elec0017_project/server/server.go

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"net"
)

var aes_key = "03020100070605040b0a09080f0e0d0c"


func serveConnection(conn net.Conn) {
	defer logPanic()
	defer conn.Close()
	fmt.Printf("Connection from %s\n", conn.RemoteAddr().String())
	decoded, _ := hex.DecodeString(aes_key)
	buf := make([]byte, 4)
	for {
		_, err := conn.Read(buf)
		errCheckPanic(err, "Connection failed with %s", conn.RemoteAddr().String())
		id := binary.LittleEndian.Uint16(buf[:2])
		msglen := binary.LittleEndian.Uint16(buf[2:])
		fmt.Printf("Connection from ID %d message length %d\n %x\n", id, msglen, buf)
		payload := make([]byte, msglen)
		_, err = conn.Read(payload)
		errCheckPanic(err, "Connection failed %s device #%d", conn.RemoteAddr().String(), id)
		fmt.Printf("Payload: %x\n", payload)
		message := make([]byte, msglen-16)
		block, err := aes.NewCipher(decoded)
		errCheckPanic(err, "Decryption failed %s device #%d", conn.RemoteAddr().String(), id)
		mode := cipher.NewCBCDecrypter(block, payload[:16])
		mode.CryptBlocks(message, payload[16:])
		fmt.Printf("Message: %s\n", string(message))
	}

}

func serve(address string) {
	ln, err := net.Listen("tcp", address)
	errCheckExit(err,"Failed accept connection")

	defer ln.Close()
	fmt.Printf("Service socket ready at %s\n", address)

	for {
		conn, err := ln.Accept()
		errCheckExit(err,"Failed accept connection %s", conn.RemoteAddr().String())
		go serveConnection(conn)
	}

}