handle new session reply

libi2pd/ECIESX25519AEADRatchetSession.cpp

@@ -137,6 +137,7 @@ namespace garlic
 		}
 		if (isStatic) MixHash (buf, len); // h = SHA256(h || ciphertext)
         m_State = eSessionStateNewSessionReceived;            
+		GetOwner ()->AddECIESx25519Session (m_RemoteStaticKey, shared_from_this ());
 
         HandlePayload (payload.data (), len - 16, handleClove);    
 
@@ -273,8 +274,52 @@ namespace garlic
 
     bool ECIESX25519AEADRatchetSession::NewOutgoingSessionReply (const uint8_t * buf, size_t len, CloveHandler handleClove)
     {
-        // TODO  
+		// we are Alice
 		LogPrint (eLogDebug, "Garlic: reply received");
+		const uint8_t * tag = buf;
+		buf += 8; len -= 8; // tag
+        uint8_t bepk[32]; // Bob's ephemeral key
+		if (!i2p::crypto::GetElligator ()->Decode (buf, bepk))
+		{ 
+			LogPrint (eLogError, "Garlic: Can't decode elligator");
+			return false;	
+		} 
+		buf += 32; len -= 32;
+		// KDF for  Reply Key Section
+        MixHash (tag, 8); // h = SHA256(h || tag)
+        MixHash (bepk, 32); // h = SHA256(h || bepk)		
+		uint8_t sharedSecret[32];      
+        m_EphemeralKeys.Agree (bepk, sharedSecret); // sharedSecret = x25519(aesk, bepk)  
+		i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64) 
+		 uint8_t nonce[12];
+		memset (nonce, 0, 12); // n = 0
+        // calulate hash for zero length
+		if (!i2p::crypto::AEADChaCha20Poly1305 (buf, 0, m_H, 32, m_CK + 32, nonce, sharedSecret/* can be anyting */, 0, false)) // decrypt, DECRYPT(k, n, ZEROLEN, ad) verification only
+		{
+			LogPrint (eLogWarning, "Garlic: Reply key section AEAD decryption failed");
+			return false;
+		}
+		MixHash (buf, 16); // h = SHA256(h || ciphertext)  
+		buf += 16; len -= 16;
+		// KDF for payload
+        uint8_t keydata[64];
+        i2p::crypto::HKDF (m_CK, nullptr, 0, "", keydata); // keydata = HKDF(chainKey, ZEROLEN, "", 64)
+        // k_ab = keydata[0:31], k_ba = keydata[32:63]
+        m_TagsetAB.DHInitialize (m_CK, keydata); // tagset_ab = DH_INITIALIZE(chainKey, k_ab)
+        m_TagsetBA.DHInitialize (m_CK, keydata + 32); // tagset_ba = DH_INITIALIZE(chainKey, k_ba)
+        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);
+        if (!i2p::crypto::AEADChaCha20Poly1305 (buf, len - 16, m_H, 32, keydata, nonce, payload.data (), len - 16, false)) // decrypt
+		{
+			LogPrint (eLogWarning, "Garlic: Payload section AEAD decryption failed");
+			return false;
+		}
+	
+		// TODO: change state
+		GetOwner ()->AddECIESx25519Session (m_RemoteStaticKey, shared_from_this ());
+		HandlePayload (payload.data (), len - 16, handleClove); 
+
         return true;
     }
 

libi2pd/Garlic.cpp

@@ -869,23 +869,14 @@ namespace garlic
         {
             // TODO
             auto session = it->second;
-            if (session->NewOutgoingSessionReply (buf, len, handleClove))
-                m_ECIESx25519Sessions.emplace (session->GetRemoteStaticKey (), session);
-            else    
-            {
+            if (!session->NewOutgoingSessionReply (buf, len, handleClove))
                 LogPrint (eLogError, "Garlic: can't decrypt ECIES-X25519-AEAD-Ratchet new session reply");
-                m_ECIESx25519Tags.erase (tag);
-                m_ECIESx25519Sessions.erase (session->GetRemoteStaticKey ());
-            }
+			 m_ECIESx25519Tags.erase (tag);
         }
         else
         {
             auto session = std::make_shared<ECIESX25519AEADRatchetSession> (this);
-            if (session->NewIncomingSession (buf, len, handleClove))
-            {
-                m_ECIESx25519Sessions.emplace (session->GetRemoteStaticKey (), session);
-            }
-            else
+            if (!session->NewIncomingSession (buf, len, handleClove))
                  LogPrint (eLogError, "Garlic: can't decrypt ECIES-X25519-AEAD-Ratchet new session");
         }
 	}
@@ -950,5 +941,11 @@ namespace garlic
     {
         m_ECIESx25519Tags.emplace (tag, session);
     }
+
+	void GarlicDestination::AddECIESx25519Session (const uint8_t * staticKey, ECIESX25519AEADRatchetSessionPtr session)
+	{
+		m_ECIESx25519Sessions.emplace (staticKey, session);
+	}
+
 }
 }

libi2pd/Garlic.h

@@ -218,6 +218,7 @@ namespace garlic
 			virtual bool SubmitSessionKey (const uint8_t * key, const uint8_t * tag); // from different thread
 			void DeliveryStatusSent (ElGamalAESSessionPtr session, uint32_t msgID);
             void AddECIESx25519SessionTag (uint64_t tag, ECIESX25519AEADRatchetSessionPtr session);
+			void AddECIESx25519Session (const uint8_t * staticKey, ECIESX25519AEADRatchetSessionPtr session);
 
 			virtual void ProcessGarlicMessage (std::shared_ptr<I2NPMessage> msg);
 			virtual void ProcessDeliveryStatusMessage (std::shared_ptr<I2NPMessage> msg);