Protocol 2                                  	                # Protocol 1 is fundamentally broken
StrictModes yes                                                 # Protects from misconfiguration

#ListenAddress [ip-here]                                        # Listening address
Port 22                                                         # Listening port. Normal 22

AuthenticationMethods publickey                                 # Only public key authentication allowed
AuthorizedKeysFile .ssh/authorized_keys
PubkeyAuthentication yes                                        # Allow public key authentication
HostKey /etc/ssh/ssh_host_ed25519_key                           # Only allow ECDSA pubic key authentication
HostKeyAlgorithms ssh-ed25519-cert-v01@openssh.com,ssh-ed25519  # Host keys the client should accepts
KexAlgorithms curve25519-sha256                                 # Specifies the available KEX (Key Exchange) algorithms
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com    # Specifies the ciphers allowed
MACs hmac-sha2-512-etm@openssh.com                		# Specifies the available MAC alg.

#Only allow incoming ECDSA and ed25519 sessions:
HostbasedAcceptedKeyTypes ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519
PubkeyAcceptedKeyTypes sk-ecdsa-sha2-nistp256@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ssh-ed25519@openssh.com,ssh-ed25519
#CASignatureAlgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519

PermitRootLogin WITHOUT-PASSWORD                                # Enable/disable root login
#AllowUsers [username]                                          # Authorized SSH users are inside the admin group
MaxAuthTries 5                                                  # Maximum allowed authentication attempts
MaxSessions 2                                                   # Maximum allowed sessions by the user

PasswordAuthentication no                                       # No username password authentication
PermitEmptyPasswords no                                         # No empty password authentcation allowed
IgnoreRhosts yes                                                # Dont read users rhost files
HostbasedAuthentication no                                      # Disable host-based authentication
ChallengeResponseAuthentication no                              # Unused authentication scheme
X11Forwarding no                                                # Disable X11 forwarding

LogLevel VERBOSE                                                # Fingerprint details of failed login attempts
SyslogFacility AUTH                                             # Logging authentication and authorization related commands
UseDNS no                                                       # Client from a location without proper DNS generate a warning in the logs

PermitTunnel no                                                 # Only SSH connection and nothing else
AllowTcpForwarding no                                           # Disablow tunneling out via SSH
AllowStreamLocalForwarding no                                   # Disablow tunneling out via SSH
GatewayPorts no                                                 # Disablow tunneling out via SSH
AllowAgentForwarding no                                         # Do not allow agent forwarding

#Banner /etc/issue.net                                           # Show legal login banner
PrintLastLog yes                                                # Show last login

ClientAliveInterval 900                                         # Client timeout (15 minutes)
ClientAliveCountMax 0                                           # This way enforces timeouts on the server side
LoginGraceTime 30                                               # Authenticatin must happen within 30 seconds
MaxStartups 2                                                   # Max concurrent SSH sessions
TCPKeepAlive yes                                                # Do not use TCP keep-alive

AcceptEnv LANG LC_*                                             # Allow client to pass locale environment variables