Cis Apache 5.9

Ensure Old HTTP Protocol Versions Are Disallowed

Description

The Apache modules mod_rewrite and mod_security can be used to disallow old and invalid HTTP versions. The HTTP 1.1 RFC is dated June 1999 and has been supported by Apache since version 1.2, so it should no longer be necessary to allow ancient versions of HTTP prior to 1.1. Refer to the Apache documentation on mod_rewrite for more details: http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html

Rationale

Many malicious automated programs, vulnerability scanners, and fingerprinting tools send requests using old HTTP versions to see how the web server responds. These requests are usually part of the attacker's enumeration process.

Impact

None documented

Audit Procedure

Perform the following to determine if the recommended state is implemented:

1. Locate the Apache configuration files and included configuration files.
2. Verify there is a rewrite condition within the global server context that disallows requests that do not include the HTTP/1.1 header, as shown below.

RewriteEngine On
RewriteCond %{THE_REQUEST} !HTTP/1\.1$
RewriteRule .* - [F]

3. Verify the following directives are included in each section so that the main server settings will be inherited:

RewriteEngine On
RewriteOptions Inherit

Remediation

Perform the following to implement the recommended state:

1. Load the mod_rewrite module for Apache by doing either one of the following:

   • Add a LoadModule directive in the main Apache configuration file
   • Build Apache with mod_rewrite compiled in statically
   • Use a package manager to install mod_rewrite as a shared module

2. Add the following rewrite directives to the global server context to reject HTTP requests that do not conform to HTTP/1.1:

RewriteEngine On
RewriteCond %{THE_REQUEST} !HTTP/1\.1$
RewriteRule .* - [F]

3. For each virtual host or other section that needs to inherit these settings, add:

RewriteEngine On
RewriteOptions Inherit

Default Value

None documented

References

1. http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html

CIS Controls

Version 6

9.1 Limit Open Ports, Protocols, and Services Ensure that only ports, protocols, and services with validated business needs are running on each system.

Version 7

9.2 Ensure Only Approved Ports, Protocols and Services Are Running Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.

Profile

Level 1 | Scored