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|
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.security.rngd;
in
{
options = {
security.rngd = {
enable = mkOption {
type = types.bool;
default = true;
description = ''
Whether to enable the rng daemon, which adds entropy from
hardware sources of randomness to the kernel entropy pool when
available.
'';
};
debug = mkOption {
type = types.bool;
default = false;
description = "Whether to enable debug output (-d).";
};
};
};
config = mkIf cfg.enable {
services.udev.extraRules = ''
KERNEL=="random", TAG+="systemd"
SUBSYSTEM=="cpu", ENV{MODALIAS}=="cpu:type:x86,*feature:*009E*", TAG+="systemd", ENV{SYSTEMD_WANTS}+="rngd.service"
KERNEL=="hw_random", TAG+="systemd", ENV{SYSTEMD_WANTS}+="rngd.service"
'';
systemd.services.rngd = {
bindsTo = [ "dev-random.device" ];
after = [ "dev-random.device" ];
# Clean shutdown without DefaultDependencies
conflicts = [ "shutdown.target" ];
before = [
"sysinit.target"
"shutdown.target"
];
description = "Hardware RNG Entropy Gatherer Daemon";
# rngd may have to start early to avoid entropy starvation during boot with encrypted swap
unitConfig.DefaultDependencies = false;
serviceConfig = {
ExecStart = "${pkgs.rng-tools}/sbin/rngd -f"
+ optionalString cfg.debug " -d";
# PrivateTmp would introduce a circular dependency if /tmp is on tmpfs and swap is encrypted,
# thus depending on rngd before swap, while swap depends on rngd to avoid entropy starvation.
NoNewPrivileges = true;
PrivateNetwork = true;
ProtectSystem = "full";
ProtectHome = true;
};
};
};
}
|