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Message-ID: <YV5UDyXNaOKeLz7p@netbsd.org>
Date: Thu, 7 Oct 2021 01:57:35 +0000
From: David Holland <dholland-libc@...bsd.org>
To: libc-coord@...ts.openwall.com
Subject: Re: freezero() and freezeroall()
On Mon, Oct 04, 2021 at 06:22:39PM -0700, Alan Coopersmith wrote:
> On 9/17/21 5:46 PM, Paul Eggert wrote:
> > Looking at the current OpenBSD source code[1], it appears they're doing
> > best effort. Unless I'm missing something, in some cases freezero
> > appears to call memset instead of explicit_bzero. Even if that were
> > changed, on real systems I expect the data are too often still lying
> > around somewhere in the hardware. I suppose the idea is that it's
> > better than nothing.
>
> I believe the goal is to protect against the memory being visible
> in core files and to debuggers, not to a physical RAM dump of some
> sort.
(Probably should have said this a month ago)
I'm not sure I see the point of this function -- if you're calling
explicit_bzero because you're handling secrets, skipping the bzero
because the page is about to be unmapped seems like a mistake, so
explicit_bzero followed by free seems just as good as anything and
easier to reason about than adding something new.
If you're not handling secrets, then it seems like security theater.
--
David A. Holland
dholland@...bsd.org
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