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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;
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;
}
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