Did you *really* zeroize that key?

[Bill Sommerfeld]

[cc's pruned]

> static void
> burn_stack (int bytes)
> {
>      char buf[64];
> 
>      memset (buf, 0, sizeof buf);
>      bytes -= sizeof buf;
>      if (bytes > 0)
>          burn_stack (bytes);
> }

This may also not quite do what you think:

 1) burn_stack() may reasonably be made tail-recursive by a
sufficiently agressive compiler, if the memset is inlined and is then
recognized as a bunch of dead stores.

 2) even if it doesn't get tail-call treatment, some ABI's require
largeish alignment for stack frames or define a fixed component to the
stack frame and then don't fill in the unused stack slots; either of
these may leave a good size chunk of the stack unwritten.

						- Bill

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