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Merge pull request #14651 from NixOS/restore-sink-more-openat2

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libutil: Use openFileEnsureBeneathNoSymlinks in RestoreSink::createRe…
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John Ericson 2025-11-26 01:45:50 +00:00 • committed by GitHub
commit c38349583f
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4 changed files with 10 additions and 1 deletions
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4
src/libutil-tests/file-system.cc
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@ -351,6 +351,10 @@ TEST(openFileEnsureBeneathNoSymlinks, works)
sink.createDirectory(
CanonPath("a/b/c/f"), [](FileSystemObjectSink & dirSink, const CanonPath & relPath) {}),
SymlinkNotAllowed);
ASSERT_THROW(
sink.createRegularFile(
CanonPath("a/b/c/regular"), [](CreateRegularFileSink & crf) { crf("some contents"); }),
SymlinkNotAllowed);
}
AutoCloseFD dirFd = openDirectory(tmpDir);

2
src/libutil/fs-sink.cc
View file

@ -170,7 +170,7 @@ void RestoreSink::createRegularFile(const CanonPath & path, std::function<void(C
constexpr int flags = O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC;
if (!dirFd)
return ::open(p.c_str(), flags, 0666);
return ::openat(dirFd.get(), path.rel_c_str(), flags, 0666);
return unix::openFileEnsureBeneathNoSymlinks(dirFd.get(), path, flags, 0666);
}();
#endif
;

2
src/libutil/include/nix/util/file-descriptor.hh
View file

@ -263,6 +263,8 @@ struct SymlinkNotAllowed : public Error
* @param flags O_* flags
* @param mode Mode for O_{CREAT,TMPFILE}
*
* @pre path.isRoot() is false
*
* @throws SymlinkNotAllowed if any path components
*/
Descriptor openFileEnsureBeneathNoSymlinks(Descriptor dirFd, const CanonPath & path, int flags, mode_t mode = 0);

3
src/libutil/unix/file-descriptor.cc
View file

@ -269,6 +269,7 @@ openFileEnsureBeneathNoSymlinksIterative(Descriptor dirFd, const CanonPath & pat
{
AutoCloseFD parentFd;
auto nrComponents = std::ranges::distance(path);
assert(nrComponents >= 1);
auto components = std::views::take(path, nrComponents - 1); /* Everything but last component */
auto getParentFd = [&]() { return parentFd ? parentFd.get() : dirFd; };
@ -320,6 +321,8 @@ openFileEnsureBeneathNoSymlinksIterative(Descriptor dirFd, const CanonPath & pat
Descriptor unix::openFileEnsureBeneathNoSymlinks(Descriptor dirFd, const CanonPath & path, int flags, mode_t mode)
{
assert(!path.rel().starts_with('/')); /* Just in case the invariant is somehow broken. */
assert(!path.isRoot());
#ifdef __linux__
auto maybeFd = linux::openat2(
dirFd, path.rel_c_str(), flags, static_cast<uint64_t>(mode), RESOLVE_BENEATH | RESOLVE_NO_SYMLINKS);