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// Miniscript // Written in 2019 by // Andrew Poelstra <apoelstra@wpsoftware.net> // // 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/>. // //! Miniscript and Output Descriptors //! //! # Introduction //! ## Bitcoin Script //! //! In Bitcoin, spending policies are defined and enforced by means of a //! stack-based programming language known as Bitcoin Script. While this //! language appears to be designed with tractable analysis in mind (e.g. //! there are no looping or jumping constructions), in practice this is //! extremely difficult. As a result, typical wallet software supports only //! a small set of script templates, cannot interoperate with other similar //! software, and each wallet contains independently written ad-hoc manually //! verified code to handle these templates. Users who require more complex //! spending policies, or who want to combine signing infrastructure which //! was not explicitly designed to work together, are simply out of luck. //! //! ## Miniscript //! //! Miniscript is an alternative to Bitcoin Script which eliminates these //! problems. It can be efficiently and simply encoded as Script to ensure //! that it works on the Bitcoin blockchain, but its design is very different. //! Essentially, a Miniscript is a monotone function (tree of ANDs, ORs and //! thresholds) of signature requirements, hash preimage requirements, and //! timelocks. //! //! A [full description of Miniscript is available here](http://bitcoin.sipa.be/miniscript/miniscript.html). //! //! Miniscript also admits a more human-readable encoding. //! //! ## Output Descriptors //! //! While spending policies in Bitcoin are entirely defined by Script; there //! are multiple ways of embedding these Scripts in transaction outputs; for //! example, P2SH or Segwit v0. These different embeddings are expressed by //! *Output Descriptors*, [which are described here](https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md) //! //! # Examples //! //! ## Deriving an address from a descriptor //! //! ```rust //! extern crate bitcoin; //! extern crate miniscript; //! //! use std::str::FromStr; //! use miniscript::NullCtx; //! //! fn main() { //! let desc = miniscript::Descriptor::< //! bitcoin::PublicKey, //! >::from_str("\ //! sh(wsh(or_d(\ //! c:pk_k(020e0338c96a8870479f2396c373cc7696ba124e8635d41b0ea581112b67817261),\ //! c:pk_k(0250863ad64a87ae8a2fe83c1af1a8403cb53f53e486d8511dad8a04887e5b2352)\ //! )))\ //! ").unwrap(); //! //! // Sometimes it is necessary to have additional information to get the bitcoin::PublicKey //! // from the MiniscriptKey which can supplied by `to_pk_ctx` parameter. For example, //! // when calculating the script pubkey of a descriptor with xpubs, the secp context and //! // child information maybe required. //! //! // Derive the P2SH address //! assert_eq!( //! desc.address(bitcoin::Network::Bitcoin, NullCtx).unwrap().to_string(), //! "3CJxbQBfWAe1ZkKiGQNEYrioV73ZwvBWns" //! ); //! //! // Check whether the descriptor is safe //! // This checks whether all spend paths are accessible in bitcoin network. //! // It maybe possible that some of the spend require more than 100 elements in Wsh scripts //! // Or they contain a combination of timelock and heightlock. //! assert!(desc.sanity_check().is_ok()); //! //! // Estimate the satisfaction cost //! assert_eq!(desc.max_satisfaction_weight(NullCtx).unwrap(), 293); //! } //! ``` //! //! #![allow(bare_trait_objects)] #![cfg_attr(all(test, feature = "unstable"), feature(test))] // Coding conventions #![deny(unsafe_code)] #![deny(non_upper_case_globals)] #![deny(non_camel_case_types)] #![deny(non_snake_case)] #![deny(unused_mut)] #![deny(dead_code)] #![deny(unused_imports)] #![deny(missing_docs)] pub extern crate bitcoin; #[cfg(feature = "serde")] pub extern crate serde; #[cfg(all(test, feature = "unstable"))] extern crate test; #[macro_use] mod macros; pub mod descriptor; pub mod expression; pub mod interpreter; pub mod miniscript; pub mod policy; pub mod psbt; mod util; use std::str::FromStr; use std::{error, fmt, hash, str}; use bitcoin::blockdata::{opcodes, script}; use bitcoin::hashes::{hash160, sha256, Hash}; pub use descriptor::{Descriptor, DescriptorPublicKey, DescriptorPublicKeyCtx}; pub use