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 * Linux commit 219d54332a09
18 #include <linux/scatterlist.h>
19 #include <crypto/skcipher.h>
20 #include "llcrypt_private.h"
22 static inline bool llcrypt_is_dot_dotdot(const struct qstr *str)
24 if (str->len == 1 && str->name[0] == '.')
27 if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
34 * fname_encrypt() - encrypt a filename
36 * The output buffer must be at least as large as the input buffer.
37 * Any extra space is filled with NUL padding before encryption.
39 * Return: 0 on success, -errno on failure
41 int fname_encrypt(struct inode *inode, const struct qstr *iname,
42 u8 *out, unsigned int olen)
44 struct skcipher_request *req = NULL;
45 DECLARE_CRYPTO_WAIT(wait);
46 struct llcrypt_info *ci = llcrypt_info(inode);
47 struct crypto_skcipher *tfm = ci->ci_ctfm;
49 struct scatterlist sg;
53 * Copy the filename to the output buffer for encrypting in-place and
54 * pad it with the needed number of NUL bytes.
56 if (WARN_ON(olen < iname->len))
58 memcpy(out, iname->name, iname->len);
59 memset(out + iname->len, 0, olen - iname->len);
61 /* Initialize the IV */
62 llcrypt_generate_iv(&iv, 0, ci);
64 /* Set up the encryption request */
65 req = skcipher_request_alloc(tfm, GFP_NOFS);
68 skcipher_request_set_callback(req,
69 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
70 crypto_req_done, &wait);
71 sg_init_one(&sg, out, olen);
72 skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
74 /* Do the encryption */
75 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
76 skcipher_request_free(req);
78 llcrypt_err(inode, "Filename encryption failed: %d", res);
86 * fname_decrypt() - decrypt a filename
88 * The caller must have allocated sufficient memory for the @oname string.
90 * Return: 0 on success, -errno on failure
92 static int fname_decrypt(struct inode *inode,
93 const struct llcrypt_str *iname,
94 struct llcrypt_str *oname)
96 struct skcipher_request *req = NULL;
97 DECLARE_CRYPTO_WAIT(wait);
98 struct scatterlist src_sg, dst_sg;
99 struct llcrypt_info *ci = llcrypt_info(inode);
100 struct crypto_skcipher *tfm = ci->ci_ctfm;
104 /* Allocate request */
105 req = skcipher_request_alloc(tfm, GFP_NOFS);
108 skcipher_request_set_callback(req,
109 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
110 crypto_req_done, &wait);
113 llcrypt_generate_iv(&iv, 0, ci);
115 /* Create decryption request */
116 sg_init_one(&src_sg, iname->name, iname->len);
117 sg_init_one(&dst_sg, oname->name, oname->len);
118 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
119 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
120 skcipher_request_free(req);
122 llcrypt_err(inode, "Filename decryption failed: %d", res);
126 oname->len = strnlen(oname->name, iname->len);
130 static const char lookup_table[65] =
131 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
133 #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
138 * Encodes the input string using characters from the set [A-Za-z0-9+,].
139 * The encoded string is roughly 4/3 times the size of the input string.
141 * Return: length of the encoded string
143 static int base64_encode(const u8 *src, int len, char *dst)
145 int i, bits = 0, ac = 0;
148 for (i = 0; i < len; i++) {
149 ac += src[i] << bits;
152 *cp++ = lookup_table[ac & 0x3f];
158 *cp++ = lookup_table[ac & 0x3f];
162 static int base64_decode(const char *src, int len, u8 *dst)
164 int i, bits = 0, ac = 0;
168 for (i = 0; i < len; i++) {
169 p = strchr(lookup_table, src[i]);
170 if (p == NULL || src[i] == 0)
172 ac += (p - lookup_table) << bits;
185 bool llcrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
186 u32 max_len, u32 *encrypted_len_ret)
188 const struct llcrypt_info *ci = llcrypt_info(inode);
189 int padding = 4 << (llcrypt_policy_flags(&ci->ci_policy) &
190 LLCRYPT_POLICY_FLAGS_PAD_MASK);
193 if (orig_len > max_len)
195 encrypted_len = max(orig_len, (u32)LL_CRYPTO_BLOCK_SIZE);
196 encrypted_len = round_up(encrypted_len, padding);
197 *encrypted_len_ret = min(encrypted_len, max_len);
202 * llcrypt_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 llcrypt_fname_alloc_buffer(const struct inode *inode,
210 u32 max_encrypted_len,
211 struct llcrypt_str *crypto_str)
213 const u32 max_encoded_len =
214 max_t(u32, BASE64_CHARS(LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
215 1 + BASE64_CHARS(sizeof(struct llcrypt_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(llcrypt_fname_alloc_buffer);
229 * llcrypt_fname_free_buffer - free the buffer for presented filenames
231 * Free the buffer allocated by llcrypt_fname_alloc_buffer().
