1 // SPDX-License-Identifier: GPL-2.0
3 * This contains functions for filename crypto management
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
8 * Written by Uday Savagaonkar, 2014.
9 * Modified by Jaegeuk Kim, 2015.
11 * This has not yet undergone a rigorous security audit.
14 #include <linux/scatterlist.h>
15 #include <linux/ratelimit.h>
16 #include <crypto/skcipher.h>
17 #include "fscrypt_private.h"
19 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
21 if (str->len == 1 && str->name[0] == '.')
24 if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
31 * fname_encrypt() - encrypt a filename
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.
36 * Return: 0 on success, -errno on failure
38 int fname_encrypt(struct inode *inode, const struct qstr *iname,
39 u8 *out, unsigned int olen)
41 struct skcipher_request *req = NULL;
42 DECLARE_CRYPTO_WAIT(wait);
43 struct fscrypt_info *ci = inode->i_crypt_info;
44 struct crypto_skcipher *tfm = ci->ci_ctfm;
46 struct scatterlist sg;
50 * Copy the filename to the output buffer for encrypting in-place and
51 * pad it with the needed number of NUL bytes.
53 if (WARN_ON(olen < iname->len))
55 memcpy(out, iname->name, iname->len);
56 memset(out + iname->len, 0, olen - iname->len);
58 /* Initialize the IV */
59 fscrypt_generate_iv(&iv, 0, ci);
61 /* Set up the encryption request */
62 req = skcipher_request_alloc(tfm, GFP_NOFS);
65 skcipher_request_set_callback(req,
66 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
67 crypto_req_done, &wait);
68 sg_init_one(&sg, out, olen);
69 skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
71 /* Do the encryption */
72 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
73 skcipher_request_free(req);
75 fscrypt_err(inode->i_sb,
76 "Filename encryption failed for inode %lu: %d",
85 * fname_decrypt() - decrypt a filename
87 * The caller must have allocated sufficient memory for the @oname string.
89 * Return: 0 on success, -errno on failure
91 static int fname_decrypt(struct inode *inode,
92 const struct fscrypt_str *iname,
93 struct fscrypt_str *oname)
95 struct skcipher_request *req = NULL;
96 DECLARE_CRYPTO_WAIT(wait);
97 struct scatterlist src_sg, dst_sg;
98 struct fscrypt_info *ci = inode->i_crypt_info;
99 struct crypto_skcipher *tfm = ci->ci_ctfm;
103 /* Allocate request */
104 req = skcipher_request_alloc(tfm, GFP_NOFS);
107 skcipher_request_set_callback(req,
108 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
109 crypto_req_done, &wait);
112 fscrypt_generate_iv(&iv, 0, ci);
114 /* Create decryption request */
115 sg_init_one(&src_sg, iname->name, iname->len);
116 sg_init_one(&dst_sg, oname->name, oname->len);
117 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
118 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
119 skcipher_request_free(req);
121 fscrypt_err(inode->i_sb,
122 "Filename decryption failed for inode %lu: %d",
127 oname->len = strnlen(oname->name, iname->len);
131 static const char *lookup_table =
132 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
134 #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
139 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
140 * The encoded string is roughly 4/3 times the size of the input string.
142 static int digest_encode(const char *src, int len, char *dst)
144 int i = 0, bits = 0, ac = 0;
148 ac += (((unsigned char) src[i]) << bits);
151 *cp++ = lookup_table[ac & 0x3f];
158 *cp++ = lookup_table[ac & 0x3f];
162 static int digest_decode(const char *src, int len, char *dst)
164 int i = 0, bits = 0, ac = 0;
169 p = strchr(lookup_table, src[i]);
170 if (p == NULL || src[i] == 0)
172 ac += (p - lookup_table) << bits;
186 bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
187 u32 max_len, u32 *encrypted_len_ret)
189 int padding = 4 << (inode->i_crypt_info->ci_flags &
190 FS_POLICY_FLAGS_PAD_MASK);
193 if (orig_len > max_len)
195 encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
196 encrypted_len = round_up(encrypted_len, padding);
197 *encrypted_len_ret = min(encrypted_len, max_len);
202 * fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames
204 * Allocate a buffer that is large enough to hold any decrypted or encoded
205 * filename (null-terminated), for the given maximum encrypted filename length.
207 * Return: 0 on success, -errno on failure
209 int fscrypt_fname_alloc_buffer(const struct inode *inode,
210 u32 max_encrypted_len,
211 struct fscrypt_str *crypto_str)
213 const u32 max_encoded_len =
214 max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
215 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
216 u32 max_presented_len;
218 max_presented_len = max(max_encoded_len, max_encrypted_len);
220 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
221 if (!crypto_str->name)
223 crypto_str->len = max_presented_len;
226 EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
229 * fscrypt_fname_free_buffer - free the buffer for presented filenames
231 * Free the buffer allocated by fscrypt_fname_alloc_buffer().
