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Reject ext32 length 0xffffffff in the C unpacker #761

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Reject ext32 length 0xffffffff in the C unpacker #761

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13 changes: 9 additions & 4 deletions msgpack/unpack_template.h
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Original file line number Diff line number Diff line change
Expand Up @@ -232,10 +232,15 @@ static inline int unpack_execute(bool construct, unpack_context* ctx, const char
again_fixed_trail_if_zero(ACS_EXT_VALUE,
_msgpack_load16(uint16_t,n)+1,
_ext_zero);
case CS_EXT_32:
again_fixed_trail_if_zero(ACS_EXT_VALUE,
_msgpack_load32(uint32_t,n)+1,
_ext_zero);
case CS_EXT_32: {
uint32_t size = _msgpack_load32(uint32_t,n);
// trail includes the typecode, so size+1 must not wrap around.
if (size == UINT32_MAX) {
PyErr_Format(PyExc_ValueError, "%u exceeds max ext length", size);
goto _failed;
}
again_fixed_trail_if_zero(ACS_EXT_VALUE, size+1, _ext_zero);
}
case CS_FLOAT: {
double f;
#if PY_VERSION_HEX >= 0x030B00A7
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9 changes: 9 additions & 0 deletions test/test_limits.py
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,15 @@ def test_max_ext_len():
unpacker.unpack()


@pytest.mark.parametrize("method", ["unpack", "skip"])
def test_ext32_max_length(method):
# ext32 with length 0xffffffff followed by bytes that look like another object.
unpacker = Unpacker()
unpacker.feed(b"\xc9\xff\xff\xff\xff" + packb({"a": 1}))
with pytest.raises(UnpackValueError):
getattr(unpacker, method)()


# PyPy fails following tests because of constant folding?
# https://bugs.pypy.org/issue1721
# @pytest.mark.skipif(True, reason="Requires very large memory.")
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