wechat_hitxy/server.go

package main

import (
	"crypto/sha1"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"sort"
	"strings"
)

//apiV1Main  version 1 main entry for all wechat callbacks
//
func apiV1Main(w http.ResponseWriter, r *http.Request) {
	logRequestDebug(httputil.DumpRequest(r, true))
	if checkSignature(r) == false {
		log.Println("signature of URL incorrect")
		w.Header().Set("Content-Type", "text/xml; charset=utf-8")
		w.WriteHeader(http.StatusUnauthorized)
		fmt.Fprintf(w, "") //empty string
		return
	}

	switch r.Method {
	case "POST":
		//answerWechatPostEcho(w, r)
		answerWechatPost(w, r)
	case "GET":
		answerInitialAuth(w, r)
	default:
		log.Fatalln(fmt.Sprintf("Unhandled HTTP %s", r.Method))
		fmt.Fprintf(w, "Protocol Error: Expect GET or POST only")
	}
}

//
//answerInitialAuth,  when wechat first verify our URL for API hooks
//
func answerInitialAuth(w http.ResponseWriter, r *http.Request) {
	rq := r.URL.RawQuery
	m, _ := url.ParseQuery(rq)

	echostr, eok := m["echostr"]
	if checkSignature(r) && eok {
		fmt.Fprintf(w, echostr[0])
	} else {
		fmt.Fprintf(w, "wtf is wrong with the Internet")
	}
}

//answerWechatPost  distribute PostRequest according to xml body info
//
func answerWechatPost(w http.ResponseWriter, r *http.Request) {
	body, _ := ioutil.ReadAll(r.Body)
	d := decryptToXML(string(body))
	fmt.Printf("decrypt as: %s\n", d)
	h := ReadCommonHeader(d)
	reply, _ := BuildTextMsg(h.MsgType, h.FromUserName)
	if h.MsgType == "voice" {
		a := ReadVoiceMsg(d)
		reply, _ = BuildTextMsg(a.Recognition, h.FromUserName)
	}
	if h.MsgType == "event" {
		a := ReadEventMsg(d)
		reply, _ = BuildTextMsg(a.Event+"/"+a.EventKey, h.FromUserName)
	}
	w.Header().Set("Content-Type", "text/xml; charset=utf-8")
	fmt.Fprint(w, reply)
	return
}

func answerWechatPostEcho(w http.ResponseWriter, r *http.Request) {
	body, _ := ioutil.ReadAll(r.Body)
	//fmt.Printf("get body: %s", string(body))
	s := ReadEncryptedMsg(string(body))
	//fmt.Printf("to decrypt %s", s.Encrypt)
	d := Decode(s.Encrypt)
	fmt.Printf("echo as: \n%s", d)

	e := strings.Replace(d, "ToUserName", "FDDD20170506xyzunique", 2)
	f := strings.Replace(e, "FromUserName", "ToUserName", 2)
	g := strings.Replace(f, "FDDD20170506xyzunique", "FromUserName", 2)
	fmt.Fprint(w, g)
}

//
func checkSignature(r *http.Request) bool {
	rq := r.URL.RawQuery
	m, _ := url.ParseQuery(rq)

	signature, sok := m["signature"]
	timestamp, tok := m["timestamp"]
	nonce, nok := m["nonce"]
	token := APIConfig.Token
	if sok && tok && nok {
		//sort token, timestamp, nonce  and join them
		strs := []string{token, timestamp[0], nonce[0]}
		sort.Strings(strs)
		s := strings.Join(strs, "")

		//calculate sha1
		h := sha1.New()
		h.Write([]byte(s))
		calculated := fmt.Sprintf("%x", h.Sum(nil))
		return signature[0] == calculated
	}
	return false
}

func checkSignature1() bool {
	s1 := "e39de9f2e28079c01ebb4b803dfc3442b819545c"
	t1 := "1492970761"
	n1 := "1850971833"
	token := APIConfig.Token

	strs := []string{token, t1, n1}
	sort.Strings(strs)
	s := strings.Join(strs, "")

	h := sha1.New()
	h.Write([]byte(s))
	us := fmt.Sprintf("%x", h.Sum(nil))
	return s1 == us
}

//webrootHandler sending contents to client when request "/"
//      essentially to prove the webserver is still alive
//      echo query string to the client
func webrootHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
	rq := r.URL.RawQuery
	m, _ := url.ParseQuery(rq)
	for index, element := range m {
		fmt.Fprintf(w, "\n%s => %s", index, element)
	}
	logRequestDebug(httputil.DumpRequest(r, true))

}

func logRequestDebug(data []byte, err error) {
	if err == nil {
		fmt.Printf("%s\n\n", data)
	} else {
		log.Fatalf("%s\n\n", err)
	}
}