Securing Passwords

Overview

In this lesson, we'll cover bcryp, a gem that works to encrypt passwords.

Objectives

Explain how bcrypt manipulates and stores passwords
Use Active Record's has_secure_password method
Sign up and in a user with a secure, encrypted password

Storing Users' Passwords

Securing users' data is one of the most important jobs of a web developer. Despite frequent warnings against it, many of your users will use the same username and password combination across many different websites. This means that, in general, people will use the same password for our applications that they do for their bank.

Because of this, we never want to store our users' passwords in plain text in our database. Instead, we'll run the passwords through a hashing algorithm. A hashing algorithm manipulates data in such a way that it cannot be un-manipulated. This is to say that if someone got a hold of the hashed version of a password, they would have no way to turn it back into the original. In addition to hashing the password, we'll also add a "salt". A salt is simply a random string of characters that gets added into the hash. That way, if two of our users use the password "fido", they will end up with different hashes in our database.

We'll use an open-source gem, bcrypt, to implement this strategy.

Starter Code

We've got a basic Sinatra MVC application. In our application_controller we have two helper methods defined: logged_in? returns true or false based on the presence of a session[:user_id] and current_user returns the instance of the logged in user, based on the session[:user_id]. We have five actions defined:

get "/" do renders an index.erb file with links to signup or login.
get '/signup' renders a form to create a new user. The form includes fields form username and password.
get '/login' renders a form for logging in.
get '/success' renders a success.erb page, which should be displayed once a user successfully logs in
get '/failure' renders a failure.erb page. This will be accessed if there is an error logging in or signing up.
get '/logout' clears the session data and redirects to the home page.

We've also stubbed out a user model in app/models/user.rb that inherits from ActiveRecord::Base.

Fork and clone this repository and run bundle install to get started! Preview your work by running shotgun and navigating to http://localhost:9393 in your browser.

Password Encryption with BCrypt

BCrypt will store a salted, hashed version of our users password in our database in a column called password_digest. Essentially, once a password is salted and hashed, there is no way for anyone to de-code it. This method requires that hackers use a "brute force" approach to gain access to someone's account - still possible, but more difficult.

Implementing BCrypt

We've created a migration file for you ( using rake db:create_migration NAME=create_users), but you'll need to fill it in. Let's edit that file so that it actually creates a users table. We'll have two columns: one for username and one for password_digest.

class CreateUsers < ActiveRecord::Migration
  def up
  	create_table :users do |t|
  		t.string :username
  		t.string :password_digest
  	end
  end

  def down
  	drop_table :users
  end
end

Run this migration using rake db:migrate. Awesome job!

ActiveRecord's `has_secure_password`

Next, let's update our user model so that it includes has_secure_password. This ActiveRecord macro gives us access to a few new methods. A macro is a method that when called, creates methods for you. This is meta programming, which you don't need to worry about now. Just know that using a macros is just like calling a normal ruby method.

In this case, the macro has_secure_password is being called just like a normal ruby method. It works in conjunction with a gem called bcrypt and gives us all of those abilities in a secure way that doesn't actually store the plain text password in the database.

class User < ActiveRecord::Base

	has_secure_password

end

Next, let's handle signing up. In our post '/signup' action, let's make a new instance of our user class with a username and password from params. Note that even though our database has a column called password_digest, we still access the attribute of password. This is given to us by has_secure_password. You can read more about that in the Ruby Docs.

	post "/signup" do
		user = User.new(:username => params[:username], :password => params[:password])
	end

Because our user has has_secure_password, we won't be able to save this to the database unless our user filled out the password field. Calling user.save will return false if the user can't be persisted. Let's update this route so that we redirect to '/login' if the user is saved, or '/failure' if the user can't be saved. (For now, we'll make the user log in after they sign up successfully).

	post "/signup" do
		user = User.new(:username => params[:username], :password => params[:password])
		if user.save
			redirect "/login"
		else
			redirect "/failure"
		end
	end

Awesome! Test this feature out in your browser. Leaving the password field blank should land you at the "failure" page, while creating a valid user should take you to login.

Next, create at least one valid user, then let's build out our login action. In post '/login', let's find the user by username.

	post "/login" do
		user = User.find_by(:username => params[:username])
	end

Next, we need to check two conditions: first, did we find a user with that username? This can be written as user != nil, or simply user.

	post "/login" do
		user = User.find_by(:username => params[:username])
		if user
			redirect "/success"
		else
			redirect "/failure"
		end
	end

We also need to check if that user's password matches up with our password_digest. We can use a method called authenticate. The method is provided for us by the bcrypt gem. Our authenticate method takes a string as an argument. If the string matches up against the password digest, it will return the user object, otherwise it will return false. Therefore, we can check that we have a user AND that the user is authenticated. If so, we'll set the session[:user_id] and redirect to the /success route. Otherwise, we'll redirect to the /failure route so our user can try again.

	post "/login" do
		user = User.find_by(:username => params[:username])
		if user && user.authenticate(params[:password])
			session[:user_id] = user.id
			redirect "/success"
		else
			redirect "/failure"
		end
	end

Awesome job! We've now built out a basic authentication system for a user without storing a plain-text password in our database.

Video Review

Authentication

Resources

BCrypt Ruby
Intro to BCrypt & Password Security - MakerSquare on YouTube
Ruby on Rails Guide: Has Secure Password
How NOT to Store Passwords! - Computerphile on Youtube

View Securing Passwords in Sinatra on Learn.co and start learning to code for free.

eleanorgraham/sinatra-password-security-v-000