_ 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 {
  35         tag: &'static str,
  36         merkle_root: sha256::Hash,
  37         digest: Message,
  38 }
  39
  40 impl TaggedHash {
  41         /// Creates a tagged hash with the given parameters.
  42         ///
  43         /// Panics if `tlv_stream` is not a well-formed TLV stream containing at least one TLV record.
  44         pub(super) fn new(tag: &'static str, tlv_stream: &[u8]) -> Self {
  45                 let tag_hash = sha256::Hash::hash(tag.as_bytes());
  46                 let merkle_root = root_hash(tlv_stream);
  47                 let digest = Message::from_slice(tagged_hash(tag_hash, merkle_root).as_byte_array()).unwrap();
  48                 Self {
  49                         tag,
  50                         merkle_root,
  51                         digest,
  52                 }
  53         }
  54
  55         /// Returns the digest to sign.
  56         pub fn as_digest(&self) -> &Message {
  57                 &self.digest
  58         }
  59
  60         /// Returns the tag used in the tagged hash.
  61         pub fn tag(&self) -> &str {
  62                 &self.tag
  63         }
  64
  65         /// Returns the merkle root used in the tagged hash.
  66         pub fn merkle_root(&self) -> sha256::Hash {
  67                 self.merkle_root
  68         }
  69 }
  70
  71 impl AsRef<TaggedHash> for TaggedHash {
  72         fn as_ref(&self) -> &TaggedHash {
  73                 self
  74         }
  75 }
  76
  77 /// Error when signing messages.
  78 #[derive(Debug, PartialEq)]
  79 pub enum SignError<E> {
  80         /// User-defined error when signing the message.
  81         Signing(E),
  82         /// Error when verifying the produced signature using the given pubkey.
  83         Verification(secp256k1::Error),
  84 }
  85
  86 /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream, checking if it
  87 /// can be verified with the supplied `pubkey`.
  88 ///
  89 /// Since `message` is any type that implements [`AsRef<TaggedHash>`], `sign` may be a closure that
  90 /// takes a message such as [`Bolt12Invoice`] or [`InvoiceRequest`]. This allows further message
  91 /// verification before signing its [`TaggedHash`].
  92 ///
  93 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
  94 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
  95 pub(super) fn sign_message<F, E, T>(
  96         sign: F, message: &T, pubkey: PublicKey,
  97 ) -> Result<Signature, SignError<E>>
  98 where
  99         F: FnOnce(&T) -> Result<Signature, E>,
 100         T: AsRef<TaggedHash>,
 101 {
 102         let signature = sign(message).map_err(|e| SignError::Signing(e))?;
 103
 104         let digest = message.as_ref().as_digest();
 105         let pubkey = pubkey.into();
 106         let secp_ctx = Secp256k1::verification_only();
 107         secp_ctx.verify_schnorr(&signature, digest, &pubkey).map_err(|e| SignError::Verification(e))?;
 108
 109         Ok(signature)
 110 }
 111
 112 /// Verifies the signature with a pubkey over the given message using a tagged hash as the message
 113 /// digest.
 114 pub(super) fn verify_signature(
 115         signature: &Signature, message: &TaggedHash, pubkey: PublicKey,
 116 ) -> Result<(), secp256k1::Error> {
 117         let digest = message.as_digest();
 118         let pubkey = pubkey.into();
 119         let secp_ctx = Secp256k1::verification_only();
 120         secp_ctx.verify_schnorr(signature, digest, &pubkey)
 121 }
 122
 123 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
 124 /// containing at least one TLV record.
 125 fn root_hash(data: &[u8]) -> sha256::Hash {
 126         let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
 127                 let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
 128                 let mut engine = sha256::Hash::engine();
 129                 engine.input("LnNonce".as_bytes());
 130                 engine.input(first_tlv_record.record_bytes);
 131                 engine
 132         }));
 133         let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
 134         let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
 135
 136         let mut leaves = Vec::new();
 137         let tlv_stream = TlvStream::new(&data[..]);
 138         for record in tlv_stream.skip_signatures() {
 139                 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
 140                 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
 141         }
 142
 143         // Calculate the merkle root hash in place.
