Token Manual Review Findings

TNE-01M: Potentially Invalidated Assumption

Type	Severity	Location
Mathematical Operations		Token.sol:L78-L79

Description:

The Token::distributeTo function assumes that the _distribution being processed is composed of recipients that are not equal to the contract the code is being executed on, however, this is not guaranteed.

Impact:

The Token::distributeTo function performs an unchecked subtraction on the _amountLeft value that may overflow if a distribution recipient is the logic contact itself given that the balance will remain available for the next distribution.

Example:

Copy
63function distributeTo(
64  address _token,
65  DistributionTarget[] calldata _distribution
66)
67  internal
68  returns (uint256 _available)
69{
70  _available = balanceOnContract(_token);
71  uint256 _amountLeft = _available;
72
73  // Distribute amounts
74  for (uint256 i; i < _distribution.length - 1;) {
75    uint256 _toSend = _available * _distribution[i].shareBps / 10_000;
76    sendAmountTo(_token, _toSend, _distribution[i].recipient);
77    unchecked {
78      // We know that _toSend <= _amountLeft because if it wasn't, sendAmountTo would have reverted
79      _amountLeft -= _toSend;
80      ++i;
81    }
82  }
83
84  // Send amount left to the last recipient
85  sendAmountTo(_token, _amountLeft, _distribution[_distribution.length - 1].recipient);
86}

Recommendation:

We advise the code to perform the _amountLeft subtraction using checked arithmetics as the gas cost is minimal and protects against multiple types of exploits, including self-transfers (that can thus exceed the 10_000 BPS number and still succeed) as well as potential re-entrancy attack vectors that take advantage of that.

Alleviation:

The Mean Finance team evaluated this exhibit and relocated the _amountLeft subtraction outside the unchecked code block, ensuring that the edge-case condition referenced here will fail with a clearer error.