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1// SPDX-License-Identifier: GPL-2.02/*3 * base64.c - RFC4648-compliant base64 encoding4 *5 * Copyright (c) 2020 Hannes Reinecke, SUSE6 *7 * Based on the base64url routines from fs/crypto/fname.c8 * (which are using the URL-safe base64 encoding),9 * modified to use the standard coding table from RFC4648 section 4.10 */11 12#include <linux/kernel.h>13#include <linux/types.h>14#include <linux/export.h>15#include <linux/string.h>16#include <linux/base64.h>17 18static const char base64_table[65] =19 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";20 21/**22 * base64_encode() - base64-encode some binary data23 * @src: the binary data to encode24 * @srclen: the length of @src in bytes25 * @dst: (output) the base64-encoded string. Not NUL-terminated.26 *27 * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified28 * by RFC 4648, including the '='-padding.29 *30 * Return: the length of the resulting base64-encoded string in bytes.31 */32int base64_encode(const u8 *src, int srclen, char *dst)33{34 u32 ac = 0;35 int bits = 0;36 int i;37 char *cp = dst;38 39 for (i = 0; i < srclen; i++) {40 ac = (ac << 8) | src[i];41 bits += 8;42 do {43 bits -= 6;44 *cp++ = base64_table[(ac >> bits) & 0x3f];45 } while (bits >= 6);46 }47 if (bits) {48 *cp++ = base64_table[(ac << (6 - bits)) & 0x3f];49 bits -= 6;50 }51 while (bits < 0) {52 *cp++ = '=';53 bits += 2;54 }55 return cp - dst;56}57EXPORT_SYMBOL_GPL(base64_encode);58 59/**60 * base64_decode() - base64-decode a string61 * @src: the string to decode. Doesn't need to be NUL-terminated.62 * @srclen: the length of @src in bytes63 * @dst: (output) the decoded binary data64 *65 * Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"66 * specified by RFC 4648, including the '='-padding.67 *68 * This implementation hasn't been optimized for performance.69 *70 * Return: the length of the resulting decoded binary data in bytes,71 * or -1 if the string isn't a valid base64 string.72 */73int base64_decode(const char *src, int srclen, u8 *dst)74{75 u32 ac = 0;76 int bits = 0;77 int i;78 u8 *bp = dst;79 80 for (i = 0; i < srclen; i++) {81 const char *p = strchr(base64_table, src[i]);82 83 if (src[i] == '=') {84 ac = (ac << 6);85 bits += 6;86 if (bits >= 8)87 bits -= 8;88 continue;89 }90 if (p == NULL || src[i] == 0)91 return -1;92 ac = (ac << 6) | (p - base64_table);93 bits += 6;94 if (bits >= 8) {95 bits -= 8;96 *bp++ = (u8)(ac >> bits);97 }98 }99 if (ac & ((1 << bits) - 1))100 return -1;101 return bp - dst;102}103EXPORT_SYMBOL_GPL(base64_decode);104