Pycoin does not validate Gavin Andresen's test multisig transaction. about pycoin HOT 9 CLOSED

There is a method in pycoin/services/bitcoind.py called "bitcoind_agrees_on_transaction_validity" that is useful for checking agreement of bitcoind and pycoin that you might find useful.

There is a bug in pycoin that causes some (but not all) multisig transactions to not validate when they should. I have a test case which currently fails, so I just need to track down what's wrong. I think it's a problem in my implementation of OP_CHECKMULTISIG.

You should be able to partially sign with just one key. I seem to remember that I have a test case that does this...

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That test case is in tests/pay_to_test.py, in test_multisig_one_at_a_time().
Looks like a great starting point to learn pycoin tx internals, thanks. I shall rewrite my gist as test case,
checking if Gavin's transaction signature is ok and than trying to recreate it from scratch.

That problem in the implementation of OP_CHECKMULTISIG, do you think it is in
tx/script/vm.py, or deeper in ecdsa.possible_public_pairs_for_signature()? In other words,
do you think eval_script() reads bad data from script and feeds it into possible_public_pairs_for_signature() or the signature_hash and sig_pair are correct?

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My gut feeling is that the problem is possible_public_pairs_for_signature. A prior implementation of OP_CHECKMULTISIG did the naïve thing of trying every signature with every public pair... that one probably worked (although it predated the test that now fails).

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I changed the implementation of OP_CHECKMULTISIG to the earlier version
and unfortunately the tx_test.py still fails at the same point.
(You can see what code I actually run the test against at 9e519b4)

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The transaction couldn't be validated because signature_hash in vm.py is wrong!
If I put the correct signature_hash, the transaction validates.
(Actually, I force the correct script into signature_for_hash_type_f.)
Please, checkout: 689e067, and run tests/ga_multisig_test.py.

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I came up with the solution: PR #73.
What do you think?

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Unfortunately, now pay_to_test.py fails.
I think that's because Tx.sign_tx_in() does not handle P2SH input correctly. I took care of it in 6a365a8

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@gitmarek I can confirm your fix works. Pycoin now correctly signs multisig transactions.

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Merged (squashed) in 9333471

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