Understanding Authentication and Authorization Elixir

What You’ll Learn 📚

• The difference between authentication and authorization
• Key terminology and concepts
• Step-by-step examples from simple to complex
• Common questions and troubleshooting tips

Introduction to Authentication and Authorization

In the world of web applications, authentication and authorization are crucial concepts. Simply put, authentication is about verifying who you are, while authorization is about what you can do. Think of it like this: when you enter a building, showing your ID at the door is authentication, and being allowed to access certain rooms is authorization.

Key Terminology

• Authentication: The process of verifying the identity of a user.
• Authorization: The process of determining what resources a user can access.
• Token: A digital key used to authenticate a user.
• Session: A temporary state that allows a user to remain authenticated over multiple requests.

Getting Started with Elixir

Before we jump into examples, make sure you have Elixir installed on your machine. You can check this by running:

elixir -v

If you see the version number, you’re good to go! If not, follow the official installation guide.

Simple Authentication Example

defmodule SimpleAuth do  def authenticate(user, password) do    if user == "student" and password == "elixir" do      {:ok, "Welcome, #{user}!"}    else      {:error, "Invalid credentials."}    end  endend

{:ok, "Welcome, student!"}

Progressively Complex Examples

Example 1: Using Tokens

defmodule TokenAuth do  def authenticate(user, password) do    if user == "student" and password == "elixir" do      {:ok, generate_token(user)}    else      {:error, "Invalid credentials."}    end  end  defp generate_token(user) do    "token_for_#{user}"  endend

{:ok, "token_for_student"}

Example 2: Authorization Check

defmodule AuthWithRoles do  def authenticate(user, password) do    if user == "admin" and password == "elixir" do      {:ok, "admin_token"}    else      {:error, "Invalid credentials."}    end  end  def authorize(token, resource) do    if token == "admin_token" and resource == "admin_panel" do      {:ok, "Access granted to #{resource}."}    else      {:error, "Access denied."}    end  endend

{:ok, "Access granted to admin_panel."}

Example 3: Handling Sessions

defmodule SessionAuth do  def authenticate(user, password) do    if user == "student" and password == "elixir" do      {:ok, start_session(user)}    else      {:error, "Invalid credentials."}    end  end  defp start_session(user) do    "session_for_#{user}"  end  def check_session(session) do    if session == "session_for_student" do      {:ok, "Session is valid."}    else      {:error, "Invalid session."}    end  endend

{:ok, "Session is valid."}

Common Questions and Answers

1. What is the difference between authentication and authorization?

   Authentication verifies identity, while authorization determines access rights.

2. Why use tokens for authentication?

   Tokens provide a secure and stateless way to authenticate users across multiple requests.

3. How do sessions differ from tokens?

   Sessions maintain state on the server, while tokens are stateless and can be used across different servers.

4. Can I use both sessions and tokens?

   Yes, combining both can provide flexibility and security, depending on your application’s needs.

5. What are common pitfalls in authentication?

   Common pitfalls include weak passwords, insecure token storage, and improper session management.

Troubleshooting Common Issues

Ensure your Elixir environment is correctly set up before running examples.

• Issue: Invalid credentials error.
  Solution: Double-check the username and password being used.
• Issue: Access denied error.
  Solution: Verify the token and resource being accessed.
• Issue: Invalid session error.
  Solution: Ensure the session token is correctly generated and stored.

Practice Exercises

1. Create a new authentication module that uses email and password instead of username.
2. Implement a logout function that invalidates a session.
3. Extend the authorization example to include multiple roles and resources.

Remember, practice makes perfect! Keep experimenting with different scenarios to solidify your understanding. 💪

For further reading, check out the Elixir documentation and explore more about authentication libraries like Guardian.