Symfony2 lets hackers pretend to be trusted IP addresses

Damien Tournoud, from the Drupal security team, contacted us two days ago about a security issue in the Request::getClientIp() method when the trust proxy mode is enabled (Request::trustProxyData()).

An application is vulnerable if it uses the client IP address as returned by the Request::getClientIp() method for sensitive decisions like IP based access control.

To fix this security issue, the following changes have been made to all versions of Symfony2:

A new Request::setTrustedProxies() method has been introduced and should be used intead of Request::trustProxyData() to enable the trust proxy mode. It takes an array of trusted proxy IP addresses as its argument:
```
// before (probably in your front controller script)
Request::trustProxyData();
```
```
// after
Request::setTrustedProxies(array('1.1.1.1'));
// 1.1.1.1 being the IP address of a trusted reverse proxy
```
The Request::trustProxyData() method has been deprecated (when used, it automatically trusts the latest proxy in the chain -- which is the current remote address):
```
Request::trustProxyData();
```
```
// is equivalent to
Request::setTrustedProxies(array($request->server->get('REMOTE_ADDR')));
```
We encourage all Symfony2 users to upgrade as soon as possible. It you don't want to upgrade to the latest version yet, you can also apply the following patches:

[Patch](https://github.com/symfony/symfony/compare/fc89d6b...9ce892c.patch) for Symfony 2.0.19
[Patch](https://github.com/symfony/symfony/compare/922c201...e5536f0.patch) for Symfony 2.1.4