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|
{ config, pkgs, lib, ... }:
with lib;
let
cfg = config.security.grsecurity;
grsecLockPath = "/proc/sys/kernel/grsecurity/grsec_lock";
# Ascertain whether NixOS container support is required
containerSupportRequired =
config.boot.enableContainers && config.containers != {};
in
{
meta = {
maintainers = with maintainers; [ joachifm ];
doc = ./grsecurity.xml;
};
options.security.grsecurity = {
enable = mkOption {
type = types.bool;
example = true;
default = false;
description = ''
Enable grsecurity/PaX.
'';
};
lockTunables = mkOption {
type = types.bool;
example = false;
default = true;
description = ''
Whether to automatically lock grsecurity tunables
(<option>boot.kernel.sysctl."kernel.grsecurity.*"</option>). Disable
this to allow runtime configuration of grsecurity features. Activate
the <literal>grsec-lock</literal> service unit to prevent further
configuration until the next reboot.
'';
};
disableEfiRuntimeServices = mkOption {
type = types.bool;
example = false;
default = true;
description = ''
Whether to disable access to EFI runtime services. Enabling EFI runtime
services creates a venue for code injection attacks on the kernel and
should be disabled if at all possible. Changing this option enters into
effect upon reboot.
'';
};
};
config = mkIf cfg.enable {
boot.kernelPackages = mkForce pkgs.linuxPackages_grsec_nixos;
boot.kernelParams = [ "grsec_sysfs_restrict=0" ]
++ optional cfg.disableEfiRuntimeServices "noefi";
nixpkgs.config.grsecurity = true;
# Install PaX related utillities into the system profile.
environment.systemPackages = with pkgs; [ gradm paxctl pax-utils ];
# Install rules for the grsec device node
services.udev.packages = [ pkgs.gradm ];
# This service unit is responsible for locking the grsecurity tunables. The
# unit is always defined, but only activated on bootup if lockTunables is
# toggled. When lockTunables is toggled, failure to activate the unit will
# enter emergency mode. The intent is to make it difficult to silently
# enter multi-user mode without having locked the tunables. Some effort is
# made to ensure that starting the unit is an idempotent operation.
systemd.services.grsec-lock = {
description = "Lock grsecurity tunables";
wantedBy = optional cfg.lockTunables "multi-user.target";
wants = [ "local-fs.target" "systemd-sysctl.service" ];
after = [ "local-fs.target" "systemd-sysctl.service" ];
conflicts = [ "shutdown.target" ];
restartIfChanged = false;
script = ''
if ${pkgs.gnugrep}/bin/grep -Fq 0 ${grsecLockPath} ; then
echo -n 1 > ${grsecLockPath}
fi
'';
unitConfig = {
ConditionPathIsReadWrite = grsecLockPath;
DefaultDependencies = false;
} // optionalAttrs cfg.lockTunables {
OnFailure = "emergency.target";
};
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
};
# Configure system tunables
boot.kernel.sysctl = {
# Read-only under grsecurity
"kernel.kptr_restrict" = mkForce null;
# All grsec tunables default to off, those not enabled below are
# *disabled*. We use mkDefault to allow expert users to override
# our choices, but use mkForce where tunables would outright
# conflict with other settings.
# Enable all chroot restrictions by default (overwritten as
# necessary below)
"kernel.grsecurity.chroot_caps" = mkDefault 1;
"kernel.grsecurity.chroot_deny_bad_rename" = mkDefault 1;
"kernel.grsecurity.chroot_deny_chmod" = mkDefault 1;
"kernel.grsecurity.chroot_deny_chroot" = mkDefault 1;
"kernel.grsecurity.chroot_deny_fchdir" = mkDefault 1;
"kernel.grsecurity.chroot_deny_mknod" = mkDefault 1;
"kernel.grsecurity.chroot_deny_mount" = mkDefault 1;
"kernel.grsecurity.chroot_deny_pivot" = mkDefault 1;
"kernel.grsecurity.chroot_deny_shmat" = mkDefault 1;
"kernel.grsecurity.chroot_deny_sysctl" = mkDefault 1;
"kernel.grsecurity.chroot_deny_unix" = mkDefault 1;
"kernel.grsecurity.chroot_enforce_chdir" = mkDefault 1;
"kernel.grsecurity.chroot_findtask" = mkDefault 1;
"kernel.grsecurity.chroot_restrict_nice" = mkDefault 1;
# Enable various grsec protections
"kernel.grsecurity.consistent_setxid" = mkDefault 1;
"kernel.grsecurity.deter_bruteforce" = mkDefault 1;
"kernel.grsecurity.fifo_restrictions" = mkDefault 1;
"kernel.grsecurity.harden_ipc" = mkDefault 1;
"kernel.grsecurity.harden_ptrace" = mkDefault 1;
"kernel.grsecurity.harden_tty" = mkDefault 1;
"kernel.grsecurity.ip_blackhole" = mkDefault 1;
"kernel.grsecurity.linking_restrictions" = mkDefault 1;
"kernel.grsecurity.ptrace_readexec" = mkDefault 1;
# Enable auditing
"kernel.grsecurity.audit_ptrace" = mkDefault 1;
"kernel.grsecurity.forkfail_logging" = mkDefault 1;
"kernel.grsecurity.rwxmap_logging" = mkDefault 1;
"kernel.grsecurity.signal_logging" = mkDefault 1;
"kernel.grsecurity.timechange_logging" = mkDefault 1;
} // optionalAttrs config.nix.useSandbox {
# chroot(2) restrictions that conflict with sandboxed Nix builds
"kernel.grsecurity.chroot_caps" = mkForce 0;
"kernel.grsecurity.chroot_deny_chmod" = mkForce 0;
"kernel.grsecurity.chroot_deny_chroot" = mkForce 0;
"kernel.grsecurity.chroot_deny_mount" = mkForce 0;
"kernel.grsecurity.chroot_deny_pivot" = mkForce 0;
} // optionalAttrs containerSupportRequired {
# chroot(2) restrictions that conflict with NixOS lightweight containers
"kernel.grsecurity.chroot_caps" = mkForce 0;
"kernel.grsecurity.chroot_deny_chmod" = mkForce 0;
"kernel.grsecurity.chroot_deny_mount" = mkForce 0;
"kernel.grsecurity.chroot_restrict_nice" = mkForce 0;
# Disable privileged IO by default, unless X is enabled
} // optionalAttrs (!config.services.xserver.enable) {
"kernel.grsecurity.disable_priv_io" = mkDefault 1;
};
};
}
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