client should compatible with SSH AUTH protocol - rfc4252

[ericwq]

• Authentication Methods and Their Order in SSH
• How to set the preferred authentication method for SSH

[ericwq]

for server: How can I list MACs, Ciphers and KexAlogrithms supported by my ssh server?

sshd -T | grep "\(ciphers\|macs\|kexalgorithms\)"

for client:

     PreferredAuthentications
             Specifies the order in which the client should try authentication methods.  This allows a client to prefer one method
             (e.g. keyboard-interactive) over another method (e.g. password).  The default is:

                   gssapi-with-mic,hostbased,publickey,
                   keyboard-interactive,password

[ericwq]

for client:

           1.   command-line options
           2.   user's configuration file (~/.ssh/config)
           3.   system-wide configuration file (/etc/ssh/ssh_config)

[ericwq]

plan to support only two auth methods: publickey, password. agent is just a shortcut for publickey auth method. rfc4254

[ericwq]

verified.