Security best practices in Ruby on Rails - Mini Project: Build & Apply

Security Best Practices in Rails

📖 Scenario: You are building a simple Rails web application that handles user sign-up and login. To keep users safe, you need to apply security best practices in your Rails code.

🎯 Goal: Learn how to implement basic security best practices in a Rails app, including strong parameters, password hashing, and protection against common attacks.

📋 What You'll Learn

Use strong parameters to whitelist user input

Use has_secure_password for password hashing

Add CSRF protection in the controller

Sanitize user input before displaying

💡 Why This Matters

🌍 Real World

Web applications must protect user data and prevent attacks like CSRF, injection, and password theft. These practices keep users safe and build trust.

💼 Career

Rails developers are expected to know how to secure apps by using built-in features like strong parameters, password hashing, and CSRF protection.

1

Set up User model with secure password

Create a Rails model called User with attributes email:string and password_digest:string. Add has_secure_password to enable password hashing.

Ruby on Rails

# Create User model with email and password_digest
# Add has_secure_password inside the model

Hint

The has_secure_password method adds password hashing and authentication features.

2

Add strong parameters in UsersController

In UsersController, create a private method called user_params that uses params.require(:user).permit(:email, :password, :password_confirmation) to whitelist user input.

Ruby on Rails

class User < ApplicationRecord
  has_secure_password
end

class UsersController < ApplicationController
  # Add user_params method here
end

Hint

Strong parameters help prevent unwanted data from being saved.

3

Enable CSRF protection in ApplicationController

In ApplicationController, add protect_from_forgery with: :exception to enable CSRF protection.

Ruby on Rails

class ApplicationController < ActionController::Base
  # Add CSRF protection here
end

Hint

This line helps protect your app from cross-site request forgery attacks.

4

Sanitize user input before displaying

In a view file, use the Rails helper sanitize() to safely display user input stored in @user.email.

Ruby on Rails

Hint

Sanitize removes harmful HTML or scripts from user input before showing it.

Practice

1. Which Rails feature helps prevent unwanted or dangerous user input from being saved to the database?

easy

A. Strong Parameters

B. Active Record Callbacks

C. Action Mailer

D. Asset Pipeline

Solution

1. Step 1: Understand user input control

   Strong Parameters allow you to specify which attributes are allowed from user input, preventing mass assignment vulnerabilities.

2. Step 2: Identify the correct Rails feature

   Active Record Callbacks and others do not control input filtering; only Strong Parameters do.

3. Final Answer:

   Strong Parameters -> Option A

4. Quick Check:

   User input filtering = Strong Parameters [OK]

Hint: Strong Parameters filter user input safely [OK]

Common Mistakes:

• Confusing callbacks with input filtering
• Thinking Asset Pipeline handles security
• Assuming Action Mailer controls input

2. Which line correctly enables CSRF protection in a Rails controller?

easy

A. enable_csrf_protection!

B. protect_from_forgery with: :exception

C. csrf_protect true

D. use_csrf_protection = true

Solution

1. Step 1: Recall Rails CSRF protection syntax

   The correct method to enable CSRF protection is protect_from_forgery with: :exception in controllers.

2. Step 2: Check other options for validity

   Other options are not valid Rails syntax and will cause errors or have no effect.

3. Final Answer:

   protect_from_forgery with: :exception -> Option B

4. Quick Check:

   CSRF protection syntax = protect_from_forgery [OK]

Hint: Use protect_from_forgery with: :exception [OK]

Common Mistakes:

• Using non-existent methods for CSRF
• Forgetting to add CSRF protection
• Misnaming the method or options

3. Given this Rails view code:

<%= raw @user.name %>

What security risk exists if @user.name contains HTML tags?

medium

A. Cross-Site Scripting (XSS) attack

B. SQL Injection

C. Mass Assignment

D. Denial of Service

Solution

1. Step 1: Understand output escaping in Rails views

   Using <%= %> escapes HTML by default, but if raw HTML is inserted, it can cause XSS.

2. Step 2: Identify the risk of unescaped HTML in user input

   If @user.name contains HTML tags and is not escaped, it can run malicious scripts in the browser, causing XSS.

3. Final Answer:

   Cross-Site Scripting (XSS) attack -> Option A

4. Quick Check:

   Unescaped HTML in views = XSS risk [OK]

Hint: Unescaped user input risks XSS attacks [OK]

Common Mistakes:

• Confusing XSS with SQL Injection
• Assuming Rails never escapes output
• Ignoring HTML tags in user input

4. You see this code in a Rails controller:

params.require(:user).permit(:name, :email)

But users report they can update admin-only fields. What is the likely problem?

medium

A. CSRF protection is disabled

B. The controller action is missing

C. Strong Parameters are not used correctly

D. The database schema is incorrect

Solution

1. Step 1: Analyze the use of Strong Parameters

   The code shows permitted params, but if the controller does not use this filtered params hash for updating, mass assignment can happen.

2. Step 2: Identify why admin-only fields update

   If the controller uses unfiltered params or merges extra params, Strong Parameters are bypassed, causing security issues.

3. Final Answer:

   Strong Parameters are not used correctly -> Option C

4. Quick Check:

   Mass assignment issue = incorrect Strong Parameters use [OK]

Hint: Always use filtered params for updates [OK]

Common Mistakes:

• Assuming CSRF causes mass assignment
• Ignoring how params are passed to update
• Blaming database instead of controller code

5. You want to ensure all Rails app traffic is secure and user data is protected. Which combination of practices is best?

hard

A. Only use HTTPS and ignore CSRF and output escaping

B. Disable CSRF protection, use HTTP, and sanitize database inputs

C. Use HTTP, skip escaping output, and rely on user validation

D. Force HTTPS, enable CSRF protection, and escape all output

Solution

1. Step 1: Identify key security practices for web apps

   Forcing HTTPS encrypts data in transit, CSRF protection stops fake requests, and escaping output prevents XSS.

2. Step 2: Evaluate each option's security coverage

   Force HTTPS, enable CSRF protection, and escape all output covers all three essential protections. Others disable or ignore important protections, increasing risk.

3. Final Answer:

   Force HTTPS, enable CSRF protection, and escape all output -> Option D

4. Quick Check:

   HTTPS + CSRF + escaping = best security [OK]

Hint: Combine HTTPS, CSRF, and escaping for strong security [OK]

Common Mistakes:

• Ignoring CSRF protection importance
• Thinking HTTPS alone is enough
• Skipping output escaping