nixpkgs/nixos/modules/config/nsswitch.nix
Florian Klink c1536f5c78 nixos/systemd: fix NSS database ordering
- The order of NSS (host) modules has been brought in line with upstream
  recommendations:

  - The `myhostname` module is placed before the `resolve` (optional) and `dns`
    entries, but after `file` (to allow overriding via `/etc/hosts` /
    `networking.extraHosts`, and prevent ISPs with catchall-DNS resolvers from
    hijacking `.localhost` domains)
  - The `mymachines` module, which provides hostname resolution for local
    containers (registered with `systemd-machined`) is placed to the front, to
    make sure its mappings are preferred over other resolvers.
  - If systemd-networkd is enabled, the `resolve` module is placed before
    `files` and `myhostname`, as it provides the same logic internally, with
    caching.
  - The `mdns(_minimal)` module has been updated to the new priorities.

  If you use your own NSS host modules, make sure to update your priorities
  according to these rules:

  - NSS modules which should be queried before `resolved` DNS resolution should
    use mkBefore.
  - NSS modules which should be queried after `resolved`, `files` and
    `myhostname`, but before `dns` should use the default priority
  - NSS modules which should come after `dns` should use mkAfter.
2021-07-17 23:55:35 +02:00

134 lines
3.9 KiB
Nix

# Configuration for the Name Service Switch (/etc/nsswitch.conf).
{ config, lib, pkgs, ... }:
with lib;
{
options = {
# NSS modules. Hacky!
# Only works with nscd!
system.nssModules = mkOption {
type = types.listOf types.path;
internal = true;
default = [];
description = ''
Search path for NSS (Name Service Switch) modules. This allows
several DNS resolution methods to be specified via
<filename>/etc/nsswitch.conf</filename>.
'';
apply = list:
{
inherit list;
path = makeLibraryPath list;
};
};
system.nssDatabases = {
passwd = mkOption {
type = types.listOf types.str;
description = ''
List of passwd entries to configure in <filename>/etc/nsswitch.conf</filename>.
Note that "files" is always prepended while "systemd" is appended if nscd is enabled.
This option only takes effect if nscd is enabled.
'';
default = [];
};
group = mkOption {
type = types.listOf types.str;
description = ''
List of group entries to configure in <filename>/etc/nsswitch.conf</filename>.
Note that "files" is always prepended while "systemd" is appended if nscd is enabled.
This option only takes effect if nscd is enabled.
'';
default = [];
};
shadow = mkOption {
type = types.listOf types.str;
description = ''
List of shadow entries to configure in <filename>/etc/nsswitch.conf</filename>.
Note that "files" is always prepended.
This option only takes effect if nscd is enabled.
'';
default = [];
};
hosts = mkOption {
type = types.listOf types.str;
description = ''
List of hosts entries to configure in <filename>/etc/nsswitch.conf</filename>.
Note that "files" is always prepended, and "dns" and "myhostname" are always appended.
This option only takes effect if nscd is enabled.
'';
default = [];
};
services = mkOption {
type = types.listOf types.str;
description = ''
List of services entries to configure in <filename>/etc/nsswitch.conf</filename>.
Note that "files" is always prepended.
This option only takes effect if nscd is enabled.
'';
default = [];
};
};
};
imports = [
(mkRenamedOptionModule [ "system" "nssHosts" ] [ "system" "nssDatabases" "hosts" ])
];
config = {
assertions = [
{
# Prevent users from disabling nscd, with nssModules being set.
# If disabling nscd is really necessary, it's still possible to opt out
# by forcing config.system.nssModules to [].
assertion = config.system.nssModules.path != "" -> config.services.nscd.enable;
message = "Loading NSS modules from system.nssModules (${config.system.nssModules.path}), requires services.nscd.enable being set to true.";
}
];
# Name Service Switch configuration file. Required by the C
# library.
environment.etc."nsswitch.conf".text = ''
passwd: ${concatStringsSep " " config.system.nssDatabases.passwd}
group: ${concatStringsSep " " config.system.nssDatabases.group}
shadow: ${concatStringsSep " " config.system.nssDatabases.shadow}
hosts: ${concatStringsSep " " config.system.nssDatabases.hosts}
networks: files
ethers: files
services: ${concatStringsSep " " config.system.nssDatabases.services}
protocols: files
rpc: files
'';
system.nssDatabases = {
passwd = mkBefore [ "files" ];
group = mkBefore [ "files" ];
shadow = mkBefore [ "files" ];
hosts = mkMerge [
(mkOrder 998 [ "files" ])
(mkOrder 1499 [ "dns" ])
];
services = mkBefore [ "files" ];
};
};
}