The IIS 10.0 website must generate unique session identifiers that cannot be reliably reproduced.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-218751	IIST-SI-000223	SV-218751r558649_rule		Medium

Description
Communication between a client and the web server is done using the HTTP protocol, but HTTP is a stateless protocol. To maintain a connection or session, a web server will generate a session identifier (ID) for each client session when the session is initiated. The session ID allows the web server to track a user session and, in many cases, the user, if the user previously logged into a hosted application. By being able to guess session IDs, an attacker can easily perform a man-in-the-middle attack. To truly generate random session identifiers that cannot be reproduced, the web server session ID generator, when used twice with the same input criteria, must generate an unrelated random ID. The session ID generator must be a FIPS 140-2-approved generator.

Description

Communication between a client and the web server is done using the HTTP protocol, but HTTP is a stateless protocol. To maintain a connection or session, a web server will generate a session identifier (ID) for each client session when the session is initiated. The session ID allows the web server to track a user session and, in many cases, the user, if the user previously logged into a hosted application. By being able to guess session IDs, an attacker can easily perform a man-in-the-middle attack. To truly generate random session identifiers that cannot be reproduced, the web server session ID generator, when used twice with the same input criteria, must generate an unrelated random ID. The session ID generator must be a FIPS 140-2-approved generator.

STIG	Date
Microsoft IIS 10.0 Site Security Technical Implementation Guide	2021-12-28

Details

Check Text ( C-20224r311151_chk )
Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name. Under the "ASP.NET" section, select "Session State". Under "Session State" Mode Settings, verify the "In Process" mode is selected. If the "In Process" mode is selected, this is not a finding. Alternative method: Click the site name. Select "Configuration Editor" under the "Management" section. From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState". Verify the "mode" reflects "InProc". If the "mode" is not set to "InProc", this is a finding. If the system being reviewed is part of a Web Farm, interview the System Administrator to ensure Session State Tracking is enabled via a SQL server, or other means. If Session State Tracking is enabled on the Web Farm, this is not a finding.

Check Text ( C-20224r311151_chk )

Follow the procedures below for each site hosted on the IIS 10.0 web server:

Open the IIS 10.0 Manager.

Click the site name.

Under the "ASP.NET" section, select "Session State".

Under "Session State" Mode Settings, verify the "In Process" mode is selected.

If the "In Process" mode is selected, this is not a finding.

Alternative method:

Click the site name.

Select "Configuration Editor" under the "Management" section.

From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState".

Verify the "mode" reflects "InProc".

If the "mode" is not set to "InProc", this is a finding.

If the system being reviewed is part of a Web Farm, interview the System Administrator to ensure Session State Tracking is enabled via a SQL server, or other means. If Session State Tracking is enabled on the Web Farm, this is not a finding.

Fix Text (F-20222r311152_fix)
Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name. Under the ASP.NET section, select "Session State". Under "Session State" Mode Settings, select the "In Process" mode.