Too much ETH in receiveTokenOrETH not reimbursed

[code423n4]

Lines of code

https://github.com/debtdao/Line-of-Credit/blob/d7ef66035ddf873b0c96804a1c9deeebb1f798ea/contracts/utils/LineLib.sol#L71

Vulnerability details

Impact

In LineLib.receiveTokenOrETH, it is only checked if msg.value is greater or equal than amount when the token is ETH:

if(msg.value < amount) { revert TransferFailed(); }

Therefore, when a user accidentally pays too much ETH, the additional amount will be lost. Note that this is different to ERC20 tokens, where the exact amount is enforced (by transferring the exact amount).

Proof Of Concept

Alice calls LineOfCredit.addCredit to add a credit with 1 ETH. While amount is set to 1 ETH (10**18), she accidentally sends 2 ETH with the call. The additional ETH is lost and cannot be recovered.

Recommended Mitigation Steps

Either force that the amount matches exactly or reimburse the additional ETH.

[c4-judge]

dmvt marked the issue as duplicate of #25

[c4-judge]

dmvt marked the issue as satisfactory

[C4-Staff]

liveactionllama marked the issue as duplicate of #39