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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
package org.bouncycastle.crypto.tls;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
import org.bouncycastle.util.Integers;
class DTLSReliableHandshake
{
private final static int MAX_RECEIVE_AHEAD = 16;
private static final int MESSAGE_HEADER_LENGTH = 12;
/*
* No 'final' modifiers so that it works in earlier JDKs
*/
private DTLSRecordLayer recordLayer;
private TlsHandshakeHash handshakeHash;
private Hashtable currentInboundFlight = new Hashtable();
private Hashtable previousInboundFlight = null;
private Vector outboundFlight = new Vector();
private boolean sending = true;
private int message_seq = 0, next_receive_seq = 0;
DTLSReliableHandshake(TlsContext context, DTLSRecordLayer transport)
{
this.recordLayer = transport;
this.handshakeHash = new DeferredHash();
this.handshakeHash.init(context);
}
void notifyHelloComplete()
{
this.handshakeHash = handshakeHash.notifyPRFDetermined();
}
TlsHandshakeHash getHandshakeHash()
{
return handshakeHash;
}
TlsHandshakeHash prepareToFinish()
{
TlsHandshakeHash result = handshakeHash;
this.handshakeHash = handshakeHash.stopTracking();
return result;
}
void sendMessage(short msg_type, byte[] body)
throws IOException
{
TlsUtils.checkUint24(body.length);
if (!sending)
{
checkInboundFlight();
sending = true;
outboundFlight.removeAllElements();
}
Message message = new Message(message_seq++, msg_type, body);
outboundFlight.addElement(message);
writeMessage(message);
updateHandshakeMessagesDigest(message);
}
byte[] receiveMessageBody(short msg_type)
throws IOException
{
Message message = receiveMessage();
if (message.getType() != msg_type)
{
throw new TlsFatalAlert(AlertDescription.unexpected_message);
}
return message.getBody();
}
Message receiveMessage()
throws IOException
{
if (sending)
{
sending = false;
prepareInboundFlight(new Hashtable());
}
byte[] buf = null;
// TODO Check the conditions under which we should reset this
int readTimeoutMillis = 1000;
for (;;)
{
try
{
for (;;)
{
if (recordLayer.isClosed())
{
throw new TlsFatalAlert(AlertDescription.user_canceled);
}
Message pending = getPendingMessage();
if (pending != null)
{
return pending;
}
int receiveLimit = recordLayer.getReceiveLimit();
if (buf == null || buf.length < receiveLimit)
{
buf = new byte[receiveLimit];
}
int received = recordLayer.receive(buf, 0, receiveLimit, readTimeoutMillis);
if (received < 0)
{
break;
}
boolean resentOutbound = processRecord(MAX_RECEIVE_AHEAD, recordLayer.getReadEpoch(), buf, 0, received);
if (resentOutbound)
{
readTimeoutMillis = backOff(readTimeoutMillis);
}
}
}
catch (IOException e)
{
// NOTE: Assume this is a timeout for the moment
}
resendOutboundFlight();
readTimeoutMillis = backOff(readTimeoutMillis);
}
}
void finish()
{
DTLSHandshakeRetransmit retransmit = null;
if (!sending)
{
checkInboundFlight();
}
else
{
prepareInboundFlight(null);
if (previousInboundFlight != null)
{
/*
* RFC 6347 4.2.4. In addition, for at least twice the default MSL defined for [TCP],
* when in the FINISHED state, the node that transmits the last flight (the server in an
* ordinary handshake or the client in a resumed handshake) MUST respond to a retransmit
* of the peer's last flight with a retransmit of the last flight.
*/
retransmit = new DTLSHandshakeRetransmit()
{
public void receivedHandshakeRecord(int epoch, byte[] buf, int off, int len)
throws IOException
{
processRecord(0, epoch, buf, off, len);
}
};
}
}
recordLayer.handshakeSuccessful(retransmit);
}
void resetHandshakeMessagesDigest()
{
handshakeHash.reset();
}
private int backOff(int timeoutMillis)
{
/*
* TODO[DTLS] implementations SHOULD back off handshake packet size during the
* retransmit backoff.
*/
return Math.min(timeoutMillis * 2, 60000);
}
/**
* Check that there are no "extra" messages left in the current inbound flight
*/
private void checkInboundFlight()
{
Enumeration e = currentInboundFlight.keys();
while (e.hasMoreElements())
{
Integer key = (Integer)e.nextElement();
if (key.intValue() >= next_receive_seq)
{
// TODO Should this be considered an error?
}
}
}
private Message getPendingMessage() throws IOException
{
DTLSReassembler next = (DTLSReassembler)currentInboundFlight.get(Integers.valueOf(next_receive_seq));
if (next != null)
{
byte[] body = next.getBodyIfComplete();
if (body != null)
{
previousInboundFlight = null;
return updateHandshakeMessagesDigest(new Message(next_receive_seq++, next.getMsgType(), body));
}
}
return null;
}
private void prepareInboundFlight(Hashtable nextFlight)
{
resetAll(currentInboundFlight);
previousInboundFlight = currentInboundFlight;
currentInboundFlight = nextFlight;
}
private boolean processRecord(int windowSize, int epoch, byte[] buf, int off, int len) throws IOException
{
boolean checkPreviousFlight = false;
while (len >= MESSAGE_HEADER_LENGTH)
{
int fragment_length = TlsUtils.readUint24(buf, off + 9);
int message_length = fragment_length + MESSAGE_HEADER_LENGTH;
if (len < message_length)
{
// NOTE: Truncated message - ignore it
break;
}
int length = TlsUtils.readUint24(buf, off + 1);
int fragment_offset = TlsUtils.readUint24(buf, off + 6);
if (fragment_offset + fragment_length > length)
{
// NOTE: Malformed fragment - ignore it and the rest of the record
break;
}
/*
* NOTE: This very simple epoch check will only work until we want to support
* renegotiation (and we're not likely to do that anyway).
