1 files changed, 150 insertions, 0 deletions
diff --git a/nixos/modules/services/security/fail2ban.nix b/nixos/modules/services/security/fail2ban.nix
new file mode 100644
index 00000000000..2b2a54ef409
--- /dev/null
+++ b/nixos/modules/services/security/fail2ban.nix
@@ -0,0 +1,150 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  cfg = config.services.fail2ban;
+
+  fail2banConf = pkgs.writeText "fail2ban.conf" cfg.daemonConfig;
+
+  jailConf = pkgs.writeText "jail.conf"
+    (concatStringsSep "\n" (attrValues (flip mapAttrs cfg.jails (name: def:
+      optionalString (def != "") 
+        ''
+          [${name}]
+          ${def}
+        ''))));
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.fail2ban = {
+
+      daemonConfig = mkOption {
+        default =
+          ''
+            [Definition]
+            loglevel  = 3
+            logtarget = SYSLOG
+            socket    = /var/run/fail2ban/fail2ban.sock
+          '';
+        type = types.string;
+        description =
+          ''
+            The contents of Fail2ban's main configuration file.  It's
+            generally not necessary to change it.
+          '';
+      };
+
+      jails = mkOption {
+        default = { };
+        example =
+          { "apache-nohome-iptables" =
+              ''
+                # Block an IP address if it accesses a non-existent
+                # home directory more than 5 times in 10 minutes,
+                # since that indicates that it's scanning.
+                filter   = apache-nohome
+                action   = iptables-multiport[name=HTTP, port="http,https"]
+                logpath  = /var/log/httpd/error_log*
+                findtime = 600
+                bantime  = 600
+                maxretry = 5
+              '';
+          };
+        type = types.attrsOf types.string;
+        description =
+          ''
+            The configuration of each Fail2ban “jail”.  A jail
+            consists of an action (such as blocking a port using
+            <command>iptables</command>) that is triggered when a
+            filter applied to a log file triggers more than a certain
+            number of times in a certain time period.  Actions are
+            defined in <filename>/etc/fail2ban/action.d</filename>,
+            while filters are defined in
+            <filename>/etc/fail2ban/filter.d</filename>.
+          '';
+      };
+      
+    };
+
+  };
+
+  
+  ###### implementation
+
+  config = {
+
+    environment.systemPackages = [ pkgs.fail2ban ];
+
+    environment.etc =
+      [ { source = fail2banConf;
+          target = "fail2ban/fail2ban.conf";
+        }
+        { source = jailConf;
+          target = "fail2ban/jail.conf";
+        }
+        { source = "${pkgs.fail2ban}/etc/fail2ban/action.d/*.conf";
+          target = "fail2ban/action.d";
+        }
+        { source = "${pkgs.fail2ban}/etc/fail2ban/filter.d/*.conf";
+          target = "fail2ban/filter.d";
+        }
+      ];
+
+    system.activationScripts.fail2ban =
+      ''
+        mkdir -p /var/run/fail2ban -m 0755
+      '';
+
+    systemd.services.fail2ban =
+      { description = "Fail2ban intrusion prevention system";
+
+        wantedBy = [ "multi-user.target" ];
+        after = [ "network.target" ];
+      
+        restartTriggers = [ fail2banConf jailConf ];
+        path = [ pkgs.fail2ban pkgs.iptables ];
+        
+        serviceConfig =
+          { ExecStart = "${pkgs.fail2ban}/bin/fail2ban-server -f";
+            ReadOnlyDirectories = "/";
+            ReadWriteDirectories = "/var/run/fail2ban /var/tmp";
+            CapabilityBoundingSet="CAP_DAC_READ_SEARCH CAP_NET_ADMIN CAP_NET_RAW";
+          };
+
+        postStart =
+          ''
+            fail2ban-client reload
+          '';
+      };
+
+    # Add some reasonable default jails.  The special "DEFAULT" jail
+    # sets default values for all other jails.
+    services.fail2ban.jails.DEFAULT =
+      ''
+        ignoreip = 127.0.0.1/8
+        bantime  = 600
+        findtime = 600
+        maxretry = 3
+        backend  = auto
+      '';
+
+    # Block SSH if there are too many failing connection attempts.
+    services.fail2ban.jails."ssh-iptables" =
+      ''
+        filter   = sshd
+        action   = iptables[name=SSH, port=ssh, protocol=tcp]
+        logpath  = /var/log/warn
+        maxretry = 5
+      '';
+    
+  };
+
+}