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lib/base64: add support for multiple variants 

Patch series " lib/base64: add generic encoder/decoder, migrate users", v5.

This series introduces a generic Base64 encoder/decoder to the kernel
library, eliminating duplicated implementations and delivering significant
performance improvements.

The Base64 API has been extended to support multiple variants (Standard,
URL-safe, and IMAP) as defined in RFC 4648 and RFC 3501.  The API now
takes a variant parameter and an option to control padding.  As part of
this series, users are migrated to the new interface while preserving
their specific formats: fscrypt now uses BASE64_URLSAFE, Ceph uses
BASE64_IMAP, and NVMe is updated to BASE64_STD.

On the encoder side, the implementation processes input in 3-byte blocks,
mapping 24 bits directly to 4 output symbols.  This avoids bit-by-bit
streaming and reduces loop overhead, achieving about a 2.7x speedup
compared to previous implementations.

On the decoder side, replace strchr() lookups with per-variant reverse
tables and process input in 4-character groups.  Each group is mapped to
numeric values and combined into 3 bytes.  Padded and unpadded forms are
validated explicitly, rejecting invalid '=' usage and enforcing tail
rules.  This improves throughput by ~43-52x.


This patch (of 6):

Extend the base64 API to support multiple variants (standard, URL-safe,
and IMAP) as defined in RFC 4648 and RFC 3501.  The API now takes a
variant parameter and an option to control padding.  Update NVMe auth code
to use the new interface with BASE64_STD.

Link: https://lkml.kernel.org/r/20251114055829.87814-1-409411716@gms.tku.edu.tw
Link: https://lkml.kernel.org/r/20251114060045.88792-1-409411716@gms.tku.edu.tw
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Co-developed-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
Reviewed-by: David Laight <david.laight.linux@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
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
Kuan-Wei Chiu 2025-11-14 14:00:45 +08:00 committed by Andrew Morton
parent 03ef32d665
commit f1e2ca801c
3 changed files with 46 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/nvme/common/auth.c
View File

@ -178,7 +178,7 @@ struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
if (!key)
return ERR_PTR(-ENOMEM);
key_len = base64_decode(secret, allocated_len, key->key);
key_len = base64_decode(secret, allocated_len, key->key, true, BASE64_STD);
if (key_len < 0) {
pr_debug("base64 key decoding error %d\n",
key_len);
@ -663,7 +663,7 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
if (ret)
goto out_free_digest;
ret = base64_encode(digest, digest_len, enc);
ret = base64_encode(digest, digest_len, enc, true, BASE64_STD);
if (ret < hmac_len) {
ret = -ENOKEY;
goto out_free_digest;

10
include/linux/base64.h
View File

@ -8,9 +8,15 @@
#include <linux/types.h>
enum base64_variant {
BASE64_STD, /* RFC 4648 (standard) */
BASE64_URLSAFE, /* RFC 4648 (base64url) */
BASE64_IMAP, /* RFC 3501 */
};
#define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
int base64_encode(const u8 *src, int len, char *dst);
int base64_decode(const char *src, int len, u8 *dst);
int base64_encode(const u8 *src, int len, char *dst, bool padding, enum base64_variant variant);
int base64_decode(const char *src, int len, u8 *dst, bool padding, enum base64_variant variant);
#endif /* _LINUX_BASE64_H */

62
lib/base64.c
View File

@ -1,12 +1,12 @@
// SPDX-License-Identifier: GPL-2.0
/*
* base64.c - RFC4648-compliant base64 encoding
* base64.c - Base64 with support for multiple variants
*
* Copyright (c) 2020 Hannes Reinecke, SUSE
*
* Based on the base64url routines from fs/crypto/fname.c
* (which are using the URL-safe base64 encoding),
* modified to use the standard coding table from RFC4648 section 4.
* (which are using the URL-safe Base64 encoding),
* modified to support multiple Base64 variants.
*/
#include <linux/kernel.h>
@ -15,26 +15,31 @@
#include <linux/string.h>
#include <linux/base64.h>
static const char base64_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char base64_tables[][65] = {
[BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
[BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
[BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,",
};
/**
* base64_encode() - base64-encode some binary data
* base64_encode() - Base64-encode some binary data
* @src: the binary data to encode
* @srclen: the length of @src in bytes
* @dst: (output) the base64-encoded string. Not NUL-terminated.
* @dst: (output) the Base64-encoded string. Not NUL-terminated.
* @padding: whether to append '=' padding characters
* @variant: which base64 variant to use
*
* Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
* by RFC 4648, including the '='-padding.
* Encodes data using the selected Base64 variant.
*
* Return: the length of the resulting base64-encoded string in bytes.
* Return: the length of the resulting Base64-encoded string in bytes.
*/
int base64_encode(const u8 *src, int srclen, char *dst)
int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant)
{
u32 ac = 0;
int bits = 0;
int i;
char *cp = dst;
const char *base64_table = base64_tables[variant];
for (i = 0; i < srclen; i++) {
ac = (ac << 8) | src[i];
@ -48,44 +53,49 @@ int base64_encode(const u8 *src, int srclen, char *dst)
*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
bits -= 6;
}
while (bits < 0) {
*cp++ = '=';
bits += 2;
if (padding) {
while (bits < 0) {
*cp++ = '=';
bits += 2;
}
}
return cp - dst;
}
EXPORT_SYMBOL_GPL(base64_encode);
/**
* base64_decode() - base64-decode a string
* base64_decode() - Base64-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
* @padding: whether to append '=' padding characters
* @variant: which base64 variant to use
*
* Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
* specified by RFC 4648, including the '='-padding.
* Decodes a string using the selected Base64 variant.
*
* 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 base64 string.
* or -1 if the string isn't a valid Base64 string.
*/
int base64_decode(const char *src, int srclen, u8 *dst)
int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant)
{
u32 ac = 0;
int bits = 0;
int i;
u8 *bp = dst;
const char *base64_table = base64_tables[variant];
for (i = 0; i < srclen; i++) {
const char *p = strchr(base64_table, src[i]);
if (src[i] == '=') {
ac = (ac << 6);
bits += 6;
if (bits >= 8)
bits -= 8;
continue;
if (padding) {
if (src[i] == '=') {
ac = (ac << 6);
bits += 6;
if (bits >= 8)
bits -= 8;
continue;
}
}
if (p == NULL || src[i] == 0)
return -1;