 144         let num_leaves = leaves.len();
 145         for level in 0.. {
 146                 let step = 2 << level;
 147                 let offset = step / 2;
 148                 if offset >= num_leaves {
 149                         break;
 150                 }
 151
 152                 let left_branches = (0..num_leaves).step_by(step);
 153                 let right_branches = (offset..num_leaves).step_by(step);
 154                 for (i, j) in left_branches.zip(right_branches) {
 155                         leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
 156                 }
 157         }
 158
 159         *leaves.first().unwrap()
 160 }
 161
 162 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
 163         let engine = tagged_hash_engine(tag);
 164         tagged_hash_from_engine(engine, msg)
 165 }
 166
 167 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
 168         let mut engine = sha256::Hash::engine();
 169         engine.input(tag.as_ref());
 170         engine.input(tag.as_ref());
 171         engine
 172 }
 173
 174 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
 175         engine.input(msg.as_ref());
 176         sha256::Hash::from_engine(engine)
 177 }
 178
 179 fn tagged_branch_hash_from_engine(
 180         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
 181 ) -> sha256::Hash {
 182         if leaf1 < leaf2 {
 183                 engine.input(leaf1.as_ref());
 184                 engine.input(leaf2.as_ref());
 185         } else {
 186                 engine.input(leaf2.as_ref());
 187                 engine.input(leaf1.as_ref());
 188         };
 189         sha256::Hash::from_engine(engine)
 190 }
 191
 192 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
 193 /// well-formed TLV stream.
 194 #[derive(Clone)]
 195 pub(super) struct TlvStream<'a> {
 196         data: io::Cursor<&'a [u8]>,
 197 }
 198
 199 impl<'a> TlvStream<'a> {
 200         pub fn new(data: &'a [u8]) -> Self {
 201                 Self {
 202                         data: io::Cursor::new(data),
 203                 }
 204         }
 205
 206         pub fn range<T>(self, types: T) -> impl core::iter::Iterator<Item = TlvRecord<'a>>
 207         where
 208                 T: core::ops::RangeBounds<u64> + Clone,
 209         {
 210                 let take_range = types.clone();
 211                 self.skip_while(move |record| !types.contains(&record.r#type))
 212                         .take_while(move |record| take_range.contains(&record.r#type))
 213         }
 214
 215         fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
 216                 self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
 217         }
 218 }
 219
 220 /// A slice into a [`TlvStream`] for a record.
 221 pub(super) struct TlvRecord<'a> {
 222         pub(super) r#type: u64,
 223         type_bytes: &'a [u8],
 224         // The entire TLV record.
 225         pub(super) record_bytes: &'a [u8],
 226 }
 227
 228 impl<'a> Iterator for TlvStream<'a> {
 229         type Item = TlvRecord<'a>;
 230
 231         fn next(&mut self) -> Option<Self::Item> {
 232                 if self.data.position() < self.data.get_ref().len() as u64 {
 233                         let start = self.data.position();
 234
 235                         let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 236                         let offset = self.data.position();
 237                         let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
 238
 239                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 240                         let offset = self.data.position();
 241                         let end = offset + length;
 242
 243                         let _value = &self.data.get_ref()[offset as usize..end as usize];
 244                         let record_bytes = &self.data.get_ref()[start as usize..end as usize];
 245
 246                         self.data.set_position(end);
 247
 248                         Some(TlvRecord { r#type, type_bytes, record_bytes })
 249                 } else {
 250                         None
 251                 }
 252         }
 253 }
 254
 255 /// Encoding for a pre-serialized TLV stream that excludes any signature TLV records.
