_ Git - rust-lightning/blob - lightning/src/util/message_signing.rs

   1 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   2 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   3 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   4 // You may not use this file except in accordance with one or both of these
   5 // licenses.
   6
   7 //! Lightning message signing and verification lives here. These tools can be used to sign messages using the node's
   8 //! secret so receivers are sure that they come from you. You can also use this to verify that a given message comes
   9 //! from a specific node.
  10 //! Furthermore, these tools can be used to sign / verify messages using ephemeral keys not tied to node's identities.
  11 //!
  12 //! Note this is not part of the specs, but follows lnd's signing and verifying protocol, which can is defined as follows:
  13 //!
  14 //! signature = zbase32(SigRec(sha256d(("Lightning Signed Message:" + msg)))
  15 //! zbase32 from <https://philzimmermann.com/docs/human-oriented-base-32-encoding.txt>
  16 //! SigRec has first byte 31 + recovery id, followed by 64 byte sig.
  17 //!
  18 //! This implementation is compatible with both lnd's and c-lightning's
  19 //!
  20 //! <https://lightning.readthedocs.io/lightning-signmessage.7.html>
  21 //! <https://api.lightning.community/#signmessage>
  22
  23 use crate::prelude::*;
  24 use crate::util::base32;
  25 use bitcoin::hashes::{sha256d, Hash};
  26 use bitcoin::secp256k1::ecdsa::{RecoverableSignature, RecoveryId};
  27 use bitcoin::secp256k1::{Error, Message, PublicKey, Secp256k1, SecretKey};
  28
  29 static LN_MESSAGE_PREFIX: &[u8] = b"Lightning Signed Message:";
  30
  31 fn sigrec_encode(sig_rec: RecoverableSignature) -> Vec<u8> {
  32         let (rid, rsig) = sig_rec.serialize_compact();
  33         let prefix = rid.to_i32() as u8 + 31;
  34
  35         [&[prefix], &rsig[..]].concat()
  36 }
  37
  38 fn sigrec_decode(sig_rec: Vec<u8>) -> Result<RecoverableSignature, Error> {
  39         // Signature must be 64 + 1 bytes long (compact signature + recovery id)
  40         if sig_rec.len() != 65 {
  41                 return Err(Error::InvalidSignature);
  42         }
  43
  44         let rsig = &sig_rec[1..];
  45         let rid = sig_rec[0] as i32 - 31;
  46
  47         match RecoveryId::from_i32(rid) {
  48                 Ok(x) => RecoverableSignature::from_compact(rsig, x),
  49                 Err(e) => Err(e)
  50         }
  51 }
  52
  53 /// Creates a digital signature of a message given a SecretKey, like the node's secret.
  54 /// A receiver knowing the PublicKey (e.g. the node's id) and the message can be sure that the signature was generated by the caller.
  55 /// Signatures are EC recoverable, meaning that given the message and the signature the PublicKey of the signer can be extracted.
  56 pub fn sign(msg: &[u8], sk: &SecretKey) -> Result<String, Error> {
  57         let secp_ctx = Secp256k1::signing_only();
  58         let msg_hash = sha256d::Hash::hash(&[LN_MESSAGE_PREFIX, msg].concat());
  59
  60         let sig = secp_ctx.sign_ecdsa_recoverable(&Message::from_slice(msg_hash.as_byte_array())?, sk);
  61         Ok(base32::Alphabet::ZBase32.encode(&sigrec_encode(sig)))
  62 }
  63
  64 /// Recovers the PublicKey of the signer of the message given the message and the signature.
  65 pub fn recover_pk(msg: &[u8], sig: &str) ->  Result<PublicKey, Error> {
  66         let secp_ctx = Secp256k1::verification_only();
  67         let msg_hash = sha256d::Hash::hash(&[LN_MESSAGE_PREFIX, msg].concat());
  68
  69         match base32::Alphabet::ZBase32.decode(&sig) {
  70                 Ok(sig_rec) => {
  71                         match sigrec_decode(sig_rec) {
  72                                 Ok(sig) => secp_ctx.recover_ecdsa(&Message::from_slice(msg_hash.as_byte_array())?, &sig),
  73                                 Err(e) => Err(e)
  74                         }
  75                 },
  76                 Err(_) => Err(Error::InvalidSignature)
  77         }
  78 }
  79
  80 /// Verifies a message was signed by a PrivateKey that derives to a given PublicKey, given a message, a signature,
  81 /// and the PublicKey.
