Modern secure SSH daemon config

sshd_config

# Modern secure (OpenSSH Server 7+) SSHd config by HacKan
# Refer to the manual for more info: https://www.freebsd.org/cgi/man.cgi?sshd_config(5)

# Server fingerprint
# Regenerate with: ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa -b 4096
HostKey /etc/ssh/ssh_host_rsa_key
# Regerate with: ssh-keygen -f /etc/ssh/ssh_host_ed25519_key -N '' -t ed25519
HostKey /etc/ssh/ssh_host_ed25519_key

# Log for audit, even users' key fingerprint
LogLevel INFO

UsePrivilegeSeparation sandbox

# Ciphers and keying
RekeyLimit 1G 1H
KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group14-sha256
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com

# Limit sessions and its duration
MaxAuthTries 2
MaxSessions 5
ClientAliveInterval 30
ClientAliveCountMax 6
TCPKeepAlive yes

UsePAM yes
PasswordAuthentication no
ChallengeResponseAuthentication no
PubkeyAuthentication yes

# You can request for several auth methods to grant access, one next to the other
#AuthenticationMethods publickey

# Enable AllowAgentForwarding if you need to jump through this host
AllowAgentForwarding yes
AllowTcpForwarding yes
X11Forwarding yes
PrintMotd no
# Compression no

# Only if you really need it:
#AcceptEnv LANG LC_*

# Enable sftp only if needed
# For Arch Linux and Debian 10+
# Subsystem       sftp    /usr/lib/ssh/sftp-server
# For Debian/Ubuntu
# Subsystem sftp /usr/lib/openssh/sftp-server -f AUTHPRIV -l INFO

# Set authorized keys file
# Prefer using an admin-controlled environment
# AuthorizedKeysFile      /etc/ssh/authorized_keys/%u
AuthorizedKeysFile      .ssh/authorized_keys

# Restrict SSH usage
AllowUsers	root
# Or restrict by group
# AllowGroups root