i2pd/core/I2NPProtocol.h

#ifndef I2NP_PROTOCOL_H__
#define I2NP_PROTOCOL_H__

#include <inttypes.h>
#include <string.h>
#include <set>
#include <memory>
#include <cryptopp/sha.h>
#include "util/I2PEndian.h"
#include "Identity.h"
#include "RouterInfo.h"
#include "LeaseSet.h"

namespace i2p
{   
    // I2NP header
    const size_t I2NP_HEADER_TYPEID_OFFSET = 0;
    const size_t I2NP_HEADER_MSGID_OFFSET = I2NP_HEADER_TYPEID_OFFSET + 1;
    const size_t I2NP_HEADER_EXPIRATION_OFFSET = I2NP_HEADER_MSGID_OFFSET + 4;
    const size_t I2NP_HEADER_SIZE_OFFSET = I2NP_HEADER_EXPIRATION_OFFSET + 8;
    const size_t I2NP_HEADER_CHKS_OFFSET = I2NP_HEADER_SIZE_OFFSET + 2;
    const size_t I2NP_HEADER_SIZE = I2NP_HEADER_CHKS_OFFSET + 1;

    // I2NP short header
    const size_t I2NP_SHORT_HEADER_TYPEID_OFFSET = 0;
    const size_t I2NP_SHORT_HEADER_EXPIRATION_OFFSET = I2NP_SHORT_HEADER_TYPEID_OFFSET + 1;
    const size_t I2NP_SHORT_HEADER_SIZE = I2NP_SHORT_HEADER_EXPIRATION_OFFSET + 4;
    
    // Tunnel Gateway header
    const size_t TUNNEL_GATEWAY_HEADER_TUNNELID_OFFSET = 0;
    const size_t TUNNEL_GATEWAY_HEADER_LENGTH_OFFSET = TUNNEL_GATEWAY_HEADER_TUNNELID_OFFSET + 4;
    const size_t TUNNEL_GATEWAY_HEADER_SIZE = TUNNEL_GATEWAY_HEADER_LENGTH_OFFSET + 2;

    // DeliveryStatus   
    const size_t DELIVERY_STATUS_MSGID_OFFSET = 0;
    const size_t DELIVERY_STATUS_TIMESTAMP_OFFSET = DELIVERY_STATUS_MSGID_OFFSET + 4;
    const size_t DELIVERY_STATUS_SIZE = DELIVERY_STATUS_TIMESTAMP_OFFSET + 8;

    // DatabaseStore
    const size_t DATABASE_STORE_KEY_OFFSET = 0;
    const size_t DATABASE_STORE_TYPE_OFFSET = DATABASE_STORE_KEY_OFFSET + 32;
    const size_t DATABASE_STORE_REPLY_TOKEN_OFFSET = DATABASE_STORE_TYPE_OFFSET + 1;
    const size_t DATABASE_STORE_HEADER_SIZE = DATABASE_STORE_REPLY_TOKEN_OFFSET + 4;

    // TunnelBuild  
    const size_t TUNNEL_BUILD_RECORD_SIZE = 528;

    //BuildRequestRecordClearText
    const size_t BUILD_REQUEST_RECORD_RECEIVE_TUNNEL_OFFSET = 0;
    const size_t BUILD_REQUEST_RECORD_OUR_IDENT_OFFSET = BUILD_REQUEST_RECORD_RECEIVE_TUNNEL_OFFSET + 4;
    const size_t BUILD_REQUEST_RECORD_NEXT_TUNNEL_OFFSET = BUILD_REQUEST_RECORD_OUR_IDENT_OFFSET + 32;
    const size_t BUILD_REQUEST_RECORD_NEXT_IDENT_OFFSET = BUILD_REQUEST_RECORD_NEXT_TUNNEL_OFFSET + 4;
    const size_t BUILD_REQUEST_RECORD_LAYER_KEY_OFFSET = BUILD_REQUEST_RECORD_NEXT_IDENT_OFFSET + 32;
    const size_t BUILD_REQUEST_RECORD_IV_KEY_OFFSET = BUILD_REQUEST_RECORD_LAYER_KEY_OFFSET + 32;
    const size_t BUILD_REQUEST_RECORD_REPLY_KEY_OFFSET = BUILD_REQUEST_RECORD_IV_KEY_OFFSET + 32;
    const size_t BUILD_REQUEST_RECORD_REPLY_IV_OFFSET = BUILD_REQUEST_RECORD_REPLY_KEY_OFFSET + 32;
    const size_t BUILD_REQUEST_RECORD_FLAG_OFFSET = BUILD_REQUEST_RECORD_REPLY_IV_OFFSET + 16;
    const size_t BUILD_REQUEST_RECORD_REQUEST_TIME_OFFSET = BUILD_REQUEST_RECORD_FLAG_OFFSET + 1;
    const size_t BUILD_REQUEST_RECORD_SEND_MSG_ID_OFFSET = BUILD_REQUEST_RECORD_REQUEST_TIME_OFFSET + 4;
    const size_t BUILD_REQUEST_RECORD_PADDING_OFFSET = BUILD_REQUEST_RECORD_SEND_MSG_ID_OFFSET + 4;
    const size_t BUILD_REQUEST_RECORD_CLEAR_TEXT_SIZE = 222;
    
