First Flight #2: Puppy Raffle

Summary

The selectWinner function in the PuppyRaffle smart contract is susceptible to overflow and underflow vulnerabilities due to the lack of protection against these issues in Solidity compiler version 0.7.6. The absence of SafeMath library usage in the current implementation leaves the contract exposed to potential arithmetic problems that can be exploited by malicious actors.

Vulnerability Details

The vulnerability revolves around arithmetic operations within the selectWinner function, which involve the multiplication and division of values. Without proper overflow and underflow protection, these operations can result in unexpected and erroneous calculations. While the details of the vulnerability depend on the specific calculations performed in the function, common vulnerabilities include:

1. Integer Overflow: Occurs when an arithmetic operation results in a value exceeding the maximum representable integer, causing the value to wrap around to a smaller number. This can lead to incorrect calculations and unintended consequences.

2. Integer Underflow: Occurs when an arithmetic operation results in a value less than zero, which is not valid for unsigned integers. Underflows can lead to erroneous results and unintended behaviors.

Impact

The impact of overflow and underflow vulnerabilities can vary, but in the context of the selectWinner function, it could lead to:

• Incorrect Prize Calculation: An attacker might manipulate the calculations, leading to incorrect prize pool distribution. This could result in a disproportionate reward to the winner or even draining the prize pool entirely.

• Loss of Funds: If the contract relies on accurate calculations for financial transactions, the vulnerability could allow an attacker to drain funds from the contract.

Tools Used

This analysis is based on a manual review of the smart contract code.

Recommendations

To address the overflow and underflow vulnerabilities in the selectWinner function, consider the following recommendations:

• Use SafeMath Library: Implement arithmetic operations with the SafeMath library to ensure that calculations do not result in overflows or underflows.

OR

• ** Update Compiler Version:** Consider updating to the latest compiler version, such as 0.8.0 or higher, which provides built-in protections against overflow and underflow vulnerabilities.