example oauth-google

readme.md

from https://dev.to/douglasmakey/oauth2-example-with-go-3n8a

example of "enable API" button https://cloud.google.com/resource-manager/docs/creating-managing-projects#api_1

example of "enable API" button https://cloud.google.com/resource-manager/reference/rest/v1/projects/create?hl=th

oauth 2 client https://cloud.google.com/docs/authentication#oauth-2.0-clients

oauth 2 webserver https://developers.google.com/identity/protocols/oauth2/web-server?hl=th

link for create Start project & set credential type

https://console.developers.google.com/henhouse/?pb=%5B%22hh-0%22,%22drive%22,null,%5B%5D,%22https:%2F%2Fdevelopers.google.com%22,null,%5B%5D,null,%22Enable%20the%20Drive%20API%22,1,null,%5B%5D,false,false,null,null,null,null,false,null,false,false,null,null,null,%22DESKTOP%22,null,%22Quickstart%22,true,%22Quickstart%22,null,null,false%5D

https://console.developers.google.com/henhouse/?pb=%5B%22hh-0%22,%22drive%22,null,%5B%5D,%22https:%2F%2Fdevelopers.google.com%22,null,%5B%5D,null,%22Enable%20the%20Drive%20API%22,1,null,%5B%5D,false,false,null,null,null,null,false,null,false,false,null,null,null,%22WEB_SERVER%22,null,%22Quickstart%22,true,%22Quickstart%22,null,null,false%5D

• create project (with google login for gate auth key) ( https://cloud.google.com/resource-manager/docs/creating-managing-projects#api_1 )

• then use Oauth2.0 with client ID method for get credential for use Drive API ( https://cloud.google.com/docs/authentication?_ga=2.88793183.-554737446.1609815827&_gac=1.95650542.1613348762.CjwKCAiAsaOBBhA4EiwAo0_AnHXu0Yj-CiAek1wyni3NpBTCm1JdCyRRLAtemjW1zQEIm4urfrrekxoCZ4AQAvD_BwE#oauth-2.0-clients )

base-oauth2-google.go

package handlers

import (
    "net/http"
)

func New() http.Handler {
    mux := http.NewServeMux()
    // Root
    mux.Handle("/",  http.FileServer(http.Dir("templates/")))

    // OauthGoogle
    mux.HandleFunc("/auth/google/login", oauthGoogleLogin)
    mux.HandleFunc("/auth/google/callback", oauthGoogleCallback)

    return mux
}

main.go

package main

import (
    "fmt"
    "net/http"
    "log"
    "github.com/douglasmakey/oauth2-example/handlers"
)

func main() {
    server := &http.Server{
        Addr: fmt.Sprintf(":8000"),
        Handler: handlers.New(),
    }

    log.Printf("Starting HTTP Server. Listening at %q", server.Addr)
    if err := server.ListenAndServe(); err != http.ErrServerClosed {
        log.Printf("%v", err)
    } else {
        log.Println("Server closed!")
    }
}

oauth_google.go

package handlers

import (
    "golang.org/x/oauth2"
    "golang.org/x/oauth2/google"
    "net/http"
    "fmt"
    "io/ioutil"
    "context"
    "log"
    "encoding/base64"
    "crypto/rand"
    "os"
    "time"
)

// Scopes: OAuth 2.0 scopes provide a way to limit the amount of access that is granted to an access token.
// for drive access scope = https://www.googleapis.com/auth/drive.file	
// list of all scope = https://developers.google.com/identity/protocols/oauth2/scopes#drive
var googleOauthConfig = &oauth2.Config{
    RedirectURL:  "http://localhost:8000/auth/google/callback",
    ClientID:     os.Getenv("GOOGLE_OAUTH_CLIENT_ID"),
    ClientSecret: os.Getenv("GOOGLE_OAUTH_CLIENT_SECRET"),
    Scopes:       []string{"https://www.googleapis.com/auth/userinfo.email"},
    Endpoint:     google.Endpoint,
}

const oauthGoogleUrlAPI = "https://www.googleapis.com/oauth2/v2/userinfo?access_token="

func oauthGoogleLogin(w http.ResponseWriter, r *http.Request) {

    // Create oauthState cookie
    oauthState := generateStateOauthCookie(w)

    /*
    AuthCodeURL receive state that is a token to protect the user from CSRF attacks. You must always provide a non-empty string and
    validate that it matches the the state query parameter on your redirect callback.
    */
    u := googleOauthConfig.AuthCodeURL(oauthState)
    http.Redirect(w, r, u, http.StatusTemporaryRedirect)
}

func oauthGoogleCallback(w http.ResponseWriter, r *http.Request) {
    // Read oauthState from Cookie
    oauthState, _ := r.Cookie("oauthstate")

    if r.FormValue("state") != oauthState.Value {
        log.Println("invalid oauth google state")
        http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
        return
    }

    data, err := getUserDataFromGoogle(r.FormValue("code"))
    if err != nil {
        log.Println(err.Error())
        http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
        return
    }

    // GetOrCreate User in your db.
    // Redirect or response with a token.
    // More code .....
    fmt.Fprintf(w, "UserInfo: %s\n", data)
}

func generateStateOauthCookie(w http.ResponseWriter) string {
    var expiration = time.Now().Add(365 * 24 * time.Hour)

    b := make([]byte, 16)
    rand.Read(b)
    state := base64.URLEncoding.EncodeToString(b)
    cookie := http.Cookie{Name: "oauthstate", Value: state, Expires: expiration}
    http.SetCookie(w, &cookie)

    return state
}

func getUserDataFromGoogle(code string) ([]byte, error) {
    // Use code to get token and get user info from Google.

    token, err := googleOauthConfig.Exchange(context.Background(), code)
    if err != nil {
        return nil, fmt.Errorf("code exchange wrong: %s", err.Error())
    }
    response, err := http.Get(oauthGoogleUrlAPI + token.AccessToken)
    if err != nil {
        return nil, fmt.Errorf("failed getting user info: %s", err.Error())
    }
    defer response.Body.Close()
    contents, err := ioutil.ReadAll(response.Body)
    if err != nil {
        return nil, fmt.Errorf("failed read response: %s", err.Error())
    }
    return contents, nil
}