fill phony record for inbound tunnel with x25519 public key

libi2pd/Tunnel.cpp

@@ -29,7 +29,7 @@ namespace i2p
 {
 namespace tunnel
 {
-	Tunnel::Tunnel (std::shared_ptr<const TunnelConfig> config):
+	Tunnel::Tunnel (std::shared_ptr<TunnelConfig> config):
 		TunnelBase (config->GetTunnelID (), config->GetNextTunnelID (), config->GetNextIdentHash ()),
 		m_Config (config), m_IsShortBuildMessage (false), m_Pool (nullptr),
 		m_State (eTunnelStatePending), m_FarEndTransports (i2p::data::RouterInfo::eAllTransports),
@@ -44,7 +44,13 @@ namespace tunnel
 	void Tunnel::Build (uint32_t replyMsgID, std::shared_ptr<OutboundTunnel> outboundTunnel)
 	{
 		auto numHops = m_Config->GetNumHops ();
-		const int numRecords = numHops <= STANDARD_NUM_RECORDS ? STANDARD_NUM_RECORDS : MAX_NUM_RECORDS;
+		bool insertPhonyRecord = m_Config->IsInbound() && numHops < MAX_NUM_RECORDS;	
+		if (insertPhonyRecord) 
+		{	
+			m_Config->CreatePhonyHop ();
+			numHops++;
+		}	
+		int numRecords = numHops <= STANDARD_NUM_RECORDS ? STANDARD_NUM_RECORDS : MAX_NUM_RECORDS;
 		auto msg = numRecords <= STANDARD_NUM_RECORDS ? NewI2NPShortMessage () : NewI2NPMessage ();
 		*msg->GetPayload () = numRecords;
 		const size_t recordSize = m_Config->IsShort () ? SHORT_TUNNEL_BUILD_RECORD_SIZE : TUNNEL_BUILD_RECORD_SIZE;
@@ -52,8 +58,7 @@ namespace tunnel
 		// shuffle records
 		std::vector<int> recordIndicies;
 		for (int i = 0; i < numRecords; i++) recordIndicies.push_back(i);
-		std::shuffle (recordIndicies.begin(), recordIndicies.end(), m_Pool ? m_Pool->GetRng () : std::mt19937(std::random_device()()));
+		std::shuffle (recordIndicies.begin(), recordIndicies.end(), m_Pool ? m_Pool->GetRng () : std::mt19937(std::random_device()()));	
-
 		// create real records
 		uint8_t * records = msg->GetPayload () + 1;
 		TunnelHopConfig * hop = m_Config->GetFirstHop ();
@@ -61,7 +66,7 @@ namespace tunnel
 		while (hop)
 		{
 			uint32_t msgID;
-			if (hop->next) // we set replyMsgID for last hop only
+			if (hop->next && hop->next->ident) // we set replyMsgID for last non-phony hop only
 				RAND_bytes ((uint8_t *)&msgID, 4);
 			else
 				msgID = replyMsgID;
@@ -89,6 +94,9 @@ namespace tunnel
 			}
 			hop = hop->prev;
 		}
+		// delete phony hop after encryption
+		if (insertPhonyRecord) m_Config->DeletePhonyHop ();
+		
 		msg->FillI2NPMessageHeader (m_Config->IsShort () ? eI2NPShortTunnelBuild : eI2NPVariableTunnelBuild);
 		auto s = shared_from_this ();
 		msg->onDrop = [s]()

libi2pd/Tunnel.h

@@ -81,12 +81,12 @@ namespace tunnel
 			/** function for visiting a hops stored in a tunnel */
 			typedef std::function<void(std::shared_ptr<const i2p::data::IdentityEx>)> TunnelHopVisitor;
 
-			Tunnel (std::shared_ptr<const TunnelConfig> config);
+			Tunnel (std::shared_ptr<TunnelConfig> config);
 			~Tunnel ();
 
 			void Build (uint32_t replyMsgID, std::shared_ptr<OutboundTunnel> outboundTunnel = nullptr);
 
