[Ethereum] Minting Tokens and OnlyOwner – ERC20

erc-20presalesolidity

I have created a contract based on a standard one to mint and I have code as follows – 

  modifier canMint() {
    require(!mintingFinished);
    _;
  }

  /**
   * Function to mint tokens
   * @param _to The address that will recieve the minted tokens.
   * @param _amount The amount of tokens to mint.
   * @return A boolean that indicates if the operation was successful.
   */
  function mint(address _to, uint256 _amount) onlyOwner canMint returns (bool) {
    totalSupply = totalSupply.add(_amount);
    balances[_to] = balances[_to].add(_amount);
    Mint(_to, _amount);
    return true;
  }

  /**
   * Function to stop minting new tokens.
   * @return True if the operation was successful.
   */
  function finishMinting() onlyOwner returns (bool) {
    mintingFinished = true;
    MintFinished();
    return true;
  }

I understand intuitively what onlyOwner means but how is this actually enforced in practice to prevent anyone just minting coins?

I intend to deploy via myetherwallet. So I would have whatever credentials and available via that system.

Once I deployed via myetherwallet, then I need to somehow run the contract. Usually in test I use geth but for the full ethereum system I cannot do that.

So how would I actually run the finishMinting etc? Is there a command line option for production Ethereum, or do I need a Web3 interface in React or something like that, and then how would I confirm I am the onlyowner?

Best Answer

If you have taken the contracts from Zeppelin Solidity, then there should be a contract called Ownable. In that contract there is a modifier called onlyOwner and the contract should look something like:

address public owner;

function Ownable() public {
   owner = msg.sender; //ownership is assigned to the address used to deploy contract

}

modifier onlyOwner {
    require(owner == msg.sender); //if msg.sender != owner, then mint function will fail to execute.
    _;
}

You will notice that onlyOwner is in the 'mint' function signature. The modifier is there to check that the msg.sender is the owner before executing any of the function's body.

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