Date: Wed, 8 Aug 2001 16:56:39 -0700 From: Kris Kennaway <kris@obsecurity.org> To: John Jennings <my_pinup_girl@www.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: uptime values in kernel Message-ID: <20010808165638.A91680@xor.obsecurity.org> In-Reply-To: <200108082246.PAA01726@mail19.bigmailbox.com>; from my_pinup_girl@www.com on Wed, Aug 08, 2001 at 03:46:48PM -0700 References: <200108082246.PAA01726@mail19.bigmailbox.com>
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--mP3DRpeJDSE+ciuQ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Aug 08, 2001 at 03:46:48PM -0700, John Jennings wrote: > Hello all: >=20 > As stated on this page: >=20 > http://uptime.netcraft.com/up/accuracy.html#whichos >=20 > FreeBSD 3.0 and later 'default configuration' does not supply > accurate uptime statistics to Netcraft so that they may plot a > graph. What is meant by 'default configuration'? I got a few > pointers on DALnet #freebsd. They said that I am attempting to > 'change the kernel so that it displays the correct uptime.' > > I do believe this is a matter of little importance; but, for > knowledge sake, I would like some information on how to reach my > desired goal. Does it involve compiling a new kernel or simply > changing an obscure configuration file? The current implementation of RFC 1323 TCP extensions leaks the system uptime to remote systems. RFC 1323 was disabled in 3.0 because it causes certain ancient (really ancient) hardware to break, but it's recently been re-enabled because a number of other OSes didn't bother about breaking that hardware, and so it's basically safe now. You can enable it in /etc/rc.conf by setting tcp_extensions=3D"YES". Note that leaking of system uptime has indirect security implications: there have been a number of attacks in the past which rely on, or are made much easier by, a precise knowledge of the system uptime. Kris --mP3DRpeJDSE+ciuQ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: For info see http://www.gnupg.org iD8DBQE7cdG1Wry0BWjoQKURAnWzAJsFUdmpHYeRXbuY/t5rpLtzqb1d5gCfRyIS MFYsQ4QFFppqaVrTWg592Mk= =lgSM -----END PGP SIGNATURE----- --mP3DRpeJDSE+ciuQ-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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