OpenWRT Dropbear v2020.80: Exit before auth: No matching algo kex

[Jamie Lokier]

Walter Harms wrote:
> This is caused by changes in ssh_config. You can try:
>   ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 USER at TARGET 
> 
> or persistent in ssh_config 
> KexAlgorithms=+diffie-hellman-group1-sha1 
> 
> your mileage may vary etc.
> 
> re,
>  wh

Thanks!

This advice has shown me how to connect directly to an old OpenSSH server again
(not Dropbear), instead of via intermediate hops on intermediate servers :)

However after reading [1] I decided a safer kex is diffie-hellman-group14-sha1
(group14 instead of group1).

Mentioning this in case it's also an option for old Dropbear/OpenWRT users.

[1] https://tools.ietf.org/id/draft-ietf-curdle-ssh-kex-sha2-09.html#rfc.section.3.4
"Key Exchange (KEX) Method Updates and Recommendations for Secure Shell (SSH)".

Best,
-- Jamie