namespace Symfony\Component\Security\Http\Firewall;
// ...
class X509AuthenticationListener extends AbstractPreAuthenticatedListener
{
  // ...
    /**
     * {@inheritdoc}
     */
    protected function getPreAuthenticatedData(Request $request)
    {
        $user = null;
        if ($request->server->has($this->userKey)) {
            $user = $request->server->get($this->userKey);
        } elseif ($request->server->has($this->credentialKey) && preg_match('#/emailAddress=(.+\@.+\..+)(/|$)#', $request->server->get($this->credentialKey), $matches)) {
            $user = $matches[1];
        }

        if (null === $user) {
            throw new BadCredentialsException(sprintf('SSL credentials not found: %s, %s', $this->userKey, $this->credentialKey));
        }

        return [$user, $request->server->get($this->credentialKey, '')];
    }
}```