linux-kernel - [PATCH-v3 0/5] random: replace urandom pool with a CRNG

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Date:	Mon, 30 May 2016 01:39:20 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Linux Kernel Developers List <linux-kernel@...r.kernel.org>
Cc:	smueller@...onox.de, herbert@...dor.apana.org.au,
	andi@...stfloor.org, sandyinchina@...il.com,
	cryptography@...edaemon.net, jsd@...n.com, hpa@...or.com,
	linux-crypto@...r.kernel.org, Theodore Ts'o <tytso@....edu>
Subject: [PATCH-v3 0/5] random: replace urandom pool with a CRNG

By using a CRNG to replace the urandom pool, we address a number of
complaints which Stephan Mueller has been concerned about.  We now use
a much more aggressive interrupt sampling system to quickly initialize
a CRNG which gets used in place of the original non-blocking pool.
This tends to get initialized *very* quickly (before the devices are
finished being proved.)  Like Stephan's proposal, this assumes that we
can get a bit of entropy per interrupt, which may be problematic on
some architectures.  So after we do this quick-and-dirty
initialization, we then fall back to the slower, more conservative
interrupt sampling system to fill the input pool, and we will do a
catastrophic reseeding once we get 128 bits using the slower but more
conservative system, and every five minutes afterwards, if possible.

In addition, on NUMA systems we make the CRNG state per-NUMA socket, to
address the NUMA locking contention problem which Andi Kleen has been
complaining about.  I'm not entirely sure this will work well on the
crazy big SGI systems, but they are rare.  Whether they are rarer than
abusive userspace programs that are continuously pounding /dev/urandom
is unclear.  If necessary we can make a config option to turn off the
per-NUMA socket hack if it proves to be problematic.

Note: I didn't propose this for merging in 4.7 because I wanted to
   further refine the reseeding logic and because I wanted to get more
   feedback.  My plan is to merge these changes for the 4.8 merge
   window.

These patches are also available at:
	git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random.git

Changes since -v2:
  * Rebased to v4.7-rc1
  * Improved/reworked CRNG reseeding and backtracking protection
  * Preseed the CRNG state from system data
  * Added fix to properly align the get_random_int_hash[] array

Eric Biggers (1):
  random: properly align get_random_int_hash

Stephan Mueller (1):
  random: add interrupt callback to VMBus IRQ handler

Theodore Ts'o (3):
  random: replace non-blocking pool with a Chacha20-based CRNG
  random: make /dev/urandom scalable for silly userspace programs
  random: add backtracking protection to the CRNG

 crypto/chacha20_generic.c |  61 -------
 drivers/char/random.c     | 446 ++++++++++++++++++++++++++++++++++++----------
 drivers/hv/vmbus_drv.c    |   3 +
 include/crypto/chacha20.h |   1 +
 lib/Makefile              |   2 +-
 lib/chacha20.c            |  79 ++++++++
 6 files changed, 438 insertions(+), 154 deletions(-)
 create mode 100644 lib/chacha20.c

-- 
2.5.0