When the security option "Shutdown: Allow system to be shutdown without having to log on" (in the local security policy) is set to "Disable", and the power management setting "When I press the power button" is set to "Shut Down", it is possible for an unauthenticated user to press the power button at the Windows logon screen and gracefully shutdown the system. The explanation of this security option, taken from the local security policy, is as follows: "Shutdown: Allow system to be shut down without having to log on This security setting determines whether a computer can be shut down without having to log on to Windows. When this policy is enabled, the Shut Down command is available on the Windows logon screen. When this policy is disabled, the option to shut down the computer does not appear on the Windows logon screen. In this case, *users must be able to log on to the computer successfully and have the Shut down the system user right before they can perform a system shutdown*. Default on workstations: Enabled. Default on servers: Disabled." Note the text between the asterisks. While this bug isn't necessarily a software flaw allowing for an intrusion into the system in a traditional sense, it does set a bad precedence in that power management has a free pass to bypass local security policy and perform actions expressly against the defined policy. It appears that the only impact the use of this security option actually has is enabling or disabling the display of the "power button" on the Windows logon screen (locally only - this setting has no affect on remote desktop connections - the "power button" is not displayed in either case), not actually preventing anyone from (gracefully) shutting down the system without logging in. I reported this to the MSRC on 6/25/2008 and their stance was that this wasn't a security vulnerability, but was likely a bug, and was passed directly to the product team to investigate through their normal bug triage process. After some back and forth, there was silence, and I let them know I was going to release this information to the community. This was tested on Windows Vista SP1 (32-bit). -- Abe Getchell me@xxxxxxxxxxxxxxx https://abegetchell.com/
