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.
sysctl.d(5) recommends prefixing all filenames in /etc/sysctl.d with a
two-digit number and a dash, to simplify the ordering of the files.
Some packages provide custom files, often with "50-" prefix.
To ensure user-supplied configuration takes precedence over the one
specified via `boot.kernel.sysctl`, prefix the file generated there with
"60-".
The inability to run strace or gdb is the kind of
developer-unfriendliness that we're used to from OS X, let's not do it
on NixOS.
This restriction can be re-enabled by setting
boot.kernel.sysctl."kernel.yama.ptrace_scope" = 1;
It might be nice to have a NixOS module for enabling hardened defaults.
Xref #14392.
Thanks @abbradar.
If you define a unit, and either systemd or a package in
systemd.packages already provides that unit, then we now generate a
file /etc/systemd/system/<unit>.d/overrides.conf. This makes it
possible to use upstream units, while allowing them to be customised
from the NixOS configuration. For instance, the module nix-daemon.nix
now uses the units provided by the Nix package. And all unit
definitions that duplicated upstream systemd units are finally gone.
This makes the baseUnit option unnecessary, so I've removed it.
Using pkgs.lib.mkOverride in a sysctl option would throw a bogus error.
Also, if you defined a sysctl multiple times in the same configuration,
only one of the values would be picked up, while the others were silently
discarded.
This patch should fix both issues. If you define a sysctl multiple
times at your highest defined priority level, you will get a proper
error with detailed location information.
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
This module implements a significant refactoring in grsecurity
configuration for NixOS, making it far more usable by default and much
easier to configure.
- New security.grsecurity NixOS attributes.
- All grsec kernels supported
- Allows default 'auto' grsec configuration, or custom config
- Supports custom kernel options through kernelExtraConfig
- Defaults to high-security - user must choose kernel, server/desktop
mode, and any virtualisation software. That's all.
- kptr_restrict is fixed under grsecurity (it's unwriteable)
- grsecurity patch creation is now significantly abstracted
- only need revision, version, and SHA1
- kernel version requirements are asserted for sanity
- built kernels can have the uname specify the exact grsec version
for development or bug reports. Off by default (requires
`security.grsecurity.config.verboseVersion = true;`)
- grsecurity sysctl support
- By default, disabled.
- For people who enable it, NixOS deploys a 'grsec-lock' systemd
service which runs at startup. You are expected to configure sysctl
through NixOS like you regularly would, which will occur before the
service is started. As a result, changing sysctl settings requires
a reboot.
- New default group: 'grsecurity'
- Root is a member by default
- GRKERNSEC_PROC_GID is implicitly set to the 'grsecurity' GID,
making it possible to easily add users to this group for /proc
access
- AppArmor is now automatically enabled where it wasn't before, despite
implying features.apparmor = true
The most trivial example of enabling grsecurity in your kernel is by
specifying:
security.grsecurity.enable = true;
security.grsecurity.testing = true; # testing 3.13 kernel
security.grsecurity.config.system = "desktop"; # or "server"
This specifies absolutely no virtualisation support. In general, you
probably at least want KVM host support, which is a little more work.
So:
security.grsecurity.enable = true;
security.grsecurity.stable = true; # enable stable 3.2 kernel
security.grsecurity.config = {
system = "server";
priority = "security";
virtualisationConfig = "host";
virtualisationSoftware = "kvm";
hardwareVirtualisation = true;
}
This module has primarily been tested on Hetzner EX40 & VQ7 servers
using NixOps.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
E.g.
The unique option `fileSystems./.device' is defined multiple times, in `/etc/nixos/configuration.nix' and `/etc/nixos/foo.nix'.
This requires passing file/value tuples to the merge functions.
For instance, if time.timeZone is defined multiple times, you now get
the error message:
error: user-thrown exception: The unique option `time.timeZone' is defined multiple times, in `/etc/nixos/configurations/misc/eelco/x11vnc.nix' and `/etc/nixos/configuration.nix'.
while previously you got:
error: user-thrown exception: Multiple definitions of string. Only one is allowed for this option.
and only an inspection of the stack trace gave a clue as to what
option caused the problem.
