linux-kernel - Re: [PATCH v2] utsname: contribute changes to RNG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAHmME9ptjydKVKBnYP6BaEnuJVxxzUD9AgmqVsHA1mEMV44cDw@mail.gmail.com>
Date:   Tue, 27 Sep 2022 16:53:56 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH v2] utsname: contribute changes to RNG

On Tue, Sep 27, 2022 at 4:25 PM Kees Cook <keescook@...omium.org>
wrote:> > +             add_device_randomness(tmp_data,
sizeof(tmp_data));
>
> Does this matter that we're dumping the same same trailing bytes into
> the RNG? (i.e. only min(lenp, table->maxlen) has changed.)
>
> If that's okay (and maybe a comment should be added):
>
> Reviewed-by: Kees Cook <keescook@...omium.org>

It doesn't matter. You can call add_device_randomness() as often as
you want on whatever data you want, and it is never bad.

I mentioned in my Linux Plumbers talk that I'd like to see various
subsystems add whatever they can find, provided it's not a performance
bottleneck. add_device_randomness() is good for things that /could/ be
random, but might not be. Right after my talk, somebody posted this,
which I was happy to see:
https://lore.kernel.org/all/20220915004117.1562703-2-bryan.odonoghue@linaro.org/

There's also this commit from a few months ago that I was quite happy
about: https://lore.kernel.org/all/20220425205442.1347837-1-linus.walleij@linaro.org/

This one here is part of that same general trend. If you have more
ideas on odd drivers or hooks or whatever else where that might be
useful, feel free to submit patches.

Jason