104 lines
2.4 KiB
C
104 lines
2.4 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* base64.c - RFC4648-compliant base64 encoding
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*
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* Copyright (c) 2020 Hannes Reinecke, SUSE
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*
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* Based on the base64url routines from fs/crypto/fname.c
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* (which are using the URL-safe base64 encoding),
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* modified to use the standard coding table from RFC4648 section 4.
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*/
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/export.h>
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#include <linux/string.h>
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#include <linux/base64.h>
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static const char base64_table[65] =
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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/**
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* base64_encode() - base64-encode some binary data
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* @src: the binary data to encode
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* @srclen: the length of @src in bytes
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* @dst: (output) the base64-encoded string. Not NUL-terminated.
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*
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* Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
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* by RFC 4648, including the '='-padding.
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*
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* Return: the length of the resulting base64-encoded string in bytes.
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*/
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int base64_encode(const u8 *src, int srclen, char *dst)
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{
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u32 ac = 0;
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int bits = 0;
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int i;
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char *cp = dst;
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for (i = 0; i < srclen; i++) {
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ac = (ac << 8) | src[i];
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bits += 8;
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do {
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bits -= 6;
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*cp++ = base64_table[(ac >> bits) & 0x3f];
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} while (bits >= 6);
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}
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if (bits) {
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*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
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bits -= 6;
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}
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while (bits < 0) {
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*cp++ = '=';
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bits += 2;
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}
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return cp - dst;
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}
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EXPORT_SYMBOL_GPL(base64_encode);
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/**
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* base64_decode() - base64-decode a string
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* @src: the string to decode. Doesn't need to be NUL-terminated.
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* @srclen: the length of @src in bytes
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* @dst: (output) the decoded binary data
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*
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* Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
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* specified by RFC 4648, including the '='-padding.
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*
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* This implementation hasn't been optimized for performance.
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*
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* Return: the length of the resulting decoded binary data in bytes,
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* or -1 if the string isn't a valid base64 string.
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*/
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int base64_decode(const char *src, int srclen, u8 *dst)
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{
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u32 ac = 0;
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int bits = 0;
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int i;
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u8 *bp = dst;
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for (i = 0; i < srclen; i++) {
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const char *p = strchr(base64_table, src[i]);
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if (src[i] == '=') {
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ac = (ac << 6);
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bits += 6;
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if (bits >= 8)
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bits -= 8;
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continue;
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}
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if (p == NULL || src[i] == 0)
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return -1;
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ac = (ac << 6) | (p - base64_table);
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bits += 6;
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if (bits >= 8) {
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bits -= 8;
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*bp++ = (u8)(ac >> bits);
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}
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}
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if (ac & ((1 << bits) - 1))
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return -1;
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return bp - dst;
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}
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EXPORT_SYMBOL_GPL(base64_decode);
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