https://github.com/python/cpython/commit/674935b8caf33e47c78f1b8e197b1b77a04... commit: 674935b8caf33e47c78f1b8e197b1b77a04992d2 branch: master author: William Chargin <wchargin@gmail.com> committer: GitHub <noreply@github.com> date: 2020-02-12T11:56:02-08:00 summary: bpo-18819: tarfile: only set device fields for device files (GH-18080) The GNU docs describe the `devmajor` and `devminor` fields of the tar header struct only in the context of character and block special files, suggesting that in other cases they are not populated. Typical utilities behave accordingly; this patch teaches `tarfile` to do the same. files: A Misc/NEWS.d/next/Library/2020-01-20-10-06-19.bpo-18819.H4qsoS.rst M Lib/tarfile.py M Lib/test/test_tarfile.py M Misc/ACKS diff --git a/Lib/tarfile.py b/Lib/tarfile.py index 90a2c95b315b3..e2b60532f693d 100755 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -930,6 +930,14 @@ def _create_header(info, format, encoding, errors): """Return a header block. info is a dictionary with file information, format must be one of the *_FORMAT constants. """ + has_device_fields = info.get("type") in (CHRTYPE, BLKTYPE) + if has_device_fields: + devmajor = itn(info.get("devmajor", 0), 8, format) + devminor = itn(info.get("devminor", 0), 8, format) + else: + devmajor = stn("", 8, encoding, errors) + devminor = stn("", 8, encoding, errors) + parts = [ stn(info.get("name", ""), 100, encoding, errors), itn(info.get("mode", 0) & 0o7777, 8, format), @@ -943,8 +951,8 @@ def _create_header(info, format, encoding, errors): info.get("magic", POSIX_MAGIC), stn(info.get("uname", ""), 32, encoding, errors), stn(info.get("gname", ""), 32, encoding, errors), - itn(info.get("devmajor", 0), 8, format), - itn(info.get("devminor", 0), 8, format), + devmajor, + devminor, stn(info.get("prefix", ""), 155, encoding, errors) ] diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 6a901089611cd..cae96802ded67 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -1549,6 +1549,52 @@ def test_longnamelink_1025(self): ("longlnk/" * 127) + "longlink_") +class DeviceHeaderTest(WriteTestBase, unittest.TestCase): + + prefix = "w:" + + def test_headers_written_only_for_device_files(self): + # Regression test for bpo-18819. + tempdir = os.path.join(TEMPDIR, "device_header_test") + os.mkdir(tempdir) + try: + tar = tarfile.open(tmpname, self.mode) + try: + input_blk = tarfile.TarInfo(name="my_block_device") + input_reg = tarfile.TarInfo(name="my_regular_file") + input_blk.type = tarfile.BLKTYPE + input_reg.type = tarfile.REGTYPE + tar.addfile(input_blk) + tar.addfile(input_reg) + finally: + tar.close() + + # devmajor and devminor should be *interpreted* as 0 in both... + tar = tarfile.open(tmpname, "r") + try: + output_blk = tar.getmember("my_block_device") + output_reg = tar.getmember("my_regular_file") + finally: + tar.close() + self.assertEqual(output_blk.devmajor, 0) + self.assertEqual(output_blk.devminor, 0) + self.assertEqual(output_reg.devmajor, 0) + self.assertEqual(output_reg.devminor, 0) + + # ...but the fields should not actually be set on regular files: + with open(tmpname, "rb") as infile: + buf = infile.read() + buf_blk = buf[output_blk.offset:output_blk.offset_data] + buf_reg = buf[output_reg.offset:output_reg.offset_data] + # See `struct posixheader` in GNU docs for byte offsets: + # <https://www.gnu.org/software/tar/manual/html_node/Standard.html> + device_headers = slice(329, 329 + 16) + self.assertEqual(buf_blk[device_headers], b"0000000\0" * 2) + self.assertEqual(buf_reg[device_headers], b"\0" * 16) + finally: + support.rmtree(tempdir) + + class CreateTest(WriteTestBase, unittest.TestCase): prefix = "x:" diff --git a/Misc/ACKS b/Misc/ACKS index 5a779833e68be..933402069b4fd 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -286,6 +286,7 @@ Brad Chapman Greg Chapman Mitch Chapman Matt Chaput +William Chargin Yogesh Chaudhari David Chaum Nicolas Chauvat diff --git a/Misc/NEWS.d/next/Library/2020-01-20-10-06-19.bpo-18819.H4qsoS.rst b/Misc/NEWS.d/next/Library/2020-01-20-10-06-19.bpo-18819.H4qsoS.rst new file mode 100644 index 0000000000000..e9f111ad62e28 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-01-20-10-06-19.bpo-18819.H4qsoS.rst @@ -0,0 +1,3 @@ +Omit ``devmajor`` and ``devminor`` fields for non-device files in +:mod:`tarfile` archives, enabling bit-for-bit compatibility with GNU +``tar(1)``.