Dropbear difficulties due to outdated version?

[Matt Johnston]

On 2022-06-25 7:49 am, James Miller wrote:
> I set up a small low-resource VPS a few years ago to use mainly as a
> light-use xmpp server. I got Dropbear operating there so I could admin
> it. Dropbear seemed a good choice since system resources were so
> anemic. I recall it being quite challenging to get key-pair
> authentication to finally work there, though I can't recall many
> details about how I finally succeeded.

Most likely would be OpenSSH requiring sha2 for RSA signatures. If you 
can use
ecdsa keys instead those should work OK.

Alternatively to keep using RSA, set

     Host old-host
         HostkeyAlgorithms +ssh-rsa
	PubkeyAcceptedAlgorithms +ssh-rsa

in your .ssh/config for the client which will allow the older sha1 RSA 
signatures.
Which OpenSSH version is it? https://www.openssh.com/releasenotes.html 
has details
of what has been deprecated.

Matt

> The VPS runs Ubuntu 16.04 (EMS), so the version of Dropbear there is a
> bit outdated (v2017.75). Since that release was made, various changes
> have happened to openssh that may, I assume, make it incompatible with
> this version of Dropbear. I am using ssh when I try to connect to the
> VPS, btw.