util: add `bip143` module to create BIP143 signature hashes

Cargo.toml

@@ -1,7 +1,7 @@
 
 [package]
 name = "bitcoin"
-version = "0.10.6"
+version = "0.10.7"
 authors = ["Andrew Poelstra <apoelstra@wpsoftware.net>"]
 license = "CC0-1.0"
 homepage = "https://github.com/apoelstra/rust-bitcoin/"

src/blockdata/script.rs

@@ -619,8 +619,6 @@ mod test {
         assert!(read_scriptint(&build_scriptint(-(1 << 31))).is_err());
     }
 
-    macro_rules! hex_script (($s:expr) => (Script::from($s.from_hex().unwrap())));
-
     #[test]
     fn provably_unspendable_test() {
         // p2pk

src/internal_macros.rs

@@ -285,3 +285,9 @@ macro_rules! display_from_debug {
     }
 }
 
+#[cfg(test)]
+macro_rules! hex_script (($s:expr) => (Script::from($s.from_hex().unwrap())));
+
+#[cfg(test)]
+macro_rules! hex_hash (($s:expr) => (Sha256dHash::from(&$s.from_hex().unwrap()[..])));
+

src/util/bip143.rs

@@ -0,0 +1,149 @@
+// Rust Bitcoin Library
+// Written in 2018 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/>.
+//
+
+//! # BIP143 Implementation
+//!
+//! Implementation of BIP143 Segwit-style signatures. Should be sufficient
+//! to create signatures for Segwit transactions (which should be pushed into
+//! the appropriate place in the `Transaction::witness` array) or bcash
+//! signatures, which are placed in the scriptSig.
+//!
+
+use blockdata::script::Script;
+use blockdata::transaction::Transaction;
+use network::encodable::ConsensusEncodable;
+use util::hash::{Sha256dHash, Sha256dEncoder};
+
+/// Parts of a sighash which are common across inputs or signatures, and which are
+/// sufficient (in conjunction with a private key) to sign the transaction
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct SighashComponents {
+    /// Hash of all the previous outputs
+    pub hash_prevouts: Sha256dHash,
+    /// Hash of all the input sequence nos
+    pub hash_sequence: Sha256dHash,
+    /// Hash of all the outputs in this transaction
+    pub hash_outputs: Sha256dHash,
+}
+
+impl SighashComponents {
+    /// Compute the sighash components from an unsigned transaction and auxiliary
+    /// information about its inputs
+    pub fn new(tx: &Transaction) -> SighashComponents {
+        let hash_prevouts = {
+            let mut enc = Sha256dEncoder::new();
+            for txin in &tx.input {
+                txin.prev_hash.consensus_encode(&mut enc).unwrap();
+                txin.prev_index.consensus_encode(&mut enc).unwrap();
+            }
+            enc.into_hash()
+        };
+
+        let hash_sequence = {
+            let mut enc = Sha256dEncoder::new();
+            for txin in &tx.input {
+                txin.sequence.consensus_encode(&mut enc).unwrap();
+            }
+            enc.into_hash()
+        };
+
+        let hash_outputs = {
+            let mut enc = Sha256dEncoder::new();
+            for txout in &tx.output {
+                txout.consensus_encode(&mut enc).unwrap();
+            }
+            enc.into_hash()
+        };
+
+        SighashComponents {
+            hash_prevouts: hash_prevouts,
+            hash_sequence: hash_sequence,
+            hash_outputs: hash_outputs,
+        }
+    }
+
+    /// Compute the BIP143 sighash for a `SIGHASH_ALL` signature for the given
+    /// input index
+    pub fn sighash_all(&self, tx: &Transaction, index: usize, witness_script: &Script, value: u64) -> Sha256dHash {
+        let mut enc = Sha256dEncoder::new();
+        tx.version.consensus_encode(&mut enc).unwrap();
+        self.hash_prevouts.consensus_encode(&mut enc).unwrap();
+        self.hash_sequence.consensus_encode(&mut enc).unwrap();
+        tx.input[index]
+            .prev_hash
+            .consensus_encode(&mut enc)
+            .unwrap();
+        tx.input[index]
+            .prev_index
+            .consensus_encode(&mut enc)
+            .unwrap();
+        witness_script.consensus_encode(&mut enc).unwrap();
+        value.consensus_encode(&mut enc).unwrap();
+        tx.input[index].sequence.consensus_encode(&mut enc).unwrap();
+        self.hash_outputs.consensus_encode(&mut enc).unwrap();
+        tx.lock_time.consensus_encode(&mut enc).unwrap();
+        1u32.consensus_encode(&mut enc).unwrap(); // hashtype
+        enc.into_hash()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use serialize::hex::FromHex;
+
+    use network::serialize::deserialize;
+    use util::misc::hex_bytes;
+
+    use super::*;
+
+    #[test]
+    fn bip143_sig() {
+        let tx = deserialize::<Transaction>(
+            &hex_bytes(
+            "010000000136641869ca081e70f394c6948e8af409e18b619df2ed74aa106c1ca29787b96e0100000000\
+             ffffffff0200e9a435000000001976a914389ffce9cd9ae88dcc0631e88a821ffdbe9bfe2688acc0832f\
+             05000000001976a9147480a33f950689af511e6e84c138dbbd3c3ee41588ac00000000").unwrap()[..],
+        ).unwrap();
+
+        let witness_script = hex_script!(
+            "56210307b8ae49ac90a048e9b53357a2354b3334e9c8bee813ecb98e99a7e07e8c3ba32103b28f0c28\
+             bfab54554ae8c658ac5c3e0ce6e79ad336331f78c428dd43eea8449b21034b8113d703413d57761b8b\
+             9781957b8c0ac1dfe69f492580ca4195f50376ba4a21033400f6afecb833092a9a21cfdf1ed1376e58\
+             c5d1f47de74683123987e967a8f42103a6d48b1131e94ba04d9737d61acdaa1322008af9602b3b1486\
+             2c07a1789aac162102d8b661b0b3302ee2f162b09e07a55ad5dfbe673a9f01d9f0c19617681024306b\
+             56ae"
+        );
+        let value = 987654321;
+
+        let comp = SighashComponents::new(&tx);
+        assert_eq!(
+            comp,
+            SighashComponents {
+                hash_prevouts: hex_hash!(
+                    "74afdc312af5183c4198a40ca3c1a275b485496dd3929bca388c4b5e31f7aaa0"
+                ),
+                hash_sequence: hex_hash!(
+                    "3bb13029ce7b1f559ef5e747fcac439f1455a2ec7c5f09b72290795e70665044"
+                ),
+                hash_outputs: hex_hash!(
+                    "bc4d309071414bed932f98832b27b4d76dad7e6c1346f487a8fdbb8eb90307cc"
+                ),
+            }
+        );
+
+        assert_eq!(
+            comp.sighash_all(&tx, 0, &witness_script, value),
+            hex_hash!("185c0be5263dce5b4bb50a047973c1b6272bfbd0103a89444597dc40b248ee7c")
+        );
+    }
+}

src/util/mod.rs

@@ -19,6 +19,7 @@
 pub mod address;
 pub mod base58;
 pub mod bip32;
+pub mod bip143;
 pub mod contracthash;
 pub mod decimal;
 pub mod hash;