generate more receive tags when needed

libi2pd/ECIESX25519AEADRatchetSession.cpp

@@ -295,13 +295,7 @@ namespace garlic
 		m_ReceiveTagset.NextSessionTagRatchet ();
         m_SendTagset.DHInitialize (m_CK, keydata + 32); // tagset_ba = DH_INITIALIZE(chainKey, k_ba)
 		m_SendTagset.NextSessionTagRatchet ();	
-		auto numTags = GetOwner ()->GetNumTags ();
+		GenerateMoreReceiveTags (GetOwner ()->GetNumTags ());
-		for (int i = 0; i < numTags; i++)
-		{
-			auto index = m_ReceiveTagset.GetNextIndex ();
-			uint64_t tag = m_ReceiveTagset.GetNextSessionTag ();
-			GetOwner ()->AddECIESx25519SessionTag (index, tag, shared_from_this ());
-		}	
         i2p::crypto::HKDF (keydata + 32, nullptr, 0, "AttachPayloadKDF", keydata, 32); // k = HKDF(k_ba, ZEROLEN, "AttachPayloadKDF", 32)
         // encrypt payload
         if (!i2p::crypto::AEADChaCha20Poly1305 (payload, len, m_H, 32, keydata, nonce, out + offset, len + 16, true)) // encrypt
@@ -310,7 +304,7 @@ namespace garlic
 			return false;
 		}
 		m_State = eSessionStateEstablished;
-
+		
         return true;
     }
 
@@ -353,13 +347,7 @@ namespace garlic
 		m_SendTagset.NextSessionTagRatchet ();
         m_ReceiveTagset.DHInitialize (m_CK, keydata + 32); // tagset_ba = DH_INITIALIZE(chainKey, k_ba)
 		m_ReceiveTagset.NextSessionTagRatchet ();
-		auto numTags = GetOwner ()->GetNumTags ();
+		GenerateMoreReceiveTags (GetOwner ()->GetNumTags ());
-		for (int i = 0; i < numTags; i++)
-		{
-			auto index = m_ReceiveTagset.GetNextIndex ();
-			uint64_t tag = m_ReceiveTagset.GetNextSessionTag ();
-			GetOwner ()->AddECIESx25519SessionTag (index, tag, shared_from_this ());
-		}	
         i2p::crypto::HKDF (keydata + 32, nullptr, 0, "AttachPayloadKDF", keydata, 32); // k = HKDF(k_ba, ZEROLEN, "AttachPayloadKDF", 32)		
 		// decrypt payload
 		std::vector<uint8_t> payload (len - 16);
@@ -405,6 +393,9 @@ namespace garlic
 			return false;
 		}	
 		HandlePayload (payload.data (), len - 16); 
+		if (m_NumReceiveTags > 0)m_NumReceiveTags--;
+		if (m_NumReceiveTags <= GetOwner ()->GetNumTags ()*2/3)
+			GenerateMoreReceiveTags (GetOwner ()->GetNumTags ());		
 		return true;
 	}
 
@@ -513,6 +504,17 @@ namespace garlic
         memcpy (buf + 9, msg->GetPayload (), msg->GetPayloadLength ());
         return cloveSize + 3;
     } 
+
+	void ECIESX25519AEADRatchetSession::GenerateMoreReceiveTags (int numTags)
+	{
+		for (int i = 0; i < numTags; i++)
+		{
+			auto index = m_ReceiveTagset.GetNextIndex ();
+			uint64_t tag = m_ReceiveTagset.GetNextSessionTag ();
+			GetOwner ()->AddECIESx25519SessionTag (index, tag, shared_from_this ());
+		}	
+		m_NumReceiveTags += numTags;	
+	}	
 }
 }
 

libi2pd/ECIESX25519AEADRatchetSession.h

@@ -80,7 +80,7 @@ namespace garlic
 			{
 				if (!m_Destination) m_Destination.reset (new i2p::data::IdentHash (dest));
 			}
-
+			
         private:
 
 			void ResetKeys ();
@@ -101,6 +101,8 @@ namespace garlic
             std::vector<uint8_t> CreatePayload (std::shared_ptr<const I2NPMessage> msg);
             size_t CreateGarlicClove (std::shared_ptr<const I2NPMessage> msg, uint8_t * buf, size_t len, bool isDestination = false);
 
+			void GenerateMoreReceiveTags (int numTags);
+			
         private:
 
             uint8_t m_H[32], m_CK[64] /* [chainkey, key] */, m_RemoteStaticKey[32];
@@ -108,6 +110,7 @@ namespace garlic
             i2p::crypto::X25519Keys m_EphemeralKeys;
             SessionState m_State = eSessionStateNew;
             RatchetTagSet m_SendTagset, m_ReceiveTagset;
+			int m_NumReceiveTags = 0;
 			std::unique_ptr<i2p::data::IdentHash> m_Destination;// TODO: might not need it 
     };
 }