Subject: Kerberos (GSSAPI) auth fails there is an sshd banner and the client is on Linux (or Mac OS X)

From: Mike DePaulo <[email-masked]>
Date: Thu, 13 Oct 2016 16:29:36 -0400

Package: x2goclient
Version: 4.0.5.2

When the following conditions are met:
1. You are using Kerberos (GSSAPI) auth
2. You are using the Linux client (Mac client is probably affected
also, although I have not tested it. Windows is unaffected, I tested
it.)
3. A "banner" is enabled on the SSH server
4. `x2golistsessions` lists no sessions. e.g., you do not already have
a session running.
Kerberos (GSSAPI) auth fails.

This is because the x2goclient code considers the connection to have
failed if the `ssh` command has 0 length standard output (in between
the delimeters), but it does have standard error. A connection is made
to the remote system to run `x2golistsessions`, which returns no
standard output when there are no existing sessions. However, the
`ssh` command outputs the banner on standard error.

Note that the banner is outputted in a popup window, as if it were an
SSH connection error. This is a separate bug IMHO.