git.bitcoin.ninja 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 core::convert::AsRef;
  16 use crate::io;
  17 use crate::util::ser::{BigSize, Readable, Writeable, Writer};
  18
  19 use crate::prelude::*;
  20
  21 /// Valid type range for signature TLV records.
  22 const SIGNATURE_TYPES: core::ops::RangeInclusive<u64> = 240..=1000;
  23
  24 tlv_stream!(SignatureTlvStream, SignatureTlvStreamRef, SIGNATURE_TYPES, {
  25         (240, signature: Signature),
  26 });
  27
  28 /// A hash for use in a specific context by tweaking with a context-dependent tag as per [BIP 340]
  29 /// and computed over the merkle root of a TLV stream to sign as defined in [BOLT 12].
  30 ///
  31 /// [BIP 340]: https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki
  32 /// [BOLT 12]: https://github.com/rustyrussell/lightning-rfc/blob/guilt/offers/12-offer-encoding.md#signature-calculation
  33 #[derive(Clone, Debug, PartialEq)]
  34 pub struct TaggedHash(Message);
  35
  36 impl TaggedHash {
  37         /// Creates a tagged hash with the given parameters.
  38         ///
  39         /// Panics if `tlv_stream` is not a well-formed TLV stream containing at least one TLV record.
  40         pub(super) fn new(tag: &str, tlv_stream: &[u8]) -> Self {
  41                 let tag = sha256::Hash::hash(tag.as_bytes());
  42                 let merkle_root = root_hash(tlv_stream);
  43                 Self(Message::from_slice(&tagged_hash(tag, merkle_root)).unwrap())
  44         }
  45
  46         /// Returns the digest to sign.
  47         pub fn as_digest(&self) -> &Message {
  48                 &self.0
  49         }
  50 }
  51
  52 impl AsRef<TaggedHash> for TaggedHash {
  53         fn as_ref(&self) -> &TaggedHash {
  54                 self
  55         }
  56 }
  57
  58 /// Error when signing messages.
  59 #[derive(Debug, PartialEq)]
  60 pub enum SignError<E> {
  61         /// User-defined error when signing the message.
  62         Signing(E),
  63         /// Error when verifying the produced signature using the given pubkey.
  64         Verification(secp256k1::Error),
  65 }
  66
  67 /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream, checking if it
  68 /// can be verified with the supplied `pubkey`.
  69 ///
  70 /// Since `message` is any type that implements [`AsRef<TaggedHash>`], `sign` may be a closure that
  71 /// takes a message such as [`Bolt12Invoice`] or [`InvoiceRequest`]. This allows further message
  72 /// verification before signing its [`TaggedHash`].
  73 ///
  74 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
  75 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
  76 pub(super) fn sign_message<F, E, T>(
  77         sign: F, message: &T, pubkey: PublicKey,
  78 ) -> Result<Signature, SignError<E>>
  79 where
  80         F: FnOnce(&T) -> Result<Signature, E>,
  81         T: AsRef<TaggedHash>,
  82 {
  83         let signature = sign(message).map_err(|e| SignError::Signing(e))?;
  84
  85         let digest = message.as_ref().as_digest();
  86         let pubkey = pubkey.into();
  87         let secp_ctx = Secp256k1::verification_only();
  88         secp_ctx.verify_schnorr(&signature, digest, &pubkey).map_err(|e| SignError::Verification(e))?;
  89
  90         Ok(signature)
  91 }
  92
  93 /// Verifies the signature with a pubkey over the given message using a tagged hash as the message
  94 /// digest.
  95 pub(super) fn verify_signature(
  96         signature: &Signature, message: &TaggedHash, pubkey: PublicKey,
  97 ) -> Result<(), secp256k1::Error> {
  98         let digest = message.as_digest();
  99         let pubkey = pubkey.into();
 100         let secp_ctx = Secp256k1::verification_only();
 101         secp_ctx.verify_schnorr(signature, digest, &pubkey)
 102 }
 103
 104 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
 105 /// containing at least one TLV record.
 106 fn root_hash(data: &[u8]) -> sha256::Hash {
 107         let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
 108                 let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
 109                 let mut engine = sha256::Hash::engine();
 110                 engine.input("LnNonce".as_bytes());
 111                 engine.input(first_tlv_record.record_bytes);
 112                 engine
 113         }));
 114         let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
 115         let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
 116
 117         let mut leaves = Vec::new();
 118         let tlv_stream = TlvStream::new(&data[..]);
 119         for record in tlv_stream.skip_signatures() {
 120                 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
 121                 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
 122         }
 123
 124         // Calculate the merkle root hash in place.