*/
short msg_type = TlsUtils.readUint8(buf, off + 0);
int expectedEpoch = msg_type == HandshakeType.finished ? 1 : 0;
if (epoch != expectedEpoch)
{
break;
}
int message_seq = TlsUtils.readUint16(buf, off + 4);
if (message_seq >= (next_receive_seq + windowSize))
{
// NOTE: Too far ahead - ignore
}
else if (message_seq >= next_receive_seq)
{
DTLSReassembler reassembler = (DTLSReassembler)currentInboundFlight.get(Integers.valueOf(message_seq));
if (reassembler == null)
{
reassembler = new DTLSReassembler(msg_type, length);
currentInboundFlight.put(Integers.valueOf(message_seq), reassembler);
}
reassembler.contributeFragment(msg_type, length, buf, off + MESSAGE_HEADER_LENGTH, fragment_offset,
fragment_length);
}
else if (previousInboundFlight != null)
{
/*
* NOTE: If we receive the previous flight of incoming messages in full again,
* retransmit our last flight
*/
DTLSReassembler reassembler = (DTLSReassembler)previousInboundFlight.get(Integers.valueOf(message_seq));
if (reassembler != null)
{
reassembler.contributeFragment(msg_type, length, buf, off + MESSAGE_HEADER_LENGTH, fragment_offset,
fragment_length);
checkPreviousFlight = true;
}
}
off += message_length;
len -= message_length;
}
boolean result = checkPreviousFlight && checkAll(previousInboundFlight);
if (result)
{
resendOutboundFlight();
resetAll(previousInboundFlight);
}
return result;
}
private void resendOutboundFlight()
throws IOException
{
recordLayer.resetWriteEpoch();
for (int i = 0; i < outboundFlight.size(); ++i)
{
writeMessage((Message)outboundFlight.elementAt(i));
}
}
private Message updateHandshakeMessagesDigest(Message message)
throws IOException
{
if (message.getType() != HandshakeType.hello_request)
{
byte[] body = message.getBody();
byte[] buf = new byte[MESSAGE_HEADER_LENGTH];
TlsUtils.writeUint8(message.getType(), buf, 0);
TlsUtils.writeUint24(body.length, buf, 1);
TlsUtils.writeUint16(message.getSeq(), buf, 4);
TlsUtils.writeUint24(0, buf, 6);
TlsUtils.writeUint24(body.length, buf, 9);
handshakeHash.update(buf, 0, buf.length);
handshakeHash.update(body, 0, body.length);
}
return message;
}
private void writeMessage(Message message)
throws IOException
{
int sendLimit = recordLayer.getSendLimit();
int fragmentLimit = sendLimit - MESSAGE_HEADER_LENGTH;
// TODO Support a higher minimum fragment size?
if (fragmentLimit < 1)
{
// TODO Should we be throwing an exception here?
throw new TlsFatalAlert(AlertDescription.internal_error);
}
int length = message.getBody().length;
// NOTE: Must still send a fragment if body is empty
int fragment_offset = 0;
do
{
int fragment_length = Math.min(length - fragment_offset, fragmentLimit);
writeHandshakeFragment(message, fragment_offset, fragment_length);
fragment_offset += fragment_length;
}
while (fragment_offset < length);
}
private void writeHandshakeFragment(Message message, int fragment_offset, int fragment_length)
throws IOException
{
RecordLayerBuffer fragment = new RecordLayerBuffer(MESSAGE_HEADER_LENGTH + fragment_length);
TlsUtils.writeUint8(message.getType(), fragment);
TlsUtils.writeUint24(message.getBody().length, fragment);
TlsUtils.writeUint16(message.getSeq(), fragment);
TlsUtils.writeUint24(fragment_offset, fragment);
TlsUtils.writeUint24(fragment_length, fragment);
fragment.write(message.getBody(), fragment_offset, fragment_length);
fragment.sendToRecordLayer(recordLayer);
}
private static boolean checkAll(Hashtable inboundFlight)
{
Enumeration e = inboundFlight.elements();
while (e.hasMoreElements())
{
if (((DTLSReassembler)e.nextElement()).getBodyIfComplete() == null)
{
return false;
}
}
return true;
}
private static void resetAll(Hashtable inboundFlight)
{
Enumeration e = inboundFlight.elements();
while (e.hasMoreElements())
{
((DTLSReassembler)e.nextElement()).reset();
}
}
static class Message
{
private final int message_seq;
private final short msg_type;
private final byte[] body;
private Message(int message_seq, short msg_type, byte[] body)
{
this.message_seq = message_seq;
this.msg_type = msg_type;
this.body = body;
}
public int getSeq()
{
return message_seq;
}
public short getType()
{
return msg_type;
}
public byte[] getBody()
{
return body;
}
}
static class RecordLayerBuffer extends ByteArrayOutputStream
{
RecordLayerBuffer(int size)
{
super(size);
}
void sendToRecordLayer(DTLSRecordLayer recordLayer) throws IOException
{
recordLayer.send(buf, 0, count);
buf = null;
}
}
}
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