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Author SHA1 Message Date
Joachim Fasting 9a9237e0aa
grsecurity: revamp nixos kernel config
Cleanup:
- Restructure & add some commentary
- Remove redundant option specs given the auto config
  constraints (some are left in for documentation purposes)

Changes:
- GRKERNSEC_CONFIG_VIRT_HOST -> GUEST
  The former deselects paravirtualization and friends
- PAX_LATENT_ENTROPY n -> y (implied by auto)
- GRKERNSEC_ACL_HIDEKERN y -> n
  Possibly useless with redistribution
2016-10-02 19:25:58 +02:00
Joachim Fasting 1bb7b44cd7
grsecurity: make GRKERNSEC y and PAX y implicit
These options should always be specified. Note, an implication of this
change is that not specifying any grsec/PaX options results in a build
failure.
2016-10-02 19:25:58 +02:00
Joachim Fasting b1cceeda84
grsecurity: enable pax size overflow plugin 2016-08-16 17:50:36 +02:00
Joachim Fasting 3fcb9e6f57
grsecurity: support non-enforcing mode
Until we've made sure that most things actually work out of the box, we
need to give people a way of continuing to use the system without
completely disabling grsecurity.

Set sysctl kernel.pax.softmode=1 or boot with pax.softmode=1
2016-08-16 17:50:36 +02:00
Joachim Fasting c93ffb95bc
grsecurity: enable support for setting pax flags via xattrs
While useless for binaries within the Nix store, user xattrs are a convenient
alternative for setting PaX flags to executables outside of the store.

To use disable secure memory protections for a non-store file foo, do
  $ setfattr -n user.pax.flags -v em foo
2016-07-20 10:17:11 +02:00
Joachim Fasting 75b9a7beac
grsecurity: implement a single NixOS kernel
This patch replaces the old grsecurity kernels with a single NixOS
specific grsecurity kernel.  This kernel is intended as a general
purpose kernel, tuned for casual desktop use.

Providing only a single kernel may seem like a regression compared to
offering a multitude of flavors.  It is impossible, however, to
effectively test and support that many options.  This is amplified by
the reality that very few seem to actually use grsecurity on NixOS,
meaning that bugs go unnoticed for long periods of time, simply because
those code paths end up never being exercised.  More generally, it is
hopeless to anticipate imagined needs.  It is better to start from a
solid foundation and possibly add more flavours on demand.

While the generic kernel is intended to cover a wide range of use cases,
it cannot cover everything.  For some, the configuration will be either
too restrictive or too lenient.  In those cases, the recommended
solution is to build a custom kernel --- this is *strongly* recommended
for security sensitive deployments.

Building a custom grsec kernel should be as simple as
```nix
linux_grsec_nixos.override {
  extraConfig = ''
    GRKERNSEC y
    PAX y
    # and so on ...
  '';
}
```

The generic kernel should be usable both as a KVM guest and host.  When
running as a host, the kernel assumes hardware virtualisation support.
Virtualisation systems other than KVM are *unsupported*: users of
non-KVM systems are better served by compiling a custom kernel.

Unlike previous Grsecurity kernels, this configuration disables `/proc`
restrictions in favor of `security.hideProcessInformation`.

Known incompatibilities:
- ZFS: can't load spl and zfs kernel modules; claims incompatibility
  with KERNEXEC method `or` and RAP; changing to `bts` does not fix the
  problem, which implies we'd have to disable RAP as well for ZFS to
  work
- `kexec()`: likely incompatible with KERNEXEC (unverified)
- Xen: likely incompatible with KERNEXEC and UDEREF (unverified)
- Virtualbox: likely incompatible with UDEREF (unverified)
2016-06-14 00:08:20 +02:00