fix(security): fail closed Config Server reads by default

config-server/pom.xml

@@ -21,6 +21,10 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-actuator</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-security</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

config-server/src/main/java/com/xtrmetl/config/ConfigServerSecurityConfiguration.java

@@ -0,0 +1,43 @@
+package com.xtrmetl.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.web.SecurityFilterChain;
+
+/**
+ * Defines the credential-free fail-closed HTTP posture for the reference-only Config Server.
+ *
+ * <p>The repository does not invent a production service identity. Until a deployment-owned
+ * authentication mechanism is selected and proven under issue #193, only health and info actuator
+ * endpoints are intentionally public and every configuration-resource request is denied. A future
+ * authenticated production profile must replace this reference-only posture through a separately
+ * reviewed security contract rather than weakening this default.</p>
+ */
+@Configuration(proxyBeanMethods = false)
+public class ConfigServerSecurityConfiguration {
+
+    /**
+     * Builds the reference-only Config Server security chain.
+     *
+     * @param http Spring Security's servlet HTTP configuration builder
+     * @return the configured filter chain
+     * @throws Exception when Spring Security cannot build the filter chain
+     */
+    @Bean
+    public SecurityFilterChain configServerSecurityFilterChain(HttpSecurity http) throws Exception {
+        http
+                .csrf(csrf -> csrf.disable())
+                .httpBasic(httpBasic -> httpBasic.disable())
+                .formLogin(formLogin -> formLogin.disable())
+                .logout(logout -> logout.disable())
+                .authorizeHttpRequests(authorize -> authorize
+                        .requestMatchers(
+                                "/actuator/health",
+                                "/actuator/health/**",
+                                "/actuator/info"
+                        ).permitAll()
+                        .anyRequest().denyAll());
+        return http.build();
+    }
+}

config-server/src/test/java/com/xtrmetl/config/ConfigServerInboundSecurityTest.java

@@ -0,0 +1,37 @@
+package com.xtrmetl.config;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Verifies the fail-closed inbound HTTP boundary for the reference-only Config Server profile.
+ */
+@SpringBootTest(
+        classes = ConfigServerApplication.class,
+        webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
+        properties = {
+                "spring.profiles.active=native",
+                "spring.cloud.config.server.native.search-locations=classpath:/",
+                "eureka.client.enabled=false"
+        }
+)
+class ConfigServerInboundSecurityTest {
+
+    @Autowired
+    private TestRestTemplate restTemplate;
+
+    @Test
+    void anonymousConfigurationReadIsDeniedWhileHealthRemainsPublic() {
+        ResponseEntity<String> configuration = restTemplate.getForEntity("/application/default", String.class);
+        ResponseEntity<String> health = restTemplate.getForEntity("/actuator/health", String.class);
+
+        assertEquals(HttpStatus.FORBIDDEN, configuration.getStatusCode());
+        assertEquals(HttpStatus.OK, health.getStatusCode());
+    }
+}