linux/include
Willy Tarreau 3744741ada random32: add noise from network and scheduling activity
With the removal of the interrupt perturbations in previous random32
change (random32: make prandom_u32() output unpredictable), the PRNG
has become 100% deterministic again. While SipHash is expected to be
way more robust against brute force than the previous Tausworthe LFSR,
there's still the risk that whoever has even one temporary access to
the PRNG's internal state is able to predict all subsequent draws till
the next reseed (roughly every minute). This may happen through a side
channel attack or any data leak.

This patch restores the spirit of commit f227e3ec3b ("random32: update
the net random state on interrupt and activity") in that it will perturb
the internal PRNG's statee using externally collected noise, except that
it will not pick that noise from the random pool's bits nor upon
interrupt, but will rather combine a few elements along the Tx path
that are collectively hard to predict, such as dev, skb and txq
pointers, packet length and jiffies values. These ones are combined
using a single round of SipHash into a single long variable that is
mixed with the net_rand_state upon each invocation.

The operation was inlined because it produces very small and efficient
code, typically 3 xor, 2 add and 2 rol. The performance was measured
to be the same (even very slightly better) than before the switch to
SipHash; on a 6-core 12-thread Core i7-8700k equipped with a 40G NIC
(i40e), the connection rate dropped from 556k/s to 555k/s while the
SYN cookie rate grew from 5.38 Mpps to 5.45 Mpps.

Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
Cc: George Spelvin <lkml@sdf.org>
Cc: Amit Klein <aksecurity@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
2020-10-24 20:21:57 +02:00
..
acpi pci-v5.10-changes 2020-10-22 12:41:00 -07:00
asm-generic Kbuild updates for v5.10 2020-10-22 13:13:57 -07:00
clocksource clocksource/drivers/sp804: Remove unused sp804_timer_disable() and timer-sp804.h 2020-09-24 10:51:04 +02:00
crypto X.509: Fix modular build of public_key_sm2 2020-10-08 16:39:14 +11:00
drm sound updates for 5.10 2020-10-15 11:07:44 -07:00
dt-bindings This pull request contains zero diff to the core framework. It is a collection 2020-10-22 12:53:28 -07:00
keys
kunit linux-kselftest-kunit-5.10-rc1 2020-10-18 14:45:59 -07:00
kvm ARM: 2020-10-23 11:17:56 -07:00
linux random32: add noise from network and scheduling activity 2020-10-24 20:21:57 +02:00
math-emu
media Linux 5.9-rc7 2020-10-04 12:19:12 +02:00
memory
misc
net Fixes for 5.10-rc1 from the networking tree: 2020-10-23 12:05:49 -07:00
pcmcia
ras mm,hwpoison: introduce MF_MSG_UNSPLIT_THP 2020-10-16 11:11:17 -07:00
rdma RDMA: Explicitly pass in the dma_device to ib_register_device 2020-10-16 13:53:46 -03:00
scsi SCSI misc on 20201023 2020-10-23 16:19:02 -07:00
soc networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
sound ASoC: Updates for v5.10 2020-10-12 16:08:57 +02:00
target
trace ARM: 2020-10-23 11:17:56 -07:00
uapi Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2020-10-23 16:16:31 -07:00
vdso
video fbdev: remove mbx framebuffer driver 2020-09-08 13:33:32 +02:00
xen xen: branch for v5.10-rc1b 2020-10-20 09:24:01 -07:00