Unveiling the Uniswap Permit2 Signature Eyewash

Hackers are a frightening presence in the Web3 ecosystem. For project teams, open-source code brings immense security pressure. For individual users, every on-chain interaction may carry risks. Recently, a new phishing method has become active, where just signing could lead to theft; the method is subtle and hard to defend against, and addresses that have used Uniswap may be exposed to risks.

Incident Details

Recently, a friend of mine ( Xiao A ) had his wallet assets stolen, but he did not disclose his private key or interact with any suspicious contracts. The investigation found that Xiao A's USDT was transferred using the Transfer From function, which means that a third party operated to transfer the assets.

Transaction Details:

• An address ending in fd51 transferred Xiaoa's assets to an address ending in a0c8.
• This operation interacts with the Permit2 contract of Uniswap.

The key question is: how did the address ending in fd51 obtain asset permissions? Why is it related to Uniswap?

Introduction to Uniswap Permit2 Contract

Uniswap Permit2 is a token approval contract that allows sharing and management of authorizations across different applications, providing a more unified, efficient, and secure user experience. It can reduce transaction costs, improve user experience, and enhance the security of smart contracts.

Permit2 acts as an intermediary between the user and the Dapp. Users only need to authorize the Permit2 contract, and all Dapps integrated with Permit2 can share this authorization limit. This reduces user interaction costs, but may also introduce new risks.

Fishing Technique Analysis

The key lies in the Permit function of the Permit2 contract. In simple terms, this function uses the user's signature to transfer the token allowance granted to Permit2 to another address. A hacker only needs to obtain the signature to transfer the user's assets.

Specific steps:

1. The user has authorized the Permit2 contract ( on Uniswap, usually with an unlimited limit ).
2. The user inadvertently signed a Permit2 signature constructed by hackers.
3. Hackers use signatures to execute Permit and Transfer From operations in the Permit2 contract.
4. User assets have been transferred

preventive measures

1. Learn to recognize the Permit signature format and use security plugins to assist with identification.
2. Use the storage wallet and the interactive wallet separately.
3. Limit the authorization amount to Permit2, or revoke the authorization.
4. Understand whether the tokens you hold support the permit function, and be especially cautious with related transactions.
5. In case of theft, quickly formulate a comprehensive asset recovery plan.

As the application of Permit2 expands, such phishing attacks may become more frequent. Users need to be vigilant and enhance their security awareness to protect their asset safety.