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Previously, system call filtering (to prevent builders from storing files with
setuid/setgid permission bits or extended attributes) was performed using a
blocklist. While this looks simple at first, it actually carries significant
security and maintainability risks: after all, the kernel may add new syscalls
to achieve the same functionality one is trying to block, and it can even be
hard to actually add the syscall to the blocklist when building against a C
library that doesn't know about it yet. For a recent demonstration of this
happening in practice to Nix, see the introduction of fchmodat2 [0] [1].
The allowlist approach does not share the same drawback. While it does require
a rather large list of harmless syscalls to be maintained in the codebase,
failing to update this list (and roll out the update to all users) in time has
rather benign effects; at worst, very recent programs that already rely on new
syscalls will fail with an error the same way they would on a slightly older
kernel that doesn't support them yet. Most importantly, no unintended new ways
of performing dangerous operations will be silently allowed.
Another possible drawback is reduced system call performance due to the larger
filter created by the allowlist requiring more computation [2]. However, this
issue has not convincingly been demonstrated yet in practice, for example in
systemd or various browsers. To the contrary, it has been measured that the the
actual filter constructed here has approximately the same overhead as a very
simple filter blocking only one system call.
This commit tries to keep the behavior as close to unchanged as possible. The
system call list is in line with libseccomp 2.5.5 and glibc 2.39, which are the
latest versions at the point of writing. Since libseccomp 2.5.5 is already a
requirement and the distributions shipping this together with older versions of
glibc are mostly not a thing any more, this should not lead to more build
failures any more.
[0] https://github.com/NixOS/nixpkgs/issues/300635
[1] https://github.com/NixOS/nix/issues/10424
[2] https://github.com/flatpak/flatpak/pull/4462#issuecomment-1061690607
Change-Id: I541be3ea9b249bcceddfed6a5a13ac10b11e16ad
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In f047e4357b4f7ad66c2e476506bf35cab82e441e, I missed the behavior that if
building without a dedicated build user (i.e. in single-user setups), seccomp
setup failures are silently ignored. This was introduced without explanation 7
years ago (ff6becafa8efc2f7e6f2b9b889ba4adf20b8d524). Hopefully the only
use-case nowadays is causing spurious test suite successes when messing up the
seccomp filter during development. Let's try removing it.
Change-Id: Ibe51416d9c7a6dd635c2282990224861adf1ceab
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Musl stdout macro expands¹ to something that isn't a valid identifier,
so we get syntax errors when compiling usage of a method called stdout
with Musl's stdio.h.
[1]: https://git.musl-libc.org/cgit/musl/tree/include/stdio.h?id=ab31e9d6a0fa7c5c408856c89df2dfb12c344039#n67
Change-Id: I10e6f6a49504399bf8edd59c5d9e4e62449469e8
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This is slightly more type safe and is more in line with modern C++.
Change-Id: Ia7a8df1c7788085020d1bdc941d6f9cee356144e
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Use libprocstat to find garbage collector roots on FreeBSD.
Tested working on a FreeBSD machine, although there is no CI yet
Change-Id: Id36bac8c3de6cc4de94e2d76e9663dd4b76068a9
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Error is pretty large, and most goals do not fail. this alone more than
halves the size of Goal on x86_64-linux, from 720 bytes down to 344. in
derived classes the difference is not as dramatic, but even the largest
derived class (`LocalDerivationGoal`) loses almost 20% of its footprint
Change-Id: Ifda8f94c81b6566eeb3e52d55d9796ec40c7bce8
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Change-Id: I3c7f17d5492a16bb54480fa1aa384b96fba72d61
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the goals are either already using std::async and merely forgot to
remove std::thread vestiges or they emulate async with threads and
promises. we can simply use async directly everywhere for clarity.
Change-Id: I3f05098310a25984f10fff1e68c573329002b500
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under owner_less it's equivalent to insert(), only sometimes a little
bit faster because it does not construct a weak_ptr if the goal is in
the set already. this small difference in performance does not matter
here and c++23 will make insert transparent anyway, so we can drop it
Change-Id: I7cbd7d6e0daa95d67145ec58183162f6c4743b15
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this should be an optional. "busy" is not an *exit* code!
