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bpo-32583: Fix possible crashing in builtin Unicode decoders (#5325)

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When using customized decode error handlers, it is possible for builtin decoders
to write out-of-bounds and then crash.
This commit is contained in:
Xiang Zhang 2018-01-31 20:48:05 +08:00 • committed by GitHub
parent 84521047e4
commit 2c7fd46e11
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3 changed files with 74 additions and 2 deletions
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52
Lib/test/test_codeccallbacks.py
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@ -1044,6 +1044,58 @@ class CodecCallbackTest(unittest.TestCase):
for (encoding, data) in baddata:
self.assertEqual(data.decode(encoding, "test.mutating"), "\u4242")
# issue32583
def test_crashing_decode_handler(self):
# better generating one more character to fill the extra space slot
# so in debug build it can steadily fail
def forward_shorter_than_end(exc):
if isinstance(exc, UnicodeDecodeError):
# size one character, 0 < forward < exc.end
return ('\ufffd', exc.start+1)
else:
raise TypeError("don't know how to handle %r" % exc)
codecs.register_error(
"test.forward_shorter_than_end", forward_shorter_than_end)
self.assertEqual(
b'\xd8\xd8\xd8\xd8\xd8\x00\x00\x00'.decode(
'utf-16-le', 'test.forward_shorter_than_end'),
'\ufffd\ufffd\ufffd\ufffd\xd8\x00'
)
self.assertEqual(
b'\xd8\xd8\xd8\xd8\x00\xd8\x00\x00'.decode(
'utf-16-be', 'test.forward_shorter_than_end'),
'\ufffd\ufffd\ufffd\ufffd\xd8\x00'
)
self.assertEqual(
b'\x11\x11\x11\x11\x11\x00\x00\x00\x00\x00\x00'.decode(
'utf-32-le', 'test.forward_shorter_than_end'),
'\ufffd\ufffd\ufffd\u1111\x00'
)
self.assertEqual(
b'\x11\x11\x11\x00\x00\x11\x11\x00\x00\x00\x00'.decode(
'utf-32-be', 'test.forward_shorter_than_end'),
'\ufffd\ufffd\ufffd\u1111\x00'
)
def replace_with_long(exc):
if isinstance(exc, UnicodeDecodeError):
exc.object = b"\x00" * 8
return ('\ufffd', exc.start)
else:
raise TypeError("don't know how to handle %r" % exc)
codecs.register_error("test.replace_with_long", replace_with_long)
self.assertEqual(
b'\x00'.decode('utf-16', 'test.replace_with_long'),
'\ufffd\x00\x00\x00\x00'
)
self.assertEqual(
b'\x00'.decode('utf-32', 'test.replace_with_long'),
'\ufffd\x00\x00'
)
def test_fake_error_class(self):
handlers = [
codecs.strict_errors,