README.md

Solidity Challenge #396 🕵️‍♂️

What are the potential security vulnerabilities in this smart contract?

Problem Explanation

The MysticalVault contract transfers its balance to the caller if four valid signatures are provided. There are several issues that could lead to failures or vulnerabilities.

What Went Wrong?

1. Fixed Loop Limit: The loop only iterates 4 times, assuming exactly 4 signatures are always required.
2. Signature Verification: Only checks if the recovered address from the signature matches the owner address.
3. Replay Attack Vulnerability: Signatures can be reused, causing multiple unauthorized transfers.
4. Inconsistent State Management: The lapsed mapping is updated after the transfer, leading to potential re-entrancy issues.

Example

1. The contract receives 10 ETH.
2. A user tries to redeem using 4 valid signatures.
3. The contract transfers the balance but does not update the state correctly, allowing for possible re-entrancy attacks.

Solution

1. Dynamic Loop Limit: Use the length of the sigs array for iteration.
2. Enhanced Signature Verification: Check signatures dynamically.
3. Prevent Replay Attacks: Ensure signatures cannot be reused.
4. Consistent State Management: Update the lapsed mapping before transferring funds.