Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
6b3bd08f | 2 | /* |
0b81d077 | 3 | * This contains functions for filename crypto management |
6b3bd08f JK |
4 | * |
5 | * Copyright (C) 2015, Google, Inc. | |
6 | * Copyright (C) 2015, Motorola Mobility | |
7 | * | |
6b3bd08f | 8 | * Written by Uday Savagaonkar, 2014. |
0b81d077 | 9 | * Modified by Jaegeuk Kim, 2015. |
6b3bd08f JK |
10 | * |
11 | * This has not yet undergone a rigorous security audit. | |
12 | */ | |
0b81d077 | 13 | |
6b3bd08f | 14 | #include <linux/scatterlist.h> |
6b3bd08f | 15 | #include <linux/ratelimit.h> |
a575784c | 16 | #include <crypto/skcipher.h> |
3325bea5 | 17 | #include "fscrypt_private.h" |
6b3bd08f | 18 | |
dcf0db9e EB |
19 | static 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 | ||
6b3bd08f | 30 | /** |
ef1eb3aa | 31 | * fname_encrypt() - encrypt a filename |
6b3bd08f | 32 | * |
50c961de EB |
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. | |
ef1eb3aa EB |
35 | * |
36 | * Return: 0 on success, -errno on failure | |
6b3bd08f | 37 | */ |
50c961de EB |
38 | int fname_encrypt(struct inode *inode, const struct qstr *iname, |
39 | u8 *out, unsigned int olen) | |
6b3bd08f | 40 | { |
2731a944 | 41 | struct skcipher_request *req = NULL; |
d0082e1a | 42 | DECLARE_CRYPTO_WAIT(wait); |
50c961de | 43 | struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm; |
6b3bd08f | 44 | int res = 0; |
0b81d077 | 45 | char iv[FS_CRYPTO_BLOCK_SIZE]; |
08ae877f | 46 | struct scatterlist sg; |
6b3bd08f | 47 | |
08ae877f EB |
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 | */ | |
50c961de | 52 | if (WARN_ON(olen < iname->len)) |
76e81d6d | 53 | return -ENOBUFS; |
50c961de EB |
54 | memcpy(out, iname->name, iname->len); |
55 | memset(out + iname->len, 0, olen - iname->len); | |
6b3bd08f | 56 | |
08ae877f EB |
57 | /* Initialize the IV */ |
58 | memset(iv, 0, FS_CRYPTO_BLOCK_SIZE); | |
6b3bd08f | 59 | |
08ae877f | 60 | /* Set up the encryption request */ |
2731a944 | 61 | req = skcipher_request_alloc(tfm, GFP_NOFS); |
c90fd775 | 62 | if (!req) |
6b3bd08f | 63 | return -ENOMEM; |
2731a944 | 64 | skcipher_request_set_callback(req, |
6b3bd08f | 65 | CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
d0082e1a | 66 | crypto_req_done, &wait); |
50c961de EB |
67 | sg_init_one(&sg, out, olen); |
68 | skcipher_request_set_crypt(req, &sg, &sg, olen, iv); | |
6b3bd08f | 69 | |
08ae877f | 70 | /* Do the encryption */ |
d0082e1a | 71 | res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); |
2731a944 | 72 | skcipher_request_free(req); |
ef1eb3aa | 73 | if (res < 0) { |
544d08fd EB |
74 | fscrypt_err(inode->i_sb, |
75 | "Filename encryption failed for inode %lu: %d", | |
76 | inode->i_ino, res); | |
ef1eb3aa EB |
77 | return res; |
78 | } | |
0b81d077 | 79 | |
ef1eb3aa | 80 | return 0; |
6b3bd08f JK |
81 | } |
82 | ||
ef1eb3aa EB |
83 | /** |
84 | * fname_decrypt() - decrypt a filename | |
85 | * | |
86 | * The caller must have allocated sufficient memory for the @oname string. | |
87 | * | |
88 | * Return: 0 on success, -errno on failure | |
6b3bd08f | 89 | */ |
0b81d077 JK |
90 | static int fname_decrypt(struct inode *inode, |
