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descriptors: lift the bounds to create a Liana policy

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Since we now use the Miniscript compiler, there is no reason not to
allow more than 20 keys.
This commit is contained in:
Antoine Poinsot 2023-03-24 19:16:58 +01:00
parent 55d86c62a5
commit ec0009113a
No known key found for this signature in database
GPG Key ID: E13FC145CD3F4304
2 changed files with 45 additions and 41 deletions
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64
src/descriptors/analysis.rs
View File

@ -1,7 +1,7 @@
use miniscript::{
bitcoin::{util::bip32, Sequence},
descriptor,
policy::{Concrete as ConcretePolicy, Liftable, Semantic as SemanticPolicy},
policy::{compiler, Concrete as ConcretePolicy, Liftable, Semantic as SemanticPolicy},
ScriptContext,
};
@ -19,6 +19,9 @@ pub enum LianaPolicyError {
InvalidMultiThresh(usize),
InvalidMultiKeys(usize),
IncompatibleDesc,
/// The spending policy is not a valid Miniscript policy: it may for instance be malleable, or
/// overflow some limit.
InvalidPolicy(compiler::CompilerError),
}
impl std::fmt::Display for LianaPolicyError {
@ -43,6 +46,7 @@ impl std::fmt::Display for LianaPolicyError {
f,
"Descriptor is not compatible with a Liana spending policy."
),
Self::InvalidPolicy(e) => write!(f, "Invalid Miniscript policy: {}", e),
}
}
}
@ -303,6 +307,8 @@ impl PathInfo {
/// A Liana spending policy. Can be created from some settings (the primary and recovery keys, the
/// timelock(s)) and be used to derive a descriptor. It can also be inferred from a descriptor and
/// be used to retrieve the settings.
/// Do note however that the descriptor generation process is not deterministic, therefore you
/// **cannot roundtrip** a descriptor through a `LianaPolicy`.
#[derive(Debug, Eq, PartialEq, Clone, Ord, PartialOrd, Hash)]
pub struct LianaPolicy {
pub(super) primary_path: PathInfo,
@ -327,18 +333,6 @@ impl LianaPolicy {
return Err(LianaPolicyError::InsaneTimelock(recovery_timelock as u32));
}
// If any of the paths is a multisig, make sure they are within the CHECKMULTISIG bounds.
for path_info in &[&primary_path, &recovery_path] {
if let PathInfo::Multi(thresh, keys) = path_info {
if keys.len() < 2 || keys.len() > 20 {
return Err(LianaPolicyError::InvalidMultiKeys(keys.len()));
}
if thresh == &0 || thresh > &keys.len() {
return Err(LianaPolicyError::InvalidMultiThresh(*thresh));
}
}
}
// Check all keys are valid according to our standard (this checks all are multipath keys).
let (prim_keys, rec_keys) = (primary_path.keys(), recovery_path.keys());
let all_keys = prim_keys.iter().chain(rec_keys.iter());
@ -346,7 +340,8 @@ impl LianaPolicy {
return Err(LianaPolicyError::InvalidKey((*key).clone().into()));
}
// Check for key duplicates. They are invalid in (nonmalleable) miniscripts.
// Check for key duplicates. They are invalid in (nonmalleable) miniscripts. This is
// checked by the Miniscript policy compiler too but not at the raw xpub level.
let mut key_set = HashSet::new();
for key in all_keys {
let xpub = match key {
@ -360,10 +355,13 @@ impl LianaPolicy {
}
assert!(!key_set.is_empty());
Ok(LianaPolicy {
// Make sure it is a valid Miniscript policy by (ab)using the compiler.
let policy = LianaPolicy {
primary_path,
recovery_path: (recovery_timelock, recovery_path),
})
};
policy.clone().into_miniscript()?;
Ok(policy)
}
/// Create a Liana policy from a descriptor. This will check the descriptor is correctly formed
@ -439,10 +437,10 @@ impl LianaPolicy {
}
}
Ok(LianaPolicy {
primary_path: primary_path.ok_or(LianaPolicyError::IncompatibleDesc)?,
recovery_path: recovery_path.ok_or(LianaPolicyError::IncompatibleDesc)?,
})
// Use the constructor for the sanity checks (especially around the Miniscript policy).
let prim_path = primary_path.ok_or(LianaPolicyError::IncompatibleDesc)?;
let (timelock, reco_path) = recovery_path.ok_or(LianaPolicyError::IncompatibleDesc)?;
LianaPolicy::new(prim_path, reco_path, timelock)
}
pub fn primary_path(&self) -> &PathInfo {
@ -454,12 +452,12 @@ impl LianaPolicy {
(self.recovery_path.0, &self.recovery_path.1)
}
/// Create a descriptor from this spending policy with multipath key expressions.
