dotfiles/nixos/security.nix

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Nix
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{
config,
pkgs,
lib,
...
}: {
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networking.firewall.checkReversePath = "loose";
networking.firewall.enable = true;
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nix.settings.allowed-users = ["@users"];
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security = {
apparmor.enable = true;
apparmor.killUnconfinedConfinables = true;
forcePageTableIsolation = true;
lockKernelModules = false;
protectKernelImage = true;
virtualisation.flushL1DataCache = "always";
};
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sops.age = {
keyFile = "/var/lib/sops-nix/key.txt";
generateKey = true;
};
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boot = {
kernelParams = ["slub_debug=FZP" "page_poison=1" "page_alloc.shuffle=1"];
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blacklistedKernelModules = [
# Obscure network protocols
"ax25"
"netrom"
"rose"
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# Old or rare or insufficiently audited filesystems
"adfs"
"affs"
"bfs"
"befs"
"cramfs"
"efs"
"erofs"
"exofs"
"freevxfs"
"f2fs"
"hfs"
"hpfs"
"jfs"
"minix"
"nilfs2"
"omfs"
"qnx4"
"qnx6"
"sysv"
"ufs"
];
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kernel.sysctl = {
# Restrict ptrace() usage to processes with a pre-defined relationship
# (e.g., parent/child)
"kernel.yama.ptrace_scope" = lib.mkOverride 500 1;
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# Hide kptrs even for processes with CAP_SYSLOG
"kernel.kptr_restrict" = lib.mkOverride 500 2;
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# Disable bpf() JIT (to eliminate spray attacks)
"net.core.bpf_jit_enable" = false;
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# Disable ftrace debugging
"kernel.ftrace_enabled" = false;
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# 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).
"net.ipv4.conf.all.log_martians" = true;
"net.ipv4.conf.all.rp_filter" = "1";
"net.ipv4.conf.default.log_martians" = true;
"net.ipv4.conf.default.rp_filter" = "1";
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# Ignore broadcast ICMP (mitigate SMURF)
"net.ipv4.icmp_echo_ignore_broadcasts" = true;
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# Ignore incoming ICMP redirects (note: default is needed to ensure that the
# setting is applied to interfaces added after the sysctls are set)
"net.ipv4.conf.all.accept_redirects" = false;
"net.ipv4.conf.all.secure_redirects" = false;
"net.ipv4.conf.default.accept_redirects" = false;
"net.ipv4.conf.default.secure_redirects" = false;
"net.ipv6.conf.all.accept_redirects" = false;
"net.ipv6.conf.default.accept_redirects" = false;
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# Ignore outgoing ICMP redirects (this is ipv4 only)
"net.ipv4.conf.all.send_redirects" = false;
"net.ipv4.conf.default.send_redirects" = false;
};
};
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}