feat: implement `GetKey` for `KeyMap` and `DescriptorSecretKey` #851

oleonardolima · 2025-08-22T20:31:49Z

fixes #709

Description

I've built upon Tobin's work in #765 (see #765 (comment)) to implement the GetKey trait for KeyMap, a feature that will enable us to entirely remove the signers API from bdk_wallet, see: bitcoindevkit/bdk_wallet#70 and bitcoindevkit/bdk_wallet#235.

Notes to the reviewers

I followed some of Poelstra's previous comments to reduce the number of required matching branches, and also some VM's suggestions on implementing the main GetKey logic for DescriptorSecretKey instead.

Let me know if you have any other suggestions or comments.

Changelog notice

# Added:
 - implemented `GetKey` trait for `KeyMap`
 - implemented `GetKey` trait for `DescriptorSecretKey`

# Changed
 - moved `KeyMap` to it's own `key_map` module, replacing the `BTreeMap` alias.

tcharding · 2025-08-22T22:06:29Z

Mad, thanks man. I'm off travelling this week but can help review this when I get a chance if needed. I don't do many reviews in miniscript in general.

apoelstra · 2025-08-22T23:13:29Z

In 255a61e:

You need to update Cargo-minimal.lock and Cargo-recent.lock to require bitcoin 0.32.6 since the KeyRequest enum was smaller in 0.32.5 and before.

Relatedly, your unreachable! branch is not actually unreachable. It will be hit by any additions to the KeyRequest enum in the future.

oleonardolima · 2025-08-28T14:01:04Z

In 255a61e:

You need to update Cargo-minimal.lock and Cargo-recent.lock to require bitcoin 0.32.6 since the KeyRequest enum was smaller in 0.32.5 and before.

Relatedly, your unreachable! branch is not actually unreachable. It will be hit by any additions to the KeyRequest enum in the future.

Thanks, I've added a new commit 8e05d85 specifically for this version bump.

I also updated unreachable! to unimplemented! instead.

apoelstra · 2025-08-28T14:43:43Z

I also updated unreachable! to unimplemented! instead.

This is not sufficient. The code should not panic on key accesses.

ValuedMammal · 2025-08-29T19:19:59Z

src/descriptor/key_map.rs

+        let path = DerivationPath::from_str("84'/1'/0'/0").unwrap();
+        let expected_pk = xpriv.xkey.derive_priv(&secp, &path).unwrap().to_priv();


Is this the path derived from the master key or from the tpriv shown above?

It's from the key origin as per the descriptor above. It's curious because I had to port this test from bdk_wallet specifically because AFAICT it's a scenario that the default KeyRequest::Bip32 implementation can't cover.

I'm confused what the expected key is in this case. If path is to be derived from the origin, don't we only want to derive one additional step from the xkey?

- it's required in order to have all the added variants for `KeyRequest` type.

- creates a new `key_map` module, and `KeyMap` type to replace the existing `BTreeMap` alias. - it's a commit extracted from superseded PR rust-bitcoin#765.

oleonardolima · 2025-09-08T01:01:53Z

I also updated unreachable! to unimplemented! instead.

This is not sufficient. The code should not panic on key accesses.

Alright, thanks! I'll follow the standard that it should return None, as it can't find the key and no error is found.

I was wondering if a new error variant should be added, but I don't think that's the case. Please let me know if I should proceed in a other way.

- add the implementation of GetKey for `KeyMap`, and also implements it for the inner type `DescriptorSecretKey` in order to make the match branching and logic clearer.

apoelstra · 2025-09-08T13:53:24Z

CI failure is because the stable compiler broke our CI. I'll fix this separately.

apoelstra

ACK e2d934e; successfully ran local tests

tcharding · 2025-09-09T04:31:02Z

You don't need my review on this do you @apoelstra , its a savage context switch.

apoelstra · 2025-09-09T14:39:31Z

Nope! Was just fighting with my local CI setup (had to tweak a bunch of stuff for rust-bitcoin 0.31.x) and forgot to queue the merge here.