///
/// Although for now this function is deterministic, it **will not** be in the future.
pub fn into_multipath_descriptor(
fn into_miniscript(
self,
) -> descriptor::Descriptor<descriptor::DescriptorPublicKey> {
) -> Result<
miniscript::Miniscript<descriptor::DescriptorPublicKey, miniscript::Segwitv0>,
LianaPolicyError,
> {
let LianaPolicy {
primary_path,
recovery_path: (timelock, recovery_path),
@ -475,9 +473,21 @@ impl LianaPolicy {
let primary_keys = primary_path.into_ms_policy();
let tl_policy = ConcretePolicy::Or(vec![(99, primary_keys), (1, recovery_branch)]);
let ms = tl_policy
tl_policy
.compile::<miniscript::Segwitv0>()
.expect("Compilation must never fail, nothing overflows.");
.map_err(LianaPolicyError::InvalidPolicy)
}
/// Create a descriptor from this spending policy with multipath key expressions. Note this
/// involves a Miniscript policy compilation: this function is **not deterministic**. If you
/// are inferring a `LianaPolicy` from a descriptor, generating a descriptor from this
/// `LianaPolicy` may not yield the same descriptor.
pub fn into_multipath_descriptor(
self,
) -> descriptor::Descriptor<descriptor::DescriptorPublicKey> {
let ms = self
.into_miniscript()
.expect("This is always checked when creating a LianaPolicy.");
miniscript::Segwitv0::check_local_validity(&ms).expect("Miniscript must be sane");
descriptor::Descriptor::Wsh(descriptor::Wsh::new(ms).expect("Must pass sanity checks"))
}

22
src/descriptors/mod.rs
View File

@ -584,17 +584,11 @@ mod tests {
descriptor::DescriptorPublicKey::from_str(&xpub_str).unwrap()
};
let prim_path = PathInfo::Single(random_desc_key());
let twenty_keys: Vec<descriptor::DescriptorPublicKey> =
(0..20).map(|_| random_desc_key()).collect();
let mut twenty_one_keys = twenty_keys.clone();
twenty_one_keys.push(random_desc_key());
let twenty_eight_keys: Vec<descriptor::DescriptorPublicKey> =
(0..28).map(|_| random_desc_key()).collect();
let mut twenty_nine_keys = twenty_eight_keys.clone();
twenty_nine_keys.push(random_desc_key());
LianaPolicy::new(
prim_path.clone(),
PathInfo::Multi(1, vec![random_desc_key()]),
1,
)
.unwrap_err();
LianaPolicy::new(
prim_path.clone(),
PathInfo::Multi(2, vec![random_desc_key()]),
@ -627,12 +621,12 @@ mod tests {
.unwrap_err();
LianaPolicy::new(
prim_path.clone(),
PathInfo::Multi(3, twenty_keys.clone()),
