Secret Gifts with Twilio Verify for Gift of Code

Time to read: 4 minutes

December 21, 2020

Written by

Rachel Black

Twilion

Reviewed by

Kelley Robinson

Twilion

Valeriane Venance

Twilion

Secret Gifts with Twilio Verify for Gift of Code

It’s December and in typical fashion I have left Christmas shopping too late. But as a developer, I can always use my coding powers to build a gift. Using Twilio Verify, I will code a small application that gifts a secret message to a holder of a specific phone number. This secret content could take the form of a message, picture etc. Watch out friends and family, I am going to be using it to gift my favourite holiday GIFs!

Technical requirements

A free Twilio account. If you use this link to register, you will receive $10 credit when you upgrade to a paid account
Node.js and npm installed

User flow

Our application will be coded with a specific person in mind. This user will be identified by their telephone number. This user will be able to visit our application, start the verification process and receive a SMS code. On submitting the correct code our application will show them the secret content.

A user visits our application and starts the verification process. A SMS code is sent to the mobile number. They input this code and unlock the secret content.

Getting started

We will use Express generator to create the boilerplate for our application. Install with:

npm install -g express-generator
express --view=pug giftOfCode 
cd giftOfCode
npm i

Opening the directory in your code editor, you should see the following template:

To this we will add a .gitignore and .env file:

touch .gitignore .env

Open the .gitignore and add the following:

.env
node_modules
views/elements/secret.pug  // the secret content we display only if the user verifies.

We do not want to commit either our node modules, or the .env file, which will contain our authentication keys to source.

Pug.js Frontend

We generated our application with Pugs.js as the view engine. Pug.js a HTML templating engine which offers us a straightforward way to build out our frontend. Unlike HTML you can pass in conditionals, loops, includes and mixins.

We can update or add the following Pug.js files to our /views directory:

Update views/index.pug

extends layout

block content

  h1 Happy Holidays 🎄
  p Get your gift below

  if !showCodeInput
    form#secret-form(action='/create-verify' method='get')
      button(type='submit' form='secret-form' value='Submit') Start Verify
  if showCodeInput
    form#verify-check(action='/verify-check' method='post')
      label(for='verifyCode') Prove your identity with the code
      input#secret(type='text' name='verifyCode')
      button(type='submit' form='verify-check' value='Submit') Submit

    form#secret-form(action='/create-verify' method='get')
      button(type='submit' form='secret-form' value='Submit') Resend

Here in views/error.pug we will render a button to start the verify process, and a form to input the Verify code that will be sent over.

error.pug
extends layout

block content
  h1 Something went wrong
  a(href="/") try again

An error layout which returns us to the home page.

Finally our secret content in views/secret.pug.

extends layout

block content
  h1 Secret info
  img(src='https://media.giphy.com/media/S6O2GuDzHJCoVD7NFm/giphy.gif')

Once the application is working, you can replace it with your own secret content.

Verifying our recipients number

The secret content in this application should only be accessible to the recipient. If we know their telephone number, we can use Twilio Verify’s REST API to send a code to their phone, which they can input to our application. Therefore to gain access to the secret content, you will need to have access to the phone number we specify.

We will work through the following steps:

Create a verification service
Start a verification
Input the verification code (verification check)
Handle a successful and failed verification

Creating a verification service

Before we can start verifying the numbers of our users. We need to create a verification service. The documentation explains how to do this via the API, but for this tutorial, let’s create one in Twilio Console. Select the ‘Create new service’ button, and name your service, this will be used in the verification message template, but you can always change it later.

Once you have created the service, you will be taken to an overview page. Here you can change the length of code sent out (we recommend at least 6). Copy the SERVICE SID and store in your .env file as:

SERVICE_ID=VAxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Whilst we are in the Twilio Console, we can also grab the other required Twilio credentials. Navigate to the Console dashboard (home icon) and copy your account SID and auth token. Add them to your .env file:

SID=ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
AUTH=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

We want to keep the recipient’s number private as well, so add the recipient's number in E.164 format to your .env file. This can be your own number while you're testing:

RECIPIENT_NUM=+44xxxx

Now we have created the service, and have our Twilio credentials, we can start coding the verification process.

Starting a verification

Install the following modules:

npm i twilio env2

Along with Twilio, we are installing the env2 to handle our environment variables.

Open up routes/index.js file and require both at the top of the file.

require("env2")(__dirname + "./../.env");
const client = require("twilio")(process.env.SID, process.env.AUTH);

Once we have required env2 with the correct path to our .env file, we can access any of our defined environment variables via process.env. We make use of environment variables to avoid committing API keys and other sensitive information like phone numbers.

Next, let’s replace the index route with:

router.get("/", (req, res) => {
 res.render("index", { showCodeInput: false });
});

When we first navigate to our page, we will render index.pug, with the variable showCodeInput of false. According to our template, this conditional will hide the verify code input, and show the button to trigger the verify process.

Referring back to our index.pug file, we can see that when we hit the button to start the verification process, we do a GET request to /create-verify. Returning back to routes/index.js, we add the following code to process this get request:

router.get("/create-verify", (req, res) => {
 client.verify
   .services(process.env.SERVICE_ID)
   .verifications.create({ to: process.env.RECIPIENT_NUM, channel: "sms" })
   .then((verification) => {
     return res.render("index", { showCodeInput: true });
   })
   .catch((err) => {
     console.log(err);
     res.render("error")
   });
});

This triggers a verification, and the recipient will receive an sms with a code. In addition this request returns the index.pug, but this time with the showCodeInput conditional. In the UI this will render a simple form input, where the user can submit their code.

Processing the verification code

Now we need to write the /verify-check POST endpoint. Checking in our index.pug file, we can see that this request is the action on the input form, meaning it will be triggered when the user submits their code.

We can add the following to routes/index.js:

router.post("/verify-check", (req, res) => {
 client.verify
   .services(process.env.SERVICE_ID)
   .verificationChecks.create({
     to: process.env.RECIPIENT_NUM,
     code: req.body.verifyCode,
   })
   .then((verification_check) => {
     if (verification_check.status === "approved") {
       return res.render("secret");
     }
     return res.render("error");
   });
});

Here we use the Verify API again, this time to check the code is correct. We do this using the verification check method. This method takes the number we are verifying and the code we have sent from the frontend. It returns the verification_check, which allows us to ensure the status is “approved” before rendering our secret content. If the verification check method returns something other than approved, we will render our error UI.

Run the application from the terminal with npm start and navigate to http://localhost:3000/

Test this out with your own number, and to see the secret content, you will have to verify that your number matches the one in the .env file. Now it’s working, swap out the super dull secret template with your own message or content If deploying your site, make sure to use HTTPS rather than unencrypted HTTP, to prevent hackers doing a man in the middle attack.

Happy coding and a merry new year!