nixpkgs/nixos/modules/profiles/hardened.nix

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# A profile with most (vanilla) hardening options enabled by default,
# potentially at the cost of stability, features and performance.
#
# This profile enables options that are known to affect system
# stability. If you experience any stability issues when using the
# profile, try disabling it. If you report an issue and use this
# profile, always mention that you do.
{ config, lib, pkgs, ... }:
with lib;
{
meta = {
maintainers = [ maintainers.joachifm maintainers.emily ];
};
boot.kernelPackages = mkDefault pkgs.linuxPackages_hardened;
nixos/nix-daemon: use structural settings The `nix.*` options, apart from options for setting up the daemon itself, currently provide a lot of setting mappings for the Nix daemon configuration. The scope of the mapping yields convience, but the line where an option is considered essential is blurry. For instance, the `extra-sandbox-paths` mapping is provided without its primary consumer, and the corresponding `sandbox-paths` option is also not mapped. The current system increases the maintenance burden as maintainers have to closely follow upstream changes. In this case, there are two state versions of Nix which have to be maintained collectively, with different options avaliable. This commit aims to following the standard outlined in RFC 42[1] to implement a structural setting pattern. The Nix configuration is encoded at its core as key-value pairs which maps nicely to attribute sets, making it feasible to express in the Nix language itself. Some existing options are kept such as `buildMachines` and `registry` which present a simplified interface to managing the respective settings. The interface is exposed as `nix.settings`. Legacy configurations are mapped to their corresponding options under `nix.settings` for backwards compatibility. Various options settings in other nixos modules and relevant tests have been updated to use structural setting for consistency. The generation and validation of the configration file has been modified to use `writeTextFile` instead of `runCommand` for clarity. Note that validation is now mandatory as strict checking of options has been pushed down to the derivation level due to freeformType consuming unmatched options. Furthermore, validation can not occur when cross-compiling due to current limitations. A new option `publicHostKey` was added to the `buildMachines` submodule corresponding to the base64 encoded public host key settings exposed in the builder syntax. The build machine generation was subsequently rewritten to use `concatStringsSep` for better performance by grouping concatenations. [1] - https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md
2021-11-19 23:36:26 +01:00
nix.settings.allowed-users = mkDefault [ "@users" ];
environment.memoryAllocator.provider = mkDefault "scudo";
environment.variables.SCUDO_OPTIONS = mkDefault "ZeroContents=1";
security.lockKernelModules = mkDefault true;
security.protectKernelImage = mkDefault true;
security.allowSimultaneousMultithreading = mkDefault false;
security.forcePageTableIsolation = mkDefault true;
# This is required by podman to run containers in rootless mode.
security.unprivilegedUsernsClone = mkDefault config.virtualisation.containers.enable;
security.virtualisation.flushL1DataCache = mkDefault "always";
security.apparmor.enable = mkDefault true;
security.apparmor.killUnconfinedConfinables = mkDefault true;
boot.kernelParams = [
# Slab/slub sanity checks, redzoning, and poisoning
"slub_debug=FZP"
# Overwrite free'd memory
"page_poison=1"
# Enable page allocator randomization
"page_alloc.shuffle=1"
];
boot.blacklistedKernelModules = [
# Obscure network protocols
"ax25"
"netrom"
"rose"
# Old or rare or insufficiently audited filesystems
"adfs"
"affs"
"bfs"
"befs"
"cramfs"
"efs"
"erofs"
"exofs"
"freevxfs"
"f2fs"
"hfs"
"hpfs"
"jfs"
"minix"
"nilfs2"
"ntfs"
"omfs"
"qnx4"
"qnx6"
"sysv"
"ufs"
];
# Restrict ptrace() usage to processes with a pre-defined relationship
# (e.g., parent/child)
boot.kernel.sysctl."kernel.yama.ptrace_scope" = mkOverride 500 1;
# Hide kptrs even for processes with CAP_SYSLOG
boot.kernel.sysctl."kernel.kptr_restrict" = mkOverride 500 2;
# Disable bpf() JIT (to eliminate spray attacks)
boot.kernel.sysctl."net.core.bpf_jit_enable" = mkDefault false;
# Disable ftrace debugging
boot.kernel.sysctl."kernel.ftrace_enabled" = mkDefault false;
# Enable strict reverse path filtering (that is, do not attempt to route
# packets that "obviously" do not belong to the iface's network; dropped
# packets are logged as martians).
boot.kernel.sysctl."net.ipv4.conf.all.log_martians" = mkDefault true;
boot.kernel.sysctl."net.ipv4.conf.all.rp_filter" = mkDefault "1";
boot.kernel.sysctl."net.ipv4.conf.default.log_martians" = mkDefault true;
boot.kernel.sysctl."net.ipv4.conf.default.rp_filter" = mkDefault "1";
# Ignore broadcast ICMP (mitigate SMURF)
boot.kernel.sysctl."net.ipv4.icmp_echo_ignore_broadcasts" = mkDefault true;
# Ignore incoming ICMP redirects (note: default is needed to ensure that the
# setting is applied to interfaces added after the sysctls are set)
boot.kernel.sysctl."net.ipv4.conf.all.accept_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv4.conf.all.secure_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv4.conf.default.accept_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv4.conf.default.secure_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv6.conf.all.accept_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv6.conf.default.accept_redirects" = mkDefault false;
# Ignore outgoing ICMP redirects (this is ipv4 only)
boot.kernel.sysctl."net.ipv4.conf.all.send_redirects" = mkDefault false;
boot.kernel.sysctl."net.ipv4.conf.default.send_redirects" = mkDefault false;
}