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 static const char base64url_table[] =
211 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
213 #define LLCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
216 * llcrypt_base64url_encode() - base64url-encode some binary data
217 * @src: the binary data to encode
218 * @srclen: the length of @src in bytes
219 * @dst: (output) the base64url-encoded string. Not NUL-terminated.
221 * Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL
222 * and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used,
223 * as it's unneeded and not required by the RFC. base64url is used instead of
224 * base64 to avoid the '/' character, which isn't allowed in filenames.
226 * Return: the length of the resulting base64url-encoded string in bytes.
227 * This will be equal to LLCRYPT_BASE64URL_CHARS(srclen).
229 static inline int llcrypt_base64url_encode(const u8 *src, int srclen, char *dst)
236 for (i = 0; i < srclen; i++) {
237 ac = (ac << 8) | src[i];
241 *cp++ = base64url_table[(ac >> bits) & 0x3f];
245 *cp++ = base64url_table[(ac << (6 - bits)) & 0x3f];
250 * llcrypt_base64url_decode() - base64url-decode a string
251 * @src: the string to decode. Doesn't need to be NUL-terminated.
252 * @srclen: the length of @src in bytes
253 * @dst: (output) the decoded binary data
255 * Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with
256 * URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't
257 * accepted, nor are non-encoding characters such as whitespace.
259 * This implementation hasn't been optimized for performance.
261 * Return: the length of the resulting decoded binary data in bytes,
262 * or -1 if the string isn't a valid base64url string.
264 static inline int llcrypt_base64url_decode(const char *src, int srclen, u8 *dst)
271 for (i = 0; i < srclen; i++) {
272 const char *p = strchr(base64url_table, src[i]);
274 if (p == NULL || src[i] == 0)
276 ac = (ac << 6) | (p - base64url_table);
280 *bp++ = (u8)(ac >> bits);
283 if (ac & ((1 << bits) - 1))
288 static inline int base64_chars(struct lustre_sb_info *lsi, int nbytes)
290 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
291 return LLCRYPT_BASE64URL_CHARS(nbytes);
293 return LLCRYPT_BASE64_CHARS(nbytes);
296 bool llcrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
297 u32 max_len, u32 *encrypted_len_ret)
299 const struct llcrypt_info *ci = llcrypt_info(inode);
300 struct crypto_skcipher *tfm = ci->ci_ctfm;
301 int padding = 4 << (llcrypt_policy_flags(&ci->ci_policy) &
302 LLCRYPT_POLICY_FLAGS_PAD_MASK);
305 if (orig_len > max_len)
308 *encrypted_len_ret = orig_len;
310 encrypted_len = max(orig_len, (u32)LL_CRYPTO_BLOCK_SIZE);
311 encrypted_len = round_up(encrypted_len, padding);
312 *encrypted_len_ret = min(encrypted_len, max_len);
318 * llcrypt_fname_alloc_buffer - allocate a buffer for presented filenames
320 * Allocate a buffer that is large enough to hold any decrypted or encoded
321 * filename (null-terminated), for the given maximum encrypted filename length.
323 * Return: 0 on success, -errno on failure
325 int llcrypt_fname_alloc_buffer(const struct inode *inode,
326 u32 max_encrypted_len,
327 struct llcrypt_str *crypto_str)
329 struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
330 const u32 max_encoded_len =
332 base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
333 1 + base64_chars(lsi, sizeof(struct llcrypt_digested_name)));
334 u32 max_presented_len;
336 max_presented_len = max(max_encoded_len, max_encrypted_len);
338 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
339 if (!crypto_str->name)
341 crypto_str->len = max_presented_len;
344 EXPORT_SYMBOL(llcrypt_fname_alloc_buffer);
347 * llcrypt_fname_free_buffer - free the buffer for presented filenames
349 * Free the buffer allocated by llcrypt_fname_alloc_buffer().
351 void llcrypt_fname_free_buffer(struct llcrypt_str *crypto_str)
355 kfree(crypto_str->name);
356 crypto_str->name = NULL;
358 EXPORT_SYMBOL(llcrypt_fname_free_buffer);
361 * llcrypt_fname_disk_to_usr() - converts a filename from disk space to user
364 * The caller must have allocated sufficient memory for the @oname string.
366 * If the key is available, we'll decrypt the disk name; otherwise, we'll encode
367 * it for presentation. Short names are directly base64-encoded, while long
368 * names are encoded in llcrypt_digested_name format.
