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use bitcoin::bip32;
use std::str::FromStr;
#[derive(Debug, PartialEq, Eq)]
pub enum Wildcard {
None,
Unhardened,
Hardened,
}
#[derive(Debug, Clone)]
pub struct ParseError(&'static str);
impl std::fmt::Display for ParseError {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(f, "Error while parsing policy: {}", self.0)
}
}
/// from https://github.com/rust-bitcoin/rust-miniscript/blob/master/src/descriptor/key.rs#L780
pub fn parse_xkey_deriv(
key_deriv: &str,
) -> Result<(Vec<bip32::DerivationPath>, Wildcard), ParseError> {
let mut wildcard = Wildcard::None;
let mut multipath = false;
let derivation_paths = key_deriv
.replace("**", "<0;1>/*")
.split('/')
.filter_map(|p| {
if wildcard == Wildcard::None && p == "*" {
wildcard = Wildcard::Unhardened;
None
} else if wildcard == Wildcard::None && (p == "*'" || p == "*h") {
wildcard = Wildcard::Hardened;
None
} else if wildcard != Wildcard::None {
Some(Err(ParseError(
"'*' may only appear as last element in a derivation path.",
)))
} else {
// BIP389 defines a new step in the derivation path. This step contains two or more
// derivation indexes in the form '<1;2;3';4h;5H;6>'.
if p.starts_with('<') && p.ends_with('>') {
// There may only be one occurence of this step.
if multipath {
return Some(Err(ParseError(
"'<' may only appear once in a derivation path.",
)));
}
multipath = true;
// The step must contain at least two derivation indexes.
// So it's at least '<' + a number + ';' + a number + '>'.
if p.len() < 5 || !p.contains(';') {
return Some(Err(ParseError(
"Invalid multi index step in multipath descriptor.",
)));
}
// Collect all derivation indexes at this step.
let indexes = p[1..p.len() - 1].split(';');
Some(
indexes
.into_iter()
.map(|s| {
bip32::ChildNumber::from_str(s).map_err(|_| {
ParseError("Error while parsing index in key derivation path.")
})
})
.collect::<Result<Vec<bip32::ChildNumber>, _>>(),
)
} else {
// Not a BIP389 step, just a regular derivation index.
Some(
bip32::ChildNumber::from_str(p)
.map(|i| vec![i])
.map_err(|_| ParseError("Error while parsing key derivation path")),
)
}
}
})
// Now we've got all derivation indexes in a list of vectors of indexes. If the derivation
// path was empty then this list is empty. If the derivation path didn't contain any BIP389
// step all the vectors of indexes contain a single element. If it did though, one of the
// vectors contains more than one element.
// Now transform this list of vectors of steps into distinct derivation paths.
.try_fold(Vec::new(), |mut paths, index_list| {
let mut index_list = index_list?.into_iter();
let first_index = index_list
.next()
.expect("There is always at least one element");
if paths.is_empty() {
paths.push(vec![first_index]);
} else {
for path in paths.iter_mut() {
path.push(first_index);
}
}
// If the step is a BIP389 one, create as many paths as there is indexes.
for (i, index) in index_list.enumerate() {
paths.push(paths[0].clone());
*paths[i + 1].last_mut().expect("Never empty") = index;
}
Ok(paths)
})?
.into_iter()
.map(|index_list| index_list.into_iter().collect::<bip32::DerivationPath>())
.collect::<Vec<bip32::DerivationPath>>();
Ok((derivation_paths, wildcard))
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_parse_xkey_deriv() {
// We can have a key in a descriptor that has multiple paths
let (paths, wildcard) = parse_xkey_deriv("2/<0;1;42;9854>").unwrap();
assert_eq!(wildcard, Wildcard::None);
assert_eq!(
paths,
vec![
bip32::DerivationPath::from_str("m/2/0").unwrap(),
bip32::DerivationPath::from_str("m/2/1").unwrap(),
bip32::DerivationPath::from_str("m/2/42").unwrap(),
bip32::DerivationPath::from_str("m/2/9854").unwrap()
],
);
// Even if it's in the middle of the derivation path.
let (paths, wildcard) = parse_xkey_deriv("2/<0;1;9854>/0/5/10").unwrap();
assert_eq!(wildcard, Wildcard::None);
assert_eq!(
paths,
vec![
bip32::DerivationPath::from_str("m/2/0/0/5/10").unwrap(),
bip32::DerivationPath::from_str("m/2/1/0/5/10").unwrap(),
bip32::DerivationPath::from_str("m/2/9854/0/5/10").unwrap()
],
);
// Even if it is a wildcard extended key.
let (paths, wildcard) = parse_xkey_deriv("2/<0;1;9854>/3456/9876/*").unwrap();
assert_eq!(wildcard, Wildcard::Unhardened);
assert_eq!(
paths,
vec![
bip32::DerivationPath::from_str("m/2/0/3456/9876").unwrap(),
bip32::DerivationPath::from_str("m/2/1/3456/9876").unwrap(),
bip32::DerivationPath::from_str("m/2/9854/3456/9876").unwrap()
],
);
// Also even if it has an origin.
let (paths, wildcard) = parse_xkey_deriv("<0;1>/*").unwrap();
assert_eq!(wildcard, Wildcard::Unhardened);
assert_eq!(
paths,
vec![
bip32::DerivationPath::from_str("m/0").unwrap(),
bip32::DerivationPath::from_str("m/1").unwrap(),
],
);
// Also if it has hardened steps in the derivation path. In fact, it can also have hardened
// indexes even at the step with multiple indexes!
let (paths, wildcard) = parse_xkey_deriv("9478'/<0';1h>/8h/*'").unwrap();
assert_eq!(wildcard, Wildcard::Hardened);
assert_eq!(
paths,
vec![
bip32::DerivationPath::from_str("m/9478'/0'/8'").unwrap(),
bip32::DerivationPath::from_str("m/9478h/1h/8h").unwrap(),
],
);
// It's invalid to:
// - Not have opening or closing brackets
// - Have multiple steps with different indexes
// - Only have one index within the brackets
parse_xkey_deriv("2/<0;1;42;9854").unwrap_err();
parse_xkey_deriv("2/0;1;42;9854>").unwrap_err();
parse_xkey_deriv("2/4/<0;1>/96/<0;1>").unwrap_err();
parse_xkey_deriv("2/4/<0>").unwrap_err();
parse_xkey_deriv("2/4/<0;>").unwrap_err();
parse_xkey_deriv("2/4/<;1>").unwrap_err();
parse_xkey_deriv("2/4/<0;1;>").unwrap_err();
}
}