X2Go Bug report logs - #1520
Proxy-Server - SSH - strong Cipher crash x2Go-Client

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Message #5 received at submit@bugs.x2go.org (full text, mbox, reply):

From: <Marian.Schwarcz@dlr.de>

To: <submit@bugs.x2go.org>

Subject: Proxy-Server - SSH - strong Cipher crash x2Go-Client

Date: Thu, 14 Jan 2021 07:47:33 +0000

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Package: x2goClient
Version: 4.1.2.2-2020.02.13

Host-System: Windows 10, und Windows Server 2012 R2 (German Language)
Installations-Typ: Recommended (Default)

*** Problem Description ***
When using x2GoClient via jumpserver (as SSH-Proxy-Server), then is X2GoClient automatic closed (without any Information). Problem are the SSH-Strong-Ciphers, which are configured in SSHd on Jumpserver. Strong Ciphers => x2GoClient crashed. If default Ciphers => x2GoClient and connection works.

*** X2GoClient - Configuration ***
Sitzungsname: test
Pfad: /
Host: ziel-server
Login: test_ye
SSH-Port: 22

Proxy-Server für SSH-Verbindung verwenden
SSH
Host: jumpserver
Port: 22
Gleiche Anmeldung wie für X2Go-Server
Gleiches Kennwort wie für X2Go-Server

XFCE

*** Jumpserver Configuration) ***
Jumpserver SSHd Config: /etc/ssh/sshd_config  (CentOS 7)
Ciphers aes128-ctr,aes192-ctr,aes256-ctr

The ciphers are used for strong Encryption. Then access from x2GoClient via jumpserver cannot handle this.
------

When the Cipher-Restriction is not configured:
Jumpserver SSHd Confg: (CentOS 7)
#Ciphers aes128-ctr,aes192-ctr,aes256-ctr

then the connection from x2GoClient via jumpserver to Destination X2Go-Server does work.


I hope I provided all needed information for you. Let me know if this can be patched, or does our Company need to search for other solution.
Thank you.

Best regards,
Marián Schwarcz

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Message #10 received at 1520@bugs.x2go.org (full text, mbox, reply):

From: Adam Dorsey - NOAA Affiliate <adam.dorsey@noaa.gov>

To: 1520@bugs.x2go.org

Cc: Nathan Gregg - NOAA Affiliate <nathan.gregg@noaa.gov>, Chance Taylor - NOAA Affiliate <chance.taylor@noaa.gov>

Subject: RE: Proxy-Server - SSH - strong Cipher crash x2Go-Client

Date: Fri, 19 Mar 2021 14:28:38 -0400

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I can confirm this issue in my own environment as well.  X2Go server
version is 4.1.0.3-9.el7 running on CentOS 7.  Affected users are running
X2Go client version 4.1.2.2 on Windows 10 (though this may affect other
Windows versions as well).

We forced the use of the aes128-ctr cipher yesterday on our cluster login
nodes to resolve a security issue raised by our security team.  To do this,
we added the following line to our SSH server config file:

Ciphers aes128-ctr

After making this change, several users running the X2Go client on Windows
10 could no longer connect.  We found this bug report, and subsequently
reverted the above change, which resolved the issue.

Please note that Linux clients appeared to be unaffected by this issue; I
was able to connect from a workstation running X2Go client version 4.1.2.2
on Ubuntu Linux 20.04 without any issues.

-- 
Adam Dorsey
NOAA RDHPCS Systems Administrator Site Lead
CSRA / RedLine Performance Solutions, LLC

NOAA NESCC
1000 Galliher Drive, Suite 333, Fairmont, WV 26554
office: (304) 367-2882
cell: (304) 685-9345
adam.dorsey@noaa.gov

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