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.
graph to be passed to a builder. This attribute should be a list of
pairs [name1 path1 name2 path2 ...]. The references graph of each
`pathN' will be stored in a text file `nameN' in the temporary build
directory. The text files have the format used by `nix-store
--register-validity'. However, the deriver fields are left empty.
`exportReferencesGraph' is useful for builders that want to do
something with the closure of a store path. Examples: the builders
that make initrds and ISO images for NixOS.
`exportReferencesGraph' is entirely pure. It's necessary because
otherwise the only way for a builder to get this information would
be to call `nix-store' directly, which is not allowed (though
unfortunately possible).
available. For instance,
$ nix-store -l $(which svn) | less
lets you read the build log of the Subversion instance in your
profile.
* `nix-store -qb': if applied to a non-derivation, take the deriver.
check that the references of the output of a derivation are in the
specified set. For instance,
allowedReferences = [];
specifies that the output cannot have any references. (This is
useful, for instance, for the generation of bootstrap binaries for
stdenv-linux, which must not have any references for purity). It
could also be used to guard against undesired runtime dependencies,
e.g.,
{gcc, dynlib}: derivation {
...
allowedReferences = [dynlib];
}
says that the output can refer to the path of `dynlib' but not
`gcc'. A `forbiddedReferences' attribute would be more useful for
this, though.
concatenation and string coercion. This was a big mess (see
e.g. NIX-67). Contexts are now folded into strings, so that they
don't cause evaluation errors when they're not expected. The
semantics of paths has been clarified (see nixexpr-ast.def).
toString() and coerceToString() have been merged.
Semantic change: paths are now copied to the store when they're in a
concatenation (and in most other situations - that's the
formalisation of the meaning of a path). So
"foo " + ./bla
evaluates to "foo /nix/store/hash...-bla", not "foo
/path/to/current-dir/bla". This prevents accidental impurities, and
is more consistent with the treatment of derivation outputs, e.g.,
`"foo " + bla' where `bla' is a derivation. (Here `bla' would be
replaced by the output path of `bla'.)
Nix-env failed to call addPermRoot(), which is necessary to safely
add a new root. So if nix-env started after and finished before the
garbage collector, the user environment (plus all other new stuff)
it built might be garbage collected, leading to a dangling symlink
chain in ~/.nix-profile...
* Be more explicit if we block on the GC lock ("waiting for the big
garbage collector lock...").
* Don't loop trying to create a new generation. It's not necessary
anymore since profiles are locked nowadays.
writable. File permissions on Cygwin are rather complex, and in this
case this check introduced a problem with build jobs invoke from
outside of Cygwin (MSYS). It seemed almost impossible to fix the
permissions of the directory, so for now this safety check is disabled
on Cygwin.
the disk is full (because to delete something from the Nix store, we
need a Berkeley DB transaction, which takes up disk space). Under
normal operation, we make sure that there exists a file
/nix/var/nix/db/reserved of 1 MB. When running the garbage
collector, we delete that file before we open the Berkeley DB
environment.
creates a new process group but also a new session. New sessions
have no controlling tty, so child processes like ssh cannot open
/dev/tty (which is bad).
intended). This ensures that any ssh child processes to remote
machines are also killed, and thus the Nix process on the remote
machine also exits. Without this, the remote Nix process will
continue until it exists or until its stdout buffer gets full and it
locks up. (Partially fixes NIX-35.)
deletes a path even if it is reachable from a root. However, it
won't delete a path that still has referrers (since that would
violate store invariants).
Don't try this at home. It's a useful hack for recovering from
certain situations in a somewhat clean way (e.g., holes in closures
due to disk corruption).
nix-store query options `--referer' and `--referer-closure' have
been changed to `--referrer' and `--referrer-closure' (but the old
ones are still accepted for compatibility).
mapping. The referer table is replaced by a referrer table (note
spelling fix) that stores each referrer separately. That is,
instead of having
referer[P] = {Q_1, Q_2, Q_3, ...}
we store
referer[(P, Q_1)] = ""
referer[(P, Q_2)] = ""
referer[(P, Q_3)] = ""
...
To find the referrers of P, we enumerate over the keys with a value
lexicographically greater than P. This requires the referrer table
to be stored as a B-Tree rather than a hash table.
(The tuples (P, Q) are stored as P + null-byte + Q.)
Old Nix databases are upgraded automatically to the new schema.
builder. Instead, require that the Nix store has sticky permission
(S_ISVTX); everyone can created files in the Nix store, but they
cannot delete, rename or modify files created by others.
root (or setuid root), then builds will be performed under one of
the users listed in the `build-users' configuration variables. This
is to make it impossible to influence build results externally,
allowing locally built derivations to be shared safely between
users (see ASE-2005 paper).
To do: only one builder should be active per build user.
derivations. This is mostly to simplify the implementation of
nix-prefetch-{url, svn}, which now work properly in setuid
installations.
* Enforce valid store names in `nix-store --add / --add-fixed'.
continue building when one fails unless `--keep-going' is
specified.
