If you have the Nix store mounted from a nonlocal filesystem whose
exporter is not running as root, making the directory mode 000 makes it
inaccessible to that remote unprivileged user and therefore breaks the
build. (Specifically, I am running into this with a virtiofs mount using
Apple Virtualization.framework as a non-root user, but I expect the
same thing would happen with virtiofs in qemu on Linux as a non-root
user or with various userspace network file servers.)
Make the directory mode 500 (dr-x------) to make the sandbox work in
this use case, which explicitly conveys our intention to read and search
the directory. The code only works because root can already bypass
directory checks, so this does not actually grant more permissions to
the directory owner / does not make the sandbox less secure.
This patch has been manually adapted from
14dc84ed03
Tested with:
$ NIX_SSL_CERT_FILE=$(nix-build '<nixpkgs>' -A cacert)/etc/ssl/certs/ca-bundle.crt nix-build --store $(mktemp -d) -E 'import <nix/fetchurl.nix> { url = https://google.com; }'
Finished at 16:57:50 after 1s
warning: found empty hash, assuming 'sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA='
this derivation will be built:
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com> building '/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv'
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com> error:
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com> … writing file '/nix/store/0zynn4n8yx59bczy1mgh1lq2rnprvvrc-google.com'
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com>
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com> error: unable to download 'https://google.com': Problem with the SSL CA cert (path? access rights?) (77) error setting certificate file: /nix/store/nlgbippbbgn38hynjkp1ghiybcq1dqhx-nss-cacert-3.101.1/etc/ssl/certs/ca-bundle.crt
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
error: builder for '/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv' failed with exit code 1
Now returns:
nix-env % NIX_SSL_CERT_FILE=$(nix-build '<nixpkgs>' -A cacert)/etc/ssl/certs/ca-bundle.crt nix-build --store $(mktemp -d) -E 'import <nix/fetchurl.nix> { url = https://google.com; }'
Finished at 17:05:48 after 0s
warning: found empty hash, assuming 'sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA='
this derivation will be built:
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
google.com> building '/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv'
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
nix-output-monitor error: DerivationReadError /nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv: openFile: does not exist (No such file or directory)
error: hash mismatch in fixed-output derivation '/nix/store/4qljhy0jj2b0abjzpsbyarpia1bqylwc-google.com.drv':
specified: sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
Caused by 1d3696f0fb
Without this fix the kept build directory is readable only by root
```
$ sudo ls -ld /comp-temp/nix-build-openssh-static-x86_64-unknown-linux-musl-9.8p1.drv-5
drwx------ root root 60 B Wed Sep 11 00:09:48 2024 /comp-temp/nix-build-openssh-static-x86_64-unknown-linux-musl-9.8p1.drv-5/
$ sudo ls -ld /comp-temp/nix-build-openssh-static-x86_64-unknown-linux-musl-9.8p1.drv-5/build
drwxr-xr-x nixbld1 nixbld 80 B Wed Sep 11 00:09:58 2024 /comp-temp/nix-build-openssh-static-x86_64-unknown-linux-musl-9.8p1.drv-5/build/
```
The daemon process is now moved into a new sub-cgroup called nix-daemon when the
daemon starts. This is necessary to abide by the no-processes-in-inner-nodes
rule, because the service cgroup becomes an inner node when the child cgroups
for the build are created (see LocalDerivationGoal::startBuilder()).
See #9675
This reverts commit 43e82c9446, reversing
changes made to d79b9bdec0.
Since /proc/homeless-shelter returns a different errno than /homeless-shelter (ENOENT vs EACCES), we need to revert this change.
Software depends on this error code i.e. cargo and therefore breaks.
this is only used to close non-stdio files in derivation sandboxes. we
may as well encode that in its name, drop the unnecessary integer set,
and use close_range to deal with the actual closing of files. not only
is this clearer, it also makes sandbox setup on linux fast by 1ms each
(cherry-picked and adapted from
c7d97802e4)
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: Cole Helbling <cole.e.helbling@outlook.com>
Co-authored-by: John Ericson <git@JohnEricson.me>
This is because with the split packages of the Meson build, we simply
have no idea what directory the binaries will be installed in when we
build the library.
In the process of doing so, consolidate and make more sophisticated the
logic to cope with a few corner cases (e.g. `NIX_BIN_DIR` exists, but no
binaries are inside it).
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
In d60c3f7f7c, this was changed to close a
hole in the sandbox. Unfortunately, this was too restrictive such that it
made local port binding fail, thus making derivations that needed
`__darwinAllowLocalNetworking` gain nearly nothing, and thus largely
fail (as the primary use for it is to enable port binding).
This unfortunately does mean that a sandboxed build process can, in
coordination with an actor outside the sandbox, escape the sandbox by
binding a port and connecting to it externally to send data. I do not
see a way around this with my experimentation and understanding of the
(quite undocumented) macOS sandbox profile API. Notably it seems not
possible to use the sandbox to do any of:
- Restrict the remote IP of inbound network requests
- Restrict the address being bound to
As such, the `(local ip "*:*")` here appears to be functionally no
different than `(local ip "localhost:*")` (however it *should* be
different than removing the filter entirely, as that would make it also
apply to non-IP networking). Doing `(allow network-inbound (require-all
(local ip "localhost:*") (remote ip "localhost:*")))` causes listening
to fail.
