Elevating privileges doesn't work with UseShellExecute=false

Question

I want to start a child process (indeed the same, console app) with elevated privileges but with hidden window.

I do next:

var info = new ProcessStartInfo(Assembly.GetEntryAssembly().Location)
{
    UseShellExecute = true, // !
    Verb = "runas", 
};

var process = new Process
{
    StartInfo = info
};

process.Start();

and this works:

var identity = new WindowsPrincipal(WindowsIdentity.GetCurrent());
identity.IsInRole(WindowsBuiltInRole.Administrator); // returns true

But UseShellExecute = true creates a new window and I also I can't redirect output.

So when I do next:

var info = new ProcessStartInfo(Assembly.GetEntryAssembly().Location)
{
    RedirectStandardError = true,
    RedirectStandardOutput = true,
    UseShellExecute = false, // !
    Verb = "runas"
};

var process = new Process
{
    EnableRaisingEvents = true,
    StartInfo = info
};

DataReceivedEventHandler actionWrite = (sender, e) =>
{
    Console.WriteLine(e.Data);
};

process.ErrorDataReceived += actionWrite;
process.OutputDataReceived += actionWrite;

process.Start();
process.BeginOutputReadLine();
process.BeginErrorReadLine();
process.WaitForExit();

This doesn't elevate privileges and code above returns false. Why??

BTW, you can write `DataReceivedEventHandler actionWrite = ...` and `process.ErrorDataReceived += actionWrite`. — SLaks, Aug 29 '10 at 19:35
Can you test using UseShellExecute = true, Verb = "runas", and ErrorDataReceived events as @SLaks comment ? — Kiquenet, Oct 15 '14 at 17:02

score 22 · Accepted Answer · edited May 23 '17 at 10:31

22

ProcessStartInfo.Verb will only have an effect if the process is started by ShellExecuteEx(). Which requires UseShellExecute = true. Redirecting I/O and hiding the window can only work if the process is started by CreateProcess(). Which requires UseShellExecute = false.

Well, that's why it doesn't work. Not sure if forbidding to start a hidden process that bypasses UAC was intentional. Probably. Very probably.

Check this Q+A for the manifest you need to display the UAC elevation prompt.

edited May 23 '17 at 10:31

Community

1
1

answered Aug 29 '10 at 19:58

Hans Passant

922,412
146
1,693
2,536

Thank you very much for WinAPI behind-the-scene description. How do you think is it possible to get elevated privileges on demand for a process with hidden window? Or this is mutually exclusive things? – abatishchev Aug 30 '10 at 13:10
And is it possible to switch on/off using manifest? I.e. when I start my app first time (manually) - don't use a manifest, when second (programmatically) - force to use. – abatishchev Aug 30 '10 at 13:12
Starting a process with elevated privileges without the user knowing about it is not possible. You need a separate .exe so that it has its own manifest. Basically you only need the Main() method. – Hans Passant Aug 30 '10 at 13:18
I don't want to hide process launch from user, I still need UAC confirm from him, I just want to hide started process window. I think this isn't possible too, right? – abatishchev Aug 30 '10 at 14:50
2

Hmm... this is rather frustrating. – tofutim May 21 '13 at 00:48

score 12 · Answer 2 · answered Mar 17 '16 at 11:27

12

In my case, it was ok to get the outputs once the elevated child process is done. Here's the solution I came up. It uses a temporary file :

var output = Path.GetTempFileName();
var process = Process.Start(new ProcessStartInfo
{
    FileName = "cmd",
    Arguments = "/c echo I'm an admin > " + output, // redirect to temp file
    Verb = "runas", // UAC prompt
    UseShellExecute = true,
});
process.WaitForExit();
string res = File.ReadAllText(output);
// do something with the output
File.Delete(output);

answered Mar 17 '16 at 11:27

tpol

910
10
16

this actually appears to be working for me. convoluted details (windows 10, F#) - gist at https://gist.github.com/ImaginaryDevelopment/f4bc33ae75bdf29e5aad8fd4045f193d – Maslow Dec 13 '16 at 16:44
The accepted answer is an explanation, this is a solution.. +1 – caesay Jun 10 '17 at 03:26

score 0 · Answer 3 · edited May 23 '17 at 12:02

0

Check this answer.

This seems to provide a workaround. But I recommend to try other methods like Named Pipes when you have access to source code of the child process.

edited May 23 '17 at 12:02

Community

1
1

answered Oct 15 '13 at 13:07

Masood Khaari

2,911
2
23
40

1

I haven't tested the UAC article approach, though it contains a sample by itself. But if you mean a sample for Named Pipes, you can easily find many of them (like [this](http://stackoverflow.com/questions/13806153/example-of-named-pipes) or [this](http://www.codeproject.com/Tips/492231/Csharp-Async-Named-Pipes)) with a little search. The point is that like I/O redirection, you can use textual streams with Named Pipes too, to send and receive data (even if the two processes reside on different machines). Of course you have to deal with some nuances to get a fully working application. – Masood Khaari Aug 11 '14 at 13:29
@abatishchev IMHO, better using Trace to File, not redirect output, verb = runas. Named Pipes is much more complex and complex to debugging easy. – Kiquenet Oct 15 '14 at 17:13

Elevating privileges doesn't work with UseShellExecute=false

3 Answers3

Linked

Related