 256 ///
 257 /// Panics if the wrapped bytes are not a well-formed TLV stream.
 258 pub(super) struct WithoutSignatures<'a>(pub &'a [u8]);
 259
 260 impl<'a> Writeable for WithoutSignatures<'a> {
 261         #[inline]
 262         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 263                 let tlv_stream = TlvStream::new(self.0);
 264                 for record in tlv_stream.skip_signatures() {
 265                         writer.write_all(record.record_bytes)?;
 266                 }
 267                 Ok(())
 268         }
 269 }
 270
 271 #[cfg(test)]
 272 mod tests {
 273         use super::{SIGNATURE_TYPES, TlvStream, WithoutSignatures};
 274
 275         use bitcoin::hashes::{Hash, sha256};
 276         use bitcoin::hashes::hex::FromHex;
 277         use bitcoin::secp256k1::{KeyPair, Message, Secp256k1, SecretKey};
 278         use bitcoin::secp256k1::schnorr::Signature;
 279         use core::convert::Infallible;
 280         use crate::offers::offer::{Amount, OfferBuilder};
 281         use crate::offers::invoice_request::InvoiceRequest;
 282         use crate::offers::parse::Bech32Encode;
 283         use crate::offers::test_utils::{payer_pubkey, recipient_pubkey};
 284         use crate::util::ser::Writeable;
 285
 286         #[test]
 287         fn calculates_merkle_root_hash() {
 288                 // BOLT 12 test vectors
 289                 macro_rules! tlv1 { () => { "010203e8" } }
 290                 macro_rules! tlv2 { () => { "02080000010000020003" } }
 291                 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
 292                 assert_eq!(
 293                         super::root_hash(&<Vec<u8>>::from_hex(tlv1!()).unwrap()),
 294                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
 295                 );
 296                 assert_eq!(
 297                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!())).unwrap()),
 298                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
 299                 );
 300                 assert_eq!(
 301                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
 302                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
 303                 );
 304         }
 305
 306         #[test]
 307         fn calculates_merkle_root_hash_from_invoice_request() {
 308                 let secp_ctx = Secp256k1::new();
 309                 let recipient_pubkey = {
 310                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4141414141414141414141414141414141414141414141414141414141414141").unwrap()).unwrap();
 311                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 312                 };
 313                 let payer_keys = {
 314                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4242424242424242424242424242424242424242424242424242424242424242").unwrap()).unwrap();
 315                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 316                 };
 317
 318                 // BOLT 12 test vectors
 319                 let invoice_request = OfferBuilder::new("A Mathematical Treatise".into(), recipient_pubkey)
 320                         .amount(Amount::Currency { iso4217_code: *b"USD", amount: 100 })
 321                         .build_unchecked()
 322                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 323                         .build_unchecked()
 324                         .sign::<_, Infallible>(
 325                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 326                         )
 327                         .unwrap();
 328                 assert_eq!(
 329                         invoice_request.to_string(),
 330                         "lnr1qqyqqqqqqqqqqqqqqcp4256ypqqkgzshgysy6ct5dpjk6ct5d93kzmpq23ex2ct5d9ek293pqthvwfzadd7jejes8q9lhc4rvjxd022zv5l44g6qah82ru5rdpnpjkppqvjx204vgdzgsqpvcp4mldl3plscny0rt707gvpdh6ndydfacz43euzqhrurageg3n7kafgsek6gz3e9w52parv8gs2hlxzk95tzeswywffxlkeyhml0hh46kndmwf4m6xma3tkq2lu04qz3slje2rfthc89vss",
 331                 );
 332                 assert_eq!(
 333                         super::root_hash(&invoice_request.bytes[..]),
 334                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("608407c18ad9a94d9ea2bcdbe170b6c20c462a7833a197621c916f78cf18e624").unwrap()).unwrap(),
 335                 );
 336                 assert_eq!(
 337                         invoice_request.signature(),
 338                         Signature::from_slice(&<Vec<u8>>::from_hex("b8f83ea3288cfd6ea510cdb481472575141e8d8744157f98562d162cc1c472526fdb24befefbdebab4dbb726bbd1b7d8aec057f8fa805187e5950d2bbe0e5642").unwrap()).unwrap(),
 339                 );
 340         }
 341
 342         #[test]
 343         fn compute_tagged_hash() {
 344                 let unsigned_invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
 345                         .amount_msats(1000)
 346                         .build().unwrap()
 347                         .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
 348                         .payer_note("bar".into())
 349                         .build().unwrap();
 350
 351                 // Simply test that we can grab the tag and merkle root exposed by the accessor
 352                 // functions, then use them to succesfully compute a tagged hash.
