init

ansible/roles/harden/sshd_config/templates/00-sshd_config-hardening.conf.j2

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+# --- MAIN ---
+
+# Change default port 22 → {{ ssh_port }} (reduces noise from scanners)
+Port {{ ssh_port }}
+
+# Optionally limit interfaces (default is all)
+# ListenAddress 0.0.0.0   # IPv4
+# ListenAddress ::        # IPv6
+
+# Allow only SSH protocol version 2 (v1 is insecure)
+Protocol 2
+
+
+# --- AUTHENTICATION ---
+
+# Disable root login (only via sudo)
+PermitRootLogin prohibit-password
+
+# Disable password login (keys only)
+PasswordAuthentication no
+
+# Disable interactive keyboard auth (OTP, TOTP, etc.)
+KbdInteractiveAuthentication no
+
+# Disable challenge-response auth (legacy)
+ChallengeResponseAuthentication no
+
+# Enable public key authentication (main method)
+PubkeyAuthentication yes
+
+
+# --- ACCESS ---
+
+# Allow only specific user
+# AllowUsers adminuser
+# Or alternatively allow a group:
+# AllowGroups sshusers
+
+
+# --- FUNCTION RESTRICTIONS ---
+
+# Disallow empty passwords
+PermitEmptyPasswords no
+
+# Disallow user environment modification (~/.ssh/environment)
+PermitUserEnvironment no
+
+# Disable X11 forwarding (no GUI sessions)
+X11Forwarding no
+
+# Disable TCP forwarding (no tunnels)
+AllowTcpForwarding yes
+
+# Disable gateway ports (no external binding)
+GatewayPorts no
+
+# Disable VPN tunnels via SSH
+PermitTunnel no
+
+# Disable SSH agent forwarding
+AllowAgentForwarding yes
+
+
+# --- ANTI-BRUTEFORCE & STABILITY ---
+
+# Login timeout (20 seconds)
+LoginGraceTime 20
+
+# Max 3 auth attempts per connection
+MaxAuthTries 3
+
+# Limit simultaneous connections
+# Allow 10 new, start dropping at 30, max 60 queued
+MaxStartups 10:30:60
+
+
+# --- SESSION ACTIVITY ---
+
+# Ping client every 300s (5 minutes)
+ClientAliveInterval 300
+
+# Disconnect if no response twice
+ClientAliveCountMax 2
+
+# Disable TCP keepalive
+TCPKeepAlive no
+
+# Skip DNS checks for faster login
+UseDNS no
+
+
+# --- SFTP ---
+
+# Use internal SFTP subsystem
+Subsystem sftp internal-sftp
+
+
+# --- CRYPTOGRAPHY (optional) ---
+
+# Modern key exchange algorithms (if supported)
+# KexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256
+
+# Modern ciphers
+# Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr
+
+# Modern MAC algorithms
+# MACs umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com