diff options
Diffstat (limited to 'nixos/modules')
| -rw-r--r-- | nixos/modules/default.nix | 1 | ||||
| -rw-r--r-- | nixos/modules/security.nix | 62 |
2 files changed, 63 insertions, 0 deletions
diff --git a/nixos/modules/default.nix b/nixos/modules/default.nix index f17f392..4469650 100644 --- a/nixos/modules/default.nix +++ b/nixos/modules/default.nix @@ -2,4 +2,5 @@ cachix = import ./cachix; flake = import ./flake.nix; nix = import ./nix.nix; + security = import ./security.nix; } diff --git a/nixos/modules/security.nix b/nixos/modules/security.nix new file mode 100644 index 0000000..4d79be9 --- /dev/null +++ b/nixos/modules/security.nix @@ -0,0 +1,62 @@ +{ config, lib, ... }: + +{ + # Security-related system tweaks + + # Prevent replacing the running kernel without reboot. + security.protectKernelImage = true; + + # mount /tmp in ram. This makes temp file management faster + # on ssd systems, and volatile! Because it's wiped on reboot. + boot.tmpOnTmpfs = true; + #boot.tmpOnTmpfsSize = "80%"; + + # Purge /tmp on boot. (fallback option) + boot.cleanTmpDir = lib.mkDefault (!config.boot.tmpOnTmpfs); + + 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" ]; + + # Accept CA's ToS. + security.acme.acceptTerms = true; +} |