nokey_name *nokey_name; |
448 | int ret; |
449 | |
450 | memset(fname, 0, sizeof(struct fscrypt_name)); |
451 | fname->usr_fname = iname; |
452 | |
453 | if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(str: iname)) { |
454 | fname->disk_name.name = (unsigned char *)iname->name; |
455 | fname->disk_name.len = iname->len; |
456 | return 0; |
457 | } |
458 | ret = fscrypt_get_encryption_info(inode: dir, allow_unsupported: lookup); |
459 | if (ret) |
460 | return ret; |
461 | |
462 | if (fscrypt_has_encryption_key(inode: dir)) { |
463 | if (!fscrypt_fname_encrypted_size(dir, iname->len, NAME_MAX, |
464 | &fname->crypto_buf.len)) |
465 | return -ENAMETOOLONG; |
466 | fname->crypto_buf.name = kmalloc(size: fname->crypto_buf.len, |
467 | GFP_NOFS); |
468 | if (!fname->crypto_buf.name) |
469 | return -ENOMEM; |
470 | |
471 | ret = fscrypt_fname_encrypt(dir, iname, fname->crypto_buf.name, |
472 | fname->crypto_buf.len); |
473 | if (ret) |
474 | goto errout; |
475 | fname->disk_name.name = fname->crypto_buf.name; |
476 | fname->disk_name.len = fname->crypto_buf.len; |
477 | return 0; |
478 | } |
479 | if (!lookup) |
480 | return -ENOKEY; |
481 | fname->is_nokey_name = true; |
482 | |
483 | /* |
484 | * We don't have the key and we are doing a lookup; decode the |
485 | * user-supplied name |
486 | */ |
487 | |
488 | if (iname->len > FSCRYPT_NOKEY_NAME_MAX_ENCODED) |
489 | return -ENOENT; |
490 | |
491 | fname->crypto_buf.name = kmalloc(FSCRYPT_NOKEY_NAME_MAX, GFP_KERNEL); |
492 | if (fname->crypto_buf.name == NULL) |
493 | return -ENOMEM; |
494 | |
495 | ret = fscrypt_base64url_decode(src: iname->name, srclen: iname->len, |
496 | dst: fname->crypto_buf.name); |
497 | if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) || |
498 | (ret > offsetof(struct fscrypt_nokey_name, sha256) && |
499 | ret != FSCRYPT_NOKEY_NAME_MAX)) { |
500 | ret = -ENOENT; |
501 | goto errout; |
502 | } |
503 | fname->crypto_buf.len = ret; |
504 | |
505 | nokey_name = (void *)fname->crypto_buf.name; |
506 | fname->hash = nokey_name->dirhash[0]; |
507 | fname->minor_hash = nokey_name->dirhash[1]; |
508 | if (ret != FSCRYPT_NOKEY_NAME_MAX) { |
509 | /* The full ciphertext filename is available. */ |
510 | fname->disk_name.name = nokey_name->bytes; |
511 | fname->disk_name.len = |
512 | ret - offsetof(struct fscrypt_nokey_name, bytes); |
513 | } |
514 | return 0; |
515 | |
516 | errout: |
517 | kfree(objp: fname->crypto_buf.name); |
518 | return ret; |
519 | } |
520 | EXPORT_SYMBOL(fscrypt_setup_filename); |
521 | |
522 | /** |
523 | * fscrypt_match_name() - test whether the given name matches a directory entry |
524 | * @fname: the name being searched for |
525 | * @de_name: the name from the directory entry |
526 | * @de_name_len: the length of @de_name in bytes |
527 | * |
528 | * Normally @fname->disk_name will be set, and in that case we simply compare |
529 | * that to the name stored in the directory entry. The only exception is that |
530 | * if we don't have the key for an encrypted directory and the name we're |
531 | * looking for is very long, then we won't have the full disk_name and instead |
532 | * we'll need to match against a fscrypt_nokey_name that includes a strong hash. |
533 | * |
534 | * Return: %true if the name matches, otherwise %false. |
535 | */ |
536 | bool fscrypt_match_name(const struct fscrypt_name *fname, |
537 | const u8 *de_name, u32 de_name_len) |
538 | { |
539 | const struct fscrypt_nokey_name *nokey_name = |
540 | (const void *)fname->crypto_buf.name; |
