Message-ID: <1363258094.4853.20.camel@i7.infradead.org>
Subject: Re: Wrong system clock vs X.509 date specifiers
From: David Woodhouse <dwmw2@infradead.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Howells <dhowells@redhat.com>, rusty@rustcorp.com.au,
        herbert@gondor.hengli.com.au, pjones@redhat.com, jwboyer@redhat.com,
        linux-crypto@vger.kernel.org, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, keyrings@linux-nfs.org
Date: Thu, 14 Mar 2013 10:48:14 +0000
In-Reply-To: <20120925163037.20ba3f3c@pyramind.ukuu.org.uk>
References: <5555.1348531649@warthog.procyon.org.uk>
	 <21845.1348585794@warthog.procyon.org.uk>
	 <20120925163037.20ba3f3c@pyramind.ukuu.org.uk>
Content-Type: multipart/signed; micalg="sha1"; protocol="application/x-pkcs7-signature";
	boundary="=-fFD9nZ5HmDapRimHSVaE"
Mime-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 11203
Lines: 187


--=-fFD9nZ5HmDapRimHSVaE
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tue, 2012-09-25 at 16:30 +0100, Alan Cox wrote:
> On Tue, 25 Sep 2012 16:09:54 +0100
> David Howells <dhowells@redhat.com> wrote:
>=20
> >=20
> > The X.509 certificate has a pair of times in it that delineate the vali=
d
> > period of the cert, and I'm checking that the system clock is within th=
e
> > bounds they define before permitting you to use the cert.  I've been se=
tting
> > the expiry date to be 100 years in the future - by which time hopefully=
 I
> > won't have to worry about it - but occasionally clock skew means a fres=
hly
> > built kernel won't boot because the machine trying to boot doesn't thin=
k that
> > the start time has been reached yet.
> >=20
> > Do we actually want to do this, however?  Or should we just ignore the =
times?
> > Or just the start time?
>=20
> Generate a certificate that is valid from a few minutes before the
> wallclock time. It's a certificate policy question not a kernel hackery
> one.

That's not good enough. I frequently encounter laptops with hardware
clocks which are *way* slower than that. I see lots of machines booting
up thinking it's 1970, 1900 iirc for some Macs, and more recently 2001.

This causes the kernel to refuse to load the certificate:
[    3.116185] Loading module verification certificates
[    3.117414] X.509: Cert e1a74f2317b1f38848278d07926ed16c2675393e is not =
yet valid
[    3.118639] MODSIGN: Problem loading in-kernel X.509 certificate (-129)

...and then spew error messages every time a module is loaded.=20

For the kernel, it makes *absolutely* no sense to be checking the start
date of the certificate. We do not have a usage model where someone says
"hey, here's this kernel module but I don't want you to be able to use
it until tomorrow so I've post-dated its signature".

If we *ever* try to load a signed kernel module when the certificate is
"not yet valid", it's because the clock is wrong. It's as simple as
that.

And even if we *did* want to support that stupid "load this tomorrow"
use case, it's broken. You couldn't boot today, then load the offending
module tomorrow. You'd have to *reboot* tomorrow, because the kernel
refused to load the damn cert into its store at all.

For the specific case of module signing, we should probably just disable
the date checks completely.

--=20
dwmw2

--=-fFD9nZ5HmDapRimHSVaE
Content-Type: application/x-pkcs7-signature; name="smime.p7s"
Content-Disposition: attachment; filename="smime.p7s"
Content-Transfer-Encoding: base64
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--=-fFD9nZ5HmDapRimHSVaE--

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/