support of multiple incoming garlic sessions

Garlic.cpp

@@ -232,14 +232,17 @@ namespace garlic
 		uint32_t length = be32toh (*(uint32_t *)buf);
 		buf += 4;
 		std::string sessionTag((const char *)buf, 32);
-		if (m_SessionTags.count (sessionTag) > 0)
+		auto it = m_SessionTags.find (sessionTag);
+		if (it != m_SessionTags.end ())
 		{
 			// existing session
+			std::string sessionKey (it->second);
+			m_SessionTags.erase (it); // tag might be used only once
 			uint8_t iv[32]; // IV is first 16 bytes
 			CryptoPP::SHA256().CalculateDigest(iv, buf, 32);
-			m_Decryption.SetKeyWithIV (m_SessionKey, 32, iv);
+			m_Decryption.SetKeyWithIV ((uint8_t *)sessionKey.c_str (), 32, iv); // tag is mapped to 32 bytes key
 			m_Decryption.ProcessData(buf + 32, buf + 32, length - 32);
-			HandleAESBlock (buf + 32, length - 32);
+			HandleAESBlock (buf + 32, length - 32, (uint8_t *)sessionKey.c_str ());
 		}
 		else
 		{
@@ -248,22 +251,21 @@ namespace garlic
 			i2p::crypto::ElGamalDecrypt (
 			   	isFromTunnel ? i2p::context.GetLeaseSetPrivateKey () : i2p::context.GetPrivateKey (), 
 				buf, (uint8_t *)&elGamal, true);
-			memcpy (m_SessionKey, elGamal.sessionKey, 32);
 			uint8_t iv[32]; // IV is first 16 bytes
 			CryptoPP::SHA256().CalculateDigest(iv, elGamal.preIV, 32); 
-			m_Decryption.SetKeyWithIV (m_SessionKey, 32, iv);
+			m_Decryption.SetKeyWithIV (elGamal.sessionKey, 32, iv);
 			m_Decryption.ProcessData(buf + 514, buf + 514, length - 514);
-			HandleAESBlock (buf + 514, length - 514);
+			HandleAESBlock (buf + 514, length - 514, elGamal.sessionKey);
 		}	
 		
 	}	
 
-	void GarlicRouting::HandleAESBlock (uint8_t * buf, size_t len)
+	void GarlicRouting::HandleAESBlock (uint8_t * buf, size_t len, uint8_t * sessionKey)
 	{
 		uint16_t tagCount = be16toh (*(uint16_t *)buf);
 		buf += 2;
 		for (int i = 0; i < tagCount; i++)
-			m_SessionTags.insert (std::string ((const char *)(buf + i*32), 32));
+			m_SessionTags[std::string ((const char *)(buf + i*32), 32)] = std::string ((const char *)sessionKey, 32);
 		buf += tagCount*32;
 		uint32_t payloadSize = be32toh (*(uint32_t *)buf);
 		buf += 4;

Garlic.h

@@ -3,7 +3,6 @@
 
 #include <inttypes.h>
 #include <map>
-#include <set>
 #include <string>
 #include <cryptopp/modes.h>
 #include <cryptopp/aes.h>
@@ -75,7 +74,7 @@ namespace garlic
 
 		private:
 
-			void HandleAESBlock (uint8_t * buf, size_t len);
+			void HandleAESBlock (uint8_t * buf, size_t len, uint8_t * sessionKey);
 			void HandleGarlicPayload (uint8_t * buf, size_t len);
 			
 		private:
@@ -83,8 +82,7 @@ namespace garlic
 			// outgoing sessions
 			std::map<i2p::data::IdentHash, GarlicRoutingSession *> m_Sessions;
 			// incoming session
-			uint8_t m_SessionKey[32];
-			std::set<std::string> m_SessionTags;
+			std::map<std::string, std::string> m_SessionTags; // tag -> key
 			CryptoPP::CBC_Mode<CryptoPP::AES>::Decryption m_Decryption;
 	};