TwentyOne

Summary

The contract does not include a mechanism for the owner to withdraw Ether that accumulates in the contract. Over time, forfeited wagers and unused deposits remain permanently locked, rendering the funds inaccessible. Without a withdrawal function, the Ether in the contract is effectively unusable, leading to inefficiencies and financial loss for the contract owner.

Vulnerability Details

• Root Cause:

  • The contract does not implement a withdrawal function for the owner to retrieve the accumulated Ether.

  • Any forfeited player wagers or unclaimed Ether from game activities are locked indefinitely in the contract balance.

• Symptoms:

  • The contract accumulates funds over time from:

    • Wagers lost by players.

    • Unused or excess Ether deposited for the prize pool.

  • These funds remain stuck in the contract, with no mechanism for the owner to reclaim or reallocate them.

• Code Affected:

  • No withdraw or similar function exists in the contract, preventing the owner from accessing the accumulated funds.

• Behavior Details:

  • Ether in the contract balance cannot be withdrawn by any actor, including the owner, resulting in permanent inaccessibility.

Impact

• Locked Funds:

  • Any Ether that accumulates in the contract cannot be accessed, leading to potential financial loss for the owner.

• Operational Inefficiency:

  • The inability to withdraw funds restricts the owner from reallocating the accumulated Ether for operational or strategic purposes.

• Protocol Shutdown Challenges:

  • If the game is discontinued or migrated to a new contract, the locked funds cannot be transferred, resulting in a complete loss of the accumulated balance.

Tools Used

Manual code review.

Recommendations

Add a Secure Withdrawal Function:

• Introduce a withdrawal function that allows the contract owner to retrieve Ether from the contract balance:

  function withdraw(uint256 amount) public onlyOwner {

  require(amount <= address(this).balance, "Insufficient contract balance");

  payable(owner).transfer(amount);

  }