Re: FreeBSD Patch question
From: Gaspar Chilingarov (nm_at_web.am)
Date: 09/26/03
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Date: Fri, 26 Sep 2003 7:40:18 +0400 To: freebsd-security@freebsd.org
Probably this should included in the FAQ, very good and detailed answer...
--------- Original Message --------
From: Robert Watson <rwatson@freebsd.org>
To: V. Jones <vjones62@earthlink.net>
Cc: freebsd-security@freebsd.org
Subject: Re: FreeBSD Patch question
Date: 26/09/03 00:15
>
>
> On Thu, 25 Sep 2003, V. Jones wrote:
>
> > I administer a remote server and want to apply some of the security
> > patches. (I assume this is the best way to go since I can't go into
> > single-user mode to use CVsup).
>
> I generally follow the following practice:
>
> cvsup in multiuser
> buildworld in multiuser
> buildkernel in multiuser
>
> These stages, other than impact on cpu, memory, disk i/o speed, and
> storage space, shouldn't interact with the running environment and so
> shouldn't be a problem. Then comes the slightly more tricky bit: I decide
> whether I'm willing to update while running multiuser. If I am:
>
> installkernel
> reboot
> installworld
> mergemaster
> reboot
>
> If I'm not, the procedure is much the same except that I boot only to
> single-user after the first reboot, mount -a, swapon, and proceed.
>
> Note that there are a number of risks and complications associated with
> the installworld and mergemaster steps, both in multiuser and singleuser
> mode. multiuser is typically more risky: for example, if mergemaster
> notices a change to MAKEDEV, it will prompt to recreate devices. DO NOT
> DO THIS ON A LIVE MULTIUSER SYSTEM. :-) If you do run it, it will reset
> all the permissions in /dev, leaving in-use ttys world readable and
> writable. This will permit unprivileged users to potentially sniff the
> I/O for more privileged users, send output to their display, etc. So it's
> fine in single-user, but not multi-user. Typically, that sort of change
> doesn't occur on the security/release branches, but will happen with
> moderate frequency as you track -STABLE.
>
> > I have a couple of questions. First, I have installed one of the pgp
> > ports to verify the patches. When I run it, I get this message:
> >
> > > File 'buffer46.patch.asc' has signature, but with no text.
> > > Text is assumed to be in file 'buffer46.patch'.
> > > signature not checked.
> > > Signature made 2003/09/17 18:02 GMT
> > > key does not meet validity threshold.
> >
> > > WARNING: Because this public key is not certified with a
trusted
> > > signature, it is not known with high confidence that this public
key
> > > actually belongs to: "(KeyID: 0xCA6CDFB2)".
> >
> > I guess that I need to do some additional set up to get pgp to
validate
> > this file. Can anyone tell me where to find a howto on this subject
or
> > tell me what to do?
>
> PGP relies on a "web of trust". Users sign each others
identities to bind
> them to keys. Your local PGP keyring will hold any keys and signatures
> you've stuffed in there. PGP determines "trust" by building a
path of
> signatures and validations between you and the target key. There are
> various parameters to determine the degree of transitivity to trust, etc.
> There's fairly extensive documentation of the PGP trust model on various
> web pages, but you can read the above warning as simply "There is no
path
> of signatures between your trusted keys and the key used to sign this
> message/file". For the highest level of confidence, attend a USENIX
or
> BSDCon key signing, and sign the security-officer key yourself once you've
> seen the fingerprint, etc. For lower levels of confidence, go to a
> key-signing event with someone who has signed the security-officer key,
> etc, etc.
>
> > Second, Do I have apply each patch, then run make after each patch,
or
> > can I apply all the patches and just run make once?
>
> It depends a bit on the patches and the branch. If you're tracking a
> release/patch branch, you can cvsup forward to the head of the branch,
> then rebuild the identified components. Sometimes, patches and update
> activities coallesce well (unrelated change to unrelated binaries).
> Sometimes, less well -- you might have to make sure to build libraries
> before binaries, for example, or apply a series of sendmail or ssh patches
> in order. Cvsuping forward and rebuilding world and kernel is a
> reasonable answer for most people, and means you don't have to worry about
> the ordering.
>
> FYI, regarding your general interest in advice: the single best piece of
> advice for remotely administered systems is to get a serial console. That
> way if something gets messed up, you have a decent chance of being able to
> fix it. It means you have full access to single-user mode, you can select
> which kernel to run at boot, even have multiple root file systems
> (production, backup) and swap between them. It takes a lot of the risk
> out of upgrades by providing a good escape route if networking fails to
> come up properly, for example. With the recent ARP fix, there was a
> functional regression in the first version of the patch, which caused
> routing to fail under some circumstances. If you had access to a serial
> console for a remote box, you were fine because you could revert to the
> previous kernel once you noticed the problem. Otherwise, you might be out
> of luck...
>
> Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
> robert@fledge.watson.org Network Associates Laboratories
>
> _______________________________________________
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>
>
>
>
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