Pete Freitag Pete Freitag

20 ways to Secure your Apache Configuration

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Here are 20 things you can do to make your apache configuration more secure.

Disclaimer: The thing about security is that there are no guarantees or absolutes. These suggestions should make your server a bit tighter, but don't think your server is necessarily secure after following these suggestions.

Additionally some of these suggestions may decrease performance, or cause problems due to your environment. It is up to you to determine if any of the changes I suggest are not compatible with your requirements. In other words proceed at your own risk.

First, make sure you've installed latest security patches

There is no sense in putting locks on the windows, if your door is wide open. As such, if you're not patched up there isn't really much point in continuing any longer on this list. Go ahead and bookmark this page so you can come back later, and patch your server.

You'll need a way to know when new Apache Server vulnerabilities are published. I like to use stack.watch to notify me when new Apache httpd server vulnerabilities are published. The service is free, and will send you an email whenever new vulnerabilities exist.

Hide the Apache Version number, and other sensitive information.

By default many Apache installations tell the world what version of Apache you're running, what operating system/version you're running, and even what Apache Modules are installed on the server. Attackers can use this information to their advantage when performing an attack. It also sends the message that you have left most defaults alone.

There are two directives that you need to add, or edit in your httpd.conf file:

ServerSignature Off
ServerTokens Prod

The ServerSignature appears on the bottom of pages generated by apache such as 404 pages, directory listings, etc.

The ServerTokens directive is used to determine what Apache will put in the Server HTTP response header. By setting it to Prod it sets the HTTP response header as follows:

Server: Apache

If you're super paranoid you could change this to something other than "Apache" by editing the source code, or by using mod_security (see below).

Make sure apache is running under its own user account and group

Several apache installations have it run as the user nobody. So suppose both Apache, and your mail server were running as nobody an attack through Apache may allow the mail server to also be compromised, and vise versa.

User apache
Group apache

Ensure that files outside the web root are not served

We don't want apache to be able to access any files out side of its web root. So assuming all your web sites are placed under one directory (we will call this /web), you would set it up as follows:

<Directory />
  Order Deny,Allow
  Deny from all
  Options None
  AllowOverride None
</Directory>
<Directory /web>
  Order Allow,Deny
  Allow from all
</Directory>
Note that because we set Options None and AllowOverride None this will turn off all options and overrides for the server. You now have to add them explicitly for each directory that requires an Option or Override.

Turn off directory browsing

You can do this with an Options directive inside a Directory tag. Set Options to either None or -Indexes

Options -Indexes

Turn off server side includes

This is also done with the Options directive inside a Directory tag. Set Options to either None or -Includes

Options -Includes

Turn off CGI execution

If you're not using CGI turn it off with the Options directive inside a Directory tag. Set Options to either None or -ExecCGI

Options -ExecCGI

Don't allow apache to follow symbolic links

This can again can be done using the Options directive inside a Directory tag. Set Options to either None or -FollowSymLinks

Options -FollowSymLinks

Turning off multiple Options

If you want to turn off all Options simply use:

Options None

If you only want to turn off some separate each option with a space in your Options directive:

Options -ExecCGI -FollowSymLinks -Indexes

Turn off support for .htaccess files

This is done in a Directory tag but with the AllowOverride directive. Set it to None.

AllowOverride None

If you require Overrides ensure that they cannot be downloaded, and/or change the name to something other than .htaccess. For example we could change it to .httpdoverride, and block all files that start with .ht from being downloaded as follows:

AccessFileName .httpdoverride
<Files ~ "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy All
</Files>

Run mod_security

mod_security is a super handy Apache module written by Ivan Ristic, the author of Apache Security from O'Reilly press.

You can do the following with mod_security:

  • Simple filtering
  • Regular Expression based filtering
  • URL Encoding Validation
  • Unicode Encoding Validation
  • Auditing
  • Null byte attack prevention
  • Upload memory limits
  • Server identity masking
  • Built in Chroot support
  • And more

Disable any unnecessary modules

Apache typically comes with several modules installed. Go through the apache module documentation and learn what each module you have enabled actually does. Many times you will find that you don't need to have the said module enabled.

Look for lines in your httpd.conf that contain LoadModule. To disable the module you can typically just add a # at the beginning of the line. To search for modules run:

grep LoadModule httpd.conf

Here are some modules that are typically enabled but often not needed: mod_imap, mod_include, mod_info, mod_userdir, mod_status, mod_cgi, mod_autoindex.

Make sure only root has read access to apache's config and binaries

This can be done assuming your apache installation is located at /usr/local/apache as follows:

chown -R root:root /usr/local/apache
chmod -R o-rwx /usr/local/apache

Lower the Timeout value

By default the Timeout directive is set to 300 seconds. You can decrease help mitigate the potential effects of a denial of service attack.

