ArkProject: NFT Bridge

Summary

The Bridge contract uses a whitelist to prevent bridging tokens, however this whitelist is not enforced whilst unbridging.

Vulnerability Details

The Bridge contract enables onlyOwner to whitelist specific token collections from being processed by the bridge.

However, this is only enforced on depositTokens and does not take effect on calls to withdrawTokens.

Consequently, malicious token collections that were bridged prior to the collection being blacklisted may continue to be transacted.

Impact

The bridge remains vulnerable to interacting with explicitly disabled (i.e. malicious) token collections.

Tools Used

Manual Review

Recommendations

Bridge.sol

When attempting to withdraw a token from escrow via the untrusted withdrawTokens function, validate the collectionL1 has been whitelisted.

We advise against enforcing these rules in the admin-controlled functions, since it can be left to the discretion of the admin to determine whether blacklisted token withdrawals via startRequestCancellation be permitted.

However, it may be advisable for the admin to explicitly acknowledge the potential interaction with a blacklisted token during cancellation using a force override.