linux-kernel - Re: get_random_bytes returns bad randomness before seeding is complete

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Message-ID: <CAH8yC8m1HRNWTE9=NXkUypMupAoMTCfs2L=EEfwtXpBgT5BrZg@mail.gmail.com>
Date:   Sat, 3 Jun 2017 18:54:39 -0400
From:   Jeffrey Walton <noloader@...il.com>
To:     Sandy Harris <sandyinchina@...il.com>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Stephan Mueller <smueller@...onox.de>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: get_random_bytes returns bad randomness before seeding is complete

On Sat, Jun 3, 2017 at 5:45 PM, Sandy Harris <sandyinchina@...il.com> wrote:
> ...
> Of course this will fail on systems with no high-res timer. Are there
> still some of those? It might be done in about 1000 times as long on a
> system that lacks the realtime library's nanosecond timer but has the
> Posix standard microsecond timer, implying a delay time in the
> milliseconds. Would that be acceptable in those cases?

A significant portion of the use cases should include mobile devices.
Device sales outnumbered desktop and server sales several years ago.

Many devices are sensor rich. Even the low-end ones come with
accelorometers for gaming. A typical one has 3 or 4 sensors, and
higher-end ones have 7 or 8 sensors. An Evo 4G has 7 of them.

There's no wanting for entropy in many of the use cases. The thing
that is lacking seems to be taking advantage of it.

Jeff