_ 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 #[allow(unused_imports)]
  20 use crate::prelude::*;
  21
  22 /// Valid type range for signature TLV records.
  23 const SIGNATURE_TYPES: core::ops::RangeInclusive<u64> = 240..=1000;
  24
  25 tlv_stream!(SignatureTlvStream, SignatureTlvStreamRef, SIGNATURE_TYPES, {
  26         (240, signature: Signature),
  27 });
  28
  29 /// A hash for use in a specific context by tweaking with a context-dependent tag as per [BIP 340]
  30 /// and computed over the merkle root of a TLV stream to sign as defined in [BOLT 12].
  31 ///
  32 /// [BIP 340]: https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki
  33 /// [BOLT 12]: https://github.com/rustyrussell/lightning-rfc/blob/guilt/offers/12-offer-encoding.md#signature-calculation
  34 #[derive(Clone, Debug, PartialEq)]
  35 pub struct TaggedHash {
  36         tag: &'static str,
  37         merkle_root: sha256::Hash,
  38         digest: Message,
  39 }
  40
  41 impl TaggedHash {
  42         /// Creates a tagged hash with the given parameters.
  43         ///
  44         /// Panics if `tlv_stream` is not a well-formed TLV stream containing at least one TLV record.
  45         pub(super) fn new(tag: &'static str, tlv_stream: &[u8]) -> Self {
  46                 let tag_hash = sha256::Hash::hash(tag.as_bytes());
  47                 let merkle_root = root_hash(tlv_stream);
  48                 let digest = Message::from_slice(tagged_hash(tag_hash, merkle_root).as_byte_array()).unwrap();
  49                 Self {
  50                         tag,
  51                         merkle_root,
  52                         digest,
  53                 }
  54         }
  55
  56         /// Returns the digest to sign.
  57         pub fn as_digest(&self) -> &Message {
  58                 &self.digest
  59         }
  60
  61         /// Returns the tag used in the tagged hash.
  62         pub fn tag(&self) -> &str {
  63                 &self.tag
  64         }
  65
  66         /// Returns the merkle root used in the tagged hash.
  67         pub fn merkle_root(&self) -> sha256::Hash {
  68                 self.merkle_root
  69         }
  70 }
  71
  72 impl AsRef<TaggedHash> for TaggedHash {
  73         fn as_ref(&self) -> &TaggedHash {
  74                 self
  75         }
  76 }
  77
  78 /// Error when signing messages.
  79 #[derive(Debug, PartialEq)]
  80 pub enum SignError {
  81         /// User-defined error when signing the message.
  82         Signing,
  83         /// Error when verifying the produced signature using the given pubkey.
  84         Verification(secp256k1::Error),
  85 }
  86
  87 /// A function for signing a [`TaggedHash`].
  88 pub(super) trait SignFn<T: AsRef<TaggedHash>> {
  89         /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream.
  90         fn sign(&self, message: &T) -> Result<Signature, ()>;
  91 }
  92
  93 impl<F> SignFn<TaggedHash> for F
  94 where
  95         F: Fn(&TaggedHash) -> Result<Signature, ()>,
  96 {
  97         fn sign(&self, message: &TaggedHash) -> Result<Signature, ()> {
  98                 self(message)
  99         }
 100 }
 101
 102 /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream, checking if it
 103 /// can be verified with the supplied `pubkey`.
 104 ///
 105 /// Since `message` is any type that implements [`AsRef<TaggedHash>`], `sign` may be a closure that
 106 /// takes a message such as [`Bolt12Invoice`] or [`InvoiceRequest`]. This allows further message
 107 /// verification before signing its [`TaggedHash`].
 108 ///
 109 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 110 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 111 pub(super) fn sign_message<F, T>(
 112         f: F, message: &T, pubkey: PublicKey,
 113 ) -> Result<Signature, SignError>
 114 where
 115         F: SignFn<T>,
 116         T: AsRef<TaggedHash>,
 117 {
 118         let signature = f.sign(message).map_err(|()| SignError::Signing)?;
 119
 120         let digest = message.as_ref().as_digest();
 121         let pubkey = pubkey.into();
 122         let secp_ctx = Secp256k1::verification_only();
 123         secp_ctx.verify_schnorr(&signature, digest, &pubkey).map_err(|e| SignError::Verification(e))?;
 124
 125         Ok(signature)
 126 }
 127
 128 /// Verifies the signature with a pubkey over the given message using a tagged hash as the message
 129 /// digest.