  82 pub fn verify(msg: &[u8], sig: &str, pk: &PublicKey) -> bool {
  83         match recover_pk(msg, sig) {
  84                 Ok(x) => x == *pk,
  85                 Err(_) => false
  86         }
  87 }
  88
  89 #[cfg(test)]
  90 mod test {
  91         use core::str::FromStr;
  92         use crate::util::message_signing::{sign, recover_pk, verify};
  93         use bitcoin::secp256k1::constants::ONE;
  94         use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
  95
  96         #[test]
  97         fn test_sign() {
  98                 let message = "test message";
  99                 let one_key = SecretKey::from_slice(&ONE).unwrap();
 100                 let zbase32_sig = sign(message.as_bytes(), &one_key);
 101
 102                 assert_eq!(zbase32_sig.unwrap(), "d9tibmnic9t5y41hg7hkakdcra94akas9ku3rmmj4ag9mritc8ok4p5qzefs78c9pqfhpuftqqzhydbdwfg7u6w6wdxcqpqn4sj4e73e")
 103         }
 104
 105         #[test]
 106         fn test_recover_pk() {
 107                 let message = "test message";
 108                 let one_key = SecretKey::from_slice(&ONE).unwrap();
 109                 let sig = "d9tibmnic9t5y41hg7hkakdcra94akas9ku3rmmj4ag9mritc8ok4p5qzefs78c9pqfhpuftqqzhydbdwfg7u6w6wdxcqpqn4sj4e73e";
 110                 let pk = recover_pk(message.as_bytes(), sig);
 111
 112                 assert_eq!(pk.unwrap(), PublicKey::from_secret_key(&Secp256k1::signing_only(), &one_key))
 113         }
 114
 115         #[test]
 116         fn test_verify() {
 117                 let message = "another message";
 118                 let one_key = SecretKey::from_slice(&ONE).unwrap();
 119                 let sig = sign(message.as_bytes(), &one_key).unwrap();
 120                 let pk = PublicKey::from_secret_key(&Secp256k1::signing_only(), &one_key);
 121
 122                 assert!(verify(message.as_bytes(), &sig, &pk))
 123         }
 124
 125         #[test]
 126         fn test_verify_ground_truth_ish() {
 127                 // There are no standard tests vectors for Sign/Verify, using the same tests vectors as c-lightning to see if they are compatible.
 128                 // Taken from https://github.com/ElementsProject/lightning/blob/1275af6fbb02460c8eb2f00990bb0ef9179ce8f3/tests/test_misc.py#L1925-L1938
 129
 130                 let corpus = [
 131                         ["@bitconner",
 132                         "is this compatible?",
 133                         "rbgfioj114mh48d8egqx8o9qxqw4fmhe8jbeeabdioxnjk8z3t1ma1hu1fiswpakgucwwzwo6ofycffbsqusqdimugbh41n1g698hr9t",
 134                         "02b80cabdf82638aac86948e4c06e82064f547768dcef977677b9ea931ea75bab5"],
 135                         ["@duck1123",
 136                         "hi",
 137                         "rnrphcjswusbacjnmmmrynh9pqip7sy5cx695h6mfu64iac6qmcmsd8xnsyczwmpqp9shqkth3h4jmkgyqu5z47jfn1q7gpxtaqpx4xg",
 138                         "02de60d194e1ca5947b59fe8e2efd6aadeabfb67f2e89e13ae1a799c1e08e4a43b"],
 139                         ["@jochemin",
 140                         "hi",
 141                         "ry8bbsopmduhxy3dr5d9ekfeabdpimfx95kagdem7914wtca79jwamtbw4rxh69hg7n6x9ty8cqk33knbxaqftgxsfsaeprxkn1k48p3",
 142                         "022b8ece90ee891cbcdac0c1cc6af46b73c47212d8defbce80265ac81a6b794931"],
 143                 ];
 144
 145                 for c in &corpus {
 146                         assert!(verify(c[1].as_bytes(), c[2], &PublicKey::from_str(c[3]).unwrap()))
 147                 }
 148         }
 149 }
 150