Audit/oz co2 match transition indexing 187 (#79)

* match global indexes

* index fix

* invalid global index test cleanup

packages/contracts/contracts/optimistic-ethereum/OVM/verification/OVM_FraudVerifier.sol

@@ -26,7 +26,7 @@ contract OVM_FraudVerifier is Lib_AddressResolver, OVM_FraudContributor, iOVM_Fr
      *******************************************/
 
     mapping (bytes32 => iOVM_StateTransitioner) internal transitioners;
-    
+
 
     /***************
      * Constructor *
@@ -95,7 +95,7 @@ contract OVM_FraudVerifier is Lib_AddressResolver, OVM_FraudContributor, iOVM_Fr
         if (_hasStateTransitioner(_preStateRoot)) {
             return;
         }
-        
+
         iOVM_StateCommitmentChain ovmStateCommitmentChain = iOVM_StateCommitmentChain(resolve("OVM_StateCommitmentChain"));
         iOVM_CanonicalTransactionChain ovmCanonicalTransactionChain = iOVM_CanonicalTransactionChain(resolve("OVM_CanonicalTransactionChain"));
 
@@ -118,6 +118,11 @@ contract OVM_FraudVerifier is Lib_AddressResolver, OVM_FraudContributor, iOVM_Fr
             "Invalid transaction inclusion proof."
         );
 
+        require (
+            _preStateRootBatchHeader.prevTotalElements + _preStateRootProof.index == _transactionBatchHeader.prevTotalElements + _transactionProof.index,
+            "Pre-state root global index must equal to the transaction root global index."
+        );
+
         transitioners[_preStateRoot] = iOVM_StateTransitionerFactory(
             resolve("OVM_StateTransitionerFactory")
         ).create(

packages/contracts/test/contracts/OVM/verification/OVM_FraudVerifier.spec.ts

@@ -26,6 +26,13 @@ const DUMMY_TX_CHAIN_ELEMENTS = [...Array(10)].map(() => {
   }
 })
 
+const DUMMY_BATCH_PROOFS_WITH_INDEX = [
+  {
+    index: 11,
+    siblings: [NULL_BYTES32],
+  },
+]
+
 describe('OVM_FraudVerifier', () => {
   let AddressManager: Contract
   before(async () => {
@@ -177,6 +184,20 @@ describe('OVM_FraudVerifier', () => {
             await OVM_FraudVerifier.getStateTransitioner(NULL_BYTES32)
           ).to.equal(Mock__OVM_StateTransitioner.address)
         })
+
+        it('should revert when provided with a incorrect transaction root global index', async () => {
+          await expect (
+            OVM_FraudVerifier.initializeFraudVerification(
+              NULL_BYTES32,
+              DUMMY_BATCH_HEADERS[0],
+              DUMMY_BATCH_PROOFS[0],
+              DUMMY_OVM_TRANSACTIONS[0],
+              DUMMY_TX_CHAIN_ELEMENTS[0],
+              DUMMY_BATCH_HEADERS[0],
+              DUMMY_BATCH_PROOFS_WITH_INDEX[0]
+            )
+          ).to.be.revertedWith('Pre-state root global index must equal to the transaction root global index.')
+        })
       })
     })
   })