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sherlock-audit / 2024-02-smilee-finance-judging

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mgf15 - safeApprove could revert for non-standard token like USDT #145

Closed sherlock-admin3 closed 8 months ago

sherlock-admin3 commented 9 months ago

mgf15

medium

safeApprove could revert for non-standard token like USDT

Summary

Certain ERC20 token does not return bool from approve and transfer and transaction revert

Vulnerability Detail

Some non-standard tokens like USDT will revert when a contract or a user tries to approve an al- lowance when the spender allowance has already been set to a non zero value.

Impact

Some tokens do not return a bool on ERC20 methods and use IERC20 token interface will revert transaction

Code Snippet

https://github.com/sherlock-audit/2024-02-smilee-finance/blob/3241f1bf0c8e951a41dd2e51997f64ef3ec017bd/smilee-v2-contracts/src/providers/SwapAdapterRouter.sol#L161

Tool used

Manual Review

Recommendation

It is recommended to set the allowance to zero before increasing the allowance and use safeApprove/safeIncreaseAllowance.

sherlock-admin3 commented 8 months ago

2 comment(s) were left on this issue during the judging contest.

panprog commented:

invalid, full approved amount is transfered downstream in swapadapter, thus always resetting approval back to 0 at the end of the function

takarez commented:

valid; the ReadMe says there is a chance of addign another stable coins in the fututre, so this should be valid; medium(6)