[X2Go-Dev] Bug#1202: kex error : no match for method mac algo client->server: server [hmac-sha2-256, hmac-sha2-512], client [hmac-sha1]

J. M. van Bilsen jbilsen at xs4all.nl
Wed Aug 30 21:09:19 CEST 2017

Package: x2goclient 

Complete system info :

 $ which x2goclient
 $ cat /etc/lsb-release 
DISTRIB_DESCRIPTION="Linux Mint 18.1 Serena"

 $ dpkg --list | grep x2goclient
ii  x2goclient                                        
-1                                    amd64        X2Go Client
application (Qt4)

WARNING my assumption is this problem will be on all x2goclient

After change of the security settings on sshd we cannot connect using
Using portforwarding ssh -L 9999:localhost:22 someremotehost then
letting x2goclient connect to localhost port 9999 works.

Settings in sshd_config

MACs hmac-sha2-256,hmac-sha2-512

When connecting we get error message :

kex error : no match for method mac algo client->server: server [hmac-
sha2-256,hmac-sha2-512], client [hmac-sha1]

My assumption is client is configured using hmac-sha1 as default

Problem does not surface using ssh or ssh port forwarding.

Problem can be easy reproduced using raspberry with mathe and MACs
hmac-sha2-256,hmac-sha2-512 in sshd_config

Problem surface also with different ssh proxy servers having the MACs
setting. As stated before normal connection on ssh or using port
forwarding no problem.

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