Timeout 45

Limiting large requests

Apache has several directives that allow you to limit the size of a request, this can also be useful for mitigating the effects of a denial of service attack.

A good place to start is the LimitRequestBody directive. This directive is set to unlimited by default. If you are allowing file uploads of no larger than 1MB, you could set this setting to something like:

LimitRequestBody 1048576

If you're not allowing file uploads you can set it even smaller.

Some other directives to look at are LimitRequestFields, LimitRequestFieldSize and LimitRequestLine. These directives are set to a reasonable defaults for most servers, but you may want to tweak them to best fit your needs. See the documentation for more info.

Limiting the size of an XML Body

If you're running mod_dav (typically used with subversion) then you may want to limit the max size of an XML request body. The LimitXMLRequestBody directive is only available on Apache 2, and its default value is 1 million bytes (approx 1mb). Many tutorials will have you set this value to 0 which means files of any size may be uploaded, which may be necessary if you're using WebDAV to upload large files, but if you're simply using it for source control, you can probably get away with setting an upper bound, such as 10mb:

LimitXMLRequestBody 10485760

Limiting Concurrency

Apache has several configuration settings that can be used to adjust handling of concurrent requests. The MaxClients is the maximum number of child processes that will be created to serve requests. This may be set too high if your server doesn't have enough memory to handle a large number of concurrent requests.

Other directives such as MaxSpareServers, MaxRequestsPerChild, and on Apache2 ThreadsPerChild, ServerLimit, and MaxSpareThreads are important to adjust to match your operating system, and hardware.

Restricting Access by IP

If you have a resource that should only by accessed by a certain network, or IP address you can enforce this in your apache configuration. For instance if you want to restrict access to your intranet to allow only the 176.16 network:


Order Deny,Allow
Deny from all
Allow from 176.16.0.0/16

Or by IP:

Order Deny,Allow
Deny from all
Allow from 127.0.0.1

Adjusting KeepAlive settings

According to the Apache documentation using HTTP Keep Alive's can improve client performance by as much as 50%, so be careful before changing these settings, you will be trading performance for a slight denial of service mitigation.

KeepAlive's are turned on by default and you should leave them on, but you may consider changing the MaxKeepAliveRequests which defaults to 100, and the KeepAliveTimeout which defaults to 15. Analyze your log files to determine the appropriate values.

Run Apache in a Chroot environment

chroot allows you to run a program in its own isolated jail. This prevents a break in on one service from being able to effect anything else on the server.

It can be fairly tricky to set this up using chroot due to library dependencies. I mentioned above that the mod_security module has built in chroot support. It makes the process as simple as adding a mod_security directive to your configuration:

SecChrootDir /chroot/apache

There are however some caveats however, so check out the mod_security docs for more info.

Acknowledgments

I have found the book Apache Security to be a highly valuable resource for securing an apache web server. Some of the suggestions listed above were inspired by this book.

Suggestions

Please post any suggestions, caveats, or corrections in the comments and I will update the post if necessary.


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20 ways to Secure your Apache Configuration was first published on December 06, 2005.

If you like reading about apache, security, mod_security, configuration, howto, tips, reference, ivan ristic, or httpd then you might also like:

Comments

Very helpful. I was just searching for an article on securing Apache with ColdFusion the other day. Windows/IIS users may want to take a look at this article which is Windows 2003 specific:

Configuring ColdFusion MX 7 Server Security
http://www.macromedia.com/devnet/coldfusion/articles/cf7_security.html
by Steven Erat on 12/06/2005 at 12:20:01 PM UTC
Yes the apache configuration does not limit what PHP (or any cgi program) can do. I'm not sure if there is any way of limiting that, but I'm not a php guru.

Thanks for pointing out that typo as well, I'll fix it.
by Pete Freitag on 12/12/2005 at 12:24:27 PM UTC
For mod_security, the guys at gotroot.com make a very complete set of rules available that you can download and pop in to protect against all kinds of attacks. They update the rules every few days. An excellent way to help protect your application from known exploits, XSS and other attempts.

