feat(applying): validate all inputs in UTxO set (#324)

pallas-applying/src/byron.rs

@@ -1,18 +1,19 @@
 //! Utilities required for Byron-era transaction validation.
 
-use crate::types::{ByronProtParams, UTxOs, ValidationError, ValidationResult};
+use crate::types::{ByronProtParams, MultiEraInput, UTxOs, ValidationError, ValidationResult};
 
 use pallas_primitives::byron::{MintedTxPayload, Tx};
 
 // TODO: implement missing validation rules.
 pub fn validate_byron_tx(
     mtxp: &MintedTxPayload,
-    _utxos: &UTxOs,
+    utxos: &UTxOs,
     _prot_pps: &ByronProtParams,
 ) -> ValidationResult {
     let tx: &Tx = &mtxp.transaction;
     check_ins_not_empty(tx)?;
-    check_outs_not_empty(tx)
+    check_outs_not_empty(tx)?;
+    check_ins_in_utxos(tx, utxos)
 }
 
 fn check_ins_not_empty(tx: &Tx) -> ValidationResult {
@@ -28,3 +29,12 @@ fn check_outs_not_empty(tx: &Tx) -> ValidationResult {
     }
     Ok(())
 }
+
+fn check_ins_in_utxos(tx: &Tx, utxos: &UTxOs) -> ValidationResult {
+    for input in tx.inputs.iter() {
+        if !(utxos.contains_key(&MultiEraInput::from_byron(input))) {
+            return Err(ValidationError::InputMissingInUTxO);
+        }
+    }
+    Ok(())
+}

pallas-applying/src/types.rs

@@ -21,6 +21,7 @@ pub enum MultiEraProtParams<'b> {
 #[derive(Debug)]
 #[non_exhaustive]
 pub enum ValidationError {
+    InputMissingInUTxO,
     TxInsEmpty,
     TxOutsEmpty,
 }

pallas-applying/tests/byron.rs

@@ -117,6 +117,37 @@ mod byron_tests {
             },
         }
     }
+
+    #[test]
+    // The UTxO set does not contain an entry for the single input to this transaction. This
+    // represents the situation where a transaction tries to spend a non-existent UTxO (e.g., one
+    // which has already been spent).
+    fn unfound_utxo() {
+        let protocol_params: ByronProtParams = ByronProtParams;
+        let mut tx_ins: ByronTxIns = empty_tx_ins();
+        let tx_in: ByronTxIn = new_tx_in(rand_tx_id(), 3);
+        add_byron_tx_in(&mut tx_ins, &tx_in);
+        let mut tx_outs: ByronTxOuts = new_tx_outs();
+        let tx_out_addr: Address = new_addr(rand_addr_payload(), 0);
+        let tx_out: ByronTxOut = new_tx_out(tx_out_addr, 99091);
+        add_tx_out(&mut tx_outs, &tx_out);
+        // Note: utxos is empty, hence the only input to this transaction will not be found, for
+        // which an error should be raised.
+        let utxos: UTxOs = new_utxos();
+        let validation_result = mk_byron_tx_and_validate(
+            &new_tx(tx_ins, tx_outs, empty_attributes()),
+            &empty_witnesses(),
+            &utxos,
+            &protocol_params,
+        );
+        match validation_result {
+            Ok(()) => assert!(false, "All inputs must be within the UTxO set."),
+            Err(err) => match err {
+                ValidationError::InputMissingInUTxO => (),
+                _ => assert!(false, "Unexpected error ({:?}).", err),
+            },
+        }
+    }
 }
 
 // Types aliases.