Change-Id: Ic231cb27b022312b1a7a7b9602f32845b7a9c934
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Change-Id: Ia3ebd434b17052b6760ce74d8e20025a72148613
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*accidentally* overriding a function is almost guaranteed to be an
error. overriding a function without labeling it as such is merely
bad style, but bad style that makes the code harder to understand.
Change-Id: Ic0594f3d1604ab6b3c1a75cb5facc246effe45f0
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decompression" into main
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it" into main
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Due to a leftover from a previous version where the buffer was allocated on the
stack, the change introduced in commit 4ec87742a196d8ed8f41b41ef039706ce791448d
accidentally passes the size of a pointer as the size of the buffer to the
decompressor. Since the former is much smaller (usually 8 bytes instead of 64
kilobytes), this is safe, but leads to considerable overhead; most notably, due
to excessive progress reports, which happen for each chunk. Pass the proper
buffer size instead.
Change-Id: If4bf472d33e21587acb5235a2d99e3cb10914633
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SimpleLogger is not fully thread-safe, and all loggers that wrap it are
also not safe accordingly. this does not affect much, but in rare cases
it can cause interleaving of messages on stderr when used with the json
or raw log formats. the fix applied here is a bit of a hack, but fixing
this properly requires rearchitecting the logger infrastructure. nested
loggers are not the most natural abstraction here, and it is biting us.
Change-Id: Ifbf34fe1e85c60e73b59faee50e7411c7b5e7c12
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If useChroot = false, and user namespaces aren't available for some
reason (e.g. within a Docker container), this fixes a pointless warning
being emitted, as we would never attempt to use them even if they were
available.
Change-Id: Ibcee91c088edd2cd19e70218d5a5802bff8f537b
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This removes a *whole load* of variables from scope and enforces thread
boundaries with the type system.
There is not much change of significance in here, so the things to watch
out for while reviewing it are primarily that the destructor ordering
may have changed inadvertently, I think.
Change-Id: I3cd87e6d5a08dfcf368637407251db22a8906316
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(plus one reference to CppNix github)
Change-Id: Id8b3d2897f3b54e286861805cfd421adc4d5de47
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Change-Id: Id1ee0d2ad4a3774f4bbb960d76f0f76ac4f3eff9
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we no longer need these since we're no longer using sinks to serialize things.
Change-Id: Iffb1a3eab33c83f611c88fa4e8beaa8d5ffa079b
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this is cursed. deeply and profoundly cursed. under NO CIRCUMSTANCES
must protocol serializer helpers be applied to temporaries! doing so
will inevitably cause dangling references and cause the entire thing
to crash. we need to do this even so to get rid of boost coroutines,
and likewise to encapsulate the serializers we suffer today at least
a little bit to allow a gradual migration to an actual IPC protocol.
(this isn't a problem that's unique to generators. c++ coroutines in
general cannot safely take references to arbitrary temporaries since
c++ does not have a lifetime system that can make this safe. -sigh-)
Change-Id: I2921ba451e04d86798752d140885d3c5cc08e146
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this doesn't have a test because this code path is only reached by
clients that predate 2.4, and we really should not be caring about
those any more right now. even the test suite doesn't, and the few
tests that might care are disabled because they will not even work
Change-Id: Id9eb190065138fedb2c7d90c328ff9eb9d97385b
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Change-Id: Ifa783c2c65c06ddd1d0212016d5bfd07666ea91c
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This also bans various sneaking of negative numbers from the language
into unsuspecting builtins as was exposed while auditing the
consequences of changing the Nix language integer type to a newtype.
It's unlikely that this change comprehensively ensures correctness when
passing integers out of the Nix language and we should probably add a
checked-narrowing function or something similar, but that's out of scope
for the immediate change.
During the development of this I found a few fun facts about the
language:
- You could overflow integers by converting from unsigned JSON values.
- You could overflow unsigned integers by converting negative numbers
into them when going into Nix config, into fetchTree, and into flake
inputs.
The flake inputs and Nix config cannot actually be tested properly
since they both ban thunks, however, we put in checks anyway because
it's possible these could somehow be used to do such shenanigans some
other way.
Note that Lix has banned Nix language integer overflows since the very
first public beta, but threw a SIGILL about them because we run with
-fsanitize=signed-overflow -fsanitize-undefined-trap-on-error in
production builds. Since the Nix language uses signed integers, overflow
was simply undefined behaviour, and since we defined that to trap, it
did.
