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gh-88233: zipfile: handle extras after a zip64 extra #96161

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Merged
miss-islington merged 8 commits into from
Feb 20, 2023
Merged

gh-88233: zipfile: handle extras after a zip64 extra #96161

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a263718
zipfile: handle extras after a zip64 extra
thatch Aug 21, 2022
f995644
Add NEWS entry for bugfix
thatch Sep 5, 2022
105321c
Merge branch 'main' into issue88233
arhadthedev Feb 5, 2023
9c58352
Fix typo
jaraco Feb 20, 2023
72f6e4d
Tweak style to conform to best conventions. Remove unused variable.
jaraco Feb 20, 2023
b1dad59
Reflow comment to 72 characters per PEP 8.
jaraco Feb 20, 2023
61ad114
Replace literal and ambiguous comment with a self-documenting constant.
jaraco Feb 20, 2023
a26edf1
Merge branch 'main' into issue88233
jaraco Feb 20, 2023
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zipfile: handle extras after a zip64 extra 
Previously, any data _after_ the zip64 extra would be removed.

With many new tests.

Fixes #88233
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@thatch
thatch committed Sep 5, 2022
commit a263718a19eb7828b114a2634d2fe8895c42dbf6
52 changes: 52 additions & 0 deletions Lib/test/test_zipfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3425,6 +3425,58 @@ def test_cli_with_metadata_encoding_extract(self):
for name in self.file_names:
self.assertIn(name, listing)

class StripExtraTests(unittest.TestCase):
# Note: all of the "z" characters are technically invalid, but up to 3 bytes
# at the end of the extra will be passed through as they are too short to
# encode a valid extra.
def test_no_data(self):
s = struct.Struct("<HH")
a = s.pack(1, 0) # 1=zip64 exta signature
b = s.pack(2, 0)
c = s.pack(3, 0)

self.assertEqual(b'', zipfile._strip_extra(a, (1,)))
self.assertEqual(b, zipfile._strip_extra(b, (1,)))
self.assertEqual(b+b"z", zipfile._strip_extra(b+b"z", (1,)))

self.assertEqual(b+c, zipfile._strip_extra(a+b+c, (1,)))
self.assertEqual(b+c, zipfile._strip_extra(b+a+c, (1,)))
self.assertEqual(b+c, zipfile._strip_extra(b+c+a, (1,)))

def test_with_data(self):
s = struct.Struct("<HH")
a = s.pack(1, 1) + b"a" # 1=zip64 exta signature
b = s.pack(2, 2) + b"bb"
c = s.pack(3, 3) + b"ccc"

self.assertEqual(b"", zipfile._strip_extra(a, (1,)))
self.assertEqual(b, zipfile._strip_extra(b, (1,)))
self.assertEqual(b+b"z", zipfile._strip_extra(b+b"z", (1,)))

self.assertEqual(b+c, zipfile._strip_extra(a+b+c, (1,)))
self.assertEqual(b+c, zipfile._strip_extra(b+a+c, (1,)))
self.assertEqual(b+c, zipfile._strip_extra(b+c+a, (1,)))

def test_multiples(self):
s = struct.Struct("<HH")
a = s.pack(1, 1) + b"a" # 1=zip64 exta signature
b = s.pack(2, 2) + b"bb"
c = s.pack(3, 3) + b"ccc"

self.assertEqual(b"", zipfile._strip_extra(a+a, (1,)))
self.assertEqual(b"", zipfile._strip_extra(a+a+a, (1,)))
self.assertEqual(b"z", zipfile._strip_extra(a+a+b"z", (1,)))
self.assertEqual(b+b"z", zipfile._strip_extra(a+a+b+b"z", (1,)))

self.assertEqual(b, zipfile._strip_extra(a+a+b, (1,)))
self.assertEqual(b, zipfile._strip_extra(a+b+a, (1,)))
self.assertEqual(b, zipfile._strip_extra(b+a+a, (1,)))

def test_too_short(self):
self.assertEqual(b"", zipfile._strip_extra(b"", (1,)))
self.assertEqual(b"z", zipfile._strip_extra(b"z", (1,)))
self.assertEqual(b"zz", zipfile._strip_extra(b"zz", (1,)))
self.assertEqual(b"zzz", zipfile._strip_extra(b"zzz", (1,)))

if __name__ == "__main__":
unittest.main()
2 changes: 2 additions & 0 deletions Lib/zipfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,8 @@ def _strip_extra(extra, xids):
i = j
if not modified:
return extra
if start != len(extra):
buffer.append(extra[start:])
return b''.join(buffer)

def _check_zipfile(fp):
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