 130 pub(super) fn verify_signature(
 131         signature: &Signature, message: &TaggedHash, pubkey: PublicKey,
 132 ) -> Result<(), secp256k1::Error> {
 133         let digest = message.as_digest();
 134         let pubkey = pubkey.into();
 135         let secp_ctx = Secp256k1::verification_only();
 136         secp_ctx.verify_schnorr(signature, digest, &pubkey)
 137 }
 138
 139 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
 140 /// containing at least one TLV record.
 141 fn root_hash(data: &[u8]) -> sha256::Hash {
 142         let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
 143                 let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
 144                 let mut engine = sha256::Hash::engine();
 145                 engine.input("LnNonce".as_bytes());
 146                 engine.input(first_tlv_record.record_bytes);
 147                 engine
 148         }));
 149         let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
 150         let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
 151
 152         let mut leaves = Vec::new();
 153         let tlv_stream = TlvStream::new(&data[..]);
 154         for record in tlv_stream.skip_signatures() {
 155                 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
 156                 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
 157         }
 158
 159         // Calculate the merkle root hash in place.
 160         let num_leaves = leaves.len();
 161         for level in 0.. {
 162                 let step = 2 << level;
 163                 let offset = step / 2;
 164                 if offset >= num_leaves {
 165                         break;
 166                 }
 167
 168                 let left_branches = (0..num_leaves).step_by(step);
 169                 let right_branches = (offset..num_leaves).step_by(step);
 170                 for (i, j) in left_branches.zip(right_branches) {
 171                         leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
 172                 }
 173         }
 174
 175         *leaves.first().unwrap()
 176 }
 177
 178 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
 179         let engine = tagged_hash_engine(tag);
 180         tagged_hash_from_engine(engine, msg)
 181 }
 182
 183 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
 184         let mut engine = sha256::Hash::engine();
 185         engine.input(tag.as_ref());
 186         engine.input(tag.as_ref());
 187         engine
 188 }
 189
 190 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
 191         engine.input(msg.as_ref());
 192         sha256::Hash::from_engine(engine)
 193 }
 194
 195 fn tagged_branch_hash_from_engine(
 196         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
 197 ) -> sha256::Hash {
 198         if leaf1 < leaf2 {
 199                 engine.input(leaf1.as_ref());
 200                 engine.input(leaf2.as_ref());
 201         } else {
 202                 engine.input(leaf2.as_ref());
 203                 engine.input(leaf1.as_ref());
 204         };
 205         sha256::Hash::from_engine(engine)
 206 }
 207
 208 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
 209 /// well-formed TLV stream.
 210 #[derive(Clone)]
 211 pub(super) struct TlvStream<'a> {
 212         data: io::Cursor<&'a [u8]>,
 213 }
 214
 215 impl<'a> TlvStream<'a> {
 216         pub fn new(data: &'a [u8]) -> Self {
 217                 Self {
 218                         data: io::Cursor::new(data),
 219                 }
 220         }
 221
 222         pub fn range<T>(self, types: T) -> impl core::iter::Iterator<Item = TlvRecord<'a>>
 223         where
 224                 T: core::ops::RangeBounds<u64> + Clone,
 225         {
 226                 let take_range = types.clone();
 227                 self.skip_while(move |record| !types.contains(&record.r#type))
 228                         .take_while(move |record| take_range.contains(&record.r#type))
 229         }
 230
 231         fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
 232                 self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
 233         }
 234 }
 235
 236 /// A slice into a [`TlvStream`] for a record.
 237 pub(super) struct TlvRecord<'a> {
 238         pub(super) r#type: u64,
 239         type_bytes: &'a [u8],
 240         // The entire TLV record.
