Fix Insecure API Management in Micronaut

Micronaut's high-performance footprint often leads developers to overlook the management layer, leaving sensitive endpoints like /beans, /env, or /refresh wide open. Insecure API management in Micronaut typically stems from permissive security rules, lack of rate limiting, and exposing internal state through unauthenticated management beans. If an attacker hits your /env endpoint, they've got your DB credentials and API keys. We're going to harden this surface using Micronaut Security and granular endpoint configuration.

The Vulnerable Pattern

// application.yml - The 'I want to be pwned' config
endpoints:
  all:
    enabled: true
    sensitive: false # This exposes sensitive metadata to the public
// Vulnerable Controller - No authentication enforced
@Controller(“/admin”)
public class AdminController {
@Get(“/stats”)
public Map<String, Object> getStats() {
return Map.of(“status”, “live”, “internal_ip”, “10.0.0.5”);
}
}

The Secure Implementation

The fix involves three layers of defense. First, we enable 'micronaut-security' and toggle 'sensitive: true' globally for all management endpoints in the YAML config; this ensures no metadata leaks without a valid token. Second, we move from anonymous access to explicit authorization using the '@Secured' annotation, restricting high-risk endpoints to specific roles (e.g., ROLE_ADMIN). Finally, we externalize secrets like the JWT generator key to environment variables rather than hardcoding them, preventing credential exposure in the codebase.

// application.yml - Hardened Config
micronaut:
  security:
    enabled: true
    token:
      jwt:
        enabled: true
        signatures:
          secret:
            generator:
              secret: "${JWT_GENERATOR_SECRET}"
  endpoints:
    all:
      enabled: true
      sensitive: true # Forces authentication for all management endpoints
// Secure Controller - Enforcing Role-Based Access Control (RBAC)
@Secured(“ROLE_ADMIN”)
@Controller(“/admin”)
public class AdminController {
@Get(“/stats”)
public Map<String, Object> getStats() {
return Map.of(“status”, “secure”);
}
}