Building a Central Authentication Service (CAS) Server in Java

Introduction

CAS (Central Authentication Service) is an enterprise-grade single sign-on (SSO) solution that provides centralized authentication for multiple web applications. A Java-based CAS server enables organizations to implement secure, scalable SSO across their application ecosystem. This guide explores how to build, configure, and deploy a CAS server using Spring Boot and the Apereo CAS framework.

Article: Implementing a Production-Ready CAS Server in Java

CAS server acts as a central authentication authority that issues tickets to authenticated users, allowing them to access multiple applications without re-entering credentials. The Java ecosystem provides robust tools for building enterprise-ready CAS servers.

1. CAS Architecture Overview

Key Components:

CAS Server - Central authentication service
CAS Clients - Applications protected by CAS
Ticket Registry - Storage for tickets (TGT, ST)
Service Registry - Registered applications and policies
Authentication Handlers - Credential validation mechanisms

Authentication Flow:

1. User accesses protected service 2. Redirect to CAS login → 3. User provides credentials 4. CAS validates credentials → 5. Issue Ticket Granting Ticket (TGT) 6. Redirect back with Service Ticket (ST) → 7. Service validates ST 8. Grant access to service

2. Maven Dependencies and Project Setup

CAS Overlay Project Structure:

cas-overlay/ ├── pom.xml ├── src/ │ └── main/ │ ├── java/ │ │ └── com/myapp/cas/ │ └── resources/ │ ├── application.yml │ └── services/ └── etc/ └── cas/

pom.xml for CAS Overlay:

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0"> <modelVersion>4.0.0</modelVersion> <groupId>com.myapp</groupId> <artifactId>cas-overlay</artifactId> <version>1.0.0</version> <packaging>war</packaging> <properties> <cas.version>6.6.14</cas.version> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>3.3.2</version> <configuration> <warName>cas</warName> <overlays> <overlay> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-webapp</artifactId> </overlay> </overlays> </configuration> </plugin> </plugins> </build> <dependencies> <!-- CAS Server Web Application --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-webapp</artifactId> <version>${cas.version}</version> <type>war</type> <scope>runtime</scope> </dependency> <!-- CAS Configuration --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-core-configuration</artifactId> <version>${cas.version}</version> </dependency> <!-- LDAP Authentication --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-ldap</artifactId> <version>${cas.version}</version> </dependency> <!-- JDBC Authentication --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-jdbc</artifactId> <version>${cas.version}</version> </dependency> <!-- REST API Support --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-rest</artifactId> <version>${cas.version}</version> </dependency> <!-- SAML Support --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-saml</artifactId> <version>${cas.version}</version> </dependency> <!-- OAuth2 Support --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-oauth</artifactId> <version>${cas.version}</version> </dependency> <!-- Monitoring and Management --> <dependency> <groupId>org.apereo.cas</groupId> <artifactId>cas-server-support-monitor</artifactId> <version>${cas.version}</version> </dependency> </dependencies> </project>

3. CAS Server Configuration

application.yml:

# CAS Server Configuration server: port: 8443 ssl: enabled: true key-store: file:/etc/cas/jetty/thekeystore key-store-password: changeit key-password: changeit cas: server: name: https://cas.mycompany.com:8443 prefix: ${cas.server.name}/cas # Service Registry Configuration service-registry: core: init-from-json: true json: location: file:/etc/cas/services # Authentication Configuration authn: # LDAP Authentication ldap: - type: AUTHENTICATED ldap-url: ldap://ldap.mycompany.com:389 base-dn: dc=mycompany,dc=com user-filter: cn={user} bind-dn: cn=admin,dc=mycompany,dc=com bind-credential: password search-filter: (cn={user}) # JDBC Authentication jdbc: query: - url: jdbc:postgresql://localhost:5432/cas user: cas_user password: cas_password driver-class: org.postgresql.Driver field-password: password table-users: users field-expired: expired field-disabled: disabled sql: SELECT * FROM users WHERE username = ? # Accept Users (for testing) accept: users: "user1::password1,user2::password2" # REST Authentication rest: uri: http://localhost:8080/api/authenticate # Ticket Registry ticket: registry: jpa: dialect: org.hibernate.dialect.PostgreSQLDialect ddl-auto: update url: jdbc:postgresql://localhost:5432/cas user: cas_user password: cas_password driver-class: org.postgresql.Driver # Logout Configuration logout: follow-service-redirects: true # Monitoring monitor: endpoints: enabled: true sensitive: false web: exposure: include: health,info,metrics,loggers # Theme Configuration theme: default-theme-name: mytheme # Custom Properties custom: app-name: "MyCompany CAS" support-email: "[email protected]"

