If you ever met the following errors when trying to git or ssh after upgraded your OS to sierra:
Unable to negotiate with legacyhost: no matching host key type found. Their offer: ssh-dss
Just relax, it’s not your fault but your server’s fault. Upgrading your OS to sierra will also bump your OpenSSH from version 6.9 to 7.2. According to the document of OpenSSH 7 (http://www.openssh.com/legacy.html):
OpenSSH 7.0 and greater similarly disable the ssh-dss (DSA) public key algorithm. It too is weak and we recommend against its use. It can be re-enabled using the HostKeyAlgorithms configuration option:
ssh -oHostKeyAlgorithms=+ssh-dss user@legacyhost
or in the ~/.ssh/config file:
Host somehost.example.org
HostKeyAlgorithms +ssh-dss
However, it is probably not enough. You may be prompted for password all the time but no password is correct. In that case, you can simply append another line in your ~/.ssh/config file:
PubkeyAcceptedKeyTypes +ssh-dss
That’s it! Don’t forget to restart your sshd service before retrying.
