i2pd/libi2pd/ECIESX25519AEADRatchetSession.h

#ifndef ECIES_X25519_AEAD_RATCHET_SESSION_H__
#define ECIES_X25519_AEAD_RATCHET_SESSION_H__

#include <string.h>
#include <inttypes.h>
#include <functional>
#include <memory>
#include <vector>
#include <list>
#include <unordered_map>
#include "Identity.h"
#include "Crypto.h"
#include "Garlic.h"
#include "Tag.h"

namespace i2p
{
namespace garlic
{
	class ECIESX25519AEADRatchetSession;
    class RatchetTagSet
    {
        public:

			RatchetTagSet (std::shared_ptr<ECIESX25519AEADRatchetSession> session): m_Session (session) {};	
			
            void DHInitialize (const uint8_t * rootKey, const uint8_t * k);
            void NextSessionTagRatchet ();
            uint64_t GetNextSessionTag ();
			const uint8_t * GetNextRootKey () const { return m_NextRootKey; };
			int GetNextIndex () const { return m_NextIndex; }; 
			void GetSymmKey (int index, uint8_t * key);

			std::shared_ptr<ECIESX25519AEADRatchetSession> GetSession () { return m_Session.lock (); };
			int GetTagSetID () const { return m_TagSetID; };
			void SetTagSetID (int tagsetID) { m_TagSetID = tagsetID; };
			
		private:
			
           union
           {
               uint64_t ll[8]; 
               uint8_t buf[64];

               const uint8_t * GetSessTagCK () const { return buf; }; // sessTag_chainKey = keydata[0:31]
               const uint8_t * GetSessTagConstant () const { return buf + 32; }; // SESSTAG_CONSTANT = keydata[32:63] 
               uint64_t GetTag () const { return ll[4]; }; // tag = keydata[32:39]            
             
           } m_KeyData;  
           uint8_t m_SessTagConstant[32], m_SymmKeyCK[32], m_CurrentSymmKeyCK[64], m_NextRootKey[32];   
		   int m_NextIndex, m_NextSymmKeyIndex;
		   std::unordered_map<int, i2p::data::Tag<32> > m_ItermediateSymmKeys;
		   std::weak_ptr<ECIESX25519AEADRatchetSession> m_Session;
		   int m_TagSetID = 0;	
    };       

    enum ECIESx25519BlockType
	{
		eECIESx25519BlkDateTime = 0,
		eECIESx25519BlkSessionID = 1, 
		eECIESx25519BlkTermination = 4,
		eECIESx25519BlkOptions = 5,
		eECIESx25519BlkNextKey = 7,
		eECIESx25519BlkAck = 8,
		eECIESx25519BlkAckRequest = 9,
		eECIESx25519BlkGalicClove = 11,
		eECIESx25519BlkPadding = 254	
	};	

	const uint8_t ECIESX25519_NEXT_KEY_KEY_PRESENT_FLAG = 0x01;
	const uint8_t ECIESX25519_NEXT_KEY_REVERSE_KEY_FLAG = 0x02;
	const uint8_t ECIESX25519_NEXT_KEY_REQUEST_REVERSE_KEY_FLAG = 0x04;
	
	const int ECIESX25519_RESTART_TIMEOUT = 120; // number of second of inactivity we should restart after
	const int ECIESX25519_EXPIRATION_TIMEOUT = 480; // in seconds
	const int ECIESX25519_INCOMING_TAGS_EXPIRATION_TIMEOUT = 600; // in seconds
	const int ECIESX25519_TAGSET_MAX_NUM_TAGS = 1024; // number of tags we request new tagset after
	const int ECIESX25519_MIN_NUM_GENERATED_TAGS = 24;
	const int ECIESX25519_MAX_NUM_GENERATED_TAGS = 160;
	const int ECIESX25519_NSR_NUM_GENERATED_TAGS = 12;
	
    class ECIESX25519AEADRatchetSession: public GarlicRoutingSession, public std::enable_shared_from_this<ECIESX25519AEADRatchetSession>
    {
        enum SessionState
        {
            eSessionStateNew =0,
            eSessionStateNewSessionReceived,
			eSessionStateNewSessionSent,
			eSessionStateNewSessionReplySent,
			eSessionStateEstablished		
        };

		struct DHRatchet
		{
			int keyID = 0;
			i2p::crypto::X25519Keys key;
			uint8_t remote[32]; // last remote public key
			bool newKey = true;
		};	
		
        public:

