Spring Security 6 & JWT Authentication · レッスン

JWTのブラックリストとホワイトリスト

トークンのブラックリストやホワイトリストを管理する方法を含め、高度なトークン失効技術を詳しく学びます。

「JWTのブラックリストとホワイトリスト」はCoddyKit上の無料Spring Security 6 & JWT Authenticationレッスンです。これはレッスン2/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはSpring Security 6 & JWT Authentication学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Spring Security 6 & JWT Authenticationコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Why Revoke JWTs?

JSON Web Tokens (JWTs) are powerful for authentication, but sometimes you need to invalidate them before their natural expiry. This process is called token revocation.

Compromised Token: If a token is stolen.
User Logout: To immediately end a user's session.
Password Change: To invalidate all old tokens.
Role Changes: To force re-authentication with new permissions.

The Stateless Challenge

JWTs are inherently stateless. Once issued, they contain all necessary information for validation and don't require the server to store session data.

This statelessness is a strength, but it makes direct server-side revocation tricky. The server typically doesn't hold a list of active tokens to simply 'turn off'.

Blacklisting Explained

Blacklisting is a common strategy to revoke JWTs. When a token needs to be invalidated, its unique identifier (often the JTI claim) is added to a 'blacklist' — a list of forbidden tokens.

Any token whose JTI is on this list is rejected, even if it's cryptographically valid and not expired.
This allows you to 'undo' a token's validity.

Implementing a Blacklist

The blacklist needs to be stored in a highly available, fast-access data store. Speed is crucial because every incoming request might need to check this list.

Redis: An excellent choice due to its in-memory nature and support for time-to-live (TTL) on entries, which can match token expiry.
Database: A simple table can work, but might be slower for high-volume checks.
Each entry typically stores the JWT's JTI and its original expiry time.

Simple Blacklist Service

Here's a basic interface for a service that manages a token blacklist. In a real application, this would interact with a database or a caching system like Redis.

public interface TokenBlacklistService {
  void blacklistToken(String jti, long expirySeconds);
  boolean isBlacklisted(String jti);
}

JWT Filter with Blacklist Check

When a request arrives, a security filter would first validate the JWT's signature and expiry. Then, it would check if the token's JTI is present on the blacklist before granting access.

Try running this example:

import java.util.HashSet;
import java.util.Set;

// A simplified in-memory blacklist for demonstration
class MockTokenBlacklistService {
    private Set<String> blacklistedJtis = new HashSet<>();

    public void blacklistToken(String jti, long expirySeconds) {
        System.out.println("Action: Blacklisting JTI " + jti);
        blacklistedJtis.add(jti);
        // In a real app, 'expirySeconds' would set a TTL on the blacklist entry
    }

    public boolean isBlacklisted(String jti) {
        boolean result = blacklistedJtis.contains(jti);
        System.out.println("Check: Is JTI " + jti + " blacklisted? " + result);
        return result;
    }
}

public class Main {
    public static void main(String[] args) {
        MockTokenBlacklistService blacklist = new MockTokenBlacklistService();

        String userTokenJti = "user-abc-123";
        String adminTokenJti = "admin-def-456";

        // Simulate an admin token being revoked after a security event
        blacklist.blacklistToken(adminTokenJti, 3600); // Token expires in 1 hour

        // Check access for different tokens
        System.out.println("\n--- Access Checks ---");
        System.out.println("User token access: " + (blacklist.isBlacklisted(userTokenJti) ? "DENIED" : "GRANTED"));
        System.out.println("Admin token access: " + (blacklist.isBlacklisted(adminTokenJti) ? "DENIED" : "GRANTED"));
    }
}

Whitelisting Explained

Whitelisting is an alternative revocation strategy. Instead of listing forbidden tokens, you maintain a list of active, allowed tokens.

When a token is issued, its JTI is added to a 'whitelist'.
For every request, the token's JTI must be found on this whitelist to be considered valid.
If a token's JTI is not on the whitelist, it's rejected.

Implementing a Whitelist

Similar to blacklisting, a whitelist requires a fast, persistent store (e.g., Redis). The key difference is what you store and how you manage it:

Each entry typically stores the JWT's JTI, often associated with a user ID.
When a user logs out or changes their password, all active JTIs associated with that user can be efficiently removed from the whitelist.

Blacklist vs. Whitelist Comparison

Both strategies achieve revocation but have different implications:

Blacklist: Ideal for rare, specific revocations (e.g., single token compromise). Requires less storage if revocations are infrequent.
Whitelist: Better for frequent revocations (e.g., user logout invalidates all tokens). Can simplify session management but requires more storage for all active tokens.
The choice depends on your application's specific needs and the frequency of revocations.

Revocation Scenario

Consider an application where users frequently log out, and you need to ensure all their issued tokens are immediately invalidated upon logout.

Recap: Revocation Strategies

In this lesson, we've explored advanced strategies for revoking JWTs, which is crucial for robust security:

Blacklisting: Marking specific tokens as invalid by adding their JTI to a forbidden list.
Whitelisting: Only allowing tokens that are explicitly listed as active, often tied to a user session.
The best approach depends on your application's requirements, especially the frequency and nature of token invalidation.

Next, we'll analyze the performance implications of these techniques.

よくある質問

「JWTのブラックリストとホワイトリスト」レッスンは無料ですか？

はい。「JWTのブラックリストとホワイトリスト」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Spring Security 6 & JWT Authenticationコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Spring Security 6 & JWT Authenticationコースには全4レッスンが含まれています。

「JWTのブラックリストとホワイトリスト」で何を学びますか？

トークンのブラックリストやホワイトリストを管理する方法を含め、高度なトークン失効技術を詳しく学びます。ブラウザで直接実行するハンズオンコードでSpring Security 6 & JWT Authenticationを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Spring Security 6 & JWT Authenticationを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのSpring Security 6 & JWT Authenticationは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン2/4です。

「JWTのブラックリストとホワイトリスト」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このSpring Security 6 & JWT Authenticationレッスンでコードを書いて実行できますか？

はい。すべてのSpring Security 6 & JWT Authenticationレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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