Add arbitrum specific gateway contracts

contracts/src/bridge/IL1Bridge.sol

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+interface IL1Bridge {
+    /**
+     * Sends an arbitrary message from one domain to another.
+     *
+     * @dev The caller needs to pay some ETH to cover the gas costs
+     * of the call on L2. Excess ETH that is not used by gas costs will
+     * be refunded to the `msg.sender` address on L2.
+     *
+     * @notice if a user does not desire immediate redemption, they should
+     * provide a DepositValue of at least CallValue + MaxSubmissionCost.
+     * If they do desire immediate execution, they should provide a DepositValue
+     * of at least CallValue + MaxSubmissionCost + (GasPrice x MaxGas).
+     *
+     * @param _calldata The L2 encoded message data.
+     * @param _maxGas Gas limit for immediate L2 execution attempt.
+     * @param _gasPriceBid L2 Gas price bid for immediate L2 execution attempt.
+     * @return Unique id to track the message request/transaction.
+     */
+    function sendCrossDomainMessage(
+        bytes memory _calldata,
+        uint256 _maxGas,
+        uint256 _gasPriceBid
+    ) external payable returns (uint256);
+
+    function getSubmissionPrice(uint256 _calldatasize) external view returns (uint256);
+
+    function onlyAuthorized() external;
+}

contracts/src/bridge/IL2Bridge.sol

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+interface IL2Bridge {
+    /**
+     * Sends an arbitrary message from one domain to another.
+     *
+     * @param _calldata The L1 encoded message data.
+     * @return Unique id to track the message request/transaction.
+     */
+    function sendCrossDomainMessage(bytes memory _calldata) external returns (uint256);
+
+    function onlyAuthorized() external;
+}

contracts/src/bridge/arbitrum/AddressAliasHelper.sol

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Apache-2.0
+
+/*
+ * Copyright 2019-2021, Offchain Labs, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+pragma solidity >=0.7.0;
+
+library AddressAliasHelper {
+    uint160 constant offset = uint160(0x1111000000000000000000000000000000001111);
+
+    /// @notice Utility function that converts the address in the L1 that submitted a tx to
+    /// the inbox to the msg.sender viewed in the L2
+    /// @param l1Address the address in the L1 that triggered the tx to L2
+    /// @return l2Address L2 address as viewed in msg.sender
+    function applyL1ToL2Alias(address l1Address) internal pure returns (address l2Address) {
+        l2Address = address(uint160(l1Address) + offset);
+    }
+
+    /// @notice Utility function that converts the msg.sender viewed in the L2 to the
+    /// address in the L1 that submitted a tx to the inbox
+    /// @param l2Address L2 address as viewed in msg.sender
+    /// @return l1Address the address in the L1 that triggered the tx to L2
+    function undoL1ToL2Alias(address l2Address) internal pure returns (address l1Address) {
+        l1Address = address(uint160(l2Address) - offset);
+    }
+}

contracts/src/bridge/arbitrum/L1Bridge.sol → contracts/src/bridge/arbitrum/ArbL1Bridge.sol

@@ -3,9 +3,12 @@
 pragma solidity ^0.8.0;
 
 import "./interfaces/IInbox.sol";
+import "./interfaces/IOutbox.sol";
 import "./interfaces/IArbRetryableTx.sol";
 
-contract L1Bridge {
+import "../IL1Bridge.sol";
+
+contract ArbL1Bridge is IL1Bridge {
     address public l2Target;
     IInbox public inbox;
     IArbRetryableTx constant arbRetryableTx = IArbRetryableTx(address(110));
@@ -39,7 +42,8 @@ contract L1Bridge {
         uint256 _maxGas,
         uint256 _gasPriceBid
     ) external payable returns (uint256) {
-        (uint256 baseSubmissionCost, ) = arbRetryableTx.getSubmissionPrice(_calldata.length);
+        uint256 baseSubmissionCost = getSubmissionPrice(_calldata.length);
+        require(msg.value >= baseSubmissionCost + (_maxGas * _gasPriceBid));
 
         uint256 ticketID = inbox.createRetryableTicket{value: msg.value}(
             l2Target,
@@ -55,4 +59,15 @@ contract L1Bridge {
         emit RetryableTicketCreated(ticketID);
         return ticketID;
     }
+
+    function getSubmissionPrice(uint256 _calldatasize) public view returns (uint256) {
+        (uint256 submissionCost, ) = arbRetryableTx.getSubmissionPrice(_calldatasize);
+        return submissionCost;
+    }
+
+    function onlyAuthorized() external {
+        IOutbox outbox = IOutbox(inbox.bridge().activeOutbox());
+        address l2Sender = outbox.l2ToL1Sender();
+        require(l2Sender == l2Target, "Only L2 target");
+    }
 }

contracts/src/bridge/arbitrum/L2Bridge.sol → contracts/src/bridge/arbitrum/ArbL2Bridge.sol

