Bridge handshake protocol (#82)

Adds a handshake protocol that ensures no funds are lost when
depositing in the canonical bridge.

---------

Co-authored-by: K1-R1 <77465250+K1-R1@users.noreply.github.com>

.changeset/popular-feet-walk.md

@@ -0,0 +1,7 @@
+---
+'@fuel-bridge/solidity-contracts': minor
+'@fuel-bridge/fungible-token': minor
+'@fuel-bridge/test-utils': minor
+---
+
+Introduces a handshake protocol to avoid loss of funds while bridging assets from L1 to L2

docker/l1-chain/Dockerfile

@@ -16,6 +16,12 @@ WORKDIR /l1chain/fuel-v2-contracts
 
 # build the ethereum contracts and environment
 RUN pnpm install
+
+# Take advantage of cache by putting a placeholder and downloading the compiler
+ADD ./docker/l1-chain/Placeholder.sol /l1chain/fuel-v2-contracts/contracts/Placeholder.sol
+COPY ./docker/l1-chain/hardhat/hardhat.config.ts .
+RUN pnpm compile
+
 # replace the fuel chain consts values and change contract code
 ADD ./docker/l1-chain/.fuelChainConsts.env /l1chain/fuel-v2-contracts/.fuelChainConsts.env
 ADD ./packages/solidity-contracts/scripts/replaceFuelChainConsts.ts /l1chain/fuel-v2-contracts/scripts/replaceFuelChainConsts.ts
@@ -27,7 +33,6 @@ RUN pnpm ts-node scripts/replaceFuelChainConsts.ts
 
 # remove build dependencies
 # RUN pnpm prune --prod
-COPY ./docker/l1-chain/hardhat/hardhat.config.ts .
 RUN pnpm compile
 
 # Create deployments dir

docker/l1-chain/Placeholder.sol

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.0;
+
+/// @dev The only purpose of this contract is to be copied during the Dockerfile build
+///         so that hardhat downloads the compiler and it gets cached
+contract Placeholder {}

packages/fungible-token/bridge-fungible-token/src/interface/bridge.sw

@@ -38,4 +38,8 @@ abi Bridge {
     // Recovers the sub_id used to generate an asset_id (= sha256(contract_id, sub_id))
     #[storage(read)]
     fn asset_to_sub_id(asset_id: b256) -> b256;
+
+    /// Sends a message to the L1 gateway to inform of capabilities to receive funds
+    #[storage(read)]
+    fn register_bridge();
 }

packages/fungible-token/bridge-fungible-token/src/main.sw

@@ -33,7 +33,12 @@ use std::{
     },
     u256::U256,
 };
-use utils::{adjust_deposit_decimals, adjust_withdrawal_decimals, encode_data};
+use utils::{
+    adjust_deposit_decimals,
+    adjust_withdrawal_decimals,
+    encode_data,
+    encode_register_calldata,
+};
 
 configurable {
     DECIMALS: u8 = 9u8,
@@ -126,6 +131,11 @@ impl MessageReceiver for Contract {
 }
 
 impl Bridge for Contract {
+    #[storage(read)]
+    fn register_bridge() {
+        send_message(BRIDGED_TOKEN_GATEWAY, encode_register_calldata(BRIDGED_TOKEN), 0);
+    }
+
     #[storage(read, write)]
     fn claim_refund(from: b256, token_address: b256, token_id: b256) {
         let asset = sha256((token_address, token_id));

packages/fungible-token/bridge-fungible-token/src/utils.sw

@@ -100,6 +100,21 @@ pub fn encode_data(to: b256, amount: b256, bridged_token: b256, token_id: b256)
     data
 }
 
+pub fn encode_register_calldata(bridged_token: b256) -> Bytes {
+    let mut data = Bytes::with_capacity(36);
+
+    // First 4 bytes are funcSig: aec97dc6  =>  registerAsReceiver(address)  
+    data.push(0xaeu8);
+    data.push(0xc9u8);
+    data.push(0x7du8);
+    data.push(0xc6u8);
+
+    // Now the parameters
+    data.append(Bytes::from(bridged_token));
+
+    data
+}
+
 fn shift_decimals_left(bn: U256, decimals: u8) -> Result<U256, BridgeFungibleTokenError> {
     let mut bn_clone = bn;
     let mut decimals_to_shift = asm(r1: decimals) { r1: u64 };

packages/solidity-contracts/contracts/messaging/FuelMessagesEnabled.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.9;
 
 import {FuelMessagePortal} from "../fuelchain/FuelMessagePortal.sol";

packages/solidity-contracts/contracts/messaging/FuelMessagesEnabledUpgradeable.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.9;
 
 import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";

packages/solidity-contracts/contracts/messaging/gateway/FuelBridgeBase.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.9;
 
 abstract contract FuelBridgeBase {

packages/solidity-contracts/contracts/messaging/gateway/FuelERC20Gateway.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.9;
 
 import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
@@ -54,7 +54,7 @@ contract FuelERC20Gateway is
     /////////////
 
