PATH in child process includes Windows Terminal Preview installation directory, if started via Win+R wt.exe

[KalleOlaviNiemitalo]

Environment

Windows build number: Microsoft Windows [Version 10.0.19041.388]
Windows Terminal version (if applicable): Windows Terminal Preview 1.2.2022.0

Steps to reproduce

1. Enable the wt.exe app execution alias of Windows Terminal Preview.
2. Press Windows+R to open the Run dialog box.
3. Type wt.exe and press Enter to start Windows Terminal Preview.
4. In Windows Terminal Preview, start the Command Prompt profile.
5. In the Command Prompt session, type PATH and press Enter.

Expected behavior

The displayed value of PATH does not include the directory where Windows Terminal Preview was installed.

Actual behavior

C:\Program Files\WindowsApps\Microsoft.WindowsTerminalPreview_1.2.2022.0_x64__8wekyb3d8bbwe is the first directory in PATH.

Notes

This is presumably caused by the Registry values that were created by AppXSvc when Windows Terminal Preview was installed:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\wt.exe]
@="C:\\Program Files\\WindowsApps\\Microsoft.WindowsTerminalPreview_1.2.2022.0_x64__8wekyb3d8bbwe\\wt.exe"
"Path"="C:\\Program Files\\WindowsApps\\Microsoft.WindowsTerminalPreview_1.2.2022.0_x64__8wekyb3d8bbwe"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\wt.exe]
@="C:\\Program Files\\WindowsApps\\Microsoft.WindowsTerminalPreview_1.2.2022.0_x64__8wekyb3d8bbwe\\wt.exe"
"Path"="C:\\Program Files\\WindowsApps\\Microsoft.WindowsTerminalPreview_1.2.2022.0_x64__8wekyb3d8bbwe"

According to Application Registration, ShellExecuteEx prepends the data of the "Path" Registry value to the PATH environment variable of the new process. That seems unnecessary here, as selecting Windows Terminal Preview from the Start menu does not add to PATH.

Because non-packaged processes of users have no access to the "C:\Program Files\WindowsApps" directory, this addition to PATH perhaps does not cause problems. However, if wt.exe is run as administrator, then the PATH addition could cause a process in the terminal session to load DLLs from the installation directory of Windows Terminal Preview. (If a packaged application is run within the terminal session, then that too would have access to the directory, but Search Order for Windows Store apps looks like the PATH environment variable will not affect DLL loading in that case.)

Related to #6860, #6748, #7188. Found while searching for possible causes of #7195.

[DHowett]

So, a few notes.

• I think this is harmless. There's no executable in our package that the user shouldn't be able to launch, and nothing that will incorrectly eclipse things that are on their PATHs.
• We don't have any control over this.
• I can't find this entry in PATH when I elevate wt.exe
• Packaged applications don't follow the traditional DLL search order, so I don't think it likely that they'll inherit WT's libraries

[DHowett]

Incidentally, this and the last seven issues are the first (and second through seventh) times I've ever heard of App Paths, and I didn't know the system was maintaining it on our behalf.

[KalleOlaviNiemitalo]

• I can't find this entry in PATH when I elevate wt.exe

How do you elevate it? If I type wt.exe in the Run dialog box and press Ctrl+Shift+Enter, then the WT installation directory does appear in PATH in the Command Prompt session.

[DHowett]

Yep, using Ctrl+Shift+Enter from the Run dialog.

[KalleOlaviNiemitalo]

We don't have any control over this.

I imagine Windows Terminal could explicitly delete its installation directory from PATH in the environment block that it passes to CreateProcess.

Or use CreateEnvironmentBlock as suggested in #1125, instead of copying PATH and other variables from the environment of the WindowsTerminal.exe process.

Yep, using Ctrl+Shift+Enter from the Run dialog.

That's strange… Are you using the same version of Windows 10? Does the PATH change even get to the WindowsTerminal.exe process? Process Monitor filtering with Operation = Process Start is handy for checking this.