Messages in this thread | | | Date | Mon, 26 Sep 2022 20:23:57 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] random: split initialization into early arch step and later non-arch step |
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On Mon, Sep 26, 2022 at 08:52:39PM +0200, Jason A. Donenfeld wrote: > On Mon, Sep 26, 2022 at 8:22 PM Kees Cook <keescook@chromium.org> wrote: > > Can find a way to get efi_get_random_bytes() in here too? (As a separate > > patch.) I don't see where that actually happens anywhere currently, > > and we should have it available at this point in the boot, yes? > > No, absolutely not. That is not how EFI works. EFI gets its seed to > random.c much earlier by way of add_bootloader_randomness().
Ah! Okay, so, yes, it _does_ get entropy in there, just via a path I didn't see?
> > > > - entropy[0] = random_get_entropy(); > > > - _mix_pool_bytes(entropy, sizeof(*entropy)); > > > arch_bits -= sizeof(*entropy) * 8; > > > ++i; > > > } > > > - _mix_pool_bytes(&now, sizeof(now)); > > > - _mix_pool_bytes(utsname(), sizeof(*(utsname()))); > > > > Hm, can't we keep utsname in the early half by using init_utsname() ? > > Yes, we could maybe *change* to using init_utsname if we wanted. That > seems kind of different though. So I'd prefer that to be a different > patch, which would require looking at the interaction with early > hostname setting and such. If you want to do that work, I'd certainly > welcome the patch.
Er, isn't that _WAY_ later? Like, hostname isn't set until sysctls up and running, etc. I haven't actually verified 100% but it looks like current->utsname is exactly init_utsname currently.
But if not, I guess it could just get added in both places. I'd be nice to keep kernel version as part of the pre-time-keeping entropy stuffing.
> > Was there a reason kfence_init() was happening before time_init()? > > Historically there was, I think, because random_init() used to make > weird allocations. But that's been gone for a while. At this point > it's a mistake, and removing it allows me to do this: > > https://groups.google.com/g/kasan-dev/c/jhExcSv_Pj4
Cool. Is that true for all the -stable releases this is aimed at?
Anyway, just to repeat before: yay! I really like seeing this split up. :)
-- Kees Cook
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