Airdopped tokens can be stolen by anyone

Summary

lzReceive function inside TOFT, mTOFT and USDO contracts can be used to airdrop tokens to the contract. These tokens can be stolen by anyone.

Vulnerability Detail

Cross-chain receiving logic inside TOFT, mTOFT and USDO is split between lzReceive and lzCompose functions.

lzReceive handles the crediting of tokens and invoking the lzEndpoint.sendCompose so the rest of the cross-chain flow can be executed inside the lzCompose function.

lzCompose in the context of the above-mentioned contracts handles many flows, some of which require the user to airdrop a certain amount of tokens so a specific action can be executed. An example is withdrawing assets to another chain.

If we check the LayerZero option types it is only possible to airdrop tokens as part of the lzReceive and not the lzCompose function call: https://docs.layerzero.network/contracts/options#lzcompose-option

This means that the airdropped tokens will be sitting in the TOFT contract for example in between the two calls.

This is a problem as some other user can directly use these gas tokens to pay for his LayerZero fees, effectively stealing the airdropped tokens.

Impact

Any airdropped tokens as part of the lzReceive function call can be stolen by anyone.

Code Snippet

https://github.com/sherlock-audit/2024-02-tapioca/blob/dc2464f420927409a67763de6ec60fe5c028ab0e/TapiocaZ/contracts/tOFT/TOFT.sol#L168

Tool used

Manual Review

Recommendation

Disallow airdropping tokens as part of the lzReceive function call. This can be done by checking the _extraOptions passed to the sendPacket function.

sherlock-audit / 2024-02-tapioca-judging

GiuseppeDeLaZara - Airdopped tokens can be stolen by anyone #80