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Trusting Proxies

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Trusting Proxies

Tip

If you’re using the Symfony Framework, start by reading How to Configure Symfony to Work behind a Load Balancer or a Reverse Proxy.

If you find yourself behind some sort of proxy - like a load balancer - then certain header information may be sent to you using special X-Forwarded-* headers or the Forwarded header. For example, the Host HTTP header is usually used to return the requested host. But when you’re behind a proxy, the actual host may be stored in an X-Forwarded-Host header.

Since HTTP headers can be spoofed, Symfony does not trust these proxy headers by default. If you are behind a proxy, you should manually whitelist your proxy as follows:

use Symfony\Component\HttpFoundation\Request;

// put this code as early as possible in your application (e.g. in your
// front controller) to only trust proxy headers coming from these IP addresses
Request::setTrustedProxies(array('192.0.0.1', '10.0.0.0/8'));

New in version 2.3: CIDR notation support was introduced in Symfony 2.3, so you can whitelist whole subnets (e.g. 10.0.0.0/8, fc00::/7).

You should also make sure that your proxy filters unauthorized use of these headers, e.g. if a proxy natively uses the X-Forwarded-For header, it should not allow clients to send Forwarded headers to Symfony.

If your proxy does not filter headers appropriately, you need to configure Symfony not to trust the headers your proxy does not filter (see below).

Configuring Header Names

By default, the following proxy headers are trusted:

If your reverse proxy uses a different header name for any of these, you can configure that header name via setTrustedHeaderName():

Request::setTrustedHeaderName(Request::HEADER_FORWARDED, 'X-Forwarded');
Request::setTrustedHeaderName(Request::HEADER_CLIENT_IP, 'X-Proxy-For');
Request::setTrustedHeaderName(Request::HEADER_CLIENT_HOST, 'X-Proxy-Host');
Request::setTrustedHeaderName(Request::HEADER_CLIENT_PORT, 'X-Proxy-Port');
Request::setTrustedHeaderName(Request::HEADER_CLIENT_PROTO, 'X-Proxy-Proto');

Not Trusting certain Headers

By default, if you whitelist your proxy’s IP address, then all five headers listed above are trusted. If you need to trust some of these headers but not others, you can do that as well:

// disables trusting the ``Forwarded`` header
Request::setTrustedHeaderName(Request::HEADER_FORWARDED, null);

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.