nix-config/modules/nixos/services/fail2ban/default.nix

# Filter and ban unauthorized access
{ config, lib, ... }:
let
  cfg = config.my.services.fail2ban;
  wgNetCfg = config.my.services.wireguard.net;
in
{
  options.my.services.fail2ban = with lib; {
    enable = mkEnableOption "fail2ban daemon";
  };

  config = lib.mkIf cfg.enable {
    services.fail2ban = {
      enable = true;

      ignoreIP = [
        # Wireguard IPs
        "${wgNetCfg.v4.subnet}.0/${toString wgNetCfg.v4.mask}"
        "${wgNetCfg.v6.subnet}::/${toString wgNetCfg.v6.mask}"
        # Loopback addresses
        "127.0.0.0/8"
      ];

      maxretry = 5;

      bantime-increment = {
        enable = true;
        rndtime = "5m"; # Use 5 minute jitter to avoid unban evasion
      };

      jails.DEFAULT.settings = {
        findtime = "4h";
        bantime = "10m";
      };
    };

    my.system.persist.directories = [
      "/var/lib/fail2ban"
    ];
  };
}