How to use OpenProcessToken, AdjustTokenPrivileges, and GetExitCodeProcess in VC++ 2005

Question

I read a couple of posts on how to check if a process has exited from a different process (I realize some people get hung up on semantics here, but just humor me) and I tried to implement it but am running into the error code 5 ("ERROR_ACCESS_DENIED") all over the place.

Here is what I do.

1) Process 1 (P1) launches process 2 and writes to a shared memory location its own PID.

2) Process 2 (P2) reads the PID from shared memory

3) P2 calls OpenProcess(...) with P1's PID to save a handle that it can check later.

4) P2 calls GetExitCodeProcess(...) with P1's PID repeatedly and checks for a STILL_ACTIVE code.

In the above method, I keep getting the ACCESS_DENIED error on GetExitCodeProcess. I've tried modifying P2's privileges by using the below code from MSDN's docs:

HANDLE proc_h = OpenProcess(SYNCHRONIZE, FALSE, GetCurrentProcessId());
HANDLE hToken;
OpenProcessToken(proc_h, TOKEN_ADJUST_PRIVILEGES, &hToken);

LookupPrivilegeValue(NULL, lpszPrivilege, &luid );

tp.PrivilegeCount = 1;
tp.Privileges[0].Luid = luid;
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
// Enable the privilege
AdjustTokenPrivileges(hToken, 
                      FALSE, 
                      &tp, 
                      sizeof(TOKEN_PRIVILEGES), 
                      (PTOKEN_PRIVILEGES) NULL, 
                      (PDWORD) NULL);

But I keep getting the ACCESS_DENIED error on the call to OpenProcessToken(...) method. So does this indicate some sort of system level hurdle? I do have admin rights on my machine and I'm running XP.

Thanks in advance for any help.

Can you post your code that is opening the process handle for P1 in P2? Are you specifying the PROCESS_QUERY_INFORMATION flag in the desisredAccess parameter to OpenPRocess? — Bukes, Jan 17 '12 at 16:39
@Bukes, hmjd guessed the problem. I was using the SYNCHRONIZE permissions and not PROCESS_QUERY_INFORMATION. — Ian, Jan 17 '12 at 18:16

score 4 · Accepted Answer · answered Jan 17 '12 at 16:43

The handle passed to GetExitCodeProcess requires PROCESS_QUERY_INFORMATION access right. The following works fine:

int main(int a_argc, char** a_argv)
{
    int pid = atoi(*(a_argv + 1));

    HANDLE h = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);

    if (NULL != h)
    {
        Sleep(2000);
        DWORD exit_code;
        if (FALSE == GetExitCodeProcess(h, &exit_code))
        {
            std::cerr << "GetExitCodeProcess() failure: " <<
                GetLastError() << "\n";
        }
        else if (STILL_ACTIVE == exit_code)
        {
            std::cout << "Still running\n";
        }
        else
        {
            std::cout << "exit code=" << exit_code << "\n";
        }
    }
    else
    {
        std::cerr << "OpenProcess() failure: " << GetLastError() << "\n";
    }

    return 0;
}

Instead of polling on GetExitCodeProcess open the handle with SYNCHRONIZE and wait for it to exit:

int main(int a_argc, char** a_argv)
{
    int pid = atoi(*(a_argv + 1));

    HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION, FALSE, pid);

    if (NULL != h)
    {
        WaitForSingleObject(h, 5000); // Change to 'INFINITE' wait if req'd
        DWORD exit_code;
        if (FALSE == GetExitCodeProcess(h, &exit_code))
        {
            std::cerr << "GetExitCodeProcess() failure: " <<
                GetLastError() << "\n";
        }
        else if (STILL_ACTIVE == exit_code)
        {
            std::cout << "Still running\n";
        }
        else
        {
            std::cout << "exit code=" << exit_code << "\n";
        }
    }
    else
    {
        std::cerr << "OpenProcess() failure: " << GetLastError() << "\n";
    }

    return 0;
}

score 1 · Answer 2 · answered Jan 17 '12 at 16:35

1

OpenProcesstoken requires PROCESS_QUERY_INFORMATION you are opening the process with only SYNCHRONIZE access. See if you add | PROCESS_QUERY_INFORMATION if it works.

answered Jan 17 '12 at 16:35

rerun

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score 1 · Answer 3 · answered Jan 17 '12 at 16:41

If you just want P2 to do something when P1 exits, there's another way that's probably rather easier: have P1 create a pipe and let P2 inherit a handle to that pipe. In P2, execute a read from the pipe. When P2's call to ReadFile returns with an error of ERROR_BROKEN_PIPE, P1 has exited.

How to use OpenProcessToken, AdjustTokenPrivileges, and GetExitCodeProcess in VC++ 2005

3 Answers3