ob-game: Prevent a proposal <= `GENESIS_BLOCK_NUMBER`

packages/contracts-bedrock/semver-lock.json

@@ -100,8 +100,8 @@
     "sourceCodeHash": "0xa995b54dce03ddf5c9c47451bd7181996b91398ad66b54ab0b8cbf582863a33e"
   },
   "src/dispute/OutputBisectionGame.sol": {
-    "initCodeHash": "0xd354d78579c42a9f0f8a8c9b5ef04f570fa3bd088f88102b431aca8d48fddaae",
-    "sourceCodeHash": "0x98f65f2f2f07a525d360eba87e624f1cb44c52326f3b3f2bf7b6ee41a7ec4a2c"
+    "initCodeHash": "0xe5799a4c06cf02fa1fba61129bd32d1a4b07df737a1f2b429b1acd7160093f0a",
+    "sourceCodeHash": "0xf95c7b1575988853b10d4ad2219a6031be27278add5073f3e96854f41f75ba62"
   },
   "src/legacy/DeployerWhitelist.sol": {
     "initCodeHash": "0x8de80fb23b26dd9d849f6328e56ea7c173cd9e9ce1f05c9beea559d1720deb3d",

packages/contracts-bedrock/src/dispute/OutputBisectionGame.sol

@@ -6,8 +6,6 @@ import { IOutputBisectionGame } from "src/dispute/interfaces/IOutputBisectionGam
 import { IInitializable } from "src/dispute/interfaces/IInitializable.sol";
 import { IBondManager } from "src/dispute/interfaces/IBondManager.sol";
 import { IBigStepper, IPreimageOracle } from "src/dispute/interfaces/IBigStepper.sol";
-import { L2OutputOracle } from "src/L1/L2OutputOracle.sol";
-import { BlockOracle } from "src/dispute/BlockOracle.sol";
 
 import { Clone } from "src/libraries/Clone.sol";
 import { Types } from "src/libraries/Types.sol";
@@ -83,8 +81,8 @@ contract OutputBisectionGame is IOutputBisectionGame, Clone, ISemver {
     bool internal subgameAtRootResolved;
 
     /// @notice Semantic version.
-    /// @custom:semver 0.0.15
-    string public constant version = "0.0.15";
+    /// @custom:semver 0.0.16
+    string public constant version = "0.0.16";
 
     /// @param _gameType The type ID of the game.
     /// @param _absolutePrestate The absolute prestate of the instruction trace.
@@ -105,9 +103,8 @@ contract OutputBisectionGame is IOutputBisectionGame, Clone, ISemver {
         Duration _gameDuration,
         IBigStepper _vm
     ) {
-        // The split depth cannot be greater than or equal to the max game depth, and it must
-        // be even due to the constraint laid out in `verifyExecBisectionRoot`
-        if (_splitDepth >= _maxGameDepth || _splitDepth % 2 != 0) revert InvalidSplitDepth();
+        // The split depth cannot be greater than or equal to the max game depth.
+        if (_splitDepth >= _maxGameDepth) revert InvalidSplitDepth();
 
         GAME_TYPE = _gameType;
         ABSOLUTE_PRESTATE = _absolutePrestate;
@@ -446,6 +443,13 @@ contract OutputBisectionGame is IOutputBisectionGame, Clone, ISemver {
         //
         // Implicit assumptions:
         // - The `gameStatus` state variable defaults to 0, which is `GameStatus.IN_PROGRESS`
+        //
+        // Explicit checks:
+        // - An output root cannot be proposed at or before the genesis block.
+
+        // Do not allow the game to be initialized if the root claim corresponds to a block at or before the
+        // configured genesis block number.
+        if (l2BlockNumber() <= GENESIS_BLOCK_NUMBER) revert UnexpectedRootClaim(rootClaim());
 
         // Set the game's starting timestamp
         createdAt = Timestamp.wrap(uint64(block.timestamp));

packages/contracts-bedrock/test/dispute/OutputBisectionGame.t.sol

@@ -105,9 +105,7 @@ contract OutputBisectionGame_Test is OutputBisectionGame_Init {
     ////////////////////////////////////////////////////////////////
 
     /// @dev Tests that the constructor of the `OutputBisectionGame` reverts when the `_splitDepth`
-    ///      parameter is either:
-    ///      1. Greater than or equal to the `MAX_GAME_DEPTH`
-    ///      2. Odd
+    ///      parameter is greater than or equal to the `MAX_GAME_DEPTH`
     function test_constructor_wrongArgs_reverts(uint256 _splitDepth) public {
         AlphabetVM2 alphabetVM = new AlphabetVM2(ABSOLUTE_PRESTATE);
 
@@ -125,22 +123,6 @@ contract OutputBisectionGame_Test is OutputBisectionGame_Init {
             _gameDuration: Duration.wrap(7 days),
             _vm: alphabetVM
         });
-
-        // Test that the constructor reverts when the `_splitDepth` parameter is odd.
-        _splitDepth = bound(_splitDepth, 0, 2 ** 3 - 1);
-        if (_splitDepth % 2 == 0) _splitDepth += 1;
-
-        vm.expectRevert(InvalidSplitDepth.selector);
-        new OutputBisectionGame({
-            _gameType: GAME_TYPE,
-            _absolutePrestate: ABSOLUTE_PRESTATE,
-            _maxGameDepth: 2 ** 3,
-            _genesisBlockNumber: 0,
-            _genesisOutputRoot: Hash.wrap(bytes32(0)),
-            _splitDepth: _splitDepth,
-            _gameDuration: Duration.wrap(7 days),
-            _vm: alphabetVM
-        });
     }
 
     /// @dev Tests that the game's root claim is set correctly.
@@ -176,6 +158,16 @@ contract OutputBisectionGame_Test is OutputBisectionGame_Init {
     //          `IOutputBisectionGame` Implementation Tests       //
     ////////////////////////////////////////////////////////////////
 
+    /// @dev Tests that the game cannot be initialized with an output root that commits to <= the configured genesis
+    ///      block number
+    function testFuzz_initialize_cannotProposeGenesis_reverts(uint256 _blockNumber) public {
+        _blockNumber = bound(_blockNumber, 0, gameProxy.GENESIS_BLOCK_NUMBER());
+
+        Claim claim = _dummyClaim();
+        vm.expectRevert(abi.encodeWithSelector(UnexpectedRootClaim.selector, claim));
+        gameProxy = OutputBisectionGame(address(factory.create(GAME_TYPE, claim, abi.encode(_blockNumber))));
+    }
+
     /// @dev Tests that the game is initialized with the correct data.
     function test_initialize_correctData_succeeds() public {
         // Assert that the root claim is initialized correctly.