Super Sushi Samurai Hack Analysis

Overview:

On March 21, 2024, Super Sushi Samurai suffered an attack due to a double token transfer issue, leading to an approximate loss of over 4.8M USD.

Smart Contract Hack Overview:

• Attacker address: 0x6a89a8
• Vulnerable Contract: 0xdfdcdb
• Attack Contract:0xded85d
• Attack Transaction: 0x62e6b9

Fig: Attack Transaction

Decoding the Smart Contract Vulnerability:

1. The attacker manipulated the transfer function by initiating transactions with both the sender and receiver addresses set to their own.
2. The update function, triggered by the transfer, lacked the necessary checks, making it vulnerable to exploitation.
3. Without differentiation between standard transfers and self-transfers, the update function effectively doubled the attacker’s token balance with each transaction.
4. In the `postCheck` function, the `toBalance` calculation compounded the vulnerability by adding current `balances[to]` to the `amountAfterTax` values.
5. Since both `balances[from]` and `balances[to]` were updated after `postCheck`, and with identical addresses in the transfer, they pointed to the same storage location.
6. Consequently, balances[to] doubled with each transaction, allowing attackers to profit at the expense of Super Sushi Samurai and its users.

Fig: The root cause of the vulnerability

Mitigation and Best Practices:

• This easy but powerful action could have stopped the problem that caused tokens to double by mistake: require(from != to, “Both addresses cannot be the same.”);
• Always validate your code by writing comprehensive test cases that cover all the possible business logic.
• To prevent such vulnerabilities, the best Smart Contract auditors must examine the Smart Contracts for logical issues. We at CredShields provide smart contract security and end-to-end security of web applications and externally exposed networks. Schedule a call at https://credshields.com/
• Scan your Solidity contracts against the latest common security vulnerabilities with 130+ detections at SolidityScan

Fig: SolidityScan — Smart Contract Vulnerability Scanner

Conclusion:

SolidityScan is an advanced smart contract scanning tool that discovers vulnerabilities and reduces risks in code. Request a security audit with us, and we will help you secure your smart contracts. Signup for a free trial at https://solidityscan.com/signup

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