linux-kernel - Re: [PATCH -v5] random: introduce getrandom(2) system call

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

Message-ID: <CALCETrXtNUSCQEZ+SKJ5Br41rnF35kGqStkFuX6dN-3z5hVdmQ@mail.gmail.com>
Date:	Thu, 24 Jul 2014 13:54:05 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	linux-crypto@...r.kernel.org
Subject: Re: [PATCH -v5] random: introduce getrandom(2) system call

On Thu, Jul 24, 2014 at 1:30 PM, Henrique de Moraes Holschuh
<hmh@....eng.br> wrote:
> On Thu, 24 Jul 2014, Theodore Ts'o wrote:
>> On Thu, Jul 24, 2014 at 08:21:38AM -0700, Andy Lutomirski wrote:
>> > > Should we add E<SOMETHING> to be able to deny access to GRND_RANDOM or some
>> > > future extension ?
>> >
>> > This might actually be needed sooner rather than later.  There are
>> > programs that use containers and intentionally don't pass /dev/random
>> > through into the container.  I know that Sandstorm does this, and I
>> > wouldn't be surprised if other things (Docker?) do the same thing.
>>
>> I wouldn't add the error to the man page until we actually modify the
>> kernel to add such a restriction.
>
> By then, it might be too late.  It would be really sad to find ourselves
> forced to return ENOSYS to getrandom(GRND_RANDOM) when we actually wanted to
> return EPERM/EACCES.
>
> Actually, we might not be able to do even that much: all it takes is for
> someone to have the bright idea of deploying userspace code that checks for
> ENOSYS only on a first "probe" getrandom() syscall without GRND_RANDOM, and
> does something idiotic when it gets ENOSYS later on a
> getrandom(GRND_RANDOM).  meh.  We can't even abuse the system ourselves :-)
>

Or that someone writes userspace code that gets -EPERM/-EACCESS on
getrandom with GRND_RANDOM and falls back to something worse than
getrandom w/o GRND_RANDOM.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/