Brian
by Brian on 01/20/2006 at 3:19:28 PM UTC
Cheers Mate...
by Qrucial on 02/04/2006 at 12:11:51 PM UTC
Thats a great resource. Thanks a lot !
Some wicked tips in there
by web design uk on 06/17/2006 at 5:28:51 AM UTC
i want to know how to setup .cfm
on apache???
by Renan on 08/21/2006 at 4:28:37 PM UTC
Author, pin pointed the performance, security issues with suitable mitigation. Cool.
by Ramesh Kumar on 12/15/2006 at 5:13:09 AM UTC
If you don't want to use mod_security, and simply looks for hiding/masking Server: header, there's a tiny third part module that exists to do it on :
http://jok.is-a-geek.net/blog/index.php?page=read&id=2006/01/090956
by Jok on 01/05/2007 at 6:07:22 PM UTC
Awesome article man, very helpful. Here is a really good post dealing with securing SSL http://www.askapache.com/2006/htaccess/apache-ssl-in-htaccess-examples.html
by Apache Dude on 01/08/2007 at 5:46:44 AM UTC
Thank you.
by Debi Winters on 04/04/2007 at 4:01:48 PM UTC
Thanks. Its really helpfull. Keep it up.
by Humayun on 06/05/2007 at 1:35:27 AM UTC
Hi, I know I'm a bit late to the party, but I just wanted to comment on Renan's query regarding .cfm files not being sent to the correct ErrorDocument location as set in Apache's config.

To have Apache catch .cfm files, instead of Coldfusion displaying an error, you need to update the IfModule mod_jrun22.c portion of the httpd.conf file for Apache. Change the 'JRunConfig Ignoresuffixmap false' to 'JRunConfig Ignoresuffixmap true'
by Brontojoris on 12/02/2007 at 6:29:10 PM UTC
Restricting Access by IP
If you have a resource that should only by accessed by a certain network.

I am sure that "by" should be a "be"
thanks for this topic!
by Mario Barrera A. on 05/23/2008 at 2:50:54 PM UTC
Very well article. I would like to add the way you can exclude needless Apache modules. After commenting out needless candidate, run httpd.conf test, not httpd restart because httpd in case of error will not start. You should also comment depend modules. I describe whole procedure on www.redips.net so I hope you will find useful information there.
by Darko Bunic on 08/01/2008 at 2:16:39 AM UTC
its good, but Drupal confidure with apache , clean URl must change AllowOverride All.
by Rashmin on 08/11/2008 at 11:09:57 PM UTC
hi anyone help me to configure the apache in centos 5.1 or 5.2 i am windows base but i want to switch in linux!please help me tank you
by rey on 11/26/2008 at 2:53:09 AM UTC
@James - You could always add users to the Apache group to allow editing by other users.
by Pete Freitag on 01/29/2010 at 8:54:15 AM UTC
@James - I suggest you look into the mod_suexec module http://httpd.apache.org/docs/2.2/mod/mod_suexec.html
by Rudy Puig on 02/11/2010 at 12:57:55 PM UTC
Great post. 5 years old, but super-great still :) thnx bro
by Goran on 05/18/2010 at 9:56:11 AM UTC
Thanks a lot for this guide,

I think it will be more secure to state:<Directory />
Order Allow,Deny
</Directory>

instead of
<Directory />
Order Deny,Allow
Deny from all
</Directory>

This way if there is more matching rules later, some allowing access and some denying it the request will be denied (your code will allow access in this case)

see here http://httpd.apache.org/docs/2.0/mod/mod_access.html#order
by ahwebd on 10/21/2010 at 3:06:29 PM UTC
Hi,
If people knows the URL to static file on the server as .DOC/.pdf how can I prevent them from accessing this.
One way is to to the basic suthentication on that folder but is there any other way?

Thanks for the help.

Thanks
vinod
by vinod palan on 08/23/2011 at 6:59:35 PM UTC
Thanks for the tips! I just went through and configured similar to what you advise. It is working peachy and I feel a bit safer. I also use SSL for my login forms, etc. so that no one is passing plain text passwords around the web!
by Derik on 01/28/2012 at 7:46:09 PM UTC
Hi,
Please let me know how can i modify my own header.
by default apache is showing but i want to shown in header abcd
So please help me...
by Arvind Lavania on 04/04/2012 at 3:03:36 AM UTC
I've a web site that has been up and running for some time now, and for numerous reasons I want to replace it with a Wordpress site.. . So, how do I commence making the Wordpress site - within a seperate folder from the "public_html" folder? Then when you will be ready to move it into the public_html folder, does one have to correct whatever file-paths and link errors?.
by Unrettygreats on 10/27/2012 at 11:32:32 AM UTC
@Mr. Helpful - There is no way to remove the server header with standard Apache modules that I'm aware of, you will need a third party module such as mod_security to do that for you.
by Pete Freitag on 04/11/2013 at 10:52:14 AM UTC
Have a look at Apache security on HTTP Security Headers - https://www.yeahhub.com/http-security-headers-apache-servers/
by Alex on 09/22/2018 at 7:50:25 PM UTC