diff options
Diffstat (limited to 'nixos/modules/system/boot/resolved.nix')
| -rw-r--r-- | nixos/modules/system/boot/resolved.nix | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/nixos/modules/system/boot/resolved.nix b/nixos/modules/system/boot/resolved.nix new file mode 100644 index 00000000000..21d3fab2f35 --- /dev/null +++ b/nixos/modules/system/boot/resolved.nix @@ -0,0 +1,183 @@ +{ config, lib, ... }: + +with lib; +let + cfg = config.services.resolved; + + dnsmasqResolve = config.services.dnsmasq.enable && + config.services.dnsmasq.resolveLocalQueries; + +in +{ + + options = { + + services.resolved.enable = mkOption { + default = false; + type = types.bool; + description = '' + Whether to enable the systemd DNS resolver daemon. + ''; + }; + + services.resolved.fallbackDns = mkOption { + default = [ ]; + example = [ "8.8.8.8" "2001:4860:4860::8844" ]; + type = types.listOf types.str; + description = '' + A list of IPv4 and IPv6 addresses to use as the fallback DNS servers. + If this option is empty, a compiled-in list of DNS servers is used instead. + ''; + }; + + services.resolved.domains = mkOption { + default = config.networking.search; + defaultText = literalExpression "config.networking.search"; + example = [ "example.com" ]; + type = types.listOf types.str; + description = '' + A list of domains. These domains are used as search suffixes + when resolving single-label host names (domain names which + contain no dot), in order to qualify them into fully-qualified + domain names (FQDNs). + + For compatibility reasons, if this setting is not specified, + the search domains listed in + <filename>/etc/resolv.conf</filename> are used instead, if + that file exists and any domains are configured in it. + ''; + }; + + services.resolved.llmnr = mkOption { + default = "true"; + example = "false"; + type = types.enum [ "true" "resolve" "false" ]; + description = '' + Controls Link-Local Multicast Name Resolution support + (RFC 4795) on the local host. + + If set to + + <variablelist> + <varlistentry> + <term><literal>"true"</literal></term> + <listitem><para> + Enables full LLMNR responder and resolver support. + </para></listitem> + </varlistentry> + <varlistentry> + <term><literal>"false"</literal></term> + <listitem><para> + Disables both. + </para></listitem> + </varlistentry> + <varlistentry> + <term><literal>"resolve"</literal></term> + <listitem><para> + Only resolution support is enabled, but responding is disabled. + </para></listitem> + </varlistentry> + </variablelist> + ''; + }; + + services.resolved.dnssec = mkOption { + default = "allow-downgrade"; + example = "true"; + type = types.enum [ "true" "allow-downgrade" "false" ]; + description = '' + If set to + <variablelist> + <varlistentry> + <term><literal>"true"</literal></term> + <listitem><para> + all DNS lookups are DNSSEC-validated locally (excluding + LLMNR and Multicast DNS). Note that this mode requires a + DNS server that supports DNSSEC. If the DNS server does + not properly support DNSSEC all validations will fail. + </para></listitem> + </varlistentry> + <varlistentry> + <term><literal>"allow-downgrade"</literal></term> + <listitem><para> + DNSSEC validation is attempted, but if the server does not + support DNSSEC properly, DNSSEC mode is automatically + disabled. Note that this mode makes DNSSEC validation + vulnerable to "downgrade" attacks, where an attacker might + be able to trigger a downgrade to non-DNSSEC mode by + synthesizing a DNS response that suggests DNSSEC was not + supported. + </para></listitem> + </varlistentry> + <varlistentry> + <term><literal>"false"</literal></term> + <listitem><para> + DNS lookups are not DNSSEC validated. + </para></listitem> + </varlistentry> + </variablelist> + ''; + }; + + services.resolved.extraConfig = mkOption { + default = ""; + type = types.lines; + description = '' + Extra config to append to resolved.conf. + ''; + }; + + }; + + config = mkIf cfg.enable { + + assertions = [ + { assertion = !config.networking.useHostResolvConf; + message = "Using host resolv.conf is not supported with systemd-resolved"; + } + ]; + + users.users.systemd-resolve.group = "systemd-resolve"; + + # add resolve to nss hosts database if enabled and nscd enabled + # system.nssModules is configured in nixos/modules/system/boot/systemd.nix + # added with order 501 to allow modules to go before with mkBefore + system.nssDatabases.hosts = (mkOrder 501 ["resolve [!UNAVAIL=return]"]); + + systemd.additionalUpstreamSystemUnits = [ + "systemd-resolved.service" + ]; + + systemd.services.systemd-resolved = { + wantedBy = [ "multi-user.target" ]; + aliases = [ "dbus-org.freedesktop.resolve1.service" ]; + restartTriggers = [ config.environment.etc."systemd/resolved.conf".source ]; + }; + + environment.etc = { + "systemd/resolved.conf".text = '' + [Resolve] + ${optionalString (config.networking.nameservers != []) + "DNS=${concatStringsSep " " config.networking.nameservers}"} + ${optionalString (cfg.fallbackDns != []) + "FallbackDNS=${concatStringsSep " " cfg.fallbackDns}"} + ${optionalString (cfg.domains != []) + "Domains=${concatStringsSep " " cfg.domains}"} + LLMNR=${cfg.llmnr} + DNSSEC=${cfg.dnssec} + ${config.services.resolved.extraConfig} + ''; + + # symlink the dynamic stub resolver of resolv.conf as recommended by upstream: + # https://www.freedesktop.org/software/systemd/man/systemd-resolved.html#/etc/resolv.conf + "resolv.conf".source = "/run/systemd/resolve/stub-resolv.conf"; + } // optionalAttrs dnsmasqResolve { + "dnsmasq-resolv.conf".source = "/run/systemd/resolve/resolv.conf"; + }; + + # If networkmanager is enabled, ask it to interface with resolved. + networking.networkmanager.dns = "systemd-resolved"; + + }; + +} |