mod_rewrite

Whilst converting tokiwinter.com away from mod_php to mod_fastcgi/PHP-FPM, I experienced the following error:

[Thu Jul 11 14:29:31 2013] [error] [client 192.168.122.1] Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

1	[Thu Jul 11 14:29:31 2013] [error] [client 192.168.122.1] Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

Enabling LogLevel debug for the VirtualHost showed the following extra detail:

[Thu Jul 11 14:29:31 2013] [debug] core.c(3072): [client 192.168.122.1] r->uri = /index.php
[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /cgi-bin/php5.fcgi/index.php
[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /index.php
[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /cgi-bin/php5.fcgi/index.php
[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /index.php
...

[Thu Jul 11 14:29:31 2013] [debug] core.c(3072): [client 192.168.122.1] r->uri = /index.php

[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /cgi-bin/php5.fcgi/index.php

[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /index.php

[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /cgi-bin/php5.fcgi/index.php

[Thu Jul 11 14:29:31 2013] [debug] core.c(3078): [client 192.168.122.1] redirected from r->uri = /index.php

...

We can see that the rewrites required for WordPress in .htaccess are interfering with the correct operation of mod_fastcgi. The net result - HTTP 500 Internal Server Error for all our clients.

The fix is easy enough - add the following additional rewrite to .htaccess for the WordPress installation:

RewriteCond %{REQUEST_URI} ^/cgi-bin/php5.fcgi(.*)
RewriteRule . - [L]

1 2	RewriteCond %{REQUEST_URI} ^/cgi-bin/php5.fcgi(.*) RewriteRule . - [L]

i.e. if the request URI is a mod_fastcgi request, do not apply any rewrites. My complete .htaccess file in my WordPress VirtualHost is now:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_URI} ^/cgi-bin/php5.fcgi(.*)
RewriteRule . - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

# BEGIN WordPress

RewriteEngine On

RewriteBase /

RewriteRule ^index\.php$ - [L]

RewriteCond %{REQUEST_URI} ^/cgi-bin/php5.fcgi(.*)

RewriteRule . - [L]

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

RewriteRule . /index.php [L]

</IfModule>

# END WordPress

This works for me with the following VirtualHost configuration:

NameVirtualHost *:80
<VirtualHost *:80>
	ServerAdmin toki@tokiwinter.com
	ServerName tokiwinter.com
	ServerAlias www.tokiwinter.com	
	DocumentRoot /var/www/virtualhosts/tokiwinter.com/htdocs
	ScriptAlias "/cgi-bin/" "/var/www/virtualhosts/tokiwinter.com/htdocs/cgi-bin/"
	FastCGIExternalServer /var/www/virtualhosts/tokiwinter.com/htdocs/cgi-bin/php5.fcgi -host 127.0.0.1:9000
	ErrorLog logs/tokiwinter.com-error_log
	CustomLog logs/tokiwinter.com-access_log common
	<Directory />
		AllowOverride all
		Order allow,deny
		Allow from all
		AddType application/x-httpd-fastphp5 .php
		Action application/x-httpd-fastphp5 /cgi-bin/php5.fcgi
	</Directory>
	DirectoryIndex index.php
</VirtualHost>

NameVirtualHost *:80

ServerAdmin toki@tokiwinter.com

ServerName tokiwinter.com

ServerAlias www.tokiwinter.com

DocumentRoot /var/www/virtualhosts/tokiwinter.com/htdocs

ScriptAlias "/cgi-bin/" "/var/www/virtualhosts/tokiwinter.com/htdocs/cgi-bin/"

FastCGIExternalServer /var/www/virtualhosts/tokiwinter.com/htdocs/cgi-bin/php5.fcgi -host 127.0.0.1:9000

ErrorLog logs/tokiwinter.com-error_log

CustomLog logs/tokiwinter.com-access_log common

AllowOverride all

Order allow,deny

Allow from all

AddType application/x-httpd-fastphp5 .php

Action application/x-httpd-fastphp5 /cgi-bin/php5.fcgi

</Directory>

DirectoryIndex index.php

</VirtualHost>

Your mileage may well vary.

Within Apache HTTPD’s mod_rewrite, RewriteCond only applies one RewriteRule that comes immediately after the RewriteCond itself. It didn’t seem like such a great idea to have to duplicate a lengthy RewriteCond definition half a dozen times for multiple RewriteRules.

Turns out there is a fairly simple trick to achieve exactly what I was looking for: if the RewriteCond is negated and followed by RewriteRule . – [S=n] to skip the following n rules, the RewriteRules in essence are only applied when the singular RewriteCond is true. Like so:

RewriteCond %{REQUEST_URI} !^/(pattern1|pattern2|pattern3)/$ [NC]
RewriteRule . - [S=3]
RewriteRule ^/pattern1/$ /someURL.php [L]
RewriteRule ^/pattern2/$ /someURL2.php [L]
RewriteRule ^/pattern3/$ /iLikeDoughnuts.php [L]

RewriteCond %{REQUEST_URI} !^/(pattern1|pattern2|pattern3)/$ [NC]

RewriteRule . - [S=3]

RewriteRule ^/pattern1/$ /someURL.php [L]

RewriteRule ^/pattern2/$ /someURL2.php [L]

RewriteRule ^/pattern3/$ /iLikeDoughnuts.php [L]

Now the last three rules are skipped if the condition is not true or, in reverse, they are applied if the condition is true. Each pattern is then handled individually, and the [L] rewrite option will cause only the pertinent rule to be applied - processing will stop after the first matched condition.

Toki Winter

Advanced UNIX for the experienced system administrator

Tag Archives: mod_rewrite

WordPress: Avoiding Infinite Recursion with mod_rewrite and mod_fastcgi

Apache HTTPD mod_rewrite: one RewriteCond to many RewriteRules