How to Configure Symfony to Work behind a Load Balancer or a Reverse Proxy
How to Configure Symfony to Work behind a Load Balancer or a Reverse Proxy¶
When you deploy your application, you may be behind a load balancer (e.g. an AWS Elastic Load Balancer) or a reverse proxy (e.g. Varnish for caching).
For the most part, this doesn’t cause any problems with Symfony. But, when
a request passes through a proxy, certain request information is sent using
either the standard
Forwarded header or non-standard special
headers. For example, instead of reading the
REMOTE_ADDR header (which
will now be the IP address of your reverse proxy), the user’s true IP will be
stored in a standard
Forwarded: for="..." header or a non standard
If you don’t configure Symfony to look for these headers, you’ll get incorrect information about the client’s IP address, whether or not the client is connecting via HTTPS, the client’s port and the hostname being requested.
This is no problem, but you do need to tell Symfony what is happening and which reverse proxy IP addresses will be doing this type of thing:
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# app/config/config.yml # ... framework: trusted_proxies: [192.0.0.1, 10.0.0.0/8]
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<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:framework="http://symfony.com/schema/dic/symfony" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/symfony http://symfony.com/schema/dic/symfony/symfony-1.0.xsd"> <framework:config trusted-proxies="192.0.0.1, 10.0.0.0/8"> <!-- ... --> </framework> </container>
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// app/config/config.php $container->loadFromExtension('framework', array( 'trusted_proxies' => array('192.0.0.1', '10.0.0.0/8'), ));
In this example, you’re saying that your reverse proxy (or proxies) has
the IP address
192.0.0.1 or matches the range of IP addresses that use
the CIDR notation
10.0.0.0/8. For more details, see the
You are also saying that you trust that the proxy does not send conflicting
headers, e.g. sending both
Forwarded in the same
That’s it! Symfony will now look for the correct headers to get information like the client’s IP address, host, port and whether the request is using HTTPS.
But what if the IP of my Reverse Proxy Changes Constantly!¶
Some reverse proxies (like Amazon’s Elastic Load Balancers) don’t have a static IP address or even a range that you can target with the CIDR notation. In this case, you’ll need to - very carefully - trust all proxies.
Configure your web server(s) to not respond to traffic from any clients other than your load balancers. For AWS, this can be done with security groups.
Once you’ve guaranteed that traffic will only come from your trusted reverse proxies, configure Symfony to always trust incoming request. This is done inside of your front controller:
// web/app.php // ... Request::setTrustedProxies(array('127.0.0.1', $request->server->get('REMOTE_ADDR'))); $response = $kernel->handle($request); // ...
Ensure that the trusted_proxies setting in your
app/config/config.ymlis not set or it will overwrite the
That’s it! It’s critical that you prevent traffic from all non-trusted sources. If you allow outside traffic, they could “spoof” their true IP address and other information.
My Reverse Proxy Sends X-Forwarded-For but Does not Filter the Forwarded Header¶
Many popular proxy implementations do not yet support the
and do not filter it by default. Ideally, you would configure this in your
proxy. If this is not possible, you can tell Symfony to distrust the
header, while still trusting your proxy’s
This is done inside of your front controller:
// web/app.php // ... Request::setTrustedHeaderName(Request::HEADER_FORWARDED, null); $response = $kernel->handle($request); // ...
Configuring the proxy server trust is very important, as not doing so will allow malicious users to “spoof” their IP address.
My Reverse Proxy Uses Non-Standard (not X-Forwarded) Headers¶
Although RFC 7239 recently defined a standard
Forwarded header to disclose
all proxy information, most reverse proxies store information in non-standard
But if your reverse proxy uses other non-standard header names, you can configure these (see “Trusting Proxies”).
The code for doing this will need to live in your front controller (e.g.
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.