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nixpkgs/nixos/modules/config/sysctl.nix

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{ config, lib, ... }:
with lib;
let
sysctlOption = mkOptionType {
name = "sysctl option value";
check = val:
let
checkType = x: isBool x || isString x || isInt x || x == null;
in
checkType val || (val._type or "" == "override" && checkType val.content);
merge = loc: defs: mergeOneOption loc (filterOverrides defs);
};
in
{
options = {
boot.kernel.sysctl = mkOption {
default = {};
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example = literalExample ''
{ "net.ipv4.tcp_syncookies" = false; "vm.swappiness" = 60; }
'';
type = types.attrsOf sysctlOption;
description = ''
Runtime parameters of the Linux kernel, as set by
<citerefentry><refentrytitle>sysctl</refentrytitle>
<manvolnum>8</manvolnum></citerefentry>. Note that sysctl
parameters names must be enclosed in quotes
(e.g. <literal>"vm.swappiness"</literal> instead of
nixos: add grsecurity module (#1875) This module implements a significant refactoring in grsecurity configuration for NixOS, making it far more usable by default and much easier to configure. - New security.grsecurity NixOS attributes. - All grsec kernels supported - Allows default 'auto' grsec configuration, or custom config - Supports custom kernel options through kernelExtraConfig - Defaults to high-security - user must choose kernel, server/desktop mode, and any virtualisation software. That's all. - kptr_restrict is fixed under grsecurity (it's unwriteable) - grsecurity patch creation is now significantly abstracted - only need revision, version, and SHA1 - kernel version requirements are asserted for sanity - built kernels can have the uname specify the exact grsec version for development or bug reports. Off by default (requires `security.grsecurity.config.verboseVersion = true;`) - grsecurity sysctl support - By default, disabled. - For people who enable it, NixOS deploys a 'grsec-lock' systemd service which runs at startup. You are expected to configure sysctl through NixOS like you regularly would, which will occur before the service is started. As a result, changing sysctl settings requires a reboot. - New default group: 'grsecurity' - Root is a member by default - GRKERNSEC_PROC_GID is implicitly set to the 'grsecurity' GID, making it possible to easily add users to this group for /proc access - AppArmor is now automatically enabled where it wasn't before, despite implying features.apparmor = true The most trivial example of enabling grsecurity in your kernel is by specifying: security.grsecurity.enable = true; security.grsecurity.testing = true; # testing 3.13 kernel security.grsecurity.config.system = "desktop"; # or "server" This specifies absolutely no virtualisation support. In general, you probably at least want KVM host support, which is a little more work. So: security.grsecurity.enable = true; security.grsecurity.stable = true; # enable stable 3.2 kernel security.grsecurity.config = { system = "server"; priority = "security"; virtualisationConfig = "host"; virtualisationSoftware = "kvm"; hardwareVirtualisation = true; } This module has primarily been tested on Hetzner EX40 & VQ7 servers using NixOps. Signed-off-by: Austin Seipp <aseipp@pobox.com>
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<literal>vm.swappiness</literal>). The value of each
parameter may be a string, integer, boolean, or null
(signifying the option will not appear at all).
'';
};
};
config = {
environment.etc."sysctl.d/60-nixos.conf".text =
nixos: add grsecurity module (#1875) This module implements a significant refactoring in grsecurity configuration for NixOS, making it far more usable by default and much easier to configure. - New security.grsecurity NixOS attributes. - All grsec kernels supported - Allows default 'auto' grsec configuration, or custom config - Supports custom kernel options through kernelExtraConfig - Defaults to high-security - user must choose kernel, server/desktop mode, and any virtualisation software. That's all. - kptr_restrict is fixed under grsecurity (it's unwriteable) - grsecurity patch creation is now significantly abstracted - only need revision, version, and SHA1 - kernel version requirements are asserted for sanity - built kernels can have the uname specify the exact grsec version for development or bug reports. Off by default (requires `security.grsecurity.config.verboseVersion = true;`) - grsecurity sysctl support - By default, disabled. - For people who enable it, NixOS deploys a 'grsec-lock' systemd service which runs at startup. You are expected to configure sysctl through NixOS like you regularly would, which will occur before the service is started. As a result, changing sysctl settings requires a reboot. - New default group: 'grsecurity' - Root is a member by default - GRKERNSEC_PROC_GID is implicitly set to the 'grsecurity' GID, making it possible to easily add users to this group for /proc access - AppArmor is now automatically enabled where it wasn't before, despite implying features.apparmor = true The most trivial example of enabling grsecurity in your kernel is by specifying: security.grsecurity.enable = true; security.grsecurity.testing = true; # testing 3.13 kernel security.grsecurity.config.system = "desktop"; # or "server" This specifies absolutely no virtualisation support. In general, you probably at least want KVM host support, which is a little more work. So: security.grsecurity.enable = true; security.grsecurity.stable = true; # enable stable 3.2 kernel security.grsecurity.config = { system = "server"; priority = "security"; virtualisationConfig = "host"; virtualisationSoftware = "kvm"; hardwareVirtualisation = true; } This module has primarily been tested on Hetzner EX40 & VQ7 servers using NixOps. Signed-off-by: Austin Seipp <aseipp@pobox.com>
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concatStrings (mapAttrsToList (n: v:
optionalString (v != null) "${n}=${if v == false then "0" else toString v}\n"
) config.boot.kernel.sysctl);
systemd.services.systemd-sysctl =
{ wantedBy = [ "multi-user.target" ];
restartTriggers = [ config.environment.etc."sysctl.d/60-nixos.conf".source ];
};
# Enable hardlink and symlink restrictions. See
# https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=800179c9b8a1e796e441674776d11cd4c05d61d7
# for details.
boot.kernel.sysctl."fs.protected_hardlinks" = true;
boot.kernel.sysctl."fs.protected_symlinks" = true;
# Hide kernel pointers (e.g. in /proc/modules) for unprivileged
# users as these make it easier to exploit kernel vulnerabilities.
boot.kernel.sysctl."kernel.kptr_restrict" = 1;
# Disable YAMA by default to allow easy debugging.
boot.kernel.sysctl."kernel.yama.ptrace_scope" = mkDefault 0;
};
}