I hadn’t looked at ssh-dss before so I Googled it a bit and from what I read 
it’s considered weak because it can be compromised by bad random generator 
implementations. OpenSSH deprecated it in 2015 with version 7.0. It might be 
better to look for a different solution. After reading 
https://issues.apache.org/jira/browse/GUACAMOLE-1504 I guess it would be better 
to upgrade libssh2 on your Guacamole server? (or use a newer container image?) 
Other options I’ve found are adding “HostKeyAlgorithms +ssh-rsa” to the end of 
/etc/ssh/sshd_config on the Ubuntu machine and restart sshd 
(https://www.reddit.com/r/linuxquestions/comments/ued2vq/comment/i736why/?utm_source=share&utm_medium=web2x&context=3)
 or change the way you generate the keys 
(https://www.reddit.com/r/selfhosted/comments/os4d52/guacamole_ssh_keys_help/)

Best regards,
Willem van de Mheen



From: Don Eugene Paul Viado <[email protected]>
Sent: Thursday, 18 August 2022 03:16
To: [email protected]
Subject: Re: Guacamole 1.4.0 support for Ubuntu 22.04 SSH

Thanks Mike for the valuable information.

On Saturday, 13 August 2022 at 10:51:32 am SGT, Michael Jumper 
<[email protected]<mailto:[email protected]>> wrote:


On Fri, Aug 12, 2022 at 7:40 PM Don Eugene Paul Viado
<[email protected]<mailto:[email protected]>> wrote:
>
> Hi,
>
> I noticed after upgrade to Ubuntu 22.04, Guacamole 1.4.0 could no longer 
> access it via SSH.
> Found out that the guacamole only supports ssh-dss?
> Workaround by adding below on sshd_config:
>
> HostKeyAlgorithms ssh-rsa,ssh-dss
> PubkeyAcceptedKeyTypes ssh-rsa,ssh-dss
>
> May we know when guacamole will support higher KeyTypes/Algo?
>

This is actually not a matter of Guacamole adding this support, but
the underlying SSH library adding this support (libssh2). With respect
to "ssh-rsa" and compatibility with newer versions of the OpenSSH
server, they did this recently:

https://github.com/libssh2/libssh2/pull/626

See: https://github.com/libssh2/libssh2/issues/634

- Mike

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