NAME
   Apache2::ModProxyPerlHtml - rewrite HTTP headers and HTML links for
   reverse proxy usage

DESCRIPTION
   Apache2::ModProxyPerlHtml is the most advanced Apache output filter to
   rewrite HTTP headers and HTML links for reverse proxy usage. It is
   written in Perl and exceeds all mod_proxy_html.c limitations without
   performance lost.

   Apache2::ModProxyPerlHtml is very simple and has far better
   parsing/replacement of URL than the original C code. It also supports
   meta tag, CSS, and javascript URL rewriting and can be used with
   compressed HTTP. You can now replace any code by other, like changing
   image names or anything else. mod_proxy_html can't do all of that. Since
   release 3.x ModProxyPerlHtml is also able to rewrite HTTP headers with
   Refresh url redirection and Referer.

   The replacement capability concern only the following HTTP content type:

           text/javascript
           text/html
           text/css
           text/xml
           application/.*javascript
           application/.*xml

   other kind of file, will be left untouched (or see ProxyHTMLContentType
   and ProxyHTMLExcludeContentType).

AVAILIBILITY
   You can get the latest version of Apache2::ModProxyPerlHtml from CPAN
   (http://search.cpan.org/).

PREREQUISITES
   You must have Apache2, mod_proxy, mod_perl and IO::Compress::Zlib perl
   modules installed on your system.

 Installation on RH/CentOs
   Install Apache2, apxs, the Epel repository (for mod_perl install) and
   the Perl Module IO::Compress:

           yum install httpd httpd-devel
           yum install epel-release
           yum install perl-IO-Compress

   Install ModPerl, minimal version to work with Apache 2.4 is 2.0.10:

           yum list | grep mod_perl
           yum --enablerepo=epel -y install mod_perl mod_perl-devel

   Enable mod_perl:

           a2enconf mod_perl
           systemctl reload apache2

   The Apache module mod_ssl is not available by default, install it:

           yum install mod_ssl

   If the firewall is enabled you might want to allow access to the Apache
   services

           firewall-cmd --permanent --add-service=http
           firewall-cmd --permanent --add-service=https
           firewall-cmd --reload

 Installation on Debian/Ubuntu
   To have Apache2 server and apxs command:

           apt install apache2 apache2-dev

   ModPerl can be installed using:

           apt install libapache2-mod-perl2 libapache2-mod-perl2-dev

   ModProxyPerlHtml need additional Perl module IO::Compress:

           apt install libio-compress-perl

   Enable mod_proxy:

           a2enmod proxy
           a2enmod proxy_http
           a2enmod proxy_ftp
           a2enmod proxy_connect

   Enable the configuration and mod_perl:

           a2enmod perl

INSTALLATION
           % perl Makefile.PL
           % make && make install

APACHE CONFIGURATION
   On Debian/Ubuntu set the following configuration into the VirtualHost
   section of files /etc/apache2/sites-available/default-ssl.conf and
   /etc/apache2/sites-available/000-default.conf. On CentOS/RedHat add it
   to /etc/httpd/conf.d/vhost.conf.

       ProxyRequests Off
       ProxyPreserveHost Off
       ProxyPass       /webcal/  http://webcal.domain.com/

       PerlInputFilterHandler Apache2::ModProxyPerlHtml
       PerlOutputFilterHandler Apache2::ModProxyPerlHtml
       SetHandler perl-script
       # Use line below and comment line above if you experience error:
       # "Attempt to serve directory". The reason is that with SetHandler
       # DirectoryIndex is not working
       # AddHandler perl-script *
       PerlSetVar ProxyHTMLVerbose "On"
       LogLevel Info


       <Location /webcal/>
           ProxyPassReverse /
           PerlAddVar ProxyHTMLURLMap "/ /webcal/"
           PerlAddVar ProxyHTMLURLMap "http://webcal.domain.com /webcal"
       </Location>

   Note that here FilterHandlers are set globally, you can also set them in
   any <Location> part to set it locally and avoid calling this Apache
   module globally.

   If you want to rewrite some code on the fly, like changing images
   filename you can use the perl variable ProxyHTMLRewrite under the
   location directive as follow:

       <Location /webcal/>
           ...
           PerlAddVar ProxyHTMLRewrite "/logo/image1.png /images/logo1.png"
           # Or more complicated to handle space in the code as space is the
           # pattern / substitution separator character internally in ModProxyPerlHtml
           PerlAddVar ProxyHTMLRewrite "ajaxurl[\s\t]*=[\s\t]*'/blog' ajaxurl = '/www2.mydom.org/blog'"
           ...
       </Location>

   this will replace each occurence of '/logo/image1.png' by
   '/images/logo1.png' in the entire stream (html, javascript or css). Note
   that this kind of substitution is done after all other proxy related
   replacements.

   In some conditions javascript code can be replaced by error, for
   example:

           imgUp.src = '/images/' + varPath + '/' + 'up.png';

   will be rewritten like this:

           imgUp.src = '/URL/images/' + varPath + '/URL/' + 'up.png';

   To avoid the second replacement, write your JS code like that:

           imgUp.src = '/images/' + varPath + unescape('%2F') + 'up.png';

   ModProxyPerlHTML replacement is activated on certain HTTP Content Type.
   If you experienced that replacement is not activated for your file type,
   you can use the ProxyHTMLContentType configuration directive to
   redefined the HTTP Content Type that should be parsed by
   ModProxyPerlHTML. The default value is the following Perl regular
   expresssion:

           PerlAddVar ProxyHTMLContentType    (text\/javascript|text\/html|text\/css|text\/xml|application\/.*javascript|application\/.*xml)

   If you know exactly what you are doing by editing this regexp fill free
   to add the missing Content-Type that must be parsed by ModProxyPerlHTML.
   Otherwise drop me a line with the content type, I will give you the
   rigth expression. If you don't know about the content type, with FireFox
   simply type Ctrl+i on the web page.