    // BuildRequestRecordEncrypted  
    const size_t BUILD_REQUEST_RECORD_TO_PEER_OFFSET = 0;
    const size_t BUILD_REQUEST_RECORD_ENCRYPTED_OFFSET = BUILD_REQUEST_RECORD_TO_PEER_OFFSET + 16;
    
    // BuildResponseRecord
    const size_t BUILD_RESPONSE_RECORD_HASH_OFFSET = 0;
    const size_t BUILD_RESPONSE_RECORD_PADDING_OFFSET = 32;
    const size_t BUILD_RESPONSE_RECORD_PADDING_SIZE = 495;
    const size_t BUILD_RESPONSE_RECORD_RET_OFFSET = BUILD_RESPONSE_RECORD_PADDING_OFFSET + BUILD_RESPONSE_RECORD_PADDING_SIZE;

    enum I2NPMessageType
    {
        eI2NPDatabaseStore = 1,
        eI2NPDatabaseLookup = 2,
        eI2NPDatabaseSearchReply = 3,
        eI2NPDeliveryStatus = 10,
        eI2NPGarlic = 11,
        eI2NPTunnelData = 18,
        eI2NPTunnelGateway = 19,
        eI2NPData = 20,
        eI2NPTunnelBuild = 21,
        eI2NPTunnelBuildReply = 22,
        eI2NPVariableTunnelBuild = 23,
        eI2NPVariableTunnelBuildReply = 24  
    };  

    const int NUM_TUNNEL_BUILD_RECORDS = 8; 

    // DatabaseLookup flags
    const uint8_t DATABASE_LOOKUP_DELIVERY_FLAG = 0x01;
    const uint8_t DATABASE_LOOKUP_ENCYPTION_FLAG = 0x02;    
    const uint8_t DATABASE_LOOKUP_TYPE_FLAGS_MASK = 0x0C;
    const uint8_t DATABASE_LOOKUP_TYPE_NORMAL_LOOKUP = 0;
    const uint8_t DATABASE_LOOKUP_TYPE_LEASESET_LOOKUP = 0x04; // 0100
    const uint8_t DATABASE_LOOKUP_TYPE_ROUTERINFO_LOOKUP = 0x08; // 1000            
    const uint8_t DATABASE_LOOKUP_TYPE_EXPLORATORY_LOOKUP = 0x0C; // 1100

    const int MAX_NUM_TRANSIT_TUNNELS = 2500;

namespace tunnel
{       
    class InboundTunnel;
    class TunnelPool;
}

    const size_t I2NP_MAX_MESSAGE_SIZE = 32768; 
    const size_t I2NP_MAX_SHORT_MESSAGE_SIZE = 4096; 
    struct I2NPMessage
    {   
        uint8_t * buf;  
        size_t len, offset, maxLen;
        std::shared_ptr<i2p::tunnel::InboundTunnel> from;
        
        I2NPMessage (): buf (nullptr),len (I2NP_HEADER_SIZE + 2), 
            offset(2), maxLen (0), from (nullptr) {};  // reserve 2 bytes for NTCP header
    
