From 9be0327a4975e219957d5108b3753a7640c4a9e0 Mon Sep 17 00:00:00 2001 From: Florian Klink Date: Sun, 11 Aug 2019 13:32:24 +0200 Subject: [PATCH] nixos/systemd: install sysctl snippets systemd provides two sysctl snippets, 50-coredump.conf and 50-default.conf. These enable: - Loose reverse path filtering - Source route filtering - `fq_codel` as a packet scheduler (this helps to fight bufferbloat) This also configures the kernel to pass coredumps to `systemd-coredump`. These sysctl snippets can be found in `/etc/sysctl.d/50-*.conf`, and overridden via `boot.kernel.sysctl` (which will place the parameters in `/etc/sysctl.d/60-nixos.conf`. Let's start using these, like other distros already do for quite some time, and remove those duplicate `boot.kernel.sysctl` options we previously did set. In the case of rp_filter (which systemd would set to 2 (loose)), make our overrides to "1" more explicit. --- nixos/doc/manual/release-notes/rl-1909.xml | 24 +++++++++++++++++++ nixos/modules/config/sysctl.nix | 6 ----- nixos/modules/profiles/hardened.nix | 16 ++++--------- nixos/modules/system/boot/systemd.nix | 4 ++++ .../virtualisation/google-compute-config.nix | 10 ++------ 5 files changed, 35 insertions(+), 25 deletions(-) diff --git a/nixos/doc/manual/release-notes/rl-1909.xml b/nixos/doc/manual/release-notes/rl-1909.xml index 4fe82e10ae6..e63a6d10a86 100644 --- a/nixos/doc/manual/release-notes/rl-1909.xml +++ b/nixos/doc/manual/release-notes/rl-1909.xml @@ -444,6 +444,30 @@ two-digit number and a dash to simplify the ordering of the files. + + + We now install the sysctl snippets shipped with systemd. + + This enables: + + Loose reverse path filtering + + + Source route filtering + + + + fq_codel as a packet scheduler (this helps to fight bufferbloat) + + + + + This also configures the kernel to pass coredumps to systemd-coredump. + These sysctl snippets can be found in /etc/sysctl.d/50-*.conf, + and overridden via boot.kernel.sysctl + (which will place the parameters in /etc/sysctl.d/60-nixos.conf). + + diff --git a/nixos/modules/config/sysctl.nix b/nixos/modules/config/sysctl.nix index 112e5e744d4..fb2b58eed72 100644 --- a/nixos/modules/config/sysctl.nix +++ b/nixos/modules/config/sysctl.nix @@ -52,12 +52,6 @@ in restartTriggers = [ config.environment.etc."sysctl.d/60-nixos.conf".source ]; }; - # Enable hardlink and symlink restrictions. See - # https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=800179c9b8a1e796e441674776d11cd4c05d61d7 - # for details. - boot.kernel.sysctl."fs.protected_hardlinks" = true; - boot.kernel.sysctl."fs.protected_symlinks" = true; - # Hide kernel pointers (e.g. in /proc/modules) for unprivileged # users as these make it easier to exploit kernel vulnerabilities. boot.kernel.sysctl."kernel.kptr_restrict" = 1; diff --git a/nixos/modules/profiles/hardened.nix b/nixos/modules/profiles/hardened.nix index 3ff9a2b4fde..46417579352 100644 --- a/nixos/modules/profiles/hardened.nix +++ b/nixos/modules/profiles/hardened.nix @@ -95,23 +95,17 @@ with lib; # Disable ftrace debugging boot.kernel.sysctl."kernel.ftrace_enabled" = mkDefault false; - # Enable 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). + # 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 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 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 route information from sender - boot.kernel.sysctl."net.ipv4.conf.all.accept_source_route" = mkDefault false; - boot.kernel.sysctl."net.ipv4.conf.default.accept_source_route" = mkDefault false; - boot.kernel.sysctl."net.ipv6.conf.all.accept_source_route" = mkDefault false; - boot.kernel.sysctl."net.ipv6.conf.default.accept_source_route" = mkDefault false; - # 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; diff --git a/nixos/modules/system/boot/systemd.nix b/nixos/modules/system/boot/systemd.nix index 1914827d0e5..e84b1ffbfc1 100644 --- a/nixos/modules/system/boot/systemd.nix +++ b/nixos/modules/system/boot/systemd.nix @@ -831,6 +831,10 @@ in [Sleep] ''; + # install provided sysctl snippets + "sysctl.d/50-coredump.conf".source = "${systemd}/example/sysctl.d/50-coredump.conf"; + "sysctl.d/50-default.conf".source = "${systemd}/example/sysctl.d/50-default.conf"; + "tmpfiles.d/systemd.conf".source = "${systemd}/example/tmpfiles.d/systemd.conf"; "tmpfiles.d/x11.conf".source = "${systemd}/example/tmpfiles.d/x11.conf"; diff --git a/nixos/modules/virtualisation/google-compute-config.nix b/nixos/modules/virtualisation/google-compute-config.nix index 5c59188b68b..79766970c75 100644 --- a/nixos/modules/virtualisation/google-compute-config.nix +++ b/nixos/modules/virtualisation/google-compute-config.nix @@ -159,12 +159,6 @@ in # functionality/features (e.g. TCP Window scaling). "net.ipv4.tcp_syncookies" = mkDefault "1"; - # ignores source-routed packets - "net.ipv4.conf.all.accept_source_route" = mkDefault "0"; - - # ignores source-routed packets - "net.ipv4.conf.default.accept_source_route" = mkDefault "0"; - # ignores ICMP redirects "net.ipv4.conf.all.accept_redirects" = mkDefault "0"; @@ -186,10 +180,10 @@ in # don't allow traffic between networks or act as a router "net.ipv4.conf.default.send_redirects" = mkDefault "0"; - # reverse path filtering - IP spoofing protection + # strict reverse path filtering - IP spoofing protection "net.ipv4.conf.all.rp_filter" = mkDefault "1"; - # reverse path filtering - IP spoofing protection + # strict path filtering - IP spoofing protection "net.ipv4.conf.default.rp_filter" = mkDefault "1"; # ignores ICMP broadcasts to avoid participating in Smurf attacks