 241         pub(super) record_bytes: &'a [u8],
 242 }
 243
 244 impl<'a> Iterator for TlvStream<'a> {
 245         type Item = TlvRecord<'a>;
 246
 247         fn next(&mut self) -> Option<Self::Item> {
 248                 if self.data.position() < self.data.get_ref().len() as u64 {
 249                         let start = self.data.position();
 250
 251                         let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 252                         let offset = self.data.position();
 253                         let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
 254
 255                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 256                         let offset = self.data.position();
 257                         let end = offset + length;
 258
 259                         let _value = &self.data.get_ref()[offset as usize..end as usize];
 260                         let record_bytes = &self.data.get_ref()[start as usize..end as usize];
 261
 262                         self.data.set_position(end);
 263
 264                         Some(TlvRecord { r#type, type_bytes, record_bytes })
 265                 } else {
 266                         None
 267                 }
 268         }
 269 }
 270
 271 /// Encoding for a pre-serialized TLV stream that excludes any signature TLV records.
 272 ///
 273 /// Panics if the wrapped bytes are not a well-formed TLV stream.
 274 pub(super) struct WithoutSignatures<'a>(pub &'a [u8]);
 275
 276 impl<'a> Writeable for WithoutSignatures<'a> {
 277         #[inline]
 278         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 279                 let tlv_stream = TlvStream::new(self.0);
 280                 for record in tlv_stream.skip_signatures() {
 281                         writer.write_all(record.record_bytes)?;
 282                 }
 283                 Ok(())
 284         }
 285 }
 286
 287 #[cfg(test)]
 288 mod tests {
 289         use super::{SIGNATURE_TYPES, TlvStream, WithoutSignatures};
 290
 291         use bitcoin::hashes::{Hash, sha256};
 292         use bitcoin::hashes::hex::FromHex;
 293         use bitcoin::secp256k1::{KeyPair, Message, Secp256k1, SecretKey};
 294         use bitcoin::secp256k1::schnorr::Signature;
 295         use crate::offers::offer::{Amount, OfferBuilder};
 296         use crate::offers::invoice_request::{InvoiceRequest, UnsignedInvoiceRequest};
 297         use crate::offers::parse::Bech32Encode;
 298         use crate::offers::test_utils::{payer_pubkey, recipient_pubkey};
 299         use crate::util::ser::Writeable;
 300
 301         #[test]
 302         fn calculates_merkle_root_hash() {
 303                 // BOLT 12 test vectors
 304                 macro_rules! tlv1 { () => { "010203e8" } }
 305                 macro_rules! tlv2 { () => { "02080000010000020003" } }
 306                 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
 307                 assert_eq!(
 308                         super::root_hash(&<Vec<u8>>::from_hex(tlv1!()).unwrap()),
 309                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
 310                 );
 311                 assert_eq!(
 312                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!())).unwrap()),
 313                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
 314                 );
 315                 assert_eq!(
 316                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
 317                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
 318                 );
 319         }
 320
 321         #[test]
 322         fn calculates_merkle_root_hash_from_invoice_request() {
 323                 let secp_ctx = Secp256k1::new();
 324                 let recipient_pubkey = {
 325                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4141414141414141414141414141414141414141414141414141414141414141").unwrap()).unwrap();
 326                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 327                 };
 328                 let payer_keys = {
 329                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4242424242424242424242424242424242424242424242424242424242424242").unwrap()).unwrap();
 330                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 331                 };
 332
 333                 // BOLT 12 test vectors
 334                 let invoice_request = OfferBuilder::new("A Mathematical Treatise".into(), recipient_pubkey)
 335                         .amount(Amount::Currency { iso4217_code: *b"USD", amount: 100 })
 336                         .build_unchecked()
 337                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 338                         .build_unchecked()
 339                         .sign(|message: &UnsignedInvoiceRequest|
 340                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 341                         )
 342                         .unwrap();
 343                 assert_eq!(
 344                         invoice_request.to_string(),
 345                         "lnr1qqyqqqqqqqqqqqqqqcp4256ypqqkgzshgysy6ct5dpjk6ct5d93kzmpq23ex2ct5d9ek293pqthvwfzadd7jejes8q9lhc4rvjxd022zv5l44g6qah82ru5rdpnpjkppqvjx204vgdzgsqpvcp4mldl3plscny0rt707gvpdh6ndydfacz43euzqhrurageg3n7kafgsek6gz3e9w52parv8gs2hlxzk95tzeswywffxlkeyhml0hh46kndmwf4m6xma3tkq2lu04qz3slje2rfthc89vss",
 346                 );
 347                 assert_eq!(
 348                         super::root_hash(&invoice_request.bytes[..]),
 349                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("608407c18ad9a94d9ea2bcdbe170b6c20c462a7833a197621c916f78cf18e624").unwrap()).unwrap(),
 350                 );
 351                 assert_eq!(
 352                         invoice_request.signature(),
 353                         Signature::from_slice(&<Vec<u8>>::from_hex("b8f83ea3288cfd6ea510cdb481472575141e8d8744157f98562d162cc1c472526fdb24befefbdebab4dbb726bbd1b7d8aec057f8fa805187e5950d2bbe0e5642").unwrap()).unwrap(),
 354                 );
 355         }
 356
 357         #[test]
 358         fn compute_tagged_hash() {
 359                 let unsigned_invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
 360                         .amount_msats(1000)
 361                         .build().unwrap()
 362                         .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
 363                         .payer_note("bar".into())
 364                         .build().unwrap();
 365
 366                 // Simply test that we can grab the tag and merkle root exposed by the accessor
 367                 // functions, then use them to succesfully compute a tagged hash.