     /// @notice Maps ERC20 tokens to Fuel tokens to balance of the ERC20 tokens deposited
-    mapping(address => mapping(bytes32 => uint256)) private _deposits;
+    mapping(address => mapping(bytes32 => uint256)) internal _deposits;
 
     /////////////////////////////
     // Constructor/Initializer //
@@ -101,7 +101,7 @@ contract FuelERC20Gateway is
     /// @param tokenAddress ERC-20 token address
     /// @param fuelContractId ID of the corresponding token on Fuel
     /// @return amount of tokens deposited
-    function tokensDeposited(address tokenAddress, bytes32 fuelContractId) public view returns (uint256) {
+    function tokensDeposited(address tokenAddress, bytes32 fuelContractId) public view virtual returns (uint256) {
         return _deposits[tokenAddress][fuelContractId];
     }
 
@@ -116,7 +116,7 @@ contract FuelERC20Gateway is
         address tokenAddress,
         bytes32 fuelContractId,
         uint256 amount
-    ) external payable whenNotPaused {
+    ) external virtual payable whenNotPaused {
         bytes memory messageData = abi.encodePacked(
             fuelContractId,
             bytes32(uint256(uint160(tokenAddress))), // OFFSET_TOKEN_ADDRESS = 32
@@ -141,7 +141,7 @@ contract FuelERC20Gateway is
         bytes32 fuelContractId,
         uint256 amount,
         bytes calldata data
-    ) external payable whenNotPaused {
+    ) external virtual payable whenNotPaused {
         bytes memory messageData = abi.encodePacked(
                 fuelContractId,
                 bytes32(uint256(uint160(tokenAddress))), // OFFSET_TOKEN_ADDRESS = 32
@@ -181,7 +181,7 @@ contract FuelERC20Gateway is
 
     /// @notice Allows the admin to rescue ETH sent to this contract by accident
     /// @dev Made payable to reduce gas costs
-    function rescueETH() external payable onlyRole(DEFAULT_ADMIN_ROLE) {
+    function rescueETH() external virtual payable onlyRole(DEFAULT_ADMIN_ROLE) {
         (bool success, ) = address(msg.sender).call{value: address(this).balance}("");
         require(success);
     }
@@ -195,7 +195,7 @@ contract FuelERC20Gateway is
     /// @param fuelContractId ID of the contract on Fuel that manages the deposited tokens
     /// @param amount Amount of tokens to deposit
     /// @param messageData The data of the message to send for deposit
-    function _deposit(address tokenAddress, bytes32 fuelContractId, uint256 amount, bytes memory messageData) private {
+    function _deposit(address tokenAddress, bytes32 fuelContractId, uint256 amount, bytes memory messageData) internal virtual {
         require(amount > 0, "Cannot deposit zero");
 
         //transfer tokens to this contract and update deposit balance

packages/solidity-contracts/contracts/messaging/gateway/FuelERC721Gateway.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.9;
 
 import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
@@ -58,7 +58,7 @@ contract FuelERC721Gateway is
     /////////////
 
     /// @notice Maps ERC721 tokens to its fuel bridge counterpart
-    mapping(address => mapping(uint256 => bytes32)) private _deposits;
+    mapping(address => mapping(uint256 => bytes32)) internal _deposits;
 
     /////////////////////////////
     // Constructor/Initializer //
@@ -190,7 +190,7 @@ contract FuelERC721Gateway is
     /// @param fuelContractId ID of the contract on Fuel that manages the deposited tokens
     /// @param tokenId tokenId to deposit
     /// @param messageData The data of the message to send for deposit
-    function _deposit(address tokenAddress, bytes32 fuelContractId, uint256 tokenId, bytes memory messageData) private {
+    function _deposit(address tokenAddress, bytes32 fuelContractId, uint256 tokenId, bytes memory messageData) internal virtual {
         // TODO: this check might be unnecessary. If the token is conformant to ERC721
         // it should not be possible to deposit the same token again
         require(_deposits[tokenAddress][tokenId] == 0, "tokenId is already owned by another fuel bridge");

packages/solidity-contracts/contracts/messaging/gateway/v2/FuelBridgeBaseV2.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.9;
+
+abstract contract FuelBridgeBaseV2 {
+    error FuelContractIsNotBridge();
+
+    event ReceiverRegistered(
+        bytes32 indexed fuelContractId,
+        address indexed tokenAddress
+    );
+
+    mapping(bytes32 => mapping(address => bool)) public isBridge;
+
+    /// @notice Accepts a message from a fuel entity to acknowledge it can receive tokens
+    /// @param tokenAddress The token address that the fuel entity can receive
+    /// @dev Made payable to reduce gas costs
+    /// @dev funcSig: aec97dc6  =>  registerAsReceiver(address)  
+    function registerAsReceiver(address tokenAddress) external payable virtual;
+
+    /**
+     * @dev This empty reserved space is put in place to allow future versions to add new
+     * variables without shifting down storage in the inheritance chain.
+     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
+     */
+    uint256[49] private __gap;
+}

