Listas negras y blancas de JWT
Profundice en técnicas avanzadas de revocación de tokens, incluido el mantenimiento de listas negras o blancas de tokens.
Listas negras y blancas de JWT es una lección gratuita de Spring Security 6 & JWT Authentication en CoddyKit. Esta es la lección 2 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de Spring Security 6 & JWT Authentication, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de Spring Security 6 & JWT Authentication incluye 4 lecciones en total.
Partes de esta lección aún no han sido traducidas y se muestran en inglés.
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.
Aprende Java con un tutor de IA — gratis
Escribe y ejecuta código real en tu navegador, obtén ayuda instantánea de un tutor de IA disponible 24/7 y continúa donde lo dejaste en la web o en la aplicación.
- Cursos
- 12
- Lecciones
- 48
Preguntas frecuentes
¿La lección «Listas negras y blancas de JWT» es gratis?
Sí — el texto completo de «Listas negras y blancas de JWT» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de Spring Security 6 & JWT Authentication, actualiza a CoddyKit PRO. El curso de Spring Security 6 & JWT Authentication incluye 4 lecciones en total.
¿Qué aprenderé en «Listas negras y blancas de JWT»?
Profundice en técnicas avanzadas de revocación de tokens, incluido el mantenimiento de listas negras o blancas de tokens. Practicas Spring Security 6 & JWT Authentication con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.
¿Necesito experiencia previa para empezar Spring Security 6 & JWT Authentication?
No se requiere experiencia previa. Spring Security 6 & JWT Authentication en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 2 de 4.
¿Cuánto tiempo toma la lección «Listas negras y blancas de JWT»?
La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.
¿Puedo escribir y ejecutar código en esta lección de Spring Security 6 & JWT Authentication?
Sí. Cada lección de Spring Security 6 & JWT Authentication incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.
Todas las lecciones de este curso
- JWT de corta duración y ciclo de actualización
- Listas negras y blancas de JWT
- Consideraciones de rendimiento para JWT
- Almacenamiento en caché de la validación de tokens para escalar