Tadle

Github

• https://github.com/Cyfrin/2024-08-tadle/blob/04fd8634701697184a3f3a5558b41c109866e5f8/src/core/TokenManager.sol#L233

Summary

The _transfer function in the TokenManager contract encounters issues when dealing with ERC20 tokens that have a fee on transfer. The function assumes that the amount specified for transfer is exactly what will be received, which may not hold true if the token imposes a transfer fee. This discrepancy can lead to unexpected behavior and failed transactions.

Vulnerability Details

The _transfer function checks the token balances before and after the transfer to validate the success of the operation. However, this approach assumes that the amount of tokens sent is the same as the amount received. For tokens with a fee on transfer, the amount received by the destination address will be less than the amount sent. This discrepancy can cause the function to revert due to the failed balance checks.

Impact

The function may incorrectly revert transactions if the token implements a fee on transfer, causing DOS in operations that rely on this function. Users might lose tokens due to failed transfers or incorrect calculations if the function does not account for transfer fees.

Tools Used

Manual Review

Recommendations

Modify the _transfer function to account for the potential fee deducted during the transfer. Instead of comparing exact amounts, allow for a small tolerance to accommodate fees.