As described in CVE-2020-14199 it is unsafe to only rely on witness
UTXO information when signing. Hardware wallets fixed this by also
requiring the full non-witness UTXO to be present for a witness input.
To be compatible with those newer hardware wallet firmware, we need to
remove the sanity checks that disallowed setting witness and non-witness
UTXOs at the same time.
See https://github.com/bitcoin/bitcoin/pull/19215 for comparison which
removed the sanity checks in Bitcoin Core.
This commit fixes a panic when deserializing PSBTs in raw binary.
If the key type was SighashType and the value was not 4 bytes long,
the call to binary.LittleEndian.Uint32(value) would panic as the
function expects 4 bytes to parse into a uint32. We now perform a
sanity check that asserts that the value is 4 bytes long.
