{ config, lib, pkgs, ... }: with lib; let cfg = config.services.sslh; user = "sslh"; configFile = pkgs.writeText "sslh.conf" '' verbose: ${boolToString cfg.verbose}; foreground: true; inetd: false; numeric: false; transparent: ${boolToString cfg.transparent}; timeout: "${toString cfg.timeout}"; listen: ( { host: "${cfg.listenAddress}"; port: "${toString cfg.port}"; } ); ${cfg.appendConfig} ''; defaultAppendConfig = '' protocols: ( { name: "ssh"; service: "ssh"; host: "localhost"; port: "22"; probe: "builtin"; }, { name: "openvpn"; host: "localhost"; port: "1194"; probe: "builtin"; }, { name: "xmpp"; host: "localhost"; port: "5222"; probe: "builtin"; }, { name: "http"; host: "localhost"; port: "80"; probe: "builtin"; }, { name: "ssl"; host: "localhost"; port: "443"; probe: "builtin"; }, { name: "anyprot"; host: "localhost"; port: "443"; probe: "builtin"; } ); ''; in { options = { services.sslh = { enable = mkEnableOption "sslh"; verbose = mkOption { type = types.bool; default = false; description = "Verbose logs."; }; timeout = mkOption { type = types.int; default = 2; description = "Timeout in seconds."; }; transparent = mkOption { type = types.bool; default = false; description = "Will the services behind sslh (Apache, sshd and so on) see the external IP and ports as if the external world connected directly to them"; }; listenAddress = mkOption { type = types.str; default = "0.0.0.0"; description = "Listening address or hostname."; }; port = mkOption { type = types.int; default = 443; description = "Listening port."; }; appendConfig = mkOption { type = types.str; default = defaultAppendConfig; description = "Verbatim configuration file."; }; }; }; config = mkMerge [ (mkIf cfg.enable { users.users.${user} = { description = "sslh daemon user"; isSystemUser = true; }; systemd.services.sslh = { description = "Applicative Protocol Multiplexer (e.g. share SSH and HTTPS on the same port)"; after = [ "network.target" ]; wantedBy = [ "multi-user.target" ]; serviceConfig = { User = user; Group = "nogroup"; PermissionsStartOnly = true; Restart = "always"; RestartSec = "1s"; ExecStart = "${pkgs.sslh}/bin/sslh -F${configFile}"; KillMode = "process"; AmbientCapabilities = "CAP_NET_BIND_SERVICE CAP_NET_ADMIN CAP_SETGID CAP_SETUID"; PrivateTmp = true; PrivateDevices = true; ProtectSystem = "full"; ProtectHome = true; }; }; }) # code from https://github.com/yrutschle/sslh#transparent-proxy-support # the only difference is using iptables mark 0x2 instead of 0x1 to avoid conflicts with nixos/nat module (mkIf (cfg.enable && cfg.transparent) { # Set route_localnet = 1 on all interfaces so that ssl can use "localhost" as destination boot.kernel.sysctl."net.ipv4.conf.default.route_localnet" = 1; boot.kernel.sysctl."net.ipv4.conf.all.route_localnet" = 1; systemd.services.sslh = let iptablesCommands = [ # DROP martian packets as they would have been if route_localnet was zero # Note: packets not leaving the server aren't affected by this, thus sslh will still work { table = "raw"; command = "PREROUTING ! -i lo -d 127.0.0.0/8 -j DROP"; } { table = "mangle"; command = "POSTROUTING ! -o lo -s 127.0.0.0/8 -j DROP"; } # Mark all connections made by ssl for special treatment (here sslh is run as user ${user}) { table = "nat"; command = "OUTPUT -m owner --uid-owner ${user} -p tcp --tcp-flags FIN,SYN,RST,ACK SYN -j CONNMARK --set-xmark 0x02/0x0f"; } # Outgoing packets that should go to sslh instead have to be rerouted, so mark them accordingly (copying over the connection mark) { table = "mangle"; command = "OUTPUT ! -o lo -p tcp -m connmark --mark 0x02/0x0f -j CONNMARK --restore-mark --mask 0x0f"; } ]; ip6tablesCommands = [ { table = "raw"; command = "PREROUTING ! -i lo -d ::1/128 -j DROP"; } { table = "mangle"; command = "POSTROUTING ! -o lo -s ::1/128 -j DROP"; } { table = "nat"; command = "OUTPUT -m owner --uid-owner ${user} -p tcp --tcp-flags FIN,SYN,RST,ACK SYN -j CONNMARK --set-xmark 0x02/0x0f"; } { table = "mangle"; command = "OUTPUT ! -o lo -p tcp -m connmark --mark 0x02/0x0f -j CONNMARK --restore-mark --mask 0x0f"; } ]; in { path = [ pkgs.iptables pkgs.iproute pkgs.procps ]; preStart = '' # Cleanup old iptables entries which might be still there ${concatMapStringsSep "\n" ({table, command}: "while iptables -w -t ${table} -D ${command} 2>/dev/null; do echo; done") iptablesCommands} ${concatMapStringsSep "\n" ({table, command}: "iptables -w -t ${table} -A ${command}" ) iptablesCommands} # Configure routing for those marked packets ip rule add fwmark 0x2 lookup 100 ip route add local 0.0.0.0/0 dev lo table 100 '' + optionalString config.networking.enableIPv6 '' ${concatMapStringsSep "\n" ({table, command}: "while ip6tables -w -t ${table} -D ${command} 2>/dev/null; do echo; done") ip6tablesCommands} ${concatMapStringsSep "\n" ({table, command}: "ip6tables -w -t ${table} -A ${command}" ) ip6tablesCommands} ip -6 rule add fwmark 0x2 lookup 100 ip -6 route add local ::/0 dev lo table 100 ''; postStop = '' ${concatMapStringsSep "\n" ({table, command}: "iptables -w -t ${table} -D ${command}") iptablesCommands} ip rule del fwmark 0x2 lookup 100 ip route del local 0.0.0.0/0 dev lo table 100 '' + optionalString config.networking.enableIPv6 '' ${concatMapStringsSep "\n" ({table, command}: "ip6tables -w -t ${table} -D ${command}") ip6tablesCommands} ip -6 rule del fwmark 0x2 lookup 100 ip -6 route del local ::/0 dev lo table 100 ''; }; }) ]; }