nixpkgs/nixos/modules/services/networking/dnscrypt-wrapper.nix
2021-01-19 01:16:25 -08:00

285 lines
8.3 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.dnscrypt-wrapper;
dataDir = "/var/lib/dnscrypt-wrapper";
mkPath = path: default:
if path != null
then toString path
else default;
publicKey = mkPath cfg.providerKey.public "${dataDir}/public.key";
secretKey = mkPath cfg.providerKey.secret "${dataDir}/secret.key";
daemonArgs = with cfg; [
"--listen-address=${address}:${toString port}"
"--resolver-address=${upstream.address}:${toString upstream.port}"
"--provider-name=${providerName}"
"--provider-publickey-file=${publicKey}"
"--provider-secretkey-file=${secretKey}"
"--provider-cert-file=${providerName}.crt"
"--crypt-secretkey-file=${providerName}.key"
];
genKeys = ''
# generates time-limited keypairs
keyGen() {
dnscrypt-wrapper --gen-crypt-keypair \
--crypt-secretkey-file=${cfg.providerName}.key
dnscrypt-wrapper --gen-cert-file \
--crypt-secretkey-file=${cfg.providerName}.key \
--provider-cert-file=${cfg.providerName}.crt \
--provider-publickey-file=${publicKey} \
--provider-secretkey-file=${secretKey} \
--cert-file-expire-days=${toString cfg.keys.expiration}
}
cd ${dataDir}
# generate provider keypair (first run only)
${optionalString (cfg.providerKey.public == null || cfg.providerKey.secret == null) ''
if [ ! -f ${publicKey} ] || [ ! -f ${secretKey} ]; then
dnscrypt-wrapper --gen-provider-keypair
fi
''}
# generate new keys for rotation
if [ ! -f ${cfg.providerName}.key ] || [ ! -f ${cfg.providerName}.crt ]; then
keyGen
fi
'';
rotateKeys = ''
# check if keys are not expired
keyValid() {
fingerprint=$(dnscrypt-wrapper \
--show-provider-publickey \
--provider-publickey-file=${publicKey} \
| awk '{print $(NF)}')
dnscrypt-proxy --test=${toString (cfg.keys.checkInterval + 1)} \
--resolver-address=127.0.0.1:${toString cfg.port} \
--provider-name=${cfg.providerName} \
--provider-key=$fingerprint
}
cd ${dataDir}
# archive old keys and restart the service
if ! keyValid; then
echo "certificate soon to become invalid; backing up old cert"
mkdir -p oldkeys
mv -v ${cfg.providerName}.key oldkeys/${cfg.providerName}-$(date +%F-%T).key
mv -v ${cfg.providerName}.crt oldkeys/${cfg.providerName}-$(date +%F-%T).crt
systemctl restart dnscrypt-wrapper
fi
'';
# This is the fork of the original dnscrypt-proxy maintained by Dyne.org.
# dnscrypt-proxy2 doesn't provide the `--test` feature that is needed to
# correctly implement key rotation of dnscrypt-wrapper ephemeral keys.
dnscrypt-proxy1 = pkgs.callPackage
({ stdenv, fetchFromGitHub, autoreconfHook
, pkg-config, libsodium, ldns, openssl, systemd }:
stdenv.mkDerivation rec {
pname = "dnscrypt-proxy";
version = "2019-08-20";
src = fetchFromGitHub {
owner = "dyne";
repo = "dnscrypt-proxy";
rev = "07ac3825b5069adc28e2547c16b1d983a8ed8d80";
sha256 = "0c4mq741q4rpmdn09agwmxap32kf0vgfz7pkhcdc5h54chc3g3xy";
};
configureFlags = optional stdenv.isLinux "--with-systemd";
nativeBuildInputs = [ autoreconfHook pkg-config ];
# <ldns/ldns.h> depends on <openssl/ssl.h>
buildInputs = [ libsodium openssl.dev ldns ] ++ optional stdenv.isLinux systemd;
postInstall = ''
# Previous versions required libtool files to load plugins; they are
# now strictly optional.
rm $out/lib/dnscrypt-proxy/*.la
'';
meta = {
description = "A tool for securing communications between a client and a DNS resolver";
homepage = "https://github.com/dyne/dnscrypt-proxy";
license = licenses.isc;
maintainers = with maintainers; [ rnhmjoj ];
platforms = platforms.linux;
};
}) { };
in {
###### interface
options.services.dnscrypt-wrapper = {
enable = mkEnableOption "DNSCrypt wrapper";
address = mkOption {
type = types.str;
default = "127.0.0.1";
description = ''
The DNSCrypt wrapper will bind to this IP address.
