Re: A Famous Security Bug

scott@slp53.sl.home (Scott Lurndal) writes:

Kaz Kylheku <433-929-6894@kylheku.com> writes:

On 2024-03-20, Stefan Ram <ram@zedat.fu-berlin.de> wrote:

  A "famous security bug":
>
void f( void )
{ char buffer[ MAX ];
  /* . . . */
  memset( buffer, 0, sizeof( buffer )); }
>
  . Can you see what the bug is?

>
I don't know about "the bug", but conditions can be identified under
which that would have a problem executing, like MAX being in excess
of available automatic storage.

>
Perhaps Stephan is under the mistaken assumption that
'buffer' devolves to a type of 'char *' when used
with the sizeof operator.

>
That was my first thought, but I think the idea (not clearly stated) is
that the /* . . . */ code stores sensitive information in buffer, and
the memset call is intended to clobber that information, but may be
elided since buffer is not explicitly used later.  A malicious process
with access to the program's memory might be able to read that
information after f() has returned.

C23 adds memset_explicit() for this purpose.