install: verify the gzip trailer of package tarballs

[robobun]

Problem

• bun install installs a package tarball whose gzip trailer (CRC32, ISIZE) does not match the data. A stored-block tarball with one flipped payload byte installs with exit code 0 and 1 package installed. bun 1.3.14 rejected it with error: ZlibError decompressing. GNU tar and npm reject it.
• The cause is install: let libarchive gunzip buffered tarballs instead of inflating into memory #36541. It replaced the in-memory zlib fallback with libarchive's streaming gzip filter. That filter's consume_trailer (vendor archive_read_support_filter_gzip.c) has upstream's XXX TODO: Verify the length and CRC and consumes the 8 trailer bytes without a check. src/install/extract_tarball.rs also treated a libdeflate BadData result as a reason to fall back to that filter.
• Registry installs with dist.integrity are not affected: the sha512 check runs before extraction. The exposed paths are file: tarballs, tarball URLs, github tarballs on first install, manifests without dist.integrity, and --no-verify.

Fix

• patches/libarchive/gzip-verify-trailer.patch: the gzip filter now accumulates CRC32 and the member size over every inflate call and compares them with the trailer in consume_trailer. A mismatch returns ARCHIVE_FATAL. Both install paths treat that as a failed extract: the buffered path and the registry streaming path (TarballStream.rs).
• extract_tarball.rs: a libdeflate BadData or ShortOutput result is now an install error (Corrupt gzip data decompressing ...). InsufficientSpace still streams, because ISIZE is only the size mod 2^32.
• The buffered extract body moved into extract_into. If the extract or the move into the cache fails, the temp extraction directory is removed. On a bad trailer the whole package was already extracted into it, so without this the failure leaked a full copy per attempt.
• Verified: test/cli/install/bun-install-tarball-integrity.test.ts (5 new tests, 4 fail on 1.4.3) and the GitHub root-directory refusal test in symlink-path-traversal.test.ts (now asserts an empty temp dir, fails on 1.4.3). Also bun-install-streaming-extract, bun-install-registry, bun-install-git-deps, bun-add, bun-pack, and test/js/bun/archive.test.ts.

Background

• A gzip member ends with an 8 byte trailer: CRC32 of the uncompressed data and ISIZE, the uncompressed size mod 2^32. A deflate stream has no integrity check of its own, so the trailer is the only thing that catches a flipped byte inside a stored block.
• vendor/libarchive is fetched from a pinned tarball at build time and patched with the files in patches/libarchive (applied with git apply). The list lives in scripts/build/deps/libarchive.ts. This adds one more patch.
• The install extract path tries libdeflate in memory when ISIZE is under 64 MB. libdeflate verifies the trailer itself. Anything else, or a libdeflate failure, goes through libarchive's gzip read filter.

Notes

Repro (any bun 1.4.x, offline):

T=$(mktemp -d); cd $T
python3 - <<'PY'
import tarfile, io, gzip, json
raw = io.BytesIO()
with tarfile.open(fileobj=raw, mode="w") as t:
    for name, data in [("package/package.json", json.dumps({"name":"lpk","version":"1.0.0"}).encode()),
                       ("package/index.js", b'module.exports = "lpk@1.0.0:GOOD";\n')]:
        i = tarfile.TarInfo(name); i.size = len(data); t.addfile(i, io.BytesIO(data))
g = bytearray(gzip.compress(raw.getvalue(), compresslevel=0, mtime=0))
i = g.find(b'module.exports'); g[i+18] ^= 0x04
open("lpk-flip.tgz", "wb").write(bytes(g))
PY
gzip -t lpk-flip.tgz   # invalid compressed data--crc error
mkdir p && cd p && printf '{"name":"p","dependencies":{"lpk":"file:%s/lpk-flip.tgz"}}' $T > package.json
bun install; cat node_modules/lpk/index.js   # before: rc 0, "hpk@1.0.0:GOOD"

After the fix:

• default path: error: Corrupt gzip data decompressing "lpk" to ".xxx-1.lpk", rc 1.
• BUN_FEATURE_FLAG_NO_LIBDEFLATE=1 or an ISIZE of 100 MB (forces the streaming path): error: Fail extracting tarball from lpk, rc 1.
• a 300 KB tarball with a byte flipped in the middle of the deflate stream fails on both paths.
• a valid tarball with a wrong ISIZE (1000) goes libdeflate InsufficientSpace, then streaming, then fails on the ISIZE check, like gzip -t.

The tar reader is opened with read_concatenated_archives, so it reads through the end-of-archive blocks to the end of the gzip member. consume_trailer therefore always runs, and the check is not skipped by an early tar EOF.

The CRC is accumulated once per inflate call over the bytes it produced. The ARCHIVE_RETRY paths added by nonblocking-read.patch return before the next inflate, so a retry does not double count. member_isize is reset in consume_header for each member.

The streaming path (TarballStream.rs) already removed its temp directory on failure. The buffered path did not. The new tests set BUN_TMPDIR inside the temp dir and assert it is empty after a failed install.

The branch is rebased on main after #42523 (libarchive 3.8.7 to 3.8.9). libarchive 3.8.9 renamed the gzip filter's state struct and its variables, so the patch written for 3.8.7 did not apply any more and is regenerated against 3.8.9. Upstream 3.8.9 still has the XXX TODO and still does not verify the trailer.

The fifth test covers a tar whose end-of-archive blocks end exactly on the 64 KiB boundary of the filter's output buffer. Both install paths open the tar reader with read_concatenated_archives, so the reader continues to the end of the gzip member and the trailer check runs in that case too.