 125         let num_leaves = leaves.len();
 126         for level in 0.. {
 127                 let step = 2 << level;
 128                 let offset = step / 2;
 129                 if offset >= num_leaves {
 130                         break;
 131                 }
 132
 133                 let left_branches = (0..num_leaves).step_by(step);
 134                 let right_branches = (offset..num_leaves).step_by(step);
 135                 for (i, j) in left_branches.zip(right_branches) {
 136                         leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
 137                 }
 138         }
 139
 140         *leaves.first().unwrap()
 141 }
 142
 143 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
 144         let engine = tagged_hash_engine(tag);
 145         tagged_hash_from_engine(engine, msg)
 146 }
 147
 148 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
 149         let mut engine = sha256::Hash::engine();
 150         engine.input(tag.as_ref());
 151         engine.input(tag.as_ref());
 152         engine
 153 }
 154
 155 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
 156         engine.input(msg.as_ref());
 157         sha256::Hash::from_engine(engine)
 158 }
 159
 160 fn tagged_branch_hash_from_engine(
 161         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
 162 ) -> sha256::Hash {
 163         if leaf1 < leaf2 {
 164                 engine.input(leaf1.as_ref());
 165                 engine.input(leaf2.as_ref());
 166         } else {
 167                 engine.input(leaf2.as_ref());
 168                 engine.input(leaf1.as_ref());
 169         };
 170         sha256::Hash::from_engine(engine)
 171 }
 172
 173 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
 174 /// well-formed TLV stream.
 175 #[derive(Clone)]
 176 pub(super) struct TlvStream<'a> {
 177         data: io::Cursor<&'a [u8]>,
 178 }
 179
 180 impl<'a> TlvStream<'a> {
 181         pub fn new(data: &'a [u8]) -> Self {
 182                 Self {
 183                         data: io::Cursor::new(data),
 184                 }
 185         }
 186
 187         pub fn range<T>(self, types: T) -> impl core::iter::Iterator<Item = TlvRecord<'a>>
 188         where
 189                 T: core::ops::RangeBounds<u64> + Clone,
 190         {
 191                 let take_range = types.clone();
 192                 self.skip_while(move |record| !types.contains(&record.r#type))
 193                         .take_while(move |record| take_range.contains(&record.r#type))
 194         }
 195
 196         fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
 197                 self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
 198         }
 199 }
 200
 201 /// A slice into a [`TlvStream`] for a record.
 202 pub(super) struct TlvRecord<'a> {
 203         pub(super) r#type: u64,
 204         type_bytes: &'a [u8],
 205         // The entire TLV record.
 206         pub(super) record_bytes: &'a [u8],
 207 }
 208
 209 impl<'a> Iterator for TlvStream<'a> {
 210         type Item = TlvRecord<'a>;
 211
 212         fn next(&mut self) -> Option<Self::Item> {
 213                 if self.data.position() < self.data.get_ref().len() as u64 {
 214                         let start = self.data.position();
 215
 216                         let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 217                         let offset = self.data.position();
 218                         let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
 219
 220                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 221                         let offset = self.data.position();
 222                         let end = offset + length;
 223
 224                         let _value = &self.data.get_ref()[offset as usize..end as usize];
 225                         let record_bytes = &self.data.get_ref()[start as usize..end as usize];
 226
 227                         self.data.set_position(end);
 228
 229                         Some(TlvRecord { r#type, type_bytes, record_bytes })
 230                 } else {
 231                         None
 232                 }
 233         }
 234 }
 235
 236 /// Encoding for a pre-serialized TLV stream that excludes any signature TLV records.
 237 ///
 238 /// Panics if the wrapped bytes are not a well-formed TLV stream.
 239 pub(super) struct WithoutSignatures<'a>(pub &'a [u8]);
 240
 241 impl<'a> Writeable for WithoutSignatures<'a> {
 242         #[inline]
 243         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 244                 let tlv_stream = TlvStream::new(self.0);
 245                 for record in tlv_stream.skip_signatures() {
 246                         writer.write_all(record.record_bytes)?;
 247                 }
 248                 Ok(())
 249         }
 250 }
 251
 252 #[cfg(test)]
 253 mod tests {
 254         use super::{SIGNATURE_TYPES, TlvStream, WithoutSignatures};
 255
 256         use bitcoin::hashes::{Hash, sha256};
 257         use bitcoin::secp256k1::{KeyPair, Secp256k1, SecretKey};
 258         use bitcoin::secp256k1::schnorr::Signature;
 259         use core::convert::Infallible;
 260         use crate::offers::offer::{Amount, OfferBuilder};
 261         use crate::offers::invoice_request::InvoiceRequest;
 262         use crate::offers::parse::Bech32Encode;
 263         use crate::util::ser::Writeable;
 264
 265         #[test]
 266         fn calculates_merkle_root_hash() {
 267                 // BOLT 12 test vectors
 268                 macro_rules! tlv1 { () => { "010203e8" } }
 269                 macro_rules! tlv2 { () => { "02080000010000020003" } }
 270                 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
 271                 assert_eq!(
 272                         super::root_hash(&hex::decode(tlv1!()).unwrap()),
 273                         sha256::Hash::from_slice(&hex::decode("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
 274                 );
 275                 assert_eq!(
 276                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!())).unwrap()),
 277                         sha256::Hash::from_slice(&hex::decode("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
 278                 );
 279                 assert_eq!(
 280                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
 281                         sha256::Hash::from_slice(&hex::decode("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
