ssh -X fails without warning when xauth not installed

[Pavel Šimerda]

Binary package hint: xauth

SSH with X11 Forwarding enabled on both sides fails when xauth is not installed.

This looks reasonable because X Forwarding needs xauth. But the user should be warned that something failed and why. Now he's just wondering what's wrong and why there's no DISPLAY variable.

[Mark Reitblatt (mark-reitblatt)]

This is really more of a request, and would be most effectively handled by filing upstream. However, it seems to me that perhaps xauth should be in openssh-client's "recommends" or "requires" list, not just "suggests". It should also be noted in the config file since xauth is not installed by default with openssh-client.

[Nicolas Valcarcel (nvalcarcel)]

I see 2 ways of fixing this:
1) Add xauth to the dependencies of openssh-client.
2) Add a warning message if the user uses -X and have no xauth installed.

I also think it's an openssh-client bug, not a xauth problem ("Binary package hint": must be openssh-client)

[Nicolas Valcarcel (nvalcarcel)]

Attaching a patch.

[Colin Watson (cjwatson)]

Nicolas, thanks, but I'm not sure that really addresses the bug. Even after this it will still be the case that ssh -X will fail confusingly if xauth is not installed.

A dependency would definitely not be appropriate - it needs a warning message.

[Colin Watson (cjwatson)]

I've committed an improved variant of Nicolas' patch to my Debian tree, but have unsubscribed ubuntu-main-sponsors as I still think this needs further work.

[Nicolas Valcarcel (nvalcarcel)]

Can someone confirm the bug and if it's still valid paste the output here to add a warning saying that this package should be installed.

[Victor Engmark (victor-engmark)]

Confirmed on Ubuntu Server 9.10 - Please reset status.

Details:
/etc/ssh/sshd_config contained
X11Forwarding yes
X11DisplayOffset 10

ssh -X and ssh -Y worked fine, but DISPLAY was not set, and the result was the following:
$ meld foo bar
/var/lib/python-support/python2.5/gtk-2.0/gtk/__init__.py:72: GtkWarning: could not open display
  warnings.warn(str(e), _gtk.Warning)
/usr/lib/meld/gnomeglade.py:123: GtkWarning: cannot open display:
  self.program = gnome.program_init(name, version)

Installing xauth worked:
$ sudo apt-get install xauth
$ logout
$ ssh -Y hostname
$ meld foo bar &