Re: memset() in crypto code?

[Daniel Borkmann <dborkman@redhat.com>]

On 10/06/2014 08:52 PM, Sandy Harris wrote:
> On Mon, Oct 6, 2014 at 1:44 PM, Jason Cooper <jason@lakedaemon.net> wrote:
>> On Sat, Oct 04, 2014 at 11:09:40PM -0400, Sandy Harris wrote:
...
>>> There was recently a patch to the random driver to replace memset()
>>> because, according to the submitter, gcc sometimes optimises memset()
>>> away ...
>
>> memzero_explicit() is a good start, ...
>
> As I see it, memzero_explicit() is a rather ugly kluge, albeit an
> acceptable one in the circumstances.

Right.

> A real fix would make memset() do the right thing reliably; if the
> programmer puts in memset( x, 0, nbytes) then the memory should be
> cleared, no ifs or buts. I do not know or care if that means changes
> in the compiler or in the library code or even both, but the fix
> should make the standard library code work right, not require adding a
> new function and expecting everyone to use it.

That would be a desirable goal, ideally perhaps as a built-in from
the compiler itself, just as memset(). Applications such as openssh
implement for the very same purpose their bzero_explicit() variant
just as well.