Merge bitcoindevkit/bdk#1161: ref(hwi): Move hwi out of bdk

105d70e9743f651d141c6e0d901d60d583afd4d9 ref(hwi): Move hwi out of bdk (Daniela Brozzoni)

Pull request description:

  Fixes #872

  ### Description

  This commit moves the `hardwaresigner` outside of bdk and inside `bdk_hwi`

  ### Notes to the reviewers

  There are currently two issues with the code:
  - `TransactionSigner` dictates that `sign_transaction` must return a `SignerError` - but being `SignerError` defined inside of bdk, we can't modify it to include an hwi specific error! I don't know how we could fix this (other than getting rid of the trait altogether :)); for now I just added a `SignerError::Generic` variant, lmk if you have better ideas!
  - The hwi tests used the bdk utils to get a funded wallet for testing, which aren't available in `bdk_hwi`, which made me realize - maybe we should expose them so that we can use them across our crates, and also our users can use them to test their code?
  For now, I just left the test commented.

  ### Changelog notice

  - The old `hardwaresigner` module has been moved out of `bdk` and inside `bdk_hwi`.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  ~~* [ ] I've added tests for the new feature~~
  * [x] I've added docs for the new feature

ACKs for top commit:
  notmandatory:
    reACK 105d70e9743f651d141c6e0d901d60d583afd4d9

Tree-SHA512: 9ae3cd035cc27bd7b2831e89c104f40771c6f165cb3bfe1a9052f820050fca7c19f4dd68f171c630a71a7d18ccdee5f94adbc497c6475bd257c2d01cc08109a1

Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "crates/electrum",
     "crates/esplora",
     "crates/bitcoind_rpc",
+    "crates/hwi",
     "example-crates/example_cli",
     "example-crates/example_electrum",
     "example-crates/example_esplora",

crates/bdk/Cargo.toml

@@ -21,7 +21,6 @@ serde_json = { version = "^1.0" }
 bdk_chain = { path = "../chain", version = "0.7.0", features = ["miniscript", "serde"], default-features = false }
 
 # Optional dependencies
-hwi = { version = "0.7.0", optional = true, features = [ "miniscript"] }
 bip39 = { version = "2.0", optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
@@ -34,8 +33,6 @@ std = ["bitcoin/std", "miniscript/std", "bdk_chain/std"]
 compiler = ["miniscript/compiler"]
 all-keys = ["keys-bip39"]
 keys-bip39 = ["bip39"]
-hardware-signer = ["hwi"]
-test-hardware-signer = ["hardware-signer"]
 
 # This feature is used to run `cargo check` in our CI targeting wasm. It's not recommended
 # for libraries to explicitly include the "getrandom/js" feature, so we only do it when

crates/bdk/src/lib.rs

@@ -17,8 +17,6 @@ extern crate std;
 pub extern crate alloc;
 
 pub extern crate bitcoin;
-#[cfg(feature = "hardware-signer")]
-pub extern crate hwi;
 pub extern crate miniscript;
 extern crate serde;
 extern crate serde_json;

crates/bdk/src/wallet/mod.rs

@@ -50,10 +50,6 @@ pub mod tx_builder;
 pub(crate) mod utils;
 
 pub mod error;
-#[cfg(feature = "hardware-signer")]
-#[cfg_attr(docsrs, doc(cfg(feature = "hardware-signer")))]
-pub mod hardwaresigner;
-
 pub use utils::IsDust;
 
 #[allow(deprecated)]

crates/bdk/src/wallet/signer.rs

@@ -80,6 +80,7 @@
 //! ```
 
 use crate::collections::BTreeMap;
+use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 use core::cmp::Ordering;
@@ -162,16 +163,10 @@ pub enum SignerError {
     SighashError(sighash::Error),
     /// Miniscript PSBT error
     MiniscriptPsbt(MiniscriptPsbtError),
-    /// Error while signing using hardware wallets
+    /// To be used only by external libraries implementing [`InputSigner`] or
-    #[cfg(feature = "hardware-signer")]
+    /// [`TransactionSigner`], so that they can return their own custom errors, without having to
-    HWIError(hwi::error::Error),
+    /// modify [`SignerError`] in BDK.
-}
+    External(String),
-
-#[cfg(feature = "hardware-signer")]
-impl From<hwi::error::Error> for SignerError {
-    fn from(e: hwi::error::Error) -> Self {
-        SignerError::HWIError(e)
-    }
 }
 
