separate decryption between own record and other records

libi2pd/Tunnel.cpp

@@ -111,32 +111,32 @@ namespace tunnel
 		TunnelHopConfig * hop = m_Config->GetLastHop ();
 		while (hop)
 		{
-			decryption.SetKey (hop->replyKey);
-			// decrypt records before and current hop 
-			TunnelHopConfig * hop1 = hop;
-			while (hop1)
-			{
-				auto idx = hop1->recordIndex;
+			// decrypt current hop
+			auto idx = hop->recordIndex;
 			if (idx >= 0 && idx < msg[0])
 			{
 				uint8_t * record = msg + 1 + idx*TUNNEL_BUILD_RECORD_SIZE;
-					if (hop1 == hop && hop1->IsECIES ())
-					{
-						uint8_t nonce[12];
-						memset (nonce, 0, 12);
-						if (!i2p::crypto::AEADChaCha20Poly1305 (record, TUNNEL_BUILD_RECORD_SIZE - 16, 
-							hop->m_H, 32, hop->m_CK, nonce, record, TUNNEL_BUILD_RECORD_SIZE - 16, false)) // decrypt
-						{
-							LogPrint (eLogWarning, "Tunnel: Response AEAD decryption failed");
+				if (!hop->DecryptBuildResponseRecord (record, record))
 					return false;
 			}	
-					}
 			else
 			{
+				LogPrint (eLogWarning, "Tunnel: hop index ", idx, " is out of range");
+				return false;
+			}	
+			
+			// decrypt records before current hop 
+			decryption.SetKey (hop->replyKey);
+			TunnelHopConfig * hop1 = hop->prev;
+			while (hop1)
+			{
+				auto idx = hop1->recordIndex;
+				if (idx >= 0 && idx < msg[0])
+				{
+					uint8_t * record = msg + 1 + idx*TUNNEL_BUILD_RECORD_SIZE;
 					decryption.SetIV (hop->replyIV);
 					decryption.Decrypt(record, TUNNEL_BUILD_RECORD_SIZE, record);
 				}
-				}
 				else
 					LogPrint (eLogWarning, "Tunnel: hop index ", idx, " is out of range");
 				hop1 = hop1->prev;

libi2pd/TunnelConfig.cpp

@@ -147,5 +147,28 @@ namespace tunnel
 		}	
 		MixHash (encrypted, ECIES_BUILD_REQUEST_RECORD_CLEAR_TEXT_SIZE + 16); // h = SHA256(h || ciphertext)
 	}	
+
+	bool TunnelHopConfig::DecryptBuildResponseRecord (const uint8_t * encrypted, uint8_t * clearText)
+	{
+		if (IsECIES ())
+		{
+			uint8_t nonce[12];
+			memset (nonce, 0, 12);
+			if (!i2p::crypto::AEADChaCha20Poly1305 (encrypted, TUNNEL_BUILD_RECORD_SIZE - 16, 
+				m_H, 32, m_CK, nonce, clearText, TUNNEL_BUILD_RECORD_SIZE - 16, false)) // decrypt
+			{
+				LogPrint (eLogWarning, "Tunnel: Response AEAD decryption failed");
+				return false;
+			}	
+		}
+		else
+		{	
+			i2p::crypto::CBCDecryption decryption;
+			decryption.SetKey (replyKey);
+			decryption.SetIV (replyIV);
+			decryption.Decrypt (encrypted, TUNNEL_BUILD_RECORD_SIZE, clearText);
+		}	
+		return true;
+	}	
 }
 }

libi2pd/TunnelConfig.h

@@ -43,6 +43,7 @@ namespace tunnel
 		void CreateBuildRequestRecord (uint8_t * record, uint32_t replyMsgID, BN_CTX * ctx);
 		void EncryptECIES (std::shared_ptr<i2p::crypto::CryptoKeyEncryptor>& encryptor, 
 			const uint8_t * clearText, uint8_t * encrypted, BN_CTX * ctx);
+		bool DecryptBuildResponseRecord (const uint8_t * encrypted, uint8_t * clearText);
 	};
 	
 	class TunnelConfig