(WIP) Install fail2ban using system manager

Author: yvan-sraka

nix/systemConfigs.nix

@@ -1,9 +1,11 @@
 { self, inputs, ... }:
 let
   mkModules = system: [
+    self.systemModules.fail2ban
     ({
       services.nginx.enable = true;
       nixpkgs.hostPlatform = system;
+      supabase.services.fail2ban.enable = true;
     })
   ];
 

nix/systemModules/default.nix

@@ -4,6 +4,8 @@
 {
   imports = [ ./tests ];
   flake = {
-    systemModules = { };
+    systemModules = {
+      fail2ban = ./fail2ban.nix;
+    };
   };
 }

nix/systemModules/dummy-sshd.nix

@@ -0,0 +1,9 @@
+{ lib, ... }:
+{
+  options = {
+    services.openssh = lib.mkOption {
+      type = lib.types.attrs;
+      default = { };
+    };
+  };
+}

nix/systemModules/fail2ban.nix

@@ -0,0 +1,100 @@
+{
+  lib,
+  nixosModulesPath,
+  config,
+  ...
+}:
+let
+  cfg = config.supabase.services.fail2ban;
+in
+{
+  imports = [
+    # We use a dummmy sshd module to workaround this error when importing "/services/networking/ssh/sshd.nix":
+    #   error: The option `users' in module `/nix/store/...-source/nix/modules'
+    #   would be a parent of the following options, but its type `attribute set' does not support nested options.
+    #   - option(s) with prefix `users.users' in module `/nix/store/...-source/nixos/modules/services/networking/ssh/sshd.nix'
+    # FIXME: it would be better to rely on userborn in system-manager:
+    # https://github.com/numtide/system-manager/pull/266
+    ./dummy-sshd.nix
+  ]
+  ++ map (path: nixosModulesPath + path) [
+    "/services/security/fail2ban.nix"
+  ];
+
+  options = {
+    supabase.services.fail2ban = {
+      enable = lib.mkEnableOption "Fail2Ban";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    # TODO: (last bit form Ansible task)
+    # - name: Configure journald
+    #   copy:
+    #     src: files/fail2ban_config/jail-ssh.conf
+    #     dest: /etc/fail2ban/jail.d/sshd.local
+    #   when: debpkg_mode or nixpkg_mode
+    supabase.services.fail2ban = {
+      enable = true; # FIXME: fail2ban was disabled in ansible/tasks/setup-fail2ban.yml
+      bantime = "3600";
+      jails = {
+        postgresql = {
+          settings = {
+            enabled = true;
+            port = "5432";
+            protocol = "tcp";
+            filter = "postgresql";
+            logpath = "/var/log/postgresql/auth-failures.csv";
+            maxretry = 3;
+            ignoreip = "192.168.0.0/16 172.17.1.0/20";
+          };
+        };
+        pgbouncer = {
+          settings = {
+            enabled = true;
+            port = "6543";
+            protocol = "tcp";
+            filter = "pgbouncer";
+            backend = "systemd[journalflags=1]";
+            maxretry = 3;
+          };
+        };
+      };
+      # TODO: extraPackages = [ pkgs.nftables ];
+    };
+
+    environment.etc = {
+      "fail2ban/jail.local".text = ''
+        [DEFAULT]
+        banaction = nftables-multiport
+        banaction_allports = nftables-allports
+      '';
+
+      "fail2ban/filter.d/postgresql.conf".text = ''
+        [Definition]
+        failregex = ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user.*$
+        ignoreregex = ^.*,.*,.*,.*,"127\.0\.0\.1.*password authentication failed for user.*$
+                      ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user ""supabase_admin".*$
+                      ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user ""supabase_auth_admin".*$
+                      ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user ""supabase_storage_admin".*$
+                      ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user ""authenticator".*$
+                      ^.*,.*,.*,.*,"<HOST>:.*password authentication failed for user ""pgbouncer".*$
+      '';
+
+      "fail2ban/filter.d/pgbouncer.conf".text = ''
+        [Definition]
+        failregex = ^.+@<HOST>:.+password authentication failed$
+        journalmatch = _SYSTEMD_UNIT=pgbouncer.service
+      '';
+    };
+
+    systemd.services.fail2ban = {
+      wantedBy = lib.mkForce [
+        "system-manager.target"
+      ];
+      # TODO:
+      # after = [ "nftables.service" ];
+      # wants = [ "nftables.service" ];
+    };
+  };
+}

nix/systemModules/tests/test_fail2ban.py

@@ -0,0 +1,7 @@
+# from time import sleep
+
+
+def test_fail2ban_service(host):
+    # sleep(5000) # Handy for interactive debugging (with docker exec -it $CONTAINER_ID /bin/bash)
+    assert host.service("fail2ban.service").is_valid
+    assert host.service("fail2ban.service").is_running, "Fail2Ban service should be running but failed: {}".format(host.run("systemctl status fail2ban.service").stdout)