The new SIGHASH_UTXO has a possible attack vector where prepared huge
outputs are used and required to be hashed for the signing preimage.
At most you can force the full node to prepare 20GB of (utxo) data
_prior_ to creation of the preimage. Which is a big issue when it comes
to memory usage of the node.
What this change does is we ensure that the class used for this data is
a ConstBuf as given to us from the utxo. Which are just pointers and not
full data, the data is memory mapped.
So we ensure shallow copies to avoid actually requiring the data to be
in memory until the point where it is used. And it can get swapped out
immediately after.
This ensures we are immune to the SIGHASH_UTXO attack vector.
tomFlowee
TomZ