Owner Renouncing Ownership Without Transfer

Description

The renounceOwnership() function in the contract allows the owner to renounce their ownership of the contract without assigning a new owner. This can be a security issue, as it means that the contract may be left without an owner or control in case of a compromise of the owner's account or key.

Example Code

Here's an example of the renounceOwnership() function:

function renounceOwnership() public virtual onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
}

Recommendation

To mitigate this issue, it's recommended to either implement a two-factor authentication process for transferring ownership or to modify the renounceOwnership() function to overwrite it so that it's not possible to call it directly. This could be done by removing the function or implementing a check that prevents it from being called if there are no other owners designated.

Two Factor Authentication Example

In this example, the owner must specify a new owner address and the new owner must confirm the ownership transfer before the transfer can occur. This ensures that ownership can only be transferred with the approval of both the current and new owners.

pragma solidity ^0.8.0;

contract TwoFactorAuthOwnership {
    address public owner;
    address public proposal;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() {
        owner = msg.sender;
    }

    function transferOwnership(address _newOwner) public {
        require(_newOwner != address(0), "Invalid new owner address");
        require(msg.sender == owner, "Only the owner can transfer ownership");

        proposal = _newOwner;
    }

    function confirmOwnershipTransfer() public {
        require(msg.sender == proposal, "Only the new owner can confirm ownership transfer");

        // Emit ownership transfer event
        emit OwnershipTransferred(owner, proposal);

        // Set new owner
        owner = proposal;
    }
}

Overwriting renonuceOwnership() Example

In this example, the renounceOwnership() function is overwritten to prevent the owner from renouncing ownership without transferring ownership to a new address.

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

contract NoRenounceOwnership is Ownable {
    address public newOwner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function renounceOwnership() public override onlyOwner {
        revert("Ownership cannot be renounced, please transfer ownership to a new address.");
    }
}