_ Git - rust-lightning/blob - lightning/src/offers/merkle.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   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
   8 // licenses.
   9
  10 //! Tagged hashes for use in signature calculation and verification.
  11
  12 use bitcoin::hashes::{Hash, HashEngine, sha256};
  13 use bitcoin::secp256k1::{Message, PublicKey, Secp256k1, self};
  14 use bitcoin::secp256k1::schnorr::Signature;
  15 use crate::io;
  16 use crate::util::ser::{BigSize, Readable};
  17
  18 use crate::prelude::*;
  19
  20 /// Valid type range for signature TLV records.
  21 const SIGNATURE_TYPES: core::ops::RangeInclusive<u64> = 240..=1000;
  22
  23 tlv_stream!(SignatureTlvStream, SignatureTlvStreamRef, SIGNATURE_TYPES, {
  24         (240, signature: Signature),
  25 });
  26
  27 /// Error when signing messages.
  28 #[derive(Debug)]
  29 pub enum SignError<E> {
  30         /// User-defined error when signing the message.
  31         Signing(E),
  32         /// Error when verifying the produced signature using the given pubkey.
  33         Verification(secp256k1::Error),
  34 }
  35
  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.
  38 ///
  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>>
  43 where
  44         F: FnOnce(&Message) -> Result<Signature, E>
  45 {
  46         let digest = message_digest(tag, bytes);
  47         let signature = sign(&digest).map_err(|e| SignError::Signing(e))?;
  48
  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))?;
  52
  53         Ok(signature)
  54 }
  55
  56 /// Verifies the signature with a pubkey over the given bytes using a tagged hash as the message
  57 /// digest.
  58 ///
  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)
  67 }
  68
  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()
  73 }
  74
  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);
  83                 engine
  84         }));
  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()));
  87
  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));
  93                 }
  94         }
  95
  96         // Calculate the merkle root hash in place.
  97         let num_leaves = leaves.len();
  98         for level in 0.. {
  99                 let step = 2 << level;
 100                 let offset = step / 2;
 101                 if offset >= num_leaves {
 102                         break;
 103                 }
 104
 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]);
 109                 }
 110         }
 111
 112         *leaves.first().unwrap()
 113 }
 114
 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)
 118 }
 119
 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());
 124         engine
 125 }
 126
 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)
 130 }
 131
 132 fn tagged_branch_hash_from_engine(
 133         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
 134 ) -> sha256::Hash {
 135         if leaf1 < leaf2 {
 136                 engine.input(leaf1.as_ref());
 137                 engine.input(leaf2.as_ref());
 138         } else {
 139                 engine.input(leaf2.as_ref());
 140                 engine.input(leaf1.as_ref());
 141         };
 142         sha256::Hash::from_engine(engine)
 143 }
 144
 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]>,
 149 }
 150
 151 impl<'a> TlvStream<'a> {
 152         fn new(data: &'a [u8]) -> Self {
 153                 Self {
 154                         data: io::Cursor::new(data),
 155                 }
 156         }
 157 }
 158
 159 /// A slice into a [`TlvStream`] for a record.
 160 struct TlvRecord<'a> {
 161         r#type: u64,
 162         type_bytes: &'a [u8],
 163         // The entire TLV record.
 164         record_bytes: &'a [u8],
 165 }
 166
 167 impl AsRef<[u8]> for TlvRecord<'_> {
 168         fn as_ref(&self) -> &[u8] { &self.record_bytes }
 169 }
 170
 171 impl<'a> Iterator for TlvStream<'a> {
 172         type Item = TlvRecord<'a>;
 173
 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();
 177
 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];
 181
 182                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 183                         let offset = self.data.position();
 184                         let end = offset + length;
 185
 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];
 188
 189                         self.data.set_position(end);
 190
 191                         Some(TlvRecord { r#type, type_bytes, record_bytes })
 192                 } else {
 193                         None
 194                 }
 195         }
 196 }
 197
 198 #[cfg(test)]
 199 mod tests {
 200         use bitcoin::hashes::{Hash, sha256};
 201
 202         #[test]
 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" } }
 208                 assert_eq!(
 209                         super::root_hash(&hex::decode(tlv1!()).unwrap()),
 210                         sha256::Hash::from_slice(&hex::decode("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
 211                 );
 212                 assert_eq!(
 213                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!())).unwrap()),
 214                         sha256::Hash::from_slice(&hex::decode("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
 215                 );
 216                 assert_eq!(
 217                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
 218                         sha256::Hash::from_slice(&hex::decode("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
 219                 );
 220         }
 221 }