diff --git a/Lib/tarfile.py b/Lib/tarfile.py index 80d8644af86f74..45f58eb8ac93cf 100644 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -1647,6 +1647,9 @@ def _block(self, count): """Round up a byte count by BLOCKSIZE and return it, e.g. _block(834) => 1024. """ + # Only non-negative offsets are allowed + if count < 0: + raise InvalidHeaderError("invalid offset") blocks, remainder = divmod(count, BLOCKSIZE) if remainder: blocks += 1 diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 7055e1ed147a9e..28914df6b010d0 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -55,6 +55,7 @@ def sha256sum(data): zstname = os.path.join(TEMPDIR, "testtar.tar.zst") tmpname = os.path.join(TEMPDIR, "tmp.tar") dotlessname = os.path.join(TEMPDIR, "testtar") +SPACE = b" " sha256_regtype = ( "e09e4bc8b3c9d9177e77256353b36c159f5f040531bbd4b024a8f9b9196c71ce" @@ -4602,6 +4603,161 @@ def extractall(self, ar): ar.extractall(self.testdir, filter='fully_trusted') +class OffsetValidationTests(unittest.TestCase): + tarname = tmpname + invalid_posix_header = ( + # name: 100 bytes + tarfile.NUL * tarfile.LENGTH_NAME + # mode, space, null terminator: 8 bytes + + b"000755" + SPACE + tarfile.NUL + # uid, space, null terminator: 8 bytes + + b"000001" + SPACE + tarfile.NUL + # gid, space, null terminator: 8 bytes + + b"000001" + SPACE + tarfile.NUL + # size, space: 12 bytes + + b"\xff" * 11 + SPACE + # mtime, space: 12 bytes + + tarfile.NUL * 11 + SPACE + # chksum: 8 bytes + + b"0011407" + tarfile.NUL + # type: 1 byte + + tarfile.REGTYPE + # linkname: 100 bytes + + tarfile.NUL * tarfile.LENGTH_LINK + # magic: 6 bytes, version: 2 bytes + + tarfile.POSIX_MAGIC + # uname: 32 bytes + + tarfile.NUL * 32 + # gname: 32 bytes + + tarfile.NUL * 32 + # devmajor, space, null terminator: 8 bytes + + tarfile.NUL * 6 + SPACE + tarfile.NUL + # devminor, space, null terminator: 8 bytes + + tarfile.NUL * 6 + SPACE + tarfile.NUL + # prefix: 155 bytes + + tarfile.NUL * tarfile.LENGTH_PREFIX + # padding: 12 bytes + + tarfile.NUL * 12 + ) + invalid_gnu_header = ( + # name: 100 bytes + tarfile.NUL * tarfile.LENGTH_NAME + # mode, null terminator: 8 bytes + + b"0000755" + tarfile.NUL + # uid, null terminator: 8 bytes + + b"0000001" + tarfile.NUL + # gid, space, null terminator: 8 bytes + + b"0000001" + tarfile.NUL + # size, space: 12 bytes + + b"\xff" * 11 + SPACE + # mtime, space: 12 bytes + + tarfile.NUL * 11 + SPACE + # chksum: 8 bytes + + b"0011327" + tarfile.NUL + # type: 1 byte + + tarfile.REGTYPE + # linkname: 100 bytes + + tarfile.NUL * tarfile.LENGTH_LINK + # magic: 8 bytes + + tarfile.GNU_MAGIC + # uname: 32 bytes + + tarfile.NUL * 32 + # gname: 32 bytes + + tarfile.NUL * 32 + # devmajor, null terminator: 8 bytes + + tarfile.NUL * 8 + # devminor, null terminator: 8 bytes + + tarfile.NUL * 8 + # padding: 167 bytes + + tarfile.NUL * 167 + ) + invalid_v7_header = ( + # name: 100 bytes + tarfile.NUL * tarfile.LENGTH_NAME + # mode, space, null terminator: 8 bytes + + b"000755" + SPACE + tarfile.NUL + # uid, space, null terminator: 8 bytes + + b"000001" + SPACE + tarfile.NUL + # gid, space, null terminator: 8 bytes + + b"000001" + SPACE + tarfile.NUL + # size, space: 12 bytes + + b"\xff" * 11 + SPACE + # mtime, space: 12 bytes + + tarfile.NUL * 11 + SPACE + # chksum: 8 bytes + + b"0010070" + tarfile.NUL + # type: 1 byte + + tarfile.REGTYPE + # linkname: 100 bytes + + tarfile.NUL * tarfile.LENGTH_LINK + # padding: 255 bytes + + tarfile.NUL * 255 + ) + valid_gnu_header = tarfile.TarInfo("filename").tobuf(tarfile.GNU_FORMAT) + data_block = b"\xff" * tarfile.BLOCKSIZE + + def _write_buffer(self, buffer): + with open(self.tarname, "wb") as f: + f.write(buffer) + + def _get_members(self, ignore_zeros=None): + with open(self.tarname, "rb") as f: + with tarfile.open( + mode="r", fileobj=f, ignore_zeros=ignore_zeros + ) as tar: + return tar.getmembers() + + def _assert_raises_read_error_exception(self): + with self.assertRaisesRegex( + tarfile.ReadError, "file could not be opened successfully" + ): + self._get_members() + + def test_invalid_offset_header_validations(self): + for tar_format, invalid_header in ( + ("posix", self.invalid_posix_header), + ("gnu", self.invalid_gnu_header), + ("v7", self.invalid_v7_header), + ): + with self.subTest(format=tar_format): + self._write_buffer(invalid_header) + self._assert_raises_read_error_exception() + + def test_early_stop_at_invalid_offset_header(self): + buffer = self.valid_gnu_header + self.invalid_gnu_header + self.valid_gnu_header + self._write_buffer(buffer) + members = self._get_members() + self.assertEqual(len(members), 1) + self.assertEqual(members[0].name, "filename") + self.assertEqual(members[0].offset, 0) + + def test_ignore_invalid_archive(self): + # 3 invalid headers with their respective data + buffer = (self.invalid_gnu_header + self.data_block) * 3 + self._write_buffer(buffer) + members = self._get_members(ignore_zeros=True) + self.assertEqual(len(members), 0) + + def test_ignore_invalid_offset_headers(self): + for first_block, second_block, expected_offset in ( + ( + (self.valid_gnu_header), + (self.invalid_gnu_header + self.data_block), + 0, + ), + ( + (self.invalid_gnu_header + self.data_block), + (self.valid_gnu_header), + 1024, + ), + ): + self._write_buffer(first_block + second_block) + members = self._get_members(ignore_zeros=True) + self.assertEqual(len(members), 1) + self.assertEqual(members[0].name, "filename") + self.assertEqual(members[0].offset, expected_offset) + + def setUpModule(): os_helper.unlink(TEMPDIR) os.makedirs(TEMPDIR) diff --git a/Misc/NEWS.d/next/Library/2025-07-23-00-35-29.gh-issue-130577.c7EITy.rst b/Misc/NEWS.d/next/Library/2025-07-23-00-35-29.gh-issue-130577.c7EITy.rst new file mode 100644 index 00000000000000..342cabbc865dc4 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-07-23-00-35-29.gh-issue-130577.c7EITy.rst @@ -0,0 +1,3 @@ +:mod:`tarfile` now validates archives to ensure member offsets are +non-negative. (Contributed by Alexander Enrique Urieles Nieto in +:gh:`130577`.) pFad - Phonifier reborn

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