https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291567
Bug ID: 291567
Summary: bsdtar produces corrupted gzip/zstd streams when
writing compressed archives to stdout, while the same
commands using -f file create valid archives.
Product: Base System
Version: 15.0-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Many People
Priority: ---
Component: bin
Assignee: [email protected]
Reporter: [email protected]
Summary
bsdtar produces corrupted gzip/zstd streams when writing compressed archives to
stdout, while the same invocations with -f file produce valid archives. This
affects both -z (gzip) and --zstd filters and is reproducible on multiple
FreeBSD releases and architectures.
Environment
FreeBSD 15.0-RELEASE GENERIC amd64
FreeBSD 14.3-RELEASE-p5 GENERIC amd64
FreeBSD 14.3-RELEASE-p5 GENERIC arm64
Common for all systems:
tar, gzip and zstd are from base system.
Steps to reproduce
All commands run in an empty temporary directory, with a synthetic data set:
Generate some test data:
mkdir -p /tmp/bsdtar-test/data
dd if=/dev/urandom of=/tmp/bsdtar-test/data/file.bin bs=1k count=64 status=none
cd /tmp/bsdtar-test
Gzip via stdout (broken):
tar -cz data > stdout-gzip.tgz
gzip -t stdout-gzip.tgz
# gzip reports: "trailing garbage ignored"
Gzip via -f (OK):
tar -cz -f file-gzip.tgz data
gzip -t file-gzip.tgz
# exit status 0, no warnings
Zstd via builtin --zstd + stdout (broken):
tar --zstd -c data > stdout-zstd.tzst
zstd -t stdout-zstd.tzst
# zstd: "unsupported format"
tar -tf stdout-zstd.tzst
# lists some entries, then:
# tar: Truncated input file (...), Error exit delayed from previous errors.
Zstd via builtin --zstd + -f (OK):
tar --zstd -cf file-zstd.tzst data
zstd -t file-zstd.tzst # OK
tar -tf file-zstd.tzst # full listing OK
Zstd via external filter (reference, OK):
tar -c data | zstd -o pipe-zstd.tzst
zstd -t pipe-zstd.tzst # OK
In all cases the stdout‑generated files (stdout-gzip.tgz, stdout-zstd.tzst) are
close in size to their -f counterparts, but are rejected by the native
compressor tools, while the -f and pipe variants are valid.
Actual vs expected behavior
Actual:
tar -cz data > file.tgz: gzip -t reports trailing garbage ignored on
the resulting file.
tar --zstd -c data > file.tzst: zstd -t reports unsupported format; tar
-tf sees some entries and then fails with a truncated archive error.
Using an external compressor (tar -c | gzip, tar -c | zstd) or -f with
the builtin filters always produces valid archives.
Expected:
Writing a compressed archive to stdout (tar -cz data > file, tar --zstd
-c data > file) should produce the same valid gzip/zstd stream as tar -cz -f
file / tar --zstd -cf file.
Additional notes
The issue only appears when bsdtar both performs compression and writes the
archive to a non‑seekable destination (stdout/pipe with shell redirection).
The fact that:
-f file with builtin gzip/zstd is always OK, and
tar -c | gzip / tar -c | zstd is always OK,
strongly suggests a bug in the libarchive/bsdtar write/flush path for
compressed output to non‑seekable file descriptors (finalization or padding
after EOF, or similar), rather than in the external compressor tools.
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