 impl From<sighash::Error> for SignerError {
@@ -196,8 +191,7 @@ impl fmt::Display for SignerError {
             Self::InvalidSighash => write!(f, "Invalid SIGHASH for the signing context in use"),
             Self::SighashError(err) => write!(f, "Error while computing the hash to sign: {}", err),
             Self::MiniscriptPsbt(err) => write!(f, "Miniscript PSBT error: {}", err),
-            #[cfg(feature = "hardware-signer")]
+            Self::External(err) => write!(f, "{}", err),
-            Self::HWIError(err) => write!(f, "Error while signing using hardware wallets: {}", err),
         }
     }
 }

crates/bdk/tests/wallet.rs

@@ -3591,41 +3591,6 @@ fn test_fee_rate_sign_grinding_low_r() {
     assert_fee_rate!(psbt, fee.unwrap_or(0), fee_rate);
 }
 
-// #[cfg(feature = "test-hardware-signer")]
-// #[test]
-// fn test_hardware_signer() {
-//     use std::sync::Arc;
-//
-//     use bdk::signer::SignerOrdering;
-//     use bdk::wallet::hardwaresigner::HWISigner;
-//     use hwi::types::HWIChain;
-//     use hwi::HWIClient;
-//
-//     let mut devices = HWIClient::enumerate().unwrap();
-//     if devices.is_empty() {
-//         panic!("No devices found!");
-//     }
-//     let device = devices.remove(0).unwrap();
-//     let client = HWIClient::get_client(&device, true, HWIChain::Regtest).unwrap();
-//     let descriptors = client.get_descriptors::<String>(None).unwrap();
-//     let custom_signer = HWISigner::from_device(&device, HWIChain::Regtest).unwrap();
-//
-//     let (mut wallet, _) = get_funded_wallet(&descriptors.internal[0]);
-//     wallet.add_signer(
-//         KeychainKind::External,
-//         SignerOrdering(200),
-//         Arc::new(custom_signer),
-//     );
-//
-//     let addr = wallet.get_address(LastUnused);
-//     let mut builder = wallet.build_tx();
-//     builder.drain_to(addr.script_pubkey()).drain_wallet();
-//     let (mut psbt, _) = builder.finish().unwrap();
-//
-//     let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
-//     assert!(finalized);
-// }
-
 #[test]
 fn test_taproot_load_descriptor_duplicated_keys() {
     // Added after issue https://github.com/bitcoindevkit/bdk/issues/760

crates/hwi/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "bdk_hwi"
+version = "0.1.0"
+edition = "2021"
+homepage = "https://bitcoindevkit.org"
+repository = "https://github.com/bitcoindevkit/bdk"
+description = "Utilities to use bdk with hardware wallets"
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+[dependencies]
+bdk = { path = "../bdk" }
+hwi = { version = "0.7.0", features = [ "miniscript"] }

crates/hwi/src/lib.rs

@@ -0,0 +1,42 @@
+//! HWI Signer
+//!
+//! This crate contains HWISigner, an implementation of a [`TransactionSigner`] to be
+//! used with hardware wallets.
+//! ```no_run
+//! # use bdk::bitcoin::Network;
+//! # use bdk::signer::SignerOrdering;
+//! # use bdk_hwi::HWISigner;
+//! # use bdk::wallet::AddressIndex::New;
+//! # use bdk::{FeeRate, KeychainKind, SignOptions, Wallet};
+//! # use hwi::HWIClient;
+//! # use std::sync::Arc;
+//! #
+//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! let mut devices = HWIClient::enumerate()?;
+//! if devices.is_empty() {
+//!     panic!("No devices found!");
+//! }
+//! let first_device = devices.remove(0)?;
+//! let custom_signer = HWISigner::from_device(&first_device, Network::Testnet.into())?;
+//!
+//! # let mut wallet = Wallet::new_no_persist(
+//! #     "",
+//! #     None,
+//! #     Network::Testnet,
+//! # )?;
+//! #
+//! // Adding the hardware signer to the BDK wallet
+//! wallet.add_signer(
+//!     KeychainKind::External,
+//!     SignerOrdering(200),
+//!     Arc::new(custom_signer),
+//! );
+//!
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! [`TransactionSigner`]: bdk::wallet::signer::TransactionSigner
+
+mod signer;
+pub use signer::*;

