]> git.bitcoin.ninja Git - rust-lightning/blob - lightning/src/offers/merkle.rs
Merge pull request #2248 from TheBlueMatt/2023-04-gossip-check
[rust-lightning] / 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(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                 Self(message_digest(tag, tlv_stream))
42         }
43
44         /// Returns the digest to sign.
45         pub fn as_digest(&self) -> &Message {
46                 &self.0
47         }
48 }
49
50 impl AsRef<TaggedHash> for TaggedHash {
51         fn as_ref(&self) -> &TaggedHash {
52                 self
53         }
54 }
55
56 /// Error when signing messages.
57 #[derive(Debug, PartialEq)]
58 pub enum SignError<E> {
59         /// User-defined error when signing the message.
60         Signing(E),
61         /// Error when verifying the produced signature using the given pubkey.
62         Verification(secp256k1::Error),
63 }
64
65 /// Signs a [`TaggedHash`] computed over the merkle root of `message`'s TLV stream, checking if it
66 /// can be verified with the supplied `pubkey`.
67 ///
68 /// Since `message` is any type that implements [`AsRef<TaggedHash>`], `sign` may be a closure that
69 /// takes a message such as [`Bolt12Invoice`] or [`InvoiceRequest`]. This allows further message
70 /// verification before signing its [`TaggedHash`].
71 ///
72 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
73 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
74 pub(super) fn sign_message<F, E, T>(
75         sign: F, message: &T, pubkey: PublicKey,
76 ) -> Result<Signature, SignError<E>>
77 where
78         F: FnOnce(&T) -> Result<Signature, E>,
79         T: AsRef<TaggedHash>,
80 {
81         let signature = sign(message).map_err(|e| SignError::Signing(e))?;
82
83         let digest = message.as_ref().as_digest();
84         let pubkey = pubkey.into();
85         let secp_ctx = Secp256k1::verification_only();
86         secp_ctx.verify_schnorr(&signature, digest, &pubkey).map_err(|e| SignError::Verification(e))?;
87
88         Ok(signature)
89 }
90
91 /// Verifies the signature with a pubkey over the given message using a tagged hash as the message
92 /// digest.
93 pub(super) fn verify_signature(
94         signature: &Signature, message: TaggedHash, pubkey: PublicKey,
95 ) -> Result<(), secp256k1::Error> {
96         let digest = message.as_digest();
97         let pubkey = pubkey.into();
98         let secp_ctx = Secp256k1::verification_only();
99         secp_ctx.verify_schnorr(signature, digest, &pubkey)
100 }
101
102 pub(super) fn message_digest(tag: &str, bytes: &[u8]) -> Message {
103         let tag = sha256::Hash::hash(tag.as_bytes());
104         let merkle_root = root_hash(bytes);
105         Message::from_slice(&tagged_hash(tag, merkle_root)).unwrap()
106 }
107
108 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
109 /// containing at least one TLV record.
110 fn root_hash(data: &[u8]) -> sha256::Hash {
111         let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
112                 let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
113                 let mut engine = sha256::Hash::engine();
114                 engine.input("LnNonce".as_bytes());
115                 engine.input(first_tlv_record.record_bytes);
116                 engine
117         }));
118         let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
119         let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
120
121         let mut leaves = Vec::new();
122         let tlv_stream = TlvStream::new(&data[..]);
123         for record in tlv_stream.skip_signatures() {
124                 leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
125                 leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
126         }
127
128         // Calculate the merkle root hash in place.
129         let num_leaves = leaves.len();
130         for level in 0.. {
131                 let step = 2 << level;
132                 let offset = step / 2;
133                 if offset >= num_leaves {
134                         break;
135                 }
136
137                 let left_branches = (0..num_leaves).step_by(step);
138                 let right_branches = (offset..num_leaves).step_by(step);
139                 for (i, j) in left_branches.zip(right_branches) {
140                         leaves[i] = tagged_branch_hash_from_engine(branch_tag.clone(), leaves[i], leaves[j]);
141                 }
142         }
143
144         *leaves.first().unwrap()
145 }
146
147 fn tagged_hash<T: AsRef<[u8]>>(tag: sha256::Hash, msg: T) -> sha256::Hash {
148         let engine = tagged_hash_engine(tag);
149         tagged_hash_from_engine(engine, msg)
150 }
151
152 fn tagged_hash_engine(tag: sha256::Hash) -> sha256::HashEngine {
153         let mut engine = sha256::Hash::engine();
154         engine.input(tag.as_ref());
155         engine.input(tag.as_ref());
156         engine
157 }
158
159 fn tagged_hash_from_engine<T: AsRef<[u8]>>(mut engine: sha256::HashEngine, msg: T) -> sha256::Hash {
160         engine.input(msg.as_ref());
161         sha256::Hash::from_engine(engine)
162 }
163
164 fn tagged_branch_hash_from_engine(
165         mut engine: sha256::HashEngine, leaf1: sha256::Hash, leaf2: sha256::Hash,
166 ) -> sha256::Hash {
167         if leaf1 < leaf2 {
168                 engine.input(leaf1.as_ref());
169                 engine.input(leaf2.as_ref());
170         } else {
171                 engine.input(leaf2.as_ref());
172                 engine.input(leaf1.as_ref());
173         };
174         sha256::Hash::from_engine(engine)
175 }
176
177 /// [`Iterator`] over a sequence of bytes yielding [`TlvRecord`]s. The input is assumed to be a
178 /// well-formed TLV stream.