4. Custom CAS Configuration Classes

CAS Configuration Properties:

package com.myapp.cas.config; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.stereotype.Component; @Component @ConfigurationProperties(prefix = "cas.custom") public class CasCustomProperties { private String appName; private String supportEmail; private int sessionTimeout = 3600; private boolean multiFactorEnabled = false; // Getters and setters public String getAppName() { return appName; } public void setAppName(String appName) { this.appName = appName; } public String getSupportEmail() { return supportEmail; } public void setSupportEmail(String supportEmail) { this.supportEmail = supportEmail; } public int getSessionTimeout() { return sessionTimeout; } public void setSessionTimeout(int sessionTimeout) { this.sessionTimeout = sessionTimeout; } public boolean isMultiFactorEnabled() { return multiFactorEnabled; } public void setMultiFactorEnabled(boolean multiFactorEnabled) { this.multiFactorEnabled = multiFactorEnabled; } }

CAS Configuration Class:

package com.myapp.cas.config; import org.apereo.cas.configuration.CasConfigurationProperties; import org.apereo.cas.web.flow.configurer.DefaultLoginWebflowConfigurer; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.webflow.definition.registry.FlowDefinitionRegistry; import org.springframework.webflow.engine.builder.support.FlowBuilderServices; @Configuration public class CasWebflowConfiguration { @Autowired private CasConfigurationProperties casProperties; @Autowired private ApplicationContext applicationContext; @Autowired private FlowBuilderServices flowBuilderServices; @Bean public DefaultLoginWebflowConfigurer customLoginWebflowConfigurer( FlowDefinitionRegistry loginFlowDefinitionRegistry) { return new CustomLoginWebflowConfigurer( flowBuilderServices, loginFlowDefinitionRegistry, applicationContext, casProperties ); } }

5. Custom Webflow Configuration

Custom Login Webflow Configurer:

package com.myapp.cas.webflow; import org.apereo.cas.configuration.CasConfigurationProperties; import org.apereo.cas.web.flow.configurer.DefaultLoginWebflowConfigurer; import org.springframework.context.ApplicationContext; import org.springframework.webflow.definition.registry.FlowDefinitionRegistry; import org.springframework.webflow.engine.Flow; import org.springframework.webflow.engine.builder.support.FlowBuilderServices; public class CustomLoginWebflowConfigurer extends DefaultLoginWebflowConfigurer { public CustomLoginWebflowConfigurer(FlowBuilderServices flowBuilderServices, FlowDefinitionRegistry loginFlowDefinitionRegistry, ApplicationContext applicationContext, CasConfigurationProperties casProperties) { super(flowBuilderServices, loginFlowDefinitionRegistry, applicationContext, casProperties); } @Override protected void createRememberMeAuthnWebflowConfig(Flow flow) { // Customize remember-me functionality if (casProperties.getTicket().getTgt().getRememberMe().isEnabled()) { createFlowVariable(flow, "credential", rememberMeUsernamePasswordCredential.class); final ViewState state = getState(flow, "viewLoginForm", ViewState.class); createRememberMeAuthnWebflowConfig(state); } } @Override protected void createInitialAuthenticationActions(Flow flow) { // Add custom pre-authentication actions super.createInitialAuthenticationActions(flow); // Add custom action before authentication final ActionState actionState = getState(flow, "initializeLoginForm", ActionState.class); actionState.getEntryActionList().add(createEvaluateAction("customPreAuthenticationAction")); } }

