Fairly severe, but can be disabled at bootup via
grsec_sysfs_restrict=0. For the NixOS module we ensure that it is
disabled, for systemd compatibility.
Previously, we would only set a default value, on the theory that
`boot.kernelPackages` could be used to sanely configure a custom grsec
kernel. Regrettably, this is not the case and users who expect e.g.,
`boot.kernelPackages = pkgs.linuxPackages_latest` to work will end up
with a non-grsec kernel (this problem has come up twice on the bug
tracker recently).
With this patch, `security.grsecurity.enable = true` implies
`boot.kernelPackages = linuxPackages_grsec_nixos` and any customization
must be done via package override or by eschewing the module.
Using a custom package set with the NixOS module is no longer
something I wish to support. It's still *possible* but not
advertised. Secondly, the requiredKernelConfig didn't really
do anything (setting kernelPackages to a non-grsec kernel would
just silently let the user boot into a non-grsec setup ...).
While useless, some builds may dabble with setuid bits (e.g.,
util-linux), which breaks under grsec. In the interest of user
friendliness, we once again compromise by disabling an otherwise useful
feature ...
Closes https://github.com/NixOS/nixpkgs/issues/17501
Enabling EFI runtime services provides a venue for injecting code into
the kernel.
When grsecurity is enabled, we close this by default by disabling access
to EFI runtime services. The upshot of this is that
/sys/firmware/efi/efivars will be unavailable by default (and attempts
to mount it will fail).
This is not strictly a grsecurity related option, it could be made into
a general option, but it seems to be of particular interest to
grsecurity users (for non-grsecurity users, there are other, more
immediate kernel injection attack dangers to contend with anyway).
The new module is specifically adapted to the NixOS Grsecurity/PaX
kernel. The module declares the required kernel configurations and
so *should* be somewhat compatible with custom Grsecurity kernels.
The module exposes only a limited number of options, minimising the need
for user intervention beyond enabling the module. For experts,
Grsecurity/PaX behavior may be configured via `boot.kernelParams` and
`boot.kernel.sysctl`.
The module assumes the user knows what she's doing (esp. if she decides
to modify configuration values not directly exposed by the module).
Administration of Grsecurity's role based access control system is yet
to be implemented.
The chroot caps restriction disallows chroot'ed processes from running
any command that requires `CAP_SYS_ADMIN`, breaking `nixos-rebuild`. See
e.g., https://github.com/NixOS/nixpkgs/issues/15293
This significantly weakens chroot protections, but to break
nixos-rebuild out of the box is too severe.
The grsec-lock unit fails unless /proc/sys/kernel/grsecurity/grsec_lock
exists and so prevents switching into a new configuration after enabling
grsecurity.sysctl.
The option had been added to the grsec build-support code,
but it hadn't been added to the grsec module.
After this commit, grsec module users will be able to change
the default value. It also serves to document that this option
exists and that NixOS will disable it by default.
This updates the new stable kernel to 3.14, and the new testing kernel
to 3.15.
This also removes the vserver kernel, since it's probably not nearly as
used.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
This now provides a handful of different grsecurity kernels for slightly
different 'flavors' of packages. This doesn't change the grsecurity
module to use them just yet, however.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
AppArmor only requires a few patches to the 3.2 and 3.4 kernels in order
to work properly (with the minor catch grsecurity -stable includes the
3.2 patches.) This adds them to the kernel builds by default, removes
features.apparmor (since it's always true) and makes it the default MAC
system.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
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.
Previously we were setting GRKERNSEC_PROC_USER y, which was a little bit
too strict. It doesn't allow a special group (e.g. the grsecurity group
users) to access /proc information - this requires
GRKERNSEC_PROC_USERGROUP y, and the two are mutually exclusive.
This was also not in line with the default automatic grsecurity
configuration - it actually defaults to USERGROUP (although it has a
default GID of 1001 instead of ours), not USER.
This introduces a new option restrictProcWithGroup - enabled by default
- which turns on GRKERNSEC_PROC_USERGROUP instead. It also turns off
restrictProc by default and makes sure both cannot be enabled.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
