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// Miniscript
// Written in 2020 by rust-miniscript developers
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//
//! # Sorted Multi
//!
//! Implementation of sorted multi primitive for descriptors
//!
use core::fmt;
use core::marker::PhantomData;
use core::str::FromStr;
use bitcoin::blockdata::script;
use crate::miniscript::context::ScriptContext;
use crate::miniscript::decode::Terminal;
use crate::miniscript::limits::MAX_PUBKEYS_PER_MULTISIG;
use crate::prelude::*;
use crate::{
errstr, expression, miniscript, policy, script_num_size, Error, ForEachKey, Miniscript,
MiniscriptKey, Satisfier, ToPublicKey, Translator,
};
/// Contents of a "sortedmulti" descriptor
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SortedMultiVec<Pk: MiniscriptKey, Ctx: ScriptContext> {
/// signatures required
pub k: usize,
/// public keys inside sorted Multi
pub pks: Vec<Pk>,
/// The current ScriptContext for sortedmulti
pub(crate) phantom: PhantomData<Ctx>,
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> SortedMultiVec<Pk, Ctx> {
/// Create a new instance of `SortedMultiVec` given a list of keys and the threshold
///
/// Internally checks all the applicable size limits and pubkey types limitations according to the current `Ctx`.
pub fn new(k: usize, pks: Vec<Pk>) -> Result<Self, Error> {
// A sortedmulti() is only defined for <= 20 keys (it maps to CHECKMULTISIG)
if pks.len() > MAX_PUBKEYS_PER_MULTISIG {
return Err(Error::BadDescriptor("Too many public keys".to_string()));
}
// Check the limits before creating a new SortedMultiVec
// For example, under p2sh context the scriptlen can only be
// upto 520 bytes.
let term: miniscript::decode::Terminal<Pk, Ctx> = Terminal::Multi(k, pks.clone());
let ms = Miniscript::from_ast(term)?;
// This would check all the consensus rules for p2sh/p2wsh and
// even tapscript in future
Ctx::check_local_validity(&ms)?;
Ok(Self {
k,
pks,
phantom: PhantomData,
})
}
/// Parse an expression tree into a SortedMultiVec
pub fn from_tree(tree: &expression::Tree) -> Result<Self, Error>
where
Pk: FromStr,
<Pk as FromStr>::Err: ToString,
{
if tree.args.is_empty() {
return Err(errstr("no arguments given for sortedmulti"));
}
let k = expression::parse_num(tree.args[0].name)?;
if k > (tree.args.len() - 1) as u32 {
return Err(errstr(
"higher threshold than there were keys in sortedmulti",
));
}
let pks: Result<Vec<Pk>, _> = tree.args[1..]
.iter()
.map(|sub| expression::terminal(sub, Pk::from_str))
.collect();
pks.map(|pks| SortedMultiVec::new(k as usize, pks))?
}
/// This will panic if fpk returns an uncompressed key when
/// converting to a Segwit descriptor. To prevent this panic, ensure
/// fpk returns an error in this case instead.