PathInfo::Multi(3, twenty_eight_keys.clone()),
1,
)
.unwrap();
LianaPolicy::new(prim_path.clone(), PathInfo::Multi(20, twenty_keys), 1).unwrap();
LianaPolicy::new(prim_path, PathInfo::Multi(20, twenty_one_keys), 1).unwrap_err();
LianaPolicy::new(prim_path.clone(), PathInfo::Multi(20, twenty_eight_keys), 1).unwrap();
LianaPolicy::new(prim_path, PathInfo::Multi(20, twenty_nine_keys), 1).unwrap_err();
}
fn roundtrip(desc_str: &str) {
@ -649,7 +643,7 @@ mod tests {
// A single key as primary path, a multisig as recovery
roundtrip("wsh(or_d(pk([aabbccdd]xpub6Eze7yAT3Y1wGrnzedCNVYDXUqa9NmHVWck5emBaTbXtURbe1NWZbK9bsz1TiVE7Cz341PMTfYgFw1KdLWdzcM1UMFTcdQfCYhhXZ2HJvTW/<0;1>/*),and_v(v:multi(2,[aabbccdd]xpub69cP4Y7S9TWcbSNxmk6CEDBsoaqr3ZEdjHuZcHxEFFKGh569RsJNr2V27XGhsbH9FXgWUEmKXRN7c5wQfq2VPjt31xP9VsYnVUyU8HcVevm/<0;1>/*,[aabbccdd]xpub6AA2N8RALRYgLD6jT1iXYCEDkndTeZndMtWPbtNX6sY5dPiLtf2T88ahdxrGXMUPoNadgR86sFhBXWQVgifPzDYbY9ZtwK4gqzx4y5Da1DW/<0;1>/*,[aabb0011/10/4893]xpub6AyxexvxizZJffF153evmfqHcE9MV88fCNCAtP3jQjXJHwrAKri71Tq9jWUkPxj9pja4u6AkCPHY7atgxzSEa2HtDwJfrRWKK4fsfQg4o77/<0;1>/*),older(26352))))#7du8x4v7");
// The other way around
roundtrip("wsh(or_d(multi(3,[aabbccdd]xpub6Eze7yAT3Y1wGrnzedCNVYDXUqa9NmHVWck5emBaTbXtURbe1NWZbK9bsz1TiVE7Cz341PMTfYgFw1KdLWdzcM1UMFTcdQfCYhhXZ2HJvTW/<0;1>/*,[aabb0011/10/4893]xpub6Bw79HbNSeS2xXw1sngPE3ehnk1U3iSPCgLYzC9LpN8m9nDuaKLZvkg8QXxL5pDmEmQtYscmUD8B9MkAAZbh6vxPzNXMaLfGQ9Sb3z85qhR/<0;1>/*,[aabbccdd]xpub67zuTXF9Ln4731avKTBSawoVVNRuMfmRvkL7kLUaLBRqma9ZqdHBJg9qx8cPUm3oNQMiXT4TmGovXNoQPuwg17RFcVJ8YrnbcooN7pxVJqC/<0;1>/*),and_v(v:pk([aabbccdd]xpub6Eze7yAT3Y1wGrnzedCNVYDXUqa9NmHVWck5emBaTbXtURbe1NWZbK9bsz1TiVE7Cz341PMTfYgFw1KdLWdzcM1UMFTcdQfCYhhXZ2HJvTW/<0;1>/*),older(26352))))#y9l4ldvr");
roundtrip("wsh(or_d(multi(3,[aabbccdd]xpub6Eze7yAT3Y1wGrnzedCNVYDXUqa9NmHVWck5emBaTbXtURbe1NWZbK9bsz1TiVE7Cz341PMTfYgFw1KdLWdzcM1UMFTcdQfCYhhXZ2HJvTW/<0;1>/*,[aabb0011/10/4893]xpub6Bw79HbNSeS2xXw1sngPE3ehnk1U3iSPCgLYzC9LpN8m9nDuaKLZvkg8QXxL5pDmEmQtYscmUD8B9MkAAZbh6vxPzNXMaLfGQ9Sb3z85qhR/<0;1>/*,[aabbccdd]xpub67zuTXF9Ln4731avKTBSawoVVNRuMfmRvkL7kLUaLBRqma9ZqdHBJg9qx8cPUm3oNQMiXT4TmGovXNoQPuwg17RFcVJ8YrnbcooN7pxVJqC/<0;1>/*),and_v(v:pk([aabbccdd]xpub69cP4Y7S9TWcbSNxmk6CEDBsoaqr3ZEdjHuZcHxEFFKGh569RsJNr2V27XGhsbH9FXgWUEmKXRN7c5wQfq2VPjt31xP9VsYnVUyU8HcVevm/<0;1>/*),older(26352))))#0y77q9d6");
}
fn psbt_from_str(psbt_str: &str) -> Psbt {