cyberstrikeus Ensure HTTP Request Methods Are Restricted
Description
Use the Apache <LimitExcept> directive to restrict unnecessary HTTP request methods of the web server so it only accepts and processes the GET, HEAD, POST and OPTIONS HTTP request methods.
Rationale
The HTTP 1.1 protocol supports several request methods which are rarely used and potentially high risk. For example, methods such as PUT and DELETE are rarely used and should be disabled in keeping with the security principle of minimizing features and options. Also, since these methods are rarely used, they typically have to modify resources on the web server, they should be explicitly disallowed. For normal web server operation, you will typically need to allow only the GET, HEAD and POST request methods. This will allow for downloading web pages and submitting information to web forms. The OPTIONS request method will also be allowed as it is used to request which HTTP request methods are allowed. Unfortunately, the Apache <LimitExcept> directive does not deny the TRACE request method. The TRACE request method is disallowed in another benchmark recommendation with the TraceEnable directive.
Impact
None documented
Audit Procedure
Perform the following to determine if the recommended state is implemented:
- Locate the Apache configuration files and included configuration files.
- Search for all
<Directory>directives other than the OS root directory. - Ensure that group contains a single
Orderdirective within the<Directory>directive with a value ofdeny,allow. - Verify the
<LimitExcept>directive does not include any HTTP methods other thanGET,POST, andOPTIONS. (It may contain fewer methods.)
Remediation
Perform the following to implement the recommended state:
- Locate the Apache configuration files and included configuration files.
- Search for the directive on the document root directory, such as:
<Directory "/usr/local/apache2/htdocs">
. . .
</Directory>
- Ensure that the access control order within the
<Directory>directive isdeny,allow.
Order allow,deny
- Add a directive as shown below within the group of document root directives.
# Limit HTTP methods to standard methods. Note: Does not limit TRACE
<LimitExcept GET POST OPTIONS>
Deny from all
</LimitExcept>
- Search for other directives in the Apache configuration files in places other than the root directory, and add the same directives to each. It is very important to understand that the directives are based on the OS file system hierarchy as accessed by Apache and not the hierarchy of the locations within web site URLs.
<Directory "/usr/local/apache2/cgi-bin">
. . .
Order allow,deny
# Limit HTTP methods
<LimitExcept GET POST OPTIONS>
Deny from all
</LimitExcept>
</Directory>
Default Value
No limits on HTTP methods
References
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