'';
};
port = mkOption {
type = types.int;
default = 5353;
description = ''
The DNSCrypt wrapper will listen for DNS queries on this port.
'';
};
providerName = mkOption {
type = types.str;
default = "2.dnscrypt-cert.${config.networking.hostName}";
example = "2.dnscrypt-cert.myresolver";
description = ''
The name that will be given to this DNSCrypt resolver.
Note: the resolver name must start with <literal>2.dnscrypt-cert.</literal>.
'';
};
providerKey.public = mkOption {
type = types.nullOr types.path;
default = null;
example = "/etc/secrets/public.key";
description = ''
The filepath to the provider public key. If not given a new
provider key pair will be generated on the first run.
'';
};
providerKey.secret = mkOption {
type = types.nullOr types.path;
default = null;
example = "/etc/secrets/secret.key";
description = ''
The filepath to the provider secret key. If not given a new
provider key pair will be generated on the first run.
'';
};
upstream.address = mkOption {
type = types.str;
default = "127.0.0.1";
description = ''
The IP address of the upstream DNS server DNSCrypt will "wrap".
'';
};
upstream.port = mkOption {
type = types.int;
default = 53;
description = ''
The port of the upstream DNS server DNSCrypt will "wrap".
'';
};
keys.expiration = mkOption {
type = types.int;
default = 30;
description = ''
The duration (in days) of the time-limited secret key.
This will be automatically rotated before expiration.
'';
};
keys.checkInterval = mkOption {
type = types.int;
default = 1440;
description = ''
The time interval (in minutes) between key expiration checks.
'';
};
};
###### implementation
config = mkIf cfg.enable {
users.users.dnscrypt-wrapper = {
description = "dnscrypt-wrapper daemon user";
home = "${dataDir}";
createHome = true;
isSystemUser = true;
};
users.groups.dnscrypt-wrapper = { };
security.polkit.extraConfig = ''
// Allow dnscrypt-wrapper user to restart dnscrypt-wrapper.service
polkit.addRule(function(action, subject) {
if (action.id == "org.freedesktop.systemd1.manage-units" &&
action.lookup("unit") == "dnscrypt-wrapper.service" &&
subject.user == "dnscrypt-wrapper") {
return polkit.Result.YES;
}
});
'';
systemd.services.dnscrypt-wrapper = {
description = "dnscrypt-wrapper daemon";
after = [ "network.target" ];
wantedBy = [ "multi-user.target" ];
path = [ pkgs.dnscrypt-wrapper ];
serviceConfig = {
User = "dnscrypt-wrapper";
WorkingDirectory = dataDir;
Restart = "on-failure";
ExecStart = "${pkgs.dnscrypt-wrapper}/bin/dnscrypt-wrapper ${toString daemonArgs}";
};
preStart = genKeys;
};
systemd.services.dnscrypt-wrapper-rotate = {
after = [ "network.target" ];
requires = [ "dnscrypt-wrapper.service" ];
description = "Rotates DNSCrypt wrapper keys if soon to expire";
path = with pkgs; [ dnscrypt-wrapper dnscrypt-proxy1 gawk ];
script = rotateKeys;
serviceConfig.User = "dnscrypt-wrapper";
};
systemd.timers.dnscrypt-wrapper-rotate = {
description = "Periodically check DNSCrypt wrapper keys for expiration";
wantedBy = [ "multi-user.target" ];
timerConfig = {
Unit = "dnscrypt-wrapper-rotate.service";
OnBootSec = "1min";
OnUnitActiveSec = cfg.keys.checkInterval * 60;
};
};
assertions = with cfg; [
{ assertion = (providerKey.public == null && providerKey.secret == null) ||
(providerKey.secret != null && providerKey.public != null);
message = "The secret and public provider key must be set together.";
}
];
};
meta.maintainers = with lib.maintainers; [ rnhmjoj ];
}