        // header accessors
        uint8_t * GetHeader () { return GetBuffer (); };
        const uint8_t * GetHeader () const { return GetBuffer (); };
        void SetTypeID (uint8_t typeID) { GetHeader ()[I2NP_HEADER_TYPEID_OFFSET] = typeID; };
        uint8_t GetTypeID () const { return GetHeader ()[I2NP_HEADER_TYPEID_OFFSET]; };
        void SetMsgID (uint32_t msgID) { htobe32buf (GetHeader () + I2NP_HEADER_MSGID_OFFSET, msgID); };
        uint32_t GetMsgID () const { return bufbe32toh (GetHeader () + I2NP_HEADER_MSGID_OFFSET); };
        void SetExpiration (uint64_t expiration) { htobe64buf (GetHeader () + I2NP_HEADER_EXPIRATION_OFFSET, expiration); };
        uint64_t GetExpiration () const { return bufbe64toh (GetHeader () + I2NP_HEADER_EXPIRATION_OFFSET); };
        void SetSize (uint16_t size) { htobe16buf (GetHeader () + I2NP_HEADER_SIZE_OFFSET, size); };
        uint16_t GetSize () const { return bufbe16toh (GetHeader () + I2NP_HEADER_SIZE_OFFSET); };
        void UpdateSize () { SetSize (GetPayloadLength ()); };  
        void SetChks (uint8_t chks) { GetHeader ()[I2NP_HEADER_CHKS_OFFSET] = chks; };
        void UpdateChks () 
        {
            uint8_t hash[32];
            CryptoPP::SHA256().CalculateDigest(hash, GetPayload (), GetPayloadLength ());
            GetHeader ()[I2NP_HEADER_CHKS_OFFSET] = hash[0];
        }   
        
        // payload
        uint8_t * GetPayload () { return GetBuffer () + I2NP_HEADER_SIZE; };
        const uint8_t * GetPayload () const { return GetBuffer () + I2NP_HEADER_SIZE; };
        uint8_t * GetBuffer () { return buf + offset; };
        const uint8_t * GetBuffer () const { return buf + offset; };
        size_t GetLength () const { return len - offset; }; 
        size_t GetPayloadLength () const { return GetLength () - I2NP_HEADER_SIZE; };   
            
        void Align (size_t alignment) 
        {
            if (len + alignment > maxLen) return;
            size_t rem = ((size_t)GetBuffer ()) % alignment;
            if (rem)
            {
                offset += (alignment - rem);
                len += (alignment - rem);
            }   
        }

        I2NPMessage& operator=(const I2NPMessage& other)
        {
            memcpy (buf + offset, other.buf + other.offset, other.GetLength ());
            len = offset + other.GetLength ();
            from = other.from;
            maxLen = other.maxLen;
            return *this;
        }   

        // for SSU only
        uint8_t * GetSSUHeader () { return buf + offset + I2NP_HEADER_SIZE - I2NP_SHORT_HEADER_SIZE; }; 
        void FromSSU (uint32_t msgID) // we have received SSU message and convert it to regular
        {
            const uint8_t * ssu = GetSSUHeader ();
            GetHeader ()[I2NP_HEADER_TYPEID_OFFSET] = ssu[I2NP_SHORT_HEADER_TYPEID_OFFSET]; // typeid
            SetMsgID (msgID);
            SetExpiration (bufbe32toh (ssu + I2NP_SHORT_HEADER_EXPIRATION_OFFSET)*1000LL);
            SetSize (len - offset - I2NP_HEADER_SIZE);
            SetChks (0);
        }
        uint32_t ToSSU () // return msgID
        {
            uint8_t header[I2NP_HEADER_SIZE];
            memcpy (header, GetHeader (), I2NP_HEADER_SIZE);
            uint8_t * ssu = GetSSUHeader ();
            ssu[I2NP_SHORT_HEADER_TYPEID_OFFSET] = header[I2NP_HEADER_TYPEID_OFFSET]; // typeid
            htobe32buf (ssu + I2NP_SHORT_HEADER_EXPIRATION_OFFSET, bufbe64toh (header + I2NP_HEADER_EXPIRATION_OFFSET)/1000LL);
            len = offset + I2NP_SHORT_HEADER_SIZE + bufbe16toh (header + I2NP_HEADER_SIZE_OFFSET);
            return bufbe32toh (header + I2NP_HEADER_MSGID_OFFSET);
        }   

        void FillI2NPMessageHeader (I2NPMessageType msgType, uint32_t replyMsgID = 0);
        void RenewI2NPMessageHeader ();
    };  

    template<int sz>
    struct I2NPMessageBuffer: public I2NPMessage
    {
        I2NPMessageBuffer () { buf = m_Buffer; maxLen = sz; };
        uint8_t m_Buffer[sz + 16] = {};
    };

