secure-link

Paid digital content and user-uploaded content require access control. To implement authorization, it's common to generate a token, which is appended to the resource's location as a query string parameter. This module provides functions to generate secure access tokens, which can be used with Nginx, Cloudflare, Fastly or your own application.

Installation

npm install secure-link

Usage

Nginx

To generate a token, pass the resource's location and a secret key to the generateNginxAccessToken function. It optionally accepts a lifetime parameter, which will determine the date after which the token should be considered expired. It must be set in seconds since the epoch. For more information, check out the ngx_http_secure_link_module documentation.

const { generateNginxAccessToken } = require('secure-link');
 
const timeInSeconds = Math.round(Date.now() / 1000);
const expirationTime = timeInSeconds + 86400;
 
const options = {
  secret: process.env.SECRET_KEY,
  path: '/secure/statement.pdf',
  lifetime: expirationTime
};
 
const token = generateNginxAccessToken(options);

From there, you can append the token as a query string parameter.

const url = `https://cdn.example.com/secure/statement.pdf?token=${token}&expires=${expirationTime}`;

To validate the token when a request is received, you can hash the request URL and secret in a location block. The secure_link_md5 directive matches the format used by generateNginxAccessToken internally when creating tokens. Replace secret with the secret used to create the token to ensure the hashes are the same.

location /secure {
    secure_link $arg_token,$arg_expires;
    secure_link_md5 "$uri$secure_link_expires secret";
 
    # Token mismatch
    if ($secure_link = "") {
      return 403;
    }
 
    # Token expired
    if ($secure_link = "0") {
      return 410;
    }
 
    alias /path/to/directory;
}

Cloudflare

Coming soon...

Fastly

Coming soon...