Title

The production IIS 10.0 web server must utilize SHA2 encryption for the Machine Key. (Cat II impact)

Discussion

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.

Check Content

Open the IIS 10.0 Manager. Click the IIS 10.0 web server name. Double-click the "Machine Key" icon in the website Home Pane. Verify "HMACSHA256" or stronger encryption is selected for the Validation method and "Auto" is selected for the Encryption method. If "HMACSHA256" or stronger encryption is not selected for the Validation method and/or "Auto" is not selected for the Encryption method, this is a finding. If .NET is not installed, this is Not Applicable.

Fix Text

Open the IIS 10.0 Manager. Click the IIS 10.0 web server name. Double-click the "Machine Key" icon in the web server Home Pane. Set the Validation method to "HMACSHA256" or stronger. Set the Encryption method to "Auto". Click "Apply" in the "Actions" pane.

Additional Identifiers

Rule ID: SV-218807r879642_rule

Vulnerability ID: V-218807

Group Title: SRG-APP-000231-WSR-000144

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.