6. Custom Authentication Handlers

Custom Authentication Handler:

package com.myapp.cas.auth; import org.apereo.cas.authentication.AuthenticationHandlerExecutionResult; import org.apereo.cas.authentication.Credential; import org.apereo.cas.authentication.PreventedException; import org.apereo.cas.authentication.handler.support.AbstractPreAndPostProcessingAuthenticationHandler; import org.apereo.cas.authentication.principal.PrincipalFactory; import org.apereo.cas.services.ServicesManager; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import javax.security.auth.login.FailedLoginException; import java.security.GeneralSecurityException; import java.util.ArrayList; import java.util.HashMap; public class CustomAuthenticationHandler extends AbstractPreAndPostProcessingAuthenticationHandler { private static final Logger logger = LoggerFactory.getLogger(CustomAuthenticationHandler.class); public CustomAuthenticationHandler(String name, ServicesManager servicesManager, PrincipalFactory principalFactory, Integer order) { super(name, servicesManager, principalFactory, order); } @Override protected AuthenticationHandlerExecutionResult doAuthentication(Credential credential) throws GeneralSecurityException, PreventedException { try { // Custom authentication logic UsernamePasswordCredential upc = (UsernamePasswordCredential) credential; String username = upc.getUsername(); String password = upc.getPassword(); logger.info("Attempting authentication for user: {}", username); // Validate credentials against your custom source if (validateCredentials(username, password)) { // Create principal with attributes Map<String, Object> attributes = new HashMap<>(); attributes.put("email", username + "@mycompany.com"); attributes.put("displayName", getDisplayName(username)); attributes.put("roles", getUserRoles(username)); final Principal principal = this.principalFactory.createPrincipal(username, attributes); return createHandlerResult(upc, principal, new ArrayList<>()); } throw new FailedLoginException("Invalid credentials for user: " + username); } catch (Exception e) { logger.error("Authentication error", e); throw new FailedLoginException("Authentication failed: " + e.getMessage()); } } @Override public boolean supports(Class<? extends Credential> clazz) { return UsernamePasswordCredential.class.isAssignableFrom(clazz); } @Override public boolean supports(Credential credential) { return credential instanceof UsernamePasswordCredential; } private boolean validateCredentials(String username, String password) { // Implement your custom validation logic // This could be against a database, external API, etc. return "validPassword".equals(password); // Replace with actual validation } private String getDisplayName(String username) { // Retrieve display name from your user store return username.toUpperCase(); } private List<String> getUserRoles(String username) { // Retrieve roles from your user store return List.of("ROLE_USER", "ROLE_APP_USER"); } }

Authentication Handler Configuration:

package com.myapp.cas.config; import com.myapp.cas.auth.CustomAuthenticationHandler; import org.apereo.cas.authentication.AuthenticationEventExecutionPlan; import org.apereo.cas.authentication.AuthenticationEventExecutionPlanConfigurer; import org.apereo.cas.authentication.AuthenticationHandler; import org.apereo.cas.authentication.principal.PrincipalFactory; import org.apereo.cas.configuration.CasConfigurationProperties; import org.apereo.cas.services.ServicesManager; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration @EnableConfigurationProperties(CasConfigurationProperties.class) public class CustomAuthenticationConfiguration implements AuthenticationEventExecutionPlanConfigurer { @Autowired private CasConfigurationProperties casProperties; @Autowired @Qualifier("servicesManager") private ServicesManager servicesManager; @Autowired @Qualifier("principalFactory") private PrincipalFactory principalFactory; @Bean public AuthenticationHandler customAuthenticationHandler() { return new CustomAuthenticationHandler( "CustomAuthenticationHandler", servicesManager, principalFactory, 1 // Order ); } @Override public void configureAuthenticationExecutionPlan(AuthenticationEventExecutionPlan plan) { plan.registerAuthenticationHandler(customAuthenticationHandler()); } }

7. REST API Controllers

CAS Management REST API:

