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/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
package com.wireguard.crypto;
/**
* This is a specialized constant-time base64 implementation that resists side-channel attacks.
*/
public class KeyEncoding {
public static final int KEY_LENGTH = 32;
public static final int KEY_LENGTH_BASE64 = 44;
private static final String KEY_LENGTH_BASE64_EXCEPTION_MESSAGE =
"WireGuard base64 keys must be 44 characters encoding 32 bytes";
private static int decodeBase64(final char[] src, final int src_offset) {
int val = 0;
for (int i = 0; i < 4; ++i) {
final char c = src[i + src_offset];
val |= (-1
+ ((((('A' - 1) - c) & (c - ('Z' + 1))) >>> 8) & (c - 64))
+ ((((('a' - 1) - c) & (c - ('z' + 1))) >>> 8) & (c - 70))
+ ((((('0' - 1) - c) & (c - ('9' + 1))) >>> 8) & (c + 5))
+ ((((('+' - 1) - c) & (c - ('+' + 1))) >>> 8) & 63)
+ ((((('/' - 1) - c) & (c - ('/' + 1))) >>> 8) & 64)
) << (18 - 6 * i);
}
return val;
}
private static void encodeBase64(final byte[] src, final int src_offset,
final char[] dest, final int dest_offset) {
final byte[] input = {
(byte) ((src[src_offset] >>> 2) & 63),
(byte) ((src[src_offset] << 4 | ((src[1 + src_offset] & 0xff) >>> 4)) & 63),
(byte) ((src[1 + src_offset] << 2 | ((src[2 + src_offset] & 0xff) >>> 6)) & 63),
(byte) ((src[2 + src_offset]) & 63),
};
for (int i = 0; i < 4; ++i) {
dest[i + dest_offset] = (char) (input[i] + 'A'
+ (((25 - input[i]) >>> 8) & 6)
- (((51 - input[i]) >>> 8) & 75)
- (((61 - input[i]) >>> 8) & 15)
+ (((62 - input[i]) >>> 8) & 3));
}
}
public static byte[] keyFromBase64(final String str) {
final char[] input = str.toCharArray();
final byte[] key = new byte[KEY_LENGTH];
if (input.length != KEY_LENGTH_BASE64 || input[KEY_LENGTH_BASE64 - 1] != '=')
throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
int i;
for (i = 0; i < KEY_LENGTH / 3; ++i) {
final int val = decodeBase64(input, i * 4);
if (val < 0)
throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
key[i * 3] = (byte) ((val >>> 16) & 0xff);
key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
key[i * 3 + 2] = (byte) (val & 0xff);
}
final char[] endSegment = {
input[i * 4],
input[i * 4 + 1],
input[i * 4 + 2],
'A',
};
final int val = decodeBase64(endSegment, 0);
if (val < 0 || (val & 0xff) != 0)
throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
key[i * 3] = (byte) ((val >>> 16) & 0xff);
key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
return key;
}
public static String keyToBase64(final byte[] key) {
final char[] output = new char[KEY_LENGTH_BASE64];
if (key.length != KEY_LENGTH)
throw new IllegalArgumentException("WireGuard keys must be 32 bytes");
int i;
for (i = 0; i < KEY_LENGTH / 3; ++i)
encodeBase64(key, i * 3, output, i * 4);
final byte[] endSegment = {
key[i * 3],
key[i * 3 + 1],
0,
};
encodeBase64(endSegment, 0, output, i * 4);
output[KEY_LENGTH_BASE64 - 1] = '=';
return new String(output);
}
}
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