The IIS 8.5 website must have resource mappings set to disable the serving of certain file types.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-76801	IISW-SI-000216	SV-91497r1_rule		Medium

Description
Resource mapping is the process of tying a particular file type to a process in the web server that can serve that type of file to a requesting client and to identify which file types are not to be delivered to a client. By not specifying which files can and which files cannot be served to a user, the web server could deliver to a user web server configuration files, log files, password files, etc. The web server must only allow hosted application file types to be served to a user and all other types must be disabled.

Description

Resource mapping is the process of tying a particular file type to a process in the web server that can serve that type of file to a requesting client and to identify which file types are not to be delivered to a client. By not specifying which files can and which files cannot be served to a user, the web server could deliver to a user web server configuration files, log files, password files, etc. The web server must only allow hosted application file types to be served to a user and all other types must be disabled.

STIG	Date
IIS 8.5 Site Security Technical Implementation Guide	2018-09-18

Details

Check Text ( C-76457r1_chk )
For "Handler Mappings", the ISSO must document and approve all allowable file extensions the website allows (white list) and denies (black list) by the website. The white list and black list will be compared to the "Handler Mappings" in IIS 8.5. "Handler Mappings" at the site level take precedence over "Handler Mappings" at the server level. Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Double-click "Request Filtering". If any file name extensions from the black list have "Allowed" set to "True", this is a finding.

Check Text ( C-76457r1_chk )

For "Handler Mappings", the ISSO must document and approve all allowable file extensions the website allows (white list) and denies (black list) by the website. The white list and black list will be compared to the "Handler Mappings" in IIS 8.5. "Handler Mappings" at the site level take precedence over "Handler Mappings" at the server level.

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Open the IIS 8.5 Manager.

Double-click "Request Filtering".

If any file name extensions from the black list have "Allowed" set to "True", this is a finding.

Fix Text (F-83497r1_fix)
Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Click the site name under review. Double-click "Request Filtering". For any file name extensions from the black list which have "Allowed" set to "True", remove the file name extension. Select "Deny File Name Extension" from the "Actions" pane. Add each file name extension from the black list. Select "Apply" from the "Actions" pane.

Fix Text (F-83497r1_fix)

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Open the IIS 8.5 Manager.

Click the site name under review.

Double-click "Request Filtering".

For any file name extensions from the black list which have "Allowed" set to "True", remove the file name extension.

Select "Deny File Name Extension" from the "Actions" pane.

Add each file name extension from the black list.

Select "Apply" from the "Actions" pane.