   Some MS Office files may conflict with the above ProxyHTMLContentType
   regex like .docx or .xlsx files. The result is that there could suffer
   of replacement inside and the file will be corrupted. to prevent this
   you have the ProxyHTMLExcludeContentType configuration directive to
   exclude certain content-type. Here is the default value:

           PerlAddVar ProxyHTMLExcludeContentType  (application\/vnd\.openxml)

   If you have problem with other content-type, use this directive. For
   example, as follow:

           PerlAddVar ProxyHTMLExcludeContentType  (application\/vnd\.openxml|application\/vnd\..*text)

   this regex will prevent any MS Office XML or text document to be parsed.

   Some javascript libraries like JQuery are wrongly rewritten by
   ModProxyPerlHtml. The problem is that those javascript code include some
   code and regex that are detected as links and rewritten. The only way to
   fix that is to exclude those files from the URL rewritter by using the
   "ProxyHTMLExcludeUri" configuration directive. For example:

           PerlAddVar ProxyHTMLExcludeUri  jquery.min.js$
           PerlAddVar ProxyHTMLExcludeUri  ^.*\/jquery-lib\/.*$

   Any downloaded URI that contains the given regex will be returned asis
   without rewritting. You can use this directive multiple time like above
   to match different cases.

LIVE EXAMPLE
   Here is the reverse proxy configuration I use to give access to Internet
   users to internal applications:

       ProxyRequests Off
       ProxyPreserveHost Off
       ProxyPass       /webmail/  http://webmail.domain.com/
       ProxyPass       /webcal/  http://webcal.domain.com/
       ProxyPass       /intranet/  http://intranet.domain.com/


       PerlInputFilterHandler Apache2::ModProxyPerlHtml
       PerlOutputFilterHandler Apache2::ModProxyPerlHtml
       SetHandler perl-script
       # Use line below iand comment line above if you experience error:
       # "Attempt to serve directory". The reason is that with SetHandler
       # DirectoryIndex is not working
       # AddHandler perl-script *
       PerlSetVar ProxyHTMLVerbose "On"
       LogLevel Info


       # URL rewriting
       RewriteEngine   On
       #RewriteLog      "/var/log/apache/rewrite.log"
       #RewriteLogLevel 9
       # Add ending '/' if not provided
       RewriteCond     %{REQUEST_URI}  ^/mail$
       RewriteRule     ^/(.*)$ /$1/    [R]
       RewriteCond     %{REQUEST_URI}  ^/planet$
       RewriteRule     ^/(.*)$ /$1/    [R]
       # Add full path to the CGI to bypass the index.html redirect that may fail
       RewriteCond     %{REQUEST_URI}  ^/calendar/$
       RewriteRule     ^/(.*)/$ /$1/cgi-bin/wcal.pl    [R]
       RewriteCond     %{REQUEST_URI}  ^/calendar$
       RewriteRule     ^/(.*)$ /$1/cgi-bin/wcal.pl     [R]


       <Location /webmail/>
           ProxyPassReverse /
           PerlAddVar ProxyHTMLURLMap "/ /webmail/"
           PerlAddVar ProxyHTMLURLMap "http://webmail.domain.com /webmail"
           # Use this to disable compressed HTTP
           #RequestHeader   unset   Accept-Encoding
       </Location>


       <Location /webcal/>
           ProxyPassReverse /
           PerlAddVar ProxyHTMLURLMap "/ /webcal/"
           PerlAddVar ProxyHTMLURLMap "http://webcal.domain.com /webcal"
       </Location>


       <Location /intranet/>
           ProxyPassReverse /
           PerlAddVar ProxyHTMLURLMap "/ /intranet/"
           PerlAddVar ProxyHTMLURLMap "http://intranet.domain.com /intranet"
           # Rewrite links that give access to the two previous location
           PerlAddVar ProxyHTMLURLMap "/intranet/webmail /webmail"
           PerlAddVar ProxyHTMLURLMap "/intranet/webcal /webcal"
       </Location>

   This gives access two a webmail and webcal application hosted internally
   to all authentified users through their own Internet acces. There's also
   one acces to an Intranet portal that have links to the webcal and
   webmail application. Those links must be rewritten twice to works.

ROT13 obfuscation
   Some links can be obfucated to be hidden from google or other robots. To
   enable encode/decode of those links you can use the ProxyHTMLRot13Links
   directive as follow:

           PerlAddVar ProxyHTMLRot13Links All

   All links in the page will be decoded before being rewritten and
   re-encoded.

   If obfuscation occurs on some attributs only you can set the value as a
   pair of element:attribut where the decoding/encoding must be applied.
   For example:

           PerlAddVar ProxyHTMLRot13Links a:data-href
           PerlAddVar ProxyHTMLRot13Links a:href

BUGS
   Apache2::ModProxyPerlHtml is still under development and is pretty
   stable. Please send me email to submit bug reports or feature requests.

COPYRIGHT
   Copyright (c) 2005-2020 - Gilles Darold

   All rights reserved. This program is free software; you may redistribute
   it and/or modify it under the same terms as Perl itself.

AUTHOR
   Apache2::ModProxyPerlHtml was created by :

           Gilles Darold
           <gilles at darold dot net>

   and is currently maintain by me.

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