netgiv/server.go

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"sync/atomic"
	"time"

	"github.com/h2non/filetype"

	"github.com/tardisx/netgiv/secure"
)

type Server struct {
	port int
}

// An NGF is a Netgiv File
type NGF struct {
	Id        uint32
	StorePath string
	Filename  string // could be empty string if we were not supplied with one
	Kind      string //
	Size      uint64 // file size
}

var ngfs []NGF
var globalId uint32

func (s *Server) Run() {
	address := fmt.Sprintf(":%d", s.port)
	networkAddress, _ := net.ResolveTCPAddr("tcp", address)

	listener, err := net.ListenTCP("tcp", networkAddress)
	if err != nil {
		fmt.Print(err)
		os.Exit(2)
	}

	ngfs = make([]NGF, 0)

	for {
		conn, err := listener.AcceptTCP()

		if err != nil {
			fmt.Print(err)
		}

		go handleConnection(conn)
	}
}

func handleConnection(conn *net.TCPConn) {
	defer conn.Close()

	conn.SetDeadline(time.Now().Add(time.Second * 5))

	sharedKey := secure.Handshake(conn)
	secureConnection := secure.SecureConnection{Conn: conn, SharedKey: sharedKey, Buffer: &bytes.Buffer{}}

	gob.Register(secure.PacketStart{})
	gob.Register(secure.PacketSendDataStart{})

	dec := gob.NewDecoder(&secureConnection)
	enc := gob.NewEncoder(&secureConnection)

	// Get the start packet
	start := secure.PacketStart{}

	err := dec.Decode(&start)
	if err == io.EOF {
		log.Printf("connection has been closed prematurely")
		return
	}
	if err != nil {
		log.Printf("error while expecting PacketStart: %v", err)
		return
	}

	conn.SetDeadline(time.Now().Add(time.Second * 5))

	if start.OperationType == secure.OperationTypeSend {
		log.Printf("file incoming")

		sendStart := secure.PacketSendDataStart{}

		err = dec.Decode(&sendStart)
		if err != nil {
			log.Printf("error - expecting PacketSendDataStart: %v", err)
			return
		}
		file, err := os.CreateTemp("", "netgiv_")
		if err != nil {
			log.Fatalf("can't open tempfile: %v", err)
		}
		defer file.Close()

		ngf := NGF{
			StorePath: file.Name(),
			Filename:  sendStart.Filename,
			Kind:      "",
			Size:      0,
			Id:        atomic.AddUint32(&globalId, 1),
		}

		if err != nil {
			log.Printf("got error with temp file: %w", err)
			return
		}
		sendData := secure.PacketSendDataNext{}
		determinedKind := false
		for {
			conn.SetDeadline(time.Now().Add(time.Second * 5))
			err = dec.Decode(&sendData)
			if err == io.EOF {
				break
			}
			if err != nil {
				log.Printf("error while expecting PacketSendDataNext: %s", err)
				return
			}

			// filetype.Match needs a few hundred bytes - I guess there is a chance
			// we don't have enough in the very first packet? This might need rework.
			if !determinedKind {
				kind, _ := filetype.Match(sendData.Data)
				ngf.Kind = kind.MIME.Value
				determinedKind = true
			}

			file.Write(sendData.Data)
		}
		info, err := file.Stat()
		if err != nil {
			log.Printf("couldn't stat file %s", err)
			return
		}
		ngf.Size = uint64(info.Size())
		file.Close()

		ngfs = append(ngfs, ngf)
		log.Printf("done receiving file")

		return
	} else if start.OperationType == secure.OperationTypeList {
		log.Printf("client requesting file list")

		for _, ngf := range ngfs {
			p := secure.PacketListData{}
			p.FileSize = uint32(ngf.Size)
			p.Kind = ngf.Kind
			p.Id = ngf.Id
			p.Filename = ngf.Filename
			enc.Encode(p)
		}
		log.Printf("done sending list, closing connection")

		return

	} else {
		log.Printf("bad operation")
		return
	}

}