CreateProcessAsUser with elevated privileges - windows

Question

My service is running under local system permissions, and needs to start an application with administrator permissions in the user session.
What I got is:
WTSGetActiveConsoleSessionID()
WTSQueryUserToken for session ID
CreateProcessAsUser
The problem is I need to run the process (Step 3) as an administrator, without asking the user for the administrator's password.
On Linux systems I would simply do a "su ", but to achieve this on a Windows system?

Answer 1

I've finally found the solution to manage this:
public void launchProcessInUserSession(String process) throws WindowsAPIException {
final DWORD interactiveSessionId = kernel32.WTSGetActiveConsoleSessionId();
final DWORD serviceSessionId = getCurrentSessionId();
final HANDLEByReference pExecutionToken = new HANDLEByReference();
final HANDLE currentProcessToken = getCurrentProcessToken();
try {
final HANDLE interactiveUserToken = getUserToken(interactiveSessionId);
checkAPIError(advapi32.DuplicateTokenEx(currentProcessToken, WinNT.TOKEN_ALL_ACCESS, null, SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation,
WinNT.TOKEN_TYPE.TokenPrimary, pExecutionToken));
} finally {
kernel32.CloseHandle(currentProcessToken);
}
final HANDLE executionToken = pExecutionToken.getValue();
try {
checkAPIError(advapi32.SetTokenInformation(executionToken, TOKEN_INFORMATION_CLASS.TokenSessionId, new IntByReference(interactiveSessionId.intValue()), DWORD.SIZE));
final WinBase.STARTUPINFO si = new WinBase.STARTUPINFO();
final PROCESS_INFORMATION processInfo = new WinBase.PROCESS_INFORMATION();
final int dwFlags = WinBase.DETACHED_PROCESS;
checkAPIError(advapi32.CreateProcessAsUser(executionToken, null, process, null, null, false, dwFlags, null, null, si, processInfo));
LOGGER.debug("Execution done. Process ID is {}", processInfo.dwProcessId);
} finally {
kernel32.CloseHandle(executionToken);
}
}

Answer 2

I need to run the process (Step 3) as administrator, without asking the user for the administrator's password.
If it were possible for a low privileged user to execute code as a privileged user, then the system's security model would be broken. If you want to execute code with administrator privileges then you need to supply appropriate credentials, at some point.
Your proposed plan of action has you calling CreateProcessAsUser passing the user token for a low privileged user. This plan, as itemized in the question, cannot succeed. Since the user token you will provide is that of the low privileged user, the process will not be able to perform administrative tasks.
You will need to provide, one way or another, credentials for a user with administrative rights.