179 #[derive(Clone)]
180 pub(super) struct TlvStream<'a> {
181         data: io::Cursor<&'a [u8]>,
182 }
183
184 impl<'a> TlvStream<'a> {
185         pub fn new(data: &'a [u8]) -> Self {
186                 Self {
187                         data: io::Cursor::new(data),
188                 }
189         }
190
191         pub fn range<T>(self, types: T) -> impl core::iter::Iterator<Item = TlvRecord<'a>>
192         where
193                 T: core::ops::RangeBounds<u64> + Clone,
194         {
195                 let take_range = types.clone();
196                 self.skip_while(move |record| !types.contains(&record.r#type))
197                         .take_while(move |record| take_range.contains(&record.r#type))
198         }
199
200         fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
201                 self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
202         }
203 }
204
205 /// A slice into a [`TlvStream`] for a record.
206 pub(super) struct TlvRecord<'a> {
207         pub(super) r#type: u64,
208         type_bytes: &'a [u8],
209         // The entire TLV record.
210         pub(super) record_bytes: &'a [u8],
211 }
212
213 impl<'a> Iterator for TlvStream<'a> {
214         type Item = TlvRecord<'a>;
215
216         fn next(&mut self) -> Option<Self::Item> {
217                 if self.data.position() < self.data.get_ref().len() as u64 {
218                         let start = self.data.position();
219
220                         let r#type = <BigSize as Readable>::read(&mut self.data).unwrap().0;
221                         let offset = self.data.position();
222                         let type_bytes = &self.data.get_ref()[start as usize..offset as usize];
223
224                         let length = <BigSize as Readable>::read(&mut self.data).unwrap().0;
225                         let offset = self.data.position();
226                         let end = offset + length;
227
228                         let _value = &self.data.get_ref()[offset as usize..end as usize];
229                         let record_bytes = &self.data.get_ref()[start as usize..end as usize];
230
231                         self.data.set_position(end);
232
233                         Some(TlvRecord { r#type, type_bytes, record_bytes })
234                 } else {
235                         None
236                 }
237         }
238 }
239
240 /// Encoding for a pre-serialized TLV stream that excludes any signature TLV records.
241 ///
242 /// Panics if the wrapped bytes are not a well-formed TLV stream.
243 pub(super) struct WithoutSignatures<'a>(pub &'a [u8]);
244
245 impl<'a> Writeable for WithoutSignatures<'a> {
246         #[inline]
247         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
248                 let tlv_stream = TlvStream::new(self.0);
249                 for record in tlv_stream.skip_signatures() {
250                         writer.write_all(record.record_bytes)?;
251                 }
252                 Ok(())
253         }
254 }
255
256 #[cfg(test)]
257 mod tests {
258         use super::{SIGNATURE_TYPES, TlvStream, WithoutSignatures};
259
260         use bitcoin::hashes::{Hash, sha256};
261         use bitcoin::secp256k1::{KeyPair, Secp256k1, SecretKey};
262         use bitcoin::secp256k1::schnorr::Signature;
263         use core::convert::Infallible;
264         use crate::offers::offer::{Amount, OfferBuilder};
265         use crate::offers::invoice_request::InvoiceRequest;
266         use crate::offers::parse::Bech32Encode;
267         use crate::util::ser::Writeable;
268
269         #[test]
270         fn calculates_merkle_root_hash() {
271                 // BOLT 12 test vectors
272                 macro_rules! tlv1 { () => { "010203e8" } }
273                 macro_rules! tlv2 { () => { "02080000010000020003" } }
274                 macro_rules! tlv3 { () => { "03310266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c0351800000000000000010000000000000002" } }
275                 assert_eq!(
276                         super::root_hash(&hex::decode(tlv1!()).unwrap()),
277                         sha256::Hash::from_slice(&hex::decode("b013756c8fee86503a0b4abdab4cddeb1af5d344ca6fc2fa8b6c08938caa6f93").unwrap()).unwrap(),
278                 );
279                 assert_eq!(
280                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!())).unwrap()),
281                         sha256::Hash::from_slice(&hex::decode("c3774abbf4815aa54ccaa026bff6581f01f3be5fe814c620a252534f434bc0d1").unwrap()).unwrap(),
282                 );
283                 assert_eq!(
284                         super::root_hash(&hex::decode(concat!(tlv1!(), tlv2!(), tlv3!())).unwrap()),
285                         sha256::Hash::from_slice(&hex::decode("ab2e79b1283b0b31e0b035258de23782df6b89a38cfa7237bde69aed1a658c5d").unwrap()).unwrap(),
286                 );
287         }
288
289         #[test]
290         fn calculates_merkle_root_hash_from_invoice_request() {
291                 let secp_ctx = Secp256k1::new();
292                 let recipient_pubkey = {
293                         let secret_key = SecretKey::from_slice(&hex::decode("4141414141414141414141414141414141414141414141414141414141414141").unwrap()).unwrap();
294                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
295                 };
296                 let payer_keys = {
297                         let secret_key = SecretKey::from_slice(&hex::decode("4242424242424242424242424242424242424242424242424242424242424242").unwrap()).unwrap();
298                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
