Dandy Caramel Tortoise - Tokens that revert of zero value transfers can cause reverts on liquidation

[sherlock-admin4]

Dandy Caramel Tortoise

Medium

Tokens that revert of zero value transfers can cause reverts on liquidation

Summary

Tokens that revert of zero value transfers can cause reverts on liquidation

Root Cause

In the readme the team has mentioned that they would like to know if any wierd token breaks their contract pools

In multiple places token amount which can become zero is transferred without checking the value is zero. This will cause these transactions to revert
https://github.com/sherlock-audit/2024-11-teller-finance-update/blob/0c8535728f97d37a4052d2a25909d28db886a422/teller-protocol-v2-audit-2024/packages/contracts/contracts/LenderCommitmentForwarder/extensions/LenderCommitmentGroup/LenderCommitmentGroup_Smart.sol#L699-L727

            IERC20(principalToken).safeTransferFrom(
                msg.sender,
                address(this),
                amountDue + tokensToTakeFromSender - liquidationProtocolFee
            ); 
             
            address protocolFeeRecipient = ITellerV2(address(TELLER_V2)).getProtocolFeeRecipient();


              IERC20(principalToken).safeTransferFrom(
                msg.sender,
                address(protocolFeeRecipient),
                 liquidationProtocolFee
            );


            totalPrincipalTokensRepaid += amountDue;
            tokenDifferenceFromLiquidations += int256(tokensToTakeFromSender - liquidationProtocolFee );

        } else {

            uint256 tokensToGiveToSender = abs(minAmountDifference);


           
            IERC20(principalToken).safeTransferFrom(
                msg.sender,
                address(this),
                amountDue - tokensToGiveToSender  
            );

Internal pre-conditions

No response

External pre-conditions

No response

Attack Path

No response

Impact

In case liquidation reverts (due to tokensToGiveToSender == -amountDue), the tokenDifferenceFromLiquidations won't be updated which will cause the value of the shares to be incorrectly high (because in reality the auction is settling at 0 price)

PoC

No response

Mitigation

Check if amount is non-zero before transferring

[sherlock-admin2]

The protocol team fixed this issue in the following PRs/commits:
teller-protocol/teller-protocol-v2-audit-2024#82