Vulnerability Discussion

The ability to log in to another user's active or locked session must be disabled.

macOS has a privilege that can be granted to any user that will allow that user to unlock active users' sessions. Disabling the administrator's and/or user's ability to log in to another user's active and locked session prevents unauthorized people from viewing potentially sensitive and/or personal information.

NOTE: Configuring this setting will change the user experience and disable TouchID from unlocking the screen saver. To restore the user experience and allow TouchID to unlock the screen saver, run "/usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow screenUnlockMode -int 1". This setting can also be deployed with a configuration profile.

Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000109-GPOS-00056

Check

Verify the macOS system is configured to disable login to other users' active and locked sessions with the following command:

/usr/bin/security authorizationdb read system.login.screensaver 2>&1 | /usr/bin/grep -c '<string>authenticate-session-owner</string>'

If the result is not "1", this is a finding.

Fix

Configure the macOS system to disable login to other users' active and locked sessions with the following command:

/usr/bin/security authorizationdb write system.login.screensaver "authenticate-session-owner"