299                 };
300
301                 // BOLT 12 test vectors
302                 let invoice_request = OfferBuilder::new("A Mathematical Treatise".into(), recipient_pubkey)
303                         .amount(Amount::Currency { iso4217_code: *b"USD", amount: 100 })
304                         .build_unchecked()
305                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
306                         .build_unchecked()
307                         .sign::<_, Infallible>(
308                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
309                         )
310                         .unwrap();
311                 assert_eq!(
312                         invoice_request.to_string(),
313                         "lnr1qqyqqqqqqqqqqqqqqcp4256ypqqkgzshgysy6ct5dpjk6ct5d93kzmpq23ex2ct5d9ek293pqthvwfzadd7jejes8q9lhc4rvjxd022zv5l44g6qah82ru5rdpnpjkppqvjx204vgdzgsqpvcp4mldl3plscny0rt707gvpdh6ndydfacz43euzqhrurageg3n7kafgsek6gz3e9w52parv8gs2hlxzk95tzeswywffxlkeyhml0hh46kndmwf4m6xma3tkq2lu04qz3slje2rfthc89vss",
314                 );
315                 assert_eq!(
316                         super::root_hash(&invoice_request.bytes[..]),
317                         sha256::Hash::from_slice(&hex::decode("608407c18ad9a94d9ea2bcdbe170b6c20c462a7833a197621c916f78cf18e624").unwrap()).unwrap(),
318                 );
319                 assert_eq!(
320                         invoice_request.signature(),
321                         Signature::from_slice(&hex::decode("b8f83ea3288cfd6ea510cdb481472575141e8d8744157f98562d162cc1c472526fdb24befefbdebab4dbb726bbd1b7d8aec057f8fa805187e5950d2bbe0e5642").unwrap()).unwrap(),
322                 );
323         }
324
325         #[test]
326         fn skips_encoding_signature_tlv_records() {
327                 let secp_ctx = Secp256k1::new();
328                 let recipient_pubkey = {
329                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
330                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
331                 };
332                 let payer_keys = {
333                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
334                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
335                 };
336
337                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
338                         .amount_msats(100)
339                         .build_unchecked()
340                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
341                         .build_unchecked()
342                         .sign::<_, Infallible>(
343                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
344                         )
345                         .unwrap();
346
347                 let mut bytes_without_signature = Vec::new();
348                 WithoutSignatures(&invoice_request.bytes).write(&mut bytes_without_signature).unwrap();
349
350                 assert_ne!(bytes_without_signature, invoice_request.bytes);
351                 assert_eq!(
352                         TlvStream::new(&bytes_without_signature).count(),
353                         TlvStream::new(&invoice_request.bytes).count() - 1,
354                 );
355         }
356
357         #[test]
358         fn iterates_over_tlv_stream_range() {
359                 let secp_ctx = Secp256k1::new();
360                 let recipient_pubkey = {
361                         let secret_key = SecretKey::from_slice(&[41; 32]).unwrap();
362                         KeyPair::from_secret_key(&secp_ctx, &secret_key).public_key()
363                 };
364                 let payer_keys = {
365                         let secret_key = SecretKey::from_slice(&[42; 32]).unwrap();
366                         KeyPair::from_secret_key(&secp_ctx, &secret_key)
367                 };
368
369                 let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey)
370                         .amount_msats(100)
371                         .build_unchecked()
372                         .request_invoice(vec![0; 8], payer_keys.public_key()).unwrap()
373                         .build_unchecked()
374                         .sign::<_, Infallible>(
375                                 |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &payer_keys))
376                         )
377                         .unwrap();
378
379                 let tlv_stream = TlvStream::new(&invoice_request.bytes).range(0..1)
380                         .chain(TlvStream::new(&invoice_request.bytes).range(1..80))
381                         .chain(TlvStream::new(&invoice_request.bytes).range(80..160))
382                         .chain(TlvStream::new(&invoice_request.bytes).range(160..240))
383                         .chain(TlvStream::new(&invoice_request.bytes).range(SIGNATURE_TYPES))
384                         .map(|r| r.record_bytes.to_vec())
385                         .flatten()
386                         .collect::<Vec<u8>>();
387
388                 assert_eq!(tlv_stream, invoice_request.bytes);
389         }
390
391         impl AsRef<[u8]> for InvoiceRequest {
392                 fn as_ref(&self) -> &[u8] {
393                         &self.bytes
394                 }
395         }
396
397         impl Bech32Encode for InvoiceRequest {
398                 const BECH32_HRP: &'static str = "lnr";
399         }
400
401         impl core::fmt::Display for InvoiceRequest {
402                 fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
403                         self.fmt_bech32_str(f)
404                 }
405         }
406 }