Subject: Bug#290: SSH key based authentication problems

From: Mike Gabriel <[email-masked]>
Date: Tue, 27 Aug 2013 12:34:01 +0200

Package: x2goclient
Tags: confirmed
Version: 4.0.1.0
Severity: important
x-debbugs-cc: [email-masked]

I myself have also observed the issue reported by Matthias. Adding  
this as a bug. This should get fixed before the release of 4.0.1.1.

Mike

----- Weitergeleitete Nachricht von [email-masked] -----
      Datum: Mon, 26 Aug 2013 23:54:55 +0200
        Von: Matthias Kauer <[email-masked]>
    Betreff: [X2Go-User] Login via ~/.ssh/authorized_keys fails
         An: [email-masked]

Hi,
I am looking for input on how to set up an ssh key-based authentication.

I generated an RSA key pair with puttygen and added it to
~/.ssh/authorized_keys2 => confirmed that I can login with putty.
Now, I specify the same private key in x2goclient (windows). I enter my
password and I am then prompted for the password of the ssh key. I enter
it and the same ssh key password prompt reappears. This seems to be an
infinite loop. When I cancel it, I get a message saying that only
publickey is supported as login method (which corresponds to my
sshd_config settings).

I then tried renaming ~/.ssh/authorized_keys and using a DSA key pair.
putty still works as expected with both of these alternatives.
x2goclient still shows the same problems however. It only lets me login
if I adapt my sshd_config and authenticate via user / password combination.

Is this a known limitation?
What is the best way to achieve high security? Can I limit the x2go
connections to only LAN IPs (without restricting the pure ssh connections)?

Best Wishes,
Matthias Kauer
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----- Ende der weitergeleiteten Nachricht -----

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---

From: Stefan Baur <[email-masked]>
Date: Tue, 27 Aug 2013 14:04:39 +0200

Hi Guys!

As a suggestion/workaround: I am using Pageant from the PuTTY suite, 
this is where I have my users load their keys.
Pageant is a SSH agent for Windows, under the same license as PuTTY and 
PuTTYgen.
The reason why I'm using it is that my users also use WinSCP for file 
transfers and thus have to authenticate only once - when 
loading/unlocking their key file in pageant.

Thus, I'm telling both x2goclient and WinSCP to use the SSH agent, and 
everything works (for me).

Please ALSO note that PuTTYgen saves the private key files in its own 
special format (as indicated by the *.ppk extension).
You might have to use one of the "Export" Options in PuTTYgen's 
"Conversions" menu so that x2goclient is able to process the key.

-Stefan

Am 27.08.2013 12:34, schrieb Mike Gabriel:
> X2Go-Dev mailing list
> [email-masked]
> https://lists.berlios.de/mailman/listinfo/x2go-dev

---

From: Matthias Kauer <[email-masked]>
Date: Wed, 28 Aug 2013 23:12:22 +0200

Hi Mike,
thanks for the confirmation and the submission.

If anyone is interested, one thing I did for now, to address this issue
was to allow password-based access from my LAN addresses as described
here:
http://askubuntu.com/questions/101670/how-can-i-allow-ssh-password-authentication-from-only-certain-ip-addresses
(Note that the match block should be at the end of sshd_config file as
it affects all statements below it if I understand it correctly)

Use a |Match| block in |/etc/ssh/sshd_config|.

|PasswordAuthentication no

Match address 192.0.2.0/24
    PasswordAuthentication yes
|

Best,
Matthias