    I2NPMessage * NewI2NPMessage ();
    I2NPMessage * NewI2NPShortMessage ();
    I2NPMessage * NewI2NPMessage (size_t len);
    void DeleteI2NPMessage (I2NPMessage * msg);
    std::shared_ptr<I2NPMessage> ToSharedI2NPMessage (I2NPMessage * msg);
    
    I2NPMessage * CreateI2NPMessage (I2NPMessageType msgType, const uint8_t * buf, int len, uint32_t replyMsgID = 0);   
    std::shared_ptr<I2NPMessage> CreateI2NPMessage (const uint8_t * buf, int len, std::shared_ptr<i2p::tunnel::InboundTunnel> from = nullptr);
    
    std::shared_ptr<I2NPMessage> CreateDeliveryStatusMsg (uint32_t msgID);
    std::shared_ptr<I2NPMessage> CreateRouterInfoDatabaseLookupMsg (const uint8_t * key, const uint8_t * from, 
        uint32_t replyTunnelID, bool exploratory = false, std::set<i2p::data::IdentHash> * excludedPeers = nullptr);
    std::shared_ptr<I2NPMessage> CreateLeaseSetDatabaseLookupMsg (const i2p::data::IdentHash& dest, 
        const std::set<i2p::data::IdentHash>& excludedFloodfills,
        const i2p::tunnel::InboundTunnel * replyTunnel, const uint8_t * replyKey, const uint8_t * replyTag);
    std::shared_ptr<I2NPMessage> CreateDatabaseSearchReply (const i2p::data::IdentHash& ident, std::vector<i2p::data::IdentHash> routers);
    
    std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::RouterInfo> router = nullptr, uint32_t replyToken = 0);
    std::shared_ptr<I2NPMessage> CreateDatabaseStoreMsg (std::shared_ptr<const i2p::data::LeaseSet> leaseSet, uint32_t replyToken = 0);     
        
    bool HandleBuildRequestRecords (int num, uint8_t * records, uint8_t * clearText);
    void HandleVariableTunnelBuildMsg (uint32_t replyMsgID, uint8_t * buf, size_t len);
    void HandleVariableTunnelBuildReplyMsg (uint32_t replyMsgID, uint8_t * buf, size_t len);
    void HandleTunnelBuildMsg (uint8_t * buf, size_t len);  

    I2NPMessage * CreateTunnelDataMsg (const uint8_t * buf);    
    I2NPMessage * CreateTunnelDataMsg (uint32_t tunnelID, const uint8_t * payload);     
    std::shared_ptr<I2NPMessage> CreateEmptyTunnelDataMsg ();
    
    I2NPMessage * CreateTunnelGatewayMsg (uint32_t tunnelID, const uint8_t * buf, size_t len);
    I2NPMessage * CreateTunnelGatewayMsg (uint32_t tunnelID, I2NPMessageType msgType, 
        const uint8_t * buf, size_t len, uint32_t replyMsgID = 0);
    std::shared_ptr<I2NPMessage> CreateTunnelGatewayMsg (uint32_t tunnelID, std::shared_ptr<I2NPMessage> msg);

    size_t GetI2NPMessageLength (const uint8_t * msg);
    void HandleI2NPMessage (uint8_t * msg, size_t len);
    void HandleI2NPMessage (std::shared_ptr<I2NPMessage> msg);

    class I2NPMessagesHandler
    {
        public:

            ~I2NPMessagesHandler ();
            void PutNextMessage (std::shared_ptr<I2NPMessage> msg);
            void Flush ();
            
        private:

            std::vector<std::shared_ptr<I2NPMessage> > m_TunnelMsgs, m_TunnelGatewayMsgs;
    };
}   

#endif