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/* Copyright (C) 2022 Dinglan Peng
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*/
package com.tigervnc.rdr;
import java.nio.ByteBuffer;
public class AESInStream extends InStream {
private static final int maxMessageSize = 65536;
public AESInStream(InStream _in, byte[] key)
{
in = _in;
offset = 0;
bufSize = maxMessageSize;
b = new byte[bufSize];
ptr = end = start = 0;
cipher = new AESEAXCipher(key);
messageSize = 0;
messageOffset = 0;
message = new byte[maxMessageSize + 16];
decryptedMessageOffset = 0;
decryptedMessage = new byte[maxMessageSize];
counter = new byte[16];
state = 0;
}
public final int pos()
{
return offset + ptr - start;
}
protected final int overrun(int itemSize, int nItems, boolean wait)
{
if (itemSize > bufSize)
throw new Exception("AESInStream overrun: max itemSize exceeded");
if (end - ptr != 0)
System.arraycopy(b, ptr, b, 0, end - ptr);
offset += ptr - start;
end -= ptr - start;
ptr = start;
while ((end - start) < itemSize) {
int n = readMessage(b, end, start + bufSize - end, wait);
if (!wait && n == 0)
return 0;
end += n;
}
int nAvail;
nAvail = (end - ptr) / itemSize;
if (nAvail < nItems)
return nAvail;
return nItems;
}
private int readMessage(byte[] buf, int bufPtr, int len, boolean wait)
{
if (state == 0 || state == 1) {
if (!fillDecryptedMessageBuffer(wait) && !wait)
return 0;
}
if (state == 2) {
int readSize = messageSize - decryptedMessageOffset;
if (readSize > len)
readSize = len;
System.arraycopy(decryptedMessage, decryptedMessageOffset,
buf, bufPtr, readSize);
decryptedMessageOffset += readSize;
if (decryptedMessageOffset == messageSize)
state = 0;
return readSize;
}
return 0;
}
private boolean fillDecryptedMessageBuffer(boolean wait)
{
if (state == 0) {
while (true) {
if (in.check(2, 1, wait) != 0) {
messageSize = in.readU16();
messageOffset = 0;
state = 1;
break;
} else if (!wait) {
return false;
}
}
}
if (state == 1) {
if (wait) {
in.readBytes(ByteBuffer.wrap(message, messageOffset,
messageSize + 16 - messageOffset),
messageSize + 16 - messageOffset);
} else {
while (true) {
int readSize = messageSize + 16 - messageOffset;
if (in.check(1, readSize, false) != 0) {
int availSize = in.getend() - in.getptr();
if (readSize > availSize)
readSize = availSize;
in.readBytes(ByteBuffer.wrap(message, messageOffset, readSize),
readSize);
messageOffset += readSize;
if (messageSize + 16 == messageOffset) {
break;
}
} else {
return false;
}
}
}
}
byte[] ad = new byte[] {
(byte)((messageSize & 0xff00) >> 8),
(byte)(messageSize & 0xff)
};
cipher.decrypt(message, 0, messageSize,
ad, 0, 2,
counter,
decryptedMessage, 0,
message, messageSize);
// Update nonce by incrementing the counter as a
// 128bit little endian unsigned integer
for (int i = 0; i < 16; ++i) {
// increment until there is no carry
if (++counter[i] != 0) {
break;
}
}
decryptedMessageOffset = 0;
state = 2;
return true;
}
private AESEAXCipher cipher;
private int offset;
private int start;
private int bufSize;
private int state;
private int messageSize;
private int messageOffset;
private byte[] message;
private int decryptedMessageOffset;
private byte[] decryptedMessage;
private byte[] counter;
private InStream in;
}
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