Agent Skills: Rails Security & Data Protection

Rails Security & Data Protection

Comprehensive security implementation with Lockbox, Blind Index, and Pundit.

When to Use This Skill

• Implementing authorization with Pundit policies
• Encrypting sensitive data with Lockbox
• Adding searchable encryption with Blind Index
• Configuring authentication (Devise)
• Setting up secure credentials and secrets
• Implementing two-factor authentication
• Fixing security vulnerabilities
• Setting up HTTPS, CORS, CSP
• Preventing common attacks (XSS, CSRF, SQL injection)

Core Security Stack

# Gemfile
gem "lockbox"           # Encryption at rest
gem "blind_index"       # Searchable encryption
gem "pundit"            # Authorization
gem "devise"            # Authentication (optional)
gem "brakeman"          # Security scanner
gem "bundler-audit"     # Dependency vulnerabilities

Encryption at Rest (Lockbox)

Setup

# Install
$ rails lockbox:install

# Creates config/master.key (DO NOT COMMIT!)

Encrypting Model Fields

# app/models/user.rb
class User < ApplicationRecord
  # Encrypt sensitive fields
  has_encrypted :email, :ssn, :phone, :credit_card_number

  # Lockbox creates:
  # - email_ciphertext (stored in DB)
  # - email (virtual, decrypted)
end

Migration

class AddEncryptedFieldsToUsers < ActiveRecord::Migration[7.1]
  def change
    add_column :users, :email_ciphertext, :text
    add_column :users, :ssn_ciphertext, :text
    add_column :users, :phone_ciphertext, :text
  end
end

Usage

# Writing
user = User.create!(email: "user@example.com")  # Auto-encrypted

# Reading
user.email  # => "user@example.com" (auto-decrypted)

# Database stores encrypted
user.email_ciphertext  # => "encrypted_string..."

Searchable Encryption (Blind Index)

Setup

# app/models/user.rb
class User < ApplicationRecord
  has_encrypted :email, :phone

  # Add blind indexes for searchable fields
  blind_index :email
  blind_index :phone
end

Migration

class AddBlindIndexesToUsers < ActiveRecord::Migration[7.1]
  def change
    add_column :users, :email_bidx, :string
    add_column :users, :phone_bidx, :string

    add_index :users, :email_bidx, unique: true
    add_index :users, :phone_bidx
  end
end

Searching Encrypted Fields

# Find by encrypted field (works!)
user = User.find_by(email: "user@example.com")

# Where clause
users = User.where(email: "user@example.com")

# Limitations
User.where("email LIKE ?", "%partial%")  # Won't work
User.where("email > ?", "a@a.com")       # Won't work (no range queries)

Authorization (Pundit)

Setup

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  include Pundit::Authorization

  rescue_from Pundit::NotAuthorizedError, with: :user_not_authorized

  private

  def user_not_authorized
    flash[:alert] = "You are not authorized to perform this action."
    redirect_to(request.referrer || root_path)
  end
end

Policy Example

# app/policies/article_policy.rb
class ArticlePolicy < ApplicationPolicy
  def index?
    true  # Anyone can view list
  end

  def show?
    record.published? || user_is_author?
  end

  def create?
    user.present?
  end

  def update?
    user_is_author? || user&.admin?
  end

  def destroy?
    user_is_author? || user&.admin?
  end

  class Scope < Scope
    def resolve
      if user&.admin?
        scope.all
      elsif user
        scope.where(published: true).or(scope.where(user: user))
      else
        scope.where(published: true)
      end
    end
  end

  private

  def user_is_author?
    user && record.user == user
  end
end

Using in Controllers

class ArticlesController < ApplicationController
  def index
    @articles = policy_scope(Article)
  end

  def show
    @article = Article.find(params[:id])
    authorize @article
  end

  def update
    @article = Article.find(params[:id])
    authorize @article

    if @article.update(article_params)
      redirect_to @article
    else
      render :edit
    end
  end
end

Using in Views

<% if policy(@article).update? %>
  <%= link_to "Edit", edit_article_path(@article) %>
<% end %>

<% if policy(@article).destroy? %>
  <%= button_to "Delete", article_path(@article), method: :delete %>
<% end %>

Authentication (Devise)

Strong Configuration

# config/initializers/devise.rb
Devise.setup do |config|
  # Strong passwords
  config.password_length = 12..128

  # Paranoid mode (don't reveal if email exists)
  config.paranoid = true

  # Account lockout
  config.lock_strategy = :failed_attempts
  config.maximum_attempts = 5
  config.unlock_strategy = :time
  config.unlock_in = 1.hour

  # Session timeout
  config.timeout_in = 30.minutes
end

Secure Configuration

Never Commit Secrets

# .gitignore
/.env
/config/master.key
/config/credentials/*.key

Use Rails Credentials

# Edit credentials
$ EDITOR=vim rails credentials:edit

# In file:
aws:
  access_key_id: YOUR_KEY
  secret_access_key: YOUR_SECRET

# Access in code
Rails.application.credentials.aws[:access_key_id]

HTTPS Enforcement

# config/environments/production.rb
config.force_ssl = true

Common Security Pitfalls

1. Mass Assignment

# VULNERABLE
def create
  User.create(params[:user])  # Allows ANY attribute!
end

# SAFE
def create
  User.create(user_params)
end

private

def user_params
  params.require(:user).permit(:name, :email, :password)
end

2. SQL Injection

# VULNERABLE
User.where("name = '#{params[:name]}'")

# SAFE
User.where("name = ?", params[:name])
User.where(name: params[:name])

3. XSS (Cross-Site Scripting)

<%# VULNERABLE %>
<%= raw @article.body %>
<%= @article.body.html_safe %>

<%# SAFE - Escape by default %>
<%= @article.body %>

<%# Or sanitize allowed HTML %>
<%= sanitize @article.body, tags: %w[p br strong em] %>

4. Insecure Direct Object References

# VULNERABLE - No authorization
def show
  @article = Article.find(params[:id])
end

# SAFE - Authorize first
def show
  @article = Article.find(params[:id])
  authorize @article
end

# Or scope to current user
def show
  @article = current_user.articles.find(params[:id])
end

5. Timing Attacks

# VULNERABLE
def valid_api_key?(provided_key)
  provided_key == stored_key  # Timing reveals info
end

# SAFE
def valid_api_key?(provided_key)
  ActiveSupport::SecurityUtils.secure_compare(provided_key, stored_key)
end

Security Checklist

Before deploying:

• ✓ All secrets in credentials, not code
• ✓ SSL/HTTPS enforced in production
• ✓ Strong password requirements
• ✓ CSRF protection enabled
• ✓ Mass assignment protected (strong params)
• ✓ Authorization checks on all actions
• ✓ Sensitive data encrypted (Lockbox)
• ✓ Brakeman scan passes
• ✓ bundler-audit passes
• ✓ Input validation on all user data
• ✓ Output escaping by default

Running Security Scans

# Security scan
bundle exec brakeman --no-pager

# Dependency audit
bundle exec bundle-audit check --update

# Both should pass before merge

Reference Documentation

For comprehensive security patterns:

• Security guide: security.md (detailed examples and advanced patterns)