* When `--keep-going' is specified, print out the set of failing
derivations at the end (otherwise it can be hard to find out which
failed).
multiple times is also a top-level goal, then the second and later
instantiations would never be created because there would be a
stable pointer to the first one that would keep it alive in the
WeakGoalMap.
* Some tracing code for debugging this kind of problem.
user environment, e.g.,
$ nix-env -i /nix/store/z58v41v21xd3ywrqk1vmvdwlagjx7f10-aterm-2.3.1.drv
or
$ nix-env -i /nix/store/hsyj5pbn0d9iz7q0aj0fga7cpaadvp1l-aterm-2.3.1
This is useful because it allows Nix expressions to be bypassed
entirely. For instance, if only a nix-pull manifest is provided,
plus the top-level path of some component, it can be installed
without having to supply the Nix expression (e.g., for obfuscation,
or to be independent of Nix expression language changes or context
dependencies).
to derivations in user environments. Nice for developers (since it
prevents build-time-only dependencies from being GC'ed, in
conjunction with `gc-keep-outputs'). Turned off by default.
* Removed some dead code (successor stuff) from nix-push.
* Updated terminology in the tests (store expr -> drv path).
* Check that the deriver is set properly in the tests.
for finding build-time dependencies (possibly after a build). E.g.,
$ nix-store -qb aterm $(nix-store -qd $(which strc))
/nix/store/jw7c7s65n1gwhxpn35j9rgcci6ilzxym-aterm-2.3.1
* Arguments to nix-store can be files within store objects, e.g.,
/nix/store/jw7c...-aterm-2.3.1/bin/baffle.
* Idem for garbage collector roots.
This was necessary becase root finding must be done after
acquisition of the global GC lock.
This makes `nix-collect-garbage' obsolete; it is now just a wrapper
around `nix-store --gc'.
* Automatically remove stale GC roots (i.e., indirect GC roots that
point to non-existent paths).
get rid of GC roots. Nix-build places a symlink `result' in the
current directory. Previously, removing that symlink would not
remove the store path being linked to as a GC root. Now, the GC
root created by nix-build is actually a symlink in
`/nix/var/nix/gcroots/auto' to `result'. So if that symlink is
removed the GC root automatically becomes invalid (since it can no
longer be resolved). The root itself is not automatically removed -
the garbage collector should delete dangling roots.
immediately add the result as a permanent GC root. This is the only
way to prevent a race with the garbage collector. For instance, the
old style
ln -s $(nix-store -r $(nix-instantiate foo.nix)) \
/nix/var/nix/gcroots/result
has two time windows in which the garbage collector can interfere
(by GC'ing the derivation and the output, respectively). On the
other hand,
nix-store --add-root /nix/var/nix/gcroots/result -r \
$(nix-instantiate --add-root /nix/var/nix/gcroots/drv \
foo.nix)
is safe.
* nix-build: use `--add-root' to prevent GC races.
being created after the garbage collector has read the temproots
directory. This blocks the creation of new processes, but the
garbage collector could periodically release the GC lock to allow
them to run.
that they are deleted in an order that maintains the closure
invariant.
* Presence of a path in a temporary roots file does not imply that all
paths in its closure are also present, so add the closure.
roots to a per-process temporary file in /nix/var/nix/temproots
while holding a write lock on that file. The garbage collector
acquires read locks on all those files, thus blocking further
progress in other Nix processes, and reads the sets of temporary
roots.
though). In particular it's now much easier to register a GC root.
Just place a symlink to whatever store path it is that you want to
keep in /nix/var/nix/gcroots.
This simplifies garbage collection and `nix-store --query
--requisites' since we no longer need to treat derivations
specially.
* Better maintaining of the invariants, e.g., setReferences() can only
be called on a valid/substitutable path.
closure of the referers relation rather than the references
relation, i.e., the set of all paths that directly or indirectly
refer to the given path. Note that contrary to the references
closure this set is not fixed; it can change as paths are added to
or removed from the store.
promise :-) This allows derivations to specify on *what* output
paths of input derivations they are dependent. This helps to
prevent unnecessary downloads. For instance, a build might be
dependent on the `devel' and `lib' outputs of some library
component, but not the `docs' output.
graph. That is, `nix-store --query --references PATH' shows the set
of paths referenced by PATH, and `nix-store --query --referers PATH'
shows the set of paths referencing PATH.
`derivations.cc', etc.
* Store the SHA-256 content hash of store paths in the database after
they have been built/added. This is so that we can check whether
the store has been messed with (a la `rpm --verify').
* When registering path validity, verify that the closure property
holds.
representation of closures as ATerms in the Nix store. Instead, the
file system pointer graph is now stored in the Nix database. This
has many advantages:
- It greatly simplifies the implementation (we can drop the notion
of `successors', and so on).
- It makes registering roots for the garbage collector much easier.
Instead of specifying the closure expression as a root, you can
simply specify the store path that must be retained as a root.
This could not be done previously, since there was no way to find
the closure store expression containing a given store path.
- Better traceability: it is now possible to query what paths are
referenced by a path, and what paths refer to a path.