packages/solidity-contracts/contracts/messaging/gateway/v2/FuelERC20GatewayV2.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.9;
+
+import '../FuelERC20Gateway.sol';
+import './FuelBridgeBaseV2.sol';
+
+contract FuelERC20GatewayV2 is FuelERC20Gateway, FuelBridgeBaseV2 {
+    using SafeERC20Upgradeable for IERC20Upgradeable;
+
+    function registerAsReceiver(address tokenAddress) external payable virtual override onlyFromPortal() {
+        bytes32 sender = messageSender();
+
+        isBridge[sender][tokenAddress] = true;
+
+        emit ReceiverRegistered(sender, tokenAddress);
+    }
+
+    /// @notice Deposits the given tokens to an account or contract on Fuel
+    /// @param tokenAddress Address of the token being transferred to Fuel
+    /// @param fuelContractId ID of the contract on Fuel that manages the deposited tokens
+    /// @param amount Amount of tokens to deposit
+    /// @param messageData The data of the message to send for deposit
+    function _deposit(address tokenAddress, bytes32 fuelContractId, uint256 amount, bytes memory messageData) internal virtual override {
+        require(amount > 0, "Cannot deposit zero");
+        if (!isBridge[fuelContractId][tokenAddress]) revert FuelContractIsNotBridge();
+
+        //transfer tokens to this contract and update deposit balance
+        IERC20Upgradeable(tokenAddress).safeTransferFrom(msg.sender, address(this), amount);
+        _deposits[tokenAddress][fuelContractId] = _deposits[tokenAddress][fuelContractId] + amount;
+
+        //send message to gateway on Fuel to finalize the deposit
+        sendMessage(CommonPredicates.CONTRACT_MESSAGE_PREDICATE, messageData);
+
+        //emit event for successful token deposit
+        emit Deposit(bytes32(uint256(uint160(msg.sender))), tokenAddress, fuelContractId, amount);
+    }
+
+    /**
+     * @dev This empty reserved space is put in place to allow future versions to add new
+     * variables without shifting down storage in the inheritance chain.
+     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
+     */
+    uint256[49] private __gap;
+}

packages/solidity-contracts/contracts/messaging/gateway/v2/FuelERC721GatewayV2.sol

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.9;
+
+import '../FuelERC721Gateway.sol';
+import './FuelBridgeBaseV2.sol';
+
+contract FuelERC721GatewayV2 is FuelERC721Gateway, FuelBridgeBaseV2 {
+    function registerAsReceiver(address tokenAddress) external payable virtual override onlyFromPortal() {
+        bytes32 sender = messageSender();
+
+        isBridge[sender][tokenAddress] = true;
+
+        emit ReceiverRegistered(sender, tokenAddress);
+    }
+
+    /// @notice Deposits the given tokens to an account or contract on Fuel
+    /// @param tokenAddress Address of the token being transferred to Fuel
+    /// @param fuelContractId ID of the contract on Fuel that manages the deposited tokens
+    /// @param tokenId tokenId to deposit
+    /// @param messageData The data of the message to send for deposit
+    function _deposit(
+        address tokenAddress, 
+        bytes32 fuelContractId, 
+        uint256 tokenId, 
+        bytes memory messageData
+    ) internal virtual override {
+        // TODO: this check might be unnecessary. If the token is conformant to ERC721
+        // it should not be possible to deposit the same token again
+        require(_deposits[tokenAddress][tokenId] == 0, "tokenId is already owned by another fuel bridge");
+        if (!isBridge[fuelContractId][tokenAddress]) revert FuelContractIsNotBridge();
+
+        _deposits[tokenAddress][tokenId] = fuelContractId;
+
+        //send message to gateway on Fuel to finalize the deposit
+        sendMessage(CommonPredicates.CONTRACT_MESSAGE_PREDICATE, messageData);
+
+        IERC721Upgradeable(tokenAddress).transferFrom(msg.sender, address(this), tokenId);
+        //emit event for successful token deposit
+        emit Deposit(bytes32(uint256(uint160(msg.sender))), tokenAddress, fuelContractId, tokenId);
+    }
+
+    /**
+     * @dev This empty reserved space is put in place to allow future versions to add new
+     * variables without shifting down storage in the inheritance chain.
+     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
+     */
+    uint256[49] private __gap;
+}

packages/solidity-contracts/protocol/harness.ts

@@ -159,7 +159,7 @@ export async function deployFuel(
 
   // Deploy gateway contract for ERC20 bridging
   const FuelERC20Gateway = await ethers.getContractFactory(
-    'FuelERC20Gateway',
+    'FuelERC20GatewayV2',
     deployer
   );
   const fuelERC20Gateway = (await upgrades.deployProxy(
@@ -173,7 +173,7 @@ export async function deployFuel(
 
   // Deploy gateway contract for ERC721 bridging
   const FuelERC721Gateway = await ethers.getContractFactory(
-    'FuelERC721Gateway',
+    'FuelERC721GatewayV2',
     deployer
   );
   const fuelERC721Gateway = (await upgrades.deployProxy(