🔒 Secure Your Notifications

Without Secure Mode, an attacker can access another user’s in-app and web push notifications, and can read/update their notification preferences.

Secure Mode makes our front-end SDK safe against such threats.

someLibrary.initialize({
  userId: 'another-user-id'
});

How does the Secure Mode work?

With Secure Mode:

1. Your back-end hashes the userId, using your “Client Secret” as the hash key, and passes this hashedUserId to your front-end
2. Your front-end passes the hashedUserId to our front-end SDK when initializing it. With every request, our front-end SDK sends both the userId and hashedUserId to our servers.
3. Our servers generate their own hashedUserId (using the Client Secret) for the userId of the request. If the result matches the given hashedUserId, it means that the userId has not been tampered in your front-end. Since only NotificationAPI servers and your back-end know the Client Secret, no other party can generate a valid userIdHash for the userId.

An example with attacker:

1. Attacker updates the userId parameter in your front-end
2. Our front-end SDK sends the invalid userId and the hashedUserId to our servers
3. Our server hashes the invalid userId and notices the hash result differs from hashedUserId, thus rejects the requests.

Because the attacker does not have access to your Client Secret, they have no way of providing a valid hashedUserId for the invalid userId.

Step by Step Guide

1. Back-end

Hash the userId using your client secret. Pass the hashed userId to your front-end. For example, in response to user login or from a dedicated API.

const hashedUserId = require('crypto')
  .createHmac('sha256', 'YOUR_CLIENT_SECRET')
  .update('ACTUAL_USER_ID')
  .digest('base64');

import hmac
import hashlib
import base64
hashedUserId = base64.b64encode(hmac.new( 'YOUR_CLIENT_SECRET'.encode('utf-8'),
            'ACTUAL_USER_ID'.encode('utf-8'),
             hashlib.sha256).digest())

$hashedUserId = base64_encode(hash_hmac('sha256', $userId, $clientSecret, true));

import (
  "crypto/hmac"
  "crypto/sha256"
  "encoding/base64"
)

func hashUserId(userId string, clientSecret string) string {
  h := hmac.New(sha256.New, []byte(clientSecret))
  h.Write([]byte(userId))
  return base64.StdEncoding.EncodeToString(h.Sum(nil))
}

using System;
using System.Security.Cryptography;
using System.Text;

public static string HashUserId(string userId, string clientSecret)
{
    using (var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(clientSecret)))
    {
        var hash = hmac.ComputeHash(Encoding.UTF8.GetBytes(userId));
        return Convert.ToBase64String(hash);
    }
}

require 'openssl'
require 'base64'

def hash_user_id(user_id, client_secret)
  Base64.encode64(OpenSSL::HMAC.digest('sha256', client_secret, user_id))
end

2. Front-end

Pass the hashed userId to the NotificationAPI front-end SDK during initialization:

new NotificationAPI({
  clientId: '...',
  userId: 'ACTUAL_USER_ID',
  userIdHash: 'HASHED_USER_ID'
});

3. Enable Secure Mode

Go to Dashboard > Settings > Security to enabled secure mode. By enabling this feature, all front-end SDK requests without a valid hashedUserId will be rejected.