test: refactor: deduplicate ECDSA signing for tx inputs
Summary:
There are several instances in functional tests and the framework
(MiniWallet, feature_block.py) where we create a legacy
ECDSA signature for a certain transaction's input by doing the following
steps:
- calculate the SignatureHashForkId with the desired sighash type
- create the actual digital signature by calling ECKey.sign_ecdsa on the signature message hash calculated above
- put the DER-encoded result as CScript data push into tx input's scriptSig
Create a new helper sign_input which hides those details and
takes only the necessary parameters (tx, input index, relevant
scriptPubKey, private key). For
further convenience, the signature is prepended to already existing
data-pushes in scriptSig, in order to avoid rehashing the transaction
after calling the new signing function.
This is a backport of core#28025 and a partial backport of core#32591
https://github.com/bitcoin/bitcoin/pull/32591/commits/1a689a2c88715c583da6d88cac3f77bdbaeaf551
Backport notes:
- for now we always use SIGHASH_ALL | SIGHASH_FORKID as a sighash flag, so no need to pass it as a parameter
- see D18733 for why the signing code is in blocktools rather than feature_block.py
- I didn't put the new function in script.py to avoid a script.py <-> signature_hash.py circular import. It makes more sense to put it in txtools anyway
- we weren't testing what we expected to test in feature_block.py wrt to InvalidOPIFConstruction and DisabledOpcode_*. The blocks including these transactions were accepted because sign_tx was overwriting the problematic scriptsig. Now they properly fail block inclusion for the expected reason (pushonly rule)
Test Plan: ninja check-functional
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D18927