541 | u8 digest[SHA256_DIGEST_SIZE]; |
542 | |
543 | if (likely(fname->disk_name.name)) { |
544 | if (de_name_len != fname->disk_name.len) |
545 | return false; |
546 | return !memcmp(p: de_name, q: fname->disk_name.name, size: de_name_len); |
547 | } |
548 | if (de_name_len <= sizeof(nokey_name->bytes)) |
549 | return false; |
550 | if (memcmp(p: de_name, q: nokey_name->bytes, size: sizeof(nokey_name->bytes))) |
551 | return false; |
552 | sha256(data: &de_name[sizeof(nokey_name->bytes)], |
553 | len: de_name_len - sizeof(nokey_name->bytes), out: digest); |
554 | return !memcmp(p: digest, q: nokey_name->sha256, size: sizeof(digest)); |
555 | } |
556 | EXPORT_SYMBOL_GPL(fscrypt_match_name); |
557 | |
558 | /** |
559 | * fscrypt_fname_siphash() - calculate the SipHash of a filename |
560 | * @dir: the parent directory |
561 | * @name: the filename to calculate the SipHash of |
562 | * |
563 | * Given a plaintext filename @name and a directory @dir which uses SipHash as |
564 | * its dirhash method and has had its fscrypt key set up, this function |
565 | * calculates the SipHash of that name using the directory's secret dirhash key. |
566 | * |
567 | * Return: the SipHash of @name using the hash key of @dir |
568 | */ |
569 | u64 fscrypt_fname_siphash(const struct inode *dir, const struct qstr *name) |
570 | { |
571 | const struct fscrypt_inode_info *ci = dir->i_crypt_info; |
572 | |
573 | WARN_ON_ONCE(!ci->ci_dirhash_key_initialized); |
574 | |
575 | return siphash(data: name->name, len: name->len, key: &ci->ci_dirhash_key); |
576 | } |
577 | EXPORT_SYMBOL_GPL(fscrypt_fname_siphash); |
578 | |
579 | /* |
580 | * Validate dentries in encrypted directories to make sure we aren't potentially |
581 | * caching stale dentries after a key has been added. |
582 | */ |
583 | int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) |
584 | { |
585 | struct dentry *dir; |
586 | int err; |
587 | int valid; |
588 | |
589 | /* |
590 | * Plaintext names are always valid, since fscrypt doesn't support |
591 | * reverting to no-key names without evicting the directory's inode |
592 | * -- which implies eviction of the dentries in the directory. |
593 | */ |
594 | if (!(dentry->d_flags & DCACHE_NOKEY_NAME)) |
595 | return 1; |
596 | |
597 | /* |
598 | * No-key name; valid if the directory's key is still unavailable. |
599 | * |
600 | * Although fscrypt forbids rename() on no-key names, we still must use |
601 | * dget_parent() here rather than use ->d_parent directly. That's |
602 | * because a corrupted fs image may contain directory hard links, which |
603 | * the VFS handles by moving the directory's dentry tree in the dcache |
604 | * each time ->lookup() finds the directory and it already has a dentry |
605 | * elsewhere. Thus ->d_parent can be changing, and we must safely grab |
606 | * a reference to some ->d_parent to prevent it from being freed. |
607 | */ |
608 | |
609 | if (flags & LOOKUP_RCU) |
610 | return -ECHILD; |
611 | |
612 | dir = dget_parent(dentry); |
613 | /* |
614 | * Pass allow_unsupported=true, so that files with an unsupported |
615 | * encryption policy can be deleted. |
616 | */ |
617 | err = fscrypt_get_encryption_info(inode: d_inode(dentry: dir), allow_unsupported: true); |
618 | valid = !fscrypt_has_encryption_key(inode: d_inode(dentry: dir)); |
619 | dput(dir); |
620 | |
621 | if (err < 0) |
622 | return err; |
623 | |
624 | return valid; |
625 | } |
626 | EXPORT_SYMBOL_GPL(fscrypt_d_revalidate); |
627 | |