create and handle short tunnel build reply

libi2pd/Garlic.cpp

@@ -471,8 +471,13 @@ namespace garlic
 	{
 		uint64_t t;
 		memcpy (&t, tag, 8);
+		AddECIESx25519Key (key, t);
+	}	
+
+	void GarlicDestination::AddECIESx25519Key (const uint8_t * key, uint64_t tag)
+	{
 		auto tagset = std::make_shared<SymmetricKeyTagSet>(this, key);
-		m_ECIESx25519Tags.emplace (t, ECIESX25519AEADRatchetIndexTagset{0, tagset});
+		m_ECIESx25519Tags.emplace (tag, ECIESX25519AEADRatchetIndexTagset{0, tagset});
 	}	
 		
 	bool GarlicDestination::SubmitSessionKey (const uint8_t * key, const uint8_t * tag)

libi2pd/Garlic.h

@@ -243,7 +243,7 @@ namespace garlic
 				std::shared_ptr<I2NPMessage> msg);
 
 			void AddSessionKey (const uint8_t * key, const uint8_t * tag); // one tag
-			void AddECIESx25519Key (const uint8_t * key, const uint8_t * tag); // one tag
+			void AddECIESx25519Key (const uint8_t * key, uint64_t tag); // one tag
 			virtual bool SubmitSessionKey (const uint8_t * key, const uint8_t * tag); // from different thread
 			void DeliveryStatusSent (GarlicRoutingSessionPtr session, uint32_t msgID);
 			uint64_t AddECIESx25519SessionNextTag (ReceiveRatchetTagSetPtr tagset);
@@ -260,6 +260,7 @@ namespace garlic
 
 		protected:
 
+			void AddECIESx25519Key (const uint8_t * key, const uint8_t * tag); // one tag
 			bool HandleECIESx25519TagMessage (uint8_t * buf, size_t len); // return true if found
 			virtual void HandleI2NPMessage (const uint8_t * buf, size_t len) = 0; // called from clove only
 			virtual bool HandleCloveI2NPMessage (I2NPMessageType typeID, const uint8_t * payload, size_t len) = 0;