package com.myapp.cas.api; import org.apereo.cas.services.RegisteredService; import org.apereo.cas.services.ServicesManager; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.*; import java.util.Collection; import java.util.HashMap; import java.util.Map; @RestController @RequestMapping("/api/admin") public class CasManagementController { private static final Logger logger = LoggerFactory.getLogger(CasManagementController.class); @Autowired private ServicesManager servicesManager; @GetMapping("/services") public ResponseEntity<Collection<RegisteredService>> getAllServices() { try { Collection<RegisteredService> services = servicesManager.getAllServices(); return ResponseEntity.ok(services); } catch (Exception e) { logger.error("Failed to retrieve services", e); return ResponseEntity.internalServerError().build(); } } @GetMapping("/services/{id}") public ResponseEntity<RegisteredService> getService(@PathVariable Long id) { try { RegisteredService service = servicesManager.findServiceBy(id); if (service == null) { return ResponseEntity.notFound().build(); } return ResponseEntity.ok(service); } catch (Exception e) { logger.error("Failed to retrieve service: {}", id, e); return ResponseEntity.internalServerError().build(); } } @PostMapping("/services") public ResponseEntity<Map<String, Object>> createService(@RequestBody RegisteredService service) { try { servicesManager.save(service); servicesManager.load(); Map<String, Object> response = new HashMap<>(); response.put("message", "Service created successfully"); response.put("serviceId", service.getId()); return ResponseEntity.ok(response); } catch (Exception e) { logger.error("Failed to create service", e); return ResponseEntity.badRequest().body(Map.of("error", e.getMessage())); } } @DeleteMapping("/services/{id}") public ResponseEntity<Map<String, String>> deleteService(@PathVariable Long id) { try { RegisteredService service = servicesManager.findServiceBy(id); if (service == null) { return ResponseEntity.notFound().build(); } servicesManager.delete(service); servicesManager.load(); return ResponseEntity.ok(Map.of("message", "Service deleted successfully")); } catch (Exception e) { logger.error("Failed to delete service: {}", id, e); return ResponseEntity.badRequest().body(Map.of("error", e.getMessage())); } } @GetMapping("/metrics") public ResponseEntity<Map<String, Object>> getMetrics() { try { Map<String, Object> metrics = new HashMap<>(); metrics.put("totalServices", servicesManager.count()); metrics.put("activeSessions", getActiveSessionsCount()); metrics.put("serverUptime", getServerUptime()); return ResponseEntity.ok(metrics); } catch (Exception e) { logger.error("Failed to retrieve metrics", e); return ResponseEntity.internalServerError().build(); } } private int getActiveSessionsCount() { // Implement active sessions count logic return 0; } private String getServerUptime() { // Implement server uptime calculation return "0 days, 0 hours, 0 minutes"; } }

8. Service Registry Configuration

JSON Service Registry Files:

// /etc/cas/services/MyWebApp-10000001.json { "@class": "org.apereo.cas.services.RegexRegisteredService", "serviceId": "^(https|http)://app1.mycompany.com(:443)?/.*", "name": "MyWebApp", "id": 10000001, "description": "My Company Web Application", "evaluationOrder": 1, "logoutType": "BACK_CHANNEL", "attributeReleasePolicy": { "@class": "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy", "allowedAttributes": ["email", "displayName", "roles"] }, "accessStrategy": { "@class": "org.apereo.cas.services.DefaultRegisteredServiceAccessStrategy", "enabled": true, "ssoEnabled": true } }

// /etc/cas/services/MyAPI-10000002.json { "@class": "org.apereo.cas.services.RegexRegisteredService", "serviceId": "^(https|http)://api.mycompany.com(:443)?/.*", "name": "MyAPI", "id": 10000002, "description": "My Company REST API", "evaluationOrder": 2, "logoutType": "BACK_CHANNEL", "attributeReleasePolicy": { "@class": "org.apereo.cas.services.ReturnAllowedAttributeReleasePolicy", "allowedAttributes": ["email", "roles"] }, "accessStrategy": { "@class": "org.apereo.cas.services.DefaultRegisteredServiceAccessStrategy", "enabled": true, "ssoEnabled": true } }

9. Custom Thymeleaf Views

Custom Login View (login.html):

