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