[X2Go-User] How to Pass SSH Options From X2goclient?

[Peter Keller]

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 at openssh.com,s 
>
> k-ecdsa-sha2-nistp256 at 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 at gmail.com <mailto:nobozo at 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 
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>>
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