CSC/ECE 517 Fall 2023 - E2377. Reimplement impersonating users (functionality within impersonate controller.rb)

Expertiza

Expertiza is a Ruby on Rails based open source project. Instructors have the ability to add new projects, assignments, etc., as well as edit existing ones. Later on, they can view student submissions and grade them. Students can also use Expertiza to organize into teams to work on different projects and assignments and submit their work. They can also review other students' submissions.

Problem Statement

The current expertiza platform allows authorized users to impersonate others, utilizing session-based authentication. The challenge is to reimplement this feature in the new expertiza backend (https://github.com/expertiza/reimplementation-back-end), which employs JWT token authentication.

Key challenges include adapting the existing session-based logic to work seamlessly with JWT tokens and transitioning from a Model-View-Controller (MVC) architecture to an API-only setup, requiring responses in JSON format. The goal is to ensure the smooth integration of the impersonation feature into the new backend while addressing authentication changes and architectural shifts.

Solution

We have converted the impersonate users functionality from the MVC pattern in Expertiza to match the Rails API specification for the reimplementation backend repository. We have reimplemented the impersonate_controller.rb file located within expertiza/app/controllers/. The link to the original controller within expertiza can be found at this link: Original Controller

This is not the only file that we have edited. We also needed to edit users.rb file to add some functionality regarding the impersonation criteria. We have used JWT Tokens for authentication. The front end will still be responsible for storing the original user to get the original user back in function. Our code works work to change the current user as and when necessary in the API. We also ensure that user privileges are checked to authorize only the relevant users to impersonate student users. Users that are super admin, TAs for other users or recursively parents of the user they are trying to impersonate can impersonate the user. We have also ensured that we have the supporting methods in the User class implemented. One such example of a method that we have reimplemented is the “can_impersonate?” method within the User class.

Design

Methods Reimplemented

Original

def action_allowed?
    # Check for TA privileges first since TA's also have student privileges.
    if ['Student'].include? current_role_name
      !session[:super_user].nil?
    else
      ['Super-Administrator',
       'Administrator',
       'Instructor',
       'Teaching Assistant'].include? current_role_name
    end
  end

Modification : We have removed the session and stored the user with a JWT token to authenticate. So this method is no longer required.

Original

def auto_complete_for_user_name
    @users = session[:user].get_available_users(params[:user][:name])
    render inline: "<%= auto_complete_result @users, 'name' %>", layout: false
  end

Modification : Instead of using session we just access the current user, and since this is a frontend task we decided to not keep it.

Original

  def start
    flash[:error] = "This page doesn't take any query string." unless request.GET.empty?
  end

Modification : We removed the flash error as it will not work in the our new implementation.

Original

 def generate_session(user)
    AuthController.clear_user_info(session, nil)
    session[:original_user] = @original_user
    session[:impersonate] = true
    session[:user] = user
  end

Modification : This method is now called inside the 'impersonate' method using JWT token

Original

def overwrite_session
    if params[:impersonate].nil?
      user = real_user(params[:user][:name])
      session[:super_user] = session[:user] if session[:super_user].nil?
      generate_session(user)
    elsif !params[:impersonate][:name].empty?
      user = real_user(params[:impersonate][:name])
      generate_session(user)
    else
      session[:user] = session[:super_user]
      session[:super_user] = nil
    end
  end

Modification : We got rid of this method as we now authenticate the user with a JWT token instead.

Original

def check_if_input_is_valid
    if params[:user] && warn_for_special_chars(params[:user][:name], 'Username')
      flash[:error] = 'Please enter valid user name'
      redirect_back fallback_location: root_path
    elsif params[:impersonate] && warn_for_special_chars(params[:impersonate][:name], 'Username')
      flash[:error] = 'Please enter valid user name'
      redirect_back fallback_location: root_path
    end
  end

Modification : We have changed the number of parameters for this method. Instead of two, this method now only takes one parameter which is the username of the user we wish to impersonate. We also have removed the flash errors.

Modified code

  def check_if_input_is_valid
    if params[:impersonate].blank? || warn_for_special_chars(params[:impersonate], 'Username')
      # render json: { success: false, error: 'Please enter valid user name' }, status: :unprocessable_entity
    end
  end


  def warn_for_special_chars(str, field_name)
    puts str
    if contains_special_chars? str
      render json: { success: false, error: field_name + " must not contain special characters '" + special_chars + "'." }, status: :unprocessable_entity
      return true
    end
    false
  end

  def contains_special_chars?(str)
    special = special_chars
    regex = /[#{Regexp.escape(special)}]/
    !str.match(regex).nil?
  end
    def special_chars
      '/\\?<>|&$#'
    end

Modification : This new method checks and warns about special characters used in the input. The special characters it checks for are /\\?<>|&$#

Original

def check_if_user_impersonateable
    if params[:impersonate].nil?
      user = real_user(params[:user][:name])
      unless @original_user.can_impersonate? user
        @message = "You cannot impersonate '#{params[:user][:name]}'."
        temp
        AuthController.clear_user_info(session, nil)
      else
        overwrite_session
      end
    else
      unless params[:impersonate][:name].empty?
        overwrite_session
      end
    end
  end

Modification : We changed the session to a JWT token in this method.