Note that `network-inbound` implies `network-bind`.
This change updates the seccomp profile to return ENOTSUP for getxattr
functions family. This reflects the behavior of filesystems that don’t
support extended attributes (or have an option to disable them), e.g.
ext2.
The current behavior is confusing for some programs because we can read
extended attributes, but only get to know that they are not supported
when setting them. In addition to that, ACLs on Linux are implemented
via extended attributes internally and if we don’t return ENOTSUP, acl
library converts file mode to ACL.
https://git.savannah.nongnu.org/cgit/acl.git/tree/libacl/acl_get_file.c?id=d9bb1759d4dad2f28a6dcc8c1742ff75d16dd10d#n69
(System) features are unlikely to be empty strings, but when they
come in through structuredAttrs, they probably can.
I don't think this means we should drop them, but most likely they
will be dropped after this because next time they'll be parsed with
tokenizeString.
TODO: We should forbid empty features.
The recent fix for CVE-2024-38531 broke the sandbox on macOS
completely. As it’s not practical to use `chroot(2)` on
macOS, the build takes place in the main filesystem tree, and the
world‐unreadable wrapper directory prevents the build from accessing
its `$TMPDIR` at all.
The macOS sandbox probably shouldn’t be treated as any kind of a
security boundary in its current state, but this specific vulnerability
wasn’t possible to exploit on macOS anyway, as creating `set{u,g}id`
binaries is blocked by sandbox policy.
Locking down the build sandbox further may be a good idea in future,
but it already has significant compatibility issues. For now, restore
the previous status quo on macOS.
Thanks to @alois31 for helping me come to a better understanding of
the vulnerability.
Fixes: 1d3696f0fbCloses: #11002
Previously, the .chroot directory had permission 750 or 755 (depending
on the uid-range system feature) and was owned by root/nixbld. This
makes it possible for any nixbld user (if uid-range is disabled) or
any user (if uid-range is enabled) to inspect the contents of the
chroot of an active build and maybe interfere with it (e.g. via /tmp
in the chroot, which has 1777 permission).
To prevent this, the root is now a subdirectory of .chroot, which has
permission 700 and is owned by root/root.
Instead of running the builds under
`$TMPDIR/{unique-build-directory-owned-by-the-build-user}`, run them
under `$TMPDIR/{unique-build-directory-owned-by-the-daemon}/{subdir-owned-by-the-build-user}`
where the build directory is only readable and traversable by the daemon user.
This achieves two things:
1. It prevents builders from making their build directory world-readable
(or even writeable), which would allow the outside world to interact
with them.
2. It prevents external processes running as the build user (either
because that somehow leaked, maybe as a consequence of 1., or because
`build-users` isn't in use) from gaining access to the build
directory.
Special thanks to everyone that has worked on a Meson port so far,
@p01arst0rm and @Qyriad in particular.
Co-Authored-By: p01arst0rm <polar@ever3st.com>
Co-Authored-By: Artemis Tosini <lix@artem.ist>
Co-Authored-By: Artemis Tosini <me@artem.ist>
Co-Authored-By: Felix Uhl <felix.uhl@outlook.com>
Co-Authored-By: Jade Lovelace <lix@jade.fyi>
Co-Authored-By: Lunaphied <lunaphied@lunaphied.me>
Co-Authored-By: Maximilian Bosch <maximilian@mbosch.me>
Co-Authored-By: Pierre Bourdon <delroth@gmail.com>
Co-Authored-By: Qyriad <qyriad@qyriad.me>
Co-Authored-By: Rebecca Turner <rbt@sent.as>
Co-Authored-By: Winter <winter@winter.cafe>
Co-Authored-By: eldritch horrors <pennae@lix.systems>
Co-Authored-By: jade <lix@jade.fyi>
Co-Authored-By: julia <midnight@trainwit.ch>
Co-Authored-By: rebecca “wiggles” turner <rbt@sent.as>
Co-Authored-By: wiggles dog <rbt@sent.as>
Co-Authored-By: fricklerhandwerk <valentin@fricklerhandwerk.de>
Co-authored-by: Eli Schwartz <eschwartz93@gmail.com>
1. Fix build by making the legacy SSH Storey's secret `logFD` setting
not a setting on Windows. (It doesn't make sense to specify `void *`
handles by integer cross-proccess, I don't think.)
2. Move some files that don't need to be Unix-only anymore back to their
original locations.
- Get a rump derivation goal: hook instance will come later, local
derivation goal will come after that.
- Start cleaning up the channel / waiting code with an abstraction.
In particular `local://<path>` and `unix://` (without any path) now
work, and mean the same things as `local` and `daemon`, respectively. We
thus now have the opportunity to desguar `local` and `daemon` early.
This will allow me to make a change to
https://github.com/NixOS/nix/pull/9839 requested during review to
desugar those earlier.
Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
