Commit graph

16 commits

Author SHA1 Message Date
alois31 f047e4357b libstore/build: always enable seccomp filtering and no-new-privileges
Seccomp filtering and the no-new-privileges functionality improve the security
of the sandbox, and have been enabled by default for a long time. In
lix-project/lix#265 it was decided that they
should be enabled unconditionally. Accordingly, remove the allow-new-privileges
(which had weird behavior anyway) and filter-syscall settings, and force the
security features on. Syscall filtering can still be enabled at build time to
support building on architectures libseccomp doesn't support.

Change-Id: Iedbfa18d720ae557dee07a24f69b2520f30119cb
2024-05-24 21:19:29 +00:00
Pierre Bourdon 6260563bed
nixos/tests: enable remoteBuilds tests against Nix 2.18
Fixes #321.

Change-Id: I60812aec9f9b68ab742413835c581d3b53432b9b
2024-05-23 21:16:40 +02:00
julia 5b7dcb3005 Allow enabling core dumps from builds for nix & child processes
Fixes lix-project/lix#268

Change-Id: I3f1b0ddf064f891cca8b53229c5c31c74cea3d9f
2024-05-16 17:11:21 -07:00
jade 9909a175bf Fix /etc/group having desynced IDs from the actual UID in the sandbox
This was found when `logrotate.conf` failed to build in a NixOS system
with:

    /nix/store/26zdl4pyw5qazppj8if5lm8bjzxlc07l-coreutils-9.3/bin/id: cannot find name for group ID 30000

This was surprising because it seemed to mean that /etc/group was busted
in the sandbox. Indeed it was:

    root0:
    nixbld:!💯
    nogroup65534:

We diagnosed this to sandboxUid() being called before
usingUserNamespace() was called, in setting up /etc/group inside the
sandbox. This code desperately needs refactoring.

We also moved the /etc/group code to be with the /etc/passwd code, but
honestly this code is all spaghetti'd all over the place and needs some
more serious tidying than we did here.

We also moved some checks to be earlier to improve locality with where
the things they are checking come from.

Change-Id: Ie29798771f3593c46ec313a32960fa955054aceb
2024-05-04 17:36:50 -07:00
Maximilian Bosch 79d0ae6670 Merge "libstore/local-derivation-goal: prohibit creating setuid/setgid binaries" into main 2024-05-04 07:26:15 +00:00
Maximilian Bosch 045ee37438 libstore/local-derivation-goal: prohibit creating setuid/setgid binaries
With Linux kernel >=6.6 & glibc 2.39 a `fchmodat2(2)` is available that
isn't filtered away by the libseccomp sandbox.

Being able to use this to bypass that restriction has surprising results
for some builds such as lxc[1]:

> With kernel ≥6.6 and glibc 2.39, lxc's install phase uses fchmodat2,
> which slips through 9b88e52846/src/libstore/build/local-derivation-goal.cc (L1650-L1663).
> The fixupPhase then uses fchmodat, which fails.
> With older kernel or glibc, setting the suid bit fails in the
> install phase, which is not treated as fatal, and then the
> fixup phase does not try to set it again.

Please note that there are still ways to bypass this sandbox[2] and this is
mostly a fix for the breaking builds.

This change works by creating a syscall filter for the `fchmodat2`
syscall (number 452 on most systems). The problem is that glibc 2.39
is needed to have the correct syscall number available via
`__NR_fchmodat2` / `__SNR_fchmodat2`, but this flake is still on
nixpkgs 23.11. To have this change everywhere and not dependent on the
glibc this package is built against, I added a header
"fchmodat2-compat.hh" that sets the syscall number based on the
architecture. On most platforms its 452 according to glibc with a few
exceptions:

    $ rg --pcre2 'define __NR_fchmodat2 (?!452)'
    sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
    58:#define __NR_fchmodat2 1073742276

    sysdeps/unix/sysv/linux/mips/mips64/n32/arch-syscall.h
    67:#define __NR_fchmodat2 6452

    sysdeps/unix/sysv/linux/mips/mips64/n64/arch-syscall.h
    62:#define __NR_fchmodat2 5452

    sysdeps/unix/sysv/linux/mips/mips32/arch-syscall.h
    70:#define __NR_fchmodat2 4452

    sysdeps/unix/sysv/linux/alpha/arch-syscall.h
    59:#define __NR_fchmodat2 562

I added a small regression-test to the setuid integration-test that
attempts to set the suid bit on a file using the fchmodat2 syscall.
I confirmed that the test fails without the change in
local-derivation-goal.

Additionally, we require libseccomp 2.5.5 or greater now: as it turns
out, libseccomp maintains an internal syscall table and
validates each rule against it. This means that when using libseccomp
2.5.4 or older, one may pass `452` as syscall number against it, but
since it doesn't exist in the internal structure, `libseccomp` will refuse
to create a filter for that. This happens with nixpkgs-23.11, i.e. on
stable NixOS and when building Lix against the project's flake.

To work around that

* a backport of libseccomp 2.5.5 on upstream nixpkgs has been
  scheduled[3].