91 | const struct fscrypt_str *iname, | |
92 | struct fscrypt_str *oname) | |
6b3bd08f | 93 | { |
2731a944 | 94 | struct skcipher_request *req = NULL; |
d0082e1a | 95 | DECLARE_CRYPTO_WAIT(wait); |
6b3bd08f | 96 | struct scatterlist src_sg, dst_sg; |
54632f02 | 97 | struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm; |
6b3bd08f | 98 | int res = 0; |
0b81d077 | 99 | char iv[FS_CRYPTO_BLOCK_SIZE]; |
6b3bd08f | 100 | |
6b3bd08f | 101 | /* Allocate request */ |
2731a944 | 102 | req = skcipher_request_alloc(tfm, GFP_NOFS); |
c90fd775 | 103 | if (!req) |
6b3bd08f | 104 | return -ENOMEM; |
2731a944 | 105 | skcipher_request_set_callback(req, |
6b3bd08f | 106 | CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
d0082e1a | 107 | crypto_req_done, &wait); |
6b3bd08f JK |
108 | |
109 | /* Initialize IV */ | |
0b81d077 | 110 | memset(iv, 0, FS_CRYPTO_BLOCK_SIZE); |
6b3bd08f JK |
111 | |
112 | /* Create decryption request */ | |
113 | sg_init_one(&src_sg, iname->name, iname->len); | |
114 | sg_init_one(&dst_sg, oname->name, oname->len); | |
2731a944 | 115 | skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv); |
d0082e1a | 116 | res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); |
2731a944 | 117 | skcipher_request_free(req); |
6b3bd08f | 118 | if (res < 0) { |
544d08fd EB |
119 | fscrypt_err(inode->i_sb, |
120 | "Filename decryption failed for inode %lu: %d", | |
121 | inode->i_ino, res); | |
6b3bd08f JK |
122 | return res; |
123 | } | |
124 | ||
125 | oname->len = strnlen(oname->name, iname->len); | |
ef1eb3aa | 126 | return 0; |
6b3bd08f JK |
127 | } |
128 | ||
129 | static const char *lookup_table = | |
130 | "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,"; | |
131 | ||
17159420 EB |
132 | #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3) |
133 | ||
6b3bd08f | 134 | /** |
0b81d077 | 135 | * digest_encode() - |
6b3bd08f JK |
136 | * |
137 | * Encodes the input digest using characters from the set [a-zA-Z0-9_+]. | |
138 | * The encoded string is roughly 4/3 times the size of the input string. | |
139 | */ | |
140 | static int digest_encode(const char *src, int len, char *dst) | |
141 | { | |
142 | int i = 0, bits = 0, ac = 0; | |
143 | char *cp = dst; | |
144 | ||
145 | while (i < len) { | |
146 | ac += (((unsigned char) src[i]) << bits); | |
147 | bits += 8; | |
148 | do { | |
149 | *cp++ = lookup_table[ac & 0x3f]; | |
150 | ac >>= 6; | |
151 | bits -= 6; | |
152 | } while (bits >= 6); | |
153 | i++; | |
154 | } | |
155 | if (bits) | |
156 | *cp++ = lookup_table[ac & 0x3f]; | |
157 | return cp - dst; | |
158 | } | |
159 | ||
160 | static int digest_decode(const char *src, int len, char *dst) | |
161 | { | |
162 | int i = 0, bits = 0, ac = 0; | |
163 | const char *p; | |
164 | char *cp = dst; | |
165 | ||
166 | while (i < len) { | |
167 | p = strchr(lookup_table, src[i]); | |
168 | if (p == NULL || src[i] == 0) | |
169 | return -2; | |
170 | ac += (p - lookup_table) << bits; | |
171 | bits += 6; | |
172 | if (bits >= 8) { | |
173 | *cp++ = ac & 0xff; | |
174 | ac >>= 8; | |
175 | bits -= 8; | |
176 | } | |
177 | i++; | |
178 | } | |
179 | if (ac) | |
180 | return -1; | |