-			std::shared_ptr<const TunnelConfig> GetTunnelConfig () const { return m_Config; }
+			std::shared_ptr<TunnelConfig> GetTunnelConfig () const { return m_Config; }
 			std::vector<std::shared_ptr<const i2p::data::IdentityEx> > GetPeers () const;
 			std::vector<std::shared_ptr<const i2p::data::IdentityEx> > GetInvertedPeers () const;
 			bool IsShortBuildMessage () const { return m_IsShortBuildMessage; };
@@ -125,7 +125,7 @@ namespace tunnel
 
 		private:
 
-			std::shared_ptr<const TunnelConfig> m_Config;
+			std::shared_ptr<TunnelConfig> m_Config;
 			std::vector<TunnelHop> m_Hops;
 			bool m_IsShortBuildMessage;
 			std::shared_ptr<TunnelPool> m_Pool; // pool, tunnel belongs to, or null
@@ -139,7 +139,7 @@ namespace tunnel
 	{
 		public:
 
-			OutboundTunnel (std::shared_ptr<const TunnelConfig> config):
+			OutboundTunnel (std::shared_ptr<TunnelConfig> config):
 				Tunnel (config), m_Gateway (*this), m_EndpointIdentHash (config->GetLastIdentHash ()) {};
 
 			void SendTunnelDataMsgTo (const uint8_t * gwHash, uint32_t gwTunnel, std::shared_ptr<i2p::I2NPMessage> msg);
@@ -164,7 +164,7 @@ namespace tunnel
 	{
 		public:
 
-			InboundTunnel (std::shared_ptr<const TunnelConfig> config): Tunnel (config), m_Endpoint (true) {};
+			InboundTunnel (std::shared_ptr<TunnelConfig> config): Tunnel (config), m_Endpoint (true) {};
 			void HandleTunnelDataMsg (std::shared_ptr<I2NPMessage>&& msg) override;
 			virtual size_t GetNumReceivedBytes () const { return m_Endpoint.GetNumReceivedBytes (); };
 			bool IsInbound() const override { return true; }

libi2pd/TunnelConfig.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2025, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -219,6 +219,42 @@ namespace tunnel
 		return tag;
 	}
 
+	void LongPhonyTunnelHopConfig::CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID)
+	{
+		uint8_t * record = records + recordIndex*TUNNEL_BUILD_RECORD_SIZE;
+		memcpy (record + BUILD_REQUEST_RECORD_TO_PEER_OFFSET, (const uint8_t *)i2p::context.GetIdentHash (), 16);
+		memcpy (record + BUILD_REQUEST_RECORD_ENCRYPTED_OFFSET, i2p::transport::transports.GetNextX25519KeysPair ()->GetPublicKey (), 32);
+		RAND_bytes (record + 48, TUNNEL_BUILD_RECORD_SIZE - 48);
+	}
+
+	void ShortPhonyTunnelHopConfig::CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID)
+	{
+		uint8_t * record = records + recordIndex*SHORT_TUNNEL_BUILD_RECORD_SIZE;
+		memcpy (record + BUILD_REQUEST_RECORD_TO_PEER_OFFSET, (const uint8_t *)i2p::context.GetIdentHash (), 16);
+		memcpy (record + SHORT_REQUEST_RECORD_ENCRYPTED_OFFSET, i2p::transport::transports.GetNextX25519KeysPair ()->GetPublicKey (), 32);
+		RAND_bytes (record + 48, SHORT_TUNNEL_BUILD_RECORD_SIZE - 48);
+	}
+
+	TunnelConfig::TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
+		bool isShort, i2p::data::RouterInfo::CompatibleTransports farEndTransports):
+		m_IsShort (isShort), m_FarEndTransports (farEndTransports)
+	{
+		// inbound
+		CreatePeers (peers);
+		m_LastHop->SetNextIdent (i2p::context.GetIdentHash ());
+	}
+
+	TunnelConfig::TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
+		uint32_t replyTunnelID, const i2p::data::IdentHash& replyIdent, bool isShort,
+		i2p::data::RouterInfo::CompatibleTransports farEndTransports):
+		m_IsShort (isShort), m_FarEndTransports (farEndTransports)
+	{
+		// outbound
+		CreatePeers (peers);
+		m_FirstHop->isGateway = false;
+		m_LastHop->SetReplyHop (replyTunnelID, replyIdent);
+	}
+	
 	void TunnelConfig::CreatePeers (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers)
 	{
 		TunnelHopConfig * prev = nullptr;
@@ -245,5 +281,35 @@ namespace tunnel
 		}
 		m_LastHop = prev;
 	}
+
+	void TunnelConfig::CreatePhonyHop ()
+	{
+		if (m_LastHop && m_LastHop->ident)
+		{	
+			TunnelHopConfig * hop = nullptr;
+			if (m_IsShort)
+				hop = new ShortPhonyTunnelHopConfig ();
+			else
+				hop = new LongPhonyTunnelHopConfig ();
+			if (hop)
+			{	
+				hop->prev = m_LastHop;
+				m_LastHop->next = hop;
+				m_LastHop = hop;
+			}	
+		}	
+	}	
+
+	void TunnelConfig::DeletePhonyHop ()
+	{
+		if (m_LastHop && !m_LastHop->ident)
+		{
+			if (m_LastHop->prev) m_LastHop->prev->next = nullptr;
+			else m_FirstHop = nullptr;
+			auto tmp = m_LastHop;
+			m_LastHop = m_LastHop->prev;
+			delete tmp;
+		}	
+	}	
 }
 }

