_ 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 /// A function for signing a [`TaggedHash`].
  87 pub(super) trait SignFn<T: AsRef<TaggedHash>> {
  88         /// Error type returned by the function.
  89         type Error;
  90
  91         /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream.
  92         fn sign(&self, message: &T) -> Result<Signature, Self::Error>;
  93 }
  94
  95 impl<F, E> SignFn<TaggedHash> for F
  96 where
  97         F: Fn(&TaggedHash) -> Result<Signature, E>,
  98 {
  99         type Error = E;
 100
 101         fn sign(&self, message: &TaggedHash) -> Result<Signature, E> {
 102                 self(message)
 103         }
 104 }
 105
 106 /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream, checking if it
 107 /// can be verified with the supplied `pubkey`.
 108 ///
 109 /// Since `message` is any type that implements [`AsRef<TaggedHash>`], `sign` may be a closure that
 110 /// takes a message such as [`Bolt12Invoice`] or [`InvoiceRequest`]. This allows further message
 111 /// verification before signing its [`TaggedHash`].
 112 ///
 113 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 114 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 115 pub(super) fn sign_message<F, T, E>(
 116         f: F, message: &T, pubkey: PublicKey,
 117 ) -> Result<Signature, SignError<E>>
 118 where
 119         F: SignFn<T, Error = E>,
 120         T: AsRef<TaggedHash>,
 121 {
 122         let signature = f.sign(message).map_err(|e| SignError::Signing(e))?;
 123
 124         let digest = message.as_ref().as_digest();
 125         let pubkey = pubkey.into();
 126         let secp_ctx = Secp256k1::verification_only();
 127         secp_ctx.verify_schnorr(&signature, digest, &pubkey).map_err(|e| SignError::Verification(e))?;
 128
 129         Ok(signature)
 130 }
 131
 132 /// Verifies the signature with a pubkey over the given message using a tagged hash as the message
 133 /// digest.
 134 pub(super) fn verify_signature(
 135         signature: &Signature, message: &TaggedHash, pubkey: PublicKey,
 136 ) -> Result<(), secp256k1::Error> {
 137         let digest = message.as_digest();
 138         let pubkey = pubkey.into();
 139         let secp_ctx = Secp256k1::verification_only();
 140         secp_ctx.verify_schnorr(signature, digest, &pubkey)
 141 }
 142
 143 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
 144 /// containing at least one TLV record.
 145 fn root_hash(data: &[u8]) -> sha256::Hash {
 146         let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
 147                 let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
 148                 let mut engine = sha256::Hash::engine();
 149                 engine.input("LnNonce".as_bytes());
 150                 engine.input(first_tlv_record.record_bytes);
 151                 engine
 152         }));
 153         let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
 154         let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
 155
 156         let mut leaves = Vec::new();
 157         let tlv_stream = TlvStream::new(&data[..]);
 158         for record in tlv_stream.skip_signatures() {
 159                 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
 160                 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
 161         }
 162
 163         // Calculate the merkle root hash in place.
 164         let num_leaves = leaves.len();
 165         for level in 0.. {
 166                 let step = 2 << level;
 167                 let offset = step / 2;
 168                 if offset >= num_leaves {
 169                         break;
 170                 }
 171
 172                 let left_branches = (0..num_leaves).step_by(step);
 173                 let right_branches = (offset..num_leaves).step_by(step);
 174                 for (i, j) in left_branches.zip(right_branches) {
 175                         leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
 176                 }
 177         }
 178
 179         *leaves.first().unwrap()
 180 }
 181
 182 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
 183         let engine = tagged_hash_engine(tag);
 184         tagged_hash_from_engine(engine, msg)
 185 }
 186
 187 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
 188         let mut engine = sha256::Hash::engine();
 189         engine.input(tag.as_ref());
 190         engine.input(tag.as_ref());
 191         engine
 192 }
 193
 194 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
 195         engine.input(msg.as_ref());
 196         sha256::Hash::from_engine(engine)
 197 }
 198
 199 fn tagged_branch_hash_from_engine(
 200         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
 201 ) -> sha256::Hash {
 202         if leaf1 < leaf2 {
 203                 engine.input(leaf1.as_ref());
 204                 engine.input(leaf2.as_ref());
 205         } else {
 206                 engine.input(leaf2.as_ref());
 207                 engine.input(leaf1.as_ref());
 208         };
 209         sha256::Hash::from_engine(engine)
 210 }
 211
 212 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
 213 /// well-formed TLV stream.
 214 #[derive(Clone)]
 215 pub(super) struct TlvStream<'a> {
 216         data: io::Cursor<&'a [u8]>,
 217 }
 218
 219 impl<'a> TlvStream<'a> {
 220         pub fn new(data: &'a [u8]) -> Self {
 221                 Self {
 222                         data: io::Cursor::new(data),
 223                 }
 224         }
 225
 226         pub fn range<T>(self, types: T) -> impl core::iter::Iterator<Item = TlvRecord<'a>>
 227         where
 228                 T: core::ops::RangeBounds<u64> + Clone,
 229         {
 230                 let take_range = types.clone();
 231                 self.skip_while(move |record| !types.contains(&record.r#type))
 232                         .take_while(move |record| take_range.contains(&record.r#type))
 233         }
 234
 235         fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
 236                 self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
 237         }
 238 }
 239
 240 /// A slice into a [`TlvStream`] for a record.
 241 pub(super) struct TlvRecord<'a> {
 242         pub(super) r#type: u64,
 243         type_bytes: &'a [u8],
 244         // The entire TLV record.
 245         pub(super) record_bytes: &'a [u8],
 246 }
 247
 248 impl<'a> Iterator for TlvStream<'a> {
 249         type Item = TlvRecord<'a>;
 250
 251         fn next(&mut self) -> Option<Self::Item> {
 252                 if self.data.position() < self.data.get_ref().len() as u64 {
 253                         let start = self.data.position();
 254
 255                         let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 256                         let offset = self.data.position();
 257                         let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
 258
 259                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
 260                         let offset = self.data.position();
 261                         let end = offset + length;
 262
 263                         let _value = &self.data.get_ref()[offset as usize..end as usize];
 264                         let record_bytes = &self.data.get_ref()[start as usize..end as usize];
 265
 266                         self.data.set_position(end);
 267
 268                         Some(TlvRecord { r#type, type_bytes, record_bytes })
 269                 } else {
 270                         None
 271                 }
 272         }
 273 }
 274
 275 /// Encoding for a pre-serialized TLV stream that excludes any signature TLV records.
 276 ///
 277 /// Panics if the wrapped bytes are not a well-formed TLV stream.
 278 pub(super) struct WithoutSignatures<'a>(pub &'a [u8]);
 279
 280 impl<'a> Writeable for WithoutSignatures<'a> {
 281         #[inline]
 282         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 283                 let tlv_stream = TlvStream::new(self.0);
 284                 for record in tlv_stream.skip_signatures() {
 285                         writer.write_all(record.record_bytes)?;
 286                 }
 287                 Ok(())
 288         }
 289 }
 290
 291 #[cfg(test)]
 292 mod tests {
 293         use super::{SIGNATURE_TYPES, TlvStream, WithoutSignatures};
 294
 295         use bitcoin::hashes::{Hash, sha256};
 296         use bitcoin::hashes::hex::FromHex;
 297         use bitcoin::secp256k1::{KeyPair, Message, Secp256k1, SecretKey};
 298         use bitcoin::secp256k1::schnorr::Signature;
 299         use core::convert::Infallible;
 300         use crate::offers::offer::{Amount, OfferBuilder};
 301         use crate::offers::invoice_request::{InvoiceRequest, UnsignedInvoiceRequest};
 302         use crate::offers::parse::Bech32Encode;
 303         use crate::offers::test_utils::{payer_pubkey, recipient_pubkey};
 304         use crate::util::ser::Writeable;
 305
 306         #[test]
 307         fn calculates_merkle_root_hash() {
 308                 // BOLT 12 test vectors
 309                 macro_rules! tlv1 { () => { "010203e8" } }
 310                 macro_rules! tlv2 { () => { "02080000010000020003" } }
 311                 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
 312                 assert_eq!(
 313                         super::root_hash(&<Vec<u8>>::from_hex(tlv1!()).unwrap()),
 314                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
 315                 );
 316                 assert_eq!(
 317                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!())).unwrap()),
 318                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
 319                 );
 320                 assert_eq!(
 321                         super::root_hash(&<Vec<u8>>::from_hex(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
 322                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
 323                 );
 324         }
 325
 326         #[test]
 327         fn calculates_merkle_root_hash_from_invoice_request() {
 328                 let secp_ctx = Secp256k1::new();
 329                 let recipient_pubkey = {
 330                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4141414141414141414141414141414141414141414141414141414141414141").unwrap()).unwrap();
 331                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 332                 };
 333                 let payer_keys = {
 334                         let secret_key = SecretKey::from_slice(&<Vec<u8>>::from_hex("4242424242424242424242424242424242424242424242424242424242424242").unwrap()).unwrap();
 335                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 336                 };
 337
 338                 // BOLT 12 test vectors
 339                 let invoice_request = OfferBuilder::new("A Mathematical Treatise".into(), recipient_pubkey)
 340                         .amount(Amount::Currency { iso4217_code: *b"USD", amount: 100 })
 341                         .build_unchecked()
 342                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 343                         .build_unchecked()
 344                         .sign(|message: &UnsignedInvoiceRequest| -> Result<_, Infallible> {
 345                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 346                         })