crates/hwi/src/signer.rs

@@ -0,0 +1,94 @@
+use bdk::bitcoin::bip32::Fingerprint;
+use bdk::bitcoin::psbt::PartiallySignedTransaction;
+use bdk::bitcoin::secp256k1::{All, Secp256k1};
+
+use hwi::error::Error;
+use hwi::types::{HWIChain, HWIDevice};
+use hwi::HWIClient;
+
+use bdk::signer::{SignerCommon, SignerError, SignerId, TransactionSigner};
+
+#[derive(Debug)]
+/// Custom signer for Hardware Wallets
+///
+/// This ignores `sign_options` and leaves the decisions up to the hardware wallet.
+pub struct HWISigner {
+    fingerprint: Fingerprint,
+    client: HWIClient,
+}
+
+impl HWISigner {
+    /// Create a instance from the specified device and chain
+    pub fn from_device(device: &HWIDevice, chain: HWIChain) -> Result<HWISigner, Error> {
+        let client = HWIClient::get_client(device, false, chain)?;
+        Ok(HWISigner {
+            fingerprint: device.fingerprint,
+            client,
+        })
+    }
+}
+
+impl SignerCommon for HWISigner {
+    fn id(&self, _secp: &Secp256k1<All>) -> SignerId {
+        SignerId::Fingerprint(self.fingerprint)
+    }
+}
+
+impl TransactionSigner for HWISigner {
+    fn sign_transaction(
+        &self,
+        psbt: &mut PartiallySignedTransaction,
+        _sign_options: &bdk::SignOptions,
+        _secp: &Secp256k1<All>,
+    ) -> Result<(), SignerError> {
+        psbt.combine(
+            self.client
+                .sign_tx(psbt)
+                .map_err(|e| {
+                    SignerError::External(format!("While signing with hardware wallet: {}", e))
+                })?
+                .psbt,
+        )
+        .expect("Failed to combine HW signed psbt with passed PSBT");
+        Ok(())
+    }
+}
+
+// TODO: re-enable this once we have the `get_funded_wallet` test util
+// #[cfg(test)]
+// mod tests {
+//     #[test]
+//     fn test_hardware_signer() {
+//         use std::sync::Arc;
+//
+//         use bdk::tests::get_funded_wallet;
+//         use bdk::signer::SignerOrdering;
+//         use bdk::bitcoin::Network;
+//         use crate::HWISigner;
+//         use hwi::HWIClient;
+//
+//         let mut devices = HWIClient::enumerate().unwrap();
+//         if devices.is_empty() {
+//             panic!("No devices found!");
+//         }
+//         let device = devices.remove(0).unwrap();
+//         let client = HWIClient::get_client(&device, true, Network::Regtest.into()).unwrap();
+//         let descriptors = client.get_descriptors::<String>(None).unwrap();
+//         let custom_signer = HWISigner::from_device(&device, Network::Regtest.into()).unwrap();
+//
+//         let (mut wallet, _) = get_funded_wallet(&descriptors.internal[0]);
+//         wallet.add_signer(
+//             bdk::KeychainKind::External,
+//             SignerOrdering(200),
+//             Arc::new(custom_signer),
+//         );
+//
+//         let addr = wallet.get_address(bdk::wallet::AddressIndex::LastUnused);
+//         let mut builder = wallet.build_tx();
+//         builder.drain_to(addr.script_pubkey()).drain_wallet();
+//         let (mut psbt, _) = builder.finish().unwrap();
+//
+//         let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
+//         assert!(finalized);
+//     }
+// }