libi2pd/TunnelConfig.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2024, The PurpleI2P Project
+* Copyright (c) 2013-2025, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -77,28 +77,35 @@ namespace tunnel
 		uint64_t GetGarlicKey (uint8_t * key) const override;
 	};
 
+	struct PhonyTunnelHopConfig: public ECIESTunnelHopConfig
+	{
+		PhonyTunnelHopConfig (): ECIESTunnelHopConfig (nullptr) {}
+		uint8_t GetRetCode (const uint8_t * records) const override { return 0; }
+		bool DecryptBuildResponseRecord (uint8_t * records) const override { return true; }
+		void DecryptRecord (uint8_t * records, int index) const override {} // do nothing
+	};
+
+	struct LongPhonyTunnelHopConfig: public PhonyTunnelHopConfig
+	{
+		void CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID) override;
+	};	
+
+	struct ShortPhonyTunnelHopConfig: public PhonyTunnelHopConfig
+	{
+		void CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID) override;
+	};
+	
 	class TunnelConfig
 	{
 		public:
 
 			TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
-				bool isShort, i2p::data::RouterInfo::CompatibleTransports farEndTransports = i2p::data::RouterInfo::eAllTransports): // inbound
+				bool isShort, i2p::data::RouterInfo::CompatibleTransports farEndTransports = i2p::data::RouterInfo::eAllTransports); // inbound
-				m_IsShort (isShort), m_FarEndTransports (farEndTransports)
-			{
-				CreatePeers (peers);
-				m_LastHop->SetNextIdent (i2p::context.GetIdentHash ());
-			}
 
 			TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
 				uint32_t replyTunnelID, const i2p::data::IdentHash& replyIdent, bool isShort,
-				i2p::data::RouterInfo::CompatibleTransports farEndTransports = i2p::data::RouterInfo::eAllTransports): // outbound
+				i2p::data::RouterInfo::CompatibleTransports farEndTransports = i2p::data::RouterInfo::eAllTransports); // outbound
-				m_IsShort (isShort), m_FarEndTransports (farEndTransports)
+				
-			{
-				CreatePeers (peers);
-				m_FirstHop->isGateway = false;
-				m_LastHop->SetReplyHop (replyTunnelID, replyIdent);
-			}
-
 			virtual ~TunnelConfig ()
 			{
 				TunnelHopConfig * hop = m_FirstHop;
@@ -182,6 +189,9 @@ namespace tunnel
 			}
 
 			size_t GetRecordSize () const { return m_IsShort ? SHORT_TUNNEL_BUILD_RECORD_SIZE : TUNNEL_BUILD_RECORD_SIZE; };
+
+			void CreatePhonyHop ();
+			void DeletePhonyHop ();
 			
 		protected: