Go Pentester - HTTP Servers(1)

HTTP Server Basics

Use net/http package and useful third-party packages by building simple servers.

Building a Simple Server

package main

import (
	"fmt"
	"net/http"
)

func hello(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hello %s\n", r.URL.Query().Get("name"))
}

func main() {
	http.HandleFunc("/hello", hello)
	http.ListenAndServe(":8000",nil)
}

Run the above program and test it.

curl -i http://localhost:8000/hello?name=eric

You can also use http.ListenAndServeTLS(), which will start a server using HTTPS and TLS.

Build a Simple Router

package main

import (
	"fmt"
	"net/http"
)

type router struct {
}

func (r *router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	switch req.URL.Path {
	case "/a":
		fmt.Fprintf(w, "Executing /a\n")
	case "/b":
		fmt.Fprintf(w, "Executing /b\n")
	case "/c":
		fmt.Fprintf(w, "Executing /c\n")
	default:
		http.Error(w, "404 Not Found", 404)
	}
}

func main() {
	var r router
	http.ListenAndServe(":8000", &r)
}

Test the above program by the following commands.

curl http://localhost:8000/a
curl http://localhost:8000/d

Building simple Middleware

A simple middleware, which is a sort of wrapper that will execute on all incoming requests regardless of the destination function.

package main

import (
	"fmt"
	"log"
	"net/http"
	"time"
)

type logger struct {
	Inner http.Handler
}

func (l *logger) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	log.Printf("start %s\n", time.Now().String())
	l.Inner.ServeHTTP(w,r)
	log.Printf("finish %s",time.Now().String())
}

func hello(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, "Hello\n")
}

func main() {
	f := http.HandlerFunc(hello)
	l := logger{Inner: f}
	http.ListenAndServe(":8000", &l)
}

Run the program and issue a request.

curl http://localhost:8000