lib/base64: RFC4648-compliant base64 encoding

Add RFC4648-compliant base64 encoding and decoding routines, based on
the base64url encoding in fs/crypto/fname.c.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Hannes Reinecke 2022-06-27 11:51:59 +02:00 committed by Jens Axboe
parent 9e2f284e14
commit a116e1cdc6
3 changed files with 120 additions and 1 deletions

16
include/linux/base64.h Normal file
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@ -0,0 +1,16 @@
// SPDX-License-Identifier: GPL-2.0
/*
* base64 encoding, lifted from fs/crypto/fname.c.
*/
#ifndef _LINUX_BASE64_H
#define _LINUX_BASE64_H
#include <linux/types.h>
#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);
#endif /* _LINUX_BASE64_H */

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@ -46,7 +46,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \ bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
list_sort.o uuid.o iov_iter.o clz_ctz.o \ list_sort.o uuid.o iov_iter.o clz_ctz.o \
bsearch.o find_bit.o llist.o memweight.o kfifo.o \ bsearch.o find_bit.o llist.o memweight.o kfifo.o \
percpu-refcount.o rhashtable.o \ percpu-refcount.o rhashtable.o base64.o \
once.o refcount.o usercopy.o errseq.o bucket_locks.o \ once.o refcount.o usercopy.o errseq.o bucket_locks.o \
generic-radix-tree.o generic-radix-tree.o
obj-$(CONFIG_STRING_SELFTEST) += test_string.o obj-$(CONFIG_STRING_SELFTEST) += test_string.o

103
lib/base64.c Normal file
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// SPDX-License-Identifier: GPL-2.0
/*
* base64.c - RFC4648-compliant base64 encoding
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/base64.h>
static const char base64_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/**
* 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.
*
* Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
* by RFC 4648, including the '='-padding.
*
* Return: the length of the resulting base64-encoded string in bytes.
*/
int base64_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++ = base64_table[(ac >> bits) & 0x3f];
} while (bits >= 6);
}
if (bits) {
*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
bits -= 6;
}
while (bits < 0) {
*cp++ = '=';
bits += 2;
}
return cp - dst;
}
EXPORT_SYMBOL_GPL(base64_encode);
/**
* 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
*
* Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
* specified by RFC 4648, including the '='-padding.
*
* 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.
*/
int base64_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(base64_table, src[i]);
if (src[i] == '=') {
ac = (ac << 6);
bits += 6;
if (bits >= 8)
bits -= 8;
continue;
}
if (p == NULL || src[i] == 0)
return -1;
ac = (ac << 6) | (p - base64_table);
bits += 6;
if (bits >= 8) {
bits -= 8;
*bp++ = (u8)(ac >> bits);
}
}
if (ac & ((1 << bits) - 1))
return -1;
return bp - dst;
}
EXPORT_SYMBOL_GPL(base64_decode);