181 | return cp - dst; | |
182 | } | |
183 | ||
b9db0b4a EB |
184 | bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, |
185 | u32 max_len, u32 *encrypted_len_ret) | |
6b3bd08f | 186 | { |
b9db0b4a EB |
187 | int padding = 4 << (inode->i_crypt_info->ci_flags & |
188 | FS_POLICY_FLAGS_PAD_MASK); | |
189 | u32 encrypted_len; | |
190 | ||
191 | if (orig_len > max_len) | |
192 | return false; | |
193 | encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE); | |
194 | encrypted_len = round_up(encrypted_len, padding); | |
195 | *encrypted_len_ret = min(encrypted_len, max_len); | |
196 | return true; | |
6b3bd08f JK |
197 | } |
198 | ||
199 | /** | |
2cbadadc | 200 | * fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames |
6b3bd08f | 201 | * |
2cbadadc EB |
202 | * Allocate a buffer that is large enough to hold any decrypted or encoded |
203 | * filename (null-terminated), for the given maximum encrypted filename length. | |
204 | * | |
205 | * Return: 0 on success, -errno on failure | |
6b3bd08f | 206 | */ |
0b93e1b9 | 207 | int fscrypt_fname_alloc_buffer(const struct inode *inode, |
2cbadadc EB |
208 | u32 max_encrypted_len, |
209 | struct fscrypt_str *crypto_str) | |
6b3bd08f | 210 | { |
17159420 EB |
211 | const u32 max_encoded_len = |
212 | max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE), | |
213 | 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name))); | |
2cbadadc | 214 | u32 max_presented_len; |
6b3bd08f | 215 | |
2cbadadc | 216 | max_presented_len = max(max_encoded_len, max_encrypted_len); |
17159420 | 217 | |
2cbadadc EB |
218 | crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS); |
219 | if (!crypto_str->name) | |
6b3bd08f | 220 | return -ENOMEM; |
2cbadadc | 221 | crypto_str->len = max_presented_len; |
6b3bd08f JK |
222 | return 0; |
223 | } | |
0b81d077 | 224 | EXPORT_SYMBOL(fscrypt_fname_alloc_buffer); |
6b3bd08f JK |
225 | |
226 | /** | |
2cbadadc | 227 | * fscrypt_fname_free_buffer - free the buffer for presented filenames |
6b3bd08f | 228 | * |
2cbadadc | 229 | * Free the buffer allocated by fscrypt_fname_alloc_buffer(). |
6b3bd08f | 230 | */ |
0b81d077 | 231 | void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) |
6b3bd08f JK |
232 | { |
233 | if (!crypto_str) | |
234 | return; | |
235 | kfree(crypto_str->name); | |
236 | crypto_str->name = NULL; | |
237 | } | |
0b81d077 | 238 | EXPORT_SYMBOL(fscrypt_fname_free_buffer); |
6b3bd08f JK |
239 | |
240 | /** | |
0b81d077 JK |
241 | * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user |
242 | * space | |
ef1eb3aa EB |
243 | * |
244 | * The caller must have allocated sufficient memory for the @oname string. | |
245 | * | |
17159420 EB |
246 | * If the key is available, we'll decrypt the disk name; otherwise, we'll encode |
247 | * it for presentation. Short names are directly base64-encoded, while long | |
248 | * names are encoded in fscrypt_digested_name format. | |
249 | * | |
ef1eb3aa | 250 | * Return: 0 on success, -errno on failure |
6b3bd08f | 251 | */ |
0b81d077 JK |
252 | int fscrypt_fname_disk_to_usr(struct inode *inode, |
253 | u32 hash, u32 minor_hash, | |
254 | const struct fscrypt_str *iname, | |
