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Httpd Mod_proxy



Apache HTTPD typically comes with the modproxy modules already included. This is the case on Red Hat Enterprise Linux and the HTTPD that comes with the JBoss Enterprise Web Server. You need root or administrator privileges to modify the HTTPD configuration. Apache Httpd modproxy - Error Page Cross-Site Scripting. Webapps exploit for Multiple platform.

Note

mod_proxy_html has now been relicensed andincorporated into the core Apache HTTPD distribution atapache.org from HTTPD 2.4.That version is now likely to be more up-to-date than this one.

Here a one-line bug-fix has been introduced since version 3.1.3.If you downloaded the bundled package from here, you should applythe patch before compiling.The bug won't affect most users and is not a security issue, so if youare already using mod_proxy_html successfully there's nothing to do.

mod_proxy_html is an output filter to rewrite HTML links in a proxysituation, to ensure that links work for users outside the proxy.It serves the same purpose as Apache's ProxyPassReversedirective does for HTTP headers, and is an essential component of areverse proxy.

For example, if a company has an application server atappserver.example.com that is only visible from withinthe company's internal network, and a public webserverwww.example.com, they may wish to provide a gateway tothe application server at http://www.example.com/appserver/.When the application server links to itself, those links need to berewritten to work through the gateway. mod_proxy_html serves torewrite <a href='http://appserver.example.com/foo/bar.html'>foobar</a>to <a href='http://www.example.com/appserver/foo/bar.html'>foobar</a>making it accessible from outside.

April 2006 Added a new FAQ todeal with some of the questions people commonly mail me with.

Origins and History

For more recent history, see updates at apache.org.

The current bugfix release is 3.1.4. The most recent single-line bugfixis dated 2013-02-04.

The current version is 3.1. This builds on the new features in3.0, but delegates internationalisation/charset support tomod_xml2enc. The previous version 3.0is here.

The origins and history of mod_proxy_htmlare documented in a separate page.

Related Modules

  • mod_proxy_html is derived originally from mod_accessibility.
  • A companion module mod_proxy_xml servesa similar purpose for XML document types, based on extensible namespace processing.
  • mod_publisher is the universal markupmanipulation filter. It includes the capabilities of mod_proxy_html amongsta broad range of powerful markup processing options.
  • mod_xml2enc provides extensiveinternationalisation support for mod_proxy_html. In the absence ofmod_xml2enc, mod_proxy_html will work well on ASCII or UTF-8 (Unicode),but may display other character sets incorrectly (or not at all).

Capabilities

The original capabilities of mod_proxy_html are:

  • Parses HTML and XHTML markup, rewriting links according to rules definedby the server admin.
  • Optionally converts HTML to XHTML or vice versa.
  • Optionally makes some minor corrections to broken HTML.

Important changes from 1.x to 2.x include:

Libapache2 Mod Proxy Html

Httpd mod_proxy example
  • Support for rewriting URLs in scripts, stylesheets and scripting events
  • Support for regular expression match-and-replace
  • Improved charset detection, including XML BOM, XML declaration, and HTML META where the information is not available in HTTP.
  • Support for converting meta http-equiv HTML elements to real HTTP headers.
  • The default FPI (doctype) generated has changed to none, on the grounds that it's better to omit it than declare a bogus doctype. You should now configure it explicitly if your backend generates sane HTML or XHTML.
  • A verbose logging option is provided to help with testing yourconfiguration and diagnosing exactly what it is doing.

Important changes from 2.x to 3.x include:

  • Improved Internationalisation support no longer relies on libxml2'suseful but limited builtin capabilities, but is delegated tomod_xml2enc.
  • Configurable support for proprietary HTML variants.
  • Enables fixups for bad HTML, including corrections and workaroundsfor common problems.
  • Flexible configuration using environment variables, interpolation,and conditional execution of rules.

With these new features, mod_proxy_html might find applications outside aproxy context, and an environment variable PROXY_HTML_FORCEcan be used to force it to process non-proxied pages.But reverse-proxying remains its primary purpose, whilemod_publisher offers a far wider rangeof capabilities for other applications.

How to use it

Httpd Mod_proxy

Important Note: Configuration has changed:

Httpd mod_proxy_html
  1. Unless you only need to handle unicode (or ASCII), you should loadmod_xml2enc alongside mod_proxy_html.
  2. Instead of using Apache's filter configuration directives, usethe new ProxyHTMLEnable directive, and mod_proxy_htmlwill configure both itself and mod_xml2enc for you.

We now have three documents: a tutorial on reverse proxying (includingbasic use of mod_proxy_html), a user guide, and a configuration guide.Please read the tutorial first, unless you already know it all!

Tutorial:Reverse Proxying

A tutorial on reverse proxying with Apache by the author of this moduleis available at ApacheTutor. This offers an in-depth overview ofthe problem solved by this module, in context.

Configuration Guide

Reference documentation for the configuration directives implementedby mod_proxy_html.

Apache Proxy Server

Technical Guide

This focuses on the module itself, separate from the context of theproblem it solves.

Frequently Asked Questions

Some questions come up repeatedly (sometimes in the form of bugreports, feature requests, or patches). Please see the FAQ beforemailing anything.

Support

Support is available from the developer for paying clients.

Support is also available on an ad-hoc basis from the apache community,including the users mailinglist, and the #httpd channel on irc.freenode.org.

Availability

Httpd Mod_proxy_ajp

mod_proxy_html.c source code is available from here under theGNU General Public License (GPL) Version 2.

  • Last bundled Version (3.1.2) as bzippedtar (signature) and aszipfile(signature).
  • Development Version.

NOTE: If you downloaded the bundle before October 30th,you should upgrade your copy of mod_xml2enc to 1.0.3, which fixes a bug.The current bundle includes the bugfix.

The current version from apache.org has been relicensed underthe Apache License. If you are redistributing anything derived frommod_proxy_html, you should use the source whose license bestmeets your needs. If neither license is appropriate, we can considerrelicensing on your own terms for payment.

Apache Mod Proxy

Errata

Go Mod Proxy

Users of the FreeBSD port of mod_proxy_html, please see this fix.