Translate .htaccess Content to IIS web.config

By Steve Jacobson

February 23, 2009

Introduction

Many PHP applications are distributed with configuration files for the Apache Web server. These configuration files (usually called .htaccess files) contain a number of settings that can be used for integrating the application with the capabilities of the Web server.

IIS 7 and above uses a file called Web.config to hold settings for integration with applications. The Web.config file contains information that control module loading, security configuration, session state configuration, and application language and compilation settings. Web.config files can also contain application-specific items such as database connection strings.

This article describes the most common uses of the .htaccess file by PHP applications, and shows how to use the Web.config file for these same functions in IIS.

Sample Application Configuration Files

The following examples are two configuration files for a sample application: an .htaccess file and a Web.config file.

Sample Application .htaccess File

#
# Apache/PHP/Application settings:
#

# Protect files and directories from prying eyes.
<FilesMatch "\.(engine|inc|info|install|module|profile|po|sh|.*sql|theme|tpl(\.php)?|xtmpl)$|^(code-style\.pl|Entries.*|Repository|Root|Tag|Template)$">
Order allow,deny
</FilesMatch>

# Don't show directory listings for URLs which map to a directory.
Options -Indexes

# Follow symbolic links in this directory.
Options +FollowSymLinks

# Make Application handle any 404 errors.
ErrorDocument 404 /index.php

# Force simple error message for requests for non-existent favicon.ico.
<Files favicon.ico>
ErrorDocument 404 "The requested file favicon.ico was not found.
</Files>

# Set the default handler.
DirectoryIndex index.php

# Override PHP settings. More in sites/default/settings.php
# but the following cannot be changed at runtime.

# PHP 4, Apache 1.
<IfModule mod_php4.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
php_value mbstring.http_input pass
php_value mbstring.http_output pass
php_value mbstring.encoding_translation 0
</IfModule>

# PHP 4, Apache 2.
<IfModule sapi_apache2.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
php_value mbstring.http_input pass
php_value mbstring.http_output pass
php_value mbstring.encoding_translation 0
</IfModule>

# PHP 5, Apache 1 and 2.
<IfModule mod_php5.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
php_value mbstring.http_input pass
php_value mbstring.http_output pass
php_value mbstring.encoding_translation 0
</IfModule>

# Requires mod_expires to be enabled.
<IfModule mod_expires.c>
# Enable expirations.
ExpiresActive On

# Cache all files for 2 weeks after access (A).
ExpiresDefault A1209600

# Do not cache dynamically generated pages.
ExpiresByType text/html A1
</IfModule>

# Various rewrite rules.
<IfModule mod_rewrite.c>
RewriteEngine on

# If your site can be accessed both with and without the 'www.' prefix, you
# can use one of the following settings to redirect users to your preferred
# URL, either WITH or WITHOUT the 'www.' prefix. Choose ONLY one option:
#
# To redirect all users to access the site WITH the 'www.' prefix,
# (http://example.com/... will be redirected to http://www.example.com/...)
# adapt and uncomment the following:
# RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
# RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]
#
# To redirect all users to access the site WITHOUT the 'www.' prefix,
# (http://www.example.com/... will be redirected to http://example.com/...)
# uncomment and adapt the following:
# RewriteCond %{HTTP_HOST} ^www\.example\.com$ [NC]
# RewriteRule ^(.*)$ http://example.com/$1 [L,R=301]

# Modify the RewriteBase if you are using Application in a subdirectory or in a
# VirtualDocumentRoot and the rewrite rules are not working properly.
# For example if your site is at http://example.com/application uncomment and
# modify the following line:
# RewriteBase /application
#
# If your site is running in a VirtualDocumentRoot at http://example.com/,
# uncomment the following line:
# RewriteBase /

# Rewrite URLs of the form 'x' to the form 'index.php?q=x'.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]
</IfModule>

# $Id: .htaccess,v 1.90.2.1 2008/07/08 09:33:14 goba Exp $

Sample Application Web.config File

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

<configSections>
<sectionGroup name="system.webServer">
<sectionGroup name="rewrite">
<section name="rewriteMaps" overrideModeDefault="Allow" />
<section name="rules" overrideModeDefault="Allow" />
</sectionGroup>
</sectionGroup>
</configSections>

