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refactor(chain): calculate DescriptorId as sha256 hash of spk at index 0

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Also update docs to explain how KeychainTxOutIndex handles descriptors that
generate the same spks.
This commit is contained in:
Steve Myers 2024-06-25 10:51:51 -05:00
parent 6dab68d35b
commit 46c6f18cc3
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GPG Key ID: 8105A46B22C2D051
3 changed files with 16 additions and 12 deletions
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18
crates/chain/src/descriptor_ext.rs
View File

@ -1,12 +1,8 @@
use crate::{
alloc::{string::ToString, vec::Vec},
miniscript::{Descriptor, DescriptorPublicKey},
};
use crate::miniscript::{Descriptor, DescriptorPublicKey};
use bitcoin::hashes::{hash_newtype, sha256, Hash};
hash_newtype! {
/// Represents the ID of a descriptor, defined as the sha256 hash of
/// the descriptor string, checksum excluded.
/// Represents the unique ID of a descriptor.
///
/// This is useful for having a fixed-length unique representation of a descriptor,
/// in particular, we use it to persist application state changes related to the
@ -21,8 +17,8 @@ pub trait DescriptorExt {
/// Panics if the descriptor wildcard is hardened.
fn dust_value(&self) -> u64;
/// Returns the descriptor id, calculated as the sha256 of the descriptor, checksum not
/// included.
/// Returns the descriptor ID, calculated as the sha256 hash of the spk derived from the
/// descriptor at index 0.
fn descriptor_id(&self) -> DescriptorId;
}
@ -36,9 +32,7 @@ impl DescriptorExt for Descriptor<DescriptorPublicKey> {
}
fn descriptor_id(&self) -> DescriptorId {
let desc = self.to_string();
let desc_without_checksum = desc.split('#').next().expect("Must be here");
let descriptor_bytes = <Vec<u8>>::from(desc_without_checksum.as_bytes());
DescriptorId(sha256::Hash::hash(&descriptor_bytes))
let spk = self.at_derivation_index(0).unwrap().script_pubkey();
DescriptorId(sha256::Hash::hash(spk.as_bytes()))
}
}

7
crates/chain/src/keychain/txout_index.rs
View File

@ -352,6 +352,13 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
///
/// keychain <-> descriptor is a one-to-one mapping that cannot be changed. Attempting to do so
/// will return a [`InsertDescriptorError<K>`].
///
/// `[KeychainTxOutIndex]` will prevent you from inserting two descriptors which derive the same
/// script pubkey at index 0, but it's up to you to ensure that descriptors don't collide at
/// other indices. If they do nothing catastrophic happens at the `KeychainTxOutIndex` level
/// (one keychain just becomes the defacto owner of that spk arbitrarily) but this may have
/// subtle implications up the application stack like one UTXO being missing from one keychain
/// because it has been assigned to another which produces the same script pubkey.
pub fn insert_descriptor(
&mut self,
keychain: K,

3
crates/wallet/src/wallet/mod.rs
View File

@ -91,6 +91,9 @@ const COINBASE_MATURITY: u32 = 100;
/// [`ChangeSet`]s (see [`take_staged`]). Also see individual functions and example for instructions
/// on when [`Wallet`] state needs to be persisted.
///
/// The `Wallet` descriptor (external) and change descriptor (internal) must not derive the same
/// script pubkeys. See [`KeychainTxOutIndex::insert_descriptor()`] for more details.
///
/// [`signer`]: crate::signer
/// [`take_staged`]: Wallet::take_staged
#[derive(Debug)]