# 14.4 User validation

In the process of developing web applications, user authentication is a problem which developers frequently encounter. User login, registration and logout, among other operations, as well as general authentication can be divided into three parts: 

- HTTP Basic, and HTTP Digest Authentication
- Third Party Authentication Integration: QQ, micro-blogging, watercress, OPENID, Google, GitHub, Facebook and twitter, etc.
- Custom user login, registration, logout, are generally based on sessions and cookie authentication

Beego does not natively provide support for any of these three things, however you can easily make use of existing third party open source libraries to implement them. The first two authentication solutions are on Beego's roadmap to eventually be integrated. 

## HTTP basic and digest authentication

Both HTTP basic and digest authentication are relatively simple techniques commonly used by web applications. There are already many open source third-party libraries which support these two authentication methods, such as:

	github.com/abbot/go-http-auth

The following code demonstrates how to use this library to implement authentication in a Beego application: 

	package controllers
	
	import (
		"github.com/abbot/go-http-auth"
		"github.com/astaxie/beego"
	)
	
	func Secret(user, realm string) string {
		if user == "john" {
			// password is "hello"
			return "$1$dlPL2MqE$oQmn16q49SqdmhenQuNgs1"
		}
		return ""
	}
	
	type MainController struct {
		beego.Controller
	}
	
	func (this *MainController) Prepare() {
		a := auth.NewBasicAuthenticator("example.com", Secret)
		if username := a.CheckAuth(this.Ctx.Request); username == "" {
			a.RequireAuth(this.Ctx.ResponseWriter, this.Ctx.Request)
		}
	}
	
	func (this *MainController) Get() {
		this.Data["Username"] = "astaxie"
		this.Data["Email"] = "astaxie@gmail.com"
		this.TplNames = "index.tpl"
	}

The above code takes advantage of Beego's `prepare()` function to perform authentication before allowing the normal flow of execution to proceed; as you can see, it's very simple to implement HTTP authentication. Digest authentication can be implemented in much the same way.

## OAuth and OAuth 2 authentication

OAuth and OAuth 2 are currently two of the most popular authentication methods. Fortunately, there are third-party libraries which implement this type of authentication such as the `go.auth` package available on github.

	github.com/bradrydzewski/go.auth

The code below demonstrates how to use this library to implement OAuth authentication in Beego using our Github credentials:

1. Let's add some routes 

		beego.RegisterController("/auth/login", &controllers.GithubController{})
		beego.RegisterController("/mainpage", &controllers.PageController{})

2. Then we deal with the `GithubController` landing page:

		package controllers
			
		import (
			"github.com/astaxie/beego"
			"github.com/bradrydzewski/go.auth"
		)
		
		const (
			githubClientKey = "a0864ea791ce7e7bd0df"
			githubSecretKey = "a0ec09a647a688a64a28f6190b5a0d2705df56ca"
		)
		
		type GithubController struct {
			beego.Controller
		}
		
		func (this *GithubController) Get() {
			// set the auth parameters
			auth.Config.CookieSecret = []byte("7H9xiimk2QdTdYI7rDddfJeV")
			auth.Config.LoginSuccessRedirect = "/mainpage"
			auth.Config.CookieSecure = false
		
			githubHandler := auth.Github(githubClientKey, githubSecretKey)
		
			githubHandler.ServeHTTP(this.Ctx.ResponseWriter, this.Ctx.Request)
		}

3. Handling after a successful landing page:

		package controllers
		
		import (
			"github.com/astaxie/beego"
			"github.com/bradrydzewski/go.auth"
			"net/http"
			"net/url"
		)
		
		type PageController struct {
			beego.Controller
		}
		
		func (this *PageController) Get() {
			// set the auth parameters
			auth.Config.CookieSecret = []byte("7H9xiimk2QdTdYI7rDddfJeV")
			auth.Config.LoginSuccessRedirect = "/mainpage"
			auth.Config.CookieSecure = false
		
			user, err := auth.GetUserCookie(this.Ctx.Request)
		
			//if no active user session then authorize user
			if err != nil || user.Id() == "" {
				http.Redirect(this.Ctx.ResponseWriter, this.Ctx.Request, auth.Config.LoginRedirect, http.StatusSeeOther)
				return
			}
		
