Unsigned transactions cannot be parsed by bitcoind

[bitcoin-abc]

Unsigned transactions cannot be parsed by bitcoind

[PiRK]

So, when a transaction has an unsigned input, the serialized script is
41000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000021000000000000000000000000000000000000000000000000000000000000000000

It looks like garbage indeed.

[PiRK]

The code is confusing, because of all the branching. It seems that unsigned transactions get through an "estimate_size" branch, in which a blank pubkey ("210000...") and a blank Schnorr signature ("410000...") are used in the serialization.

But simply forcing the other branch (estimate_size=Falase) does not produce a raw tx that works for "decoderawtransaction" either.

[PiRK]

This could be the issue: https://github.com/Bitcoin-ABC/ElectrumABC/blob/master/electroncash/transaction.py#L673

There is additional (non standard) data added to each input when unsigned transactions are generated. So my initial assessment was wrong, it is not causes by dummy signatures being added.

Related discussions:

• Electron-Cash#1628 (comment)
• Electron-Cash#1648

[PiRK]

Confirmed: if I comment out that block, the hex is a proper unsigned tx that can be decoded by the node.
But it has a bunch of side effects, like being unable to sign and broadcast the generated transaction. I'll have another look at this a bit later. This is calling for a refactoring of the transaction.py module.

[jasonbcox]

Thanks for doing a proper investigation. Looking forward to the fix.