From 8b35ce33202591c092fc57be6f8e27eb91ead2b1 Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Fri, 2 Jul 2021 13:20:24 -0400
Subject: [PATCH] separate decryption between own record and other records

---
 libi2pd/Tunnel.cpp       | 36 ++++++++++++++++++------------------
 libi2pd/TunnelConfig.cpp | 23 +++++++++++++++++++++++
 libi2pd/TunnelConfig.h   |  1 +
 3 files changed, 42 insertions(+), 18 deletions(-)

diff --git a/libi2pd/Tunnel.cpp b/libi2pd/Tunnel.cpp
index ba01ae20..7e154cbf 100644
--- a/libi2pd/Tunnel.cpp
+++ b/libi2pd/Tunnel.cpp
@@ -111,31 +111,31 @@ namespace tunnel
 		TunnelHopConfig * hop = m_Config->GetLastHop ();
 		while (hop)
 		{
+			// decrypt current hop
+			auto idx = hop->recordIndex;
+			if (idx >= 0 && idx < msg[0])
+			{
+				uint8_t * record = msg + 1 + idx*TUNNEL_BUILD_RECORD_SIZE;
+				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);
-			// decrypt records before and current hop 
-			TunnelHopConfig * hop1 = hop;
+			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;
-					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");
-							return false;
-						}	
-					}
-					else
-					{	
-						decryption.SetIV (hop->replyIV);
-						decryption.Decrypt(record, TUNNEL_BUILD_RECORD_SIZE, record);
-					}	
+					decryption.SetIV (hop->replyIV);
+					decryption.Decrypt(record, TUNNEL_BUILD_RECORD_SIZE, record);
 				}
 				else
 					LogPrint (eLogWarning, "Tunnel: hop index ", idx, " is out of range");
diff --git a/libi2pd/TunnelConfig.cpp b/libi2pd/TunnelConfig.cpp
index 8f515c5d..9079e134 100644
--- a/libi2pd/TunnelConfig.cpp
+++ b/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;
+	}	
 }
 }
\ No newline at end of file
diff --git a/libi2pd/TunnelConfig.h b/libi2pd/TunnelConfig.h
index 45693970..548ef031 100644
--- a/libi2pd/TunnelConfig.h
+++ b/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