Lack of data validation - Type confusion

Need

Implementation of proper data validation and type checking

Context

• Usage of Scala for building scalable and high-performance applications

• Usage of play.api.mvc for handling HTTP requests and responses in Play Framework

Description

1. Non compliant code

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.

2. Steps

• Implement proper data validation to ensure that the input is in the expected format.

• Use regular expressions or specific parsing methods to validate and parse the input.

• Reject or handle the input appropriately if it does not match the expected format.

• Avoid directly interpreting or converting the input without proper validation.

• Consider using a whitelist approach to only allow specific characters or patterns in the input.

• Sanitize the input by removing any potentially harmful characters or sequences.

• Implement server-side validation to complement client-side validation.

• Educate developers about the importance of data validation and secure coding practices.

3. 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
      case Some(num) => Ok("Processed: " + num)...

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

• 127. Lack of data validation - Type confusion

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