System Design Basics for Backend Developers · 课时

身份认证与授权

实现可靠的身份认证和授权机制，以控制对系统资源的访问

第 1 / 4 课11 个步骤

身份认证与授权 是 CoddyKit 上的免费 System Design Basics for Backend Developers 课时。这是第 1 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 System Design Basics for Backend Developers 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 System Design Basics for Backend Developers 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Auth vs. Auth: The Basics

In system design, authentication and authorization are critical for security. They control who can access your system and what they can do.

Authentication (AuthN) verifies who you are.
Authorization (AuthZ) determines what you're allowed to do.

Think of it like a club: authentication is checking your ID at the door, authorization is seeing if you have a VIP pass to enter special areas.

What is Authentication?

Authentication is the process of proving your identity to a system. This confirms that you are who you claim to be.

Common authentication methods include:

Password-based: Username and password.
Multi-factor: Combining passwords with codes from an app or SMS.
Biometric: Fingerprints or facial recognition.
Token-based: Using a cryptographic token after initial login.

Token-Based Authentication

Token-based authentication is popular for web and mobile apps. After a user logs in (authenticates) with credentials, the server issues a token.

This token is then sent with every subsequent request to prove the user's identity without sending credentials repeatedly. A common type is the JSON Web Token (JWT).

Understanding JWTs

A JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between two parties. It's often used to authenticate users.

JWTs consist of three parts, separated by dots:

Header: Type of token and signing algorithm.
Payload: Claims (user ID, roles, expiration).
Signature: Used to verify the token hasn't been tampered with.

It looks something like this:

eyJhbGciOiJIUzI1NiJ9.eyJ1c2VySWQiOiIxMjMiLCJyb2xlIjoiYWRtaW4ifQ.SFLS...

Simple Token Check Demo

When a client sends a request with a token, the server must validate it. This often involves checking the signature and expiration.

Here's a very simplified conceptual example of how a server might check if a token is known, representing a basic validation step:

public class TokenChecker {
  public static void main(String[] args) {
    String userToken = "validUserToken123";
    String adminToken = "adminSecretToken456";
    String invalidToken = "badToken";

    System.out.println("User Token Check: " + isValid(userToken));
    System.out.println("Admin Token Check: " + isValid(adminToken));
    System.out.println("Invalid Token Check: " + isValid(invalidToken));
  }

  // A very simplified conceptual token validation
  public static boolean isValid(String token) {
    if (token.equals("validUserToken123") || token.equals("adminSecretToken456")) {
      return true; // Token is conceptually 'valid'
    }
    return false; // Token is not recognized
  }
}

What is Authorization?

Authorization is the process of determining what an authenticated user or system is permitted to do.

For example, a regular user might be able to view their own profile, but only an administrator can delete user accounts. Authorization answers the question: "Are you allowed to do that?"

Role-Based Access Control (RBAC)

One common authorization model is Role-Based Access Control (RBAC). In RBAC, permissions are associated with roles, and users are assigned to roles.

Users: Individuals or systems.
Roles: Collections of permissions (e.g., 'Admin', 'Editor', 'Viewer').
Permissions: Specific actions on resources (e.g., 'read_post', 'edit_user').

This simplifies managing access, as you assign users to roles rather than individual permissions.

Policy-Based Authorization

For more complex scenarios, Policy-Based Authorization (like Attribute-Based Access Control or ABAC) allows for very fine-grained control.

Instead of just roles, access decisions are based on attributes of the user, the resource, the environment, and the action itself. This offers greater flexibility but can be more complex to manage.

AuthN and AuthZ Together

Authentication and authorization work hand-in-hand in a typical request flow:

A user tries to access a resource.
The system authenticates the user (e.g., validates their token). If invalid, access is denied.
If authenticated, the system then authorizes the user: it checks if the user's role or attributes grant them permission for that specific action on that resource.
If authorized, access is granted. Otherwise, it's denied.

Identify the Concepts

Which of the following statements correctly describe the concepts of Authentication and Authorization?

在交互式课程中回答

Recap: Securing Access

We've explored the crucial difference between authentication (who you are) and authorization (what you can do).

You learned about token-based authentication with JWTs and authorization models like RBAC. Understanding these concepts is fundamental to designing secure and robust systems.

Keep practicing these distinctions as you design systems that need to control access effectively!

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常见问题解答

「身份认证与授权」课时是免费的吗？

是的 — 「身份认证与授权」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 System Design Basics for Backend Developers 课程的其余内容，请升级到 CoddyKit PRO。 System Design Basics for Backend Developers 课程共包含 4 节课。

「身份认证与授权」这节课中我会学到什么？

实现可靠的身份认证和授权机制，以控制对系统资源的访问你通过在浏览器中直接运行的动手代码来练习 System Design Basics for Backend Developers，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 System Design Basics for Backend Developers 需要有经验吗？

无需任何先前经验。CoddyKit 上的 System Design Basics for Backend Developers 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 1 节课，共 4 节。

「身份认证与授权」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 System Design Basics for Backend Developers 课中编写并运行代码吗？

能。每节 System Design Basics for Backend Developers 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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