ArkProject: NFT Bridge

Summary

It is recommended to use safe_transfer_from instead of transfer_from when transferring ERC721s out of the bridge contract.

Vulnerability Details

In withdraw_auto_from_l1 the escrowed tokens are transfered using transfer_from. But it is better to use safe_transfer_from.
The recipient could have logic in the on_erc721_received function, which is only triggered in the safe_transfer_from function and not in transfer_from. It helps ensure that the recipient is indeed capable of handling ERC721s.

Additionally if req.owner_l2 address which is set while bridging from L1, is set to an contract which doesn't support ERC721, then NFTs might lost forever.
Using safe_transfer_from will ensure the handler reverts in such cases. Later the message can be cancelled to get the locked tokens on L1 side

Impact

NFTs might be lost forever and doesn't ensure recipient is capable of handling ERC721s.

Tools Used

Manual review

Recommendations

Use safe_transfer_from instead of transfer_from