Re: [boost] [uuid] Issue 9407: please merge fix

Subject: Re: [boost] [uuid] Issue 9407: please merge fix
From: Peter Dimov (lists_at_[hidden])
Date: 2015-01-16 12:04:46

Andrey Semashev wrote:
> On Friday 16 January 2015 18:33:28 Peter Dimov wrote:
> > Antony Polukhin wrote:
> > > Especially I'm interested in applying a pull request to fix 9407
> > > <https://svn.boost.org/trac/boost/ticket/9407> issue (
> > > https://github.com/boostorg/uuid/pull/2).
> >
> > On Windows, the usual procedure is to use RtlGenRandom, but I'm not sure 
> > which approach is better.
>
> I think it's not public API. MSDN recommends using CryptGenRandom instead.

There are no longer any non-public Windows APIs as a result of the antitrust 
lawsuit, but yes, it's probably better to use the supported version.

On a more general note, all this homegrown entropy gathering in that 
function (for most of which I might be responsible, in fact) should just be 
skipped if we have CryptGenRandom or /dev/urandom; it should merely be a 
fallback. We're never going to improve upon CryptGenRandom's output, most we 
could do is not damage it, and /dev/urandom is, I think, also 
reasonably-crypto-quality on today's POSIX OSes.

There's one subtlety though, the fact that we currently proceed 
unconditionally to mixing homegrown entropy allows us to not check for 
errors from CryptGenRandom or fread, and if we're going to skip it, we 
should check.

On an even more general note, this is actually a reimplementation of 
random_device, so it might be worth fixing that to always work (and perhaps 
take advantage of std::random_device if present?).