public BufLen GetPayload()
{
if (!AllFragmentsFound)
{
throw new Exception("Cannot reassemble payload without all the fragments!");
}
var messagesize = Fragments.Sum(f => f.Data.Length);
const int h5inh16offset = 11;
var result = new BufLen(new byte[h5inh16offset + messagesize]);
var writer = new BufRefLen(result, h5inh16offset);
foreach (var onef in Fragments)
{
writer.Write(onef.Data);
}
// Fake a I2NP16 header
var exp = new I2PDate(SSUHost.SSUDateTime(result.PeekFlip32(1 + h5inh16offset)));
result[0] = result[h5inh16offset];
result.PokeFlip64((ulong)exp, 5);
result.PokeFlip16((ushort)(messagesize - 5), 13);
// Not wasting time on faking checksum
return(result);
}
public virtual SSUState DatagramReceived(BufRefLen recv, IPEndPoint RemoteEP)
{
// Verify the MAC
var reader = new BufRefLen(recv);
var header = new SSUHeader(reader);
var recvencr = header.EncryptedBuf;
var macstate = VerifyMAC(header, CurrentMACKey);
switch (macstate)
{
case MACHealth.AbandonSession:
Logging.LogTransport($"SSU {this}: Abandoning session. MAC check failed.");
SendSessionDestroyed();
Session.Host.ReportEPProblem(RemoteEP);
return(null);
case MACHealth.Missmatch:
return(this);
}
// Decrypt
Cipher.Init(false, CurrentPayloadKey.ToParametersWithIV(header.IV));
Cipher.ProcessBytes(recvencr);
header.SkipExtendedHeaders(reader);
if (header.MessageType == SSUHeader.MessageTypes.SessionDestroyed &&
CurrentPayloadKey != Session.RemoteIntroKey &&
CurrentPayloadKey != Session.MyRouterContext.IntroKey)
{
Logging.LogTransport($"SSU {this}: Received SessionDestroyed.");
SendSessionDestroyed();
return(null);
}
Logging.LogDebugData($"SSU {this}: Received message: {header.MessageType}" +
$": {SSUHost.SSUDateTime( header.TimeStamp )}");
DataReceived();
return(HandleMessage(header, reader));
}
public override SSUState HandleMessage(SSUHeader header, BufRefLen reader)
{
var tstime = SSUHost.SSUDateTime(header.TimeStamp);
if (header.MessageType != SSUHeader.MessageTypes.SessionCreated)
{
Logging.LogTransport($"SSU SessionRequestState: Received unexpected message {tstime} : {header.Flag}");
return(this);
}
SCMessage = new SessionCreated(reader, Session.RemoteRouter.Certificate);
Session.RelayTag = SCMessage.RelayTag;
Y = new I2PPublicKey((BufRefLen)SCMessage.Y, Session.RemoteRouter.Certificate);
BufUtils.DHI2PToSessionAndMAC(out var sessionkey, out var mackey,
Y.ToBigInteger().ModPow(PrivateKey.ToBigInteger(), I2PConstants.ElGamalP));
Session.SharedKey = sessionkey;
Session.MACKey = mackey;
var ipaddr = new IPAddress(SCMessage.Address.ToByteArray());
ushort port = SCMessage.Port.PeekFlip16(0);
Session.SignOnTimeB = SCMessage.SignOnTime.Peek32(0);
var btime = SSUHost.SSUDateTime(BufUtils.Flip32(Session.SignOnTimeB));
Logging.LogTransport($"SSU SessionRequestState {Session.DebugId} : Received SessionCreated. {tstime.ToString()} : {btime}");
Session.Host.ReportedAddress(ipaddr);
if (!I2PSignature.SupportedSignatureType(Session.RemoteRouter.Certificate.SignatureType))
{
throw new SignatureCheckFailureException($"SSU SessionRequestState {Session.DebugId} : " +
$"Received non supported signature type: " +
$"{Session.RemoteRouter.Certificate.SignatureType}");
}
var cipher = new CbcBlockCipher(new AesEngine());
cipher.Init(false, Session.SharedKey.ToParametersWithIV(header.IV));
cipher.ProcessBytes(SCMessage.SignatureEncrBuf);
var baddr = new BufLen(Session.RemoteEP.Address.GetAddressBytes());
var sign = new I2PSignature((BufRefLen)SCMessage.Signature, Session.RemoteRouter.Certificate);
var sok = I2PSignature.DoVerify(
Session.RemoteRouter.SigningPublicKey, sign,
X.Key, Y.Key,
SCMessage.Address, SCMessage.Port,
baddr, BufUtils.Flip16BL((ushort)Session.RemoteEP.Port),
SCMessage.RelayTag, SCMessage.SignOnTime);
Logging.LogTransport($"SSU SessionRequestState: Signature check: {sok}. {Session.RemoteRouter.Certificate.SignatureType}");
if (!sok)
{
throw new SignatureCheckFailureException($"SSU SessionRequestState {Session.DebugId}: Received SessionCreated signature check failed." +
Session.RemoteRouter.Certificate.ToString());
}
if (!RemoteIsFirewalled)
{
var relaytag = SCMessage.RelayTag.PeekFlip32(0);
if (relaytag != 0)
{
Session.RemoteIntroducerInfo = new IntroducerInfo(
Session.RemoteEP.Address,
(ushort)Session.RemoteEP.Port,
Session.RemoteIntroKey, relaytag);
Session.Host.IntroductionRelayOffered(Session.RemoteIntroducerInfo);
}
}
Logging.LogTransport($"SSU {this}: SessionCreated received " +
$"from {Session.RemoteEP} created. Moving to SessionConfirmedState.");
Session.ReportConnectionEstablished();
return(new SessionConfirmedState(Session, this));
}