 368                 let tagged_hash = unsigned_invoice_request.as_ref();
 369                 let expected_digest = unsigned_invoice_request.as_ref().as_digest();
 370                 let tag = sha256::Hash::hash(tagged_hash.tag().as_bytes());
 371                 let actual_digest = Message::from_slice(super::tagged_hash(tag, tagged_hash.merkle_root()).as_byte_array())
 372                         .unwrap();
 373                 assert_eq!(*expected_digest, actual_digest);
 374         }
 375
 376         #[test]
 377         fn skips_encoding_signature_tlv_records() {
 378                 let secp_ctx = Secp256k1::new();
 379                 let recipient_pubkey = {
 380                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 381                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 382                 };
 383                 let payer_keys = {
 384                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 385                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 386                 };
 387
 388                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 389                         .amount_msats(100)
 390                         .build_unchecked()
 391                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 392                         .build_unchecked()
 393                         .sign(|message: &UnsignedInvoiceRequest|
 394                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 395                         )
 396                         .unwrap();
 397
 398                 let mut bytes_without_signature = Vec::new();
 399                 WithoutSignatures(&invoice_request.bytes).write(&mut bytes_without_signature).unwrap();
 400
 401                 assert_ne!(bytes_without_signature, invoice_request.bytes);
 402                 assert_eq!(
 403                         TlvStream::new(&bytes_without_signature).count(),
 404                         TlvStream::new(&invoice_request.bytes).count() - 1,
 405                 );
 406         }
 407
 408         #[test]
 409         fn iterates_over_tlv_stream_range() {
 410                 let secp_ctx = Secp256k1::new();
 411                 let recipient_pubkey = {
 412                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 413                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 414                 };
 415                 let payer_keys = {
 416                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 417                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 418                 };
 419
 420                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 421                         .amount_msats(100)
 422                         .build_unchecked()
 423                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 424                         .build_unchecked()
 425                         .sign(|message: &UnsignedInvoiceRequest|
 426                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 427                         )
 428                         .unwrap();
 429
 430                 let tlv_stream = TlvStream::new(&invoice_request.bytes).range(0..1)
 431                         .chain(TlvStream::new(&invoice_request.bytes).range(1..80))
 432                         .chain(TlvStream::new(&invoice_request.bytes).range(80..160))
 433                         .chain(TlvStream::new(&invoice_request.bytes).range(160..240))
 434                         .chain(TlvStream::new(&invoice_request.bytes).range(SIGNATURE_TYPES))
 435                         .map(|r| r.record_bytes.to_vec())
 436                         .flatten()
 437                         .collect::<Vec<u8>>();
 438
 439                 assert_eq!(tlv_stream, invoice_request.bytes);
 440         }
 441
 442         impl AsRef<[u8]> for InvoiceRequest {
 443                 fn as_ref(&self) -> &[u8] {
 444                         &self.bytes
 445                 }
 446         }
 447
 448         impl Bech32Encode for InvoiceRequest {
 449                 const BECH32_HRP: &'static str = "lnr";
 450         }
 451
 452         impl core::fmt::Display for InvoiceRequest {
 453                 fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 454                         self.fmt_bech32_str(f)
 455                 }
 456         }
 457 }