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

[Sedat Dilek]

On Tue, Sep 1, 2020 at 8:43 AM Willy Tarreau <w@xxxxxx> 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@xxxxxxx>
> Cc: Amit Klein <aksecurity@xxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: tytso@xxxxxxx
> Cc: Florian Westphal <fw@xxxxxxxxx>
> Cc: Marc Plumb <lkml.mplumb@xxxxxxxxx>
> Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx>
>

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