Prevent Object Navigation Outside of the Lock Screen

[seanbudd]

Link to issue number:

None, follow up on #5269

Summary of the issue:

On earlier Windows 10 builds, the top-level Window (Role.WINDOW) of the lock screen cannot directly navigate to the system with object navigation, but its parent can. This was fixed in a commit addressing #5269.

On Windows 11 and newer Windows 10 builds, the top-level Window can directly navigate to the system with object navigation.

STR:

1. Press Windows+L
2. press containing object (NVDA+numpad8/NVDA+shift+upArrow),
3. then you can use next object (NVDA+numpad6/NVDA+shift+rightArrow) to navigate the system.

On Windows 10 and 11, using "Navigate to the object under the mouse" (NVDA+numpadMultiply/NVDA+shift+n), you can navigate outside to the system from the lock screen.

Microsoft is aware of this issue.

Description of how this pull request fixes the issue:

This PR adds a function which checks if the lockapp is the foreground window, and if so, if a given object is outside of the lockapp.
To prevent focus objects being set or used for navigation, this function is utilised in various api methods.

An overlay class is also added which prevents navigation and announcement of content outside of the lockapp.

This PR also adds GlobalCommands.script_navigatorObject_devInfo to the allowed commands on the lockscreen to aid with debugging.
This command should be safe as:

1. The command only logs objects it can navigate to
2. The log viewer cannot be accessed from the lockscreen

Testing strategy:

Manual testing on Windows 11, Windows 10 21H2, Windows 10 1809

• Attempt to navigate outside the top level window of the lock screen using object navigation using STR
• Ensure the lock screen can still be navigated with object navigation

Known issues with pull request:

Performing 2 windows windll at every attempt to object navigate might add latency to object navigation.
This is mitigated by checking first if the lockapp appModule is running, however the lockapp process stays alive for sometime and cannot be used by itself.

There is no function you can call to determine whether the workstation is locked.
https://docs.microsoft.com/en-gb/windows/win32/api/winuser/nf-winuser-lockworkstation
https://stackoverflow.com/questions/34514644/in-python-3-how-can-i-tell-if-windows-is-locked

An advisory is required to be sent out for earlier NVDA versions.

Change log entries:

Bug fixes

- Security fix: Prevent object navigation outside of the lockscreen on Windows 10 and Windows 11.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English