Absolutely, your requirement is fully achievable! Let’s break down how to add the multi-signature approval flow to your withdraw function, plus explain why your current Gnosis Safe interaction is failing.

Why Your Current Gnosis Safe Interaction Fails #

Your existing withdraw function sends ETH directly to msg.sender (the account calling the function) as soon as a managerRole holder invokes it. When using Gnosis Safe here:

• msg.sender becomes the Gnosis Safe contract address, not your intended owner wallet, which breaks your target recipient logic.
• There’s no built-in approval check, so the transaction tries to execute immediately without meeting your 2/3 multi-sig requirement—leading to the "this transaction will fail" warning.

Step-by-Step Implementation #

We’ll split the withdraw process into three secure phases: initiate a request, collect approvals, and execute the transfer once 2/3 of the owner multisig members have signed off.

1. Add Core State Variables & Roles #

First, define structures to track requests and approvals, plus a dedicated role for your owner multisig members:

import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract YourContract is AccessControl, ReentrancyGuard {
    bytes32 public constant MANAGER_ROLE = keccak256("MANAGER_ROLE");
    bytes32 public constant OWNER_MULTISIG_ROLE = keccak256("OWNER_MULTISIG_ROLE");

    struct WithdrawRequest {
        address requester;
        uint256 amount;
        uint256 approvalCount;
        bool isExecuted;
        mapping(address => bool) hasApproved;
    }

    mapping(uint256 => WithdrawRequest) public withdrawRequests;
    uint256 public requestCounter;

    // Events for transparency on-chain
    event WithdrawRequestInitiated(uint256 requestId, address requester, uint256 amount);
    event WithdrawRequestApproved(uint256 requestId, address approver);
    event WithdrawExecuted(uint256 requestId, address recipient, uint256 amount);

    // Constructor - set initial admin/manager roles
    constructor() {
        _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
        // Add initial MANAGER_ROLE holders here if needed
    }
}

2. Replace Direct Withdraw with Request Initiation #

Instead of transferring ETH immediately, let managerRole holders create a pending withdraw request:

function initiateWithdraw() external onlyRole(MANAGER_ROLE) returns(uint256 requestId) {
    uint256 withdrawAmount = getBalance();
    require(withdrawAmount > 0, "No balance available to withdraw");

    requestId = requestCounter++;
    WithdrawRequest storage newRequest = withdrawRequests[requestId];
    newRequest.requester = msg.sender;
    newRequest.amount = withdrawAmount;
    newRequest.approvalCount = 0;
    newRequest.isExecuted = false;

    emit WithdrawRequestInitiated(requestId, msg.sender, withdrawAmount);
}

3. Add Approval Function for Multisig Members #

Only OWNER_MULTISIG_ROLE holders can approve pending requests:

function approveWithdraw(uint256 requestId) external onlyRole(OWNER_MULTISIG_ROLE) {
    WithdrawRequest storage request = withdrawRequests[requestId];
    
    require(!request.isExecuted, "Request has already been executed");
    require(!request.hasApproved[msg.sender], "You've already approved this request");

    request.hasApproved[msg.sender] = true;
    request.approvalCount++;

    emit WithdrawRequestApproved(requestId, msg.sender);
}

4. Add Executable Withdraw (After 2/3 Approvals) #

Once enough approvals are collected, anyone (or restricted roles) can trigger the ETH transfer to your owner wallet:

function executeWithdraw(uint256 requestId) external nonReentrant {
    WithdrawRequest storage request = withdrawRequests[requestId];
    
    require(!request.isExecuted, "Request has already been executed");
    require(address(this).balance >= request.amount, "Insufficient contract balance");

    // Calculate required approvals (2/3 of multisig members, rounded up for odd counts)
    uint256 totalMultisigMembers = getRoleMemberCount(OWNER_MULTISIG_ROLE);
    uint256 requiredApprovals = (totalMultisigMembers * 2) / 3;
    if ((totalMultisigMembers * 2) % 3 != 0) {
        requiredApprovals++;
    }

    require(request.approvalCount >= requiredApprovals, "Not enough approvals to execute");

    // Mark request as executed first to prevent reentrancy risks
    request.isExecuted = true;

    // Transfer ETH to your intended owner wallet (replace with your target address if needed)
    (bool sent, ) = payable(owner()).call{value: request.amount}("");
    require(sent, "Ether transfer failed");

    emit WithdrawExecuted(requestId, owner(), request.amount);
}

Gnosis Safe Integration Tips #

• Grant the OWNER_MULTISIG_ROLE to your Gnosis Safe contract address (not individual owners). This lets multi-sig transactions from the Safe count as valid approvals.
• Workflow for Gnosis Safe users:
  1. A managerRole holder initiates the withdraw request via a regular transaction.
  2. Gnosis Safe members create and approve a multi-sig transaction to call approveWithdraw for the request ID.
  3. Once enough approvals are collected, anyone can call executeWithdraw (this can also be done via a Gnosis Safe transaction for extra security).

Security Checks to Remember #

• Keep nonReentrant on executeWithdraw to block reentrancy attacks.
• Verify getBalance() correctly returns the contract’s available ETH (exclude any locked funds if applicable).
• Test with different multisig sizes (e.g., 3 members need 2 approvals, 5 need 4) to confirm the approval calculation works as intended.

内容的提问来源于stack exchange，提问作者Eniola Agboola