[X2Go-Dev] Bug#448: x2goclient won't connect with ssh agent (Q: Who was so afraid of the NSA that he disabled agent communication in x2go?)

[Stefan Baur]

Package: x2goclient
Version: 4.0.2.0

(I'm filing this against 4.0.2.0 b/c it's still present there. If bugs
should be filed against the version they initially appeared in, please
let me know)

not affected: 4.0.0.3 with PulseAudio 0.9.6
not affected: 4.0.1.2 with PulseAudio 0.9.6
possibly affected (untested) 4.0.1.3 with PulseAudio 0.9.6
affected: 4.0.1.3+build2 with PulseAudio 0.9.6
affected: 4.0.2.0

Preface:
The followin issue has been observed on Windows; whoever takes care of
this should also check if the same issue occurs on Linux and Mac when
using the ssh agents shipped with these operating systems.

Situation:
4.0.1.2 with PulseAudio 0.9.6 and older clients allowed the use of an
external SSH agent that loads and memorizes SSH private keys (so you
don't have to re-enter your private key's passphrase whenever you try to
connect).
In my case, this SSH agent was "Pageant" from the PuTTY package.

With 4.0.1.3+build2/PA0.9.6, using the same (registry-stored) settings
as before, x2goclient.exe pops up a dialog box asking me for my private
key's password. Which it does over and over again, without ever connecting.
To me, it looks like it's asking for the password for a non-existant
private key, the key with the file name "", thus it always fails.

Assumption:
Someone tried to add/fix code regarding ssh public key authentication
(maybe something to do with bug #322?), took care of whatever issue
there was with private key file handling by x2goclient itself, but
overlooked the possibility that an external ssh agent might be involved.

Net Result:
SSH public key login using an SSH agent is effectively broken in
4.0.1.3+build2 (and possibly 4.0.1.3), up to 4.0.2.0-2014-03-06 (nightly
build), and probably still broken in the current source.

Sounds like a case for one of our two Mikes ...

-Stefan