interpreter::Interpreter; pub use miniscript::context::{Bare, Legacy, ScriptContext, Segwitv0}; pub use miniscript::decode::Terminal; pub use miniscript::satisfy::{BitcoinSig, Satisfier}; pub use miniscript::Miniscript; ///Public key trait which can be converted to Hash type pub trait MiniscriptKey: Clone + Eq + Ord + str::FromStr + fmt::Debug + fmt::Display + hash::Hash { /// Check if the publicKey is uncompressed. The default /// implementation returns false fn is_uncompressed(&self) -> bool { false } /// The associated Hash type with the publicKey type Hash: Clone + Eq + Ord + str::FromStr + fmt::Display + fmt::Debug + hash::Hash; /// Converts an object to PublicHash fn to_pubkeyhash(&self) -> Self::Hash; } impl MiniscriptKey for bitcoin::PublicKey { /// `is_uncompressed` returns true only for /// bitcoin::Publickey type if the underlying key is uncompressed. fn is_uncompressed(&self) -> bool { !self.compressed } type Hash = hash160::Hash; fn to_pubkeyhash(&self) -> Self::Hash { let mut engine = hash160::Hash::engine(); self.write_into(&mut engine); hash160::Hash::from_engine(engine) } } impl MiniscriptKey for String { type Hash = String; fn to_pubkeyhash(&self) -> Self::Hash { format!("{}", &self) } } /// Trait describing public key types which can be converted to bitcoin pubkeys /// The trait relies on Copy trait because in all practical usecases `ToPkCtx` /// should contain references to objects which should be cheap to `Copy`. // Why is this a generic instead of associated type? // We would like to support implementation of `ToPublicKey` for both // secp verification_only and secp_all. But as of rust 1.29(MSRV), the // feature for associated traits is unstable. pub trait ToPublicKey<ToPkCtx: Copy>: MiniscriptKey { /// Converts an object to a public key /// C represents additional context information that maybe /// required for deriving a bitcoin::PublicKey from MiniscriptKey /// You may require secp context for crypto operations /// or additional information for substituting the wildcard in /// extended pubkeys fn to_public_key(&self, to_pk_ctx: ToPkCtx) -> bitcoin::PublicKey; /// Computes the size of a public key when serialized in a script, /// including the length bytes fn serialized_len(&self, to_pk_ctx: ToPkCtx) -> usize { if self.to_public_key(to_pk_ctx).compressed { 34 } else { 66 } } /// Converts a hashed version of the public key to a `hash160` hash. /// /// This method must be consistent with `to_public_key`, in the sense /// that calling `MiniscriptKey::to_pubkeyhash` followed by this function /// should give the same result as calling `to_public_key` and hashing /// the result directly. fn hash_to_hash160(hash: &<Self as MiniscriptKey>::Hash, to_pk_ctx: ToPkCtx) -> hash160::Hash; } /// Dummy Context for impl for ToPublicKey for bitcoin::PublicKey #[derive(Debug, Clone, Copy)] pub struct NullCtx; impl ToPublicKey<NullCtx> for bitcoin::PublicKey { fn to_public_key(&self, _ctx: NullCtx) -> bitcoin::PublicKey { *self } fn hash_to_hash160(hash: &hash160::Hash, _ctx: NullCtx) -> hash160::Hash { *hash } } /// Dummy key which de/serializes to the empty string; useful sometimes for testing #[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Debug)] pub struct DummyKey; impl str::FromStr for DummyKey { type Err = &'static str; fn from_str(x: &str) -> Result<DummyKey, &'static str> { if x.is_empty() { Ok(DummyKey) } else { Err("non empty dummy key") } } } impl MiniscriptKey for DummyKey { type Hash = DummyKeyHash; fn to_pubkeyhash(&self) -> Self::Hash { DummyKeyHash } } impl hash::Hash for DummyKey { fn hash<H: hash::Hasher>(&self, state: &mut H) { "DummyKey".hash(state); } } impl fmt::Display for DummyKey { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str("") } } impl ToPublicKey<NullCtx> for DummyKey { fn to_public_key(&self, _ctx: NullCtx) -> bitcoin::PublicKey { bitcoin::PublicKey::from_str( "0250863ad64a87ae8a2fe83c1af1a8403cb53f53e486d8511dad8a04887e5b2352", ) .unwrap() } fn hash_to_hash160(_: &DummyKeyHash, _ctx: NullCtx) -> hash160::Hash { hash160::Hash::from_str("f54a5851e9372b87810a8e60cdd2e7cfd80b6e31").unwrap() } } /// Dummy keyhash which de/serializes to the empty string; useful sometimes for testing #[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Debug)] pub struct DummyKeyHash; impl