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From: Daniel Borkmann <daniel@iogearbox.net>
To: Kees Cook <keescook@google.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Reshetova, Elena" <elena.reshetova@intel.com>,
	Alexei Starovoitov <ast@kernel.org>
Subject: Re: BPF RNG
Date: Tue, 16 Apr 2019 16:44:40 +0200	[thread overview]
Message-ID: <40a6486d-2dba-5574-06da-3e0ebb25f2b1@iogearbox.net> (raw)
In-Reply-To: <CAGXu5j+Ny=1YF0BkATbU3Xb-fb=_0a1W-iZ3jYFhTcWrTPqCJQ@mail.gmail.com>

On 04/16/2019 03:55 PM, Kees Cook wrote:
> [correcting Alexei's email address and resending...]
> 
> On Tue, Apr 16, 2019 at 8:54 AM Kees Cook <keescook@google.com> wrote:
>>
>> Hi,
>>
>> In looking at prandom_u32() users, I noticed that BPF uses its own
>> state variable with bpf_user_rnd_u32(). It appears that this state is

Correct, we split that off from the main one.

>> never reseeded like regular prandom_u32(). (See __prandom_timer().) Is
>> this intentional, or should reseeding be happening?

The prng is not to be used in any security-critical context. That said,
we optionally could perform reseeding from time to time, though that
should probably be done generically, so that all "external"
prandom_u32_state() users could register themselves upon init whether
they opt-in for periodic reseeding or not.

Thanks,
Daniel

  reply	other threads:[~2019-04-16 15:13 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-16 13:54 Kees Cook
2019-04-16 13:55 ` Kees Cook
2019-04-16 14:44   ` Daniel Borkmann [this message]
2019-04-16 22:58     ` Kees Cook
2019-04-16 15:06   ` Theodore Ts'o

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