[110643] in cryptography@c2.net mail archive
Re: More on in-memory zeroisation
daemon@ATHENA.MIT.EDU (Thierry Moreau)
Thu Dec 13 14:06:11 2007
Date: Wed, 12 Dec 2007 17:27:38 -0500
From: Thierry Moreau <thierry.moreau@connotech.com>
To: "Leichter, Jerry" <leichter_jerrold@emc.com>
CC: Peter Gutmann <pgut001@cs.auckland.ac.nz>, cryptography@metzdowd.com
In-Reply-To: <Pine.SOL.4.61.0712121640150.646@mental>
Leichter, Jerry wrote:
>
> On Wed, 12 Dec 2007, Thierry Moreau wrote:
>
> | Date: Wed, 12 Dec 2007 16:24:43 -0500
> | From: Thierry Moreau <thierry.moreau@connotech.com>
> | To: "Leichter, Jerry" <leichter_jerrold@emc.com>
> | Cc: Peter Gutmann <pgut001@cs.auckland.ac.nz>, cryptography@metzdowd.com
> | Subject: Re: More on in-memory zeroisation
> |
> | /************ testf.c ************/
> | #include <stdio.h>
> | #include <string.h>
> |
> | typedef void *(*fpt_t)(void *, int, size_t);
> |
> | void f(fpt_t arg)
> | {
> | if (memset==arg)
> | printf("Hello world!\n");
> | }
> |
> | /************ test.c ************/
> | #include <stdlib.h>
> | #include <string.h>
> |
> | typedef void *(*fpt_t)(void *, int, size_t);
> |
> | extern void f(fpt_t arg);
> |
> | int main(int argc, char *argv[])
> | {
> | f(memset);
> | return EXIT_SUCCESS;
> | }
> |
> | /* I don't want to argue too theoretically.
> |
> | - Thierry Moreau */
> I'm not sure what you are trying to prove here. Yes, I believe that
> in most implementations, this will print "Hello world\n". Is it,
> however, a strictly conforming program (I think that's the right
> standardese) - i.e., are the results guaranteed to be the same on
> all conforming implementations? I think you'll find it difficult
> to prove that.
If there is a consensus among comforming implementation developers that
the above program is comforming, that's a good enough "proof" for me.
As a consequence of alleged consensus above, my understanding of the C
standard would prevail and (memset)(?,0,?) would refer to an external
linkage function, which would guarantee (to the sterngth of the above
consensus) resetting an arbitrary memory area for secret intermediate
result protection.
Reading ANSI X3.159-1989, I believe there would be such a consensus, and
I find it quite obvious. You may disagree, and I will no further argument.
Regards,
--
- Thierry Moreau
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