Audittens audit C01 (#11)

I did a bit more than suggested: used the same function everywhere for
checking whether priority queue is active + put into the same file the
suggested operation to ensure that it is easier to track the invariant

l1-contracts/contracts/state-transition/chain-deps/facets/Admin.sol

@@ -328,6 +328,7 @@ contract AdminFacet is ZKChainBase, IAdmin {
         } else {
             s.priorityTree.initFromCommitment(_commitment.priorityTree);
         }
+        _forceDeactivateQueue();
 
         s.l2SystemContractsUpgradeTxHash = _commitment.l2SystemContractsUpgradeTxHash;
         s.l2SystemContractsUpgradeBatchNumber = _commitment.l2SystemContractsUpgradeBatchNumber;
@@ -366,7 +367,7 @@ contract AdminFacet is ZKChainBase, IAdmin {
     /// @dev Note, that this is a getter method helpful for debugging and should not be relied upon by clients.
     /// @return commitment The commitment for the chain.
     function prepareChainCommitment() public view returns (ZKChainCommitment memory commitment) {
-        require(s.priorityQueue.getFirstUnprocessedPriorityTx() >= s.priorityTree.startIndex, "PQ not ready");
+        require(!_isPriorityQueueActive(), "PQ not ready");
 
         commitment.totalBatchesCommitted = s.totalBatchesCommitted;
         commitment.totalBatchesVerified = s.totalBatchesVerified;

l1-contracts/contracts/state-transition/chain-deps/facets/Executor.sol

@@ -441,13 +441,13 @@ contract ExecutorFacet is ZKChainBase, IExecutor {
         require(batchesData.length == priorityOpsData.length, "bp");
 
         for (uint256 i = 0; i < nBatches; i = i.uncheckedInc()) {
-            if (s.priorityTree.startIndex <= s.priorityQueue.getFirstUnprocessedPriorityTx()) {
-                _executeOneBatch(batchesData[i], priorityOpsData[i], i);
-            } else {
+            if (_isPriorityQueueActive()) {
                 require(priorityOpsData[i].leftPath.length == 0, "le");
                 require(priorityOpsData[i].rightPath.length == 0, "re");
                 require(priorityOpsData[i].itemHashes.length == 0, "ih");
                 _executeOneBatch(batchesData[i], i);
+            } else {
+                _executeOneBatch(batchesData[i], priorityOpsData[i], i);
             }
             emit BlockExecution(batchesData[i].batchNumber, batchesData[i].batchHash, batchesData[i].commitment);
         }

l1-contracts/contracts/state-transition/chain-deps/facets/Getters.sol

@@ -112,10 +112,10 @@ contract GettersFacet is ZKChainBase, IGetters, ILegacyGetters {
 
     /// @inheritdoc IGetters
     function getFirstUnprocessedPriorityTx() external view returns (uint256) {
-        if (s.priorityQueue.getFirstUnprocessedPriorityTx() >= s.priorityTree.startIndex) {
-            return s.priorityTree.getFirstUnprocessedPriorityTx();
-        } else {
+        if (_isPriorityQueueActive()) {
             return s.priorityQueue.getFirstUnprocessedPriorityTx();
+        } else {
+            return s.priorityTree.getFirstUnprocessedPriorityTx();
         }
     }
 
@@ -126,13 +126,18 @@ contract GettersFacet is ZKChainBase, IGetters, ILegacyGetters {
 
     /// @inheritdoc IGetters
     function getPriorityQueueSize() external view returns (uint256) {
-        if (s.priorityQueue.getFirstUnprocessedPriorityTx() >= s.priorityTree.startIndex) {
-            return s.priorityTree.getSize();
-        } else {
+        if (_isPriorityQueueActive()) {
             return s.priorityQueue.getSize();
+        } else {
+            return s.priorityTree.getSize();
         }
     }
 
+    /// @inheritdoc IGetters
+    function isPriorityQueueActive() external view returns (bool) {
+        return _isPriorityQueueActive();
+    }
+
     /// @inheritdoc IGetters
     function isValidator(address _address) external view returns (bool) {
         return s.validators[_address];

l1-contracts/contracts/state-transition/chain-deps/facets/Mailbox.sol

@@ -494,10 +494,10 @@ contract MailboxFacet is ZKChainBase, IMailbox {
     }
 
     function _nextPriorityTxId() internal view returns (uint256) {
-        if (s.priorityQueue.getFirstUnprocessedPriorityTx() >= s.priorityTree.startIndex) {
-            return s.priorityTree.getTotalPriorityTxs();
-        } else {
+        if (_isPriorityQueueActive()) {
             return s.priorityQueue.getTotalPriorityTxs();
+        } else {
+            return s.priorityTree.getTotalPriorityTxs();
         }
     }
 