 353                 let tagged_hash = unsigned_invoice_request.as_ref();
 354                 let expected_digest = unsigned_invoice_request.as_ref().as_digest();
 355                 let tag = sha256::Hash::hash(tagged_hash.tag().as_bytes());
 356                 let actual_digest = Message::from_slice(super::tagged_hash(tag, tagged_hash.merkle_root()).as_byte_array())
 357                         .unwrap();
 358                 assert_eq!(*expected_digest, actual_digest);
 359         }
 360
 361         #[test]
 362         fn skips_encoding_signature_tlv_records() {
 363                 let secp_ctx = Secp256k1::new();
 364                 let recipient_pubkey = {
 365                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 366                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 367                 };
 368                 let payer_keys = {
 369                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 370                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 371                 };
 372
 373                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 374                         .amount_msats(100)
 375                         .build_unchecked()
 376                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 377                         .build_unchecked()
 378                         .sign::<_, Infallible>(
 379                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 380                         )
 381                         .unwrap();
 382
 383                 let mut bytes_without_signature = Vec::new();
 384                 WithoutSignatures(&invoice_request.bytes).write(&mut bytes_without_signature).unwrap();
 385
 386                 assert_ne!(bytes_without_signature, invoice_request.bytes);
 387                 assert_eq!(
 388                         TlvStream::new(&bytes_without_signature).count(),
 389                         TlvStream::new(&invoice_request.bytes).count() - 1,
 390                 );
 391         }
 392
 393         #[test]
 394         fn iterates_over_tlv_stream_range() {
 395                 let secp_ctx = Secp256k1::new();
 396                 let recipient_pubkey = {
 397                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 398                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 399                 };
 400                 let payer_keys = {
 401                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 402                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 403                 };
 404
 405                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 406                         .amount_msats(100)
 407                         .build_unchecked()
 408                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 409                         .build_unchecked()
 410                         .sign::<_, Infallible>(
 411                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 412                         )
 413                         .unwrap();
 414
 415                 let tlv_stream = TlvStream::new(&invoice_request.bytes).range(0..1)
 416                         .chain(TlvStream::new(&invoice_request.bytes).range(1..80))
 417                         .chain(TlvStream::new(&invoice_request.bytes).range(80..160))
 418                         .chain(TlvStream::new(&invoice_request.bytes).range(160..240))
 419                         .chain(TlvStream::new(&invoice_request.bytes).range(SIGNATURE_TYPES))
 420                         .map(|r| r.record_bytes.to_vec())
 421                         .flatten()
 422                         .collect::<Vec<u8>>();
 423
 424                 assert_eq!(tlv_stream, invoice_request.bytes);
 425         }
 426
 427         impl AsRef<[u8]> for InvoiceRequest {
 428                 fn as_ref(&self) -> &[u8] {
 429                         &self.bytes
 430                 }
 431         }
 432
 433         impl Bech32Encode for InvoiceRequest {
 434                 const BECH32_HRP: &'static str = "lnr";
 435         }
 436
 437         impl core::fmt::Display for InvoiceRequest {
 438                 fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 439                         self.fmt_bech32_str(f)
 440                 }
 441         }
 442 }