On Thu, Aug 30, 2012 at 07:03:43PM +0000, Taylor R Campbell wrote:
>
> The issue with memset isn't timing attacks, but rather that the C
> compiler is likely to optimize away the apparently useless memset from
> code that looks like this, and thereby leave keys floating about in
> RAM:
>
> {
> char key[32];
>
> fetch_key(key);
> do_sekrit_stuff_with_key(key);
> memset(key, 0, sizeof key);
> }
>
> Hence explicit_{bzero,memset}, not consttime_{bzero,memset}, which are
> supposed to be guaranteed not to be optimized away.
Which means that it shpuld be enough to add (with gcc):
asm volatile ("" ::: "memory");
after the memset().
David
--
David Laight: da...@l8s.co.uk
