linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	"Ahmed S. Darwish" <darwish.07@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Nicholas Mc Guire <hofrat@opentech.at>,
	the arch/x86 maintainers <x86@kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>
Subject: Re: x86/random: Speculation to the rescue
Date: Sun, 29 Sep 2019 23:37:06 -0400	[thread overview]
Message-ID: <20190930033706.GD4994@mit.edu> (raw)
In-Reply-To: <CAHk-=wi0vxLmwEBn2Xgu7hZ0U8z2kN4sgCax+57ZJMVo3huDaQ@mail.gmail.com>

On Sun, Sep 29, 2019 at 06:16:33PM -0700, Linus Torvalds wrote:
> 
>  - or just say "hey, a lot of people find jitter entropy reasonable,
> so let's just try this".
> 

I'm OK with this as a starting point.  If a jitter entropy system
allow us to get pass this logjam, let's do it.  At least for the x86
architecture, it will be security through obscurity.  And if the
alternative is potentially failing where the adversary can attack the
CRNG, it's my preference.  It's certainly better than nothing.

That being said, I'd very much like to see someone do an analysis of
how well these jitter schemes work on an RISC-V iplementation (you
know, the ones that were so simplistic and didn't have any speculation
so they weren't vulnerable to Specture/Meltdown).  If jitter
approaches turn out not to work that well on RISC-V, perhaps that will
be a goad for future RISC-V chips to include the crypto extension to
their ISA.

In the long term (not in time for the 5.4 merge window), I'm convinced
that we should be trying as many ways of getting entropy as possible.
If we're using UEFI, we should be trying to get it from UEFI's secure
random number generator; if there is a TPM, we should be trying to get
random numbers from the RPM, and mix them in, and so on.

After all, the reason why lived with getrandom(0) blocking for five
years was because for the vast majority of x86 platforms, it simply
wasn't problem in practice.  We need to get back to that place where
in practice, we've harvested as much uncertainty from hardware as
possible, so most folks are comfortable that attacking the CRNG is no
longer the simplest way to crack system security.

       	     	     	      	     - Ted

  parent reply	other threads:[~2019-09-30  3:37 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-28 22:24 x86/random: Speculation to the rescue Thomas Gleixner
2019-09-28 23:53 ` Linus Torvalds
2019-09-29  7:40   ` Thomas Gleixner
2019-09-29  8:05   ` Alexander E. Patrakov
2019-09-30  1:16   ` Linus Torvalds
2019-09-30  2:59     ` Linus Torvalds
2019-09-30  6:10       ` Borislav Petkov
2019-09-30 16:06         ` Linus Torvalds
2019-10-01 13:51           ` Borislav Petkov
2019-10-01 17:14             ` Linus Torvalds
2019-10-01 17:50               ` [PATCH] char/random: Add a newline at the end of the file Borislav Petkov
2019-09-30 18:05         ` x86/random: Speculation to the rescue Kees Cook
2019-09-30  3:37     ` Theodore Y. Ts'o [this message]
2019-09-30 13:16       ` Theodore Y. Ts'o
2019-09-30 16:15         ` Linus Torvalds
2019-09-30 16:32           ` Peter Zijlstra
2019-09-30 17:03             ` Linus Torvalds
2019-10-01 10:28           ` David Laight
2019-10-15 21:50             ` Thomas Gleixner
2019-10-01 16:15   ` Ahmed S. Darwish
2019-10-01 16:37     ` Kees Cook
2019-10-01 17:18       ` Ahmed S. Darwish
2019-10-01 17:25     ` Linus Torvalds
2019-10-06 12:07       ` Pavel Machek
2019-10-02 12:01     ` Theodore Y. Ts'o
2019-10-06 11:41   ` Pavel Machek
2019-10-06 17:26     ` Linus Torvalds
2019-10-06 17:35       ` Pavel Machek
2019-10-06 18:06         ` Linus Torvalds
2019-10-06 18:21           ` Pavel Machek
2019-10-06 18:26             ` Linus Torvalds
2019-10-07 11:47             ` Theodore Y. Ts'o
2019-10-07 22:18               ` Pavel Machek
2019-10-08 11:33                 ` David Laight
2019-10-09  8:02                   ` Pavel Machek
2019-10-09  9:37                     ` David Laight
2019-10-01  2:14 hgntkwis

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190930033706.GD4994@mit.edu \
    --to=tytso@mit.edu \
    --cc=darwish.07@gmail.com \
    --cc=hofrat@opentech.at \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).