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descriptors: fix the signatures count analysis

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Since https://github.com/wizardsardine/liana/pull/575 we started using
xpubs with an appended derivation path, and the analysis was assuming
there wasn't any.
This commit is contained in:
Antoine Poinsot 2023-07-26 19:03:10 +02:00
parent 7a33040b83
commit 10acc482e1
No known key found for this signature in database
GPG Key ID: E13FC145CD3F4304
1 changed files with 65 additions and 39 deletions
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104
src/descriptors/analysis.rs
View File

@ -130,13 +130,27 @@ fn csv_check(csv_value: u32) -> Result<u16, LianaPolicyError> {
}
}
// Get the origin of a key in a multipath descriptors.
// Returns None if the given key isn't a multixpub.
fn key_origin(
// Get the fingerprint and the full derivation paths (path from the master fingerprint in the
// origin, with the xpub derivation path appended) for a multipath xpub.
fn key_origins(
key: &descriptor::DescriptorPublicKey,
) -> Option<&(bip32::Fingerprint, bip32::DerivationPath)> {
) -> Option<(bip32::Fingerprint, HashSet<bip32::DerivationPath>)> {
match key {
descriptor::DescriptorPublicKey::MultiXPub(ref xpub) => xpub.origin.as_ref(),
descriptor::DescriptorPublicKey::MultiXPub(ref xpub) => {
xpub.origin.as_ref().map(|(fg, orig_path)| {
let mut der_paths = HashSet::with_capacity(xpub.derivation_paths.paths().len());
for der_path in xpub.derivation_paths.paths() {
der_paths.insert(
orig_path
.into_iter()
.chain(der_path.into_iter())
.copied()
.collect(),
);
}
(*fg, der_paths)
})
}
_ => None,
}
}
@ -241,28 +255,36 @@ impl PathInfo {
}
/// Get the required number of keys for spending through this path, and the set of keys
/// that can be used to provide a signature for this path.
pub fn thresh_origins(&self) -> (usize, HashSet<(bip32::Fingerprint, bip32::DerivationPath)>) {
/// that can be used to provide a signature for this path. The set of keys is represented as a
/// mapping from a master extended key fingerprint, to a set of derivation paths. This is
/// because we are using multipath descriptors. The derivation paths included the xpub's
/// derivation path appended to the origin's derivation path (without the wildcard step).
pub fn thresh_origins(
&self,
) -> (
usize,
HashMap<bip32::Fingerprint, HashSet<bip32::DerivationPath>>,
) {
match self {
PathInfo::Single(key) => {
let mut origins = HashSet::with_capacity(1);
origins.insert(
key_origin(key)
.expect("Must be a multixpub with an origin.")
.clone(),
);
(1, origins)
let mut all_origins = HashMap::with_capacity(1);
let (fg, der_path) = key_origins(key).expect("Must be a multixpub with an origin.");
all_origins.insert(fg, der_path);
(1, all_origins)
}
PathInfo::Multi(k, keys) => {
let mut all_origins: HashMap<_, HashSet<_>> = HashMap::with_capacity(keys.len());
for key in keys {
let (fg, der_paths) =
key_origins(key).expect("Must be a multixpub with an origin.");
if let Some(existing_der_paths) = all_origins.get_mut(&fg) {
existing_der_paths.extend(der_paths)
} else {
all_origins.insert(fg, der_paths);
}
}
(*k, all_origins)
}
PathInfo::Multi(k, keys) => (
*k,
keys.iter()
.map(|key| {
key_origin(key)
.expect("Must be a multixpub with an origin.")
.clone()
})
.collect(),
),
}
}
@ -278,24 +300,28 @@ impl PathInfo {
// For all existing signatures, pick those that are from one of our pubkeys.
for (fg, der_path) in all_pubkeys_signed {
// For all xpubs in the descriptor, we derive at /0/* or /1/*, so the xpub's origin's
// derivation path is the key's one without the last two derivation indexes.
if der_path.len() < 2 {
// All xpubs in the descriptor must be wildcard, and therefore have a derivation with
// at least one step. (In practice there is at least two, for `/<0;1>/*`.)
if der_path.is_empty() {
continue;
}
let parent_der_path: bip32::DerivationPath = der_path[..der_path.len() - 2].into();
let parent_origin = (*fg, parent_der_path);
// Now if the origin of this key without the two final derivation indexes is part of
// the set of our keys, count it as a signature for it. Note it won't mixup keys
// between spending paths, since we can't have duplicate xpubs in the descriptor and
// the (fingerprint, der_path) tuple is a UID for an xpub.
if origins.contains(&parent_origin) {
sigs_count += 1;
if let Some(count) = signed_pubkeys.get_mut(&parent_origin.0) {
*count += 1;
} else {
signed_pubkeys.insert(parent_origin.0, 1);
// Now check if this signature is for a public key derived from the fingerprint of one
// of our known master xpubs.
if let Some(parent_der_paths) = origins.get(fg) {
// If it is, make sure it's for one of the xpubs included in the descriptor. Remove
// the wilcard step and check if it's in the set of the derivation paths.
let der_path_wo_wc: bip32::DerivationPath = der_path[..der_path.len() - 1].into();
if parent_der_paths.contains(&der_path_wo_wc) {
// If the origin of the key without the wilcard step is part of our keys, count
// it as a signature. Also record how many times this master extended key
// signed.
sigs_count += 1;
if let Some(count) = signed_pubkeys.get_mut(fg) {
*count += 1;
} else {
signed_pubkeys.insert(*fg, 1);
}
}
}
}