1 files changed, 122 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/profiles/hardened.nix b/nixpkgs/nixos/modules/profiles/hardened.nix
new file mode 100644
index 00000000000..626d8b1d2bd
--- /dev/null
+++ b/nixpkgs/nixos/modules/profiles/hardened.nix
@@ -0,0 +1,122 @@
+# A profile with most (vanilla) hardening options enabled by default,
+# potentially at the cost of features and performance.
+
+{ lib, pkgs, ... }:
+
+with lib;
+
+{
+  meta = {
+    maintainers = [ maintainers.joachifm ];
+  };
+
+  boot.kernelPackages = mkDefault pkgs.linuxPackages_hardened;
+
+  nix.allowedUsers = mkDefault [ "@users" ];
+
+  security.hideProcessInformation = mkDefault true;
+
+  security.lockKernelModules = mkDefault true;
+
+  security.allowUserNamespaces = mkDefault false;
+
+  security.protectKernelImage = mkDefault true;
+
+  security.allowSimultaneousMultithreading = mkDefault false;
+
+  security.forcePageTableIsolation = mkDefault true;
+
+  security.virtualisation.flushL1DataCache = mkDefault "always";
+
+  security.apparmor.enable = mkDefault true;
+
+  boot.kernelParams = [
+    # Slab/slub sanity checks, redzoning, and poisoning
+    "slub_debug=FZP"
+
+    # Disable slab merging to make certain heap overflow attacks harder
+    "slab_nomerge"
+
+    # Overwrite free'd memory
+    "page_poison=1"
+
+    # Disable legacy virtual syscalls
+    "vsyscall=none"
+
+    # Enable page allocator randomization
+    "page_alloc.shuffle=1"
+  ];
+
+  boot.blacklistedKernelModules = [
+    # Obscure network protocols
+    "ax25"
+    "netrom"
+    "rose"
+  ];
+
+  # Restrict ptrace() usage to processes with a pre-defined relationship
+  # (e.g., parent/child)
+  boot.kernel.sysctl."kernel.yama.ptrace_scope" = mkOverride 500 1;
+
+  # Restrict access to kernel ring buffer (information leaks)
+  boot.kernel.sysctl."kernel.dmesg_restrict" = mkDefault true;
+
+  # Hide kptrs even for processes with CAP_SYSLOG
+  boot.kernel.sysctl."kernel.kptr_restrict" = mkOverride 500 2;
+
+  # Unprivileged access to bpf() has been used for privilege escalation in
+  # the past
+  boot.kernel.sysctl."kernel.unprivileged_bpf_disabled" = mkDefault true;
+
+  # Disable bpf() JIT (to eliminate spray attacks)
+  boot.kernel.sysctl."net.core.bpf_jit_enable" = mkDefault false;
+
+  # ... or at least apply some hardening to it
+  boot.kernel.sysctl."net.core.bpf_jit_harden" = mkDefault true;
+
+  # Raise ASLR entropy for 64bit & 32bit, respectively.
+  #
+  # Note: mmap_rnd_compat_bits may not exist on 64bit.
+  boot.kernel.sysctl."vm.mmap_rnd_bits" = mkDefault 32;
+  boot.kernel.sysctl."vm.mmap_rnd_compat_bits" = mkDefault 16;
+
+  # Allowing users to mmap() memory starting at virtual address 0 can turn a
+  # NULL dereference bug in the kernel into code execution with elevated
+  # privilege.  Mitigate by enforcing a minimum base addr beyond the NULL memory
+  # space.  This breaks applications that require mapping the 0 page, such as
+  # dosemu or running 16bit applications under wine.  It also breaks older
+  # versions of qemu.
+  #
+  # The value is taken from the KSPP recommendations (Debian uses 4096).
+  boot.kernel.sysctl."vm.mmap_min_addr" = mkDefault 65536;
+
+  # 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;
+
+  # Restrict userfaultfd syscalls to processes with the SYS_PTRACE capability
+  boot.kernel.sysctl."vm.unprivileged_userfaultfd" = mkDefault false;
+}