5bad7921d0 [test] PSBT RPC: check that bip32_derivs are present by default (Sjors Provoost)
29a21c9061 [rpc] set default bip32derivs to true for psbt methods (Sjors Provoost)
Pull request description:
In https://github.com/bitcoin/bitcoin/pull/13557#pullrequestreview-135905054 I recommended not including bip32 deriviation by default in PSBTs:
> _Bit of a privacy issue_: let's say person A and B are about to spend from a multisig address, sending everything to person A. Person A gives their address to person B, their wallet wallet creates a PSBT, but doesn't sign it. Wallet A then calls `walletprocesspsbt` which signs it and _spontaneously adds the master_fingerprint and bip32 path_. Same issue with `walletcreatefundedpsbt`.
>
> Adding `bip32_derivs` should probably be opt-in.
In practice I find this default quite annoying because I forget it and end up with a confused hardware wallet.
More importantly, in the multisig example I provided, it's actually essential for the other side to know the derivation details (in addition to an xpub). This allows them to check that change is going to an address you can still co-sign for (because the spending policy is unchanged except for an index).
ACKs for top commit:
instagibbs:
utACK 5bad7921d0
jonatack:
ACK 5bad7921d0 code review, built, ran tests, inspected/messed around with/pprinted values from the new tests. Thanks for adding the tests.
meshcollider:
utACK 5bad7921d0
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