feat: replace sequence and confirmBy with hostBlockNumber (#48)

Author: anna-carroll

.gas-snapshot

@@ -1,6 +1,5 @@
-ZenithTest:test_badSequence() (gas: 60268)
-ZenithTest:test_badSignature() (gas: 66936)
-ZenithTest:test_blockExpired() (gas: 55499)
-ZenithTest:test_notSequencer() (gas: 58618)
-ZenithTest:test_onePerBlock() (gas: 104426)
-ZenithTest:test_submitBlock() (gas: 88526)
+ZenithTest:test_badSignature() (gas: 37377)
+ZenithTest:test_incorrectHostBlock() (gas: 35200)
+ZenithTest:test_notSequencer() (gas: 34145)
+ZenithTest:test_onePerBlock() (gas: 68365)
+ZenithTest:test_submitBlock() (gas: 61143)

src/Zenith.sol

@@ -7,29 +7,25 @@ contract Zenith is Passage {
     /// @notice The address that is allowed to set/remove sequencers.
     address public immutable sequencerAdmin;
 
+    /// @notice The block number at which the Zenith contract was deployed.
+    uint256 public deployBlockNumber;
+
     /// @notice Block header information for the rollup block, signed by the sequencer.
     /// @param rollupChainId - the chainId of the rollup chain. Any chainId is accepted by the contract.
-    /// @param sequence - the sequence number of the rollup block. Must be monotonically increasing. Enforced by the contract.
-    /// @param confirmBy - the timestamp by which the block must be submitted. Enforced by the contract.
+    /// @param hostBlockNumber - the host block number in which the rollup block must be submitted. Enforced by the contract.
     /// @param gasLimit - the gas limit for the rollup block. Ignored by the contract; enforced by the Node.
     /// @param rewardAddress - the address to receive the rollup block reward. Ignored by the contract; enforced by the Node.
     /// @param blockDataHash - keccak256(rlp-encoded transactions). the Node will discard the block if the hash doens't match.
     ///                        this allows the sequencer to sign over finalized set of transactions,
     ///                        without the Zenith contract needing to interact with raw transaction data (which may be provided via blobs or calldata).
     struct BlockHeader {
         uint256 rollupChainId;
-        uint256 sequence;
-        uint256 confirmBy;
+        uint256 hostBlockNumber;
         uint256 gasLimit;
         address rewardAddress;
         bytes32 blockDataHash;
     }
 
-    /// @notice The sequence number of the next block that can be submitted for a given rollup chainId.
-    /// @dev Because sequences must start at 1, accessors must add 1 to this number.
-    /// rollupChainId => (nextSequence - 1)
-    mapping(uint256 => uint256) sequences;
-
     /// @notice The host block number that a block was last submitted at for a given rollup chainId.
     /// rollupChainId => host blockNumber that block was last submitted at
     mapping(uint256 => uint256) public lastSubmittedAtBlock;
@@ -38,13 +34,8 @@ contract Zenith is Passage {
     /// address => TRUE if it's a permissioned sequencer
     mapping(address => bool) public isSequencer;
 
-    /// @notice Thrown when a block submission is attempted with a sequence number that is not the next block for the rollup chainId.
-    /// @dev Blocks must be submitted in strict monotonic increasing order.
-    /// @param expected - the correct next sequence number for the given rollup chainId.
-    error BadSequence(uint256 expected);
-
-    /// @notice Thrown when a block submission is attempted when the confirmBy time has passed.
-    error BlockExpired();
+    /// @notice Thrown when a block submission is attempted in the incorrect host block.
+    error IncorrectHostBlock();
 
