nikhilx0111 - incorrect assumption can be problematic

[sherlock-admin4]

nikhilx0111

High

incorrect assumption can be problematic

Summary

This part of the code is inside the swap function, which is responsible for handling both DeFi and stablecoin swaps.

            uint256 iBalance = ERC20(ss.origin).balanceOf(wallet);
            if (defi.walletData.length != 0) _defiSwap(wallet, defi);
            uint256 fBalance = ERC20(ss.origin).balanceOf(wallet);
            //change balance to reflect change
            if (fBalance - iBalance != 0) ss.oAmount = fBalance - iBalance;

this line captures the initial balance of the user's ss.origin token (the token the user is going to swap from) before any operation happens. It does this by calling the balanceOf function

        if (defi.walletData.length != 0) _defiSwap(wallet, defi);

If there is a DeFi swap, the function _defiSwap(wallet, defi) is called

        uint256 fBalance = ERC20(ss.origin).balanceOf(wallet);

After performing the DeFi swap this line captures the final balance of ss.origin token after the swap. The idea is to check how the balance has changed as a result of the operation

        if (fBalance - iBalance != 0) ss.oAmount = fBalance - iBalance;

This line calculates the difference between the final balance (fBalance) and the initial balance (iBalance). This difference represents the amount of tokens spent or received due to the DeFi swap

         if (fBalance - iBalance != 0) ss.oAmount = fBalance - iBalance;

If the balance has changed (i.e., fBalance - iBalance != 0), it adjusts the amount. The oAmount represents the current balance of the wallet however the code assumes that fbalance (received amount) which can be wronf and if the initial balance every exceeds this code will fail to capture the users balance

Root Cause

https://github.com/sherlock-audit/2024-11-telcoin/blob/b9c751b59e78a7123a636e31ecafc9147046f190/telcoin-audit/contracts/swap/AmirX.sol#L93

Internal pre-conditions

balance exceeds received amount

External pre-conditions

No response

Attack Path

No response

Impact

loss of funds for users if balance ever exceeds received amount as the code will fail to capture the latest balance

PoC

No response

Mitigation

remove the check check if the amount received is more than initial balance