KDF and encryption for SessionRequest

libi2pd/SSU2.cpp

@@ -15,7 +15,8 @@ namespace transport
 {
 	SSU2Session::SSU2Session (std::shared_ptr<const i2p::data::RouterInfo> in_RemoteRouter,
 		std::shared_ptr<const i2p::data::RouterInfo::Address> addr, bool peerTest):
-		TransportSession (in_RemoteRouter, SSU2_TERMINATION_TIMEOUT)
+		TransportSession (in_RemoteRouter, SSU2_TERMINATION_TIMEOUT),
+		m_Address (addr)
 	{
 		m_NoiseState.reset (new i2p::crypto::NoiseSymmetricState);
 		if (in_RemoteRouter && addr)
@@ -28,5 +29,38 @@ namespace transport
 	SSU2Session::~SSU2Session ()
 	{	
 	}
+
+	void SSU2Session::SendSessionRequest ()
+	{
+		m_EphemeralKeys = i2p::transport::transports.GetNextX25519KeysPair ();
+		m_NoiseState->MixHash (m_EphemeralKeys->GetPublicKey (), 32);
+		uint8_t sharedSecret[32];
+		m_EphemeralKeys->Agree (m_Address->s, sharedSecret);
+		m_NoiseState->MixKey (sharedSecret);
+		
+		uint8_t packet[1200]; // TODO: correct packet size
+		size_t packetSize = 64;
+		// fill packet
+		memcpy (packet + 32, m_EphemeralKeys->GetPublicKey (), 32); // X
+		// encrypt
+		CreateHeaderMask (m_Address->i, packet + (packetSize - 24), m_Address->i, packet + (packetSize - 12));
+		EncryptHeader (*(i2p::crypto::ChipherBlock *)packet);
+		uint8_t nonce[12] = {0};
+		i2p::crypto::ChaCha20 (packet + 16, 48, m_Address->i, nonce, packet + 16);
+		i2p::crypto::AEADChaCha20Poly1305 (packet + 64, packetSize - 64, m_NoiseState->m_H, 32, m_NoiseState->m_CK, nonce, packet + 64, packetSize - 48, true);
+	}	
+
+	void SSU2Session::EncryptHeader (i2p::crypto::ChipherBlock& header)
+	{
+		header ^= m_HeaderMask;
+	}	
+
+	void SSU2Session::CreateHeaderMask (const uint8_t * kh1, const uint8_t * nonce1, const uint8_t * kh2, const uint8_t * nonce2)
+	{
+		// Header Encryption KDF
+		uint8_t data[8] = {0};
+		i2p::crypto::ChaCha20 (data, 8, kh1, nonce1, m_HeaderMask.buf);
+		i2p::crypto::ChaCha20 (data, 8, kh2, nonce2, m_HeaderMask.buf + 8);
+	}	
 }
 }

libi2pd/SSU2.h

@@ -28,10 +28,19 @@ namespace transport
 				std::shared_ptr<const i2p::data::RouterInfo::Address> addr = nullptr, bool peerTest = false);
 			~SSU2Session ();
 
+		private:
+
+			void SendSessionRequest ();
+			void EncryptHeader (i2p::crypto::ChipherBlock& header);
+			void CreateHeaderMask (const uint8_t * kh1, const uint8_t * nonce1, const uint8_t * kh2, const uint8_t * nonce2);
+		
 		private:
 
 			std::shared_ptr<i2p::crypto::X25519Keys> m_EphemeralKeys;
 			std::unique_ptr<i2p::crypto::NoiseSymmetricState> m_NoiseState;
+			std::shared_ptr<const i2p::data::RouterInfo::Address> m_Address;
+
+			i2p::crypto::ChipherBlock m_HeaderMask;
 	};
 }
 }