Data Deletion Request Callback

To be compliant with General Data Protection Regulation (GDPR), applications that access user data must do one of the following:

• Implement a Data Deletion Request Callback.
• Provide a URL with explicit instructions for users on how to delete their data by way of a third-party website or tool. The third-party website may be the relevant section in the application's Privacy Policy.

If your app is a consumer or gaming app, either the callback or the URL is required for app submission and for turning on App Live. For more information about app types, see App Types in the App Development documentation.

The data deletion callback is called when users remove your app by way of the Facebook's Apps and Website settings page, and then in the Removed section, click your app and request that their data be deleted.

This generates a POST with a signed request that is sent to your app. The signed request contains an app-scoped ID identifying the user making the request. For an example of how to parse the request and the structure of the parsed request, see the following section.

In response to the user request, you should acknowledge receiving a user data deletion request through the technical means we provide, and provide a link and a confirmation number. The link and confirmation number must give the user access to a human-readable explanation of the status of their request, including a legitimate justification for any refusal to delete (where legitimate will vary based on jurisdiction and our case-by-case interpretation of our policy as it relates to their stated reasons).

Implementing the Callback

To parse and respond to the request, you should implement a "data deletion request" callback. Your callback must use the secure HTTPS protocol and must be listed in the Data Deletion Request URL field of your app's Facebook Login > Settings page in the app dashboard.

The Data Deletion Request callback that you implement must do the following:

• Initiate the deletion of any data your app has from Facebook about the user.
• Return a JSON response that contains a URL where the user can check the status of their deletion request and an alphanumeric confirmation code. The JSON response has the following form:
  { url: '<url>', confirmation_code: '<code>' }

Failure to comply with these requirements may result in your callback being removed or your app being disabled.

You can implement this callback in any language, but the following code is an example of the callback in PHP.

<?php
header('Content-Type: application/json');

$signed_request = $_POST['signed_request'];
$data = parse_signed_request($signed_request);
$user_id = $data['user_id'];

// Start data deletion

$status_url = 'https://www.<your_website>.com/deletion?id=abc123'; // URL to track the deletion
$confirmation_code = 'abc123'; // unique code for the deletion request

$data = array(
  'url' => $status_url,
  'confirmation_code' => $confirmation_code
);
echo json_encode($data);

function parse_signed_request($signed_request) {
  list($encoded_sig, $payload) = explode('.', $signed_request, 2);

  $secret = "appsecret"; // Use your app secret here

  // decode the data
  $sig = base64_url_decode($encoded_sig);
  $data = json_decode(base64_url_decode($payload), true);

  // confirm the signature
  $expected_sig = hash_hmac('sha256', $payload, $secret, $raw = true);
  if ($sig !== $expected_sig) {
    error_log('Bad Signed JSON signature!');
    return null;
  }

  return $data;
}

function base64_url_decode($input) {
  return base64_decode(strtr($input, '-_', '+/'));
}
?>

This produces a JSON object that looks like this, in which user_id is the relevant field for your callback.

{
   "algorithm": "HMAC-SHA256",
   "expires": 1291840400,
   "issued_at": 1291836800,
   "user_id": "218471"
}

For more information on signed requests, see Using a Signed Request in the Login for Games on Facebook topic.

Testing Your Callback

To test your callback:

1. Log in to your app with Facebook Login.
2. Go to app settings: https://www.facebook.com/settings?tab=applications
3. Remove your app.
4. In the Removed section, click on your app.
5. Request data deletion from the app card.