On 4/28/2024 2:54 AM, Ulrich Sibiller wrote:

Not directly, but libssh (partly) read your ssh config. So you can add a host stanza with the settings for your destination host there.

Are you quite sure? With the following in my ssh config file

Host example.com PubkeyAcceptedAlgorithms +ssh-rsa HostKeyAlgorithms=+ssh-rsa

I can run ssh on the command line successfully but trying to start an x2go session results in

kex error : no match for method server host key algo: server [ssh-rsa,ssh-dss], client [rsa-sha2-512,rsa-sh a2-256,ssh-ed25519,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256,sk-ssh-ed25519@openssh.com,s k-ecdsa-sha2-nistp256@openssh.com]

Does x2go actually use the system ssh executable (e.g. /usr/bin/ssh)? The reason I'm asking is because I did an experiment and renamed ssh to xxx. I got the same result, shown above, when running the x2goclient! This was a surprise.

Thanks, Jon

Jon Forrest <nobozo@gmail.com <mailto:nobozo@gmail.com>> schrieb am Sa., 27. Apr. 2024, 20:30:

Due to reasons too sad to describe, I need to X2go from a modern Fedora 40 system to a Ubuntu 10.04 (!) system.

Running ssh from the command line fails with the message

Unable to negotiate with XX.XX.XX.XX port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss

After some work I got this to work by adding

-oHostKeyAlgorithms=+ssh-rsa -oPubkeyAcceptedAlgorithms=+ssh-rsa

to the ssh command line.

My question is how can I add these options to the ssh command that X2go executes on the client?

Cordially, Jon Forrest _______________________________________________ x2go-user mailing list x2go-user@lists.x2go.org <mailto:x2go-user@lists.x2go.org> https://lists.x2go.org/listinfo/x2go-user <https://lists.x2go.org/listinfo/x2go-user>

On 29/04/2024 01:38, Jon Forrest wrote:

On 4/28/2024 2:54 AM, Ulrich Sibiller wrote:

...

Not directly, but libssh (partly) read your ssh config. So you can add a host stanza with the settings for your  destination host there.

Are you quite sure?

It definitely reads it, I have something like:

Host xyz HostName example.com ... other options ...

and I can tell X2Go to connect to host xyz. However, as Ulrich points out X2Go doesn't handle the configuration in exactly the same way as ssh, for example "Include" directives are handled slightly differently.

I think that the best approach with your problem is probably to use ssh-agent and ControlPath directives. Then use your command-line ssh to establish the connection and X2Go can hopefully make use of that, even though you have such an extreme mismatch between ssh versions. You can try something like the following in .ssh/config:

Host example.com ControlPath /tmp/ssh-ctl-%l-%h-%p-%r ControlMaster auto ControlPersist 600

%C can be used in place of %l-%h-%p-%r, but the latter makes it easier to see which control socket belongs to a particular connection. (Do 'man ssh_config' for the full details on these directives.)

With the following in my ssh config file

Host example.com PubkeyAcceptedAlgorithms +ssh-rsa HostKeyAlgorithms=+ssh-rsa

I can run ssh on the command line successfully but trying to start an x2go session results in

kex error : no match for method server host key algo: server [ssh-rsa,ssh-dss], client [rsa-sha2-512,rsa-sh a2-256,ssh-ed25519,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256,sk-ssh-ed25519@openssh.com,s

k-ecdsa-sha2-nistp256@openssh.com]

Does x2go actually use the system ssh executable (e.g. /usr/bin/ssh)?

I'm pretty sure that it doesn't....

The reason I'm asking is because I did an experiment and renamed ssh to xxx. I got the same result, shown above, when running the x2goclient! This was a surprise.

.... which explains what you observed here.

I hope that this helps,

Peter.

Thanks, Jon

...

Jon Forrest <nobozo@gmail.com <mailto:nobozo@gmail.com>> schrieb am Sa., 27. Apr. 2024, 20:30:

Due to reasons too sad to describe, I need to X2go from a modern Fedora 40 system to a Ubuntu 10.04 (!) system.

Running ssh from the command line fails with the message

Unable to negotiate with XX.XX.XX.XX port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss

After some work I got this to work by adding

-oHostKeyAlgorithms=+ssh-rsa -oPubkeyAcceptedAlgorithms=+ssh-rsa

to the ssh command line.

My question is how can I add these options to the ssh command that X2go executes on the client?

Cordially, Jon Forrest _______________________________________________ x2go-user mailing list x2go-user@lists.x2go.org <mailto:x2go-user@lists.x2go.org> https://lists.x2go.org/listinfo/x2go-user <https://lists.x2go.org/listinfo/x2go-user>

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