Gorilla Mux w/ GitHub authentication

goriall-mux-github-auth

package main

import (
	"flag"
	"log"
	"net/http"
	"os"

	"github.com/gorilla/mux"
	"github.com/stretchr/gomniauth"
	"github.com/stretchr/gomniauth/providers/github"
	"github.com/stretchr/objx"
	"github.com/stretchr/signature"
)

var addr = flag.String("listen", getEnv("APP_LISTEN", ":3000"), "Address:port on which to listen")
var id = flag.String("oauth-id", getEnv("APP_OAUTH_ID", "xxxx"), "OAuth ID")
var secret = flag.String("oauth-secret", getEnv("APP_OAUTH_SECRET", "xxxx"), "OAuth secret")

func main() {
	flag.Parse()

	gomniauth.SetSecurityKey(signature.RandomKey(64))
	gomniauth.WithProviders(
		github.New(*id, *secret, "http://localhost:3000/auth/callback"),
	)

	router := mux.NewRouter()
	router.HandleFunc("/", homeCallback).Methods("GET")
	router.HandleFunc("/login", loginCallback).Methods("GET")
	router.HandleFunc("/auth/callback", authCallback).Methods("GET")
	router.HandleFunc("/hello/{name:[a-z]+}", nameCallback).Methods("GET")

	http.Handle("/", router)

	log.Println("Listening on ", *addr)
	http.ListenAndServe(*addr, nil)
}

// Callback for the homepage (/)
func homeCallback(res http.ResponseWriter, req *http.Request) {
	res.Write([]byte("Hello world!"))
}

// Callback for the name (/hello/{name:[a-z]+})
func nameCallback(res http.ResponseWriter, req *http.Request) {
	params := mux.Vars(req)
	name := params["name"]
	res.Write([]byte("Hello " + name))
}

// Login callback that auths against GitHub. See the example at
// https://github.com/stretchr/gomniauth/blob/master/example/goweb/main.go
// for the raw code this function was adapted from.
func loginCallback(res http.ResponseWriter, req *http.Request) {
	provider, err := gomniauth.Provider("github")

	if err != nil {
		log.Println(err)
		return
	}

	state := gomniauth.NewState("after", "success")

	authUrl, err := provider.GetBeginAuthURL(state, nil)

	if err != nil {
		log.Println(err)
		return
	}

	http.Redirect(res, req, authUrl, http.StatusFound)
}

// Oauth callback that GitHub redirects back to with creds. See the example at
// https://github.com/stretchr/gomniauth/blob/master/example/goweb/main.go
// for the raw code this function was adapted from.
func authCallback(res http.ResponseWriter, req *http.Request) {
	provider, err := gomniauth.Provider("github")

	if err != nil {
		log.Println(err)
		return
	}

	m := make(objx.Map)
	for k, vs := range req.URL.Query() {
		m.Set(k, vs)
	}

	creds, err := provider.CompleteAuth(m)

	if err != nil {
		log.Println(err)
		return
	}

	// load the user
	_, err := provider.GetUser(creds)

	if userErr != nil {
		log.Println(err)
		return
	}

	res.Write([]byte("OK"))
}

// Helper function that reads an environment variable and
// returns a default value if the variable isn't set.
func getEnv(env string, def string) string {
	val := os.Getenv(env)
	if len(val) != 0 {
		return val
	} else {
		return def
	}
}