 347                         .unwrap();
 348                 assert_eq!(
 349                         invoice_request.to_string(),
 350                         "lnr1qqyqqqqqqqqqqqqqqcp4256ypqqkgzshgysy6ct5dpjk6ct5d93kzmpq23ex2ct5d9ek293pqthvwfzadd7jejes8q9lhc4rvjxd022zv5l44g6qah82ru5rdpnpjkppqvjx204vgdzgsqpvcp4mldl3plscny0rt707gvpdh6ndydfacz43euzqhrurageg3n7kafgsek6gz3e9w52parv8gs2hlxzk95tzeswywffxlkeyhml0hh46kndmwf4m6xma3tkq2lu04qz3slje2rfthc89vss",
 351                 );
 352                 assert_eq!(
 353                         super::root_hash(&invoice_request.bytes[..]),
 354                         sha256::Hash::from_slice(&<Vec<u8>>::from_hex("608407c18ad9a94d9ea2bcdbe170b6c20c462a7833a197621c916f78cf18e624").unwrap()).unwrap(),
 355                 );
 356                 assert_eq!(
 357                         invoice_request.signature(),
 358                         Signature::from_slice(&<Vec<u8>>::from_hex("b8f83ea3288cfd6ea510cdb481472575141e8d8744157f98562d162cc1c472526fdb24befefbdebab4dbb726bbd1b7d8aec057f8fa805187e5950d2bbe0e5642").unwrap()).unwrap(),
 359                 );
 360         }
 361
 362         #[test]
 363         fn compute_tagged_hash() {
 364                 let unsigned_invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
 365                         .amount_msats(1000)
 366                         .build().unwrap()
 367                         .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
 368                         .payer_note("bar".into())
 369                         .build().unwrap();
 370
 371                 // Simply test that we can grab the tag and merkle root exposed by the accessor
 372                 // functions, then use them to succesfully compute a tagged hash.
 373                 let tagged_hash = unsigned_invoice_request.as_ref();
 374                 let expected_digest = unsigned_invoice_request.as_ref().as_digest();
 375                 let tag = sha256::Hash::hash(tagged_hash.tag().as_bytes());
 376                 let actual_digest = Message::from_slice(super::tagged_hash(tag, tagged_hash.merkle_root()).as_byte_array())
 377                         .unwrap();
 378                 assert_eq!(*expected_digest, actual_digest);
 379         }
 380
 381         #[test]
 382         fn skips_encoding_signature_tlv_records() {
 383                 let secp_ctx = Secp256k1::new();
 384                 let recipient_pubkey = {
 385                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 386                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 387                 };
 388                 let payer_keys = {
 389                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 390                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 391                 };
 392
 393                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 394                         .amount_msats(100)
 395                         .build_unchecked()
 396                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 397                         .build_unchecked()
 398                         .sign(|message: &UnsignedInvoiceRequest| -> Result<_, Infallible> {
 399                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 400                         })
 401                         .unwrap();
 402
 403                 let mut bytes_without_signature = Vec::new();
 404                 WithoutSignatures(&invoice_request.bytes).write(&mut bytes_without_signature).unwrap();
 405
 406                 assert_ne!(bytes_without_signature, invoice_request.bytes);
 407                 assert_eq!(
 408                         TlvStream::new(&bytes_without_signature).count(),
 409                         TlvStream::new(&invoice_request.bytes).count() - 1,
 410                 );
 411         }
 412
 413         #[test]
 414         fn iterates_over_tlv_stream_range() {
 415                 let secp_ctx = Secp256k1::new();
 416                 let recipient_pubkey = {
 417                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
 418                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
 419                 };
 420                 let payer_keys = {
 421                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
 422                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
 423                 };
 424
 425                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
 426                         .amount_msats(100)
 427                         .build_unchecked()
 428                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
 429                         .build_unchecked()
 430                         .sign(|message: &UnsignedInvoiceRequest| -> Result<_, Infallible> {
 431                                 Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
 432                         })
 433                         .unwrap();
 434
 435                 let tlv_stream = TlvStream::new(&invoice_request.bytes).range(0..1)
 436                         .chain(TlvStream::new(&invoice_request.bytes).range(1..80))
 437                         .chain(TlvStream::new(&invoice_request.bytes).range(80..160))
 438                         .chain(TlvStream::new(&invoice_request.bytes).range(160..240))
 439                         .chain(TlvStream::new(&invoice_request.bytes).range(SIGNATURE_TYPES))
 440                         .map(|r| r.record_bytes.to_vec())
 441                         .flatten()
 442                         .collect::<Vec<u8>>();
 443
 444                 assert_eq!(tlv_stream, invoice_request.bytes);
 445         }
 446
 447         impl AsRef<[u8]> for InvoiceRequest {
 448                 fn as_ref(&self) -> &[u8] {
 449                         &self.bytes
 450                 }
 451         }
 452
 453         impl Bech32Encode for InvoiceRequest {
 454                 const BECH32_HRP: &'static str = "lnr";
 455         }
 456
 457         impl core::fmt::Display for InvoiceRequest {
 458                 fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 459                         self.fmt_bech32_str(f)
 460                 }
 461         }
 462 }