2 * This contains functions for filename crypto management
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
7 * Written by Uday Savagaonkar, 2014.
8 * Modified by Jaegeuk Kim, 2015.
10 * This has not yet undergone a rigorous security audit.
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>
19 static u32 size_round_up(size_t size, size_t blksize)
21 return ((size + blksize - 1) / blksize) * blksize;
25 * dir_crypt_complete() -
27 static void dir_crypt_complete(struct crypto_async_request *req, int res)
29 struct fscrypt_completion_result *ecr = req->data;
31 if (res == -EINPROGRESS)
34 complete(&ecr->completion);
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.
44 static int fname_encrypt(struct inode *inode,
45 const struct qstr *iname, struct fscrypt_str *oname)
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;
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;
59 lim = inode->i_sb->s_cop->max_namelen(inode);
60 if (iname->len <= 0 || iname->len > lim)
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;
68 if (ciphertext_len <= sizeof(buf)) {
71 alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
77 /* Allocate request */
78 req = skcipher_request_alloc(tfm, GFP_NOFS);
80 printk_ratelimited(KERN_ERR
81 "%s: crypto_request_alloc() failed\n", __func__);
85 skcipher_request_set_callback(req,
86 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
87 dir_crypt_complete, &ecr);
90 memcpy(workbuf, iname->name, iname->len);
91 if (iname->len < ciphertext_len)
92 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
95 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
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);
107 skcipher_request_free(req);
109 printk_ratelimited(KERN_ERR
110 "%s: Error (error code %d)\n", __func__, res);
112 oname->len = ciphertext_len;
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.
123 static int fname_decrypt(struct inode *inode,
124 const struct fscrypt_str *iname,
125 struct fscrypt_str *oname)
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;
133 char iv[FS_CRYPTO_BLOCK_SIZE];
136 lim = inode->i_sb->s_cop->max_namelen(inode);
137 if (iname->len <= 0 || iname->len > lim)
140 /* Allocate request */
141 req = skcipher_request_alloc(tfm, GFP_NOFS);
143 printk_ratelimited(KERN_ERR
144 "%s: crypto_request_alloc() failed\n", __func__);
147 skcipher_request_set_callback(req,
148 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
149 dir_crypt_complete, &ecr);
152 memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
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);
163 skcipher_request_free(req);
165 printk_ratelimited(KERN_ERR
166 "%s: Error (error code %d)\n", __func__, res);
170 oname->len = strnlen(oname->name, iname->len);
174 static const char *lookup_table =
175 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
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.
183 static int digest_encode(const char *src, int len, char *dst)
185 int i = 0, bits = 0, ac = 0;
189 ac += (((unsigned char) src[i]) << bits);
192 *cp++ = lookup_table[ac & 0x3f];
199 *cp++ = lookup_table[ac & 0x3f];
203 static int digest_decode(const char *src, int len, char *dst)
205 int i = 0, bits = 0, ac = 0;
210 p = strchr(lookup_table, src[i]);
211 if (p == NULL || src[i] == 0)
213 ac += (p - lookup_table) << bits;
227 u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen)
230 struct fscrypt_info *ci = inode->i_crypt_info;
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);
238 EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
241 * fscrypt_fname_crypto_alloc_obuff() -
243 * Allocates an output buffer that is sufficient for the crypto operation
244 * specified by the context and the direction.
246 int fscrypt_fname_alloc_buffer(struct inode *inode,
247 u32 ilen, struct fscrypt_str *crypto_str)
249 unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);
251 crypto_str->len = olen;
252 if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
253 olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
255 * Allocated buffer can hold one more character to null-terminate the
258 crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
259 if (!(crypto_str->name))
263 EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
266 * fscrypt_fname_crypto_free_buffer() -
268 * Frees the buffer allocated for crypto operation.
270 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
274 kfree(crypto_str->name);
275 crypto_str->name = NULL;
277 EXPORT_SYMBOL(fscrypt_fname_free_buffer);
280 * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
283 int 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)
288 const struct qstr qname = FSTR_TO_QSTR(iname);
292 if (fscrypt_is_dot_dotdot(&qname)) {
293 oname->name[0] = '.';
294 oname->name[iname->len - 1] = '.';
295 oname->len = iname->len;
299 if (iname->len < FS_CRYPTO_BLOCK_SIZE)
302 if (inode->i_crypt_info)
303 return fname_decrypt(inode, iname, oname);
305 if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
306 ret = digest_encode(iname->name, iname->len, oname->name);
311 memcpy(buf, &hash, 4);
312 memcpy(buf + 4, &minor_hash, 4);
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;
322 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
325 * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
328 int fscrypt_fname_usr_to_disk(struct inode *inode,
329 const struct qstr *iname,
330 struct fscrypt_str *oname)
332 if (fscrypt_is_dot_dotdot(iname)) {
333 oname->name[0] = '.';
334 oname->name[iname->len - 1] = '.';
335 oname->len = iname->len;
338 if (inode->i_crypt_info)
339 return fname_encrypt(inode, iname, oname);
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
347 EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
349 int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
350 int lookup, struct fscrypt_name *fname)
352 int ret = 0, bigname = 0;
354 memset(fname, 0, sizeof(struct fscrypt_name));
355 fname->usr_fname = iname;
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;
363 ret = get_crypt_info(dir);
364 if (ret && ret != -EOPNOTSUPP)
367 if (dir->i_crypt_info) {
368 ret = fscrypt_fname_alloc_buffer(dir, iname->len,
372 ret = fname_encrypt(dir, iname, &fname->crypto_buf);
375 fname->disk_name.name = fname->crypto_buf.name;
376 fname->disk_name.len = fname->crypto_buf.len;
383 * We don't have the key and we are doing a lookup; decode the
386 if (iname->name[0] == '_')
388 if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
391 fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
392 if (fname->crypto_buf.name == NULL)
395 ret = digest_decode(iname->name + bigname, iname->len - bigname,
396 fname->crypto_buf.name);
401 fname->crypto_buf.len = ret;
403 memcpy(&fname->hash, fname->crypto_buf.name, 4);
404 memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
406 fname->disk_name.name = fname->crypto_buf.name;
407 fname->disk_name.len = fname->crypto_buf.len;
412 fscrypt_fname_free_buffer(&fname->crypto_buf);
415 EXPORT_SYMBOL(fscrypt_setup_filename);
417 void fscrypt_free_filename(struct fscrypt_name *fname)
419 kfree(fname->crypto_buf.name);
420 fname->crypto_buf.name = NULL;
421 fname->usr_fname = NULL;
422 fname->disk_name.name = NULL;
424 EXPORT_SYMBOL(fscrypt_free_filename);