Merge #13452: rpc: have verifytxoutproof check the number of txns in proof structure
Summary:
PR13452 backport https://github.com/bitcoin/bitcoin/pull/13452/files
d280617bf569f84457eaea546541dc74c67cd1e4 [qa] Add a test for merkle proof malleation (Suhas Daftuar)
ed82f1700006830b6fe34572b66245c1487ccd29 have verifytxoutproof check the number of txns in proof structure (Gregory Sanders)
Pull request description:
Recent publication of a weakness in Bitcoin's merkle tree construction demonstrates many SPV applications vulnerable to an expensive to pull off yet still plausible attack: https://bitslog.wordpress.com/2018/06/09/leaf-node-weakness-in-bitcoin-merkle-tree-design/ This change would at least allow `verifytxoutproof` to properly validate that the proof matches a known block, with known number of transactions any time after the full block is processed. This should neuter the attack entirely. The negative is that a header-only processed block/future syncing mode would cause this to fail until the node has imported the data required. related: #13451 `importprunedfunds` needs this check as well. Can expand it to cover this if people like the idea.
Test Plan:
make check
test_runner.py
Reviewers: deadalnix, jasonbcox, Fabien, #bitcoin_abc
Reviewed By: Fabien, #bitcoin_abc
Differential Revision: https://reviews.bitcoinabc.org/D3492