     /// @notice Thrown when a block submission is attempted with a signature by a non-permissioned sequencer,
     ///         OR when signature is produced over different block header than is provided.
@@ -60,17 +51,13 @@ contract Zenith is Passage {
     /// @notice Emitted when a new rollup block is successfully submitted.
     /// @param sequencer - the address of the sequencer that signed the block.
     /// @param rollupChainId - the chainId of the rollup chain.
-    /// @param sequence - the sequence number of the rollup block.
-    /// @param confirmBy - the timestamp by which the block must be submitted.
     /// @param gasLimit - the gas limit for the rollup block.
     /// @param rewardAddress - the address to receive the rollup block reward.
     /// @param blockDataHash - keccak256(rlp-encoded transactions). the Node will discard the block if the hash doens't match transactions provided.
     /// @dev including blockDataHash allows the sequencer to sign over finalized block data, without needing to calldatacopy the `blockData` param.
     event BlockSubmitted(
         address indexed sequencer,
         uint256 indexed rollupChainId,
-        uint256 indexed sequence,
-        uint256 confirmBy,
         uint256 gasLimit,
         address rewardAddress,
         bytes32 blockDataHash
@@ -83,22 +70,7 @@ contract Zenith is Passage {
         Passage(_defaultRollupChainId, _withdrawalAdmin)
     {
         sequencerAdmin = _sequencerAdmin;
-    }
-
-    /// @notice Returns the next sequence number.
-    /// @dev Because sequences must start at 1, we add 1 to the mapping value.
-    /// @param _rollupChainId - the chainId of the rollup chain. Any chainId is accepted by the contract.
-    /// @return The next sequence number.
-    function nextSequence(uint256 _rollupChainId) public view returns (uint256) {
-        return sequences[_rollupChainId] + 1;
-    }
-
-    /// @notice Increments the sequence number and returns it.
-    /// @dev Because sequences must start at 1, we add 1 to the mapping value.
-    /// @param _rollupChainId - the chainId of the rollup chain. Any chainId is accepted by the contract.
-    /// @return The next sequence number.
-    function incrementSequence(uint256 _rollupChainId) internal returns (uint256) {
-        return ++sequences[_rollupChainId];
+        deployBlockNumber = block.number;
     }
 
     /// @notice Add a sequencer to the permissioned sequencer list.
@@ -129,19 +101,14 @@ contract Zenith is Passage {
     /// @param v - the v component of the Sequencer's ECSDA signature over the block header.
     /// @param r - the r component of the Sequencer's ECSDA signature over the block header.
     /// @param s - the s component of the Sequencer's ECSDA signature over the block header.
-    /// @custom:reverts BadSequence if the sequence number is not the next block for the given rollup chainId.
-    /// @custom:reverts BlockExpired if the confirmBy time has passed.
+    /// @custom:reverts IncorrectHostBlock if the hostBlockNumber does not match the current block.
     /// @custom:reverts BadSignature if the signer is not a permissioned sequencer,
     ///                 OR if the signature provided commits to a different header.
     /// @custom:reverts OneRollupBlockPerHostBlock if attempting to submit a second rollup block within one host block.
     /// @custom:emits BlockSubmitted if the block is successfully submitted.
     function submitBlock(BlockHeader memory header, uint8 v, bytes32 r, bytes32 s, bytes calldata) external {
-        // assert that the sequence number is valid and increment it
-        uint256 _nextSequence = incrementSequence(header.rollupChainId);
-        if (_nextSequence != header.sequence) revert BadSequence(_nextSequence);
-
-        // assert that confirmBy time has not passed
-        if (block.timestamp > header.confirmBy) revert BlockExpired();
+        // assert that the host block number matches the current block
+        if (block.number != header.hostBlockNumber) revert IncorrectHostBlock();
 
         // derive sequencer from signature over block header
         bytes32 blockCommit = blockCommitment(header);
@@ -156,13 +123,7 @@ contract Zenith is Passage {
 
         // emit event
         emit BlockSubmitted(
-            sequencer,
-            header.rollupChainId,
-            header.sequence,
-            header.confirmBy,
-            header.gasLimit,
-            header.rewardAddress,
-            header.blockDataHash
+            sequencer, header.rollupChainId, header.gasLimit, header.rewardAddress, header.blockDataHash
         );
     }
 
@@ -174,9 +135,8 @@ contract Zenith is Passage {
             "init4.sequencer.v0",
             block.chainid,
             header.rollupChainId,
-            header.sequence,
+            header.hostBlockNumber,
             header.gasLimit,
-            header.confirmBy,
             header.rewardAddress,
             header.blockDataHash
         );

test/Zenith.t.sol

@@ -18,8 +18,6 @@ contract ZenithTest is Test {
     event BlockSubmitted(
         address indexed sequencer,
         uint256 indexed rollupChainId,
-        uint256 indexed sequence,
-        uint256 confirmBy,
         uint256 gasLimit,
         address rewardAddress,
         bytes32 blockDataHash
@@ -31,8 +29,7 @@ contract ZenithTest is Test {
 
