nixpkgs/nixos/modules/services/security/sshguard.nix
Andreas Brenk 36da345caa nixos/sshguard: use nftables backend if enabled
The current module assumes use of iptables and breaks if nftables is
used instead.

This change configures the correct backend based on the
config.networking.nftables.enable setting.
2020-01-27 14:42:28 +01:00

156 lines
5.1 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.sshguard;
in {
###### interface
options = {
services.sshguard = {
enable = mkOption {
default = false;
type = types.bool;
description = "Whether to enable the sshguard service.";
};
attack_threshold = mkOption {
default = 30;
type = types.int;
description = ''
Block attackers when their cumulative attack score exceeds threshold. Most attacks have a score of 10.
'';
};
blacklist_threshold = mkOption {
default = null;
example = 120;
type = types.nullOr types.int;
description = ''
Blacklist an attacker when its score exceeds threshold. Blacklisted addresses are loaded from and added to blacklist-file.
'';
};
blacklist_file = mkOption {
default = "/var/lib/sshguard/blacklist.db";
type = types.path;
description = ''
Blacklist an attacker when its score exceeds threshold. Blacklisted addresses are loaded from and added to blacklist-file.
'';
};
blocktime = mkOption {
default = 120;
type = types.int;
description = ''
Block attackers for initially blocktime seconds after exceeding threshold. Subsequent blocks increase by a factor of 1.5.
sshguard unblocks attacks at random intervals, so actual block times will be longer.
'';
};
detection_time = mkOption {
default = 1800;
type = types.int;
description = ''
Remember potential attackers for up to detection_time seconds before resetting their score.
'';
};
whitelist = mkOption {
default = [ ];
example = [ "198.51.100.56" "198.51.100.2" ];
type = types.listOf types.str;
description = ''
Whitelist a list of addresses, hostnames, or address blocks.
'';
};
services = mkOption {
default = [ "sshd" ];
example = [ "sshd" "exim" ];
type = types.listOf types.str;
description = ''
Systemd services sshguard should receive logs of.
'';
};
};
};
###### implementation
config = mkIf cfg.enable {
environment.etc."sshguard.conf".text = let
args = lib.concatStringsSep " " ([
"-afb"
"-p info"
"-o cat"
"-n1"
] ++ (map (name: "-t ${escapeShellArg name}") cfg.services));
backend = if config.networking.nftables.enable
then "sshg-fw-nft-sets"
else "sshg-fw-ipset";
in ''
BACKEND="${pkgs.sshguard}/libexec/${backend}"
LOGREADER="LANG=C ${pkgs.systemd}/bin/journalctl ${args}"
'';
systemd.services.sshguard = {
description = "SSHGuard brute-force attacks protection system";
wantedBy = [ "multi-user.target" ];
after = [ "network.target" ];
partOf = optional config.networking.firewall.enable "firewall.service";
path = with pkgs; if config.networking.nftables.enable
then [ nftables iproute systemd ]
else [ iptables ipset iproute systemd ];
# The sshguard ipsets must exist before we invoke
# iptables. sshguard creates the ipsets after startup if
# necessary, but if we let sshguard do it, we can't reliably add
# the iptables rules because postStart races with the creation
# of the ipsets. So instead, we create both the ipsets and
# firewall rules before sshguard starts.
preStart = optionalString config.networking.firewall.enable ''
${pkgs.ipset}/bin/ipset -quiet create -exist sshguard4 hash:net family inet
${pkgs.ipset}/bin/ipset -quiet create -exist sshguard6 hash:net family inet6
${pkgs.iptables}/bin/iptables -I INPUT -m set --match-set sshguard4 src -j DROP
${pkgs.iptables}/bin/ip6tables -I INPUT -m set --match-set sshguard6 src -j DROP
'';
postStop = optionalString config.networking.firewall.enable ''
${pkgs.iptables}/bin/iptables -D INPUT -m set --match-set sshguard4 src -j DROP
${pkgs.iptables}/bin/ip6tables -D INPUT -m set --match-set sshguard6 src -j DROP
${pkgs.ipset}/bin/ipset -quiet destroy sshguard4
${pkgs.ipset}/bin/ipset -quiet destroy sshguard6
'';
unitConfig.Documentation = "man:sshguard(8)";
serviceConfig = {
Type = "simple";
ExecStart = let
args = lib.concatStringsSep " " ([
"-a ${toString cfg.attack_threshold}"
"-p ${toString cfg.blocktime}"
"-s ${toString cfg.detection_time}"
(optionalString (cfg.blacklist_threshold != null) "-b ${toString cfg.blacklist_threshold}:${cfg.blacklist_file}")
] ++ (map (name: "-w ${escapeShellArg name}") cfg.whitelist));
in "${pkgs.sshguard}/bin/sshguard ${args}";
Restart = "always";
ProtectSystem = "strict";
ProtectHome = "tmpfs";
RuntimeDirectory = "sshguard";
StateDirectory = "sshguard";
CapabilityBoundingSet = "CAP_NET_ADMIN CAP_NET_RAW";
};
};
};
}