370 * Return: 0 on success, -errno on failure
372 int llcrypt_fname_disk_to_usr(struct inode *inode,
373 u32 hash, u32 minor_hash,
374 const struct llcrypt_str *iname,
375 struct llcrypt_str *oname)
377 int (*b64_encode)(const u8 *src, int srclen, char *dst);
378 struct lustre_sb_info *lsi = s2lsi(inode->i_sb);
379 const struct qstr qname = LLTR_TO_QSTR(iname);
380 struct llcrypt_digested_name digested_name;
382 if (llcrypt_is_dot_dotdot(&qname)) {
383 oname->name[0] = '.';
384 oname->name[iname->len - 1] = '.';
385 oname->len = iname->len;
389 if (llcrypt_has_encryption_key(inode)) {
390 struct llcrypt_info *ci = llcrypt_info(inode);
391 struct crypto_skcipher *tfm = ci->ci_ctfm;
393 if (tfm && iname->len < LL_CRYPTO_BLOCK_SIZE)
396 return fname_decrypt(inode, iname, oname);
399 if (!llcrypt_policy_has_filename_enc(inode)) {
400 memcpy(oname->name, iname->name, iname->len);
401 oname->name[iname->len] = '\0';
402 oname->len = iname->len;
406 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
407 b64_encode = llcrypt_base64url_encode;
409 b64_encode = llcrypt_base64_encode;
411 if (iname->len <= LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
412 oname->len = b64_encode(iname->name, iname->len, oname->name);
416 digested_name.hash = hash;
417 digested_name.minor_hash = minor_hash;
419 digested_name.hash = 0;
420 digested_name.minor_hash = 0;
422 memcpy(digested_name.digest,
423 LLCRYPT_FNAME_DIGEST(iname->name, iname->len),
424 LLCRYPT_FNAME_DIGEST_SIZE);
425 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
426 oname->name[0] = LLCRYPT_DIGESTED_CHAR;
428 oname->name[0] = LLCRYPT_DIGESTED_CHAR_OLD;
429 oname->len = 1 + b64_encode((const u8 *)&digested_name,
430 sizeof(digested_name), oname->name + 1);
433 EXPORT_SYMBOL(llcrypt_fname_disk_to_usr);
436 * llcrypt_setup_filename() - prepare to search a possibly encrypted directory
437 * @dir: the directory that will be searched
438 * @iname: the user-provided filename being searched for
439 * @lookup: 1 if we're allowed to proceed without the key because it's
440 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot
441 * proceed without the key because we're going to create the dir_entry.
442 * @fname: the filename information to be filled in
444 * Given a user-provided filename @iname, this function sets @fname->disk_name
445 * to the name that would be stored in the on-disk directory entry, if possible.
446 * If the directory is unencrypted this is simply @iname. Else, if we have the
447 * directory's encryption key, then @iname is the plaintext, so we encrypt it to
450 * Else, for keyless @lookup operations, @iname is the presented ciphertext, so
451 * we decode it to get either the ciphertext disk_name (for short names) or the
452 * llcrypt_digested_name (for long names). Non-@lookup operations will be
453 * impossible in this case, so we fail them with ENOKEY.
455 * If successful, llcrypt_free_filename() must be called later to clean up.
457 * Return: 0 on success, -errno on failure
459 int llcrypt_setup_filename(struct inode *dir, const struct qstr *iname,
460 int lookup, struct llcrypt_name *fname)
462 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
466 memset(fname, 0, sizeof(struct llcrypt_name));
467 fname->usr_fname = iname;
469 if (!IS_ENCRYPTED(dir) || llcrypt_is_dot_dotdot(iname)) {
470 fname->disk_name.name = (unsigned char *)iname->name;
471 fname->disk_name.len = iname->len;
474 ret = llcrypt_get_encryption_info(dir);
478 if (llcrypt_has_encryption_key(dir)) {
479 struct lustre_sb_info *lsi = s2lsi(dir->i_sb);
481 if (!llcrypt_fname_encrypted_size(dir, iname->len,
483 lsi->lsi_cop->max_namelen :
485 &fname->crypto_buf.len))
486 return -ENAMETOOLONG;
487 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
489 if (!fname->crypto_buf.name)
492 ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
493 fname->crypto_buf.len);
496 fname->disk_name.name = fname->crypto_buf.name;
497 fname->disk_name.len = fname->crypto_buf.len;
503 if (!llcrypt_policy_has_filename_enc(dir)) {
504 fname->disk_name.name = (unsigned char *)iname->name;
505 fname->disk_name.len = iname->len;
509 fname->is_ciphertext_name = true;
512 * We don't have the key and we are doing a lookup; decode the
515 if ((!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
516 iname->name[0] == LLCRYPT_DIGESTED_CHAR) ||
517 ((lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI) &&
518 iname->name[0] == LLCRYPT_DIGESTED_CHAR_OLD)) {
519 if (iname->len != 1 + base64_chars(lsi,
520 sizeof(struct llcrypt_digested_name))) {
526 base64_chars(lsi, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE))
531 fname->crypto_buf.name =
532 kmalloc(max_t(size_t, LLCRYPT_FNAME_MAX_UNDIGESTED_SIZE,
533 sizeof(struct llcrypt_digested_name)),
535 if (fname->crypto_buf.name == NULL)
538 if (!(lsi->lsi_flags & LSI_FILENAME_ENC_B64_OLD_CLI))
539 ret = llcrypt_base64url_decode(iname->name + digested,
540 iname->len - digested,
541 fname->crypto_buf.name);
543 ret = llcrypt_base64_decode(iname->name + digested,
544 iname->len - digested,
545 fname->crypto_buf.name);
551 fname->crypto_buf.len = ret;
553 const struct llcrypt_digested_name *n =
554 (const void *)fname->crypto_buf.name;
555 fname->hash = n->hash;
556 fname->minor_hash = n->minor_hash;
558 fname->disk_name.name = fname->crypto_buf.name;
559 fname->disk_name.len = fname->crypto_buf.len;
564 kfree(fname->crypto_buf.name);
567 EXPORT_SYMBOL(llcrypt_setup_filename);