NVDA no longer becomes unusable when interacting with a protected process such as 1Password

[michaelDCurran]

Link to issue number:

None

Summary of the issue:

During the conversion to 64 bit, the ctypes definition of WaitForSingleObject was tightened up. This caused related errors in NVDA previously hidden to be surfaced, such as continuing to keep an appModule alive with an invalid process handle. this was addressed.
However, a similar issue was also surfaced where although we successfully open a process, asking for the SYNCHRONIZE access right, once we go to check if the process is dead by calling WaitforSingleObject(handle, 0) this fails with access denied. We never actually got the SYNCHRONIZE access right.
This is most serious when trying to interact with 1Password, where it becomes totally unusable and NVDA continuously torws the error:

  File "appModuleHandler.pyc", line 622, in _get_isAlive
  File "winKernel.pyc", line 344, in waitForSingleObject
PermissionError: [WinError 5] Access is denied.

This error is also randomly seen from time to time when alt tabbing between windows. There may be another protected Windows process which happens to be noticed by NVDA.

Description of user facing changes:

NVDA no longer becomes unusable when interacting with a protected process.

Description of developer facing changes:

Description of development approach:

AppModule.isAlive: specifically handle the case when WaitForSingleObject fails, and the related error is ERROR_ACCESS_DENIED. Log a debugWarning the first time, but then set a special _liveForEver instance variable on the AppModule to true, communicating to isAlive that it should no longer check. We are not going to magically get access, so all we can do is assume it continues to be alive.

The debugWarning looks like:

Access denied waiting on Process handle 2832 for AppModule(1password, appName='1password', processID=20012), cannot verify dead, marking as living for ever.

Testing strategy:

• Open 1Password and interact with it. NVDA no longer throws errors making 1Password and NVDA unusable.
• Use NvDA for an extended period to confirm the random PermissionError exceptions have disappeared.

Known issues with pull request:

AppModules for Protected processes will stay around for the lifetime of NvDA. In 1Password's case, its process seems to stay around a lot anyway. And any other protected process probably has no specific appModule.

Code Review Checklist:

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

[Copilot]

Pull Request Overview

This PR fixes NVDA becoming unusable when interacting with protected processes like 1Password by properly handling access denied errors when checking process liveness.

• Adds graceful handling of ERROR_ACCESS_DENIED when waiting on process handles
• Implements a _liveForEver flag to mark protected processes as permanently alive
• Logs debug warnings for access denied scenarios instead of crashing

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
source/winKernel.py	Adds ERROR_ACCESS_DENIED constant for error handling
source/appModuleHandler.py	Implements _liveForEver flag and error handling for protected processes

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[michaelDCurran]

We could, but would involve checking where it was used, changing references, possible deprecations. I'd prefer to just fix this particular bug in this pr :)