ValueError('unpack requires a buffer of 2 bytes') in SlowPathParser

[xshill]

The error is launched at line 621:

https://github.com/GoSecure/pyrdp/blob/master/pyrdp/parser/rdp/slowpath.py#L621

According to the documentation, the pointerCacheSize can be omitted from the structure:

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/925e2c05-c13f-44b1-aa20-23082051fef9

pointerCacheSize (2 bytes): A 16-bit, unsigned integer. The number of available slots in the pointer cache used to store pointer data of arbitrary bit depth received in the New Pointer Update (section 2.2.9.1.1.4.5).

If the value contained in this field is zero or the Pointer Capability Set sent from the client does not include this field, the server will not use the New Pointer Update.