diff --git a/modules/security.nix b/modules/security.nix new file mode 100644 index 0000000..f303258 --- /dev/null +++ b/modules/security.nix @@ -0,0 +1,71 @@ +{ config, lib, ... }: + +# Taken from https://github.com/hlissner/dotfiles +{ + ## System security tweaks + # sets hidepid=2 on /proc (make process info visible only to owning user) + # NOTE Was removed on nixpkgs-unstable because it doesn't do anything + # security.hideProcessInformation = true; + # Prevent replacing the running kernel w/o reboot + security.protectKernelImage = true; + + # tmpfs = /tmp is mounted in ram. Doing so makes temp file management speedy + # on ssd systems, and volatile! Because it's wiped on reboot. + boot.tmpOnTmpfs = lib.mkDefault true; + # If not using tmpfs, which is naturally purged on reboot, we must clean it + # /tmp ourselves. /tmp should be volatile storage! + boot.cleanTmpDir = lib.mkDefault (!config.boot.tmpOnTmpfs); + + # Fix a security hole in place for backwards compatibility. See desc in + # nixpkgs/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix + boot.loader.systemd-boot.editor = false; + + boot.kernel.sysctl = { + # The Magic SysRq key is a key combo that allows users connected to the + # system console of a Linux kernel to perform some low-level commands. + # Disable it, since we don't need it, and is a potential security concern. + "kernel.sysrq" = 0; + + ## TCP hardening + # Prevent bogus ICMP errors from filling up logs. + "net.ipv4.icmp_ignore_bogus_error_responses" = 1; + # Reverse path filtering causes the kernel to do source validation of + # packets received from all interfaces. This can mitigate IP spoofing. + "net.ipv4.conf.default.rp_filter" = 1; + "net.ipv4.conf.all.rp_filter" = 1; + # Do not accept IP source route packets (we're not a router) + "net.ipv4.conf.all.accept_source_route" = 0; + "net.ipv6.conf.all.accept_source_route" = 0; + # Don't send ICMP redirects (again, we're on a router) + "net.ipv4.conf.all.send_redirects" = 0; + "net.ipv4.conf.default.send_redirects" = 0; + # Refuse ICMP redirects (MITM mitigations) + "net.ipv4.conf.all.accept_redirects" = 0; + "net.ipv4.conf.default.accept_redirects" = 0; + "net.ipv4.conf.all.secure_redirects" = 0; + "net.ipv4.conf.default.secure_redirects" = 0; + "net.ipv6.conf.all.accept_redirects" = 0; + "net.ipv6.conf.default.accept_redirects" = 0; + # Protects against SYN flood attacks + "net.ipv4.tcp_syncookies" = 1; + # Incomplete protection again TIME-WAIT assassination + "net.ipv4.tcp_rfc1337" = 1; + + ## TCP optimization + # TCP Fast Open is a TCP extension that reduces network latency by packing + # data in the sender’s initial TCP SYN. Setting 3 = enable TCP Fast Open for + # both incoming and outgoing connections: + "net.ipv4.tcp_fastopen" = 3; + # Bufferbloat mitigations + slight improvement in throughput & latency + "net.ipv4.tcp_congestion_control" = "bbr"; + "net.core.default_qdisc" = "cake"; + }; + boot.kernelModules = [ "tcp_bbr" ]; + + # Change me later! + user.initialPassword = "nixos"; + users.users.root.initialPassword = "nixos"; + + # So we don't have to do this later... + security.acme.acceptTerms = true; +}