executed in a chroot that contains just the Nix store, the temporary
build directory, and a configurable set of additional directories
(/dev and /proc by default). This allows a bit more purity
enforcement: hidden build-time dependencies on directories such as
/usr or /nix/var/nix/profiles are no longer possible. As an added
benefit, accidental network downloads (cf. NIXPKGS-52) are prevented
as well (because files such as /etc/resolv.conf are not available in
the chroot).
However the usefulness of chroots is diminished by the fact that
many builders depend on /bin/sh, so you need /bin in the list of
additional directories. (And then on non-NixOS you need /lib as
well...)
usage by finding identical files in the store and hard-linking them
to each other. It typically reduces the size of the store by
something like 25-35%. This is what the optimise-store.pl script
did, but the new command is faster and more correct (it's safe wrt
garbage collection and concurrent builds).
(/nix/var/nix/daemon-socket). This allows access to the Nix daemon
to be restricted by setting the mode/ownership on that directory as
desired, e.g.
$ chmod 770 /nix/var/nix/daemon-socket
$ chown root.wheel /nix/var/nix/daemon-socket
to allow only users in the wheel group to use Nix.
Setting the ownership on a socket is much trickier, since the socket
must be deleted and recreated every time the daemon is started
(which would require additional Nix configuration file directives to
specify the mode/ownership, and wouldn't support arbitrary ACLs),
some BSD variants appear to ignore permissions on sockets, and it's
not clear whether the umask is respected on every platform when
creating sockets.
fixed-output derivations or substitutions try to build the same
store path at the same time. Locking generally catches this, but
not between multiple goals in the same process. This happened
especially often (actually, only) in the build farm with fetchurl
downloads of the same file being executed on multiple machines and
then copied back to the main machine where they would clobber each
other (NIXBF-13).
Solution: if a goal notices that the output path is already locked,
then go to sleep until another goal finishes (hopefully the one
locking the path) and try again.
need any info on substitutable paths, we just call the substituters
(such as download-using-manifests.pl) directly. This means that
it's no longer necessary for nix-pull to register substitutes or for
nix-channel to clear them, which makes those operations much faster
(NIX-95). Also, we don't have to worry about keeping nix-pull
manifests (in /nix/var/nix/manifests) and the database in sync with
each other.
The downside is that there is some overhead in calling an external
program to get the substitutes info. For instance, "nix-env -qas"
takes a bit longer.
Abolishing the substitutes table also makes the logic in
local-store.cc simpler, as we don't need to store info for invalid
paths. On the downside, you cannot do things like "nix-store -qR"
on a substitutable but invalid path (but nobody did that anyway).
* Never catch interrupts (the Interrupted exception).
--export' into the Nix store, and optionally check the cryptographic
signatures against /nix/etc/nix/signing-key.pub. (TODO: verify
against a set of public keys.)
path. This is like `nix-store --dump', only it also dumps the
meta-information of the store path (references, deriver). Will add
a `--sign' flag later to add a cryptographic signature, which we
will use for exchanging store paths between build farm machines in a
secure manner.
computing the store path (NIX-77). This is an important security
property in multi-user Nix stores.
Note that this changes the store paths of derivations (since the
derivation aterms are added using addTextToStore), but not most
outputs (unless they use builtins.toFile).
important to get garbage collection to work if there is any
inconsistency in the database (because the referrer table is used to
determine whether it is safe to delete a path).
* `nix-store --verify': show some progress.
from a source directory. All files for which a predicate function
returns true are copied to the store. Typical example is to leave
out the .svn directory:
stdenv.mkDerivation {
...
src = builtins.filterSource
(path: baseNameOf (toString path) != ".svn")
./source-dir;
# as opposed to
# src = ./source-dir;
}
This is important because the .svn directory influences the hash in
a rather unpredictable and variable way.
matters when running as root, since then we don't use the setuid
helper (which already used lchown()).
* Also check for an obscure security problem on platforms that don't
have lchown. Then we can't change the ownership of symlinks, which
doesn't matter *except* when the containing directory is writable by
the owner (which is the case with the top-level Nix store directory).
* Throw more exceptions as BuildErrors instead of Errors. This
matters when --keep-going is turned on. (A BuildError is caught
and terminates the goal in question, an Error terminates the
program.)
seconds without producing output on stdout or stderr (NIX-65). This
timeout can be specified using the `--max-silent-time' option or the
`build-max-silent-time' configuration setting. The default is
infinity (0).
* Fix a tricky race condition: if we kill the build user before the
child has done its setuid() to the build user uid, then it won't be
killed, and we'll potentially lock up in pid.wait(). So also send a
conventional kill to the child.
that have to be done as root: running builders under different uids,
changing ownership of build results, and deleting paths in the store
with the wrong ownership).
`nix-store --delete'. But unprivileged users are not allowed to
ignore liveness.
* `nix-store --delete --ignore-liveness': ignore the runtime roots as
well.
process, so forward the operation.
* Spam the user about GC misconfigurations (NIX-71).
* findRoots: skip all roots that are unreadable - the warnings with
which we spam the user should be enough.
processes can register indirect roots. Of course, there is still
the problem that the garbage collector can only read the targets of
the indirect roots when it's running as root...
* SIGIO -> SIGPOLL (POSIX calls it that).
* Use sigaction instead of signal to register the SIGPOLL handler.
Sigaction is better defined, and a handler registered with signal
appears not to interrupt fcntl(..., F_SETLKW, ...), which is bad.
via the Unix domain socket in /nix/var/nix/daemon.socket. The
server forks a worker process per connection.
* readString(): use the heap, not the stack.
* Some protocol fixes.
* Added `build-users-group', the group under which builds are to be
performed.
* Check that /nix/store has 1775 permission and is owner by the
build-users-group.
mode. Presumably nix-worker would be setuid to the Nix store user.
The worker performs all operations on the Nix store and database, so
the caller can be completely unprivileged.
This is already much more secure than the old setuid scheme, since
the worker doesn't need to do Nix expression evaluation and so on.
Most importantly, this means that it doesn't need to access any user
files, with all resulting security risks; it only performs pure
store operations.
Once this works, it is easy to move to a daemon model that forks off
a worker for connections established through a Unix domain socket.
That would be even more secure.
* Some refactoring: put the NAR archive integer/string serialisation
code in a separate file so it can be reused by the worker protocol
implementation.
containing functions that operate on the Nix store. One
implementation is LocalStore, which operates on the Nix store
directly. The next step, to enable secure multi-user Nix, is to
create a different implementation RemoteStore that talks to a
privileged daemon process that uses LocalStore to perform the actual
operations.
