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);
141 * Old fashion base64 encoding, taken from Linux 5.4.
143 * This base64 encoding is specific to fscrypt and has been replaced since then
144 * with an RFC 4648 compliant base64-url encoding, see llcrypt_base64url_*
146 * The old fashion base64 encoding is kept for compatibility with older clients.
149 static const char lookup_table[65] =
150 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
152 #define LLCRYPT_BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
157 * Encodes the input string using characters from the set [A-Za-z0-9+,].
158 * The encoded string is roughly 4/3 times the size of the input string.
160 * Return: length of the encoded string
162 static inline int llcrypt_base64_encode(const u8 *src, int len, char *dst)
164 int i, bits = 0, ac = 0;
167 for (i = 0; i < len; i++) {
168 ac += src[i] << bits;
171 *cp++ = lookup_table[ac & 0x3f];
177 *cp++ = lookup_table[ac & 0x3f];
181 static inline int llcrypt_base64_decode(const char *src, int len, u8 *dst)
183 int i, bits = 0, ac = 0;
187 for (i = 0; i < len; i++) {
188 p = strchr(lookup_table, src[i]);
189 if (p == NULL || src[i] == 0)
191 ac += (p - lookup_table) << bits;
205 * New fashion base64 encoding, taken from Linux 5.14.
207 * This base64 encoding is RFC 4648 compliant base64-url encoding.
210 #define LLCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
213 * llcrypt_base64url_encode() - base64url-encode some binary data
214 * @src: the binary data to encode
215 * @srclen: the length of @src in bytes
216 * @dst: (output) the base64url-encoded string. Not NUL-terminated.
218 * Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL
219 * and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used,
220 * as it's unneeded and not required by the RFC. base64url is used instead of
221 * base64 to avoid the '/' character, which isn't allowed in filenames.
223 * Return: the length of the resulting base64url-encoded string in bytes.
224 * This will be equal to LLCRYPT_BASE64URL_CHARS(srclen).
226 static inline int llcrypt_base64url_encode(const u8 *src, int srclen, char *dst)
233 for (i = 0; i < srclen; i++) {
234 ac = (ac << 8) | src[i];
238 *cp++ = base64url_table[(ac >> bits) & 0x3f];
242 *cp++ = base64url_table[(ac << (6 - bits)) & 0x3f];
247 * llcrypt_base64url_decode() - base64url-decode a string
248 * @src: the string to decode. Doesn't need to be NUL-terminated.
249 * @srclen: the length of @src in bytes
250 * @dst: (output) the decoded binary data
252 * Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with
253 * URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't
254 * accepted, nor are non-encoding characters such as whitespace.
256 * This implementation hasn't been optimized for performance.
258 * Return: the length of the resulting decoded binary data in bytes,
259 * or -1 if the string isn't a valid base64url string.
261 static inline int llcrypt_base64url_decode(const char *src, int srclen, u8 *dst)
268 for (i = 0; i < srclen; i++) {
269 const char *p = strchr(base64url_table, src[i]);
271 if (p == NULL || src[i] == 0)
273 ac = (ac << 6) | (p - base64url_table);
277 *bp++ = (u8)(ac >> bits);
280 if (ac & ((1 << bits) - 1))
285 static inline int base64_chars(struct lustre_sb_info *lsi, int nbytes)
287 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
288 return LLCRYPT_BASE64URL_CHARS(nbytes);
290 return LLCRYPT_BASE64_CHARS(nbytes);
293 bool llcrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
294 u32 max_len, u32 *encrypted_len_ret)
296 const struct llcrypt_info *ci = llcrypt_info(inode);
297 struct crypto_skcipher *tfm = ci->ci_ctfm;
298 int padding = 4 << (llcrypt_policy_flags(&ci->ci_policy) &
299 LLCRYPT_POLICY_FLAGS_PAD_MASK);
302 if (orig_len > max_len)
305 *encrypted_len_ret = orig_len;
307 encrypted_len = max(orig_len, (u32)LL_CRYPTO_BLOCK_SIZE);
308 encrypted_len = round_up(encrypted_len, padding);
309 *encrypted_len_ret = min(encrypted_len, max_len);
315 * llcrypt_fname_alloc_buffer - allocate a buffer for presented filenames
317 * Allocate a buffer that is large enough to hold any decrypted or encoded
318 * filename (null-terminated), for the given maximum encrypted filename length.
320 * Return: 0 on success, -errno on failure
322 int llcrypt_fname_alloc_buffer(const struct inode *inode,
323 u32 max_encrypted_len,
324 struct llcrypt_str *crypto_str)
326 struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
327 const u32 max_encoded_len =
329 base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
330 1 + base64_chars(lsi, sizeof(struct llcrypt_digested_name)));
331 u32 max_presented_len;
333 max_presented_len = max(max_encoded_len, max_encrypted_len);
335 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
336 if (!crypto_str->name)
338 crypto_str->len = max_presented_len;
341 EXPORT_SYMBOL(llcrypt_fname_alloc_buffer);
344 * llcrypt_fname_free_buffer - free the buffer for presented filenames
346 * Free the buffer allocated by llcrypt_fname_alloc_buffer().
348 void llcrypt_fname_free_buffer(struct llcrypt_str *crypto_str)
352 kfree(crypto_str->name);
353 crypto_str->name = NULL;
355 EXPORT_SYMBOL(llcrypt_fname_free_buffer);
358 * llcrypt_fname_disk_to_usr() - converts a filename from disk space to user
361 * The caller must have allocated sufficient memory for the @oname string.
363 * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
364 * it for presentation. Short names are directly base64-encoded, while long
365 * names are encoded in llcrypt_digested_name format.
