correct endianness for siphash length

libi2pd/NTCP2.cpp

@@ -522,8 +522,8 @@ namespace transport
 		m_ReceiveKey = m_Kba; 
 		m_SendSipKey = m_Sipkeysab; 
 		m_ReceiveSipKey = m_Sipkeysba;
-		memcpy (m_ReceiveIV, m_Sipkeysba + 16, 8);
+		memcpy (m_ReceiveIV.buf, m_Sipkeysba + 16, 8);
-		memcpy (m_SendIV, m_Sipkeysab + 16, 8);
+		memcpy (m_SendIV.buf, m_Sipkeysab + 16, 8);
 		Established ();
 		ReceiveLength ();
 
@@ -597,8 +597,8 @@ namespace transport
 					m_ReceiveKey = m_Kab; 
 					m_SendSipKey = m_Sipkeysba; 
 					m_ReceiveSipKey = m_Sipkeysab;
-					memcpy (m_ReceiveIV, m_Sipkeysab + 16, 8);
+					memcpy (m_ReceiveIV.buf, m_Sipkeysab + 16, 8);
-					memcpy (m_SendIV, m_Sipkeysba + 16, 8);
+					memcpy (m_SendIV.buf, m_Sipkeysba + 16, 8);
 
 					// process RI
 					if (buf[0] != eNTCP2BlkRouterInfo)
@@ -691,8 +691,9 @@ namespace transport
 		}
 		else
 		{
-			i2p::crypto::Siphash<8> (m_ReceiveIV, m_ReceiveIV, 8, m_ReceiveSipKey);
+			i2p::crypto::Siphash<8> (m_ReceiveIV.buf, m_ReceiveIV.buf, 8, m_ReceiveSipKey);
-			m_NextReceivedLen = be16toh (m_NextReceivedLen ^ bufbe16toh(m_ReceiveIV));
+			// m_NextRecivedLen comes from the network in BigEndian
+			m_NextReceivedLen = be16toh (m_NextReceivedLen) ^ m_ReceiveIV.key;
 			LogPrint (eLogDebug, "NTCP2: received length ", m_NextReceivedLen);
 			if (m_NextReceivedBuffer) delete[] m_NextReceivedBuffer;
 			m_NextReceivedBuffer = new uint8_t[m_NextReceivedLen];
@@ -803,8 +804,9 @@ namespace transport
 		CreateNonce (m_SendSequenceNumber, nonce); m_SendSequenceNumber++;
 		m_NextSendBuffer = new uint8_t[len + 16 + 2];
 		i2p::crypto::AEADChaCha20Poly1305 (payload, len, nullptr, 0, m_SendKey, nonce, m_NextSendBuffer + 2, len + 16, true);
-		i2p::crypto::Siphash<8> (m_SendIV, m_SendIV, 8, m_SendSipKey);
+		i2p::crypto::Siphash<8> (m_SendIV.buf, m_SendIV.buf, 8, m_SendSipKey);
-		htobuf16 (m_NextSendBuffer, bufbe16toh (m_SendIV) ^ htobe16(len + 16));
+		// length must be in BigEndian
+		htobe16buf (m_NextSendBuffer, (len + 16) ^ m_SendIV.key);
 		LogPrint (eLogDebug, "NTCP2: sent length ", len + 16);
 
 		// send message

libi2pd/NTCP2.h

@@ -170,7 +170,11 @@ namespace transport
 			const uint8_t * m_SendKey, * m_ReceiveKey, * m_SendSipKey, * m_ReceiveSipKey;
 			uint16_t m_NextReceivedLen; 
 			uint8_t * m_NextReceivedBuffer, * m_NextSendBuffer;
-			uint8_t m_ReceiveIV[8], m_SendIV[8];
+			union
+			{
+				uint8_t buf[8];
+				uint16_t key;
+			} m_ReceiveIV, m_SendIV;
 			uint64_t m_ReceiveSequenceNumber, m_SendSequenceNumber;
 
 			i2p::I2NPMessagesHandler m_Handler;