233 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
237 kfree(crypto_str->name);
238 crypto_str->name = NULL;
240 EXPORT_SYMBOL(fscrypt_fname_free_buffer);
243 * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
246 * The caller must have allocated sufficient memory for the @oname string.
248 * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
249 * it for presentation. Short names are directly base64-encoded, while long
250 * names are encoded in fscrypt_digested_name format.
252 * Return: 0 on success, -errno on failure
254 int fscrypt_fname_disk_to_usr(struct inode *inode,
255 u32 hash, u32 minor_hash,
256 const struct fscrypt_str *iname,
257 struct fscrypt_str *oname)
259 const struct qstr qname = FSTR_TO_QSTR(iname);
260 struct fscrypt_digested_name digested_name;
262 if (fscrypt_is_dot_dotdot(&qname)) {
263 oname->name[0] = '.';
264 oname->name[iname->len - 1] = '.';
265 oname->len = iname->len;
269 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
272 if (fscrypt_has_encryption_key(inode))
273 return fname_decrypt(inode, iname, oname);
275 if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
276 oname->len = digest_encode(iname->name, iname->len,
281 digested_name.hash = hash;
282 digested_name.minor_hash = minor_hash;
284 digested_name.hash = 0;
285 digested_name.minor_hash = 0;
287 memcpy(digested_name.digest,
288 FSCRYPT_FNAME_DIGEST(iname->name, iname->len),
289 FSCRYPT_FNAME_DIGEST_SIZE);
290 oname->name[0] = '_';
291 oname->len = 1 + digest_encode((const char *)&digested_name,
292 sizeof(digested_name), oname->name + 1);
295 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
298 * fscrypt_setup_filename() - prepare to search a possibly encrypted directory
299 * @dir: the directory that will be searched
300 * @iname: the user-provided filename being searched for
301 * @lookup: 1 if we're allowed to proceed without the key because it's
302 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
303 * proceed without the key because we're going to create the dir_entry.
304 * @fname: the filename information to be filled in
306 * Given a user-provided filename @iname, this function sets @fname->disk_name
307 * to the name that would be stored in the on-disk directory entry, if possible.
308 * If the directory is unencrypted this is simply @iname. Else, if we have the
309 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
312 * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
313 * we decode it to get either the ciphertext disk_name (for short names) or the
314 * fscrypt_digested_name (for long names). Non-@lookup operations will be
315 * impossible in this case, so we fail them with ENOKEY.
317 * If successful, fscrypt_free_filename() must be called later to clean up.
319 * Return: 0 on success, -errno on failure
321 int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
322 int lookup, struct fscrypt_name *fname)
327 memset(fname, 0, sizeof(struct fscrypt_name));
328 fname->usr_fname = iname;
330 if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
331 fname->disk_name.name = (unsigned char *)iname->name;
332 fname->disk_name.len = iname->len;
335 ret = fscrypt_get_encryption_info(dir);
339 if (fscrypt_has_encryption_key(dir)) {
340 if (!fscrypt_fname_encrypted_size(dir, iname->len,
341 dir->i_sb->s_cop->max_namelen,
342 &fname->crypto_buf.len))
343 return -ENAMETOOLONG;
344 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
346 if (!fname->crypto_buf.name)
349 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
350 fname->crypto_buf.len);
353 fname->disk_name.name = fname->crypto_buf.name;
354 fname->disk_name.len = fname->crypto_buf.len;
359 fname->is_ciphertext_name = true;
362 * We don't have the key and we are doing a lookup; decode the
365 if (iname->name[0] == '_') {
367 1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)))
372 BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
377 fname->crypto_buf.name =
378 kmalloc(max_t(size_t, FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
379 sizeof(struct fscrypt_digested_name)),
381 if (fname->crypto_buf.name == NULL)
384 ret = digest_decode(iname->name + digested, iname->len - digested,
385 fname->crypto_buf.name);
390 fname->crypto_buf.len = ret;
392 const struct fscrypt_digested_name *n =
393 (const void *)fname->crypto_buf.name;
394 fname->hash = n->hash;
395 fname->minor_hash = n->minor_hash;
397 fname->disk_name.name = fname->crypto_buf.name;
398 fname->disk_name.len = fname->crypto_buf.len;
403 kfree(fname->crypto_buf.name);
406 EXPORT_SYMBOL(fscrypt_setup_filename);