[X2go-dev] sudo permissions?

[Rob Lemley]

Hey folks,

I've been toying around with x2go a bit, and I'm really liking it.
>From what I've seen, the overall architecture is cleaner than freenx
and even neatx. Certainly none of that insanity of netcat's and
fdcopy's.

I was a rather disturbed by the x2goserver package adding a line in my
sudoers file to allow anyone in the x2gousers group to run
x2gopgwrapper as root. I checked out that script and the three scripts
it can potentially call, x2gopgwrapper_{local,net,sqlite}. Other than
the _net script I see no reason why root access is required. All these
scripts do is access a database and run queries. The _net script as
written probably needs root access, but there's no reason why with
some permission adjustments on the postgres database server that it
can't run unprivileged as well.

As I'm just using sqlite on a single system, I did a little experiment
and made some changes to run that script as an unprivileged user.

I created an unprivileged x2go user with no password:  (The defaults
with this particular invocation of useradd are adequate, but the
account can be restricted some more)
useradd -r x2go

So the sudoers entry becomes:
#### X2GO section
%x2gousers ALL=(x2go) NOPASSWD: /usr/bin/x2gopgwrapper

Then permissions on the sqlite database need changing so our x2go user
can run its queries:
cd /var/db
sudo chown -R x2go.x2go x2go

Finally, the scripts in /usr/bin need to be changed so that
x2gopgwrapper runs at x2go:
for i in x2go*; do sed -ibak -e 's/sudo x2gopgwrapper/sudo -u x2go
x2gopgwrapper/' $i; done

I made these changes on my system and have not had any issues
connecting. I am only using the x2goserver package at the moment; it's
just this one script that gets executed as root, I don't know about
any of the other packages.

There's also the matter of the x2gocleansessions cleanup script...
There's a couple of sudo calls in there as well, I didn't change that
just yet as I've just disabled it altogether to prevent the spam it
sends to my syslog.

I apologize if this topic has been brought up before or is discussed
in the documentation someplace; I looked around and didn't see
anything. I simply bring this up in the interest of system security.
The fewer things that run as root the better.

The changes I describe above are my quick hack-n-fix. If I get a
chance in the next few days I can throw together a proper fix and
submit a patch. (And please add my vote to the yes-please git
repository crowd.)


X2go seems to have a lot of possibilities and potential. Thanks to
Heinz and Alex for their hard work.

^_^ rob