CreditLine.sol assumes 365 day year

[code423n4]

Handle

sirhashalot

Vulnerability details

Impact

CreditLine.sol assumes a year is 365 days with the YEAR_IN_SECONDS constant, but this is not always true. This assumption impacts the calculateInterest function and will more interest than it should during leap years (roughly 1 / 365 = 0.274% more). Solidity documentation warns against assuming a year is 365 days, and the years suffix was removed for this reason from Solidity 0.5.0.

Proof of Concept

CreditLine.sol
https://github.com/code-423n4/2021-12-sublime/blob/9df1b7c4247f8631647c7627a8da9bdc16db8b11/contracts/CreditLine/CreditLine.sol

Recommended Mitigation Steps

Handle leap year edge case in calculateInterest function to improve interest calculation accuracy

[ritik99]

We're aware that 365 days doesn't hold true for every year but we'll be retaining this assumption to simplify calculations