Thanks for checking though -- I do usually wait for your review on PRs where you've commented.

oleonardolima · 2025-09-16T08:22:53Z

I've been wondering about this one, 13.0.0 is pretty far away from releasing, right ?
I'll try to find another way to backport these changes into 12.x, if that's fine, ofc.

apoelstra · 2025-09-16T13:01:10Z

Yeah, 13.0 is a bit of a ways away.

Backports are welcome. Though this one will be a little tricky because you can't replace the BTreeMap alias in a backport.

…`KeyMap` and `DescriptorSecretKey` e2d934eb9530ffac3a26cb3c822dd5ed9bc29a85 feat: impl `GetKey` for `KeyMap` and `DescriptorSecretKey` (Leonardo Lima) 6f345d75b03d49a1e606d161656067a7f8331cf2 refactor(keymap): create `KeyMap` type (Tobin C. Harding) 131cf01f318fa9ba98c03da8ea9bab62ce7d44eb chore(deps): bump `bitcoin` to `0.32.6` (Leonardo Lima) Pull request description: fixes rust-bitcoin/rust-miniscript#709 ### Description I've built upon Tobin's work in #765 (see rust-bitcoin/rust-miniscript#765 (comment)) to implement the `GetKey` trait for `KeyMap`, a feature that will enable us to entirely remove the signers API from `bdk_wallet`, see: bitcoindevkit/bdk_wallet#70 and bitcoindevkit/bdk_wallet#235. ### Notes to the reviewers I followed some of Poelstra's previous comments to reduce the number of required matching branches, and also some VM's suggestions on implementing the main `GetKey` logic for `DescriptorSecretKey` instead. Let me know if you have any other suggestions or comments. ### Changelog notice ```md # Added: - implemented `GetKey` trait for `KeyMap` - implemented `GetKey` trait for `DescriptorSecretKey` # Changed - moved `KeyMap` to it's own `key_map` module, replacing the `BTreeMap` alias. ``` ACKs for top commit: apoelstra: ACK e2d934eb9530ffac3a26cb3c822dd5ed9bc29a85; successfully ran local tests Tree-SHA512: 85168f3d6de0527d077674ff4e988ecda9f6237ae1c15018a1cfeb5760fa5a14b700b58a9e78d79b15cffba12b3f1e8de3a5e82c0822a0506aa7fa926bf8a7d8

oleonardolima · 2025-09-29T03:16:32Z

Yeah, 13.0 is a bit of a ways away.

Backports are welcome. Though this one will be a little tricky because you can't replace the BTreeMap alias in a backport.

I'm not sure if there is a more elegant way to do it, but introducing a KeyMapWrapper (or other name) which implements the GetKey would circumvent the orphan rule and solve the issue for release/12.x.

- add `KeyMapWrapper` with `GetKey` trait for PSBT signing - implement `GetKey` for `DescriptorSecretKey` - add `From<KeyMap>` conversion - export new `KeyMapWrapper` for downstream crate usage

… keys 89b5048 test: extend unit tests to cover KeyMapWrapper error conditions (Andrew Poelstra) 78cddab key_map: handle lookup errors on multipath xprivs correctly (Andrew Poelstra) Pull request description: Since #851 we return a `NotSupported` error when attempting to request an xpriv from an x-only key. I'm not sure if this is the correct semantics, but it was deliberately written, so we'll keep it. **However** the behavior was different for multipath xprivs. There we returned `None`, i.e. "key not found/mismatch" rather than an error. This PR returns an error in both cases. ACKs for top commit: oleonardolima: ACK 89b5048 Tree-SHA512: e59b4d6877374c7e07ddf282422c42b6735f04514d2cc70610dca15dd4153cd372f9a1ccf86d3ce57ea32e8784229de0288a0e1b196405034065d92e5b134f9c

