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<?php
define('FACEBOOK_APP_ID', '218513098160159');
define('FACEBOOK_SECRET', 'f6bc120db10274de370beb8cb5aceaea');
function parse_signed_request($signed_request, $secret) {
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
// decode the data
$sig = base64_url_decode($encoded_sig);
$data = json_decode(base64_url_decode($payload), true);
if (strtoupper($data['algorithm']) !== 'HMAC-SHA256') {
error_log('Unknown algorithm. Expected HMAC-SHA256');
return null;
}
// check sig
$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($input, '-_', '+/'));
}
if ($_REQUEST) {
echo '<p>signed_request contents:</p>';
$response = parse_signed_request($_REQUEST['signed_request'],
FACEBOOK_SECRET);
echo '<pre>';
print_r($response);
echo '</pre>';
} else {
echo '$_REQUEST is empty';
}
?>