[cfe-dev] Zero'ing Registers on Function Return

[David Chisnall]

Hi Russel,

I didn't realise that Colin had blogged about it.  We've discussed it a few times in the past and I have an implementation of it that we are evaluating.

David

On 12 Sep 2014, at 03:30, Russell Harmon <eatnumber1 at google.com> wrote:

> I've been thinking about the issues with securely zero'ing buffers that Colin Percival discusses in his blog article, and I think I'd like to take a stab at fixing it in clang. Here's my proposal:
> 
> Add a function attribute, say __attribute__((clear_regs_on_return)) which when a thus annotated function returns will zero all callee owned registers and spill slots. Then, all unused caller owned registers will be immediately cleared by the caller after return.
> 
> As for why, I'm concerned with the case where a memory disclosure vulnerability exposes all or a portion of sensitive data via either spilled registers or infrequently used registers (xmm). If an attacker is able to analyze a binary for situations wherein sensitive data will be spilled, leveraging a memory disclosure vulnerability it's likely one could craft an exploit that reveals sensitive data.
> 
> What does the list think?
> -Russ Harmon
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