Datagram.cpp

#include <string.h>
#include <vector>
#include <cryptopp/sha.h>
#include <cryptopp/gzip.h>
#include "util/Log.h"
#include "tunnel/TunnelBase.h"
#include "RouterContext.h"
#include "Destination.h"
#include "Datagram.h"

namespace i2p
{
namespace datagram
{
    DatagramDestination::DatagramDestination (i2p::client::ClientDestination& owner): 
        m_Owner (owner), m_Receiver (nullptr)
    {
    }
        
    void DatagramDestination::SendDatagramTo (const uint8_t * payload, size_t len, const i2p::data::IdentHash& ident, uint16_t fromPort, uint16_t toPort)
    {
        uint8_t buf[MAX_DATAGRAM_SIZE];
        auto identityLen = m_Owner.GetIdentity ().ToBuffer (buf, MAX_DATAGRAM_SIZE);
        uint8_t * signature = buf + identityLen;
        auto signatureLen = m_Owner.GetIdentity ().GetSignatureLen ();
        uint8_t * buf1 = signature + signatureLen;
        size_t headerLen = identityLen + signatureLen;
        
        memcpy (buf1, payload, len);    
        if (m_Owner.GetIdentity ().GetSigningKeyType () == i2p::data::SIGNING_KEY_TYPE_DSA_SHA1)
        {
            uint8_t hash[32];   
            CryptoPP::SHA256().CalculateDigest (hash, buf1, len);
            m_Owner.Sign (hash, 32, signature);
        }
        else
            m_Owner.Sign (buf1, len, signature);

        auto msg = CreateDataMessage (buf, len + headerLen, fromPort, toPort); 
        auto remote = m_Owner.FindLeaseSet (ident);
        if (remote)
            m_Owner.GetService ().post (std::bind (&DatagramDestination::SendMsg, this, msg, remote));
        else
            m_Owner.RequestDestination (ident, std::bind (&DatagramDestination::HandleLeaseSetRequestComplete, this, std::placeholders::_1, msg));
    }

    void DatagramDestination::HandleLeaseSetRequestComplete (std::shared_ptr<i2p::data::LeaseSet> remote, I2NPMessage * msg)
    {
        if (remote)
            SendMsg (msg, remote);
        else
            DeleteI2NPMessage (msg);
    }   
        
    void DatagramDestination::SendMsg (I2NPMessage * msg, std::shared_ptr<const i2p::data::LeaseSet> remote)
    {
        auto outboundTunnel = m_Owner.GetTunnelPool ()->GetNextOutboundTunnel ();
        auto leases = remote->GetNonExpiredLeases ();
        if (!leases.empty () && outboundTunnel)
        {
            std::vector<i2p::tunnel::TunnelMessageBlock> msgs;          
            uint32_t i = i2p::context.GetRandomNumberGenerator ().GenerateWord32 (0, leases.size () - 1);
            auto garlic = m_Owner.WrapMessage (remote, ToSharedI2NPMessage (msg), true);
            msgs.push_back (i2p::tunnel::TunnelMessageBlock 
                { 
                    i2p::tunnel::eDeliveryTypeTunnel,
                    leases[i].tunnelGateway, leases[i].tunnelID,
                    garlic
                });
            outboundTunnel->SendTunnelDataMsg (msgs);
        }
        else
        {
            if (outboundTunnel)
                LogPrint (eLogWarning, "Failed to send datagram. All leases expired");
            else
                LogPrint (eLogWarning, "Failed to send datagram. No outbound tunnels");
            DeleteI2NPMessage (msg);    
        }   
    }

    void DatagramDestination::HandleDatagram (uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
    {
        i2p::data::IdentityEx identity;
        size_t identityLen = identity.FromBuffer (buf, len);
        const uint8_t * signature = buf + identityLen;
        size_t headerLen = identityLen + identity.GetSignatureLen ();

        bool verified = false;
        if (identity.GetSigningKeyType () == i2p::data::SIGNING_KEY_TYPE_DSA_SHA1)
        {
            uint8_t hash[32];
            CryptoPP::SHA256().CalculateDigest (hash, buf + headerLen, len - headerLen);
            verified = identity.Verify (hash, 32, signature);
        }   
        else    
            verified = identity.Verify (buf + headerLen, len - headerLen, signature);
                
        if (verified)
        {
            auto it = m_ReceiversByPorts.find (toPort);
            if (it != m_ReceiversByPorts.end ())
                it->second (identity, fromPort, toPort, buf + headerLen, len -headerLen);
            else if (m_Receiver != nullptr)
                m_Receiver (identity, fromPort, toPort, buf + headerLen, len -headerLen);
            else
                LogPrint (eLogWarning, "Receiver for datagram is not set"); 
        }
        else
            LogPrint (eLogWarning, "Datagram signature verification failed");   
    }

    void DatagramDestination::HandleDataMessagePayload (uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
    {
        // unzip it
        CryptoPP::Gunzip decompressor;
        decompressor.Put (buf, len);
        decompressor.MessageEnd();
        uint8_t uncompressed[MAX_DATAGRAM_SIZE];
        auto uncompressedLen = decompressor.MaxRetrievable ();
        if (uncompressedLen <= MAX_DATAGRAM_SIZE)
        {
            decompressor.Get (uncompressed, uncompressedLen);
            HandleDatagram (fromPort, toPort, uncompressed, uncompressedLen); 
        }
        else
            LogPrint ("Received datagram size ", uncompressedLen,  " exceeds max size");

    }

    I2NPMessage * DatagramDestination::CreateDataMessage (const uint8_t * payload, size_t len, uint16_t fromPort, uint16_t toPort)
    {
        I2NPMessage * msg = NewI2NPMessage ();
        CryptoPP::Gzip compressor; // default level
        compressor.Put (payload, len);
        compressor.MessageEnd();
        int size = compressor.MaxRetrievable ();
        uint8_t * buf = msg->GetPayload ();
        htobe32buf (buf, size); // length
        buf += 4;
        compressor.Get (buf, size);
        htobe16buf (buf + 4, fromPort); // source port
        htobe16buf (buf + 6, toPort); // destination port 
        buf[9] = i2p::client::PROTOCOL_TYPE_DATAGRAM; // datagram protocol
        msg->len += size + 4; 
        msg->FillI2NPMessageHeader (eI2NPData);
        return msg;
    }   
}
}