Trapping on it was a bad UX, but we didn't even entirely notice
that we had done this at all until it was reported as a bug a couple of
months later (which is, to be fair, that flag working as intended), and
it's got enough production time that, aside from code that is IMHO buggy
(and which is, in any case, not in nixpkgs) such as
https://git.lix.systems/lix-project/lix/issues/445, we don't think
anyone doing anything reasonable actually depends on wrapping overflow.
Even for weird use cases such as doing funny bit crimes, it doesn't make
sense IMO to have wrapping behaviour, since two's complement arithmetic
overflow behaviour is so *aggressively* not what you want for *any* kind
of mathematics/algorithms. The Nix language exists for package
management, a domain where bit crimes are already only dubiously in
scope to begin with, and it makes a lot more sense for that domain for
the integers to never lose precision, either by throwing errors if they
would, or by being arbitrary-precision.
This change will be ported to CppNix as well, to maintain language
consistency.
Fixes: https://git.lix.systems/lix-project/lix/issues/423
Change-Id: I51f253840c4af2ea5422b8a420aa5fafbf8fae75
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The actual motive here is the avoidance of integer overflow if we were
to make these use checked NixInts and retain the subtraction.
However, the actual *intent* of this code is a three-way comparison,
which can be done with operator<=>, so we should just do *that* instead.
Change-Id: I7f9a7da1f3176424b528af6d1b4f1591e4ab26bf
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upcast_goal was only ever needed to break circular includes, but the
same solution that gave us upcast_goal also lets us fully remove it:
just upcast goals without a wrapper function, but only in .cc files.
Change-Id: I9c71654b2535121459ba7dcfd6c5da5606904032
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Change-Id: Id452f6a03faa1037ff13af0f63e32883966ff40d
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the sole remaining user of this function can use makeDecompressionSource
instead, while making the sinkToSource in the caller unnecessary as well
Change-Id: I4258227b5dbbb735a75b477d8a57007bfca305e9
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this lets us remove the last true remaining uses of
makeDecompressionSink.
Change-Id: I146ca2bbe1a9ae9a367117a7b8a304b23a63e5e2
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the rewriting sink was just broken. when given a rewrite set that
contained a key that is also a proper infix of another key it was
possible to produce an incorrectly rewritten result if the writer
used the wrong block size. fixing this duplicates rewriteStrings,
to avoid this we'll rewrite rewriteStrings to use RewritingSource
in a new mode that'll allow rewrites we had previously forbidden.
Change-Id: I57fa0a9a994e654e11d07172b8e31d15f0b7e8c0
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This rather simple function existed just to check some flags,
but the response varies by platform. This is a perfect case for
our subclasses.
Change-Id: Ieb1732a8d024019236e0d0028ad843a24ec3dc59
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Change-Id: I5878007502fa68c2816a0f4c61f7d0e60bdde702
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this much more closely mimics what is actually happening: we're reading
data from somewhere else, actively, rather than passively waiting. with
the data flow matching the underlying system interactions better we can
remove a few sinkToSource calls that merely exists to undo the mismatch
caused by not treating subprocess output as a data source to begin with
Change-Id: If4abfc2f8398fb5e88c9b91a8bdefd5504bb2d11
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this will let us also return a source for the program output later,
which will in turn make sinkToSource unnecessary for program output
processing. this may also reopen a path for provigin program input,
but that still needs a proper async io framework to avoid problems.
Change-Id: Iaf93f47db99c38cfaf134bd60ed6a804d7ddf688
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Change-Id: I5f92b15fd367d46eb047d74ab6e317b4f51a46d3
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Change-Id: Ic4cf5562504aa29130304469936f958c0426e5ef
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Add a platform-specific function for starting sandboxed child.
