Skip to main content

Incorrect Exponentiation

Description​

The operator ^ is not an exponential operator, it is a bitwise XOR. Make sure to use pow() instead for exponentiation. In case of performing a XOR operation, use .bitxor() for clarity.

Exploit Scenario​

In the following example, the ^ operand is being used for exponentiation. But in Rust, ^ is the operand for an XOR operation. If misused, this could lead to unexpected behaviour in our contract.

    #[ink(message)]
    pub fn exp_data_by_3(&mut self) {
        self.data ^= 3
    }

The vulnerable code example can be found here.

Remediation​

A possible solution is to use the method pow(). But, if a XOR operation is wanted, .bitxor() method is recommended.

    #[ink(message)]
    pub fn exp_data_by_3(&mut self) {
        self.data = self.data.pow(3)
    }

The remediated code example can be found here.

References​