b80c3284d5
Borrowing from here to match hardened profile with more recent kernels: * https://madaidans-insecurities.github.io/guides/linux-hardening.html?#boot-parameters * https://github.com/a13xp0p0v/kernel-hardening-checker/ Removed "slub_debug" as that option disables kernel memory address hashing. You also see a big warning about this in the dmesg: "This system shows unhashed kernel memory addresses via the console, logs, and other interfaces." "init_on_alloc=1" and "init_on_free=1" zeroes all SLAB and SLUB allocations. Introduced in 6471384af2a6530696fc0203bafe4de41a23c9ef. Also the default for the Android Google kernel btw. It is on by default through the KConfig. "slab_nomerge" prevents the merging of slab/slub caches. These are effectively slab/slub pools. "LEGACY_VSYSCALL_NONE" disables the older vsyscall mechanic that relies on static address. It got superseeded by vdsos a decade ago. Read some LWN.net to learn more ;) "debugfs=off" I'm sure there are some few userspace programs that rely on debugfs, but they shouldn't. Most other things mentioned on the blog where already the default on a running machine or may not be applicable. Most other Kconfigs changes come from the kernel hardening checker and were added, when they were not applied to the kernel already. Unsure about CONFIG_STATIC_USERMODEHELPER. Would need testing.
118 lines
3.6 KiB
Nix
118 lines
3.6 KiB
Nix
# A profile with most (vanilla) hardening options enabled by default,
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# potentially at the cost of stability, features and performance.
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#
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# This profile enables options that are known to affect system
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# stability. If you experience any stability issues when using the
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# profile, try disabling it. If you report an issue and use this
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# profile, always mention that you do.
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{ config, lib, pkgs, ... }:
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with lib;
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{
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meta = {
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maintainers = [ maintainers.joachifm maintainers.emily ];
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};
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boot.kernelPackages = mkDefault pkgs.linuxPackages_hardened;
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nix.settings.allowed-users = mkDefault [ "@users" ];
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environment.memoryAllocator.provider = mkDefault "scudo";
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environment.variables.SCUDO_OPTIONS = mkDefault "ZeroContents=1";
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security.lockKernelModules = mkDefault true;
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security.protectKernelImage = mkDefault true;
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security.allowSimultaneousMultithreading = mkDefault false;
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security.forcePageTableIsolation = mkDefault true;
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# This is required by podman to run containers in rootless mode.
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security.unprivilegedUsernsClone = mkDefault config.virtualisation.containers.enable;
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security.virtualisation.flushL1DataCache = mkDefault "always";
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security.apparmor.enable = mkDefault true;
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security.apparmor.killUnconfinedConfinables = mkDefault true;
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boot.kernelParams = [
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# Don't merge slabs
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"slab_nomerge"
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# Overwrite free'd pages
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"page_poison=1"
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# Enable page allocator randomization
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"page_alloc.shuffle=1"
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# Disable debugfs
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"debugfs=off"
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];
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boot.blacklistedKernelModules = [
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# Obscure network protocols
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"ax25"
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"netrom"
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"rose"
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# Old or rare or insufficiently audited filesystems
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"adfs"
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"affs"
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"bfs"
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"befs"
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"cramfs"
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"efs"
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"erofs"
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"exofs"
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"freevxfs"
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"f2fs"
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"hfs"
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"hpfs"
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"jfs"
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"minix"
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"nilfs2"
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"ntfs"
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"omfs"
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"qnx4"
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"qnx6"
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"sysv"
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"ufs"
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];
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# Hide kptrs even for processes with CAP_SYSLOG
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boot.kernel.sysctl."kernel.kptr_restrict" = mkOverride 500 2;
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# Disable bpf() JIT (to eliminate spray attacks)
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boot.kernel.sysctl."net.core.bpf_jit_enable" = mkDefault false;
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# Disable ftrace debugging
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boot.kernel.sysctl."kernel.ftrace_enabled" = mkDefault false;
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# Enable strict reverse path filtering (that is, do not attempt to route
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# packets that "obviously" do not belong to the iface's network; dropped
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# packets are logged as martians).
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boot.kernel.sysctl."net.ipv4.conf.all.log_martians" = mkDefault true;
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boot.kernel.sysctl."net.ipv4.conf.all.rp_filter" = mkDefault "1";
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boot.kernel.sysctl."net.ipv4.conf.default.log_martians" = mkDefault true;
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boot.kernel.sysctl."net.ipv4.conf.default.rp_filter" = mkDefault "1";
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# Ignore broadcast ICMP (mitigate SMURF)
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boot.kernel.sysctl."net.ipv4.icmp_echo_ignore_broadcasts" = mkDefault true;
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# Ignore incoming ICMP redirects (note: default is needed to ensure that the
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# setting is applied to interfaces added after the sysctls are set)
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boot.kernel.sysctl."net.ipv4.conf.all.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.all.secure_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.secure_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv6.conf.all.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv6.conf.default.accept_redirects" = mkDefault false;
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# Ignore outgoing ICMP redirects (this is ipv4 only)
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boot.kernel.sysctl."net.ipv4.conf.all.send_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.send_redirects" = mkDefault false;
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}
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