@@ -570,7 +570,7 @@ contract MailboxFacet is ZKChainBase, IMailbox {
     }
 
     function _writePriorityOpHash(bytes32 _canonicalTxHash, uint64 _expirationTimestamp) internal {
-        if (s.priorityTree.startIndex > s.priorityQueue.getFirstUnprocessedPriorityTx()) {
+        if (_isPriorityQueueActive()) {
             s.priorityQueue.pushBack(
                 PriorityOperation({
                     canonicalTxHash: _canonicalTxHash,

l1-contracts/contracts/state-transition/chain-deps/facets/ZKChainBase.sol

@@ -62,11 +62,29 @@ contract ZKChainBase is ReentrancyGuard {
         _;
     }
 
+    /// @notice Returns whether the priority queue is still active, i.e.
+    /// the chain has not processed all transactions from it
+    function _isPriorityQueueActive() internal view returns (bool) {
+        return s.priorityQueue.getFirstUnprocessedPriorityTx() < s.priorityTree.startIndex;
+    }
+
+    /// @notice Ensures that the queue is deactivated. Should be invoked
+    /// whenever the chain migrates to another settlement layer.
+    function _forceDeactivateQueue() internal {
+        // We double check whether it is still active mainly to prevent
+        // overriding `tail`/`head` on L1 deployment.
+        if (_isPriorityQueueActive()) {
+            uint256 startIndex = s.priorityTree.startIndex;
+            s.priorityQueue.head = startIndex;
+            s.priorityQueue.tail = startIndex;
+        }
+    }
+
     function _getTotalPriorityTxs() internal view returns (uint256) {
-        if (s.priorityQueue.getFirstUnprocessedPriorityTx() >= s.priorityTree.startIndex) {
-            return s.priorityTree.getTotalPriorityTxs();
-        } else {
+        if (_isPriorityQueueActive()) {
             return s.priorityQueue.getTotalPriorityTxs();
+        } else {
+            return s.priorityTree.getTotalPriorityTxs();
         }
     }
 }

l1-contracts/contracts/state-transition/chain-interfaces/IGetters.sol

@@ -59,6 +59,11 @@ interface IGetters is IZKChainBase {
     /// @return The root hash of the priority tree
     function getPriorityTreeRoot() external view returns (bytes32);
 
+    /// @return Whether the priority queue is active, i.e. whether new priority operations are appended to it.
+    /// Once the chain processes all the transaction that were present in the priority queue, all the L1->L2 related
+    /// operations will start to get done using the priority tree.
+    function isPriorityQueueActive() external view returns (bool);
+
     /// @notice The function that returns the first unprocessed priority transaction.
     /// @dev Returns zero if and only if no operations were processed from the queue.
     /// @dev If all the transactions were processed, it will return the last processed index, so

l1-contracts/test/foundry/l1/integration/l2-tests-in-l1-context/L2GatewayTestAbstract.t.sol

@@ -31,12 +31,31 @@ import {IZKChain} from "contracts/state-transition/chain-interfaces/IZKChain.sol
 import {SystemContractsArgs} from "./_SharedL2ContractL1DeployerUtils.sol";
 
 import {DeployUtils} from "deploy-scripts/DeployUtils.s.sol";
+import {GettersFacet} from "contracts/state-transition/chain-deps/facets/Getters.sol";
+import {ZKChainCommitment} from "contracts/common/Config.sol";
 
