Check spend tx against libbitcoinconsensus

revault · Jun 17, 2022 · f1a5109 · f1a5109
1 parent 6af6b56
commit f1a5109
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Showing 4 changed files with 38 additions and 3 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -5,6 +5,7 @@ authors = ["Antoine Poinsot <darosior@protonmail.com>"]
 edition = "2018"
 
 [dependencies]
+bitcoinconsensus = "0.19.0-2"
 revault_tx = { version = "0.5", features = ["use-serde"] }
 revault_net = "0.3"
 

diff --git a/src/coordinator.rs b/src/coordinator.rs
@@ -60,7 +60,9 @@ impl CoordinatorClient {
         transport.send_req(&req)
     }
 
-    // Get Spend transaction spending the vault with the given deposit outpoint.
+    /// Get Spend transaction spending the vault with the given deposit outpoint.
+    /// Beware that the spend transaction may be invalid and needs to be verified against
+    /// libbitcoinconsensus.
     pub fn get_spend_transaction(
         &self,
         deposit_outpoint: OutPoint,

diff --git a/src/poller.rs b/src/poller.rs
@@ -18,7 +18,7 @@ use revault_tx::{
         CancelTransaction, RevaultPresignedTransaction, RevaultTransaction, UnvaultTransaction,
     },
     txins::{DepositTxIn, RevaultTxIn, UnvaultTxIn},
-    txouts::DepositTxOut,
+    txouts::{DepositTxOut, RevaultTxOut},
 };
 
 use revault_net::noise::SecretKey as NoisePrivkey;
@@ -400,7 +400,38 @@ fn check_for_unvault(
 
             let candidate_tx = if let Some(client) = coordinator_client {
                 match client.get_spend_transaction(db_vault.deposit_outpoint.clone()) {
-                    Ok(res) => res,
+                    Ok(Some(tx)) => {
+                        let spent_unvault_outpoint = unvault_txin.outpoint();
+                        if let Some(i) = tx
+                            .input
+                            .iter()
+                            .position(|input| input.previous_output == spent_unvault_outpoint)
+                        {
+                            let txout = unvault_txin.txout().txout();
+                            if let Err(e) = bitcoinconsensus::verify(
+                                &txout.script_pubkey.as_bytes(),
+                                txout.value,
+                                &encode::serialize(&tx),
+                                i,
+                            ) {
+                                log::error!(
+                                    "Coordinator sent a suspicious tx {}, libbitcoinconsensus error: {:?}",
+                                    tx.txid(),
+                                    e
+                                );
+                                None
+                            } else {
+                                Some(tx)
+                            }
+                        } else {
+                            log::error!(
+                                "Coordinator sent a suspicious tx {}, the transaction does not spend the vault",
+                                tx.txid(),
+                            );
+                            None
+                        }
+                    }
+                    Ok(None) => None,
                     Err(_e) => {
                         // Because we do not trust the coordinator, we consider it refuses to deliver the
                         // spend tx if a communication error happened.