Re: BPF RNG

[Kees Cook]

On Tue, Apr 16, 2019 at 10:13 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx> 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.

Yeah, it seemed like it should be built into the API. I'll add this to
the TODO list. ;)

Thanks for double-checking.

-- 
Kees Cook