SEC-22 CALLDATACOPY does not write zero to memory if input data offset exceeds input data size

[Gustav-Simonsson]

According to YP definition of CALLDATACOPY (0x37) if the input data offset exceeds the length of the input data size (input data passed with message call or tx (Td) then 0 should be written to memory.

Currently instead of writing 0 there is a no op due to the Set function at https://github.com/ethereum/go-ethereum/blob/develop/vm/memory.go#L14 not doing anything if the length of the write is 0.

Fix: remove the offset argument overflow and ensure data is copied up until the end of input data, and then copy zeroes until the end of the supplied offset.

[obscuren]

All methods that mem.Set are either using getData or common.BigToBytes so this can't happen.

I do believe we should add padding in there as well.