Need

Enforce proper control of interaction frequency to prevent abuse and ensure fair resource allocation, including rate limiting of sensitive endpoints such as password changes

Context

Description

# --- Post creation ---
class PostsController < ApplicationController
  def create
    post = Post.new(post_params)
    if post.save
      render json: post, status: :created
    else
      render json: post.errors, status: :unprocessable_entity...

**Post creation:** In the above code, we have a `PostsController` with a `create` action that is used to create new posts. The `create` action creates a new `Post` object with parameters `title` and `content` that are passed in the request. If the post is saved successfully, it returns the post as JSON with a status code of `201 (created)`. If it fails, it returns the errors as JSON with a status code of `422 (unprocessable entity)`. The vulnerability in this code is that there is no control over the frequency of interactions. This means that a user can send as many requests to this endpoint as they want in a short period of time. This can lead to a Denial of Service (DoS) attack where the server gets overwhelmed with too many requests and can't process legitimate requests. This can also lead to a user creating a large number of posts in a short period of time, which can be a form of spamming. **Password change:** In the above code, we have a UsersController with an `update_password` method. This method is used to update the password of a user. It first finds the user with the provided id from the parameters, then it attempts to update the user's password with the new password provided in the parameters. The vulnerability here is that there is no limit to the number of times a password can be updated in a day. This means that an attacker could potentially use a script to continuously change a user's password, causing a denial of service for that user as they would constantly need to reset their password. This could also potentially allow an attacker to guess a user's password if they are able to change it enough times.

# Add the rack-attack gem to your Gemfile
gem 'rack-attack'

# Then run bundle install
bundle install

# Create a new file config/initializers/rack_attack.rb and add the following code:
...

**Post creation:** The above code fixes the vulnerability by implementing rate limiting using the `rack-attack` gem. First, we add the `rack-attack` gem to the Gemfile and run `bundle install` to install it. Next, we create a new initializer file `rack_attack.rb` and configure the rate limit settings. In this case, we limit the number of requests to 5 per 5 seconds per IP address. Then, we update the `application.rb` file to use the `Rack::Attack` middleware. Finally, we update the `PostsController` to handle the rate limit exceeded scenario. If a user exceeds the rate limit, the server will respond with a 429 Too Many Requests status code and a JSON message indicating that the rate limit has been exceeded. This solution effectively prevents a user from making too many requests to the server in a short period of time, thus mitigating the risk of a denial-of-service attack. **Password change:** The updated code introduces a new constant `MAX_PASSWORD_CHANGES_PER_DAY` which is set to 3. This constant represents the maximum number of times a user can change their password in a day. In the `update_password` method, before updating the user's password, we check if the user has already reached the maximum number of password changes for the day by comparing `@user.password_changes_today` with `MAX_PASSWORD_CHANGES_PER_DAY`. If the user has not reached the limit, we proceed to update the password and increment the `password_changes_today` counter by 1 using the `increment!` method. If the user has reached the limit, we set a flash error message and render the edit page again. The error message informs the user that they have reached the maximum number of password changes allowed for the day. Please note that you need to add a `password_changes_today` column to your User model and reset this counter to 0 every day for each user. This can be done with a daily scheduled task. This solution helps to prevent abuse of the password change functionality by limiting the number of password changes a user can make in a day.

References