nixpkgs/nixos/modules/services/networking/uptermd.nix
Jörg Thalheim eefafb54ef
nixos/upterm: additional hardening
Before:
$ ps aux | grep upterm
root     2575046  0.0  0.0 1085080 6968 ?        Ssl  07:03   0:00 /nix/store/ci97r1lqx4128w75k7dcsw82j5bl0n3g-upterm-0.8.2/bin/uptermd --ssh-addr [::]:2323 --private-key ssh_host_ed25519_key

After
$ ps aux | grep upterm
uptermd  2832993  0.4  0.0 1158812 6856 ?        Ssl  07:08   0:00 /nix/store/ci97r1lqx4128w75k7dcsw82j5bl0n3g-upterm-0.8.2/bin/uptermd --ssh-addr [::]:2323 --private-key ssh_host_ed25519_key
2022-05-15 09:57:52 +02:00

110 lines
3.0 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.uptermd;
in
{
options = {
services.uptermd = {
enable = mkEnableOption "uptermd";
openFirewall = mkOption {
type = types.bool;
default = false;
description = ''
Whether to open the firewall for the port in <option>services.uptermd.port</option>.
'';
};
port = mkOption {
type = types.port;
default = 2222;
description = ''
Port the server will listen on.
'';
};
listenAddress = mkOption {
type = types.str;
default = "[::]";
example = "127.0.0.1";
description = ''
Address the server will listen on.
'';
};
hostKey = mkOption {
type = types.nullOr types.path;
default = null;
example = "/run/keys/upterm_host_ed25519_key";
description = ''
Path to SSH host key. If not defined, an ed25519 keypair is generated automatically.
'';
};
extraFlags = mkOption {
type = types.listOf types.str;
default = [];
example = [ "--debug" ];
description = ''
Extra flags passed to the uptermd command.
'';
};
};
};
config = mkIf cfg.enable {
networking.firewall = mkIf cfg.openFirewall {
allowedTCPPorts = [ cfg.port ];
};
systemd.services.uptermd = {
description = "Upterm Daemon";
wantedBy = [ "multi-user.target" ];
after = [ "network.target" ];
path = [ pkgs.openssh ];
preStart = mkIf (cfg.hostKey == null) ''
if ! [ -f ssh_host_ed25519_key ]; then
ssh-keygen \
-t ed25519 \
-f ssh_host_ed25519_key \
-N ""
fi
'';
serviceConfig = {
StateDirectory = "uptermd";
WorkingDirectory = "/var/lib/uptermd";
ExecStart = "${pkgs.upterm}/bin/uptermd --ssh-addr ${cfg.listenAddress}:${toString cfg.port} --private-key ${if cfg.hostKey == null then "ssh_host_ed25519_key" else cfg.hostKey} ${concatStringsSep " " cfg.extraFlags}";
# Hardening
AmbientCapabilities = mkIf (cfg.port < 1024) [ "CAP_NET_BIND_SERVICE" ];
CapabilityBoundingSet = mkIf (cfg.port < 1024) [ "CAP_NET_BIND_SERVICE" ];
PrivateUsers = cfg.port >= 1024;
DynamicUser = true;
LockPersonality = true;
MemoryDenyWriteExecute = true;
PrivateDevices = true;
ProtectClock = true;
ProtectControlGroups = true;
ProtectHome = true;
ProtectHostname = true;
ProtectKernelLogs = true;
ProtectKernelModules = true;
ProtectKernelTunables = true;
ProtectProc = "invisible";
# AF_UNIX is for ssh-keygen, which relies on nscd to resolve the uid to a user
RestrictAddressFamilies = [ "AF_INET" "AF_INET6" "AF_UNIX" ];
RestrictNamespaces = true;
RestrictRealtime = true;
SystemCallArchitectures = "native";
SystemCallFilter = "@system-service";
};
};
};
}