Date: Mon, 23 Oct 2017 20:00:53 -0400 From: Eric McCorkle <eric@metricspace.net> To: "Simon J. Gerraty" <sjg@juniper.net> Cc: Ian Lepore <ian@freebsd.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, freebsd-security@freebsd.org, freebsd-arch@freebsd.org Subject: Re: Trust system write-up Message-ID: <d06c911a-9e2a-901f-b2bb-4fa2c26b2d59@metricspace.net> In-Reply-To: <72903.1508799185@kaos.jnpr.net> References: <1a9bbbf6-d975-0e77-b199-eb1ec0486c8a@metricspace.net> <1508775285.34364.2.camel@freebsd.org> <e4fb486c-fe8a-571e-8c95-f5f68c44b77c@metricspace.net> <72903.1508799185@kaos.jnpr.net>
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On 10/23/2017 18:53, Simon J. Gerraty wrote: > Eric McCorkle <eric@metricspace.net> wrote: >>> Any thoughts on how to validate executables which are not elf binaries, >>> such as shell scripts, python programs, etc? >> >> I hadn't really thought in depth about it, as my main initial goal is >> signed kernel/modules, but I have given it some thought... >> > >> An alternative is something like the NetBSD veriexec framework, where > > Yes, as previously mentioned the verified exec model deals with this > neatly, and btw is more efficient than signing individual files - as is > needed with ELF signing etc. I think for linux based platforms using IMA we > need to generate 20-30k+ signatures, vs about a dozen for platforms using > verified exec, verification is also more expensive I'm told. Hmmm. There's advantages both ways, and I'll probably end up supporting both, as it's useful to have an in-band mechanism as well (also, I've already implemented signed ELFs). However, there is a definite advantage to having one signature for a huge number of MACs. Moreover, as I mention in the paper, the most feasible quantum-safe signature scheme at the present is SPHINCS, which has signatures about 40Kib in size. That's pretty terrible if you're signing each executable, but if you're signing 20-30k MACs at 16-32 bytes per code plus a path, suddenly a 40Kib signature doesn't look so bad anymore. It would be pretty great to roll out a trust infrastructure AND viable quantum-safe signatures. I could also see a combined scheme, say, where ELF files carry a UUID which indexes into a MAC manifest.
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