What is the most secure way to retrieve the system Drive.

Question

I know that the following should work:

Environment.GetEnvironmentVariable("windir", EnvironmentVariableTarget.Machine)

My problem with this call is that if for some reason someone decided to remove the "windir" Env Var , this won't work.

Is there an even more secure way to get the System drive?

Answer 1

Theres an environment variable called SystemDrive

C:\>SET SystemDrive
SystemDrive=C:

Answer 2

This one returns the path to the system directory (system32).

Environment.GetFolderPath(Environment.SpecialFolder.System)

You may be able to use that, then you don't need to rely on environment variables.

Answer 3

You can use the GetWindowsDirectory API to retrieve the windows directory.

Answer 4

string windir = Environment.SystemDirectory; // C:\windows\system32
string windrive = Path.GetPathRoot(Environment.SystemDirectory); // C:\

Note: This property internally uses the GetSystemDirectory() Win32 API. It doesn't rely on environment variables.

Answer 5

One thing i actually maybe misunderstand is that you want the System Drive, but by using "windir" you'll get the windows folder. So if you need a secure way to get the windows folder, you should use the good old API function GetWindowsDirectory.

Here is the function prepared for C# usage. ;-)

    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern uint GetWindowsDirectory(StringBuilder lpBuffer, uint uSize);

    private string WindowsDirectory()
    {
        uint size = 0;
        size = GetWindowsDirectory(null, size);

        StringBuilder sb = new StringBuilder((int)size);
        GetWindowsDirectory(sb, size);

        return sb.ToString();
    }

So if you really need the drive on which windows is running, you could afterwards call

System.IO.Path.GetPathRoot(WindowsDirectory());

Answer 6

Never read environment variables (any script or user can change them !)
The official method (MS internal, used by Explorer) is a Win32 api FAQ for decades (see Google groups, Win32, System api)