 abstract contract L2GatewayTestAbstract is Test, SharedL2ContractDeployer {
     function test_gatewayShouldFinalizeDeposit() public {
         finalizeDeposit();
         require(l2Bridgehub.ctmAssetIdFromAddress(address(chainTypeManager)) == ctmAssetId, "ctmAssetId mismatch");
         require(l2Bridgehub.ctmAssetIdFromChainId(mintChainId) == ctmAssetId, "ctmAssetIdFromChainId mismatch");
+
+        address diamondProxy = l2Bridgehub.getZKChain(mintChainId);
+        require(!GettersFacet(diamondProxy).isPriorityQueueActive(), "Priority queue must not be active");
+    }
+
+    function test_gatewayNonEmptyPriorityQueueMigration() public {
+        ZKChainCommitment memory commitment = abi.decode(exampleChainCommitment, (ZKChainCommitment));
+
+        // Some non-zero value which would be the case if a chain existed before the
+        // priority tree was added
+        commitment.priorityTree.startIndex = 101;
+        commitment.priorityTree.nextLeafIndex = 102;
+
+        finalizeDepositWithCustomCommitment(abi.encode(commitment));
+
+        address diamondProxy = l2Bridgehub.getZKChain(mintChainId);
+        require(!GettersFacet(diamondProxy).isPriorityQueueActive(), "Priority queue must not be active");
     }
 
     function test_forwardToL3OnGateway() public {
@@ -66,7 +85,11 @@ abstract contract L2GatewayTestAbstract is Test, SharedL2ContractDeployer {
     }
 
     function finalizeDeposit() public {
-        bytes memory chainData = exampleChainCommitment;
+        finalizeDepositWithCustomCommitment(exampleChainCommitment);
+    }
+
+    function finalizeDepositWithCustomCommitment(bytes memory chainCommitment) public {
+        bytes memory chainData = chainCommitment;
         bytes memory ctmData = abi.encode(
             baseTokenAssetId,
             ownerWallet,

l1-contracts/test/foundry/l1/integration/l2-tests-in-l1-context/_SharedL2ContractDeployer.sol

@@ -29,6 +29,9 @@ import {IBridgehub} from "contracts/bridgehub/IBridgehub.sol";
 import {L2WrappedBaseToken} from "contracts/bridge/L2WrappedBaseToken.sol";
 import {L2SharedBridgeLegacy} from "contracts/bridge/L2SharedBridgeLegacy.sol";
 import {DataEncoding} from "contracts/common/libraries/DataEncoding.sol";
+import {MailboxFacet} from "contracts/state-transition/chain-deps/facets/Mailbox.sol";
+import {AdminFacet} from "contracts/state-transition/chain-deps/facets/Admin.sol";
+import {BridgehubL2TransactionRequest} from "contracts/common/Messaging.sol";
 
 import {IChainTypeManager} from "contracts/state-transition/IChainTypeManager.sol";
 import {IZKChain} from "contracts/state-transition/chain-interfaces/IZKChain.sol";
@@ -126,6 +129,8 @@ abstract contract SharedL2ContractDeployer is Test, DeployUtils {
     }
 
     function getExampleChainCommitment() internal returns (bytes memory) {
+        address chainAdmin = makeAddr("chainAdmin");
+
         vm.mockCall(
             L2_ASSET_ROUTER_ADDR,
             abi.encodeWithSelector(IL1AssetRouter.L1_NULLIFIER.selector),
@@ -140,10 +145,33 @@ abstract contract SharedL2ContractDeployer is Test, DeployUtils {
         address chainAddress = chainTypeManager.createNewChain(
             ERA_CHAIN_ID + 1,
             baseTokenAssetId,
-            address(0x1),
+            chainAdmin,
             abi.encode(config.contracts.diamondCutData, generatedData.forceDeploymentsData),
             new bytes[](0)
         );
+
+        vm.prank(chainAdmin);
+        AdminFacet(chainAddress).setTokenMultiplier(1, 1);
+
+        // Now, let's also append a priority transaction for a more representative example
+        bytes[] memory deps = new bytes[](0);
+
+        vm.prank(address(l2Bridgehub));
+        MailboxFacet(chainAddress).bridgehubRequestL2Transaction(
+            BridgehubL2TransactionRequest({
+                sender: address(0),
+                contractL2: address(0),
+                // Just a giant number so it is always enough
+                mintValue: 1 ether,
+                l2Value: 10,
+                l2Calldata: hex"",
+                l2GasLimit: 72_000_000,
+                l2GasPerPubdataByteLimit: 800,
+                factoryDeps: deps,
+                refundRecipient: address(0)
+            })
+        );
+
         exampleChainCommitment = abi.encode(IZKChain(chainAddress).prepareChainCommitment());
     }