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Commit66363b9

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pythongh-109858: Protect zipfile from "quoted-overlap" zipbomb (pythonGH-110016)
Raise BadZipFile when try to read an entry that overlaps with other entry orcentral directory.
1 parent183b97b commit66363b9

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3 files changed

+73
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lines changed

3 files changed

+73
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lines changed

‎Lib/test/test_zipfile/test_core.py

Lines changed: 58 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2272,6 +2272,64 @@ def test_decompress_without_3rd_party_library(self):
22722272
withzipfile.ZipFile(zip_file)aszf:
22732273
self.assertRaises(RuntimeError,zf.extract,'a.txt')
22742274

2275+
deftest_full_overlap(self):
2276+
data= (
2277+
b'PK\x03\x04\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2\x1e'
2278+
b'8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00a\xed'
2279+
b'\xc0\x81\x08\x00\x00\x00\xc00\xd6\xfbK\\d\x0b`P'
2280+
b'K\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2'
2281+
b'\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00\x00'
2282+
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00aPK'
2283+
b'\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2\x1e'
2284+
b'8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00\x00\x00'
2285+
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00bPK\x05'
2286+
b'\x06\x00\x00\x00\x00\x02\x00\x02\x00^\x00\x00\x00/\x00\x00'
2287+
b'\x00\x00\x00'
2288+
)
2289+
withzipfile.ZipFile(io.BytesIO(data),'r')aszipf:
2290+
self.assertEqual(zipf.namelist(), ['a','b'])
2291+
zi=zipf.getinfo('a')
2292+
self.assertEqual(zi.header_offset,0)
2293+
self.assertEqual(zi.compress_size,16)
2294+
self.assertEqual(zi.file_size,1033)
2295+
zi=zipf.getinfo('b')
2296+
self.assertEqual(zi.header_offset,0)
2297+
self.assertEqual(zi.compress_size,16)
2298+
self.assertEqual(zi.file_size,1033)
2299+
self.assertEqual(len(zipf.read('a')),1033)
2300+
withself.assertRaisesRegex(zipfile.BadZipFile,'File name.*differ'):
2301+
zipf.read('b')
2302+
2303+
deftest_quoted_overlap(self):
2304+
data= (
2305+
b'PK\x03\x04\x14\x00\x00\x00\x08\x00\xa0lH\x05Y\xfc'
2306+
b'8\x044\x00\x00\x00(\x04\x00\x00\x01\x00\x00\x00a\x00'
2307+
b'\x1f\x00\xe0\xffPK\x03\x04\x14\x00\x00\x00\x08\x00\xa0l'
2308+
b'H\x05\xe2\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00'
2309+
b'\x00\x00b\xed\xc0\x81\x08\x00\x00\x00\xc00\xd6\xfbK\\'
2310+
b'd\x0b`PK\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0'
2311+
b'lH\x05Y\xfc8\x044\x00\x00\x00(\x04\x00\x00\x01'
2312+
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
2313+
b'\x00aPK\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0l'
2314+
b'H\x05\xe2\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00'
2315+
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00$\x00\x00\x00'
2316+
b'bPK\x05\x06\x00\x00\x00\x00\x02\x00\x02\x00^\x00\x00'
2317+
b'\x00S\x00\x00\x00\x00\x00'
2318+
)
2319+
withzipfile.ZipFile(io.BytesIO(data),'r')aszipf:
2320+
self.assertEqual(zipf.namelist(), ['a','b'])
2321+
zi=zipf.getinfo('a')
2322+
self.assertEqual(zi.header_offset,0)
2323+
self.assertEqual(zi.compress_size,52)
2324+
self.assertEqual(zi.file_size,1064)
2325+
zi=zipf.getinfo('b')
2326+
self.assertEqual(zi.header_offset,36)
2327+
self.assertEqual(zi.compress_size,16)
2328+
self.assertEqual(zi.file_size,1033)
2329+
withself.assertRaisesRegex(zipfile.BadZipFile,'Overlapped entries'):
2330+
zipf.read('a')
2331+
self.assertEqual(len(zipf.read('b')),1033)
2332+
22752333
deftearDown(self):
22762334
unlink(TESTFN)
22772335
unlink(TESTFN2)

‎Lib/zipfile/__init__.py

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -395,6 +395,7 @@ class ZipInfo (object):
395395
'compress_size',
396396
'file_size',
397397
'_raw_time',
398+
'_end_offset',
398399
)
399400

400401
def__init__(self,filename="NoName",date_time=(1980,1,1,0,0,0)):
@@ -429,6 +430,7 @@ def __init__(self, filename="NoName", date_time=(1980,1,1,0,0,0)):
429430
self.external_attr=0# External file attributes
430431
self.compress_size=0# Size of the compressed file
431432
self.file_size=0# Size of the uncompressed file
433+
self._end_offset=None# Start of the next local header or central directory
432434
# Other attributes are set by class ZipFile:
433435
# header_offset Byte offset to the file header
434436
# CRC CRC-32 of the uncompressed file
@@ -1488,6 +1490,12 @@ def _RealGetContents(self):
14881490
ifself.debug>2:
14891491
print("total",total)
14901492

1493+
end_offset=self.start_dir
1494+
forzinfoinsorted(self.filelist,
1495+
key=lambdazinfo:zinfo.header_offset,
1496+
reverse=True):
1497+
zinfo._end_offset=end_offset
1498+
end_offset=zinfo.header_offset
14911499

14921500
defnamelist(self):
14931501
"""Return a list of file names in the archive."""
@@ -1644,6 +1652,10 @@ def open(self, name, mode="r", pwd=None, *, force_zip64=False):
16441652
'File name in directory %r and header %r differ.'
16451653
% (zinfo.orig_filename,fname))
16461654

1655+
if (zinfo._end_offsetisnotNoneand
1656+
zef_file.tell()+zinfo.compress_size>zinfo._end_offset):
1657+
raiseBadZipFile(f"Overlapped entries:{zinfo.orig_filename!r} (possible zip bomb)")
1658+
16471659
# check for encrypted flag & handle password
16481660
is_encrypted=zinfo.flag_bits&_MASK_ENCRYPTED
16491661
ifis_encrypted:
Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,3 @@
1+
Protect:mod:`zipfile` from "quoted-overlap" zipbomb. It now raises
2+
BadZipFile when try to read an entry that overlaps with other entry or
3+
central directory.

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