Authentication and Authorization

In building full-stack web applications, you will more than often want to implement a system that allows users to trust you with their sensitive information. As a full-stack web developer, it is crucial to understand how to implement robust authentication and authorization mechanisms. You need to know how to protect the security of user data and the integrity of your application. Imagine you are building an e-commerce website that allows users to make online purchases.

If you do not properly authenticate and authorize users, it would be possible for someone to gain unauthorized access to the website and place orders using someone else’s personal information. This could result in financial loss for the legitimate user as well as damage to the reputation of an online business or that of your clients.

Furthermore, if you fail to properly authenticate and authorize users, it could also open your web application up to attacks such as SQL injection...

Technical requirements

The complete code for this chapter is available on GitHub at: https://github.com/PacktPublishing/Full-Stack-Flask-and-React/tree/main/Chapter12.

Understanding the fundamentals of information security

Information security is a critical aspect of web application development. In today’s digital age, personal and sensitive information is often stored and transmitted through web applications, making them vulnerable to various types of security threats. These threats can range from simple attacks such as SQL injection and cross-site scripting (XSS) to more complex attacks such as man-in-the-middle (MITM) and distributed denial of service (DDoS).

Let’s delve deeper into some of the various types of threats that can compromise your web application security:

• SQL injection: This is a type of cyberattack in which an attacker injects malicious SQL code into an application’s input fields to trick the application into executing unintended database actions. This can lead to unauthorized access, data manipulation, or even data leakage.

  For instance, consider a web application login form where a user enters their...

Defining authentication and the authentication role in web application

Authentication is the process of verifying the identity of a user and ensuring that only authorized users have access to the application’s resources and functionality. Authentication is an important aspect of any web application, including those built with Flask.

This is typically done by prompting the user to provide a set of credentials, such as a username and password, that the web application can use to confirm the user’s identity. The purpose of authentication in web application development is to ensure that only authorized users can access sensitive information and perform certain actions within a web application.

In web development, we have several types of authentication methods that can be used in any web application project. These are some of the most commonly used methods:

• Password-based authentication: This is the most common form of authentication we encounter in everyday...

Implementing password security and hashing passwords

In any web application that requires access, passwords are often the first line of defense against unauthorized access. As a developer, you will want to ensure that passwords are securely managed when building Flask applications. A critical component of password management in web applications is to never store passwords in plaintext.

Instead, passwords should be hashed, which is a one-way encryption process that produces a fixed-length output that cannot be reversed. When a user enters their password, it is hashed and compared with the stored hash. If the two hashes match, the password is correct. Hashing passwords can help protect against attacks such as brute-force and dictionary attacks.

Brute-force attacks involve trying every possible combination of characters to find a match, while dictionary attacks involve trying a pre-computed list of words. Hashing passwords makes it computationally infeasible for an attacker to reverse...

Understanding access and authorization in web application development

Access and authorization in web application development is the process of controlling who has access to specific resources and actions within a web application. As a developer, you will want to design and ensure that users can only perform actions they are authorized to perform and access resources they are authorized to access in a web application.

As discussed earlier, authentication is the process of verifying the identity of a user. Authorization is the process of determining what a user is allowed to do within a web application. When you combine these two mechanisms, you have a system that ensures that only authorized users can access sensitive information and perform certain actions within a web application.

Several different types of access control methods can be used in web application development. We will discuss some of them and make specific reference to how Flask can handle access and authorization...

Adding authentication to your Flask application

JWT is a popular method for authentication in modern web applications. A JWT is a JSON object that is digitally signed and can be used to authenticate users by transmitting claims between parties, such as an authorization server and a resource server. In a Flask web application, you can use the PyJWT library to encode and decode JWTs for authentication.

When a user logs into a Flask application, the backend verifies the user’s credentials, such as their email and password, and if they are valid, a JWT is generated and sent back to the client. The client stores the JWT in the browser’s local storage or as a cookie. For subsequent requests to protected routes and resources, the client sends the JWT in the request header.

The backend decodes the JWT to verify the user’s identity, grants or denies access to the requested resources, and generates a new JWT for subsequent requests. JWT for authentication allows stateless...

Identifying system users and managing their information

In most web applications, users are identified by a unique identifier such as a username or email address. Typically, in a Flask application, you can use a database to store user information, such as usernames, email addresses, and hashed passwords.

When a user attempts to log in, the entered credentials (username and password) are compared to the information stored in the database. If the entered credentials match, the user is authenticated, and a session is created for that user. In Flask, you can use the built-in session object to store and retrieve user information.

By using sessions, you can easily identify users in a Flask web application and retrieve information about them. However, it’s important to note that sessions are vulnerable to session hijacking attacks. So, it’s essential to use secure session management techniques such as regenerating session IDs after login and using secure cookies.

Let...

Session management

Session management is a critical aspect of web development as it enables a web application to identify and track a user’s actions over a certain period. In Flask web applications, session management is typically implemented on the server side using Flask’s in-built session object or a Flask extension such as Flask-Session; on the frontend React side, you can use React’s localStorage or sessionStorage.

Flask thrives on its simplicity as a framework of choice for Python that makes it easy to build small to enterprise-sized web applications. Flask can manage user sessions using the built-in session object and some of the available Flask extensions contributed by the community members.

A session object is a dictionary-like object that is stored on the server and can be accessed by the client via a secure session cookie. To use a session object, a secret key must be set in the Flask application. This secret key is used to encrypt and sign the...

Creating a password-protected dashboard

Protecting pages in a web application is essential for maintaining security and privacy. By extension, this can help prevent unauthorized access to sensitive information. In this section, you will be implementing a protected dashboard page in a Flask-React web application.

A dashboard is a user-friendly interface that provides an overview of data and information. The data that’s displayed on a dashboard can come from a variety of sources, such as databases, spreadsheets, and APIs.

Flask backend

The following code demonstrates an implementation that allows an admin user to log in and see a protected dashboard page. We will implement minimalist login and logout endpoints that define login and logout functionality and protect the dashboard endpoint. The application uses the Flask-Session library to store session data in the filesystem:

from flask import Flask, request, jsonify, sessionfrom flask_session import Session
app = Flask...

Implementing flash messages in Flask

Flash messages enhance the user experience in any web application, providing informative and timely feedback to users. Flash is used to display status or error messages on web pages after a redirect. For instance, after a successful form submission, a message can be stored in the flash to display a success message on the redirected page.

The flash message is stored in the user’s session, which is a dictionary-like object that can store information between requests. With flash messages, you can pass information between requests securely and efficiently. This is useful for displaying messages that don’t need to persist for a long time or that need to be shown only once, such as success or error messages. Since flash messages are stored in the user’s session, they are only accessible by the server and are not sent to the client in plain text, making them secure.

Let’s modify the login and logout endpoints to show flash...

Summary

This chapter has provided a comprehensive overview of the fundamentals of information security and how to secure a Flask web application using authentication and authorization. You learned about the best practices and were provided with use cases for implementing authentication and authorization in a Flask application. We also discussed different types of authentication methods and access control methods.

You explored how to manage user sessions and implement password-protected dashboards. Additionally, this chapter has shown you how to use flash messages to provide feedback to users of web applications. You are expected to have garnered a solid understanding of how to secure a Flask application and be able to implement authentication and authorization in your projects.

In the next chapter, we will discuss how to handle errors in Flask web applications with React handling the frontend part of it. We will delve into in-built Flask debugging capabilities and learn how to...