Need

Implementation of proper data validation for HTML code

Context

• Usage of Ruby 2.7 for developing Ruby applications
• Usage of Rails framework for building web applications
• Usage of ActiveRecord for Object-Relational Mapping (ORM) in a Node.js application

Description

Non compliant code

        class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    render json: @user
  end
end
        
        

In the above code, we have a show action in UsersController which finds a user based on id passed in the parameters and then renders the user as a JSON response.

The vulnerability here is the lack of data validation. The user input is directly used to query the database without any sanitization or validation checks. This opens up the possibility for HTML code injection.

An attacker could potentially manipulate the id parameter in a way that injects valid HTML code into the JSON response. When this response is interpreted by the client-side of the application, the injected HTML code could be executed, leading to potential Cross-Site Scripting (XSS) attacks. The attacker could use this to steal sensitive information, perform actions on behalf of the user, or even deliver malware to the user's browser.

Therefore, it's crucial to validate and sanitize all user inputs before using them to interact with the database or including them in any response.

Steps

• Implement input validation to ensure that the data received is safe and does not contain any malicious HTML code.
• Use appropriate sanitization techniques to sanitize the user input before rendering it in the JSON response.
• Consider using a library or framework feature that automatically escapes HTML characters to prevent HTML injection attacks.
• Regularly update the Ruby on Rails framework and its dependencies to benefit from the latest security patches and fixes.
• Perform security testing and code reviews to identify and address any other potential vulnerabilities in the application.

Compliant code

        class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    sanitized_user = sanitize(@user)
    render json: sanitized_user
  end

  private

  def sanitize(user)
    user.attributes.transform_values do |value|
      ActionController::Base.helpers.sanitize(value)
    end
  end
end
        
        

The original code was vulnerable to HTML injection attacks because it did not validate or sanitize the user data before rendering it in the JSON response. This could allow an attacker to inject malicious HTML code, which could be interpreted by the site receiving the JSON response.

The fixed code addresses this vulnerability by implementing a sanitize method that sanitizes the user data before it is rendered in the JSON response. This method uses the sanitize helper provided by the ActionController::Base class in the Ruby on Rails framework, which automatically escapes HTML characters to prevent HTML injection attacks.

The sanitize method is called on the @user object before it is rendered in the JSON response. This ensures that any malicious HTML code in the user data is escaped and cannot be interpreted by the site receiving the JSON response.

In addition to this fix, it is recommended to regularly update the Ruby on Rails framework and its dependencies to benefit from the latest security patches and fixes. It is also recommended to perform security testing and code reviews to identify and address any other potential vulnerabilities in the application.

References

• 321. Lack of data validation - HTML code