# OpenSSH client configuration
#
# set some basic hardening options for all connections
Host *
        # disable Roaming as it is known to be vulnerable
        UseRoaming no

        # only use secure crypto algorithm
        KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
        Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
        MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com

        # always visualise server host keys (has no technical
        # effect, but helps to identify key based MITM attacks)
        VisualHostKey yes

        # use SSHFP (might work on some up-to-date networks) to look up host keys
        VerifyHostKeyDNS yes

        # send keep-alive messages to connected server to avoid broken connections
        ServerAliveInterval 10
        ServerAliveCountMax 6

        # disable X11 forwarding (security risk)
        ForwardX11 no

        # always check server IP address
        CheckHostIP yes

        # ensure only allowed authentication methods are used
        PreferredAuthentications publickey,keyboard-interactive,password

# EOF