How to associate a user with a wallet

WalletAssociation.md

Overview

In order to associate a web2 user account with a Web3 wallet, we need a way for the database to provide a challenge that the web2 user must answer via web3.

Here is my very simple solution.

1. Api creates a unique nonce to an authorized user who has provided an EVM wallet address. This hash is stored with an expiration in the Db and returned to the client.
2. The client immediately initiates a transaction for the user to sign with the nonce as an argument to the smart contract function. This is sent to the WalletAssociation smart contract address.
3. The code packages the nonce with msg.sender and emits an event.

Here is the contract in its entirety:

pragma solidity ^0.8.0;

// Contract to handle user registration and challenge answer
contract WalletAssociation {
    event E(address indexed userWallet, uint256 answer, uint256 timestamp);
    function a(string memory answer) public {
        emit E(msg.sender, answer, block.timestamp);
    }
}

4. The indexer gathers the event and sends it to the backend to complete the handshake, checking the nonce address combination and validating the wallet for the user.

@Madgeniusblink are there any other potential exploits with this approach that would have to be accounted for?

If planned out properly and properly executed there wouldn't be many but there are always risk.

below are some risk:

Replay Attacks: If an attacker captures a valid signed challenge-response, they might try to replay it to the server to impersonate the user. To mitigate this we could do the following:

• Ensure challenges (nonces) are used only once.
• Set a short expiration time for the challenge.

Man-in-the-Middle Attacks (MitM): An attacker could intercept and modify traffic between the user and the server. To mitigate this we could do the following:

• Always use HTTPS for communications.
• Implement proper certificate pinning on client applications if possible.

Phishing: An attacker might trick users into signing malicious payloads or redirecting them to fake sites. To counter this:

• Educate users about the risks of phishing.
• Use recognizable patterns or messages when asking users to sign a challenge so they can distinguish genuine requests from malicious ones.

Storage of Signed Challenges: If signed challenges are stored insecurely, they could be stolen and used maliciously. To mitigate this:

• Store them securely, encrypted, and for only as long as necessary.
• Once verified, discard the signed challenge.

Endpoint Security: The server endpoint that verifies the signed challenge is a potential target. If it's compromised, false associations might be created. To counter this:

• Ensure robust security on all server endpoints.
• Regularly monitor and audit endpoint accesses.

Sybil Attacks: A malicious user could try to associate multiple fake or stolen Web2 accounts with their Web3 wallet. To mitigate this:

• Implement rate limiting.
• Have additional verification steps for associating accounts.

Reliance on Single Wallet: If a user loses access to their Web3 wallet, they might lose access to their associated Web2 account. To counter this:

• Allow users to associate multiple wallets or provide backup methods for association.
• Educate users about wallet backups and security.

There is always wallet vulnerabilities as well..