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fscrypt: replace local base64url helpers with lib/base64 

Replace the base64url encoding and decoding functions in fscrypt with the
generic base64_encode() and base64_decode() helpers from lib/base64.

This removes the custom implementation in fscrypt, reduces code
duplication, and relies on the shared Base64 implementation in lib.  The
helpers preserve RFC 4648-compliant URL-safe Base64 encoding without
padding, so there are no functional changes.

This change also improves performance: encoding is about 2.7x faster and
decoding achieves 43-52x speedups compared to the previous implementation.

Link: https://lkml.kernel.org/r/20251114060221.89734-1-409411716@gms.tku.edu.tw
Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Yu-Sheng Huang <home7438072@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pull/1354/merge
Guan-Chun Wu 2025-11-14 14:02:21 +08:00 committed by Andrew Morton
parent 8b365c4f5b
commit 7794510e20
1 changed files with 6 additions and 83 deletions
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89
fs/crypto/fname.c
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@ -16,6 +16,7 @@
#include <linux/export.h>
#include <linux/namei.h>
#include <linux/scatterlist.h>
#include <linux/base64.h>
#include "fscrypt_private.h"
@ -71,7 +72,7 @@ struct fscrypt_nokey_name {
/* Encoded size of max-size no-key name */
#define FSCRYPT_NOKEY_NAME_MAX_ENCODED \
FSCRYPT_BASE64URL_CHARS(FSCRYPT_NOKEY_NAME_MAX)
BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX)
static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
{
@ -162,84 +163,6 @@ static int fname_decrypt(const struct inode *inode,
return 0;
}
static const char base64url_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
#define FSCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
/**
* fscrypt_base64url_encode() - base64url-encode some binary data
* @src: the binary data to encode
* @srclen: the length of @src in bytes
* @dst: (output) the base64url-encoded string. Not NUL-terminated.
*
* Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL
* and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used,
* as it's unneeded and not required by the RFC. base64url is used instead of
* base64 to avoid the '/' character, which isn't allowed in filenames.
*
* Return: the length of the resulting base64url-encoded string in bytes.
* This will be equal to FSCRYPT_BASE64URL_CHARS(srclen).
*/
static int fscrypt_base64url_encode(const u8 *src, int srclen, char *dst)
{
u32 ac = 0;
int bits = 0;
int i;
char *cp = dst;
for (i = 0; i < srclen; i++) {
ac = (ac << 8) | src[i];
bits += 8;
do {
bits -= 6;
*cp++ = base64url_table[(ac >> bits) & 0x3f];
} while (bits >= 6);
}
if (bits)
*cp++ = base64url_table[(ac << (6 - bits)) & 0x3f];
return cp - dst;
}
/**
* fscrypt_base64url_decode() - base64url-decode a string
* @src: the string to decode. Doesn't need to be NUL-terminated.
* @srclen: the length of @src in bytes
* @dst: (output) the decoded binary data
*
* Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with
* URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't
* accepted, nor are non-encoding characters such as whitespace.
*
* This implementation hasn't been optimized for performance.
*
* Return: the length of the resulting decoded binary data in bytes,
* or -1 if the string isn't a valid base64url string.
*/
static int fscrypt_base64url_decode(const char *src, int srclen, u8 *dst)
{
u32 ac = 0;
int bits = 0;
int i;
u8 *bp = dst;
for (i = 0; i < srclen; i++) {
const char *p = strchr(base64url_table, src[i]);
if (p == NULL || src[i] == 0)
return -1;
ac = (ac << 6) | (p - base64url_table);
bits += 6;
if (bits >= 8) {
bits -= 8;
*bp++ = (u8)(ac >> bits);
}
}
if (ac & ((1 << bits) - 1))
return -1;
return bp - dst;
}
bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
u32 orig_len, u32 max_len,
u32 *encrypted_len_ret)
@ -387,8 +310,8 @@ int fscrypt_fname_disk_to_usr(const struct inode *inode,
nokey_name.sha256);
size = FSCRYPT_NOKEY_NAME_MAX;
}
oname->len = fscrypt_base64url_encode((const u8 *)&nokey_name, size,
oname->name);
oname->len = base64_encode((const u8 *)&nokey_name, size,
oname->name, false, BASE64_URLSAFE);
return 0;
}
EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
@ -467,8 +390,8 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
ret = fscrypt_base64url_decode(iname->name, iname->len,
fname->crypto_buf.name);
ret = base64_decode(iname->name, iname->len,
fname->crypto_buf.name, false, BASE64_URLSAFE);
if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) ||
(ret > offsetof(struct fscrypt_nokey_name, sha256) &&
ret != FSCRYPT_NOKEY_NAME_MAX)) {