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using System;
using System.IO;
using Org.BouncyCastle.Tls.Crypto;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Tls
{
public class DtlsVerifier
{
private static TlsMac CreateCookieMac(TlsCrypto crypto)
{
TlsMac mac = crypto.CreateHmac(MacAlgorithm.hmac_sha256);
byte[] secret = new byte[mac.MacLength];
crypto.SecureRandom.NextBytes(secret);
mac.SetKey(secret, 0, secret.Length);
return mac;
}
private readonly TlsMac m_cookieMac;
private readonly TlsMacSink m_cookieMacSink;
public DtlsVerifier(TlsCrypto crypto)
{
this.m_cookieMac = CreateCookieMac(crypto);
this.m_cookieMacSink = new TlsMacSink(m_cookieMac);
}
public virtual DtlsRequest VerifyRequest(byte[] clientID, byte[] data, int dataOff, int dataLen,
DatagramSender sender)
{
lock (this)
{
bool resetCookieMac = true;
try
{
m_cookieMac.Update(clientID, 0, clientID.Length);
DtlsRequest request = DtlsReliableHandshake.ReadClientRequest(data, dataOff, dataLen,
m_cookieMacSink);
if (null != request)
{
byte[] expectedCookie = m_cookieMac.CalculateMac();
resetCookieMac = false;
// TODO Consider stricter HelloVerifyRequest protocol
//switch (request.MessageSeq)
//{
//case 0:
//{
// DtlsReliableHandshake.SendHelloVerifyRequest(sender, request.RecordSeq, expectedCookie);
// break;
//}
//case 1:
//{
// if (Arrays.ConstantTimeAreEqual(expectedCookie, request.ClientHello.Cookie))
// return request;
// break;
//}
//}
if (Arrays.ConstantTimeAreEqual(expectedCookie, request.ClientHello.Cookie))
return request;
DtlsReliableHandshake.SendHelloVerifyRequest(sender, request.RecordSeq, expectedCookie);
}
}
catch (IOException)
{
// Ignore
}
finally
{
if (resetCookieMac)
{
m_cookieMac.Reset();
}
}
return null;
}
}
}
}
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