Re: [gentoo-user] memset_s

[Jorge Almeida <jjalmeida@gmail.com>]

On Sun, Nov 12, 2017 at 7:03 PM, Mart Raudsepp <leio@gentoo.org> wrote:
> On L, 2017-11-11 at 00:10 +0000, Jorge Almeida wrote:
>> Well, most programmers probably won't care about this stuff anyway,
>> and people who deal with cryptography tend to be more cautious than
>> average. But I'm not really making a case for safe versions of known
>> functions. After all, the usual functions do fine for most
>> applications. memset() would be enough to clear RAM with sensitive
>> data if we had a pragma (or equivalent) to convince the compiler to
>> not ignore it (I mean a pragma to invoke on a particular function
>> definition when the programmer  feels that a black box behaviour is
>> undesirable). Of course, solving the problem of the compiler copying
>> stuff around might be harder nut to crack.
>
> Sounds like you want explicit_bzero from libbsd?
>
According to their man page, yes. I'll have to [try to] check the
source. I wonder how they do it? Even the volatile modifier doesn't
solve the problem, according to the link in previous post.

Anyway, there are probably circumstances where not optimizing a
particular function would be useful. Zeroing sensitive data is just
the first that comes to mind. (For example, what if you prefer
overwriting your sensitive data with random bytes?)

Jorge