<system.webServer>
<security>
<!-- This section should be uncommented after
installation to secure the installation. -->
<!--
<requestFiltering>
<denyUrlSequences>
<add sequence="engine" />
<add sequence="inc" />
<add sequence="info" />
<add sequence="module" />
<add sequence="profile" />
<add sequence="po" />
<add sequence="sh" />
<add sequence="theme" />
<add sequence="tpl(\.php" />
<add sequence="Root" />
<add sequence="Tag" />
<add sequence="Template" />
<add sequence="Repository" />
<add sequence="code-style" />
</denyUrlSequences>
<fileExtensions>
<add fileExtension=".sql" allowed="false" />
<add fileExtension=".pl" allowed="false" />
</fileExtensions>
</requestFiltering>
-->
</security>
<directoryBrowse enabled="true" />
<caching>
<profiles>
<add extension=".php" policy="DisableCache" kernelCachePolicy="DisableCache" />
<add extension=".html" policy="CacheForTimePeriod" kernelCachePolicy="CacheForTimePeriod" duration="14:00:00:00" />
</profiles>
</caching>
<rewrite>
<rules>
<rule name="block favicon" stopProcessing="true">
<match url="favicon\.ico" />
<action type="CustomResponse" statusCode="404" subStatusCode="1"
statusReason="The requested file favicon.ico was not found"
statusDescription="The requested file favicon.ico was not found" />
</rule>
<rule name="Imported Rule 1" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions>
<add input="{HTTP_HOST}" pattern="^example\.com$" />
</conditions>

<action type="Redirect" redirectType="Permanent" url="http://www.example.com/{R:1}" />
</rule>
<rule name="Imported Rule 2" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
<add input="{URL}" pattern="^/favicon.ico$" ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="index.php?q={R:1}" appendQueryString="true" />
</rule>
</rules>
</rewrite>
<defaultDocument>
<files>
<remove value="index.php" />
<add value="index.php" />
</files>
</defaultDocument>

<!-- HTTP Errors section should only be enabled if the "Error Pages"
feature has been delegated as "Read/Write" at the Web Server level.
<httpErrors>
<remove statusCode="404" subStatusCode="-1" />
<error statusCode="404" prefixLanguageFilePath="" path="/index.php" responseMode="ExecuteURL" />
</httpErrors>
-->

</system.webServer>
</configuration>

Request Filtering

This application uses the FilesMatch directive in the .htacess file to limit browser access to files that are components of the application.

<FilesMatch "\.(engine|inc|info|install|module|profile|po|sh|.*sql|theme|tpl(\.php)?|xtmpl)$|^(code-style\.pl|Entries.*|Repository|Root|Tag|Template)$">
Order allow,deny
</FilesMatch>

IIS uses the Request Filtering module to limit browser access to files that are components of the application. For the sample application in a Web.config file, the section could look like:

<security>
<requestFiltering>
<denyUrlSequences>
<add sequence="engine" />
<add sequence="inc" />
<add sequence="info" />
<add sequence="install" />
<add sequence="module" />
<add sequence="profile" />
<add sequence="po" />
<add sequence="sh" />
<add sequence="theme" />
<add sequence="tpl(\.php" />
<add sequence="Root" />
<add sequence="Tag" />
<add sequence="Template" />
<add sequence="Repository" />
<add sequence="code-style" />
</denyUrlSequences>
<fileExtensions>
<add fileExtension=".sql" allowed="false" />
<add fileExtension=".pl" allowed="false" />
</fileExtensions>
</requestFiltering>
</security>

Note that you can leave this section commented out for installation, because the installation scripts are blocked by this filter.

An alternative to using the request filtering is to use the URL Rewriter module to return a 403 error for any of the matching file types. The advantage of the URL Rewriter module is that it uses a regular expression for the match.

<rule name="Protect files and directories from prying eyes" stopProcessing="true">
<match url="\.(engine|inc|info|install|module|profile|test|po|sh|.*sql|theme|tpl(\.php)?|xtmpl|svn-base)$|^(code-style\.pl|Entries.*|Repository|Root|Tag|Template|all-wcprops|entries|format)$" />
<action type="CustomResponse" statusCode="403" subStatusCode="0"
statusReason="Forbidden"
statusDescription="Access is forbidden." />
</rule>

Default Document

In the .htaccess file for the sample application, the DirectoryIndex directive tells the Web server which file to load if no filename is included with the URL.

