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Spring Security 6 & JWT Authentication · 강의

안전한 토큰 저장 방법

일반적인 공격을 방지하기 위해 클라이언트 측에 JWT와 리프레시 토큰을 저장하는 모범 사례를 이해합니다.

안전한 토큰 저장 방법은(는) CoddyKit의 무료 Spring Security 6 & JWT Authentication 강의입니다. 이것은 4개 중 3번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Spring Security 6 & JWT Authentication 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Spring Security 6 & JWT Authentication 강의에는 총 4개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

Why Secure Token Storage Matters

When building secure applications with JWTs, where you store these tokens on the client-side is crucial. Improper storage can expose your users to various security risks.

This lesson explores the best practices for handling JWTs and refresh tokens in client environments like web browsers, ensuring your application remains robust against common attacks.

Client-Side Storage Options

Web browsers offer several ways to store data, each with different security implications for sensitive tokens:

  • LocalStorage: Stores data persistently across browser sessions.
  • SessionStorage: Stores data only for the duration of the browser session.
  • Cookies: Small pieces of data sent by the server and stored by the browser, sent back with subsequent requests.

Choosing the right option is key to token security.

LocalStorage & SessionStorage Risks

While convenient, LocalStorage and SessionStorage are generally not recommended for storing sensitive JWTs or refresh tokens.

They are vulnerable to Cross-Site Scripting (XSS) attacks. If a malicious script is injected into your page, it can easily access and steal any tokens stored here.

XSS: The Token Thief

Cross-Site Scripting (XSS) is a common web security vulnerability. It allows attackers to inject malicious client-side scripts into web pages viewed by other users.

These scripts can then:

  • Access and steal data from LocalStorage or SessionStorage.
  • Perform actions on behalf of the user.
  • Even hijack user sessions.

This is why tokens in these storages are at high risk.

Introducing HTTP-Only Cookies

For better protection against XSS, HTTP-Only cookies are a strong choice, especially for refresh tokens. An HTTP-Only cookie cannot be accessed by client-side JavaScript.

This means even if an XSS attack occurs, the malicious script cannot read or steal the cookie's content, significantly reducing the risk of token compromise.

Essential Cookie Security Flags

Beyond HTTP-Only, two other flags are critical for cookie security:

  • Secure: Ensures the cookie is only sent over HTTPS connections. Never use sensitive cookies without this flag in production.
  • SameSite: Prevents the browser from sending the cookie with cross-site requests, providing robust protection against Cross-Site Request Forgery (CSRF) attacks.

Always use Secure and a suitable SameSite policy (e.g., Lax or Strict).

Setting a Secure Cookie in Spring

Here's how a Spring Boot backend can set an HTTP-Only, Secure, and SameSite cookie. This cookie would typically hold a refresh token.

The browser automatically handles sending this cookie with subsequent requests to your domain, while JavaScript cannot access it.

import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class CookieController {

    @GetMapping("/set-secure-cookie")
    public String setSecureCookie(HttpServletResponse response) {
        Cookie refreshTokenCookie = new Cookie("refreshToken", "your_long_refresh_token");
        refreshTokenCookie.setHttpOnly(true); // JS cannot access
        refreshTokenCookie.setSecure(true);   // Only over HTTPS
        refreshTokenCookie.setMaxAge(7 * 24 * 60 * 60); // 7 days
        refreshTokenCookie.setPath("/");
        // Set SameSite to Lax or Strict for CSRF protection
        // Note: For Spring, SameSite often set via application properties
        // or a custom filter for older Servlet versions.
        // With modern Servlet API (e.g., Servlet 4+), can be set directly:
        // refreshTokenCookie.setAttribute("SameSite", "Lax");

        response.addCookie(refreshTokenCookie);
        return "Secure cookie set!";
    }

    public static void main(String[] args) {
        // This is a conceptual example for a Spring Controller.
        // A full Spring Boot app would run this via SpringApplication.run().
        // The main method here is just for completeness as per guidelines,
        // but this code needs a Spring context to fully execute.
        System.out.println("To run, integrate into a Spring Boot application.");
    }
}

Access Token Storage: In-Memory

Access tokens are typically short-lived. The most secure place for an access token on the client-side is often in-memory (e.g., a JavaScript variable).

This means the token is not written to persistent storage and is lost when the browser tab is closed or the page is refreshed. It minimizes exposure, as an XSS attack would only be able to steal the token while the user is actively on the compromised page.

The Combined Secure Strategy

A robust strategy combines the best of both worlds:

  • Access Token: Store in a JavaScript variable (in-memory). Send it in the Authorization header for API requests. It's short-lived.
  • Refresh Token: Store in an HTTP-Only, Secure, SameSite cookie. This token is used to obtain new access tokens when the current one expires. It's longer-lived and highly protected.

This approach balances usability with strong security against XSS and CSRF.

Check Your Knowledge

Which of the following are considered best practices for securely storing JWTs and refresh tokens on the client-side?

Recap: Secure Storage Principles

You've learned critical strategies for secure client-side token storage:

  • Avoid LocalStorage/SessionStorage for sensitive tokens due to XSS risks.
  • Use HTTP-Only, Secure, SameSite cookies for refresh tokens to protect against XSS and CSRF.
  • Keep access tokens in-memory (JavaScript variables) as they are short-lived.

By following these practices, you significantly enhance the security posture of your JWT-based authentication system.

자주 묻는 질문

“안전한 토큰 저장 방법” 강의는 무료인가요?

네 — “안전한 토큰 저장 방법” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Spring Security 6 & JWT Authentication 강의 전체를 잠금 해제할 수 있습니다. Spring Security 6 & JWT Authentication 강의에는 총 4개의 강의가 포함되어 있습니다.

“안전한 토큰 저장 방법”에서 뭘 배우나요?

일반적인 공격을 방지하기 위해 클라이언트 측에 JWT와 리프레시 토큰을 저장하는 모범 사례를 이해합니다. 브라우저에서 직접 실행하는 실습 코드로 Spring Security 6 & JWT Authentication을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.

Spring Security 6 & JWT Authentication을(를) 시작하는 데 경험이 필요한가요?

사전 경험은 필요하지 않습니다. CoddyKit의 Spring Security 6 & JWT Authentication은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 3번째 강의입니다.

“안전한 토큰 저장 방법” 강의는 얼마나 걸리나요?

대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.

이 Spring Security 6 & JWT Authentication 강의에서 코드를 작성하고 실행할 수 있나요?

네. 모든 Spring Security 6 & JWT Authentication 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.

이 강의의 모든 강의

  1. 리프레시 토큰 구현
  2. JWT 토큰 폐기 전략
  3. 안전한 토큰 저장 방법
  4. 서명 키 교체 및 키 관리
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