A simple TCP honeypot written in Go. Usage: "go run goneypot.go <port>" or build a binary and run it specifying a port.

goneypot.go

package main

import (
	"bytes"
	"log"
	"net"
	"os"
)

// Connection handler
func handleConn(conn net.Conn) {
	log.Printf("Received connection from %s\n", conn.RemoteAddr())

	// Read buffer from connection
	buff := make([]byte, 1024)
	nbytes, err := conn.Read(buff)
	if err != nil {
		log.Println("Error reading from connection. ", err)
	}

	// Reply with a fake unauthorized message
	headers := "HTTP/1.0 401 Unauthorized\nServer: Apache/2.4.44 (Ubuntu) Server\n\n"
	fakeMsg := headers + "401 Unauthorized access.\n"
	conn.Write([]byte(fakeMsg))

	// Log request
	trimmedOutput := bytes.TrimRight(buff, "\x00")
	log.Printf("Read %d bytes from %s\n%s\n",
		nbytes, conn.RemoteAddr(), trimmedOutput)
	conn.Close()
}

func main() {

	// Check args
	if len(os.Args) != 2 {
		log.Fatalf("Usage: ./%s <port>", os.Args[0])
		return
	}

	// Vars
	var (
		ip       string = "localhost"
		port     string = os.Args[1]
		endpoint string = ip + ":" + port
	)

	// Set log file
	logFile, err := os.OpenFile("logs.log", os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
	if err != nil {
		log.Fatal(err)
	}
	defer logFile.Close()
	log.SetOutput(logFile)

	// TCP Listener
	ln, err := net.Listen("tcp", endpoint)
	if err != nil {
		log.Fatalf("Error listening on port %s\n%s\n", port, err.Error())
	}

	log.Printf("Listening on port %s.\n", port)
	for {
		conn, err := ln.Accept()
		if err != nil {
			log.Println("Error accepting connection.", err)
		}
		go handleConn(conn)
	}
}