* the package now uses libseccomp 2.5.5 on its own already. This is to
  provide a quick fix since the correct fix for 23.11 is still a staging cycle
  away.

We still need the compat header though since `SCMP_SYS(fchmodat2)`
internally transforms this into `__SNR_fchmodat2` which points to
`__NR_fchmodat2` from glibc 2.39, so it wouldn't build on glibc 2.38.
The updated syscall table from libseccomp 2.5.5 is NOT used for that
step, but used later, so we need both, our compat header and their
syscall table 🤷

Relevant PRs in CppNix:

* https://github.com/NixOS/nix/pull/10591
* https://github.com/NixOS/nix/pull/10501

[1] https://github.com/NixOS/nixpkgs/issues/300635#issuecomment-2031073804
[2] https://github.com/NixOS/nixpkgs/issues/300635#issuecomment-2030844251
[3] https://github.com/NixOS/nixpkgs/pull/306070

(cherry picked from commit ba6804518772e6afb403dd55478365d4b863c854)
Change-Id: I6921ab5a363188c6bff617750d00bb517276b7fe
2024-05-03 16:29:06 +02:00
Qyriad e2ab89a74b add VM test for nix upgrade-nix
This commit adds a new NixOS VM test, which tests that `nix upgrade-nix`
works on both kinds of profiles (manifest.nix and manifest.json).

Done as a separate commit from 831d18a13, since it relies on the
--store-path argument from 026c90e5f as well.

Change-Id: I5fc94b751d252862cb6cffb541a4c072faad9f3b
2024-04-29 01:19:21 +00:00
Ilya K effc28f6f5 libstore/build: set NO_NEW_PRIVS for the sandbox
Change-Id: I711f64e2b68495ed9c85c1a4bd5025405805e43a
2024-04-15 10:25:29 +03:00
Ilya K b469c6509b libstore/build: just copy the magic /etc files into the sandbox
Saves us a bunch of thinking about how to handle symlinks, and prevents
the DNS config from changing on the fly under the build, which may or may
not be a good thing?

Change-Id: I071e6ae7e220884690b788d94f480866f428db71
2024-04-13 12:43:19 +03:00
Rebecca Turner 2a98ba8b97 Add pre-commit checks
The big ones here are `trim-trailing-whitespace` and `end-of-file-fixer`
(which makes sure that every file ends with exactly one newline
character).

Change-Id: Idca73b640883188f068f9903e013cf0d82aa1123
2024-03-29 22:57:40 -07:00
puck 80b79d0137 flake.nix: upgrade to nixos-23.11
This also bypasses the Objective-C fork safety during tests.

Change-Id: I92bf9f911e8a1fbd32eae13255f9a9dabde40b21
2024-03-08 23:59:01 +00:00
eldritch horrors ca03f7cc28 Merge pull request #9676 from DavHau/git-testsuite
initialize test suite for git fetchers

(cherry picked from commit 0bd9e10aea747df51c8a5af124864c722cbeafde)
Change-Id: Idf94a47794190c3e1de07fc4e7848741c4e9ffed
2024-03-07 10:25:03 +01:00
eldritch horrors 097acae35b tests/nixos: Test remote build against older versions
(cherry picked from commit e502d1cf945fb3cdd0ca1e1c16ec330ccab51c7b)
Change-Id: If6a1758b6457c5dae9305829c4d71d1905cfca22
2024-03-06 21:32:47 -07:00
eldritch horrors 706f0df55b Merge pull request #9280 from R-VdP/rvdp/fix_remote_logging_phase_reporting
Include phase reporting in log file for ssh-ng builds

(cherry picked from commit b1e7d7cad625095656fff05ac4aedeb12135110a)
Change-Id: I4076669b0ba160412f7c628ca9113f9abbc8c303
2024-03-06 19:11:12 -07:00
puck 6f36a8834c Copy the output of fixed-output derivations before registering them
It is possible to exfiltrate a file descriptor out of the build sandbox
of FODs, and use it to modify the store path after it has been
registered. To avoid that issue, don't register the output of the build,
but a copy of it (that will be free of any leaked file descriptor).

Test that we can't leverage abstract unix domain sockets to leak file
descriptors out of the sandbox and modify the path after it has been
registered.

(cherry picked from commit 2dadfeb690e7f4b8f97298e29791d202fdba5ca6)
(tests cherry picked from commit c854ae5b3078ac5d99fa75fe148005044809e18c)

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Co-authored-by: Theophane Hufschmitt <theophane.hufschmitt@tweag.io>
Co-authored-by: Tom Bereknyei <tomberek@gmail.com>

Change-Id: I87cd58f1c0a4f7b7a610d354206b33301e47b1a4
2024-03-07 01:44:58 +00:00
eldritch horrors 2e1f5e2666 Merge pull request #9105 from Ericson2314/split-out-nixos-tests
Define NixOS tests in `tests/nixos/default.nix` rather than `flake.nix`

(cherry picked from commit c29b8ba142a0650d1182ca838ddc1b2d273dcd2a)
Change-Id: Ieae1b6476d95024485df7067e008013bc5542039
2024-03-05 21:11:59 +01:00