1 // This file is Copyright its original authors, visible in version control
4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7 // You may not use this file except in accordance with one or both of these
10 //! Tagged hashes for use in signature calculation and verification.
12 use bitcoin::hashes::{Hash, HashEngine, sha256};
13 use bitcoin::secp256k1::{Message, PublicKey, Secp256k1, self};
14 use bitcoin::secp256k1::schnorr::Signature;
16 use crate::util::ser::{BigSize, Readable};
18 use crate::prelude::*;
20 /// Valid type range for signature TLV records.
21 const SIGNATURE_TYPES: core::ops::RangeInclusive<u64> = 240..=1000;
23 tlv_stream!(SignatureTlvStream, SignatureTlvStreamRef, SIGNATURE_TYPES, {
24 (240, signature: Signature),
27 /// Error when signing messages.
28 #[derive(Debug, PartialEq)]
29 pub enum SignError<E> {
30 /// User-defined error when signing the message.
32 /// Error when verifying the produced signature using the given pubkey.
33 Verification(secp256k1::Error),
36 /// Signs a message digest consisting of a tagged hash of the given bytes, checking if it can be
37 /// verified with the supplied pubkey.
39 /// Panics if `bytes` is not a well-formed TLV stream containing at least one TLV record.
40 pub(super) fn sign_message<F, E>(
41 sign: F, tag: &str, bytes: &[u8], pubkey: PublicKey,
42 ) -> Result<Signature, SignError<E>>
44 F: FnOnce(&Message) -> Result<Signature, E>
46 let digest = message_digest(tag, bytes);
47 let signature = sign(&digest).map_err(|e| SignError::Signing(e))?;
49 let pubkey = pubkey.into();
50 let secp_ctx = Secp256k1::verification_only();
51 secp_ctx.verify_schnorr(&signature, &digest, &pubkey).map_err(|e| SignError::Verification(e))?;
56 /// Verifies the signature with a pubkey over the given bytes using a tagged hash as the message
59 /// Panics if `bytes` is not a well-formed TLV stream containing at least one TLV record.
60 pub(super) fn verify_signature(
61 signature: &Signature, tag: &str, bytes: &[u8], pubkey: PublicKey,
62 ) -> Result<(), secp256k1::Error> {
63 let digest = message_digest(tag, bytes);
64 let pubkey = pubkey.into();
65 let secp_ctx = Secp256k1::verification_only();
66 secp_ctx.verify_schnorr(signature, &digest, &pubkey)
69 fn message_digest(tag: &str, bytes: &[u8]) -> Message {
70 let tag = sha256::Hash::hash(tag.as_bytes());
71 let merkle_root = root_hash(bytes);
72 Message::from_slice(&tagged_hash(tag, merkle_root)).unwrap()
75 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
76 /// containing at least one TLV record.
77 fn root_hash(data: &[u8]) -> sha256::Hash {
78 let mut tlv_stream = TlvStream::new(&data[..]).peekable();
79 let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
80 let mut engine = sha256::Hash::engine();
81 engine.input("LnNonce".as_bytes());
82 engine.input(tlv_stream.peek().unwrap().record_bytes);
85 let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
86 let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
88 let mut leaves = Vec::new();
89 for record in tlv_stream {
90 if !SIGNATURE_TYPES.contains(&record.r#type) {
91 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record));
92 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
96 // Calculate the merkle root hash in place.
97 let num_leaves = leaves.len();
99 let step = 2 << level;
100 let offset = step / 2;
101 if offset >= num_leaves {
105 let left_branches = (0..num_leaves).step_by(step);
106 let right_branches = (offset..num_leaves).step_by(step);
107 for (i, j) in left_branches.zip(right_branches) {
108 leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
112 *leaves.first().unwrap()
115 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
116 let engine = tagged_hash_engine(tag);
117 tagged_hash_from_engine(engine, msg)
120 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
121 let mut engine = sha256::Hash::engine();
122 engine.input(tag.as_ref());
123 engine.input(tag.as_ref());
127 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
128 engine.input(msg.as_ref());
129 sha256::Hash::from_engine(engine)
132 fn tagged_branch_hash_from_engine(
133 mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
136 engine.input(leaf1.as_ref());
137 engine.input(leaf2.as_ref());
139 engine.input(leaf2.as_ref());
140 engine.input(leaf1.as_ref());
142 sha256::Hash::from_engine(engine)
145 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
146 /// well-formed TLV stream.
147 struct TlvStream<'a> {
148 data: io::Cursor<&'a [u8]>,
151 impl<'a> TlvStream<'a> {
152 fn new(data: &'a [u8]) -> Self {
154 data: io::Cursor::new(data),
159 /// A slice into a [`TlvStream`] for a record.
160 struct TlvRecord<'a> {
162 type_bytes: &'a [u8],
163 // The entire TLV record.
164 record_bytes: &'a [u8],
167 impl AsRef<[u8]> for TlvRecord<'_> {
168 fn as_ref(&self) -> &[u8] { &self.record_bytes }
171 impl<'a> Iterator for TlvStream<'a> {
172 type Item = TlvRecord<'a>;
174 fn next(&mut self) -> Option<Self::Item> {
175 if self.data.position() < self.data.get_ref().len() as u64 {
176 let start = self.data.position();
178 let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
179 let offset = self.data.position();
180 let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
182 let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
183 let offset = self.data.position();
184 let end = offset + length;
186 let _value = &self.data.get_ref()[offset as usize..end as usize];
187 let record_bytes = &self.data.get_ref()[start as usize..end as usize];
189 self.data.set_position(end);
191 Some(TlvRecord { r#type, type_bytes, record_bytes })
200 use bitcoin::hashes::{Hash, sha256};
203 fn calculates_merkle_root_hash() {
204 // BOLT 12 test vectors
205 macro_rules! tlv1 { () => { "010203e8" } }
206 macro_rules! tlv2 { () => { "02080000010000020003" } }
207 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
209 super::root_hash(&hex::decode(tlv1!()).unwrap()),
210 sha256::Hash::from_slice(&hex::decode("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
213 super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!())).unwrap()),
214 sha256::Hash::from_slice(&hex::decode("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
217 super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
218 sha256::Hash::from_slice(&hex::decode("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),