Precautions When Passing Security Attributes

• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.1 and 3.5
  

SUMMARY

All Win32 APIs that allow security to be specified take a parameter of type LPSECURITY_ATTRIBUTES as the means to attach the security descriptor. However, it is a common error to pass a PSECURITY_DESCRIPTOR type to such functions instead. Because PSECURITY_DESCRIPTOR is of type LPVOID (for opaque data-type reasons), by C Language definition, it is implicitly converted to the correct type. Therefore, the compiler does not generate any warnings; however, unexpected run-time errors will result.

MORE INFORMATION

Below is a correct example of creating a named pipe with a security descriptor attached.

Sample Code

   saSecurityAttributes.nLength = sizeof(SECURITY_ATTRIBUTES);
   saSecurityAttributes.lpSecurityDescriptor = psdAbsoluteSD;
   saSecurityAttributes.bInheritHandle = FALSE;

   hPipe = CreateNamedPipe(TEST_PIPE_NAME,
                           PIPE_ACCESS_DUPLEX,

   (PIPE_TYPE_BYTE|PIPE_READMODE_BYTE|PIPE_WAIT),
                           100,  // maximum instances
                           0,    // output buffer, sized as needed
                           0,    // input buffer, sized as needed
                           100,  // timeout in milliseconds

   (LPSECURITY_ATTRIBUTES)&saSecurityAttributes);
   if( INVALID_HANDLE_VALUE == hPipe )
   { // handle error
   }