命名核心對象有一種問題：任何程式都可以建立一個命名對象，這樣如果某個程式要實作單例運作而建立了一個核心對象，這種情況下另一程式也建立了同名的核心對象時，該單例程式就無法正常運作了。這是DoS攻擊的一種。
void CheckInstances()
{//檢查執行個體
// Create the boundary descriptor
g_hBoundary = CreateBoundaryDescriptor(g_szBoundary, 0);
// Create a SID corresponding to the Local Administrator group
BYTE localAdminSID[SECURITY_MAX_SID_SIZE];
PSID pLocalAdminSID = &localAdminSID;
DWORD cbSID = sizeof(localAdminSID);
if (!CreateWellKnownSid(
WinBuiltinAdministratorsSid, NULL, pLocalAdminSID, &cbSID)
)
{
AddText(TEXT("AddSIDToBoundaryDescriptor failed: %u\r\n"),
GetLastError());
return;
}
// Associate the Local Admin SID to the boundary descriptor
// --> only applications running under an administrator user
// will be able to access the kernel objects in the same namespace
if (!AddSIDToBoundaryDescriptor(&g_hBoundary, pLocalAdminSID))
// Create the namespace for Local Administrators only
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.bInheritHandle = FALSE;
if (!ConvertStringSecurityDescriptorToSecurityDescriptor(
TEXT("D:(A;;GA;;;BA)"),
SDDL_REVISION_1, &sa.lpSecurityDescriptor, NULL))
AddText(TEXT("Security Descriptor creation failed: %u\r\n"), GetLastError());
g_hNamespace =
CreatePrivateNamespace(&sa, g_hBoundary, g_szNamespace);
// Don't forget to release memory for the security descriptor
LocalFree(sa.lpSecurityDescriptor);
// Check the private namespace creation result
DWORD dwLastError = GetLastError();
if (g_hNamespace == NULL)
// Nothing to do if access is denied
// --> this code must run under a Local Administrator account
if (dwLastError == ERROR_ACCESS_DENIED)
AddText(TEXT("Access denied when creating the namespace.\r\n"));
AddText(TEXT(" You must be running as Administrator.\r\n\r\n"));
return;
}
else
{
if (dwLastError == ERROR_ALREADY_EXISTS)
// If another instance has already created the namespace,
// we need to open it instead.
AddText(TEXT("CreatePrivateNamespace failed: %u\r\n"), dwLastError);
g_hNamespace = OpenPrivateNamespace(g_hBoundary, g_szNamespace);
if (g_hNamespace == NULL)
AddText(TEXT(" and OpenPrivateNamespace failed: %u\r\n"),
dwLastError);
return;
}
else
g_bNamespaceOpened = TRUE;
AddText(TEXT(" but OpenPrivateNamespace succeeded\r\n\r\n"));
}
}
else
AddText(TEXT("Unexpected error occured: %u\r\n\r\n"),dwLastError);
return;
}
// Try to create the mutex object with a name
// based on the private namespace
TCHAR szMutexName[64];
StringCchPrintf(szMutexName, _countof(szMutexName), TEXT("%s\\%s"), g_szNamespace, TEXT("Singleton"));
g_hSingleton = CreateMutex(NULL, FALSE, szMutexName);//建立互斥量
if (GetLastError() == ERROR_ALREADY_EXISTS)
// There is already an instance of this Singleton object
AddText(TEXT("Another instance of Singleton is running:\r\n"));
AddText(TEXT("--> Impossible to access application features.\r\n"));
else
// First time the Singleton object is created
AddText(TEXT("First instance of Singleton:\r\n"));
AddText(TEXT("--> Access application features now.\r\n"));
}
void AddText(PCTSTR pszFormat,
)
va_list argList;
va_start(argList, pszFormat);
TCHAR sz[20 * 1024];
Edit_GetText(DETAILS_CTRL, sz, _countof(sz));
_vstprintf_s(
_tcschr(sz, TEXT('\0')), _countof(sz) - _tcslen(sz),
pszFormat, argList);
Edit_SetText(DETAILS_CTRL, sz);
va_end(argList);