Use KeySource instead of definite keys in Assets

Author: danielabrozzoni

src/descriptor/key.rs

@@ -721,41 +721,6 @@ impl DescriptorPublicKey {
             }
         }
     }
-
-    /// Whether this key is the "parent" of a [`DefiniteDescriptorKey`]
-    ///
-    /// The key is considered "parent" if it represents the non-derived version of a definite key,
-    /// meaning it contains a wildcard where the definite key has a definite derivation number.
-    ///
-    /// If `self` is a single key or doesn't contain any wildcards, the definite key will have to
-    /// be exactly the same.
-    ///
-    /// Returns the derivation path to apply to `self` to obtain the definite key.
-    pub fn is_parent(&self, definite_key: &DefiniteDescriptorKey) -> Option<bip32::DerivationPath> {
-        // If the key is `Single` or it's an `XPub` with no wildcard it will match the definite key
-        // exactly, so we try this check first
-        if self == &definite_key.0 {
-            return Some(bip32::DerivationPath::default());
-        }
-
-        match (self, &definite_key.0) {
-            (DescriptorPublicKey::XPub(self_xkey), DescriptorPublicKey::XPub(definite_xkey))
-                if definite_xkey.derivation_path.len() > 0 =>
-            {
-                let definite_path_len = definite_xkey.derivation_path.len();
-                if self_xkey.origin == definite_xkey.origin
-                    && self_xkey.xkey == definite_xkey.xkey
-                    && self_xkey.derivation_path.as_ref()
-                        == &definite_xkey.derivation_path[..(definite_path_len - 1)]
-                {
-                    Some(vec![definite_xkey.derivation_path[definite_path_len - 1]].into())
-                } else {
-                    None
-                }
-            }
-            _ => None,
-        }
-    }
 }
 
 impl FromStr for DescriptorSecretKey {

src/plan.rs

@@ -535,8 +535,12 @@ impl TaprootAvailableLeaves {
 /// The Assets we can use to satisfy a particular spending path
 #[derive(Debug, Default)]
 pub struct Assets {
-    /// Keys the user can sign for, and how
-    pub keys: HashSet<(DescriptorPublicKey, CanSign)>,
+    /// Keys the user can sign for, and how. A pair `(fingerprint, derivation_path)` is
+    /// provided, meaning that the user can sign using the key with `fingerprint`,
+    /// derived with either `derivation_path` or a derivation path that extends `derivation_path`
+    /// by exactly one child number. For example, if the derivation path `m/0/1` is provided, the
+    /// user can sign with either `m/0/1` or `m/0/1/*`.
+    pub keys: HashSet<(bip32::KeySource, CanSign)>,
     /// Set of available sha256 preimages
     pub sha256_preimages: HashSet<sha256::Hash>,
     /// Set of available hash256 preimages
@@ -551,16 +555,44 @@ pub struct Assets {
     pub relative_timelock: Option<Sequence>,
 }
 
+// Checks if the `pk` is a "direct child" of the `derivation_path` provided.
+// Direct child means that the key derivation path is either the same as the
+// `derivation_path`, or the same extened by exactly one child number.
+// For example, `pk/0/1/2` is a direct child of `m/0/1` and of `m/0/1/2`,
+// but not of `m/0`.
+fn is_key_direct_child_of(
+    pk: &DefiniteDescriptorKey,
+    derivation_path: &bip32::DerivationPath,
+) -> bool {
+    for pk_derivation_path in pk.full_derivation_paths() {
+        if &pk_derivation_path == derivation_path {
+            return true;
+        }
+
+        let definite_path_len = pk_derivation_path.len();
+        if derivation_path.as_ref() == &pk_derivation_path[..(definite_path_len - 1)] {
+            return true;
+        }
+    }
+
+    false
+}
+
 impl Assets {
     pub(crate) fn has_ecdsa_key(&self, pk: &DefiniteDescriptorKey) -> bool {
-        self.keys
-            .iter()
-            .any(|(key, can_sign)| can_sign.ecdsa && key.is_parent(pk).is_some())
+        self.keys.iter().any(|(keysource, can_sign)| {
+            can_sign.ecdsa
+                && pk.master_fingerprint() == keysource.0
+                && is_key_direct_child_of(pk, &keysource.1)
+        })
     }
 
     pub(crate) fn has_taproot_internal_key(&self, pk: &DefiniteDescriptorKey) -> Option<usize> {
-        self.keys.iter().find_map(|(key, can_sign)| {
-            if !can_sign.taproot.key_spend || !key.is_parent(pk).is_some() {
+        self.keys.iter().find_map(|(keysource, can_sign)| {
+            if !can_sign.taproot.key_spend
+                || pk.master_fingerprint() != keysource.0
+                || !is_key_direct_child_of(pk, &keysource.1)
+            {
                 None
             } else {
                 Some(can_sign.taproot.sig_len())
@@ -573,9 +605,10 @@ impl Assets {
         pk: &DefiniteDescriptorKey,
         tap_leaf_hash: &TapLeafHash,
     ) -> Option<usize> {
-        self.keys.iter().find_map(|(key, can_sign)| {
+        self.keys.iter().find_map(|(keysource, can_sign)| {
             if !can_sign.taproot.script_spend.is_available(tap_leaf_hash)
-                || !key.is_parent(pk).is_some()
+                || pk.master_fingerprint() != keysource.0
+                || !is_key_direct_child_of(pk, &keysource.1)
             {
                 None
             } else {
@@ -640,11 +673,14 @@ impl AssetProvider<DefiniteDescriptorKey> for Assets {
 
 impl FromIterator<DescriptorPublicKey> for Assets {
     fn from_iter<I: IntoIterator<Item = DescriptorPublicKey>>(iter: I) -> Self {
+        let mut keys = HashSet::new();
+        for pk in iter {
+            for deriv_path in pk.full_derivation_paths() {
+                keys.insert(((pk.master_fingerprint(), deriv_path), CanSign::default()));
+            }
+        }
         Assets {
-            keys: iter
-                .into_iter()
-                .map(|pk| (pk, CanSign::default()))
-                .collect(),
+            keys,
             ..Default::default()
         }
     }