Split sshd module.

hosts/common/sshd.nix

@@ -0,0 +1,23 @@
+{
+  services.openssh = {
+    enable = true;
+    allowSFTP = false;
+    settings = {
+      PasswordAuthentication = false;
+      KbdInteractiveAuthentication = false;
+    };
+    extraConfig = ''
+      AllowTcpForwarding yes
+      X11Forwarding no
+      AllowAgentForwarding no
+      AllowStreamLocalForwarding no
+      AuthenticationMethods publickey
+    '';
+  };
+
+  networking.firewall = {
+    enable = true;
+    allowedTCPPorts = [ 22 ];
+    allowedUDPPorts = [ ];
+  };
+}