[Cryptography] Heartbleed and fundamental crypto programming practices

[tpb-crypto at laposte.net]

> Message du 15/04/14 22:44
> De : "danimoth" 
> A : "Crypto List" 
> Copie à : 
> Objet : Re: [Cryptography] Heartbleed and fundamental crypto programming practices
>

> On 10/04/14 at 03:49pm, Bear wrote:
> > "Doesn't affect program output: therefore is a waste of work" 
> > is the underlying assumption, correct for most software, which 
> > is utterly, utterly wrong for crypto.
> > 
> > In C and C++, variable locations are stable (and mostly have to 
> > be because those languages use explicit pointers) but you have 
> > to declare them 'volatile' to be absolutely sure that the compiler 
> > will never move them (without zeroing the old location) and that 
> > writes to them prior to deallocation will happen as the code 
> > commands. 
> > 
> > In most languages, there is absolutely no standard way to be sure 
> > of getting an optimizing compiler to leave final writes alone.
> [cut]
> 
> If I understood correctly, all crypto software should be compiled with 
> -O0 flag... 

Well, depends on what kind of attack you want to avoid, you may use -O3 if you want to reduce the chances against the recent attack on OpenSSL's ECDSA in some Intel chips' cache.