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|
{ 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";
};
};
};
}
|