nixpkgs/nixos/modules/security/hidepid.nix
Joachim Fasting cef2814a4f nixos: add optional process information hiding
This module adds an option `security.hideProcessInformation` that, when
enabled, restricts access to process information such as command-line
arguments to the process owner.  The module adds a static group "proc"
whose members are exempt from process information hiding.

Ideally, this feature would be implemented by simply adding the
appropriate mount options to `fileSystems."/proc".fsOptions`, but this
was found to not work in vmtests. To ensure that process information
hiding is enforced, we use a systemd service unit that remounts `/proc`
after `systemd-remount-fs.service` has completed.

To verify the correctness of the feature, simple tests were added to
nixos/tests/misc: the test ensures that unprivileged users cannot see
process information owned by another user, while members of "proc" CAN.

Thanks to @abbradar for feedback and suggestions.
2016-04-10 12:27:06 +02:00

43 lines
1.5 KiB
Nix

{ config, pkgs, lib, ... }:
with lib;
{
options = {
security.hideProcessInformation = mkEnableOption "" // { description = ''
Restrict access to process information to the owning user. Enabling
this option implies, among other things, that command-line arguments
remain private. This option is recommended for most systems, unless
there's a legitimate reason for allowing unprivileged users to inspect
the process information of other users.
Members of the group "proc" are exempt from process information hiding.
To allow a service to run without process information hiding, add "proc"
to its supplementary groups via
<option>systemd.services.&lt;name?&gt;.serviceConfig.SupplementaryGroups</option>.
''; };
};
config = mkIf config.security.hideProcessInformation {
users.groups.proc.gid = config.ids.gids.proc;
systemd.services.hidepid = {
wantedBy = [ "local-fs.target" ];
after = [ "systemd-remount-fs.service" ];
before = [ "local-fs-pre.target" "local-fs.target" "shutdown.target" ];
wants = [ "local-fs-pre.target" ];
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
ExecStart = ''${pkgs.utillinux}/bin/mount -o remount,hidepid=2,gid=${toString config.ids.gids.proc} /proc'';
ExecStop = ''${pkgs.utillinux}/bin/mount -o remount,hidepid=0,gid=0 /proc'';
};
unitConfig = {
DefaultDependencies = false;
Conflicts = "shutdown.target";
};
};
};
}