The production IIS 8.5 web server must utilize SHA2 encryption for the Machine Key.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-76731	IISW-SV-000137	SV-91427r1_rule		Medium

Description
The Machine Key element of the ASP.NET web.config specifies the algorithm and keys that ASP.NET will use for encryption. The Machine Key feature can be managed to specify hashing and encryption settings for application services such as view state, forms authentication, membership and roles, and anonymous identification. Ensuring a strong encryption method can mitigate the risk of data tampering in crucial functional areas such as forms authentication cookies, or view state.

Description

The Machine Key element of the ASP.NET web.config specifies the algorithm and keys that ASP.NET will use for encryption. The Machine Key feature can be managed to specify hashing and encryption settings for application services such as view state, forms authentication, membership and roles, and anonymous identification. Ensuring a strong encryption method can mitigate the risk of data tampering in crucial functional areas such as forms authentication cookies, or view state.

STIG	Date
IIS 8.5 Server Security Technical Implementation Guide	2018-01-03

Details

Check Text ( C-76387r1_chk )
Open the IIS 8.5 Manager. Click the IIS 8.5 web server name. Double-click the "Machine Key" icon in the website Home Pane. Verify "HMACSHA256" is selected for the Validation method and "Auto" is selected for the Encryption method. If "HMACSHA256" is not selected for the Validation method and/or "Auto" is not selected for the Encryption method, this is a finding.

Fix Text (F-83427r1_fix)
Open the IIS 8.5 Manager. Click the IIS 8.5 web server name. Double-click the "Machine Key" icon in the web server Home Pane. Set the Validation method to "HMACSHA256". Set the Encryption method to "Auto". Click "Apply" in the "Actions" pane.