send SessionCreated before connection close if slock skew

libi2pd/NTCP2.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -195,8 +195,9 @@ namespace transport
 		MixHash (m3p2, m3p2Len); //h = SHA256(h || ciphertext)
 	}
 
-	bool NTCP2Establisher::ProcessSessionRequestMessage (uint16_t& paddingLen)
+	bool NTCP2Establisher::ProcessSessionRequestMessage (uint16_t& paddingLen, bool& clockSkew)
 	{
+		clockSkew = false;
 		// decrypt X
 		i2p::crypto::CBCDecryption decryption;
 		decryption.SetKey (i2p::context.GetIdentHash ());
@@ -230,10 +231,11 @@ namespace transport
 				auto ts = i2p::util::GetSecondsSinceEpoch ();
 				uint32_t tsA = bufbe32toh (options + 8);
 				if (tsA < ts - NTCP2_CLOCK_SKEW || tsA > ts + NTCP2_CLOCK_SKEW)
-				{
+				{	
 					LogPrint (eLogWarning, "NTCP2: SessionRequest time difference ", (int)(ts - tsA), " exceeds clock skew");
-					return false;
-				}
+					clockSkew = true;
+					// we send SessionCreate to let Alice know our time and then close session
+				}	
 			}
 			else
 			{
@@ -476,9 +478,16 @@ namespace transport
 		{
 			LogPrint (eLogDebug, "NTCP2: SessionRequest received ", bytes_transferred);
 			uint16_t paddingLen = 0;
-			if (m_Establisher->ProcessSessionRequestMessage (paddingLen))
+			bool clockSkew = false;
+			if (m_Establisher->ProcessSessionRequestMessage (paddingLen, clockSkew))
 			{
-				if (paddingLen > 0)
+				if (clockSkew)
+				{
+					// we don't care about padding, send SessionCreated and close session
+					SendSessionCreated (); 
+					m_Server.GetService ().post (std::bind (&NTCP2Session::Terminate, shared_from_this ()));
+				}	
+				else if (paddingLen > 0)
 				{
 					if (paddingLen <= NTCP2_SESSION_REQUEST_MAX_SIZE - 64) // session request is 287 bytes max
 					{
@@ -891,7 +900,7 @@ namespace transport
 				case eNTCP2BlkTermination:
 					if (size >= 9)
 					{
-						LogPrint (eLogDebug, "NTCP2: Rermination. reason=", (int)(frame[offset + 8]));
+						LogPrint (eLogDebug, "NTCP2: Termination. reason=", (int)(frame[offset + 8]));
 						Terminate ();
 					}
 					else

libi2pd/NTCP2.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -107,7 +107,7 @@ namespace transport
 		void CreateSessionConfirmedMessagePart1 (const uint8_t * nonce);
 		void CreateSessionConfirmedMessagePart2 (const uint8_t * nonce);
 
-		bool ProcessSessionRequestMessage (uint16_t& paddingLen);
+		bool ProcessSessionRequestMessage (uint16_t& paddingLen, bool& clockSkew);
 		bool ProcessSessionCreatedMessage (uint16_t& paddingLen);
 		bool ProcessSessionConfirmedMessagePart1 (const uint8_t * nonce);
 		bool ProcessSessionConfirmedMessagePart2 (const uint8_t * nonce, uint8_t * m3p2Buf);