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fix: reject incomplete zlib bit-length trees #2147

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fix: reject incomplete zlib bit-length trees #2147

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2 changes: 1 addition & 1 deletion src/core/IronPython.Modules/zlib/zlib.net/InfTree.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -312,7 +312,7 @@ internal static int inflate_trees_bits(int[] c, int[] bb, int[] tb, int[] hp, ZS
{
z.msg = "oversubscribed dynamic bit lengths tree";
}
else if (r == (int)ZLibResultCode.Z_DATA_ERROR || bb[0] == 0)
else if (r == (int)ZLibResultCode.Z_BUF_ERROR || bb[0] == 0)
{
z.msg = "incomplete dynamic bit lengths tree";
r = (int)ZLibResultCode.Z_DATA_ERROR;
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10 changes: 10 additions & 0 deletions tests/suite/modules/misc/test_zlib.py
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Expand Up @@ -76,6 +76,16 @@ def test_deflate(self):
self.assertEqual(do.decompress(self.deflate_data), self.text)
self.assertEqual(zlib.decompress(self.deflate_data, -zlib.MAX_WBITS), self.text)

def test_invalid_bit_length_trees(self):
# These dynamic blocks have incomplete and oversubscribed code-length alphabets.
for data in (b'\x05\x00\x00\x01', b'\x05\x00\x92\x00'):
with self.subTest(data=data, api='decompress'):
with self.assertRaisesRegex(zlib.error, r'Error -3\b'):
zlib.decompress(data, -zlib.MAX_WBITS)
with self.subTest(data=data, api='decompressobj'):
with self.assertRaisesRegex(zlib.error, r'Error -3\b'):
zlib.decompressobj(-zlib.MAX_WBITS).decompress(data)

def test_gzip_stream(self):
"""gzip header, uncomplete header"""
for delta in range(1, 25):
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