Boug using different OpenSSH versions

OBSD-6.8-beta OpenSSH YASM

2020-10-13

Oscaillaly I had problems with OpenSSH when using different versions, it would struck forever

debug1: expecting SSH2_MSG_KEX_ECDH_REPLY

I would just decrease MTU with ifconfig

ifconfig <interface> mtu 1200

It started bothering when wireguard interface started having this issue on OBSD-6.8-meta.

The server I'm connecting to, running OBSD-6.7 has OpenSSH_8.3 LibreSSL 3.1.1

I'm one subversion ahead on both.

Solution, from ServerFault Chossing different MACs Algorithm than hmac-md5

# on /etc/ssh/ssh_config removed above algo
MACs hmac-sha1,umac-64@openssh.com

(so what's MTU? different MACs algo? no idea now /o\)