233 void llcrypt_fname_free_buffer(struct llcrypt_str *crypto_str)
237 kfree(crypto_str->name);
238 crypto_str->name = NULL;
240 EXPORT_SYMBOL(llcrypt_fname_free_buffer);
243 * llcrypt_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 llcrypt_digested_name format.
252 * Return: 0 on success, -errno on failure
254 int llcrypt_fname_disk_to_usr(struct inode *inode,
255 u32 hash, u32 minor_hash,
256 const struct llcrypt_str *iname,
257 struct llcrypt_str *oname)
259 const struct qstr qname = LLTR_TO_QSTR(iname);
260 struct llcrypt_digested_name digested_name;
262 if (llcrypt_is_dot_dotdot(&qname)) {
263 oname->name[0] = '.';
264 oname->name[iname->len - 1] = '.';
265 oname->len = iname->len;
269 if (iname->len < LL_CRYPTO_BLOCK_SIZE)
272 if (llcrypt_has_encryption_key(inode))
273 return fname_decrypt(inode, iname, oname);
275 if (iname->len <= LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
276 oname->len = base64_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 LLCRYPT_FNAME_DIGEST(iname->name, iname->len),
289 LLCRYPT_FNAME_DIGEST_SIZE);
290 oname->name[0] = '_';
291 oname->len = 1 + base64_encode((const u8 *)&digested_name,
292 sizeof(digested_name), oname->name + 1);
295 EXPORT_SYMBOL(llcrypt_fname_disk_to_usr);
298 * llcrypt_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 * llcrypt_digested_name (for long names). Non-@lookup operations will be
315 * impossible in this case, so we fail them with ENOKEY.
317 * If successful, llcrypt_free_filename() must be called later to clean up.
319 * Return: 0 on success, -errno on failure
321 int llcrypt_setup_filename(struct inode *dir, const struct qstr *iname,
322 int lookup, struct llcrypt_name *fname)
327 memset(fname, 0, sizeof(struct llcrypt_name));
328 fname->usr_fname = iname;
330 if (!IS_ENCRYPTED(dir) || llcrypt_is_dot_dotdot(iname)) {
331 fname->disk_name.name = (unsigned char *)iname->name;
332 fname->disk_name.len = iname->len;
335 ret = llcrypt_get_encryption_info(dir);
339 if (llcrypt_has_encryption_key(dir)) {
340 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
342 if (!llcrypt_fname_encrypted_size(dir, iname->len,
344 lsi->lsi_cop->max_namelen :
346 &fname->crypto_buf.len))
347 return -ENAMETOOLONG;
348 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
350 if (!fname->crypto_buf.name)
353 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
354 fname->crypto_buf.len);
357 fname->disk_name.name = fname->crypto_buf.name;
358 fname->disk_name.len = fname->crypto_buf.len;
363 fname->is_ciphertext_name = true;
366 * We don't have the key and we are doing a lookup; decode the
369 if (iname->name[0] == '_') {
371 1 + BASE64_CHARS(sizeof(struct llcrypt_digested_name)))
376 BASE64_CHARS(LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
381 fname->crypto_buf.name =
382 kmalloc(max_t(size_t, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
383 sizeof(struct llcrypt_digested_name)),
385 if (fname->crypto_buf.name == NULL)
388 ret = base64_decode(iname->name + digested, iname->len - digested,
389 fname->crypto_buf.name);
394 fname->crypto_buf.len = ret;
396 const struct llcrypt_digested_name *n =
397 (const void *)fname->crypto_buf.name;
398 fname->hash = n->hash;
399 fname->minor_hash = n->minor_hash;
401 fname->disk_name.name = fname->crypto_buf.name;
402 fname->disk_name.len = fname->crypto_buf.len;
407 kfree(fname->crypto_buf.name);
410 EXPORT_SYMBOL(llcrypt_setup_filename);