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
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
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:
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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
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
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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.