Basic authentication with CloudFront KeyValueStore

basic-auth-with-cloudFront-KeyValueStore.js

import cf from 'cloudfront';

const kvsId = '<KEY_VALUE_STORE_ID>';

// This fails if the key value store is not associated with the function
const kvsHandle = cf.kvs(kvsId)

async function handler(event) {
    const request = event.request;
    const headers = request.headers;
    const method = request.method;

    let username = '';
    let password = '';
    try {
        username = await kvsHandle.get('username');
        password = await kvsHandle.get('password');
    } catch (err) {
        console.log(`Kvs key lookup failed: ${err}`);
        throw err;
    }

    const authorization = `Basic ${(`${username}:${password}`).toString('base64')}`;  
    const origin = '*';

    // Preflight requests skip basic authentication
    if (method === "OPTIONS") {
        return {
            statusCode: 204,
            statusDescription: "NoContent",
            headers: {
                "access-control-allow-origin": { value: origin }
            }
        };
    }

    // Handling of authentication fail
    if (headers.authorization === undefined ||
        headers.authorization.value !== authorization) {
        return {
            statusCode: 401,
            statusDescription: 'Unauthorized',
            headers: {
                'www-authenticate': {value: 'Basic'}
            }
        };
    }

    return event.request;
}