Facebook PHP SDK 5 :: API 2.4 :: Cross-site request forgery validation failed. Required param "state" missing

Question

I did a very simple PHP script, just to try to login via Facebook and get an accessToken. But when I try the following code, I get an Exception from the SDK : « Cross-site request forgery validation failed. Required param "state" missing. ».

Here is my code :

require_once __DIR__ . '/facebook-sdk-v5/autoload.php';
session_start();

$fb = new Facebook\Facebook([
    'app_id' => '{my-own-app-id}',
    'app_secret' => '{my-own-app-secret}'
]);

// Check to see if we already have an accessToken ?
if (isset($_SESSION['facebook_access_token'] )) {
    $accessToken = $_SESSION['facebook_access_token'];
    echo "Horray we have our accessToken:$accessToken<br />\n";

} else {
    // We don't have the accessToken
    // But are we in the process of getting it ? 
    if (isset($_REQUEST['code'])) {
        $helper = $fb->getRedirectLoginHelper();
        try {
            $accessToken = $helper->getAccessToken();
            } catch(Facebook\Exceptions\FacebookResponseException $e) {
              // When Graph returns an error
              echo 'Graph returned an error: ' . $e->getMessage();
              exit;
        } catch(Facebook\Exceptions\FacebookSDKException $e) {
              // When validation fails or other local issues
              echo 'Facebook SDK returned an error: ' . $e->getMessage();
            exit;
        }

        if (isset($accessToken)) {
              // Logged in!
              $_SESSION['facebook_access_token'] = (string) $accessToken;

              // Now you can redirect to another page and use the
              // access token from $_SESSION['facebook_access_token']

              echo "Finally logged in! Token:$accessToken";
        }           
    } else {
        // Well looks like we are a fresh dude, login to Facebook!
        $helper = $fb->getRedirectLoginHelper();
        $permissions = ['email', 'user_likes']; // optional
        $loginUrl = $helper->getLoginUrl('http://mywebsite.com/myapp/index.php', $permissions);

        echo '<a href="' . $loginUrl . '">Log in with Facebook!</a>';
    }

}

exit;

Answer 1

I had to add this lines in some servers:

$helper = $fb->getRedirectLoginHelper();
if (isset($_GET['state'])) {
    $helper->getPersistentDataHandler()->set('state', $_GET['state']);
}

I get this error randomly, depending of the server config.

Answer 2

Laravel 5.2

I have this error too "Cross-site request forgery validation failed. Required param “state” missing".

and after reading this for hours. I tried to change the vendor script.

in vendor\facebook\php-sdk-v4\src\Facebook\Helpers\FacebookRedirectLoginHelper.php on line 123, I change this script:

private function makeUrl($redirectUrl, array $scope, array $params = [], $separator = '&')
{
    $state = $this->pseudoRandomStringGenerator->getPseudoRandomString(static::CSRF_LENGTH);
    $this->persistentDataHandler->set('state', $state);

    return $this->oAuth2Client->getAuthorizationUrl($redirectUrl, $state, $scope, $params, $separator);
}

into (I add Session::put('state', $state);)

private function makeUrl($redirectUrl, array $scope, array $params = [], $separator = '&')
{
    $state = $this->pseudoRandomStringGenerator->getPseudoRandomString(static::CSRF_LENGTH);
    $this->persistentDataHandler->set('state', $state);
    Session::put('state', $state);
    return $this->oAuth2Client->getAuthorizationUrl($redirectUrl, $state, $scope, $params, $separator);
}

and on line 234, I change this script:

protected function validateCsrf()
{
    $state = $this->getState();
    $savedState = $this->persistentDataHandler->get('state');

    if (!$state || !$savedState) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. Required param "state" missing.');
    }

    $savedLen = strlen($savedState);
    $givenLen = strlen($state);

    if ($savedLen !== $givenLen) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. The "state" param from the URL and session do not match.');
    }

    $result = 0;
    for ($i = 0; $i < $savedLen; $i++) {
        $result |= ord($state[$i]) ^ ord($savedState[$i]);
    }

    if ($result !== 0) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. The "state" param from the URL and session do not match.');
    }
}

into (I added $this->persistentDataHandler->set('state', Session::get('state'));)

protected function validateCsrf()
{
    $state = $this->getState();
    $this->persistentDataHandler->set('state', Session::get('state'));
    $savedState = $this->persistentDataHandler->get('state');

    if (!$state || !$savedState) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. Required param "state" missing.');
    }

    $savedLen = strlen($savedState);
    $givenLen = strlen($state);

    if ($savedLen !== $givenLen) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. The "state" param from the URL and session do not match.');
    }

    $result = 0;
    for ($i = 0; $i < $savedLen; $i++) {
        $result |= ord($state[$i]) ^ ord($savedState[$i]);
    }

    if ($result !== 0) {
        throw new FacebookSDKException('Cross-site request forgery validation failed. The "state" param from the URL and session do not match.');
    }
}

that is all what I did. and the error gone.