255 | struct fscrypt_str *oname) | |
6b3bd08f JK |
256 | { |
257 | const struct qstr qname = FSTR_TO_QSTR(iname); | |
17159420 | 258 | struct fscrypt_digested_name digested_name; |
6b3bd08f | 259 | |
0b81d077 | 260 | if (fscrypt_is_dot_dotdot(&qname)) { |
6b3bd08f JK |
261 | oname->name[0] = '.'; |
262 | oname->name[iname->len - 1] = '.'; | |
263 | oname->len = iname->len; | |
ef1eb3aa | 264 | return 0; |
6b3bd08f JK |
265 | } |
266 | ||
0b81d077 | 267 | if (iname->len < FS_CRYPTO_BLOCK_SIZE) |
1dafa51d | 268 | return -EUCLEAN; |
6b3bd08f | 269 | |
0b81d077 JK |
270 | if (inode->i_crypt_info) |
271 | return fname_decrypt(inode, iname, oname); | |
272 | ||
17159420 | 273 | if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) { |
ef1eb3aa EB |
274 | oname->len = digest_encode(iname->name, iname->len, |
275 | oname->name); | |
276 | return 0; | |
6b3bd08f JK |
277 | } |
278 | if (hash) { | |
17159420 EB |
279 | digested_name.hash = hash; |
280 | digested_name.minor_hash = minor_hash; | |
0b81d077 | 281 | } else { |
17159420 EB |
282 | digested_name.hash = 0; |
283 | digested_name.minor_hash = 0; | |
0b81d077 | 284 | } |
17159420 EB |
285 | memcpy(digested_name.digest, |
286 | FSCRYPT_FNAME_DIGEST(iname->name, iname->len), | |
287 | FSCRYPT_FNAME_DIGEST_SIZE); | |
6b3bd08f | 288 | oname->name[0] = '_'; |
17159420 EB |
289 | oname->len = 1 + digest_encode((const char *)&digested_name, |
290 | sizeof(digested_name), oname->name + 1); | |
ef1eb3aa | 291 | return 0; |
6b3bd08f | 292 | } |
0b81d077 | 293 | EXPORT_SYMBOL(fscrypt_fname_disk_to_usr); |
6b3bd08f | 294 | |
17159420 EB |
295 | /** |
296 | * fscrypt_setup_filename() - prepare to search a possibly encrypted directory | |
297 | * @dir: the directory that will be searched | |
298 | * @iname: the user-provided filename being searched for | |
299 | * @lookup: 1 if we're allowed to proceed without the key because it's | |
300 | * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot | |
301 | * proceed without the key because we're going to create the dir_entry. | |
302 | * @fname: the filename information to be filled in | |
303 | * | |
304 | * Given a user-provided filename @iname, this function sets @fname->disk_name | |
305 | * to the name that would be stored in the on-disk directory entry, if possible. | |
306 | * If the directory is unencrypted this is simply @iname. Else, if we have the | |
307 | * directory's encryption key, then @iname is the plaintext, so we encrypt it to | |
308 | * get the disk_name. | |
309 | * | |
310 | * Else, for keyless @lookup operations, @iname is the presented ciphertext, so | |
311 | * we decode it to get either the ciphertext disk_name (for short names) or the | |
312 | * fscrypt_digested_name (for long names). Non-@lookup operations will be | |
313 | * impossible in this case, so we fail them with ENOKEY. | |
314 | * | |
315 | * If successful, fscrypt_free_filename() must be called later to clean up. | |
316 | * | |
317 | * Return: 0 on success, -errno on failure | |
318 | */ | |
0b81d077 JK |
319 | int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, |
320 | int lookup, struct fscrypt_name *fname) | |
6b3bd08f | 321 | { |
