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// SPDX-License-Identifier: GPL-2.0
/*
* 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 support multiple Base64 variants.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/base64.h>
static const char base64_tables[][65] = {
[BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
[BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
[BASE64_IMAP] = "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.
* @padding: whether to append '=' padding characters
* @variant: which base64 variant to use
*
* Encodes data using the selected Base64 variant.
*
* Return: the length of the resulting Base64-encoded string in bytes.
*/
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];
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;
}
if (padding) {
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
* @padding: whether to append '=' padding characters
* @variant: which base64 variant to use
*
* 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.
*/
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 (padding) {
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);
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