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Apache > HTTP Server > Documentation > Version 2.2 > Modules

Apache Module mod_proxy

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Description:HTTP/1.1 proxy/gateway server
Status:Extension
Module Identifier:proxy_module
Source File:mod_proxy.c

Summary

Warning

Do not enable proxying with ProxyRequests until you have secured your server. Open proxy servers are dangerous both to your network and to the Internet at large.

This module implements a proxy/gateway for Apache. It implements proxying capability for AJP13 (Apache JServe Protocol version 1.3), FTP, CONNECT (for SSL), HTTP/0.9, HTTP/1.0, and HTTP/1.1. The module can be configured to connect to other proxy modules for these and other protocols.

Apache's proxy features are divided into several modules in addition to mod_proxy: mod_proxy_http, mod_proxy_ftp, mod_proxy_ajp, mod_proxy_balancer, and mod_proxy_connect. Thus, if you want to use one or more of the particular proxy functions, load mod_proxy and the appropriate module(s) into the server (either statically at compile-time or dynamically via the LoadModule directive).

In addition, extended features are provided by other modules. Caching is provided by mod_cache and related modules. The ability to contact remote servers using the SSL/TLS protocol is provided by the SSLProxy* directives of mod_ssl. These additional modules will need to be loaded and configured to take advantage of these features.

Directives

Topics

See also

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Forward Proxies and Reverse Proxies/Gateways

Apache can be configured in both a forward and reverse proxy (also known as gateway) mode.

An ordinary forward proxy is an intermediate server that sits between the client and the origin server. In order to get content from the origin server, the client sends a request to the proxy naming the origin server as the target and the proxy then requests the content from the origin server and returns it to the client. The client must be specially configured to use the forward proxy to access other sites.

A typical usage of a forward proxy is to provide Internet access to internal clients that are otherwise restricted by a firewall. The forward proxy can also use caching (as provided by mod_cache) to reduce network usage.

The forward proxy is activated using the ProxyRequests directive. Because forward proxies allow clients to access arbitrary sites through your server and to hide their true origin, it is essential that you secure your server so that only authorized clients can access the proxy before activating a forward proxy.

A reverse proxy (or gateway), by contrast, appears to the client just like an ordinary web server. No special configuration on the client is necessary. The client makes ordinary requests for content in the name-space of the reverse proxy. The reverse proxy then decides where to send those requests, and returns the content as if it was itself the origin.

A typical usage of a reverse proxy is to provide Internet users access to a server that is behind a firewall. Reverse proxies can also be used to balance load among several back-end servers, or to provide caching for a slower back-end server. In addition, reverse proxies can be used simply to bring several servers into the same URL space.

A reverse proxy is activated using the ProxyPass directive or the [P] flag to the RewriteRule directive. It is not necessary to turn ProxyRequests on in order to configure a reverse proxy.

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Basic Examples

The examples below are only a very basic idea to help you get started. Please read the documentation on the individual directives.

In addition, if you wish to have caching enabled, consult the documentation from mod_cache.

Forward Proxy

ProxyRequests On
ProxyVia On

<Proxy *>
Order deny,allow
Deny from all
Allow from internal.example.com
</Proxy>

Reverse Proxy

ProxyRequests Off

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

ProxyPass /foo http://foo.example.com/bar
ProxyPassReverse /foo http://foo.example.com/bar

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Controlling access to your proxy

You can control who can access your proxy via the <Proxy> control block as in the following example:

<Proxy *>
Order Deny,Allow
Deny from all
Allow from 192.168.0
</Proxy>

For more information on access control directives, see mod_authz_host.

Strictly limiting access is essential if you are using a forward proxy (using the ProxyRequests directive). Otherwise, your server can be used by any client to access arbitrary hosts while hiding his or her true identity. This is dangerous both for your network and for the Internet at large. When using a reverse proxy (using the ProxyPass directive with ProxyRequests Off), access control is less critical because clients can only contact the hosts that you have specifically configured.

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Slow Startup

If you're using the ProxyBlock directive, hostnames' IP addresses are looked up and cached during startup for later match test. This may take a few seconds (or more) depending on the speed with which the hostname lookups occur.

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Intranet Proxy

An Apache proxy server situated in an intranet needs to forward external requests through the company's firewall (for this, configure the ProxyRemote directive to forward the respective scheme to the firewall proxy). However, when it has to access resources within the intranet, it can bypass the firewall when accessing hosts. The NoProxy directive is useful for specifying which hosts belong to the intranet and should be accessed directly.

Users within an intranet tend to omit the local domain name from their WWW requests, thus requesti