This prevents builders from setting the S_ISUID or S_ISGID bits,
preventing users from using a nixbld* user to create a setuid/setgid
binary to interfere with subsequent builds under the same nixbld* uid.
This is based on aszlig's seccomp code
(47f587700d).
Reported by Linus Heckemann.
(cherry picked from commit 6cc6c15a2d)
This reverts commit 80ebd60e7c. The
reason why we cleared CFLAGS/CXXFLAGS was because otherwise we get a
default value of -O2, which interferes with the defaults set in the
Makefile. (E.g. "make OPTIMIZE=0" should not pass -O2.)
chroot only changes the process root directory, not the mount namespace root
directory, and it is well-known that any process with chroot capability can
break out of a chroot "jail". By using pivot_root as well, and unmounting the
original mount namespace root directory, breaking out becomes impossible.
Non-root processes typically have no ability to use chroot() anyway, but they
can gain that capability through the use of clone() or unshare(). For security
reasons, these syscalls are limited in functionality when used inside a normal
chroot environment. Using pivot_root() this way does allow those syscalls to be
put to their full use.
Sodium's Ed25519 signatures are much shorter than OpenSSL's RSA
signatures. Public keys are also much shorter, so they're now
specified directly in the nix.conf option ‘binary-cache-public-keys’.
The new command ‘nix-store --generate-binary-cache-key’ generates and
prints a public and secret key.
On a system with multiple CPUs, running Nix operations through the
daemon is significantly slower than "direct" mode:
$ NIX_REMOTE= nix-instantiate '<nixos>' -A system
real 0m0.974s
user 0m0.875s
sys 0m0.088s
$ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system
real 0m2.118s
user 0m1.463s
sys 0m0.218s
The main reason seems to be that the client and the worker get moved
to a different CPU after every call to the worker. This patch adds a
hack to lock them to the same CPU. With this, the overhead of going
through the daemon is very small:
$ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system
real 0m1.074s
user 0m0.809s
sys 0m0.098s
/nix/store could be a read-only bind mount even if it is / in its own filesystem, so checking the 4th field in mountinfo is insufficient.
Signed-off-by: Shea Levy <shea@shealevy.com>
vfork() is just too weird. For instance, in this build:
http://hydra.nixos.org/build/3330487
the value fromHook.writeSide becomes corrupted in the parent, even
though the child only reads from it. At -O0 the problem goes away.
Probably the child is overriding some spilled temporary variable.
If I get bored I may implement using posix_spawn() instead.
XZ compresses significantly better than bzip2. Here are the
compression ratios and execution times (using 4 cores in parallel) on
my /var/run/current-system (3.1 GiB):
bzip2: total compressed size 849.56 MiB, 30.8% [2m08]
xz -6: total compressed size 641.84 MiB, 23.4% [6m53]
xz -7: total compressed size 621.82 MiB, 22.6% [7m19]
xz -8: total compressed size 599.33 MiB, 21.8% [7m18]
xz -9: total compressed size 588.18 MiB, 21.4% [7m40]
Note that compression takes much longer. More importantly, however,
decompression is much faster:
bzip2: 1m47.274s
xz -6: 0m55.446s
xz -7: 0m54.119s
xz -8: 0m52.388s
xz -9: 0m51.842s
The only downside to using -9 is that decompression takes a fair
amount (~65 MB) of memory.
