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83950275eddacac56c58a7a3648ed435a5593328 qa: unit test sighash caching (Antoine Poinsot)
b221aa80a081579b8d3b460e3403f7ac0daa7139 qa: simple differential fuzzing for sighash with/without caching (Antoine Poinsot)
92af9f74d74e76681f7d98f293eab226972137b4 script: (optimization) introduce sighash midstate caching (Pieter Wuille)
8f3ddb0bccebc930836b4a6745a7cf29b41eb302 script: (refactor) prepare for introducing sighash midstate cache (Pieter Wuille)
9014d4016ad9351cb59b587541895e55f5d589cc tests: add sighash caching tests to feature_taproot (Pieter Wuille)
Pull request description:
This introduces a per-txin cache for sighash midstate computation to the script interpreter for legacy (bare), P2SH, P2WSH, and (as collateral effect, but not actually useful) P2WPKH. This reduces the impact of certain types of quadratic hashing attacks that use standard transactions. It is not known to improve the situation for attacks involving non-standard transaction attacks.
The cache works by remembering for each of the 6 sighash modes a `(scriptCode, midstate)` tuple, which gives a midstate `CSHA256` object right before the appending of the sighash type itself (to permit all 256, rather than just the 6 ones that match the modes). The midstate is only reused if the `scriptCode` matches. This works because - within a single input - only the sighash type and the `scriptCode` affect the actual sighash used.
The PR implements two different approaches:
* The initial commits introduce the caching effect always, for both consensus and relay relation validation. Despite being primarily intended for improving the situation for standard transactions only, I chose this approach as the code paths are already largely common between the two, and this approach I believe involves fewer code changes than a more targetted approach, and furthermore, it should not hurt (it may even help common multisig cases slightly).
* The final commit changes the behavior to only using the cache for non-consensus script validation. I'm open to feedback about whether adding this commit is worth it.
Functional tests are included that construct contrived cases with many sighash types (standard and non-standard ones) and `OP_CODESEPARATOR`s in all script types (including P2TR, which isn't modified by this PR).
ACKs for top commit:
achow101:
ACK 83950275eddacac56c58a7a3648ed435a5593328
dergoegge:
Code review ACK 83950275eddacac56c58a7a3648ed435a5593328
darosior:
re-ACK 83950275eddacac56c58a7a3648ed435a5593328
Tree-SHA512: 65ae8635429a4d563b19969bac8128038ac2cbe01d9c9946abd4cac3c0780974d1e8b9aae9bb83f414e5d247a59f4a18fef5b37d93ad59ed41b6f11c3fe05af4
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| .. | ||
| __init__.py | ||
| address.py | ||
| authproxy.py | ||
| bdb.py | ||
| bip340_test_vectors.csv | ||
| blocktools.py | ||
| coverage.py | ||
| descriptors.py | ||
| key.py | ||
| liquid_addr.py | ||
| messages.py | ||
| muhash.py | ||
| netutil.py | ||
| p2p.py | ||
| ripemd160.py | ||
| script.py | ||
| script_util.py | ||
| segwit_addr.py | ||
| siphash.py | ||
| socks5.py | ||
| test_framework.py | ||
| test_node.py | ||
| test_shell.py | ||
| util.py | ||
| wallet.py | ||
| wallet_util.py | ||