 282                 );
 283         }
 284
 285         #[test]
 286         fn calculates_merkle_root_hash_from_invoice_request() {
 287                 let secp_ctx = Secp256k1::new();
 288                 let recipient_pubkey = {
 289                         let secret_key = SecretKey::from_slice(&hex::decode("4141414141414141414141414141414141414141414141414141414141414141").unwrap()).unwrap();
 290                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 291                 };
 292                 let payer_keys = {
 293                         let secret_key = SecretKey::from_slice(&hex::decode("4242424242424242424242424242424242424242424242424242424242424242").unwrap()).unwrap();
 294                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 295                 };
 296
 297                 // BOLT 12 test vectors
 298                 let invoice_request = OfferBuilder::new("A Mathematical Treatise".into(), recipient_pubkey)
 299                         .amount(Amount::Currency { iso4217_code: *b"USD", amount: 100 })
 300                         .build_unchecked()
 301                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 302                         .build_unchecked()
 303                         .sign::<_, Infallible>(
 304                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 305                         )
 306                         .unwrap();
 307                 assert_eq!(
 308                         invoice_request.to_string(),
 309                         "lnr1qqyqqqqqqqqqqqqqqcp4256ypqqkgzshgysy6ct5dpjk6ct5d93kzmpq23ex2ct5d9ek293pqthvwfzadd7jejes8q9lhc4rvjxd022zv5l44g6qah82ru5rdpnpjkppqvjx204vgdzgsqpvcp4mldl3plscny0rt707gvpdh6ndydfacz43euzqhrurageg3n7kafgsek6gz3e9w52parv8gs2hlxzk95tzeswywffxlkeyhml0hh46kndmwf4m6xma3tkq2lu04qz3slje2rfthc89vss",
 310                 );
 311                 assert_eq!(
 312                         super::root_hash(&invoice_request.bytes[..]),
 313                         sha256::Hash::from_slice(&hex::decode("608407c18ad9a94d9ea2bcdbe170b6c20c462a7833a197621c916f78cf18e624").unwrap()).unwrap(),
 314                 );
 315                 assert_eq!(
 316                         invoice_request.signature(),
 317                         Signature::from_slice(&hex::decode("b8f83ea3288cfd6ea510cdb481472575141e8d8744157f98562d162cc1c472526fdb24befefbdebab4dbb726bbd1b7d8aec057f8fa805187e5950d2bbe0e5642").unwrap()).unwrap(),
 318                 );
 319         }
 320
 321         #[test]
 322         fn skips_encoding_signature_tlv_records() {
 323                 let secp_ctx = Secp256k1::new();
 324                 let recipient_pubkey = {
 325                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 326                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 327                 };
 328                 let payer_keys = {
 329                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 330                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 331                 };
 332
 333                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 334                         .amount_msats(100)
 335                         .build_unchecked()
 336                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 337                         .build_unchecked()
 338                         .sign::<_, Infallible>(
 339                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 340                         )
 341                         .unwrap();
 342
 343                 let mut bytes_without_signature = Vec::new();
 344                 WithoutSignatures(&invoice_request.bytes).write(&mut bytes_without_signature).unwrap();
 345
 346                 assert_ne!(bytes_without_signature, invoice_request.bytes);
 347                 assert_eq!(
 348                         TlvStream::new(&bytes_without_signature).count(),
 349                         TlvStream::new(&invoice_request.bytes).count() - 1,
 350                 );
 351         }
 352
 353         #[test]
 354         fn iterates_over_tlv_stream_range() {
 355                 let secp_ctx = Secp256k1::new();
 356                 let recipient_pubkey = {
 357                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 358                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 359                 };
 360                 let payer_keys = {
 361                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 362                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 363                 };
 364
 365                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 366                         .amount_msats(100)
 367                         .build_unchecked()
 368                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 369                         .build_unchecked()
 370                         .sign::<_, Infallible>(
 371                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 372                         )
 373                         .unwrap();
 374
 375                 let tlv_stream = TlvStream::new(&invoice_request.bytes).range(0..1)
 376                         .chain(TlvStream::new(&invoice_request.bytes).range(1..80))
 377                         .chain(TlvStream::new(&invoice_request.bytes).range(80..160))
 378                         .chain(TlvStream::new(&invoice_request.bytes).range(160..240))
 379                         .chain(TlvStream::new(&invoice_request.bytes).range(SIGNATURE_TYPES))
 380                         .map(|r| r.record_bytes.to_vec())
 381                         .flatten()
 382                         .collect::<Vec<u8>>();
 383
 384                 assert_eq!(tlv_stream, invoice_request.bytes);
 385         }
 386
 387         impl AsRef<[u8]> for InvoiceRequest {
 388                 fn as_ref(&self) -> &[u8] {
 389                         &self.bytes
 390                 }
 391         }
 392
 393         impl Bech32Encode for InvoiceRequest {
 394                 const BECH32_HRP: &'static str = "lnr";
 395         }
 396
 397         impl core::fmt::Display for InvoiceRequest {
 398                 fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 399                         self.fmt_bech32_str(f)
 400                 }
 401         }
 402 }