сб, 6 мар. 2021 г. в 20:41, Matthieu Herrb <matth...@herrb.eu>:
>
> On Sat, Mar 06, 2021 at 09:56:34AM -0700, Theo de Raadt wrote:
> > Matthieu Herrb <matth...@openbsd.org> wrote:
> >
> > > On Fri, Mar 05, 2021 at 09:10:32PM +0300, Vadim Zhukov wrote:
> > > > чт, 4 мар. 2021 г. в 02:02, Vadim Zhukov <persg...@gmail.com>:
> > > > >
> > > > > Hello all.
> > > > >
> > > > > Since xenodm has DEF_USER_AUTH_DIR set to "/tmp", we need to ignore
> > > > > /tmp/.Xauth* in daily cleanup, don't we?
> > > > >
> > > > > Found the hard way a few minutes ago on my X240.
> > > >
> > > > Thanks sthen@, I've realized this happens only when xenodm could not
> > > > create ~/.Xauthority. In my case this happens because my laptop starts
> > > > with /home mounted read-only, but there may be others. Mattieu, the
> > > > xenodm logic itself is correct, right? If yes, anyone brave enough to
> > > > okay the diff below then? :-)
> > >
> > > Hi,
> > >
> > > Yes I think the xenodm logic (inherithed from xdm) is correct.
> > >
> > > Althoug in my experience, when an X session cnnot write to $HOME it
> > > generally doesn't get very far (iirc not beeing able to write to
> > > .xsession-errors used to be fatal)...
>
> I tried to log in with a read-only /home and it failed as I remembered
> it. Vadim are your doing something special in you X session to make
> that work   ?

Well, I do... nothing? I can show my .xsession, there's nothing
special. I run cwm, FWIW, and do not start anything heavy from the
beginning, to have a working desktop ASAP. KDE and GNOME won't work
this way for sure. :-)

For .xsession-errors, there is /tmp-based handling in
/etc/X11/xenodm/Xsession already. Oh, now I know where the disk space
on /tmp gets lost from time to time...

> > > Anyways ok to skip that directory if it exists in daily.
> >
> > It is not a directory -- it is a file.
> >
> > I don't understand how this file is created.  Well-known names in /tmp
> > are raceable -- therefore we and others increasingly use directories 
> > containing
> > files as a safer pattern.  Where is the code that creates this file?  Is it
> > safe?  I am suspicious.
>
> It's created by mkstemp(3) in
> /usr/xenocara/app/xenodm/xenodm/auth.c:798
>
> >
> > I strongly disagree with the pattern ".Xauth*".  It should be EXACT.  If
> > someone else creates a file called .Xauthsadflkjdsaf, it should not be
> > deleted.
> >
> > As a final point, is this strategy of considering /tmp a safe place 
> > acceptable
> > at all?  If $HOME doesn't work, why not just have X fail to work correctly
> > and consider this "fail over to /tmp" a junk idea from the past?
>
> The backup dir can be configured to something else, but it needs to be
> writeable by the user whois login in. It could be a subdir of /tmp (if
> the rc.d script takes care of creating it) or I can remove that
> feature from xenodm and fail the login if /home is not writeable.

I've sent a diff for subdir of /tmp already. ;-)

--
  WBR,
  Vadim Zhukov

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