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);
64 /* Initialize the IV */
65 llcrypt_generate_iv(&iv, 0, ci);
67 /* Set up the encryption request */
68 req = skcipher_request_alloc(tfm, GFP_NOFS);
71 skcipher_request_set_callback(req,
72 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
73 crypto_req_done, &wait);
74 sg_init_one(&sg, out, olen);
75 skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
77 /* Do the encryption */
78 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
79 skcipher_request_free(req);
81 llcrypt_err(inode, "Filename encryption failed: %d", res);
89 * fname_decrypt() - decrypt a filename
91 * The caller must have allocated sufficient memory for the @oname string.
93 * Return: 0 on success, -errno on failure
95 static int fname_decrypt(struct inode *inode,
96 const struct llcrypt_str *iname,
97 struct llcrypt_str *oname)
99 struct skcipher_request *req = NULL;
100 DECLARE_CRYPTO_WAIT(wait);
101 struct scatterlist src_sg, dst_sg;
102 struct llcrypt_info *ci = llcrypt_info(inode);
103 struct crypto_skcipher *tfm = ci->ci_ctfm;
108 memcpy(oname->name, iname->name, iname->len);
109 oname->name[iname->len] = '\0';
110 oname->len = iname->len;
114 /* Allocate request */
115 req = skcipher_request_alloc(tfm, GFP_NOFS);
118 skcipher_request_set_callback(req,
119 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
120 crypto_req_done, &wait);
123 llcrypt_generate_iv(&iv, 0, ci);
125 /* Create decryption request */
126 sg_init_one(&src_sg, iname->name, iname->len);
127 sg_init_one(&dst_sg, oname->name, oname->len);
128 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
129 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
130 skcipher_request_free(req);
132 llcrypt_err(inode, "Filename decryption failed: %d", res);
136 oname->len = strnlen(oname->name, iname->len);
140 static const char lookup_table[65] =
141 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
143 #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
148 * Encodes the input string using characters from the set [A-Za-z0-9+,].
149 * The encoded string is roughly 4/3 times the size of the input string.
151 * Return: length of the encoded string
153 static int base64_encode(const u8 *src, int len, char *dst)
155 int i, bits = 0, ac = 0;
158 for (i = 0; i < len; i++) {
159 ac += src[i] << bits;
162 *cp++ = lookup_table[ac & 0x3f];
168 *cp++ = lookup_table[ac & 0x3f];
172 static int base64_decode(const char *src, int len, u8 *dst)
174 int i, bits = 0, ac = 0;
178 for (i = 0; i < len; i++) {
179 p = strchr(lookup_table, src[i]);
180 if (p == NULL || src[i] == 0)
182 ac += (p - lookup_table) << bits;
195 bool llcrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
196 u32 max_len, u32 *encrypted_len_ret)
198 const struct llcrypt_info *ci = llcrypt_info(inode);
199 struct crypto_skcipher *tfm = ci->ci_ctfm;
200 int padding = 4 << (llcrypt_policy_flags(&ci->ci_policy) &
201 LLCRYPT_POLICY_FLAGS_PAD_MASK);
204 if (orig_len > max_len)
207 *encrypted_len_ret = orig_len;
209 encrypted_len = max(orig_len, (u32)LL_CRYPTO_BLOCK_SIZE);
210 encrypted_len = round_up(encrypted_len, padding);
211 *encrypted_len_ret = min(encrypted_len, max_len);
217 * llcrypt_fname_alloc_buffer - allocate a buffer for presented filenames
219 * Allocate a buffer that is large enough to hold any decrypted or encoded
220 * filename (null-terminated), for the given maximum encrypted filename length.
222 * Return: 0 on success, -errno on failure
224 int llcrypt_fname_alloc_buffer(const struct inode *inode,
225 u32 max_encrypted_len,
226 struct llcrypt_str *crypto_str)
228 const u32 max_encoded_len =
229 max_t(u32, BASE64_CHARS(LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
230 1 + BASE64_CHARS(sizeof(struct llcrypt_digested_name)));
231 u32 max_presented_len;
233 max_presented_len = max(max_encoded_len, max_encrypted_len);
235 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
236 if (!crypto_str->name)
238 crypto_str->len = max_presented_len;
241 EXPORT_SYMBOL(llcrypt_fname_alloc_buffer);
244 * llcrypt_fname_free_buffer - free the buffer for presented filenames
246 * Free the buffer allocated by llcrypt_fname_alloc_buffer().
248 void llcrypt_fname_free_buffer(struct llcrypt_str *crypto_str)
252 kfree(crypto_str->name);
253 crypto_str->name = NULL;
255 EXPORT_SYMBOL(llcrypt_fname_free_buffer);
258 * llcrypt_fname_disk_to_usr() - converts a filename from disk space to user
261 * The caller must have allocated sufficient memory for the @oname string.
263 * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
264 * it for presentation. Short names are directly base64-encoded, while long
265 * names are encoded in llcrypt_digested_name format.
