i2pd/core/transport/SSUSession.h

#ifndef SSU_SESSION_H__
#define SSU_SESSION_H__

#include <inttypes.h>
#include <set>
#include <memory>
#include "crypto/aes.h"
#include "crypto/hmac.h"
#include "I2NPProtocol.h"
#include "TransportSession.h"
#include "SSUData.h"

namespace i2p
{
namespace transport
{
#pragma pack(1)
    // Warning: do not change the order of these variables
    // (or fix the unsafe casts in SSU.h)
    struct SSUHeader
    {
        uint8_t mac[16];
        uint8_t iv[16];
        uint8_t flag;
        uint32_t time;  

        uint8_t GetPayloadType () const { return flag >> 4; };
    };
#pragma pack()

    const int SSU_CONNECT_TIMEOUT = 5; // 5 seconds
    const int SSU_TERMINATION_TIMEOUT = 330; // 5.5 minutes

    // payload types (4 bits)
    const uint8_t PAYLOAD_TYPE_SESSION_REQUEST = 0;
    const uint8_t PAYLOAD_TYPE_SESSION_CREATED = 1;
    const uint8_t PAYLOAD_TYPE_SESSION_CONFIRMED = 2;
    const uint8_t PAYLOAD_TYPE_RELAY_REQUEST = 3;
    const uint8_t PAYLOAD_TYPE_RELAY_RESPONSE = 4;
    const uint8_t PAYLOAD_TYPE_RELAY_INTRO = 5;
    const uint8_t PAYLOAD_TYPE_DATA = 6;
    const uint8_t PAYLOAD_TYPE_PEER_TEST = 7;
    const uint8_t PAYLOAD_TYPE_SESSION_DESTROYED = 8;

    enum SessionState
    {
        eSessionStateUnknown,   
        eSessionStateIntroduced,
        eSessionStateEstablished,
        eSessionStateClosed,
        eSessionStateFailed
    };  

    enum PeerTestParticipant
    {
        ePeerTestParticipantUnknown = 0,
        ePeerTestParticipantAlice1,
        ePeerTestParticipantAlice2,
        ePeerTestParticipantBob,
        ePeerTestParticipantCharlie
    };
    
    class SSUServer;
    class SSUSession: public TransportSession, public std::enable_shared_from_this<SSUSession>
    {
        public:

            SSUSession (SSUServer& server, boost::asio::ip::udp::endpoint& remoteEndpoint,
                std::shared_ptr<const i2p::data::RouterInfo> router = nullptr, bool peerTest = false);
            void ProcessNextMessage (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint);      
            ~SSUSession ();
            
            void Connect ();
            void WaitForConnect ();
            void Introduce (uint32_t iTag, const uint8_t * iKey);
            void WaitForIntroduction ();
            void Close ();
            void Done ();
            boost::asio::ip::udp::endpoint& GetRemoteEndpoint () { return m_RemoteEndpoint; };
            bool IsV6 () const { return m_RemoteEndpoint.address ().is_v6 (); };
            void SendI2NPMessages (const std::vector<std::shared_ptr<I2NPMessage> >& msgs);
            void SendPeerTest (); // Alice          

            SessionState GetState () const  { return m_State; };
            size_t GetNumSentBytes () const { return m_NumSentBytes; };
            size_t GetNumReceivedBytes () const { return m_NumReceivedBytes; };
            
            void SendKeepAlive ();  
            uint32_t GetRelayTag () const { return m_RelayTag; };   
            uint32_t GetCreationTime () const { return m_CreationTime; };

            void FlushData ();
            
        private:

            boost::asio::io_service& GetService ();
            void CreateAESandMacKey (const uint8_t * pubKey); 

            void PostI2NPMessages (std::vector<std::shared_ptr<I2NPMessage> > msgs);
            void ProcessMessage (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint); // call for established session
            void ProcessSessionRequest (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint);
            void SendSessionRequest ();
            void SendRelayRequest (uint32_t iTag, const uint8_t * iKey);
            void ProcessSessionCreated (uint8_t * buf, size_t len);
            void SendSessionCreated (const uint8_t * x);
            void ProcessSessionConfirmed (uint8_t * buf, size_t len);
            void SendSessionConfirmed (const uint8_t * y, const uint8_t * ourAddress, size_t ourAddressLen);
            void ProcessRelayRequest (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& from);
            void SendRelayResponse (uint32_t nonce, const boost::asio::ip::udp::endpoint& from,
                const uint8_t * introKey, const boost::asio::ip::udp::endpoint& to);
            void SendRelayIntro (SSUSession * session, const boost::asio::ip::udp::endpoint& from);
            void ProcessRelayResponse (uint8_t * buf, size_t len);
            void ProcessRelayIntro (uint8_t * buf, size_t len);
            void Established ();
            void Failed ();
            void ScheduleConnectTimer ();
            void HandleConnectTimer (const boost::system::error_code& ecode);
            void ProcessPeerTest (const uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint);
            void SendPeerTest (uint32_t nonce, uint32_t address, uint16_t port, const uint8_t * introKey, bool toAddress = true, bool sendAddress = true); 
            void ProcessData (uint8_t * buf, size_t len);       
            void SendSesionDestroyed ();
            void Send (uint8_t type, const uint8_t * payload, size_t len); // with session key
            void Send (const uint8_t * buf, size_t size); 
            
            void FillHeaderAndEncrypt (uint8_t payloadType, uint8_t * buf, size_t len, const uint8_t * aesKey, const uint8_t * iv, const uint8_t * macKey);
            void FillHeaderAndEncrypt (uint8_t payloadType, uint8_t * buf, size_t len); // with session key 
            void Decrypt (uint8_t * buf, size_t len, const uint8_t * aesKey);
            void DecryptSessionKey (uint8_t * buf, size_t len);
            bool Validate (uint8_t * buf, size_t len, const uint8_t * macKey);          
            const uint8_t * GetIntroKey () const; 

            void ScheduleTermination ();
            void HandleTerminationTimer (const boost::system::error_code& ecode);

        private:
    
            friend class SSUData; // TODO: change in later
            SSUServer& m_Server;
            boost::asio::ip::udp::endpoint m_RemoteEndpoint;
            boost::asio::deadline_timer m_Timer;
            bool m_PeerTest;
            SessionState m_State;
            bool m_IsSessionKey;
            uint32_t m_RelayTag;    
            i2p::crypto::CBCEncryption m_SessionKeyEncryption;
            i2p::crypto::CBCDecryption m_SessionKeyDecryption;
            i2p::crypto::AESKey m_SessionKey;
            i2p::crypto::MACKey m_MacKey;
            uint32_t m_CreationTime; // seconds since epoch
            SSUData m_Data;
            bool m_IsDataReceived;
    };


}
}

#endif