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bpo-38635: Simplify decoding the ZIP64 extra field and make it tolerant to extra data. #16988

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Merged
serhiy-storchaka merged 1 commit into from
Nov 9, 2019
Merged

bpo-38635: Simplify decoding the ZIP64 extra field and make it tolerant to extra data. #16988

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53 changes: 16 additions & 37 deletions Lib/zipfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -465,44 +465,23 @@ def _decodeExtra(self):
if ln+4 > len(extra):
raise BadZipFile("Corrupt extra field %04x (size=%d)" % (tp, ln))
if tp == 0x0001:
if ln >= 24:
counts = unpack('<QQQ', extra[4:28])
elif ln == 16:
counts = unpack('<QQ', extra[4:20])
elif ln == 8:
counts = unpack('<Q', extra[4:12])
elif ln == 0:
counts = ()
else:
raise BadZipFile("Corrupt extra field %04x (size=%d)" % (tp, ln))

idx = 0

data = extra[4:ln+4]
# ZIP64 extension (large files and/or large archives)
if self.file_size in (0xffffffffffffffff, 0xffffffff):
if len(counts) <= idx:
raise BadZipFile(
"Corrupt zip64 extra field. File size not found."
)
self.file_size = counts[idx]
idx += 1

if self.compress_size == 0xFFFFFFFF:
if len(counts) <= idx:
raise BadZipFile(
"Corrupt zip64 extra field. Compress size not found."
)
self.compress_size = counts[idx]
idx += 1

if self.header_offset == 0xffffffff:
if len(counts) <= idx:
raise BadZipFile(
"Corrupt zip64 extra field. Header offset not found."
)
old = self.header_offset
self.header_offset = counts[idx]
idx+=1
try:
if self.file_size in (0xFFFF_FFFF_FFFF_FFFF, 0xFFFF_FFFF):
field = "File size"
self.file_size, = unpack('<Q', data[:8])
data = data[8:]
if self.compress_size == 0xFFFF_FFFF:
field = "Compress size"
self.compress_size, = unpack('<Q', data[:8])
data = data[8:]
if self.header_offset == 0xFFFF_FFFF:
field = "Header offset"
self.header_offset, = unpack('<Q', data[:8])
except struct.error:
raise BadZipFile(f"Corrupt zip64 extra field. "
f"{field} not found.") from None

extra = extra[ln+4:]

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