17159420 EB |
322 | int ret; |
323 | int digested; | |
6b3bd08f | 324 | |
0b81d077 | 325 | memset(fname, 0, sizeof(struct fscrypt_name)); |
6b3bd08f JK |
326 | fname->usr_fname = iname; |
327 | ||
e0428a26 | 328 | if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) { |
6b3bd08f JK |
329 | fname->disk_name.name = (unsigned char *)iname->name; |
330 | fname->disk_name.len = iname->len; | |
7bf4b557 | 331 | return 0; |
6b3bd08f | 332 | } |
1b53cf98 | 333 | ret = fscrypt_get_encryption_info(dir); |
17bfde60 | 334 | if (ret) |
6b3bd08f | 335 | return ret; |
0b81d077 JK |
336 | |
337 | if (dir->i_crypt_info) { | |
b9db0b4a | 338 | if (!fscrypt_fname_encrypted_size(dir, iname->len, |
e12ee683 | 339 | dir->i_sb->s_cop->max_namelen, |
b9db0b4a | 340 | &fname->crypto_buf.len)) |
50c961de | 341 | return -ENAMETOOLONG; |
50c961de EB |
342 | fname->crypto_buf.name = kmalloc(fname->crypto_buf.len, |
343 | GFP_NOFS); | |
344 | if (!fname->crypto_buf.name) | |
345 | return -ENOMEM; | |
346 | ||
347 | ret = fname_encrypt(dir, iname, fname->crypto_buf.name, | |
348 | fname->crypto_buf.len); | |
ef1eb3aa | 349 | if (ret) |
e5e0906b | 350 | goto errout; |
6b3bd08f JK |
351 | fname->disk_name.name = fname->crypto_buf.name; |
352 | fname->disk_name.len = fname->crypto_buf.len; | |
7bf4b557 | 353 | return 0; |
6b3bd08f | 354 | } |
e5e0906b | 355 | if (!lookup) |
54475f53 | 356 | return -ENOKEY; |
6b3bd08f | 357 | |
0b81d077 JK |
358 | /* |
359 | * We don't have the key and we are doing a lookup; decode the | |
6b3bd08f JK |
360 | * user-supplied name |
361 | */ | |
17159420 EB |
362 | if (iname->name[0] == '_') { |
363 | if (iname->len != | |
364 | 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name))) | |
365 | return -ENOENT; | |
366 | digested = 1; | |
367 | } else { | |
368 | if (iname->len > | |
369 | BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)) | |
370 | return -ENOENT; | |
371 | digested = 0; | |
372 | } | |
e5e0906b | 373 | |
17159420 EB |
374 | fname->crypto_buf.name = |
375 | kmalloc(max_t(size_t, FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE, | |
376 | sizeof(struct fscrypt_digested_name)), | |
377 | GFP_KERNEL); | |
e5e0906b JK |
378 | if (fname->crypto_buf.name == NULL) |
379 | return -ENOMEM; | |
0b81d077 | 380 | |
17159420 | 381 | ret = digest_decode(iname->name + digested, iname->len - digested, |
6b3bd08f JK |
382 | fname->crypto_buf.name); |
383 | if (ret < 0) { | |
384 | ret = -ENOENT; | |
e5e0906b | 385 | goto errout; |
6b3bd08f JK |
386 | } |
387 | fname->crypto_buf.len = ret; | |
17159420 EB |
388 | if (digested) { |
389 | const struct fscrypt_digested_name *n = | |
390 | (const void *)fname->crypto_buf.name; | |
391 | fname->hash = n->hash; | |
392 | fname->minor_hash = n->minor_hash; | |
6b3bd08f JK |
393 | } else { |
394 | fname->disk_name.name = fname->crypto_buf.name; | |
395 | fname->disk_name.len = fname->crypto_buf.len; | |
396 | } | |
7bf4b557 | 397 | return 0; |
0b81d077 | 398 | |
e5e0906b | 399 | errout: |
50c961de | 400 | kfree(fname->crypto_buf.name); |
6b3bd08f JK |
401 | return ret; |
402 | } | |
0b81d077 | 403 | EXPORT_SYMBOL(fscrypt_setup_filename); |