How to use function modifier to control contract function access right?

Question

I deployed a ERC20Mintable token in truffle environment(the source file is ERC20Mintable.sol).

The mint function is declared with onlyMinter modifer:

contract ERC20Mintable is ERC20, MinterRole {
    function mint(address account, uint256 amount) public onlyMinter returns (bool) {
        _mint(account, amount);
        return true;
    }
}

Minter role info is:

truffle(develop)> instance.isMinter(accounts[0])
true
truffle(develop)> instance.isMinter(accounts[1])
false
truffle(develop)> instance.isMinter(accounts[2])
false
truffle(develop)> instance.isMinter(accounts[3])
false

However,when I try to mint token, I found the modifier can not take effect to control the function call right:

For the first account:

truffle(develop)> instance.mint(accounts[0],1000)
{ tx:
   '0x323ff19c7b79cbe545914465c9bda87aa5169cdaa3be6f4ccbebcd7e7eb76617',
  receipt:
   { transactionHash:
    ...
truffle(develop)> instance.totalSupply()
<BN: 3e8>//1000

For the second account:

truffle(develop)> instance.mint(accounts[1],1000)
{ tx:
   '0xc13da9ca6ba8b74e998b4b158eb1be02208e2bc8f08c789f4a6a306bedadc7a1',
  receipt:
   { transactionHash:
truffle(develop)> instance.totalSupply()
<BN: 7d0>//2000
truffle(develop)> instance.balanceOf(accounts[0])
<BN: 3e8>//1000
truffle(develop)> instance.balanceOf(accounts[1])
<BN: 3e8>//1000
truffle(develop)> instance.balanceOf(accounts[2])
<BN: 0>

From the result, every account is able to mint token, onlyMinter has no capability to control function call role.

How can I fix the problem? Thanks.

Answer 1

To manually test the MinterRole you need to change the account you are sending the transaction from. e.g. accounts[0] has the MinterRole, accounts[1] does not have the MinterRole so reverts when you attempt to mint.

truffle(develop)> accounts = await web3.eth.getAccounts()
truffle(develop)> token.mint(accounts[9], "10000000000000000000", {from:accounts[0]})
{ tx: ....
truffle(develop)> token.mint(accounts[9], "10000000000000000000", {from:accounts[1]})
Thrown:
{ Error: Returned error: VM Exception while processing transaction: revert MinterRole: caller does not have the Minter role -- Reason given: MinterRole: caller does not have the Minter role.

OpenZeppelin documentation has a guide on tokens: https://docs.openzeppelin.org/v2.3.0/tokens

If you have questions about using OpenZeppelin you can also ask questions in the community forum: https://forum.zeppelin.solutions