Date: Mon, 19 Aug 2013 01:09:24 -0600 From: Warner Losh <imp@bsdimp.com> To: Tim Kientzle <tim@kientzle.com> Cc: =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>, secteam@freebsd.org, Mark R V Murray <mark@grondar.org>, FreeBSD-arch Arch <freebsd-arch@freebsd.org> Subject: Re: random(4) plugin infrastructure for mulitple RNG in a modular fashion Message-ID: <12B58C72-CFE3-4AD4-AD03-462A10E431D9@bsdimp.com> In-Reply-To: <4C1BD77C-8C6B-4044-9285-5978A3BC4B70@kientzle.com> 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>
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On Aug 18, 2013, at 10:53 AM, Tim Kientzle wrote: > On Aug 18, 2013, at 4:33 AM, Dag-Erling Sm=F8rgrav wrote: >=20 >> Mark R V Murray <mark@grondar.org> writes: >>> OK - in the context of what is currently there, it makes less sense = than >>> that; loading RDRAND/Ivy and Nehemiah simultaneously is silly =85 >=20 > Lots of folks build static kernels that they run on diverse > hardware. >=20 > The hardware RNG modules should be loadable simultaneously > and should probe and activate only if their hardware is present, > like any other driver for real hardware. Agreed, I made that point earlier in this thread... >> Provided the HWRNG is of sufficient quality, the user should be = allowed >> to use it directly (through /dev/random) without Yarrow / Fortuna. >=20 > We could have kernel options to choose mixers > (e.g., Yarrow or Fortuna) for /dev/random and > loadable device modules for entropy sources. >=20 > Besides Yarrow and Fortuna mixers, we could then > offer a "null mixer" option that selected the single > "best" entropy source and passed it directly through. I'm still wondering why timecounters aren't the right model to follow = here, where you can have several compiled into the kernel and the one = with the best score wins. > Users could compile the null mixer into the kernel > and load a single HW RNG driver to have precise > control over /dev/random. Interrupt harvesting would > be the lowest-quality source as a fall back. >=20 > In particular, this has a reasonable failure mode if > someone built a kernel with only a single HW entropy > source and the null mixer: > * On hardware with that source, they would get > full-speed HW entropy. > * On hardware without that source, they would get > the old blocking /dev/random that we had before > Yarrow, the one that used only interrupt harvesting. Assuming there was enough interrupt entropy to generate bits... Warner
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