@@ -3,8 +3,11 @@
 pragma solidity ^0.8.0;
 
 import "./interfaces/IArbSys.sol";
+import "./AddressAliasHelper.sol";
 
-contract L2Bridge {
+import "../IL2Bridge.sol";
+
+contract ArbL2Bridge is IL2Bridge {
     address public l1Target;
     IArbSys constant arbsys = IArbSys(address(100));
 
@@ -20,10 +23,14 @@ contract L2Bridge {
      * @param _calldata The L1 encoded message data.
      * @return Unique id to track the message request/transaction.
      */
-    function sendCrossDomainMessage(bytes memory _calldata) external payable returns (uint256) {
+    function sendCrossDomainMessage(bytes memory _calldata) external returns (uint256) {
         uint256 withdrawalId = arbsys.sendTxToL1(l1Target, _calldata);
 
         emit L2ToL1TxCreated(withdrawalId);
         return withdrawalId;
     }
+
+    function onlyAuthorized() external {
+        require(msg.sender == AddressAliasHelper.applyL1ToL2Alias(l1Target), "Only L1 target");
+    }
 }

contracts/src/bridge/xdai/interfaces/IAMB.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+interface IAMB {
+    function requireToPassMessage(
+        address _contract,
+        bytes memory _data,
+        uint256 _gas
+    ) external returns (bytes32);
+
+    function maxGasPerTx() external view returns (uint256);
+
+    function messageSender() external view returns (address);
+
+    function messageSourceChainId() external view returns (bytes32);
+
+    function messageId() external view returns (bytes32);
+}

contracts/src/bridge/xdai/xDaiL1Bridge.sol

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./interfaces/IAMB.sol";
+
+import "../IL1Bridge.sol";
+
+contract xDaiL1Bridge is IL1Bridge {
+    address public l2Target;
+    IAMB amb;
+
+    constructor(address _l2Target, IAMB _amb) {
+        l2Target = _l2Target;
+        amb = _amb;
+    }
+
+    function sendCrossDomainMessage(
+        bytes memory _calldata,
+        uint256 _maxGas,
+        uint256 _gasPriceBid
+    ) external payable returns (uint256) {
+        bytes32 id = amb.requireToPassMessage(l2Target, _calldata, amb.maxGasPerTx());
+        return uint256(id);
+    }
+
+    /**
+     * @dev The xDai bridge gas cost doesn't depend on the calldata size
+     *
+     */
+    function getSubmissionPrice(
+        uint256 /* _calldatasize */
+    ) public view returns (uint256) {
+        return 0;
+    }
+
+    function onlyAuthorized() external {
+        require(msg.sender == address(amb), "Only AMB allowed");
+        // require(amb.messageSourceChainId() == foreignChainId, "Only foreign chain allowed");
+        require(amb.messageSender() == l2Target, "Only foreign gateway allowed");
+    }
+}

contracts/src/bridge/xdai/xDaiL2Bridge.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./interfaces/IAMB.sol";
+
+import "../IL2Bridge.sol";
+
+contract xDaiL2Bridge is IL2Bridge {
+    address public l1Target;
+    IAMB amb;
+
+    constructor(address _l1Target, IAMB _amb) {
+        l1Target = _l1Target;
+        amb = _amb;
+    }
+
+    function sendCrossDomainMessage(bytes memory _calldata) external returns (uint256) {
+        bytes32 id = amb.requireToPassMessage(l1Target, _calldata, amb.maxGasPerTx());
+        return uint256(id);
+    }
+
+    function onlyAuthorized() external {
+        require(msg.sender == address(amb), "Only AMB allowed");
+        // require(amb.messageSourceChainId() == homeChainId, "Only home chain allowed");
+        require(amb.messageSender() == l1Target, "Only home gateway allowed");
+    }
+}

