X2Go Bug report logs - #1253
ssh broker : bad error feedback in interaction mode

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Date: Tue, 13 Feb 2018 19:29:45 +0100 (CET)
From: Walid MOGHRABI <w.moghrabi@servicemagic.eu>
To: submit@bugs.x2go.org
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Subject: ssh broker : bad error feedback in interaction mode
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package: x2gobroker-ssh
version: 0.0.4.0-0~972~ubuntu16.04.1
priority: bug

Using the ssh broker is great because it adds the ability for the x2goclient to interact with the auth mechanism such as PAM so that you get notified that you need to renew a password for example.
This is great but it doesn't always work well.

For example, the user don't get the reason why the access is denied.

Here are different tests I made based on the following setup : x2gobroker in ssh mode with local PAM auth based on Samba Winbind/Kerberos.

I tried both situations to compare :
* with the x2goclient in broker-ssh mode
* with a term rying to connect through SSH


1) Account set for password change with temporary password in Active Directory, user type wrong password (neither old or new one)
* with x2goclient: get message "Access denied. Authentication that can continue: publickey,password,keyboard-interactive"
* with term : "Your account has been locked. Please contact your System administrator. Password: "


2) Account set for password change with temporary password in Active Directory, user type good password

* with x2goclient: get a new password form in order to type (and confirm) the new password. Reseting password works and you get logged in to the broker with the sessions list displayed.
However, if you click on the "cancel" button, x2goclient freeze and must be killed, you're not sent back to the login form.
On the other hand, if you change your password and then be logged in, clicking on the session slot fails because this is the old password that is relayed to the session slot and not the new one. When it fails, you get a new login form to enter your password again, if you type the new password there, it works.

* with term: 
    "Password: ******"
    "Password expired.  You must change it now."
    "Enter new password: ******"
    "Enter it again: ******"
If you cancel (ctrl+c), nothing happen and you get back to the prompt.
If you enter the good old password, you're prompted to change it then you're logged in.
If you enter the wrong password, your prompted to retry 2 times then you get this message "Your account has been locked. Please contact your System administrator" (this is our security policy, this is normal behaviour, 2 fauils then blocked for 10mn.


3) Account disabled in Active Directory
* with x2goclient: get message "Access denied. Authentication that can continue: publickey,password,keyboard-interactive"
* with term : "Your account has been locked. Please contact your System administrator. Password: "


Would be great to fix the issues in 2) and would be great to retrieve the error message directly from PAM so that we get the reason.

Regards,
Walid Moghrabi

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