Question

I am trying to open a process handle in C# using the OpenProcess function as follows:

IntPtr hProcess = OpenProcess(0x410, false, pid);

where pid is the process ID of the process I would like to open.

When called on a PID whose user is “NT AUTHORITY\SYSTEM” (on Vista x64), the above call fails, with an “Access Denied” error.

How do I get a handle of such a process?

What makes me think this is at all possible is that the .NET System.Diagnostics.Process class seems to be able to operate on such processes. For example, Process.ProcessName works fine on such processes. Under the hood, it calls Process.MainModule.ModuleName, which ultimately calls OpenProcess in exactly the same way I do. However, System.Diagnostics doesn’t get the “Access Denied” error whereas I do.

Curiously, anything that attempts to get the handle of the process into my application also throws the exception. For example, Process.Handle and Process.MainModule both throw an “Access Denied” error, despite the fact that Process.MainModule clearly succeeds when called indirectly through Process.ProcessName.

Does System.Diagnostics operate under some sort of raised privileges? How can I raise the privileges of my application to be able to do the same?

Answer 1

How do I get a handle of such a process?
How can I raise the privileges of my application to be able to do the same?

Apparently the application needs to give itself the SeDebugPrivilege: How To Use the SeDebugPrivilege to Acquire Any Process Handle

However it’s not a great idea for a general-purpose app to rely on this because SeDebugPrivilege is equivalent to administrator privileges (security-wise).

I’m still not sure how exactly System.Diagnostics exposes Process.ProcessName without requiring the SeDebugPrivilege, but then I know next to nothing about the code security features of .NET.