Need

Implementation of robust data validation for numbers

Context

• Usage of Swift for iOS and macOS app development
• Usage of UIKit for building modern and responsive user interfaces

Description

Non compliant code

        import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var inputField: UITextField!
    
    func processInput() {
        let input = inputField.text
        let number = Int(input!)
        
        // Do something with the number
    }
}
        
        

In the above Swift code, the processInput function is taking user input from a text field and converting it directly to an integer. This is a prime example of a lack of data validation vulnerability because it assumes that the user will always provide a valid integer as input.

However, if the user provides a string that cannot be converted to an integer, the application will crash due to a runtime error. This is because the force unwrapping operator ( !) is used, which will trigger a runtime error if input is nil or not a valid integer.

Moreover, even if the user provides a valid integer, there's no validation to check if the integer is within an expected range. For instance, if the business logic expects a number between 1 and 100, but the user inputs 200, the application will not behave as expected.

This lack of data validation can lead to unexpected application behavior, crashes, and potential security risks if the unvalidated data is used in a security-sensitive context.

Steps

• Implement data validation to ensure that the input is a valid number.
• Check if the input is empty before converting it to an integer.
• Handle the case where the input is not a valid number and provide appropriate error handling.
• Consider using a different data type or validation mechanism depending on the specific requirements of the application.

Compliant code

        import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var inputField: UITextField!
    
    func processInput() {
        guard let input = inputField.text, !input.isEmpty else {
            // Handle the case where the input is empty
            print("Input is empty")
            return
        }
        
        guard let number = Int(input) else {
            // Handle the case where the input is not a valid number
            print("Input is not a valid number")
            return
        }
        
        // Do something with the number
    }
}
        
        

The updated code now includes data validation to ensure that the input is a valid number.

Firstly, we use a guard statement to check if the input is empty. If the input is empty, we print a message and return from the function. This prevents the application from trying to convert an empty string to an integer, which would cause a crash.

Secondly, we use another guard statement to try to convert the input to an integer. If the conversion fails (because the input is not a valid number), we print a message and return from the function. This prevents the application from trying to use an invalid number.

These changes ensure that the application can handle invalid input gracefully, without crashing or behaving unexpectedly. They also provide a clear place to add more sophisticated error handling if needed.

References

• 197. Lack of data validation - Numbers