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bpo-45507: EOFErrors should be thrown for truncated gzip members #29029

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Merged
merged 1 commit into from
Nov 19, 2021
Merged

bpo-45507: EOFErrors should be thrown for truncated gzip members #29029

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3 changes: 3 additions & 0 deletions Lib/gzip.py
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Original file line number Diff line number Diff line change
Expand Up @@ -607,6 +607,9 @@ def decompress(data):
do = zlib.decompressobj(wbits=-zlib.MAX_WBITS)
# Read all the data except the header
decompressed = do.decompress(data[fp.tell():])
if not do.eof or len(do.unused_data) < 8:
raise EOFError("Compressed file ended before the end-of-stream "
"marker was reached")
crc, length = struct.unpack("<II", do.unused_data[:8])
if crc != zlib.crc32(decompressed):
raise BadGzipFile("CRC check failed")
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8 changes: 8 additions & 0 deletions Lib/test/test_gzip.py
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Expand Up @@ -562,6 +562,14 @@ def test_decompress(self):
datac = gzip.compress(data)
self.assertEqual(gzip.decompress(datac), data)

def test_decompress_truncated_trailer(self):
compressed_data = gzip.compress(data1)
self.assertRaises(EOFError, gzip.decompress, compressed_data[:-4])

def test_decompress_missing_trailer(self):
compressed_data = gzip.compress(data1)
self.assertRaises(EOFError, gzip.decompress, compressed_data[:-8])

def test_read_truncated(self):
data = data1*50
# Drop the CRC (4 bytes) and file size (4 bytes).
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2021-10-18-14-00-01.bpo-45507.lDotNV.rst
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@@ -0,0 +1 @@
Add tests for truncated/missing trailers in gzip.decompress implementation.