08fa87a test: extend unit tests to cover KeyMapWrapper error conditions (Andrew Poelstra) 5f089aa key_map: handle lookup errors on multipath xprivs correctly (Andrew Poelstra) c7d4171 feat(descriptor): backport `GetKey` impl from #851 (Leonardo Lima) 58d1df9 chore(deps): bump `bitcoin` to `0.32.6` (Leonardo Lima) Pull request description: backports #851 to release/12.x ### Description It's an initial attempt to backport the implementation of GetKey for KeyMap introduced in #851. ### Notes to the reviewers I noticed that the type `KeyMapWrapper` is already being used internally for parse_descriptor, though, as it's not part of the public API, there's no conflict, but I'm fine with changing it to another name if needed. ### Changelog Notice ``` # Added - add `KeyMapWrapper` with `GetKey` trait for PSBT signing - implement `GetKey` for `DescriptorSecretKey` - add `From<KeyMap>` conversion - export new `KeyMapWrapper` for downstream crate usage ``` ACKs for top commit: apoelstra: ACK 08fa87a; successfully ran local tests Tree-SHA512: 73f100f9b851012debdc1c8bb8b89bc76394865c98f315831168978d0c93038932745ff58ceb52d04c02e50e6c5c6073658e16279abb2b10c5b7b6c346f18ed2

oleonardolima force-pushed the feat/impl-getkey-for-keymap branch 3 times, most recently from acc2d04 to ab69aac Compare August 28, 2025 14:00

ValuedMammal reviewed Aug 29, 2025

View reviewed changes

oleonardolima and others added 2 commits September 8, 2025 10:52

chore(deps): bump bitcoin to 0.32.6

131cf01

- it's required in order to have all the added variants for `KeyRequest` type.

refactor(keymap): create KeyMap type

6f345d7

- creates a new `key_map` module, and `KeyMap` type to replace the existing `BTreeMap` alias. - it's a commit extracted from superseded PR rust-bitcoin#765.

feat: impl GetKey for KeyMap and DescriptorSecretKey

e2d934e

- add the implementation of GetKey for `KeyMap`, and also implements it for the inner type `DescriptorSecretKey` in order to make the match branching and logic clearer.

oleonardolima force-pushed the feat/impl-getkey-for-keymap branch from ab69aac to e2d934e Compare September 8, 2025 01:03

apoelstra approved these changes Sep 8, 2025

View reviewed changes

apoelstra merged commit 946901e into rust-bitcoin:master Sep 9, 2025
59 of 61 checks passed

tcharding mentioned this pull request Sep 23, 2025

Add summit label #856

Closed

tcharding added the summit To review at Rust Bitcoin Summit. label Sep 24, 2025

oleonardolima mentioned this pull request Sep 29, 2025

feat(descriptor): backport GetKey impl from #851 #860

Merged

ItoroD mentioned this pull request Sep 29, 2025

Add Psbt::sign API to Psbt type bitcoindevkit/bdk-ffi#866

Open

apoelstra mentioned this pull request Sep 30, 2025

key_map.rs: propagate "invalid key" errors from multipath keys #861

Merged

		let path = DerivationPath::from_str("84'/1'/0'/0").unwrap();
		let expected_pk = xpriv.xkey.derive_priv(&secp, &path).unwrap().to_priv();

feat: implement GetKey for KeyMap and DescriptorSecretKey #851

feat: implement GetKey for KeyMap and DescriptorSecretKey #851

Uh oh!

Conversation

oleonardolima commented Aug 22, 2025

Description

Notes to the reviewers

Changelog notice

Uh oh!

tcharding commented Aug 22, 2025

Uh oh!

apoelstra commented Aug 22, 2025

Uh oh!

oleonardolima commented Aug 28, 2025

Uh oh!

apoelstra commented Aug 28, 2025

Uh oh!

ValuedMammal Aug 29, 2025

Choose a reason for hiding this comment

Uh oh!

oleonardolima Sep 8, 2025

Choose a reason for hiding this comment

Uh oh!

ValuedMammal Sep 8, 2025

Choose a reason for hiding this comment

Uh oh!

oleonardolima commented Sep 8, 2025

Uh oh!

apoelstra commented Sep 8, 2025

Uh oh!

apoelstra left a comment

Choose a reason for hiding this comment

Uh oh!

tcharding commented Sep 9, 2025

Uh oh!

apoelstra commented Sep 9, 2025

Uh oh!

Uh oh!

oleonardolima commented Sep 16, 2025

Uh oh!

apoelstra commented Sep 16, 2025

Uh oh!

oleonardolima commented Sep 29, 2025

Uh oh!

Uh oh!

feat: implement `GetKey` for `KeyMap` and `DescriptorSecretKey` #851

feat: implement `GetKey` for `KeyMap` and `DescriptorSecretKey` #851