How a out-of process COM EXE register itself to Service Control Manager(SCM)?

DCOM and EXE

DCOM servers are often compiled as EXE executables. DCOM DLL can not execute by itself so there will be a surrogate process which executes the process and DLL will be loaded into the process. DCOM EXE server starts its execution along with a marcellng process. client's call and parameters are exchangd with the help of the marcellng process and LPC or RPC mechanim is used during the buffer/parameter change.

DCOM and SCM service

DCOM exe register its registry entries at the process of COM registration. DCOM server additionally register a service process in the service control manager (SCM). This service process will be started as soon as a Client executes CoCreateInstance/CoGetClassObject OLE API. This will be done through COM/DCOM/OLE framework and Windows registry entries provides the mapping of CLSID/progid to COM EXE server path.

SCM service APIs

SC_HANDLE WINAPI OpenSCManager(
  _In_opt_ LPCTSTR lpMachineName,
  _In_opt_ LPCTSTR lpDatabaseName,
  _In_     DWORD   dwDesiredAccess
);
SC_HANDLE WINAPI CreateService(
  _In_      SC_HANDLE hSCManager,
  _In_      LPCTSTR   lpServiceName,
  _In_opt_  LPCTSTR   lpDisplayName,
  _In_      DWORD     dwDesiredAccess,
  _In_      DWORD     dwServiceType,
  _In_      DWORD     dwStartType,
  _In_      DWORD     dwErrorControl,
  _In_opt_  LPCTSTR   lpBinaryPathName,
  _In_opt_  LPCTSTR   lpLoadOrderGroup,
  _Out_opt_ LPDWORD   lpdwTagId,
  _In_opt_  LPCTSTR   lpDependencies,
  _In_opt_  LPCTSTR   lpServiceStartName,
  _In_opt_  LPCTSTR   lpPassword
);
SC_HANDLE WINAPI OpenService(
  _In_ SC_HANDLE hSCManager,
  _In_ LPCTSTR   lpServiceName,
  _In_ DWORD     dwDesiredAccess
);
BOOL WINAPI ControlService(
  _In_  SC_HANDLE        hService,
  _In_  DWORD            dwControl,
  _Out_ LPSERVICE_STATUS lpServiceStatus
);
BOOL WINAPI DeleteService(
  _In_ SC_HANDLE hService
);
BOOL WINAPI CloseServiceHandle(
  _In_ SC_HANDLE hSCObject
);

DCOM service install

inline BOOL CServiceModule::Install()
{
    if (IsInstalled())
        return TRUE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);
    if (hSCM == NULL)
    {
        MessageBox(NULL, _T("Couldn't open service manager"), m_szServiceName, MB_OK);
        return FALSE;
    }

    // Get the executable file path
    TCHAR szFilePath[_MAX_PATH];
    ::GetModuleFileName(NULL, szFilePath, _MAX_PATH);

    SC_HANDLE hService = ::CreateService(
        hSCM, m_szServiceName, m_szDisplayName,
        SERVICE_ALL_ACCESS, SERVICE_WIN32_OWN_PROCESS,
        SERVICE_DEMAND_START, SERVICE_ERROR_NORMAL,
        szFilePath, NULL, NULL, _T("RPCSS\0"), NULL, NULL);

    if (hService == NULL)
    {
        ::CloseServiceHandle(hSCM);
        MessageBox(NULL, _T("Couldn't create service"), m_szServiceName, MB_OK);
        return FALSE;
    }

    ::CloseServiceHandle(hService);
    ::CloseServiceHandle(hSCM);
    return TRUE;
}
BOOL CServiceModule::IsInstalled()
{
    BOOL bResult = FALSE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

    if (hSCM != NULL)
    {
        SC_HANDLE hService = ::OpenService(hSCM, m_szServiceName, SERVICE_QUERY_CONFIG);
        if (hService != NULL)
        {
            bResult = TRUE;
            ::CloseServiceHandle(hService);
        }
        ::CloseServiceHandle(hSCM);
    }
    return bResult;
}

DCOM service uninstall

inline BOOL CServiceModule::Uninstall()
{
    if (!IsInstalled())
        return TRUE;

    SC_HANDLE hSCM = ::OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);

    if (hSCM == NULL)
    {
        MessageBox(NULL, _T("Couldn't open service manager"), m_szServiceName, MB_OK);
        return FALSE;
    }

    SC_HANDLE hService = ::OpenService(hSCM, m_szServiceName, SERVICE_STOP | DELETE);

    if (hService == NULL)
    {
        ::CloseServiceHandle(hSCM);
        MessageBox(NULL, _T("Couldn't open service"), m_szServiceName, MB_OK);
        return FALSE;
    }
    SERVICE_STATUS status;
    ::ControlService(hService, SERVICE_CONTROL_STOP, &status);

    BOOL bDelete = ::DeleteService(hService);
    ::CloseServiceHandle(hService);
    ::CloseServiceHandle(hSCM);

    if (bDelete)
        return TRUE;

    MessageBox(NULL, _T("Service could not be deleted"), m_szServiceName, MB_OK);
    return FALSE;
}

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