267 * Return: 0 on success, -errno on failure
269 int llcrypt_fname_disk_to_usr(struct inode *inode,
270 u32 hash, u32 minor_hash,
271 const struct llcrypt_str *iname,
272 struct llcrypt_str *oname)
274 const struct qstr qname = LLTR_TO_QSTR(iname);
275 struct llcrypt_digested_name digested_name;
277 if (llcrypt_is_dot_dotdot(&qname)) {
278 oname->name[0] = '.';
279 oname->name[iname->len - 1] = '.';
280 oname->len = iname->len;
284 if (llcrypt_has_encryption_key(inode)) {
285 struct llcrypt_info *ci = llcrypt_info(inode);
286 struct crypto_skcipher *tfm = ci->ci_ctfm;
288 if (tfm && iname->len < LL_CRYPTO_BLOCK_SIZE)
291 return fname_decrypt(inode, iname, oname);
294 if (unlikely(!llcrypt_policy_has_filename_enc(inode))) {
295 memcpy(oname->name, iname->name, iname->len);
296 oname->name[iname->len] = '\0';
297 oname->len = iname->len;
301 if (iname->len <= LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
302 oname->len = base64_encode(iname->name, iname->len,
307 digested_name.hash = hash;
308 digested_name.minor_hash = minor_hash;
310 digested_name.hash = 0;
311 digested_name.minor_hash = 0;
313 memcpy(digested_name.digest,
314 LLCRYPT_FNAME_DIGEST(iname->name, iname->len),
315 LLCRYPT_FNAME_DIGEST_SIZE);
316 oname->name[0] = '_';
317 oname->len = 1 + base64_encode((const u8 *)&digested_name,
318 sizeof(digested_name), oname->name + 1);
321 EXPORT_SYMBOL(llcrypt_fname_disk_to_usr);
324 * llcrypt_setup_filename() - prepare to search a possibly encrypted directory
325 * @dir: the directory that will be searched
326 * @iname: the user-provided filename being searched for
327 * @lookup: 1 if we're allowed to proceed without the key because it's
328 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
329 * proceed without the key because we're going to create the dir_entry.
330 * @fname: the filename information to be filled in
332 * Given a user-provided filename @iname, this function sets @fname->disk_name
333 * to the name that would be stored in the on-disk directory entry, if possible.
334 * If the directory is unencrypted this is simply @iname. Else, if we have the
335 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
338 * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
339 * we decode it to get either the ciphertext disk_name (for short names) or the
340 * llcrypt_digested_name (for long names). Non-@lookup operations will be
341 * impossible in this case, so we fail them with ENOKEY.
343 * If successful, llcrypt_free_filename() must be called later to clean up.
345 * Return: 0 on success, -errno on failure
347 int llcrypt_setup_filename(struct inode *dir, const struct qstr *iname,
348 int lookup, struct llcrypt_name *fname)
353 memset(fname, 0, sizeof(struct llcrypt_name));
354 fname->usr_fname = iname;
356 if (!IS_ENCRYPTED(dir) || llcrypt_is_dot_dotdot(iname)) {
357 fname->disk_name.name = (unsigned char *)iname->name;
358 fname->disk_name.len = iname->len;
361 ret = llcrypt_get_encryption_info(dir);
365 if (llcrypt_has_encryption_key(dir)) {
366 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
368 if (!llcrypt_fname_encrypted_size(dir, iname->len,
370 lsi->lsi_cop->max_namelen :
372 &fname->crypto_buf.len))
373 return -ENAMETOOLONG;
374 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
376 if (!fname->crypto_buf.name)
379 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
380 fname->crypto_buf.len);
383 fname->disk_name.name = fname->crypto_buf.name;
384 fname->disk_name.len = fname->crypto_buf.len;
390 if (unlikely(!llcrypt_policy_has_filename_enc(dir))) {
391 fname->disk_name.name = (unsigned char *)iname->name;
392 fname->disk_name.len = iname->len;
396 fname->is_ciphertext_name = true;
399 * We don't have the key and we are doing a lookup; decode the
402 if (iname->name[0] == '_') {
404 1 + BASE64_CHARS(sizeof(struct llcrypt_digested_name)))
409 BASE64_CHARS(LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
414 fname->crypto_buf.name =
415 kmalloc(max_t(size_t, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
416 sizeof(struct llcrypt_digested_name)),
418 if (fname->crypto_buf.name == NULL)
421 ret = base64_decode(iname->name + digested, iname->len - digested,
422 fname->crypto_buf.name);
427 fname->crypto_buf.len = ret;
429 const struct llcrypt_digested_name *n =
430 (const void *)fname->crypto_buf.name;
431 fname->hash = n->hash;
432 fname->minor_hash = n->minor_hash;
434 fname->disk_name.name = fname->crypto_buf.name;
435 fname->disk_name.len = fname->crypto_buf.len;
440 kfree(fname->crypto_buf.name);
443 EXPORT_SYMBOL(llcrypt_setup_filename);