Lack of data validation - Type confusion - Scala

Need

Implementation of proper data validation and type checking

Context

1. Usage of Scala for building scalable and high-performance applications
2. Usage of play.api.mvc for handling HTTP requests and responses in Play Framework

Description

Insecure Code Example

import play.api.mvc._

object Application extends Controller {
  def process() = Action { request =>
    val data = request.body.asFormUrlEncoded.get("data").head
    val number = Integer.parseInt(data, 16)
    Ok("Processed: " + number)
  }
}

The above Scala code represents a Play Framework application with a single action, `process`. This action is vulnerable to a type confusion attack due to a lack of proper data validation. The `process` method retrieves a form parameter `data` from the incoming request. It then attempts to parse this parameter as a hexadecimal integer using `Integer.parseInt(data, 16)`. This is problematic because `Integer.parseInt(data, 16)` will accept not only regular decimal numbers, but also hexadecimal numbers (e.g., "0xff"). This is a form of type confusion, as the server-side code is interpreting the data in a way that is inconsistent with the expected input type (decimal number). If the `data` parameter is expected to only be a decimal number, then accepting hexadecimal numbers can lead to unexpected behavior and potential security vulnerabilities. For example, an attacker could input a large hexadecimal number that causes an integer overflow when parsed. To fix this vulnerability, the code should validate that the `data` parameter is a valid decimal number before attempting to parse it.

Steps

1. Implement proper data validation to ensure that the input is in the expected format.
2. Use regular expressions or specific parsing methods to validate and parse the input.
3. Reject or handle the input appropriately if it does not match the expected format.
4. Avoid directly interpreting or converting the input without proper validation.
5. Consider using a whitelist approach to only allow specific characters or patterns in the input.
6. Sanitize the input by removing any potentially harmful characters or sequences.
7. Implement server-side validation to complement client-side validation.
8. Educate developers about the importance of data validation and secure coding practices.

Secure Code Example

import play.api.mvc._
import scala.util.Try

object Application extends Controller {
  def process() = Action { request =>
    val data = request.body.asFormUrlEncoded.get("data").head
    val number = Try(Integer.parseInt(data, 16)).toOption
    number match {
      case Some(num) => Ok("Processed: " + num)
      case None => BadRequest("Invalid data format")
    }
  }
}

The original code was vulnerable due to a lack of data validation. It was directly parsing the input data as a hexadecimal number without checking if the input was in the correct format. This could lead to type confusion if the input was not a valid hexadecimal number. The fixed code adds data validation using Scala's `Try` and `Option` types. The `Try` block attempts to parse the input data as a hexadecimal number. If the parsing is successful, `Try` returns a `Success` containing the parsed number. If the parsing fails (for example, if the input is not a valid hexadecimal number), `Try` returns a `Failure`. The `toOption` method is then called on the `Try` result. This converts the `Success` or `Failure` to an `Option`. If the `Try` was a `Success`, `toOption` returns a `Some` containing the parsed number. If the `Try` was a `Failure`, `toOption` returns `None`. The `match` block then checks the `Option`. If the `Option` is `Some`, the input was a valid hexadecimal number and the number is processed. If the `Option` is `None`, the input was not a valid hexadecimal number and a `BadRequest` response is returned. This fix ensures that only valid hexadecimal numbers are processed, preventing type confusion. It also provides a clear error response if the input is not in the expected format.

References

Last updated

2023/09/18