Modified code

 def check_if_user_impersonatable?
      user = User.find_by(name: params[:impersonate] )
      if user
        return @current_user.can_impersonate? user
      end
      false
      end

Original

def impersonate
    begin
      @original_user = session[:super_user] || session[:user]
      if params[:impersonate].nil?
        @message = "You cannot impersonate '#{params[:user][:name]}'."
        @message = 'User name cannot be empty' if params[:user][:name].empty?
        user = real_user(params[:user][:name])
        check_if_user_impersonateable if user
      elsif !params[:impersonate][:name].empty?
        # Impersonate a new account
        @message = "You cannot impersonate '#{params[:impersonate][:name]}'."
        user = real_user(params[:impersonate][:name])
        check_if_user_impersonateable if user
      # Revert to original account when currently in the impersonated session
      elsif !session[:super_user].nil?
        AuthController.clear_user_info(session, nil)
        session[:user] = session[:super_user]
        user = session[:user]
        session[:super_user] = nil
      end
      # Navigate to user's home location as the default landing page after impersonating or reverting
      AuthController.set_current_role(user.role_id, session)
      redirect_to action: AuthHelper.get_home_action(session[:user]),
                  controller: AuthHelper.get_home_controller(session[:user])
    rescue StandardError
      flash[:error] = @message
      redirect_back fallback_location: root_path
    end
  end

Modification : Modified code using JWT tokens

def impersonate
      if check_if_user_impersonatable?
        user = User.find_by(name: params[:impersonate])

        if user
          impersonate_payload = { id: user.id, name: user.name, full_name: user.full_name, role: user.role.name,
                          institution_id: user.institution.id, impersonate: true, original_user: @current_user }
          impersonate_token = JsonWebToken.encode(impersonate_payload, 24.hours.from_now)
  
          render json: { success: true, token: impersonate_token, message: "Successfully impersonated #{user.name}" }
        else
          render json: { success: false, error: 'User not found' }, status: :not_found
        end
      else
        render json: { success: false, error: "You don't have permission to impersonate this user" }, status: :forbidden
      end
    end

Modification : In order to check if the user can be impersonated, we delegate it to the user class. The user class now handles this part of checking

Modified code in user.rb

  def can_impersonate?(user)
    return true if role.super_administrator?
    return true if teaching_assistant_for?(user)
    return true if recursively_parent_of(user)

    false
    

  end
  def teaching_assistant_for?(student)
    return false unless ta?
    return false unless student.role.name == 'Student'

    # We have to use the Ta object instead of User object
    # because single table inheritance is not currently functioning
    ta = Ta.find(id)
    ta.managed_users.each { |user|
      if user.id == student.id
        return true
      end
    }
    false
  end

  def recursively_parent_of(user)
    p = user.parent
    return false if p.nil?
    return true if p == self
    return false if p.role.super_administrator?

    recursively_parent_of(p)
  end
end 

Original

def real_user(name)
    if User.anonymized_view?(session[:ip])
      user = User.real_user_from_anonymized_name(name)
    else
      user = User.find_by(name: name)
    end
    return user
  end

Modification : IMPORTANT We believe that this project is a mix of frontend and backend. So the assumption we have made is that when a user wants to impersonate any other user, the JWT token for the current user is stored in the frontend. And when the 'session' for impersonation is over, the user is assigned their previous JWT token retrieved from the frontend.

Test Plan

For the testing of this project, we first tested all functionality using the Postman API. The working of the Postman testing video will be posted here in some time. We then tested our program using the RSwag tool. This allowed us to test and explore operations using a UI and directly from the rspec integration tests.
The video links for these testing methods will be posted here soon.

Team

Mentor
Renji Joseph Sabu <rsabu@ncsu.edu>

Students
Manoj Ayyappan <mayyapp@ncsu.edu>
Pradeep Patil <papatil@ncsu.edu>
Maya Patel <mdpatel2@ncsu.edu>

Pull Request

Changes for this project are under Expertiza Pull Request