Insecure functionality - Scala

Insecure functionality - Scala

Need

Secure functionality implementation

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
  • Usage of global execution context for Scala concurrent programming
  • Usage of scala.sys.process.Process for executing system commands in Scala
  • Usage of scala.concurrent.Future for asynchronous programming in Scala
  • Usage of play.api.mvc.ControllerComponents for building controllers in a Play Framework application
  • Usage of play.api.mvc.AbstractController for creating controllers in the Play Framework
  • Usage of play.api.mvc.Action for handling HTTP requests in Play Framework
  • Usage of play.api.mvc.Request for handling HTTP requests in Play Framework
  • Usage of play.api.mvc.AnyContent for handling any type of request content in Play Framework
  • Usage of play.api.mvc.Result for handling HTTP responses in Play Framework
  • Usage of play.api.mvc.Results.Ok for returning an HTTP 200 OK response in Play Framework

Description

Non compliant code

        import play.api.mvc._
import scala.concurrent.ExecutionContext.Implicits.global

class HomeController @Inject()(cc: ControllerComponents) extends AbstractController(cc) {

  def index() = Action.async { implicit request: Request[AnyContent] =>
    val param = request.getQueryString("userInput")

    val result = scala.sys.process.Process("command " + param).!!

    Future.successful(Ok(result))
  }
}

In the above code, we have a Play Framework controller which handles an HTTP request. The index function is an asynchronous action that takes a request and returns a future result.

The vulnerability lies in the following line:

                val result = scala.sys.process.Process("command " + param).!!


Here, the application is directly using the user-provided input ( param) in a command that is executed by the system. This is a classic example of an insecure functionality, specifically a command injection vulnerability.

Command injection vulnerabilities occur when an application passes unsafe user-supplied data (forms, cookies, HTTP headers, etc.) to a system shell. In this case, the user-provided input is directly concatenated with a system command. This allows an attacker to execute arbitrary commands on the host operating system using a simple command injection payload.

For instance, if an attacker provides a value such as " ; rm -rf / --no-preserve-root" as the userInput, it will cause the deletion of all files in the server's file system, leading to a catastrophic failure of the system.

This insecure functionality can be leveraged by an attacker to negatively impact the system, potentially gaining unauthorized access, extracting sensitive information, or even causing a denial of service.

Steps

  • Validate and sanitize user input: Before using the user input in any command or operation, ensure that it is properly validated and sanitized to prevent any malicious input.
  • Implement input validation: Use appropriate validation techniques to ensure that the user input meets the expected format and constraints. This can include checking for allowed characters, length limits, and data type validation.
  • Use parameterized queries or prepared statements: When constructing commands or queries that involve user input, use parameterized queries or prepared statements instead of concatenating the input directly into the command. This helps to prevent SQL injection attacks.
  • Implement least privilege principle: Ensure that the code running the command or operation has the minimum necessary privileges to perform the task. Avoid running commands with root/administrator privileges if possible.
  • Implement proper error handling: Handle errors gracefully and avoid exposing sensitive information in error messages. Provide generic error messages to the user without revealing specific details about the system or the vulnerability.
  • Regularly update and patch dependencies: Keep the Play framework and other dependencies up to date with the latest security patches to mitigate any known vulnerabilities.
  • Perform security testing: Regularly conduct security testing, such as penetration testing and code reviews, to identify and address any potential vulnerabilities in the application.

Compliant code

        import play.api.mvc._
import scala.concurrent.ExecutionContext.Implicits.global
import play.api.data._
import play.api.data.Forms._

class HomeController @Inject()(cc: ControllerComponents) extends AbstractController(cc) {

  val userInputForm = Form(
    single(
      "userInput" -> nonEmptyText
    )
  )

  def index() = Action.async { implicit request: Request[AnyContent] =>
    val formValidationResult = userInputForm.bindFromRequest
    formValidationResult.fold(
      formWithErrors => {
        // This is the failure case, where the form value was invalid.
        // In a real application, you would not normally do this here, but
        // would return a bad request or similar.
        Future.successful(BadRequest("Invalid input"))
      },
      userData => {
        // This is the success case, where the form value was valid.
        // Run the command safely without directly concatenating user input.
        val result = scala.sys.process.Process(Seq("command", userData)).!!
        Future.successful(Ok(result))
      }
    )
  }
}

The original code was vulnerable to command injection attacks because it directly concatenated user input into a system command without any validation or sanitization. This could allow an attacker to execute arbitrary commands on the system.

The fixed code addresses this vulnerability by implementing several security measures:

1. Input Validation and Sanitization: The userInputForm is used to validate the user input. It ensures that the input is not empty. In a real-world application, you would add more validation rules here to ensure the input meets your specific requirements.

2. Safe Command Execution: Instead of directly concatenating the user input into the command, the fixed code uses a Seq to pass the command and the user input separately to the Process method. This ensures that the user input is treated as a single argument to the command, not part of the command itself.

3. Error Handling: If the form validation fails, the code returns a BadRequest response with a generic error message. This avoids exposing any sensitive information in the error message.

Remember to regularly update your dependencies and perform security testing to identify and fix any potential vulnerabilities.

References