367 * Return: 0 on success, -errno on failure
369 int llcrypt_fname_disk_to_usr(struct inode *inode,
370 u32 hash, u32 minor_hash,
371 const struct llcrypt_str *iname,
372 struct llcrypt_str *oname)
374 int (*b64_encode)(const u8 *src, int srclen, char *dst);
375 struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
376 const struct qstr qname = LLTR_TO_QSTR(iname);
377 struct llcrypt_digested_name digested_name;
379 if (llcrypt_is_dot_dotdot(&qname)) {
380 oname->name[0] = '.';
381 oname->name[iname->len - 1] = '.';
382 oname->len = iname->len;
386 if (llcrypt_has_encryption_key(inode)) {
387 struct llcrypt_info *ci = llcrypt_info(inode);
388 struct crypto_skcipher *tfm = ci->ci_ctfm;
390 if (tfm && iname->len < LL_CRYPTO_BLOCK_SIZE)
393 return fname_decrypt(inode, iname, oname);
396 if (!llcrypt_policy_has_filename_enc(inode)) {
397 memcpy(oname->name, iname->name, iname->len);
398 oname->name[iname->len] = '\0';
399 oname->len = iname->len;
403 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
404 b64_encode = llcrypt_base64url_encode;
406 b64_encode = llcrypt_base64_encode;
408 if (iname->len <= LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
409 oname->len = b64_encode(iname->name, iname->len, oname->name);
413 digested_name.hash = hash;
414 digested_name.minor_hash = minor_hash;
416 digested_name.hash = 0;
417 digested_name.minor_hash = 0;
419 memcpy(digested_name.digest,
420 LLCRYPT_FNAME_DIGEST(iname->name, iname->len),
421 LLCRYPT_FNAME_DIGEST_SIZE);
422 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
423 oname->name[0] = LLCRYPT_DIGESTED_CHAR;
425 oname->name[0] = LLCRYPT_DIGESTED_CHAR_OLD;
426 oname->len = 1 + b64_encode((const u8 *)&digested_name,
427 sizeof(digested_name), oname->name + 1);
430 EXPORT_SYMBOL(llcrypt_fname_disk_to_usr);
433 * llcrypt_setup_filename() - prepare to search a possibly encrypted directory
434 * @dir: the directory that will be searched
435 * @iname: the user-provided filename being searched for
436 * @lookup: 1 if we're allowed to proceed without the key because it's
437 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
438 * proceed without the key because we're going to create the dir_entry.
439 * @fname: the filename information to be filled in
441 * Given a user-provided filename @iname, this function sets @fname->disk_name
442 * to the name that would be stored in the on-disk directory entry, if possible.
443 * If the directory is unencrypted this is simply @iname. Else, if we have the
444 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
447 * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
448 * we decode it to get either the ciphertext disk_name (for short names) or the
449 * llcrypt_digested_name (for long names). Non-@lookup operations will be
450 * impossible in this case, so we fail them with ENOKEY.
452 * If successful, llcrypt_free_filename() must be called later to clean up.
454 * Return: 0 on success, -errno on failure
456 int llcrypt_setup_filename(struct inode *dir, const struct qstr *iname,
457 int lookup, struct llcrypt_name *fname)
459 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
463 memset(fname, 0, sizeof(struct llcrypt_name));
464 fname->usr_fname = iname;
466 if (!IS_ENCRYPTED(dir) || llcrypt_is_dot_dotdot(iname)) {
467 fname->disk_name.name = (unsigned char *)iname->name;
468 fname->disk_name.len = iname->len;
471 ret = llcrypt_get_encryption_info(dir);
475 if (llcrypt_has_encryption_key(dir)) {
476 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
478 if (!llcrypt_fname_encrypted_size(dir, iname->len,
480 lsi->lsi_cop->max_namelen :
482 &fname->crypto_buf.len))
483 return -ENAMETOOLONG;
484 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
486 if (!fname->crypto_buf.name)
489 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
490 fname->crypto_buf.len);
493 fname->disk_name.name = fname->crypto_buf.name;
494 fname->disk_name.len = fname->crypto_buf.len;
500 if (!llcrypt_policy_has_filename_enc(dir)) {
501 fname->disk_name.name = (unsigned char *)iname->name;
502 fname->disk_name.len = iname->len;
506 fname->is_ciphertext_name = true;
509 * We don't have the key and we are doing a lookup; decode the
512 if ((!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
513 iname->name[0] == LLCRYPT_DIGESTED_CHAR) ||
514 ((lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
515 iname->name[0] == LLCRYPT_DIGESTED_CHAR_OLD)) {
516 if (iname->len != 1 + base64_chars(lsi,
517 sizeof(struct llcrypt_digested_name))) {
523 base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
528 fname->crypto_buf.name =
529 kmalloc(max_t(size_t, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
530 sizeof(struct llcrypt_digested_name)),
532 if (fname->crypto_buf.name == NULL)
535 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
536 ret = llcrypt_base64url_decode(iname->name + digested,
537 iname->len - digested,
538 fname->crypto_buf.name);
540 ret = llcrypt_base64_decode(iname->name + digested,
541 iname->len - digested,
542 fname->crypto_buf.name);
548 fname->crypto_buf.len = ret;
550 const struct llcrypt_digested_name *n =
551 (const void *)fname->crypto_buf.name;
552 fname->hash = n->hash;
553 fname->minor_hash = n->minor_hash;
555 fname->disk_name.name = fname->crypto_buf.name;
556 fname->disk_name.len = fname->crypto_buf.len;
561 kfree(fname->crypto_buf.name);
564 EXPORT_SYMBOL(llcrypt_setup_filename);