[X2Go-Dev] X2go crash on Fedora 37, port already in use?

Wed Jan 4 17:07:54 CET 2023

The chmod commands allowed X2Go to open. So perhaps not a bug per se but a
suggestion to improve on some error checking.

We still use NIS/yp (yes it's ok to groan). The NIS server included the
x2gouser GID in /etc/group.  This led to creation of the user when x2go was
installed adopting that GID (461) in /etc/passwd instead of the one that
the installation created (973) in /etc/group.  (Thus /etc/passwd had
x2gouser:x:977:461 while /etc/group had x2gouser:x:973.)  The GID of the
setgid program /usr/lib64/x2go/libx2go-server-db-sqlite3-wrapper was the
one in /etc/group, namely 973, while the GID of /var/lib/x2go and
/var/lib/x2go/x2go_sessions was the one in /etc/passwd, namely 461.  Hence
when the process adopted the GID 973 of the wrapper, it was not granted
access to files with GID 461.

This caused any of the x2go library scripts that access the database to
fail when run as a normal user,  In practice, the first one that is run as
a session is starting is x2gogetports, which returned a "cannot open file"
error message instead of a list of port numbers.  This error message (or
more precisely the first "word" of it) was fed to x2gocheckports at line
131, which tried to interpret it as a port number, and got a syntax error
as a result.

In fact, there are many ways that the x2go server process could fail to
open the database file.  All of them will generate the exact same error
message.  If I may suggest a change, it would be to catch these errors
earlier (e.g. by a success code from x2gogetports and its kin) and report
the file open failure with a message based on the errno, (e.g. no such file
or access denied).  This would narrow down the possible causes of the
failure.

Thanks for all of your suggestions in getting this to work.

On Mon, Jan 2, 2023 at 3:52 AM <me at jcn50.com> wrote:

> It could be a bug: the version distributed with Fedora 37 is
> 4.1.0.3-19.fc37.x86_64.rpm whereas the one in CentOS 8 is
> x2goserver-4.1.0.3-17.el8.1.x86_64.rpm , with this showing in the change
> log:
>
> 2022-07-23 - Fedora Release Engineering <releng at fedoraproject.org> -
> 4.1.0.3-19
> - Rebuilt for
> https://urldefense.proofpoint.com/v2/url?u=https-3A__fedoraproject.org_wiki_Fedora-5F37-5FMass-5FRebuild&d=DwIDaQ&c=aqMfXOEvEJQh2iQMCb7Wy8l0sPnURkcqADc2guUW8IM&r=X0jL9y0sL4r4iU_qVtR3lLNo4tOL1ry_m7-psV3GejY&m=c4doz1suIijY2NueNOG6O9qnEmjwZUxxuWDG4ja3upV5tc8ZxcyS12WTuJJIWT3F&s=L9tIePHQQsnuZYnxUL9fh-gQnR4Rx0oKIVntrG7c-LE&e=
> 2022-05-30 - Jitka Plesnikova <jplesnik at redhat.com> - 4.1.0.3-18
> - Perl 5.36 rebuild
>
> Those are the permissions I have on my side (on Debian 11 but it should
> be the same):
> root at dev:~# ls -lah /var/lib/
> drwxrwx---+  2 x2gouser x2gouser 4.0K Dec 29 01:37 x2go
>
> root at dev:~# ls -lah /var/lib/x2go/
> -rw-rw----+  1 root     x2gouser  40K Dec 29 01:37 x2go_sessions
>
> So try this:
> sudo chmod 0770 /var/lib/x2go && sudo chown x2gouser:x2gouser
> /var/lib/x2go && sudo chmod 0660 /var/lib/x2go/x2go_sessions && sudo
> chown root:x2gouser /var/lib/x2go/x2go_sessions && echo "PERMISSIONS
> FIXED"
>
> If it still doesn't work: maybe you can revert to version
> x2goserver-4.1.0.3-17 ? I tried to find the package for Fedora 37 but
> could only find the el8 ones... Maybe this command would work:
> sudo dnf install x2goserver-4.1.0.3-17.fc37
> Otherwise, the only last option to test out would be to use the EPEL8
> repo and install the x2goserver-4.1.0.3-17.el8 package...
>
>
> Regards,
> Chris,
> Quantum Hosting®.
>
> On 2023-01-02 02:26, Robert Kudyba wrote:
> > Well a hypothesis was tested with simply changing permissions as
> > follows X2Go launched:
> >
> > sudo chmod 777 /var/lib/x2go
> > pascal:~/$ sudo chmod 666 /var/lib/x2go/x2go_sessions
> >
> > Is x2go_sessions is needed after a session is up and running?
> >
> > This proves that it is a problem of permission to read and write the
> > db.  Permission should be gotten via the sgid wrapper, but for some
> > reason it is not.
> >
> > Uninstalling and reinstalling did not work.
> >  Is there a script to fix permissions correctly? Should we remove the
> > x2go user and group and re-add?
> >
> > On Sun, Jan 1, 2023, 2:33 PM <me at jcn50.com> wrote:
> >
> >> Hi again Robert,
> >>
> >> I have tried (and succeeded) on a server using AlmaLinux 8 (I don't
> >> have
> >> access to Fedora 37, sorry) and this is the command I used (you
> >> might
> >> skip the 2x "epel" commands?):
> >>
> >> dnf upgrade -y && dnf install
> >>
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__dl.fedoraproject.org_pub_epel_epel-2Drelease-2Dlatest-2D8.noarch.rpm&d=DwIDaQ&c=aqMfXOEvEJQh2iQMCb7Wy8l0sPnURkcqADc2guUW8IM&r=X0jL9y0sL4r4iU_qVtR3lLNo4tOL1ry_m7-psV3GejY&m=7p_4VYLAUDElk8vMZgdq0Z9McN077vuO0VabguwetT409bSXJvY1JoGQ0Pc6wHog&s=zksEEUIvkzgtDnM8715wOsqYfM21ArqKZhRQdldhWWA&e=
> >>
> >> -y && dnf config-manager --enable epel && dnf config-manager
> >> --set-enabled powertools && dnf install -y xfdesktop gtk-doc xfce*
> >> --exclude=xfce4-sensors-plugin-devel lightdm firefox x2goserver
> >> x2goserver-xsession && systemctl isolate graphical.target &&
> >> systemctl
> >> set-default graphical.target && echo "PLEASE REBOOT NOW"
> >>
> >> Pausing and resuming the session didn't work though (probably bec my
> >> 1x
> >> CPU and 768 MB RAM are too small!).
> >>
> >> Again: I really prefer the LXQt or LXDE on Ubuntu/Debian as it is a
> >> lot
> >> faster than XFDE...(I can't imagine how slow MATE could be!).
> >>
> >> Regards,
> >> Chris,
> >> Quantum Hosting®.
>
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