Re: [PATCH 0/2] prandom_u32: make output less predictable

Sedat Dilek
2020-09-01T14:43:04Z

On Tue, Sep 1, 2020 at 8:43 AM Willy Tarreau <w@1wt.eu> wrote:
>
> This is the cleanup of the latest series of prandom_u32 experimentations
> consisting in using SipHash instead of Tausworthe to produce the randoms
> used by the network stack. The changes to the files were kept minimal,
> and the controversial commit that used to take noise from the fast_pool
> (f227e3ec3b5c) was reverted. Instead, a dedicated "net_rand_noise" per_cpu
> variable is fed from various sources of activities (networking, scheduling)
> to perturb the SipHash state using fast, non-trivially predictable data,
> instead of keeping it fully deterministic. The goal is essentially to make
> any occasional memory leakage or brute-force attempt useless.
>
> The resulting code was verified to be very slightly faster on x86_64 than
> what is was with the controversial commit above, though this remains barely
> above measurement noise. It was only build-tested on arm & arm64.
>
> George Spelvin (1):
> random32: make prandom_u32() output unpredictable
>
> Willy Tarreau (1):
> random32: add noise from network and scheduling activity
>
> drivers/char/random.c | 1 -
> include/linux/prandom.h | 55 ++++-
> kernel/time/timer.c | 9 +-
> lib/random32.c | 438 ++++++++++++++++++++++++----------------
> net/core/dev.c | 4 +
> 5 files changed, 326 insertions(+), 181 deletions(-)
>
> 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>
> Cc: Sedat Dilek <sedat.dilek@gmail.com>
>

I have tested with the patchset from [1].
( Later I saw, you dropped "WIP: tcp: reuse incoming skb hash in
tcp_conn_request()". )

- Sedat -

https://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/prandom.git/log/?h=20200901-siphash-noise

> --
> 2.28.0