Issue Details

Number

19608

Title

Expose PSBT AddInput/AddOutput via RPC

Description

**Is your feature request related to a problem? Please describe.** Alice creates a PSBT via the RPC API, and signs all inputs with `SIGHASH_SINGLE | SIGHASH_ANYONECANPAY`. She then sends the signed PSBT to Bob, who wants to add some more inputs and outputs via the RPC API without losing Alice's signatures, so that he can broadcast the resulting transaction without asking Alice to re-sign. Unfortunately, the PSBT RPC API doesn't seem to provide any way of appending new inputs/outputs to an existing PSBT; it only allows creating a new PSBT (via `createpsbt`) with the full set of inputs/outputs, which has the side effect of losing the existing signatures. **Describe the solution you'd like** It would be useful for the PSBT RPC API to expose the `AddInput` and `AddOutput` methods of `PartiallySignedTransaction`. These would allow adding new inputs/outputs without affecting whatever signature data might already be present in the existing inputs. Something like this: `bitcoin-cli addoutputpsbt 'existingpsbt' '{"data":"00010203"}'` **Describe alternatives you've considered** I considered adapting `combinepsbt` to copy signatures between two transactions with different TXID's if the signatures are valid in both transactions given the `SIGHASH` flags, but this seems rather unwieldy. It might be desirable to support adding multiple outputs (or inputs) in one RPC call, by making the 2nd argument an array of objects instead of an object. Or this might just complicate things unnecessarily. I don't feel particularly strongly about this. **Additional context** N/A.

URL

https://github.com/bitcoin/bitcoin/issue/19608

Closed by

Notes Could be added after PSBT v2

Attention of

Kill Factor (1-10)

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