libi2pd/I2NPProtocol.cpp

@@ -660,68 +660,47 @@ namespace i2p
 					clearText[SHORT_REQUEST_RECORD_FLAG_OFFSET] & TUNNEL_BUILD_RECORD_GATEWAY_FLAG,
 					clearText[SHORT_REQUEST_RECORD_FLAG_OFFSET] & TUNNEL_BUILD_RECORD_ENDPOINT_FLAG);
 				i2p::tunnel::tunnels.AddTransitTunnel (transitTunnel);
-				if (isEndpoint)
+				
+				// encrypt reply
+				uint8_t nonce[12];
+				memset (nonce, 0, 12);
+				uint8_t * reply = buf + 1;
+				for (int j = 0; j < num; j++)
 				{	
-					// we are endpoint, create OutboundTunnelBuildReply	
-					auto otbrm = NewI2NPShortMessage ();
-					auto payload = otbrm->GetPayload ();
-					payload[0] = num; // num
-					payload[1] = i; // slot
-					payload +=2;
-					// reply
-					htobe16buf (payload, 3); payload += 2; // length, TODO
-					memset (payload, 0, 3); payload += 3; // ClearText: no options, and zero ret code. TODO
-					// ShortBuildReplyRecords. Exclude ours
-					uint8_t * records = buf + 1;
-					if (i > 0)
-					{	
-						memcpy (payload, records, i*SHORT_TUNNEL_BUILD_RECORD_SIZE);
-						payload += i*SHORT_TUNNEL_BUILD_RECORD_SIZE;
-						records += i*SHORT_TUNNEL_BUILD_RECORD_SIZE;
-					}	
-					if (i < num-1)
+					nonce[4] = j; // nonce is record #
+					if (j == i)
 					{
-						memcpy (payload, records, (num-1-i)*SHORT_TUNNEL_BUILD_RECORD_SIZE);
-						payload += (num-1-i)*SHORT_TUNNEL_BUILD_RECORD_SIZE;
+						memset (reply + SHORT_RESPONSE_RECORD_OPTIONS_OFFSET, 0, 2); // no options
+						reply[SHORT_RESPONSE_RECORD_RET_OFFSET] = 0;  // TODO: correct ret code
+						if (!i2p::crypto::AEADChaCha20Poly1305 (reply, SHORT_TUNNEL_BUILD_RECORD_SIZE - 16, 
+							noiseState.m_H, 32, replyKey, nonce, reply, SHORT_TUNNEL_BUILD_RECORD_SIZE, true)) // encrypt
+						{
+							LogPrint (eLogWarning, "I2NP: Short reply AEAD encryption failed");
+							return;
+						}	
 					}
-					otbrm->len += (payload - otbrm->GetPayload ());
-					otbrm->FillI2NPMessageHeader (eI2NPOutboundTunnelBuildReply, bufbe32toh (clearText + SHORT_REQUEST_RECORD_SEND_MSG_ID_OFFSET));
+					else
+						i2p::crypto::ChaCha20 (reply, SHORT_TUNNEL_BUILD_RECORD_SIZE, noiseState.m_CK, nonce, reply); 
+					reply += SHORT_TUNNEL_BUILD_RECORD_SIZE;	
+				}
+				// send reply
+				if (isEndpoint)
+				{
+					auto replyMsg = NewI2NPShortMessage ();
+					replyMsg->Concat (buf, len);
+					replyMsg->FillI2NPMessageHeader (eI2NPShortTunnelBuildReply, bufbe32toh (clearText + SHORT_REQUEST_RECORD_SEND_MSG_ID_OFFSET));
 					i2p::crypto::HKDF (noiseState.m_CK, nullptr, 0, "RGarlicKeyAndTag", noiseState.m_CK); 		
 					uint64_t tag;
 					memcpy (&tag, noiseState.m_CK, 8);
-					// send garlic to reply tunnel
+					// we send it to reply tunnel
 					transports.SendMessage (clearText + SHORT_REQUEST_RECORD_NEXT_IDENT_OFFSET,
-						CreateTunnelGatewayMsg (bufbe32toh (clearText + SHORT_REQUEST_RECORD_NEXT_TUNNEL_OFFSET),
-							i2p::garlic::WrapECIESX25519Message (otbrm,  noiseState.m_CK + 32, tag)));
+					CreateTunnelGatewayMsg (bufbe32toh (clearText + SHORT_REQUEST_RECORD_NEXT_TUNNEL_OFFSET),
+						i2p::garlic::WrapECIESX25519Message (replyMsg,  noiseState.m_CK + 32, tag)));
 				}	
 				else	
-				{	
-					// we are participant, encrypt reply
-					uint8_t nonce[12];
-					memset (nonce, 0, 12);
-					uint8_t * reply = buf + 1;
-					for (int j = 0; j < num; j++)
-					{	
-						nonce[4] = j; // nonce is record #
-						if (j == i)
-						{
-							memset (reply + SHORT_RESPONSE_RECORD_OPTIONS_OFFSET, 0, 2); // no options
-							reply[SHORT_RESPONSE_RECORD_RET_OFFSET] = 0;  // TODO: correct ret code
-							if (!i2p::crypto::AEADChaCha20Poly1305 (reply, SHORT_TUNNEL_BUILD_RECORD_SIZE - 16, 
-								noiseState.m_H, 32, replyKey, nonce, reply, SHORT_TUNNEL_BUILD_RECORD_SIZE, true)) // encrypt
-							{
-								LogPrint (eLogWarning, "I2NP: Short reply AEAD encryption failed");
-								return;
-							}	
-						}
-						else
-							i2p::crypto::ChaCha20 (reply, SHORT_TUNNEL_BUILD_RECORD_SIZE, noiseState.m_CK, nonce, reply); 
-						reply += SHORT_TUNNEL_BUILD_RECORD_SIZE;	
-					}
 					transports.SendMessage (clearText + SHORT_REQUEST_RECORD_NEXT_TUNNEL_OFFSET,
 						CreateI2NPMessage (eI2NPShortTunnelBuild, buf, len,
 							bufbe32toh (clearText + SHORT_REQUEST_RECORD_SEND_MSG_ID_OFFSET)));
-				}	
 				return;
 			}	
 			record += SHORT_TUNNEL_BUILD_RECORD_SIZE;
@@ -843,6 +822,7 @@ namespace i2p
 				HandleVariableTunnelBuildMsg (msgID, buf, size);
 			break;
 			case eI2NPVariableTunnelBuildReply:
+			case eI2NPShortTunnelBuildReply:	
 				HandleVariableTunnelBuildReplyMsg (msgID, buf, size);
 			break;
 			case eI2NPShortTunnelBuild:
@@ -905,6 +885,7 @@ namespace i2p
 				case eI2NPTunnelBuild:
 				case eI2NPTunnelBuildReply:
 				case eI2NPShortTunnelBuild:	
+				case eI2NPShortTunnelBuildReply:		
 					// forward to tunnel thread
 					i2p::tunnel::tunnels.PostTunnelData (msg);
 				break;