contracts/src/gateway/BaseForeignGateway.sol

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../arbitration/IArbitrable.sol";
+import "../bridge/IL1Bridge.sol";
+
+import "./interfaces/IHomeGateway.sol";
+import "./interfaces/IForeignGateway.sol";
+
+abstract contract BaseForeignGateway is IL1Bridge, IForeignGateway {
+    // @dev Note the disputeID needs to start from one as
+    // the KlerosV1 proxy governor depends on this implementation.
+    uint256 internal localDisputeID = 1;
+
+    // For now this is just a constant, but we'd probably need to
+    // implement the same arbitrationCost calculation code we'll have
+    // in the V2 court.
+    uint256 internal internalArbitrationCost;
+
+    struct DisputeData {
+        uint256 id;
+        address arbitrable;
+    }
+    mapping(uint256 => bytes32) public disputeIDtoHash;
+    mapping(bytes32 => DisputeData) public disputeHashtoDisputeData;
+
+    IHomeGateway public homeGateway;
+    uint256 public chainID;
+
+    modifier onlyFromL2() {
+        this.onlyAuthorized();
+        _;
+    }
+
+    constructor(uint256 _arbitrationCost, IHomeGateway _homeGateway) {
+        internalArbitrationCost = _arbitrationCost;
+        homeGateway = _homeGateway;
+
+        uint256 id;
+        assembly {
+            id := chainid()
+        }
+        chainID = id;
+    }
+
+    function createDispute(uint256 _choices, bytes calldata _extraData) external payable returns (uint256 disputeID) {
+        require(msg.value >= arbitrationCost(_extraData), "Not paid enough for arbitration");
+
+        disputeID = localDisputeID++;
+        bytes32 disputeHash = keccak256(
+            abi.encodePacked(
+                chainID,
+                blockhash(block.number - 1),
+                "createDispute",
+                disputeID,
+                arbitrationCost(_extraData),
+                _extraData,
+                msg.sender
+            )
+        );
+        disputeIDtoHash[disputeID] = disputeHash;
+        disputeHashtoDisputeData[disputeHash] = DisputeData({id: disputeID, arbitrable: msg.sender});
+
+        bytes4 methodSelector = IHomeGateway.relayCreateDispute.selector;
+        bytes memory data = abi.encodeWithSelector(methodSelector, disputeHash, _choices, _extraData);
+
+        uint256 bridgeCost = this.getSubmissionPrice(data.length);
+        // We only pay for the submissionPrice gas cost
+        // which is minimum gas cost required for submitting a
+        // arbitrum retryable ticket to the retry buffer for
+        // bridge to L2.
+        // For immediate inclusion a user/bot needs to pay (GasPrice x MaxGas)
+        // with the associated ticketId that is emitted by this function
+        // after the ticket is successfully submitted.
+        // For more details, see:
+        // https://developer.offchainlabs.com/docs/l1_l2_messages#retryable-tickets-contract-api
+        //
+        // We do NOT forward the arbitrationCost ETH funds to the HomeGateway yet,
+        // only the calldata.
+        this.sendCrossDomainMessage{value: bridgeCost}(data, 0, 0);
+
+        emit DisputeCreation(disputeID, IArbitrable(msg.sender));
+    }
+
+    function arbitrationCost(bytes calldata _extraData) public view returns (uint256 cost) {
+        // Calculate the size of calldata that will be passed to the L2 bridge
+        // as that is a factor for the bridging cost.
+        // Calldata size of relayCreateDispute:
+        // relayCreateDispute methodId +
+        //      (createDispute methodId + bytes32 disputeHash + uint256 _choices + bytes _extraData)
+        //   4      +      4            +   32                +   32             + dynamic
+        uint256 calldatasize = 82 + _extraData.length;
+
+        uint256 bridgeCost = this.getSubmissionPrice(calldatasize);
+        return bridgeCost + internalArbitrationCost;
+    }
+
+    /**
+     * Relay the rule call from the home gateway to the arbitrable.
+     */
+    function relayRule(bytes32 _disputeHash, uint256 _ruling) external onlyFromL2 {
+        DisputeData memory dispute = disputeHashtoDisputeData[_disputeHash];
+
+        IArbitrable arbitrable = IArbitrable(dispute.arbitrable);
+        arbitrable.rule(dispute.id, _ruling);
+    }
+
+    function foreignDisputeHashToID(bytes32 _disputeHash) external view returns (uint256) {
+        return disputeHashtoDisputeData[_disputeHash].id;
+    }
+
+    function disputeID(uint256 _foreignDisputeID) external view returns (uint256) {
+        bytes32 disputeHash = disputeIDtoHash[_foreignDisputeID];
+        require(disputeHash != 0, "Dispute does not exist");
+
+        return homeGateway.homeDisputeHashToID(disputeHash);
+    }
+
+    function homeChainID(uint256 _disputeID) external view returns (uint256) {
+        return homeGateway.chainID();
+    }
+
+    function homeBridge(uint256 _disputeID) external view returns (address) {
+        return address(homeGateway);
+    }
+}