str::FromStr for DummyKeyHash { type Err = &'static str; fn from_str(x: &str) -> Result<DummyKeyHash, &'static str> { if x.is_empty() { Ok(DummyKeyHash) } else { Err("non empty dummy key") } } } impl fmt::Display for DummyKeyHash { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str("") } } impl hash::Hash for DummyKeyHash { fn hash<H: hash::Hasher>(&self, state: &mut H) { "DummyKeyHash".hash(state); } } /// Miniscript #[derive(Debug)] pub enum Error { /// Opcode appeared which is not part of the script subset InvalidOpcode(opcodes::All), /// Some opcode occurred followed by `OP_VERIFY` when it had /// a `VERIFY` version that should have been used instead NonMinimalVerify(miniscript::lex::Token), /// Push was illegal in some context InvalidPush(Vec<u8>), /// rust-bitcoin script error Script(script::Error), /// A `CHECKMULTISIG` opcode was preceded by a number > 20 CmsTooManyKeys(u32), /// Encountered unprintable character in descriptor Unprintable(u8), /// expected character while parsing descriptor; didn't find one ExpectedChar(char), /// While parsing backward, hit beginning of script UnexpectedStart, /// Got something we were not expecting Unexpected(String), /// Name of a fragment contained `:` multiple times MultiColon(String), /// Name of a fragment contained `@` multiple times MultiAt(String), /// Name of a fragment contained `@` but we were not parsing an OR AtOutsideOr(String), /// Fragment was an `and_v(_, true)` which should be written as `t:` NonCanonicalTrue, /// Fragment was an `or_i(_, false)` or `or_i(false,_)` which should be written as `u:` or `l:` NonCanonicalFalse, /// Encountered a `l:0` which is syntactically equal to `u:0` except stupid LikelyFalse, /// Encountered a wrapping character that we don't recognize UnknownWrapper(char), /// Parsed a miniscript and the result was not of type T NonTopLevel(String), /// Parsed a miniscript but there were more script opcodes after it Trailing(String), /// Failed to parse a push as a public key BadPubkey(bitcoin::util::key::Error), /// Could not satisfy a script (fragment) because of a missing hash preimage MissingHash(sha256::Hash), /// Could not satisfy a script (fragment) because of a missing signature MissingSig(bitcoin::PublicKey), /// Could not satisfy, relative locktime not met RelativeLocktimeNotMet(u32), /// Could not satisfy, absolute locktime not met AbsoluteLocktimeNotMet(u32), /// General failure to satisfy CouldNotSatisfy, /// Typechecking failed TypeCheck(String), /// General error in creating descriptor BadDescriptor, /// Forward-secp related errors Secp(bitcoin::secp256k1::Error), #[cfg(feature = "compiler")] /// Compiler related errors CompilerError(policy::compiler::CompilerError), /// Errors related to policy PolicyError(policy::concrete::PolicyError), /// Errors related to lifting LiftError(policy::LiftError), /// Forward script context related errors ContextError(miniscript::context::ScriptContextError), /// Recursion depth exceeded when parsing policy/miniscript from string MaxRecursiveDepthExceeded, /// Script size too large ScriptSizeTooLarge, /// Anything but c:pk(key) (P2PK), c:pk_h(key) (P2PKH), and thresh_m(k,...) /// up to n=3 is invalid by standardness (bare) NonStandardBareScript, /// Analysis Error AnalysisError(miniscript::analyzable::AnalysisError), } #[doc(hidden)] impl<Pk, Ctx> From<miniscript::types::Error<Pk, Ctx>> for Error where Pk: MiniscriptKey, Ctx: ScriptContext, { fn from(e: miniscript::types::Error<Pk, Ctx>) -> Error { Error::TypeCheck(e.to_string()) } } #[doc(hidden)] impl From<policy::LiftError> for Error { fn from(e: policy::LiftError) -> Error { Error::LiftError(e) } } #[doc(hidden)] impl From<miniscript::context::ScriptContextError> for Error { fn from(e: miniscript::context::ScriptContextError) -> Error { Error::ContextError(e) } } #[doc(hidden)] impl From<miniscript::analyzable::AnalysisError> for Error { fn from(e: miniscript::analyzable::AnalysisError) -> Error { Error::AnalysisError(e) } } #[doc(hidden)] impl From<bitcoin::secp256k1::Error> for Error { fn from(e: bitcoin::secp256k1::Error) -> Error { Error::Secp(e) } } fn errstr(s: &str) -> Error { Error::Unexpected(s.to_owned()) } impl error::Error for Error { fn cause(&self) -> Option<&error::Error> { match *self { Error::BadPubkey(ref e) => Some(e), _ => None, } } } // https://github.com/sipa/miniscript/pull/5 for discussion on this number const MAX_RECURSION_DEPTH: u32 = 402; // https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki const MAX_SCRIPT_SIZE: u32 = 10000; impl fmt::Display for Error { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { Error::InvalidOpcode(op) => write!