# Set the default handler.
DirectoryIndex index.php

For IIS, the default document should be set up as high in the Web site hierarchy as the Module Handler. For example, with PHP, the Module Handler is usually set at the Web server level. The default document should be set at that level also, rather than locally within a Web site’s context. The following code within your Web.config file can ensure this:

<defaultDocument>
<files>
<remove value="index.php" />
<add value="index.php" />
</files>
</defaultDocument>

URL Rewriting

IIS includes the URL Rewrite module. You can use this extension to provide rules for IIS to rewrite incoming URL requests. The most common use of URL Rewriting is to provide shorter, easy-to-remember URLs.

Many PHP applications currently ship with rewrite rules as part of their .htaccess file. These rules tell Apache’s mod_rewrite how and when to rewrite incoming requests. The IIS URL Rewrite module can read these rules and translate them into URL Rewrite rules.

For more information about importing Apache mod_rewrite rules, see: Importing Apache mod_rewrite Rules.

For the sample application, the relevant mod_rewrite rules in the .htaccess file are:

RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]

The IIS URL Rewriter module can read these rules and translate them. The translated URL Rewriter rules are:

<rewrite>
<rules>
<rule name="Imported Rule 1" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions>
<add input="{HTTP_HOST}" pattern="^example\.com$" />
</conditions>
<action type="Redirect" redirectType="Permanent" url="http://www.example.com/{R:1}" />
</rule>
<rule name="Imported Rule 2" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
<add input="{URL}" pattern="^/favicon.ico$" ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="index.php?q={R:1}" appendQueryString="true" />
</rule>
</rules>
</rewrite>

Error Page Redirects / Handling

Some applications handle standard errors within the scope of the application. The ErrorDocument directive in the .htaccess file of the sample application tells the Web server to load the home page for any 404 or “File Not Found” errors.

# Make Application handle any 404 errors.
ErrorDocument 404 /index.php

IIS uses the httpErrors directive for this functionality. However, because the capability to set this at the application level is turned off by default for IIS, this section should be commented out.

<!-- HTTP Errors section should only be enabled if the "Error Pages"
feature has been delegated as "Read/Write" at the Web Server level.
<httpErrors>
<remove statusCode="404" subStatusCode="-1" />
<error statusCode="404" prefixLanguageFilePath="" path="/index.php" responseMode="ExecuteURL" />
</httpErrors>
-->

Directory Browsing

Another application security (or integrity) measure often implemented is disabling directory browsing from the clients. Many Web server configurations will let users see a listing of files in a directory that does not contain one of the default document files. In the .htaccess file of the sample application, this is disabled using the Options directive:

# Don't show directory listings for URLs which map to a directory.
Options -Indexes

IIS limits this access in the Web.config file using the directoryBrowse directive:

<directoryBrowse enabled="false" />

Cache Aging

Caching directives are used to ensure that static content is cached for a period of time, and dynamic content is not cached at all. In the .htaccess file of the sample application, the ExpiresBy directives provided by mod_expires module are used.

# Requires mod_expires to be enabled.
<IfModule mod_expires.c>
# Enable expirations.
ExpiresActive On

# Cache all files for 2 weeks after access (A).
ExpiresDefault A1209600

# Do not cache dynamically generated pages.
ExpiresByType text/html A1
</IfModule>

In the Web.config file, IIS uses the Output Caching module and the caching directive to control caching. For the sample application, you can enable caching for .html files for a maximum of 14 days. For .php files, ensure that no caching is performed at all with the code:

<caching>
<profiles>
<add extension=".php" policy="DisableCache" kernelCachePolicy="DisableCache" />
<add extension=".html" policy="CacheForTimePeriod" kernelCachePolicy="CacheForTimePeriod" duration="14:00:00:00" />
</profiles>
</caching>

Links for Further Information

IIS URL Rewriting and Microsoft® ASP.NET routing.

IIS forum.