         // set default block values
         header.rollupChainId = block.chainid + 1;
-        header.sequence = 1; // first block has index 1
-        header.confirmBy = block.timestamp + 10 minutes;
+        header.hostBlockNumber = block.number;
         header.gasLimit = 30_000_000;
         header.rewardAddress = address(this);
         header.blockDataHash = keccak256(blockData);
@@ -41,29 +38,16 @@ contract ZenithTest is Test {
         commit = target.blockCommitment(header);
     }
 
-    // cannot submit block with incorrect sequence number
-    function test_badSequence() public {
-        // change to incorrect sequence number
-        header.sequence = 100;
+    // cannot submit block with incorrect host block number
+    function test_incorrectHostBlock() public {
+        // change to incorrect host block number
+        header.hostBlockNumber = 100;
         commit = target.blockCommitment(header);
 
         // sign block commitmenet with sequencer key
         (uint8 v, bytes32 r, bytes32 s) = vm.sign(sequencerKey, commit);
 
-        vm.expectRevert(abi.encodeWithSelector(Zenith.BadSequence.selector, 1));
-        target.submitBlock(header, v, r, s, blockData);
-    }
-
-    // cannot submit block with expired confirmBy time
-    function test_blockExpired() public {
-        // change to expired confirmBy time
-        header.confirmBy = block.timestamp - 1;
-        commit = target.blockCommitment(header);
-
-        // sign block commitmenet with sequencer key
-        (uint8 v, bytes32 r, bytes32 s) = vm.sign(sequencerKey, commit);
-
-        vm.expectRevert(abi.encodeWithSelector(Zenith.BlockExpired.selector));
+        vm.expectRevert(Zenith.IncorrectHostBlock.selector);
         target.submitBlock(header, v, r, s, blockData);
     }
 
@@ -75,18 +59,9 @@ contract ZenithTest is Test {
         // should emit BlockSubmitted event
         vm.expectEmit();
         emit BlockSubmitted(
-            vm.addr(sequencerKey),
-            header.rollupChainId,
-            header.sequence,
-            header.confirmBy,
-            header.gasLimit,
-            header.rewardAddress,
-            header.blockDataHash
+            vm.addr(sequencerKey), header.rollupChainId, header.gasLimit, header.rewardAddress, header.blockDataHash
         );
         target.submitBlock(header, v, r, s, blockData);
-
-        // should increment sequence number
-        assertEq(target.nextSequence(header.rollupChainId), header.sequence + 1);
     }
 
     // cannot submit block with invalid sequencer signer from non-permissioned key
@@ -104,7 +79,7 @@ contract ZenithTest is Test {
         (uint8 v, bytes32 r, bytes32 s) = vm.sign(sequencerKey, commit);
 
         // change header data from what was signed by sequencer
-        header.confirmBy = block.timestamp + 15 minutes;
+        header.rewardAddress = address(0);
         bytes32 newCommit = target.blockCommitment(header);
         address derivedSigner = ecrecover(newCommit, v, r, s);
 
@@ -120,24 +95,13 @@ contract ZenithTest is Test {
         // should emit BlockSubmitted event
         vm.expectEmit();
         emit BlockSubmitted(
-            vm.addr(sequencerKey),
-            header.rollupChainId,
-            header.sequence,
-            header.confirmBy,
-            header.gasLimit,
-            header.rewardAddress,
-            header.blockDataHash
+            vm.addr(sequencerKey), header.rollupChainId, header.gasLimit, header.rewardAddress, header.blockDataHash
         );
         target.submitBlock(header, v, r, s, blockData);
 
-        // incerement the header sequence
-        header.sequence += 1;
-        commit = target.blockCommitment(header);
-        (v, r, s) = vm.sign(sequencerKey, commit);
-
         // should revert with OneRollupBlockPerHostBlock
-        // (NOTE: this test works because forge does not increment block.number when it mines a transaction)
-        vm.expectRevert(abi.encodeWithSelector(Zenith.OneRollupBlockPerHostBlock.selector));
+        // (NOTE: this test works without changing the Header because forge does not increment block.number when it mines a transaction)
+        vm.expectRevert(Zenith.OneRollupBlockPerHostBlock.selector);
         target.submitBlock(header, v, r, s, blockData);
     }
 }