Authenticate Users in a Single Page Application with Auth0

    Joel LordJoel Lord

    In this lesson, we take the previous API and front-end and we convert them to use Auth0 to replace our custom authentication server built in the previous lessons.



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    Instructor: 00:00 Since this lesson is aimed at using Auth0 for authentication, the first thing we'll need to do is to go to the website and create a free account.

    00:09 The sign-up process is fairly straightforward. You can use an email and password or you can use any of the social connections here. This free account will give you access to most of the Auth0 API for up to 7,000 users, which is more than enough for the purpose of this lesson.

    00:24 Once you're signed up, you can log into your account, and you will land on this dashboard. This shows you your active users and the number of logins in the last few days.

    00:34 From here, we'll want to go to the API section to create a new entry. This is what will be used to protect our API.

    00:42 You can pick anything for the name. Let's just use Egghead Demo. For the identifier, you can use anything, but it is recommended that you use the URL of your application. In this case, we don't have a URL, so we'll just use egghead-demo as well.

    00:58 Finally, you will want to use HS256 for the signing algorithm, because this is what we used in the previous lesson. Once you have this, you click on create, and the modal is closed, and you get redirected to the quick start page.

    01:11 If you look at this page, you get code examples on how to implement this with your API. As you can see, it uses the same middleware as we currently use, the main difference being the settings for the middleware itself.

    01:24 We will have a secret key, but we also check who is the token meant for, the audience, and who created this token, the issuer. Those are additional checks that will make your API even more secure. Let's now go back at our code editor and open api.js.

    01:41 You can simply change the settings of the middleware by pasting the values you copied from the Auth0 website. Note that those values will need to be the ones from your Auth0 account. If you try to copy the values that I just pasted in, this won't work for you.

    01:56 We can now head to our terminal window and start our API server by running node api. Your server is now running on port 8888. If you try this now, nothing will work. Your front end also needs to get a token from Auth0. Let's get back to our code and do those changes.

    02:13 Because we won't be using our authorization server anymore, we can go ahead and remove the auth.js file from this folder altogether. It's now time to edit our index.html page to use Auth0's authentication server instead of ours.

    02:28 The first thing that we'll want to do is to remove the login modal. We will be using Auth0's login screen, so let's go to line 21 and remove those data tags that were used to open the modal.

    02:40 We can also rename this button to be login-btn instead. Since we won't be using the modal anymore, we can go down here and delete all of the markup for our login modal.

    02:55 We will use Auth0's library, which we will get from their CDN. We can add a script tag. The source will be the version number, which is 9.5.1, the latest at this moment, /auth0.min.js.

    03:21 Our index.html file is not ready, but to finish the UI changes, we will need to go to the uiupdate.js file and do a few minor changes in there. Instead of showing and hiding the login modal button, we will do that on the login button. Let's change line 5 to use login-btn, and same thing on line 11. We're almost done.

    03:44 Let's open our index.js file to change our code to use Auth0's authentication server instead of the one we built. In here, we will need to use Auth0's webAuth object. First, we need to get the settings for this object. Let's go back to Auth0's website and go into the application section.

    04:03 In here, we choose to create a new application. We can name it whatever, but we will use egghead-demo for consistency. This is application is of type single-page application, so we can select this and click on create.

    04:17 Similar to when we created the API, we get a screen that suggests us various quick starts. In here, you can find for most major JavaScript frameworks, but we are going to use plain vanilla JavaScript here.

    04:30 If you scroll down, you will find a section, which has all of your settings for your application. Once again, make sure that you copy those from your Auth0 account, and not those from this video. Let's copy that and go back to our code.

    04:44 Now we can create a webAuth object using a new auth0.WebAuth, and we can paste the settings we got from the quick start.

    04:52 If you use Auth0's application with a default setting, it is OpenID Connect-enabled, which is outside the scope of this lesson. We will need to tweak the settings of this application in order to be able to use it.

    05:04 Going back to Auth0 and into the settings of our application, the first thing that we will need to change is the callback URL. This is the page where users are redirected after they're logged in on Auth0. You can go to your application, get the URL from there, and simply paste it in the settings.

    05:22 We will also need to go all the way down to the advanced settings. This is not an OIDC conformant application, so we can uncheck this. We can change our JWT signature to also use HS256. We're good. Just save this, and we can head back to our code editor.

    05:42 We need to tweak our settings just a little bit here. Our domain is the issuer of the token. It's what is referred to as tenant in Auth0's website. The client ID is found in your settings. This should be good.

    05:54 In response type, we won't need the ID token, so we can remove this. The audience is the API that we want to connect to. Let's change this to egghead-demo. Finally, the scope is irrelevant in this case, so we can simply remove this.

    06:10 The redirect URI is where your user will be redirected afterwards. This URL has to be in your application settings in the allowed callback URL section, which we already took care of. Let's now change the logic behind our login button.

    06:25 Right now, we had to get all of that info from the modal and post that to our authentication server, but we won't need any of this now. Let's just remove all of this and use webAuth with the authorize method instead. Save this, and you should be good to go.

    06:40 If we go to our app and refresh it, and you try the public button, it should return you the data from our public endpoint. If you tried a private one, you should be getting an error message, which is normal, since we haven't logged in, yet.

    06:53 Let's do that right away and click on the login button. You can see that we are redirected to the Auth0 login screen. You now have some social sign-ons, you have a sign-up page, you have a forgot password page. All of that for free just by using Auth0. I'll go ahead and log in with Google.

    07:13 Now you get the consent UI screen asking you if you want to share the information with the application. Let's go ahead and accept that, and we are sent back to our website.

    07:23 As you can see, as part of my URL, now has a hash followed by an access token. Now if I try my public button, it still works, but if I use a private button, I'm still getting the "No authorization token was found," error message. That's because we need to parse our hash and extract the access token from there, and store it so that it can be used by our fetch call.

    07:43 Thankfully, there is a method in the Auth0 library to help us with that. Let's create a parseHash function here. This function will call webAuth's parseHash method, which takes a callback as an argument.

    07:56 This callback has an error, and authResult arguments. Let's look at the happy path and check if we have an auth result and an access token.

    08:04 We can remove the hash part of the URL. We can also store our access token in our access token variable.

    08:12 Finally, let's use our UI update helper to indicate that we are logged in. This function will need to run at some point. Let's add an event listener to our window object for DOMContentLoaded, and run this function then.

    08:28 Let's go back to our application now and refresh this. We can try public and private, and we are getting the expected result. Let's go ahead and log in.

    08:38 I'll log in with Google again. You'll notice that I haven't been asked for my consent again, as I had given it previously and it remembers this.

    08:48 Now I'm redirected back to the application, our URL is clean, it doesn't have hash in it anymore, and we have our access token right here. If you copied this token, you can go to the website and paste it there.

    09:01 This will decode the token for you and show you all of the details of this JWT. You can see that it's an HS256 encoded token. You also have a bunch of stuff like the issuer -- so who created this token -- you have your user ID, and the audience, which is who this token is meant for. You also have your issued at and an expiry time-stamps, which can be very useful.

    09:26 Now that you have this token, you can click on the private button and you see the response from your secured endpoint in your API. That's how you make a real secure application with Auth0.