            ECIESX25519AEADRatchetSession (GarlicDestination * owner, bool attachLeaseSet);
            ~ECIESX25519AEADRatchetSession ();

			bool HandleNextMessage (const uint8_t * buf, size_t len, std::shared_ptr<RatchetTagSet> receiveTagset, int index = 0);
            std::shared_ptr<I2NPMessage> WrapSingleMessage (std::shared_ptr<const I2NPMessage> msg);

            const uint8_t * GetRemoteStaticKey () const { return m_RemoteStaticKey; }
			void SetRemoteStaticKey (const uint8_t * key) { memcpy (m_RemoteStaticKey, key, 32); }

			void SetDestination (const i2p::data::IdentHash& dest) // TODO:
			{
				if (!m_Destination) m_Destination.reset (new i2p::data::IdentHash (dest));
			}
			
			bool CheckExpired (uint64_t ts); // true is expired
			bool CanBeRestarted (uint64_t ts) const { return ts > m_LastActivityTimestamp + ECIESX25519_RESTART_TIMEOUT; }

        private:

			void ResetKeys ();
            void MixHash (const uint8_t * buf, size_t len);
			void CreateNonce (uint64_t seqn, uint8_t * nonce);
            bool GenerateEphemeralKeysAndEncode (uint8_t * buf); // buf is 32 bytes
			std::shared_ptr<RatchetTagSet> CreateNewSessionTagset ();

			bool HandleNewIncomingSession (const uint8_t * buf, size_t len);
            bool HandleNewOutgoingSessionReply (const uint8_t * buf, size_t len);
			bool HandleExistingSessionMessage (const uint8_t * buf, size_t len, std::shared_ptr<RatchetTagSet> receiveTagset, int index);
            void HandlePayload (const uint8_t * buf, size_t len, const std::shared_ptr<RatchetTagSet>& receiveTagset, int index);
			void HandleNextKey (const uint8_t * buf, size_t len, const std::shared_ptr<RatchetTagSet>& receiveTagset);
			
            bool NewOutgoingSessionMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen);
            bool NewSessionReplyMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen);
			bool NextNewSessionReplyMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen);
			bool NewExistingSessionMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen);
	
            std::vector<uint8_t> CreatePayload (std::shared_ptr<const I2NPMessage> msg, bool first);
            size_t CreateGarlicClove (std::shared_ptr<const I2NPMessage> msg, uint8_t * buf, size_t len, bool isDestination = false);
			size_t CreateDeliveryStatusClove (std::shared_ptr<const I2NPMessage> msg, uint8_t * buf, size_t len);

			void GenerateMoreReceiveTags (std::shared_ptr<RatchetTagSet> receiveTagset, int numTags);
			void NewNextSendRatchet ();
			
        private:

            uint8_t m_H[32], m_CK[64] /* [chainkey, key] */, m_RemoteStaticKey[32];
			uint8_t m_Aepk[32]; // Alice's ephemeral keys, for incoming only
			uint8_t m_NSREncodedKey[32], m_NSRH[32], m_NSRKey[32]; // new session reply, for incoming only
            i2p::crypto::X25519Keys m_EphemeralKeys;
            SessionState m_State = eSessionStateNew;
			uint64_t m_LastActivityTimestamp = 0; // incoming
            std::shared_ptr<RatchetTagSet> m_SendTagset, m_NSRTagset;
			std::unique_ptr<i2p::data::IdentHash> m_Destination;// TODO: might not need it 
			std::list<std::pair<uint16_t, int> > m_AckRequests; // (tagsetid, index)
			bool m_SendReverseKey = false, m_SendForwardKey = false;
			std::unique_ptr<DHRatchet> m_NextReceiveRatchet, m_NextSendRatchet;
     };

	std::shared_ptr<I2NPMessage> WrapECIESX25519AEADRatchetMessage (std::shared_ptr<const I2NPMessage> msg, const uint8_t * key, uint64_t tag);
}
}

#endif