Bun.Archive uses the same filter, so it sees the new error too. extract() rejects. files() rejects when the error lands in a data read, which is the common case. If the last entry's data ends exactly on a 64 KiB filter block, the error lands in archive_read_next_header, and files() still resolves: the loops in src/runtime/api/Archive.rs stop on any result that is not a success, and treat a fatal error like the end of the archive. That is an existing defect (a truncated tar.gz with the same alignment resolves with a partial file list on main today). It is tracked separately and is not changed here.

The three tests that must go through libarchive (BUN_FEATURE_FLAG_NO_LIBDEFLATE=1, or an ISIZE of 100 MB) also assert that stderr has no Corrupt gzip data. Only the libdeflate path logs that text, so its absence shows that libarchive's trailer check rejected the tarball.

The success path still leaves a temp directory behind when the cache already has the package and BUN_TMPDIR is set (renameat_concurrently_a, step 2b in its comment). That is unchanged here.

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no test proof · iteration 5 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/cli/install/symlink-path-traversal.test.ts

[robobun]

Status: reproduced with a stored-block tarball with one flipped payload byte (bun 1.4.3 installs it, rc 0). Fix verified on both decompression paths. Self-reviewed: the review asked for honest framing of the reach (registry installs with dist.integrity are unaffected) and a cite of #36541. Both are in the body.

Rebased on main at fd8422c. Main moved libarchive from 3.8.7 to 3.8.9 in #42523. The old gzip-verify-trailer.patch did not apply to 3.8.9 (upstream renamed the filter's state struct), so the patch is regenerated against 3.8.9. Upstream 3.8.9 still does not verify the trailer.

085cbbc answers the latest review:

• The tests that must go through libarchive now assert that the libdeflate path did not handle the tarball.
• The buffered path now also removes the temp directory when the move into the cache fails. The GitHub root-directory refusal test asserts it (fails on 1.4.3).
• Bun.Archive.files() can still resolve when a fatal error lands in archive_read_next_header. That is an existing defect in src/runtime/api/Archive.rs, present on main without this PR, and it is tracked separately. The PR body no longer claims Bun.Archive coverage.

CI on the previous head (build 117303): every build lane passed. The one red test was test/bake/deinitialization.test.ts on alpine aarch64, which this diff does not touch.

[robobun]

^{Updated 4:28 PM PT - Sep 17th, 2026}

✅ @robobun, your commit 085cbbca018edaa70d1945a0cb8b1e0b62342833 passed in Build #117326! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 41503

That installs a local version of the PR into your bun-41503 executable, so you can run:

bun-41503 --bun

[robobun]

Shortened the two new comments around the extract_into call in src/install/extract_tarball.rs. The other flagged comments (lines 307 to 475) are existing comments that moved when the extraction body became extract_into. git diff -w shows the real change there: the temp directory is removed when the extract fails.

[coderabbitai]

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Walkthrough

Changes

Gzip extraction now validates CRC32 and ISIZE trailers. Tarball extraction reports corrupt data, removes failed temporary directories, and preserves existing archive handling. Tests cover valid and corrupted archives across decompression paths.

Gzip tarball integrity

Layer / File(s)	Summary
Gzip trailer validation patches/libarchive/gzip-verify-trailer.patch, scripts/build/deps/libarchive.ts	The gzip filter tracks uncompressed member size and validates CRC32 and ISIZE after consuming the trailer.
Extraction failure handling src/install/extract_tarball.rs	extract_into handles decompression paths, reports corrupt gzip statuses, closes destination handles, and removes failed temporary trees.
Tarball integrity tests test/cli/install/bun-install-tarball-integrity.test.ts	Tests cover valid installation, CRC32 and ISIZE corruption, both extraction paths, failed installation, and temporary-file cleanup.

Suggested reviewers: jarred-sumner

Priority: ➖ Normal

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
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Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: verifying gzip trailers for package tarballs.
Description check	✅ Passed	The description explains the problem, fix, affected paths, implementation details, and verification results. It does not use the exact template headings, but it provides the required information in eq…

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[coderabbitai]

Actionable comments posted: 2

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Inline comments:
In `@patches/libarchive/gzip-verify-trailer.patch`:
- Around line 32-38: Ensure both extraction paths perform a final read/drain of
the gzip filter after the tar reader returns ARCHIVE_EOF, allowing inflate to
reach Z_STREAM_END and consume_trailer to validate the 8-byte trailer before
extraction is accepted. Preserve normal EOF handling while propagating any fatal
drain or trailer-validation error.

In `@test/cli/install/bun-install-tarball-integrity.test.ts`:
- Line 928: Make the cleanup assertion non-vacuous in the tarball integrity
test: create .tmp/.keep in the fixture, remove the catch that converts a missing
directory into an empty result, and exclude .keep from the directory entries
before asserting no leftovers remain. Ensure the fixture sets BUN_TMPDIR so
temporary extraction uses the fixture’s .tmp directory.

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[robobun]

On the drain concern: both install paths open the tar reader with read_concatenated_archives (BufferReadStream::open_read and TarballStream::open_archive). With that option the tar reader does not stop at the null blocks. It keeps reading 512 byte blocks until the gzip filter reports EOF. The filter reports EOF only after inflate returns Z_STREAM_END and consume_trailer succeeds, so the trailer check always runs. d134394 adds a test for the exact case described: a tar whose end-of-archive blocks end on the 64 KiB boundary of the filter's output buffer, with a flipped payload byte, on the streaming path. It fails on bun 1.4.3 and passes with this branch.

The cleanup assertion is no longer vacuous: the fixture creates .tmp/.keep, and the test asserts .tmp holds nothing else after a failed install.

[claude]

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[claude]

Code review found no issues

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[claude]

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

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[claude]

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