[SDK] Securing Atomic Transactions on zkSync: Strategies and Challenges

[nagendraK6]

Environment

Mainnet

Acknowledgement

• I understand that issues are expected with the Go SDK as they are being updated.

Issue Description

I am working with a smart contract on zkSync that includes claim and transfer functions. The challenge is ensuring that both functions are executed in the same block to prevent a hacker-controlled bot from intercepting or redirecting the assets. This bot immediately transfers any ETH sent to the compromised wallet, making direct interactions with the wallet's funds risky.

Expected Behavior

The ideal solution would enable me to securely claim assets from a compromised wallet and subsequently transfer them to a safe wallet within the same block on zkSync. This atomic execution is crucial to prevent a hacker-controlled bot from intercepting the assets during the transfer process. Once the claim function validates the conditions and confirms the user's entitlement to the assets, the assets should be immediately redirected to a secure wallet, ensuring no delay or opportunity for external interference.

Code Example

Below is a sample smart contract illustrating the claim function used in this scenario. This function is part of a larger process to recover and securely transfer assets from a compromised wallet on zkSync:

function claim() public {
require(block.number >= claimPeriodStart, "claim not started");
require(block.number < claimPeriodEnd, "claim ended");

uint256 amount = claimableTokens[msg.sender];
require(amount > 0, "nothing to claim");

claimableTokens[msg.sender] = 0;

require(token.transfer(msg.sender, amount), "fail token transfer");
emit HasClaimed(msg.sender, amount);

}
This code serves as an example of how assets are claimed in a smart contract environment on the zkSync platform. The claim function performs crucial checks to ensure that the claim period is active and that the caller has a legitimate claim to tokens. Upon meeting these conditions, it zeroes the caller's claimable tokens and initiates a transfer of these tokens to their address.

However, I'm currently facing a challenge in ensuring that the token transfer executed by this claim function and any subsequent transfers of these tokens to a secure wallet can be performed within the same block. This simultaneous execution is essential to prevent any potential interference from malicious actors or bots associated with the compromised wallet. If anyone has insights or strategies on how to achieve atomic transactions within the same block on zkSync, your advice would be invaluable.

Repo Link (Optional)

No response

[gleenai[bot]]

To address the challenge of ensuring atomic transactions within the same block on zkSync, particularly for scenarios involving compromised wallets where a bot might intercept or redirect assets, you can consider implementing a few strategies. These strategies focus on minimizing the window of opportunity for malicious actors to act between the execution of claim and transfer functions.

Strategies for Securing Atomic Transactions on zkSync

1. Single Transaction Execution:

   • Modify your smart contract to handle both claiming and transferring in a single transaction. This ensures that once the claim function validates the conditions and confirms the user's entitlement to the assets, it immediately transfers them to a secure wallet within the same transaction.

   • Here’s a conceptual example of how you might modify your existing claim function to include a transfer to a secure wallet:

     function claimAndTransfer(address secureWallet) public {
         require(block.number >= claimPeriodStart, "claim not started");
         require(block.number < claimPeriodEnd, "claim ended");
     
         uint256 amount = claimableTokens[msg.sender];
         require(amount > 0, "nothing to claim");
     
         claimableTokens[msg.sender] = 0;
     
         // Ensure the transfer is to a secure wallet directly within the same transaction
         require(token.transfer(secureWallet, amount), "fail token transfer");
         emit HasClaimed(msg.sender, amount);
     }

2. Use of Checks-Effects-Interactions Pattern:

   • This pattern minimizes the risk of reentrancy attacks which can be part of the issues when dealing with compromised wallets. By ensuring that interactions (like transferring tokens) occur after all checks and effects (like updating state variables), you reduce the risk of unexpected behavior.

3. Security Audits and Testing:

   • Before deploying your modified contract, ensure it undergoes thorough security audits and testing to identify any potential vulnerabilities that could be exploited by attackers. This is crucial when handling transactions involving compromised wallets.

4. Monitoring and Alerts:

   • Implement monitoring tools to watch for suspicious activities involving the compromised wallet. Automated alerts can help in taking quick actions if unexpected behaviors are detected.

5. Time Locks and Multi-Signature Wallets:

   • Consider using time locks or multi-signature wallets for the secure wallet. This adds an additional layer of security, making it harder for attackers to immediately transfer out the assets even if they manage to intercept them.

Final Thoughts

Implementing these strategies requires careful planning and understanding of smart contract development and security. If you're not experienced with smart contract security, it might be beneficial to consult with or hire a security expert to review your contract and implementation strategy. This ensures that your approach to securing atomic transactions on zkSync is robust and minimizes risks associated with compromised wallets.