From bf4c33325cf7c447890c90a4c1361c8bd0a5bada Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Fri, 26 Jun 2015 16:06:59 -0400
Subject: [PATCH] random non-zero padding

---
 TunnelGateway.cpp | 16 ++++++++++++++--
 TunnelGateway.h   |  6 +++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/TunnelGateway.cpp b/TunnelGateway.cpp
index cedbff10..ffbb8fe3 100644
--- a/TunnelGateway.cpp
+++ b/TunnelGateway.cpp
@@ -10,6 +10,14 @@ namespace i2p
 {
 namespace tunnel
 {
+	TunnelGatewayBuffer::TunnelGatewayBuffer (uint32_t tunnelID): m_TunnelID (tunnelID), 
+				m_CurrentTunnelDataMsg (nullptr), m_RemainingSize (0) 
+	{
+		context.GetRandomNumberGenerator ().GenerateBlock (m_NonZeroRandomBuffer, TUNNEL_DATA_MAX_PAYLOAD_SIZE);
+		for (size_t i = 0; i < TUNNEL_DATA_MAX_PAYLOAD_SIZE; i++)
+			if (!m_NonZeroRandomBuffer[i]) m_NonZeroRandomBuffer[i] = 1;
+	}
+
 	TunnelGatewayBuffer::~TunnelGatewayBuffer ()
 	{
 	}	
@@ -160,13 +168,17 @@ namespace tunnel
 		payload[-1] = 0; // zero	
 		ptrdiff_t paddingSize = payload - buf - 25; // 25  = 24 + 1 
 		if (paddingSize > 0)
-			memset (buf + 24, 1, paddingSize); // padding TODO: fill with random data
+		{
+			// non-zero padding 
+			auto randomOffset = rnd.GenerateWord32 (0, TUNNEL_DATA_MAX_PAYLOAD_SIZE - paddingSize);
+			memcpy (buf + 24, m_NonZeroRandomBuffer + randomOffset, paddingSize); 
+		}
 
 		// we can't fill message header yet because encryption is required
 		m_TunnelDataMsgs.push_back (m_CurrentTunnelDataMsg);
 		m_CurrentTunnelDataMsg = nullptr;
 	}	
-	
+
 	void TunnelGateway::SendTunnelDataMsg (const TunnelMessageBlock& block)
 	{
 		if (block.data)
diff --git a/TunnelGateway.h b/TunnelGateway.h
index cfad17b5..ea88317b 100644
--- a/TunnelGateway.h
+++ b/TunnelGateway.h
@@ -14,8 +14,7 @@ namespace tunnel
 	class TunnelGatewayBuffer
 	{
 		public:
-			TunnelGatewayBuffer (uint32_t tunnelID): m_TunnelID (tunnelID), 
-				m_CurrentTunnelDataMsg (nullptr), m_RemainingSize (0) {};
+			TunnelGatewayBuffer (uint32_t tunnelID);
 			~TunnelGatewayBuffer ();
 			void PutI2NPMsg (const TunnelMessageBlock& block);	
 			const std::vector<std::shared_ptr<I2NPMessage> >& GetTunnelDataMsgs () const { return m_TunnelDataMsgs; };
@@ -32,13 +31,14 @@ namespace tunnel
 			std::vector<std::shared_ptr<I2NPMessage> > m_TunnelDataMsgs;
 			std::shared_ptr<I2NPMessage> m_CurrentTunnelDataMsg;
 			size_t m_RemainingSize;
+			uint8_t m_NonZeroRandomBuffer[TUNNEL_DATA_MAX_PAYLOAD_SIZE];
 	};	
 
 	class TunnelGateway
 	{
 		public:
 
-			TunnelGateway (TunnelBase * tunnel): 
+			TunnelGateway (TunnelBase * tunnel):
 				m_Tunnel (tunnel), m_Buffer (tunnel->GetNextTunnelID ()), m_NumSentBytes (0) {};
 			void SendTunnelDataMsg (const TunnelMessageBlock& block);	
 			void PutTunnelDataMsg (const TunnelMessageBlock& block);