libi2pd/I2NPProtocol.h

@@ -136,7 +136,7 @@ namespace i2p
 		eI2NPVariableTunnelBuild = 23,
 		eI2NPVariableTunnelBuildReply = 24,
 		eI2NPShortTunnelBuild = 25,
-		eI2NPOutboundTunnelBuildReply = 26
+		eI2NPShortTunnelBuildReply = 26
 	};
 
 	const uint8_t TUNNEL_BUILD_RECORD_GATEWAY_FLAG = 0x80;

libi2pd/Tunnel.cpp

@@ -105,7 +105,16 @@ namespace tunnel
 			outboundTunnel->SendTunnelDataMsg (GetNextIdentHash (), 0, msg);
 		}	
 		else
+		{
+			if (m_Config->IsShort () && m_Config->GetLastHop ())
+			{
+				// add garlic key/tag for reply
+				uint8_t key[32];
+				uint64_t tag = m_Config->GetLastHop ()->GetGarlicKey (key);
+				i2p::context.AddECIESx25519Key (key, tag);
+			}	
 			i2p::transport::transports.SendMessage (GetNextIdentHash (), msg);
+		}	
 	}
 
 	bool Tunnel::HandleTunnelBuildResponse (uint8_t * msg, size_t len)
@@ -513,6 +522,8 @@ namespace tunnel
 							}
 							case eI2NPVariableTunnelBuild:
 							case eI2NPVariableTunnelBuildReply:
+							case eI2NPShortTunnelBuild:
+							case eI2NPShortTunnelBuildReply:
 							case eI2NPTunnelBuild:
 							case eI2NPTunnelBuildReply:	
 								HandleI2NPMessage (msg->GetBuffer (), msg->GetLength ());

libi2pd/TunnelConfig.cpp

@@ -260,5 +260,13 @@ namespace tunnel
 		nonce[4] = index; // nonce is index
 		i2p::crypto::ChaCha20 (record, SHORT_TUNNEL_BUILD_RECORD_SIZE, replyKey, nonce, record);
 	}	
+
+	uint64_t ShortECIESTunnelHopConfig::GetGarlicKey (uint8_t * key) const
+	{
+		uint64_t tag;
+		memcpy (&tag, m_CK, 8);
+		memcpy (key, m_CK + 32, 32);
+		return tag;
+	}	
 }
 }

libi2pd/TunnelConfig.h

@@ -44,6 +44,7 @@ namespace tunnel
 		virtual void CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID) = 0;
 		virtual bool DecryptBuildResponseRecord (uint8_t * records) const = 0;
 		virtual void DecryptRecord (uint8_t * records, int index) const; // AES
+		virtual uint64_t GetGarlicKey (uint8_t * key) const { return 0; }; // return tag
 	};
 
 	struct ElGamalTunnelHopConfig: public TunnelHopConfig
@@ -83,6 +84,7 @@ namespace tunnel
 		void CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID);
 		bool DecryptBuildResponseRecord (uint8_t * records) const;	
 		void DecryptRecord (uint8_t * records, int index) const override; // Chacha20
+		uint64_t GetGarlicKey (uint8_t * key) const override;	
 	};	
 	
 	class TunnelConfig