A loan with some special parameters may never be able to doing a periodic partial repayments

[c4-bot-8]

Lines of code

https://github.com/code-423n4/2023-12-ethereumcreditguild/blob/2376d9af792584e3d15ec9c32578daa33bb56b43/src/loan/LendingTerm.sol#L490-L559

Vulnerability details

Impact

A loan with some special parameters may never be able to doing a periodic partial repayments, and this loan will inevitably become bad debt for the system.

Proof of Concept

Suppose there is a lendingTerm in the system, which stipulates that the minimum amount a user can borrow in a single loan is 100 tokens, and the minimum partial repayment is 5%.(Assume that the impact of APR and openingFee is not considered for the time being)

1. User A creates a loan: borrowAmount=100.
2. When user A attempts to call the partialRepay function, he must repay at least 5 credit Tokens (100 * 5%). After repayment, user A's current loan amount is 95. Since 95 is less than 100, the minimum loan amount cannot be met, and user A's partial repayment operation fails.
3. In the partialRepay function of LendingTerm.sol, we can see a contradiction that prevents the following two conditions from being met simultaneously:

require(
    debtToRepay >= (loanDebt * params.minPartialRepayPercent) / 1e18,
    "LendingTerm: repay below min"
);
require(
    borrowAmount - issuanceDecrease >
        ProfitManager(refs.profitManager).minBorrow(),
    "LendingTerm: below min borrow"
);

Tools Used

Manual audit

Recommended Mitigation Steps

Suggested optimization statement:

	require(
	    debtToRepay >= (loanDebt * params.minPartialRepayPercent) / 1e18,
	    "LendingTerm: repay below min"
	);
-	require(
-	    borrowAmount - issuanceDecrease >
-	        ProfitManager(refs.profitManager).minBorrow(),
-	    "LendingTerm: below min borrow"
-	);

Assessed type

Other

[c4-pre-sort]

0xSorryNotSorry marked the issue as sufficient quality report

[c4-pre-sort]

0xSorryNotSorry marked the issue as duplicate of #1182

[c4-judge]

Trumpero changed the severity to QA (Quality Assurance)

[c4-judge]

Trumpero marked the issue as grade-b

[c4-judge]

Trumpero marked the issue as grade-c