In this project, the burnt token would not be transferred to the "burn" address.

Burnt token not transferred to the "burn" address 

Some `public` functions are never called by the contract. For example: 

``` solidity 
	function transfer(address to, uint256 value) public returns (bool)
	function approve(address spender, uint256 amount) public returns (bool)
	function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) 
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool)
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool)
```


Public functions could be declared external 

The aforementioned lines perform a low level call to execute transactions but the return value is not checked in either case.

Unchecked Value of low-level Call

In the contract `Pausable`, the role `owner` has the authority which a hacker could use to take control of the contract. Once a hacker takes an owner account, he could take control with the following steps:

1. List all owner accounts by `OwnerRole.owners()`, and use `OwnerRole.removeOwner()` to remove other owners
2. Use `PauserAdminRole.replaceAllPauserAdmins()` to replace all current PauserAdmin accounts of PauserAdminRole and grant PauserAdminRole to himself
3. Use PauserAdminRole to deprive all Pause & Unpause accounts of PauseRole or UnpauseRole by `PauseRole.replaceAllPausers()` &  `UnpauseRole.replaceAllUnpausers()`
4. The hacker takes the only owner and control all transactions with pause() & unpause()





```solidity = 
    /**
     * @dev Pauses by setting `_paused` to true, to trigger stopped state.
     * Callable by an account with the pauser role, or an account with the owner role.
     */
    function pause() external onlyPauserOrOwner whenNotPaused {
        _paused = true;
        emit Paused(msg.sender);
    }

    /**
     * @dev Unpauses by setting `_paused` to false, to return to normal state.
     * Callable by an account with the unpauser role, or an account with the owner role.
     */
    function unpause() external onlyUnpauserOrOwner whenPaused {
        _paused = false;
        emit Unpaused(msg.sender);
    }
```

The overly powerful owner is a centralization risk as he can perform actions without obtaining the consensus of the community. The linked functions allow the owner to pause/unpause all transfers of tokens.

Centralization Risk

The `approve` function could be used in an attack that allows a spender to transfer more tokens than the owner of the tokens ever wanted to allow the spender to transfer.

Here is a possible attack scenario:
Alice allows Bob to transfer N of Alice's tokens (N>0)  by calling approve method on Token smart contract passing Bob's address and N as method arguments After some time, Alice decides to change from N to M (M>0) the number of Alice's tokens Bob is allowed to transfer, so she calls approve method again, this time passing Bob's address and M as method arguments Bob notices Alice's second transaction before it was mined and quickly sends another transaction that calls ·transferFrom· method to transfer N Alice's tokens somewhere If Bob's transaction will be executed before Alice's transaction, then Bob will successfully transfer N Alice's tokens and will gain the ability to transfer another M tokens Before Alice noticed that something went wrong, Bob calls ·transferFrom· method again, this time to transfer M Alice's tokens.

So, Alice's attempt to change Bob's allowance from N to M (N>0 and M>0) made it possible for Bob to transfer N+M of Alice's tokens, while Alice never wanted to allow so many of her tokens to be transferred by Bob.

ERC20 API: An Attack Vector on Approve/TransferFrom Methods
https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/edit#heading=h.m9fhqynw2xvt

Potential Risks on Approval/TransferFrom Methods

In the contract `OwnerRole`, the role `Owner` has the authority over the following functions:
- function owners() external view returns (address[]) 
- function removeOwner(address account) external onlyOwner

Any compromise to the `Owner` account may allow the hacker to take centralized control of this contract via: 
1. list all owners by owners() 
2.  remove other owners by  `removeOwner`(address account)

We advise the client to carefully manage the owner account's private key to avoid any potential risks of being hacked.
In general, we strongly recommend centralized privileges or roles in the protocol to be improved via a decentralized mechanism or smart-contract-based accounts with enhanced security practices, e.g., Multisignature wallets. 


In the contract `RewardStation`, only the role `Admin` has the authority of function `pause()` & `unpause()`. 



```solidity = 
    /**
     * @notice Triggers stopped state
     * @dev Only possible when contract not paused.
     */
    function pause() external onlyAdmin whenNotPaused {
        _pause();
        emit Pause();
    }

    /**
     * @notice Returns to normal state
     * @dev Only possible when contract is paused.
     */
    function unpause() external onlyAdmin whenPaused {
        _unpause();
        emit Unpause();
    }
```

The overly powerful owner is a centralization risk as he can perform actions without obtaining the consensus of the community. The linked functions allow the owner to pause/unpause all transfers of tokens.

In functions `claim` and `claimWithReferral`, the contract allows users to claim a specific amount of token with an admin signed message via ECDSA.

As the specification of ECDSA, the signature of message M is combined with (r,s)
```language=python
	r = k * G
	s = ( hash(M) + r * private_key ) / k
```
So we could find, as hacker could get one transaction's signature (r,s) and its hash message hash(M):
```language=python
	private_key = ( s * k - hash(M) ) / r
```
The only unknown value is the random k, the private_key would be easily recovered by hacker via:

1. When the k is revealed
2. Find two signatures that have the same r, to recover the private key by this formula:

```language=python
	private_key = ( hash(M_1)*s1 - hash(M_2)*s2 ) / r * (s1 - s2)
```

We suggest restricting the visibility of the hash assembly method `hashFun` to avoid the hacker to recover the private key with it.


ECDSA Signature Private Key Reveal Risk

When user is rewarded , `lastRewardedTime` is not updated as well as function `reward`, `claim`, `claimWithReferral`. 

lastRewardedTime is not updated in function rewardWithRefferal

The following functions are declared as `public`, contain array function arguments, and are not invoked in any of the contracts contained within the project's scope. The functions that are never called internally within the contract should have external visibility.
```language=solidity
	function reward(address _addr) public notContract onlyAdmin 
	function rewardWithReferral(address _addr, address _referral) public notContract onlyAdmin 
	function claim(uint256 _rewardsAmount, uint256 nonce, bytes memory sig) public notContract 
	function claimWithReferral(uint256 _rewardsAmount, uint256 nonce, bytes memory sig,  address _referral) public notContract 
``` 

Function Visibility Optimization

Frac property

math

ERC20.sol

UnpauserRole.sol

access

Roles.sol

utils

Burnable.sol

IERC20.sol

TokenImpl_metadata.json

artifacts

PauserAdminRole.sol

Proxy.sol

roles

AdminUpgradeabilityProxy.sol

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TokenImpl.sol

reward

MinterAdminRole.sol

TokenImpl.json

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RewardStation.sol

token

ListerAdminRole.sol

storage

Blacklistable.sol

PauserRole.sol

AddressList.sol

AddressList_metadata.json

OwnerRole.sol

UpgradeabilityProxy.sol

MintLimiterAdminRole.sol

MinterRole.sol

Whitelistable.sol

Mintable.sol

MintLimiterRole.sol

AddressList.json

ListerRole.sol

SafeMath.sol

upgradeability

lifecycle

ECRecovery.sol

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