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Address CVE-2019-20907 in tarfile module #3

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Merged
shaunmlowry merged 1 commit into from
Nov 4, 2020
Merged

Address CVE-2019-20907 in tarfile module #3

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2 changes: 2 additions & 0 deletions Lib/tarfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1400,6 +1400,8 @@ def _proc_pax(self, tarfile):

length, keyword = match.groups()
length = int(length)
if length == 0:
raise InvalidHeaderError("invalid header")
value = buf[match.end(2) + 1:match.start(1) + length - 1]

keyword = keyword.decode("utf8")
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Binary file added Lib/test/recursion.tar
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7 changes: 7 additions & 0 deletions Lib/test/test_tarfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -321,6 +321,13 @@ def test_premature_end_of_archive(self):
with self.assertRaisesRegexp(tarfile.ReadError, "unexpected end of data"):
tar.extractfile(t).read()

def test_length_zero_header(self):
# bpo-39017 (CVE-2019-20907): reading a zero-length header should fail
# with an exception
with self.assertRaisesRegexp(tarfile.ReadError, "file could not be opened successfully"):
with tarfile.open(support.findfile('recursion.tar')) as tar:
pass


class MiscReadTest(CommonReadTest):
taropen = tarfile.TarFile.taropen
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