Generally this just means startProcess, but on Linux we use flags
for clone to start a new namespace
Change-Id: I41c8aba62676a162388bbe5ab8a7518904c7b058
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Add a new OS-specific hook called `prepareSandbox`, run before forking
On Darwin this is empty as nothing is required,
on Linux this creates the chroot directory and adds basic files,
and on platforms using a fallback this throws an exception
Change-Id: Ie30c38c387f2e0e5844b2afa32fd4d33b1180dae
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generators are a better basis for serializers than streaming into sinks
as we do currently for many reasons, such as being usable as sources if
one wishes to (without requiring an intermediate sink to serialize full
data sets into memory, or boost coroutines to turn sinks into sources),
composing more naturally (as one can just yield a sub-generator instead
of being forced to wrap entire substreams into clunky functions or even
more clunky custom types to implement operator<< on), allowing wrappers
to transform data with clear ownership semantics (removing the need for
explicit memory allocations and Source wrappers), and many other things
Change-Id: I361d89ff556354f6930d9204f55117565f2f7f20
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Since Ifa0adda7984e, we don't use this code anymore on macOS, so we have
no reason to have a knob to disable it anymore.
Change-Id: Ie29a8a8978d9aefd4551895f4f9b3cc0827496df
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This is a shameless layering violation in favour of UX. It falls back
trivially to "unknown", so it's purely a UX feature.
Diagnostic sample:
```
error: hash mismatch in fixed-output derivation '/nix/store/sjfw324j4533lwnpmr5z4icpb85r63ai-x1.drv':
likely URL: https://meow.puppy.forge/puppy.tar.gz
specified: sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
got: sha256-a1Qvp3FOOkWpL9kFHgugU1ok5UtRPSu+NwCZKbbaEro=
```
Change-Id: I873eedcf7984ab23f57a6754be00232b5cb5b02c
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This is a squash of upstream PRs #10303, #10312 and #10883.
fix: Treat empty TMPDIR as unset
Fixes an instance of
nix: src/libutil/util.cc:139: nix::Path nix::canonPath(PathView, bool): Assertion `path != ""' failed.
... which I've been getting in one of my shells for some reason.
I have yet to find out why TMPDIR was empty, but it's no reason for
Nix to break.
(cherry picked from commit c3fb2aa1f9d1fa756dac38d3588c836c5a5395dc)
fix: Treat empty XDG_RUNTIME_DIR as unset
See preceding commit. Not observed in the wild, but is sensible
and consistent with TMPDIR behavior.
(cherry picked from commit b9e7f5aa2df3f0e223f5c44b8089cbf9b81be691)
local-derivation-goal.cc: Reuse defaultTempDir()
(cherry picked from commit fd31945742710984de22805ee8d97fbd83c3f8eb)
fix: remove usage of XDG_RUNTIME_DIR for TMP
(cherry picked from commit 1363f51bcb24ab9948b7b5093490a009947f7453)
tests/functional: Add count()
(cherry picked from commit 6221770c9de4d28137206bdcd1a67eea12e1e499)
Remove uncalled for message
(cherry picked from commit b1fe388d33530f0157dcf9f461348b61eda13228)
Add build-dir setting
(cherry picked from commit 8b16cced18925aa612049d08d5e78eccbf0530e4)
Change-Id: Ic7b75ff0b6a3b19e50a4ac8ff2d70f15c683c16a
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Change-Id: Icc8a15090c77f54ea7d9220aadedcd4a19922814
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copy-constructing or assigning from pid_t can easily lead to duplicate
Pid instances for the same process if a pid_t was used carelessly, and
Pid itself was copy-constructible. both could cause surprising results
such as killing processes twice (which could become very problemantic,
but luckily modern systems don't reuse PIDs all that quickly), or more
than one piece of the code believing it owns a process when neither do
Change-Id: Ifea7445f84200b34c1a1d0acc2cdffe0f01e20c6
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Change-Id: I3137cc140590001fe7ba542844e735944a0a9255
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this is only used in one place, and only to set a nicer error message on
EndOfFile. the only caller that actually *catches* this exception should
provide an error message in that catch block rather than forcing support
for setting error message so deep into the stack. copyStorePath is never
called outside of PathSubstitutionGoal anyway, which catches everything.
Change-Id: Ifbae8706d781c388737706faf4c8a8b7917ca278
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LocalDerivationGoal includes a large number of low-level sandboxing
primitives for Darwin and Linux, intermingled with ifdefs.
Start creating platform-specific classes to make it easier to add new
platforms and review platform-specific code.
This change only creates support infrastructure and moves two function,
more functions will be moved in future changes.
Change-Id: I9fc29fa2a7345107d4fc96c46fa90b4eabf6bb89
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