Basic HTTP Authentication for CloudFront with Lambda@Edge in NodeJS

Question

I am working on protecting a static website with a username and password. I created a basic HTTP Authentication for CloudFront with Lambda@Edge in NodeJS.

I am completely new to NodeJS. Initially, I had the user and the password hardcoded, and this worked properly.

'use strict';
exports.handler = (event, context, callback) => {

    // Get request and request headers
    const request = event.Records[0].cf.request;
    const headers = request.headers;

    // Configure authentication
    const authUser = 'user';
    const authPass = 'pass';

    // Construct the Basic Auth string
    const authString = 'Basic ' + new Buffer(authUser + ':' + authPass).toString('base64');

    // Require Basic authentication
    if (typeof headers.authorization == 'undefined' || headers.authorization[0].value != authString) {
        const body = 'Unauthorized';
        const response = {
            status: '401',
            statusDescription: 'Unauthorized',
            body: body,
            headers: {
                'www-authenticate': [{key: 'WWW-Authenticate', value:'Basic'}]
            },
        };
        callback(null, response);
    }

    // Continue request processing if authentication passed
    callback(null, request);
};

I stored my secrets in SSM and I want to retrieve them through the function. I tested this piece of code separately in Lambda and it returns the credentials as espected.

'use strict';
exports.handler = async (event, context, callback) => {
    const ssm = new (require('aws-sdk/clients/ssm'))();
    let userData = await ssm.getParameters({Names: ['website-user']}).promise();
    let userPass = await ssm.getParameters({Names: ['website-pass']}).promise();
    let user = userData.Parameters[0].Value;
    let pass = userPass.Parameters[0].Value;
    return {user, pass};
};

But when I stitch the two, I get 503 ERROR The request could not be satisfied. Does anyone know what I might be doing wrong? Thank you for your help!

The complete code:

'use strict';

exports.handler = async (event, context, callback) => {
    const ssm = new (require('aws-sdk/clients/ssm'))();
    let userData = await ssm.getParameters({Names: ['website-user']}).promise();
    let userPass = await ssm.getParameters({Names: ['website-pass']}).promise();
    let user = userData.Parameters[0].Value;
    let pass = userPass.Parameters[0].Value;

    // Get request and request headers
    const request = event.Records[0].cf.request;
    const headers = request.headers;

    // Construct the Basic Auth string
    let authString = 'Basic ' + new Buffer(user + ':' + pass).toString('base64');

    // Require Basic authentication
    if (typeof headers.authorization == 'undefined' || headers.authorization[0].value != authString) {
        const body = 'Unauthorized';
        const response = {
            status: '401',
            statusDescription: 'Unauthorized',
            body: body,
            headers: {
                'www-authenticate': [{key: 'WWW-Authenticate', value:'Basic'}]
            },
        };
        callback(null, response);
    }

    // Continue request processing if authentication passed
    callback(null, request);
};

Answer 1

After reading about promises I was able to resolve the error. Here's the solution that worked for me:

'use strict';

var AWS = require('aws-sdk');
AWS.config.update({ region: 'us-east-1' });
var ssm = new AWS.SSM();

function getParameter(param) {
  return new Promise(function (success, reject) {
    ssm.getParameter(param, function (err, data) {
      if (err) {
        reject(err);
      } else {
        success(data);
      }
    });
  });
};

exports.handler =  (event, context, callback) => {
    let request = event.Records[0].cf.request;
    let headers = request.headers;
    let user = {Name: 'user-path', WithDecryption: false};
    let pass = {Name: 'password-path', WithDecryption: false};
    let authUser;
    let authPass;
    var promises = [];
    promises.push(getParameter(user), getParameter(pass));
    
    Promise.all(promises)
    .then(function (result) {
      authUser = result[0].Parameter.Value;
      authPass = result[1].Parameter.Value;
      console.log(authUser);
      console.log(authPass);
      let authString = 'Basic ' + new Buffer(authUser + ':' + authPass).toString('base64');
      if (typeof headers.authorization == 'undefined' || headers.authorization[0].value != authString) {
        const body = 'Unauthorized';
        const response = {
          status: '401',
          statusDescription: 'Unauthorized',
          body: body,
          headers: {
          'www-authenticate': [{key: 'WWW-Authenticate', value:'Basic'}]
        },
    };
    callback(null, response);
}

  // Continue request processing if authentication passed
  callback(null, request);
})
    .catch(function (err) {
      console.log(err);
    });
};