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Spring Security 6 & JWT Authentication · レッスン

パスワードエンコーダーの理解

Spring Securityで利用できるさまざまなパスワードエンコーダーと、安全なパスワード保存における重要性を学びます。

「パスワードエンコーダーの理解」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 Encode Passwords?

Imagine storing your password in a simple text file. Anyone who gains access to that file can immediately see and use your password.

This is a major security risk! In web applications, we never store user passwords in plain, readable text.

Hashing vs. Encryption

When we talk about securing passwords, we use a technique called hashing, not encryption. What's the difference?

  • Encryption: Reversible process. You can encrypt data and later decrypt it back to its original form using a key.
  • Hashing: One-way process. You transform data into a fixed-size string (a hash) that is extremely difficult to reverse. There's no 'decrypting' a hash.

Hashing ensures that even if a database is breached, attackers only get hashes, not actual passwords.

Spring Security's Role

Spring Security provides powerful tools to handle password encoding correctly and securely. It uses a special component called a Password Encoder.

This encoder takes a plain-text password and converts it into a secure hash before storing it. When a user tries to log in, Spring Security encodes their entered password and compares the new hash with the stored hash.

The PasswordEncoder Interface

At the core of Spring Security's password handling is the PasswordEncoder interface. Any class that implements this interface can be used to encode and verify passwords.

It defines two main methods:

  • encode(CharSequence rawPassword): Creates a hash of the raw password.
  • matches(CharSequence rawPassword, String encodedPassword): Checks if a raw password matches an encoded password.

Introducing BCryptPasswordEncoder

One of the most widely recommended and secure password encoders in Spring Security is BCryptPasswordEncoder.

Why is BCrypt so good?

  • Salting: It automatically adds a random 'salt' to each password before hashing, making identical passwords produce different hashes.
  • Adaptive Hashing: It's designed to be computationally intensive, which slows down brute-force attacks. You can even configure its 'strength'.

Encoding a Password with BCrypt

Let's see BCryptPasswordEncoder in action. We'll create an instance and use its encode() method.

Notice how the output is different each time, even for the same input, thanks to salting!

import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;

public class PasswordEncoderDemo {
  public static void main(String[] args) {
    BCryptPasswordEncoder encoder = new BCryptPasswordEncoder();
    String rawPassword = "mysecretpassword";

    String encodedPassword1 = encoder.encode(rawPassword);
    String encodedPassword2 = encoder.encode(rawPassword);

    System.out.println("Encoded 1: " + encodedPassword1);
    System.out.println("Encoded 2: " + encodedPassword2);
  }
}

Verifying a Password with BCrypt

When a user attempts to log in, you don't re-encode their password and compare the strings directly. Instead, you use the matches() method.

This method takes the raw password entered by the user and the stored encoded password, then performs the necessary checks securely.

import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;

public class PasswordVerifierDemo {
  public static void main(String[] args) {
    BCryptPasswordEncoder encoder = new BCryptPasswordEncoder();
    String rawPassword = "userpass";
    String storedEncodedPassword = encoder.encode(rawPassword);

    System.out.println("Stored Encoded: " + storedEncodedPassword);

    // Simulate login attempt with correct password
    boolean matchesCorrect = encoder.matches("userpass", storedEncodedPassword);
    System.out.println("Matches 'userpass': " + matchesCorrect);

    // Simulate login attempt with incorrect password
    boolean matchesIncorrect = encoder.matches("wrongpass", storedEncodedPassword);
    System.out.println("Matches 'wrongpass': " + matchesIncorrect);
  }
}

Other Secure Encoders

While BCrypt is very common, Spring Security also supports other strong password hashing algorithms. These include:

  • Pbkdf2PasswordEncoder: Uses PBKDF2 (Password-Based Key Derivation Function 2).
  • SCryptPasswordEncoder: Based on scrypt, designed to be resistant to GPU-based attacks.
  • Argon2PasswordEncoder: Uses Argon2, winner of the Password Hashing Competition.

These all serve the same purpose: securely hashing passwords to prevent easy cracking.

DelegatingPasswordEncoder

Spring Security 5.0 introduced DelegatingPasswordEncoder as the default. This is a very important concept!

It allows you to:

  • Support multiple encoding formats simultaneously (e.g., if you're migrating from an older algorithm).
  • Define a default encoder while still being able to verify passwords encoded with other algorithms.

It prefixes the encoded password with an identifier (e.g., {bcrypt}) to indicate which algorithm was used.

Quick Check: Password Security

You've learned about the importance of password encoding. Let's test your understanding!

Recap: Secure Password Storage

In this lesson, we explored the critical role of password encoders in Spring Security:

  • Passwords must always be hashed, not encrypted, for secure storage.
  • The PasswordEncoder interface defines how passwords are encoded and verified.
  • BCryptPasswordEncoder is a strong, recommended encoder that uses salting and adaptive hashing.
  • DelegatingPasswordEncoder allows for flexible support of multiple hashing algorithms.

Proper password encoding is fundamental to protecting user accounts in any application.

よくある質問

「パスワードエンコーダーの理解」レッスンは無料ですか？

はい。「パスワードエンコーダーの理解」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。

「パスワードエンコーダーの理解」で何を学びますか？

Spring Securityで利用できるさまざまなパスワードエンコーダーと、安全なパスワード保存における重要性を学びます。 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。

「パスワードエンコーダーの理解」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。

このコースのすべてのレッスン

  1. カスタムUserDetailsServiceの実装
  2. パスワードエンコーダーの理解
  3. データベースとのユーザー管理統合
  4. Granted Authoritiesによるロールベース認可
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