			//else, add the user to the URL and continue
			this.Ctx.Request.URL.User = url.User(user.Id())
			this.Data["pic"] = user.Picture()
			this.Data["id"] = user.Id()
			this.Data["name"] = user.Name()
			this.TplNames = "home.tpl"
		}

The whole process is as follows: 

first open your browser and enter the address:

![](images/14.4.github.png?raw=true)

Figure 14.4 shows the home page with a login button

When clicking on the link, the following screen appears:

![](images/14.4.github2.png?raw=true)

Figure 14.5 displayed after clicking the login button to authenticate with your GitHub credentials

After clicking "Authorize app", the following screen appears:

![](images/14.4.github3.png?raw=true)

Figure 14.6 authorized Github information gets displayed after the login page

## Custom authentication

Custom authentication is generally combined with session authentication; the following code is a Beego based open source blog which demonstrates this: 

	//Login process
	func (this *LoginController) Post() {
		this.TplNames = "login.tpl"
		this.Ctx.Request.ParseForm()
		username := this.Ctx.Request.Form.Get("username")
		password := this.Ctx.Request.Form.Get("password")
		md5Password := md5.New()
		io.WriteString(md5Password, password)
		buffer := bytes.NewBuffer(nil)
		fmt.Fprintf(buffer, "%x", md5Password.Sum(nil))
		newPass := buffer.String()
	
		now := time.Now().Format("2006-01-02 15:04:05")
	
		userInfo := models.GetUserInfo(username)
		if userInfo.Password == newPass {
			var users models.User
			users.Last_logintime = now
			models.UpdateUserInfo(users)
	
			//Set the session successful login
			sess := globalSessions.SessionStart(this.Ctx.ResponseWriter, this.Ctx.Request)
			sess.Set("uid", userInfo.Id)
			sess.Set("uname", userInfo.Username)
	
			this.Ctx.Redirect(302, "/")
		}	
	}
	
	//Registration process
	func (this *RegController) Post() {
		this.TplNames = "reg.tpl"
		this.Ctx.Request.ParseForm()
		username := this.Ctx.Request.Form.Get("username")
		password := this.Ctx.Request.Form.Get("password")
		usererr := checkUsername(username)
		fmt.Println(usererr)
		if usererr == false {
			this.Data["UsernameErr"] = "Username error, Please to again"
			return
		}
	
		passerr := checkPassword(password)
		if passerr == false {
			this.Data["PasswordErr"] = "Password error, Please to again"
			return
		}
	
		md5Password := md5.New()
		io.WriteString(md5Password, password)
		buffer := bytes.NewBuffer(nil)
		fmt.Fprintf(buffer, "%x", md5Password.Sum(nil))
		newPass := buffer.String()
	
		now := time.Now().Format("2006-01-02 15:04:05")
	
		userInfo := models.GetUserInfo(username)
	
		if userInfo.Username == "" {
			var users models.User
			users.Username = username
			users.Password = newPass
			users.Created = now
			users.Last_logintime = now
			models.AddUser(users)
	
			//Set the session successful login
			sess := globalSessions.SessionStart(this.Ctx.ResponseWriter, this.Ctx.Request)
			sess.Set("uid", userInfo.Id)
			sess.Set("uname", userInfo.Username)
			this.Ctx.Redirect(302, "/")
		} else {
			this.Data["UsernameErr"] = "User already exists"
		}
	
	}
	
	func checkPassword(password string) (b bool) {
		if ok, _ := regexp.MatchString("^[a-zA-Z0-9]{4,16}$", password); !ok {
			return false
		}
		return true
	}
	
	func checkUsername(username string) (b bool) {
		if ok, _ := regexp.MatchString("^[a-zA-Z0-9]{4,16}$", username); !ok {
			return false
		}
		return true
	}

Once you have implemented user login and registration, other modules can be added to determine whether the user has been logged in or not: 

	func (this *AddBlogController) Prepare() {
		sess := globalSessions.SessionStart(this.Ctx.ResponseWriter, this.Ctx.Request)
		sess_uid := sess.Get("userid")
		sess_username := sess.Get("username")
		if sess_uid == nil {
			this.Ctx.Redirect(302, "/admin/login")
			return
		}
		this.Data["Username"] = sess_username
	}

## Links

- [Directory](preface.md)
- Previous section: [Form](14.3.md)
- Next section: [Multi-language support](14.5.md)