45 lines
1.7 KiB
Nix
45 lines
1.7 KiB
Nix
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{
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flake.modules.nixos.hardened = {
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lib,
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config,
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...
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}:
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with lib; let
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cfg = config.mySystem.boot.kernel;
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in {
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options.mySystem.boot.kernel.hardened = mkEnableOption "Enables hardened Linux kernel";
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config.boot = {
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kernelModules = lists.optional cfg.hardened "tcp_bbr";
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kernel.sysctl = mkIf cfg.hardened {
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"kernel.sysrq" = 0; # Disable magic SysRq key
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# Ignore ICMP broadcasts to avoid participating in Smurf attacks
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"net.ipv4.icmp_echo_ignore_broadcasts" = 1;
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# Ignore bad ICMP errors
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"net.ipv4.icmp_ignore_bogus_error_responses" = 1;
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# SYN flood protection
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"net.ipv4.tcp_syncookies" = 1;
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# Do not accept ICMP redirects (prevent MITM attacks)
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"net.ipv4.conf.all.accept_redirects" = 0;
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"net.ipv4.conf.default_accept_redirects" = 0;
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"net.ipv4.conf.all.secure_redirects" = 0;
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"net.ipv4.conf.default.secure_redirects" = 0;
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"net.ipv6.conf.all.accept_redirects" = 0;
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"net.ipv6.conf.default.accept_redirects" = 0;
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# Do not send ICMP redirects (we are not a router)
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"net.ipv4.conf.all.send_redirects" = 0;
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# Do not accept IP source route packets (we are not a router)
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"net.ipv4.conf.all.accept_source_route" = 0;
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"net.ipv6.conf.all.accept_source_route" = 0;
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# Protect against tcp time-wait assassination hazards
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"net.ipv4.tcp_rfc1337" = 1;
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# Latency reduction
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"net.ipv4.tcp_fastopen" = 3;
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# Bufferfloat mitigations
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"net.ipv4.tcp_congestion_control" = "bbr";
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"net.core.default_qdisc" = "cake";
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};
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};
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};
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}
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