Date: Mon, 19 Aug 2013 01:18:22 -0600 From: Warner Losh <imp@bsdimp.com> To: Mark R V Murray <mark@grondar.org> Cc: Tim Kientzle <tim@kientzle.com>, FreeBSD-arch Arch <freebsd-arch@freebsd.org>, secteam@freebsd.org, =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no> Subject: Re: random(4) plugin infrastructure for mulitple RNG in a modular fashion Message-ID: <71A92486-2213-421E-B3D2-E55816C18924@bsdimp.com> In-Reply-To: <F908BF80-538B-4363-ACCC-3D860CBEE359@grondar.org> References: <20130807183112.GA79319@dragon.NUXI.org> <86pptfnu33.fsf@nine.des.no> <20130815231713.GD76666@x96.org> <20130816002625.GE76666@x96.org> <9B274F48-0C88-4117-BEAC-1A555772A3C5@grondar.org> <86a9kf733d.fsf@nine.des.no> <0C97B866-A169-4141-8368-AA7F5B5382F4@grondar.org> <861u5r71zi.fsf@nine.des.no> <892B11BD-396D-4F82-B97C-753F72CA494D@grondar.org> <86r4dr5j3p.fsf@nine.des.no> <4C1BD77C-8C6B-4044-9285-5978A3BC4B70@kientzle.com> <537622E1-F785-4BFA-B829-09DCDB484606@grondar.org> <932AB5CA-778E-438D-8FD3-8C0F29F3D117@kientzle.com> <F908BF80-538B-4363-ACCC-3D860CBEE359@grondar.org>
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On Aug 18, 2013, at 2:02 PM, Mark R V Murray wrote: > On 18 Aug 2013, at 20:27, Tim Kientzle <tim@kientzle.com> wrote: >> But clearly some people really want to be able to >> force /dev/random to be the unconditioned output >> of a particular HW RNG. I don't know if this is a >> good idea or not, but clearly there are people who >> want this. >=20 > Agreed. (This includes my change of position on the > subject.) >=20 > Others want Yarrow/Fortuna no matter what. If we're going to allow passthrough, we should require the kernel config = to explicitly do something to get pass through. nodevice yarrow device random_passthrough would be my suggestion. >> I am NOT claiming the old blocking /dev/random is >> "good"; just that it is not an entirely unacceptable failure >> mode for badly mismatched kernel/hardware combinations. >> Keep in mind such mismatches may happen accidentally: >> add-on HW RNG cards can fail. >=20 > True. Yarrow and Fortuna were designed to shield against > those very failure modes. They treat ALL entropy sources > as suspect and endeavour to be secure irregardless. >=20 > I propose two-route device: >=20 > Route 1 (SW): > Yarrow/Fortuna (choosable between the two for now), > and a fallback for Route 2. It should be possible to > build a kernel without this route. >=20 > Route 2 (HW): > Minimally-processed randomness directly from a dedicated > source, similar to the rdrand/ivy device, but with the > actual source abstracted. If no suitable source is > available, then this whole route fails. This is where > some useful "pluggability" can come. If this fails to > fall back; then perhaps a "I don't care" vs "PANIC!!" > fallback can be supplied. Here lie the dragons. I'd go so far as to say that if you have random in your kernel, then you = need to specify some "filter" or you get a compile-time error. = Specifying yarrow via DEFAULTS or std.foo is fine by me, since both of = those can be overriden fairly easily.... I'd also think we'd want to = FAIL_PANIC or FAIL_BLOCKING, and have that choice hard wired at some = level too, to be explicit about things. But maybe that's gilding things = a bit too much and a tunable would suffice... Warner
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