pub fn translate_pk<T, Q, FuncError>(
&self,
t: &mut T,
) -> Result<SortedMultiVec<Q, Ctx>, FuncError>
where
T: Translator<Pk, Q, FuncError>,
Q: MiniscriptKey,
{
let pks: Result<Vec<Q>, _> = self.pks.iter().map(|pk| t.pk(pk)).collect();
Ok(SortedMultiVec {
k: self.k,
pks: pks?,
phantom: PhantomData,
})
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> ForEachKey<Pk> for SortedMultiVec<Pk, Ctx> {
fn for_each_key<'a, F: FnMut(&'a Pk) -> bool>(&'a self, mut pred: F) -> bool
where
Pk: 'a,
{
self.pks.iter().all(|key| pred(key))
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> SortedMultiVec<Pk, Ctx> {
/// utility function to sanity a sorted multi vec
pub fn sanity_check(&self) -> Result<(), Error> {
let ms: Miniscript<Pk, Ctx> =
Miniscript::from_ast(Terminal::Multi(self.k, self.pks.clone()))
.expect("Must typecheck");
// '?' for doing From conversion
ms.sanity_check()?;
Ok(())
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> SortedMultiVec<Pk, Ctx> {
/// Create Terminal::Multi containing sorted pubkeys
pub fn sorted_node(&self) -> Terminal<Pk, Ctx>
where
Pk: ToPublicKey,
{
let mut pks = self.pks.clone();
// Sort pubkeys lexicographically according to BIP 67
pks.sort_by(|a, b| {
a.to_public_key()
.inner
.serialize()
.partial_cmp(&b.to_public_key().inner.serialize())
.unwrap()
});
Terminal::Multi(self.k, pks)
}
/// Encode as a Bitcoin script
pub fn encode(&self) -> script::Script
where
Pk: ToPublicKey,
{
self.sorted_node()
.encode(script::Builder::new())
.into_script()
}
/// Attempt to produce a satisfying witness for the
/// witness script represented by the parse tree
pub fn satisfy<S>(&self, satisfier: S) -> Result<Vec<Vec<u8>>, Error>
where
Pk: ToPublicKey,
S: Satisfier<Pk>,
{
let ms = Miniscript::from_ast(self.sorted_node()).expect("Multi node typecheck");
ms.satisfy(satisfier)
}
/// Size, in bytes of the script-pubkey. If this Miniscript is used outside
/// of segwit (e.g. in a bare or P2SH descriptor), this quantity should be
/// multiplied by 4 to compute the weight.
///
/// In general, it is not recommended to use this function directly, but
/// to instead call the corresponding function on a `Descriptor`, which
/// will handle the segwit/non-segwit technicalities for you.
pub fn script_size(&self) -> usize {
script_num_size(self.k)
+ 1
+ script_num_size(self.pks.len())
+ self.pks.iter().map(|pk| Ctx::pk_len(pk)).sum::<usize>()
}
/// Maximum number of witness elements used to satisfy the Miniscript
/// fragment, including the witness script itself. Used to estimate
/// the weight of the `VarInt` that specifies this number in a serialized
/// transaction.
///
/// This function may panic on malformed `Miniscript` objects which do
/// not correspond to semantically sane Scripts. (Such scripts should be
/// rejected at parse time. Any exceptions are bugs.)
pub fn max_satisfaction_witness_elements(&self) -> usize {
2 + self.k
}
/// Maximum size, in bytes, of a satisfying witness.
/// In general, it is not recommended to use this function directly, but
/// to instead call the corresponding function on a `Descriptor`, which
/// will handle the segwit/non-segwit technicalities for you.
///
/// All signatures are assumed to be 73 bytes in size, including the
/// length prefix (segwit) or push opcode (pre-segwit) and sighash
/// postfix.
pub fn max_satisfaction_size(&self) -> usize {
1 + 73 * self.k
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> policy::Liftable<Pk> for SortedMultiVec<Pk, Ctx> {
fn lift(&self) -> Result<policy::semantic::Policy<Pk>, Error> {
let ret = policy::semantic::Policy::Threshold(
self.k,
self.pks
.iter()
.map(|k| policy::semantic::Policy::Key(k.clone()))
.collect(),
);
Ok(ret)
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> fmt::Debug for SortedMultiVec<Pk, Ctx> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(self, f)
}
}
impl<Pk: MiniscriptKey, Ctx: ScriptContext> fmt::Display for SortedMultiVec<Pk, Ctx> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "sortedmulti({}", self.k)?;
for k in &self.pks {
write!(f, ",{}", k)?;
}
f.write_str(")")
}
}
#[cfg(test)]
mod tests {
use bitcoin::secp256k1::PublicKey;
use miniscript::context::Legacy;
use super::*;
#[test]
fn too_many_pubkeys() {
// Arbitrary pubic key.
let pk = PublicKey::from_str(
"02e6642fd69bd211f93f7f1f36ca51a26a5290eb2dd1b0d8279a87bb0d480c8443",
)
.unwrap();
let over = 1 + MAX_PUBKEYS_PER_MULTISIG;
let mut pks = Vec::new();
for _ in 0..over {
pks.push(pk.clone());
}
let res: Result<SortedMultiVec<PublicKey, Legacy>, Error> = SortedMultiVec::new(0, pks);
let error = res.err().expect("constructor should err");
match error {
Error::BadDescriptor(_) => {} // ok
other => panic!("unexpected error: {:?}", other),
}
}
}