diff --git a/bitcoin/src/blockdata/witness.rs b/bitcoin/src/blockdata/witness.rs index 5c0044a5f..19bb268a2 100644 --- a/bitcoin/src/blockdata/witness.rs +++ b/bitcoin/src/blockdata/witness.rs @@ -431,6 +431,25 @@ impl Witness { } }) } + + /// Get the taproot annex following BIP341 rules. + /// + /// This does not guarantee that this represents a P2TR [`Witness`]. See + /// [Script::is_p2tr](crate::blockdata::script::Script::is_p2tr) to + /// check whether this is actually a Taproot witness. + pub fn taproot_annex(&self) -> Option<&[u8]> { + self.last().and_then(|last| { + // From BIP341: + // If there are at least two witness elements, and the first byte of + // the last element is 0x50, this last element is called annex a + // and is removed from the witness stack. + if self.len() >= 2 && last.first() == Some(&TAPROOT_ANNEX_PREFIX) { + Some(last) + } else { + None + } + }) + } } impl Index for Witness { @@ -749,6 +768,45 @@ mod test { assert_eq!(witness_annex.taproot_control_block(), Some(&control_block[..])); } + #[test] + fn test_get_annex() { + let tapscript = hex!("deadbeef"); + let control_block = hex!("02"); + // annex starting with 0x50 causes the branching logic. + let annex = hex!("50"); + + let witness_vec = vec![tapscript.clone(), control_block.clone()]; + let witness_vec_annex = vec![tapscript.clone(), control_block.clone(), annex.clone()]; + + let witness_serialized: Vec = serialize(&witness_vec); + let witness_serialized_annex: Vec = serialize(&witness_vec_annex); + + let witness = deserialize::(&witness_serialized[..]).unwrap(); + let witness_annex = deserialize::(&witness_serialized_annex[..]).unwrap(); + + // With or without annex, the tapscript should be returned. + assert_eq!(witness.taproot_annex(), None); + assert_eq!(witness_annex.taproot_annex(), Some(&annex[..])); + + // Now for keyspend + let signature = hex!("deadbeef"); + // annex starting with 0x50 causes the branching logic. + let annex = hex!("50"); + + let witness_vec = vec![signature.clone()]; + let witness_vec_annex = vec![signature.clone(), annex.clone()]; + + let witness_serialized: Vec = serialize(&witness_vec); + let witness_serialized_annex: Vec = serialize(&witness_vec_annex); + + let witness = deserialize::(&witness_serialized[..]).unwrap(); + let witness_annex = deserialize::(&witness_serialized_annex[..]).unwrap(); + + // With or without annex, the tapscript should be returned. + assert_eq!(witness.taproot_annex(), None); + assert_eq!(witness_annex.taproot_annex(), Some(&annex[..])); + } + #[test] fn test_tx() { const S: &str = "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";