(f, "invalid opcode {}", op), Error::NonMinimalVerify(tok) => write!(f, "{} VERIFY", tok), Error::InvalidPush(ref push) => write!(f, "invalid push {:?}", push), // TODO hexify this Error::Script(ref e) => fmt::Display::fmt(e, f), Error::CmsTooManyKeys(n) => write!(f, "checkmultisig with {} keys", n), Error::Unprintable(x) => write!(f, "unprintable character 0x{:02x}", x), Error::ExpectedChar(c) => write!(f, "expected {}", c), Error::UnexpectedStart => f.write_str("unexpected start of script"), Error::Unexpected(ref s) => write!(f, "unexpected «{}»", s), Error::MultiColon(ref s) => write!(f, "«{}» has multiple instances of «:»", s), Error::MultiAt(ref s) => write!(f, "«{}» has multiple instances of «@»", s), Error::AtOutsideOr(ref s) => write!(f, "«{}» contains «@» in non-or() context", s), Error::NonCanonicalTrue => f.write_str("Use «t:X» rather than «and_v(X,true())»"), Error::NonCanonicalFalse => { f.write_str("Use «u:X» «l:X» rather than «or_i(X,false)» «or_i(false,X)»") } Error::LikelyFalse => write!(f, "0 is not very likely (use «u:0»)"), Error::UnknownWrapper(ch) => write!(f, "unknown wrapper «{}:»", ch), Error::NonTopLevel(ref s) => write!(f, "non-T miniscript: {}", s), Error::Trailing(ref s) => write!(f, "trailing tokens: {}", s), Error::MissingHash(ref h) => write!(f, "missing preimage of hash {}", h), Error::MissingSig(ref pk) => write!(f, "missing signature for key {:?}", pk), Error::RelativeLocktimeNotMet(n) => { write!(f, "required relative locktime CSV of {} blocks, not met", n) } Error::AbsoluteLocktimeNotMet(n) => write!( f, "required absolute locktime CLTV of {} blocks, not met", n ), Error::CouldNotSatisfy => f.write_str("could not satisfy"), Error::BadPubkey(ref e) => fmt::Display::fmt(e, f), Error::TypeCheck(ref e) => write!(f, "typecheck: {}", e), Error::BadDescriptor => f.write_str("could not create a descriptor"), Error::Secp(ref e) => fmt::Display::fmt(e, f), Error::ContextError(ref e) => fmt::Display::fmt(e, f), #[cfg(feature = "compiler")] Error::CompilerError(ref e) => fmt::Display::fmt(e, f), Error::PolicyError(ref e) => fmt::Display::fmt(e, f), Error::LiftError(ref e) => fmt::Display::fmt(e, f), Error::MaxRecursiveDepthExceeded => write!( f, "Recursive depth over {} not permitted", MAX_RECURSION_DEPTH ), Error::ScriptSizeTooLarge => write!( f, "Standardness rules imply bitcoin than {} bytes", MAX_SCRIPT_SIZE ), Error::NonStandardBareScript => write!( f, "Anything but c:pk(key) (P2PK), c:pk_h(key) (P2PKH), and thresh_m(k,...) \ up to n=3 is invalid by standardness (bare). " ), Error::AnalysisError(ref e) => e.fmt(f), } } } #[doc(hidden)] #[cfg(feature = "compiler")] impl From<policy::compiler::CompilerError> for Error { fn from(e: policy::compiler::CompilerError) -> Error { Error::CompilerError(e) } } #[doc(hidden)] impl From<policy::concrete::PolicyError> for Error { fn from(e: policy::concrete::PolicyError) -> Error { Error::PolicyError(e) } } /// The size of an encoding of a number in Script pub fn script_num_size(n: usize) -> usize { match n { n if n <= 0x10 => 1, // OP_n n if n < 0x80 => 2, // OP_PUSH1 <n> n if n < 0x8000 => 3, // OP_PUSH2 <n> n if n < 0x800000 => 4, // OP_PUSH3 <n> n if n < 0x80000000 => 5, // OP_PUSH4 <n> _ => 6, // OP_PUSH5 <n> } } /// Returns the size of the smallest push opcode used to push a given number of bytes onto the stack /// /// For sizes ≤ 75, there are dedicated single-byte opcodes, so the push size is one. Otherwise, /// if the size can fit into 1, 2 or 4 bytes, we use the `PUSHDATA{1,2,4}` opcode respectively, /// followed by the actual size encoded in that many bytes. fn push_opcode_size(script_size: usize) -> usize { if script_size < 76 { 1 } else if script_size < 0x100 { 2 } else if script_size < 0x10000 { 3 } else { 5 } } /// Helper function used by tests #[cfg(test)] fn hex_script(s: &str) -> bitcoin::Script { let v: Vec<u8> = bitcoin::hashes::hex::FromHex::from_hex(s).unwrap(); bitcoin::Script::from(v) }