<!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org" lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title th:text="#{screen.login.title}">MyCompany CAS - Login</title> <link rel="stylesheet" th:href="@{/css/cas.css}"> <style> .custom-login-container { max-width: 400px; margin: 50px auto; padding: 20px; border: 1px solid #ddd; border-radius: 5px; background: #fff; } .company-logo { text-align: center; margin-bottom: 20px; } .alert-custom { padding: 10px; margin-bottom: 15px; border-radius: 3px; } .alert-error { background-color: #f8d7da; color: #721c24; border: 1px solid #f5c6cb; } </style> </head> <body> <div class="custom-login-container"> <div class="company-logo"> <h2>MyCompany CAS</h2> <p>Central Authentication Service</p> </div> <div th:if="${param.error != null}" class="alert-custom alert-error"> <strong>Login Failed!</strong> Invalid username or password. </div> <div th:if="${param.logout != null}" class="alert-custom alert-success"> You have been logged out successfully. </div> <form th:action="@{/login}" method="post"> <div class="form-group"> <label for="username">Username:</label> <input type="text" id="username" name="username" class="form-control" required autofocus> </div> <div class="form-group"> <label for="password">Password:</label> <input type="password" id="password" name="password" class="form-control" required> </div> <div class="form-group form-check"> <input type="checkbox" id="rememberMe" name="rememberMe" class="form-check-input"> <label for="rememberMe" class="form-check-label">Remember me</label> </div> <input type="hidden" th:name="${_csrf.parameterName}" th:value="${_csrf.token}"> <button type="submit" class="btn btn-primary btn-block">Sign In</button> </form> <div class="mt-3 text-center"> <a th:href="@{/forgot-password}">Forgot Password?</a> </div> <div class="mt-3 text-center"> <small>&copy; 2024 MyCompany. All rights reserved.</small> </div> </div> </body> </html>

10. Database Schema for Ticket Registry

PostgreSQL Schema:

-- CAS Ticket Registry Tables CREATE TABLE casserviceticket ( id CHARACTER VARYING(255) NOT NULL, number_of_times_used INTEGER, creation_time TIMESTAMP WITHOUT TIME ZONE, expiration_policy BYTEA, last_time_used TIMESTAMP WITHOUT TIME ZONE, previous_last_time_used TIMESTAMP WITHOUT TIME ZONE, service CHARACTER VARYING(255), ticket_already_used BOOLEAN, type CHARACTER VARYING(255), ticket_granting_ticket_id CHARACTER VARYING(255), PRIMARY KEY (id) ); CREATE TABLE casticketgrantingticket ( id CHARACTER VARYING(255) NOT NULL, expiration_policy BYTEA, creation_time TIMESTAMP WITHOUT TIME ZONE, authentication BYTEA, number_of_times_used INTEGER, PRIMARY KEY (id) ); CREATE TABLE casticketgrantingticket_proxied_by ( ticket_granting_ticket_id CHARACTER VARYING(255) NOT NULL, proxied_by_id CHARACTER VARYING(255) NOT NULL ); CREATE TABLE casticketgrantingticket_services ( ticket_granting_ticket_id CHARACTER VARYING(255) NOT NULL, service CHARACTER VARYING(255) ); -- Indexes for performance CREATE INDEX idx_service_ticket_service ON casserviceticket (service); CREATE INDEX idx_service_ticket_tgt_id ON casserviceticket (ticket_granting_ticket_id); CREATE INDEX idx_tgt_expiration ON casticketgrantingticket (creation_time);

11. Spring Boot Application Class

CAS Application:

package com.myapp.cas; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.context.annotation.ComponentScan; @SpringBootApplication @EnableConfigurationProperties @ComponentScan(basePackages = {"com.myapp.cas", "org.apereo.cas"}) public class CasServerApplication { public static void main(String[] args) { SpringApplication.run(CasServerApplication.class, args); } }

12. Docker Deployment

Dockerfile:

FROM eclipse-temurin:11-jre # Install dependencies RUN apt-get update && apt-get install -y \ curl \ && rm -rf /var/lib/apt/lists/* # Create CAS user and directories RUN adduser --disabled-password --home /opt/cas --gecos '' cas USER cas WORKDIR /opt/cas # Copy CAS WAR file COPY --chown=cas:cas target/cas.war /opt/cas/ # Create configuration directory RUN mkdir -p /opt/cas/etc/cas /opt/cas/etc/cas/services /opt/cas/etc/cas/config # Copy configuration files COPY --chown=cas:cas src/main/resources/ /opt/cas/etc/cas/config/ COPY --chown=cas:cas etc/cas/ /opt/cas/etc/cas/ # Expose CAS port EXPOSE 8443 # Health check HEALTHCHECK --interval=30s --timeout=3s --start-period=60s \ CMD curl -f https://localhost:8443/cas/actuator/health || exit 1 # Start CAS server CMD ["java", "-jar", "cas.war", \ "--server.ssl.key-store=/opt/cas/etc/cas/thekeystore", \ "--server.ssl.key-store-password=changeit", \ "--cas.service-registry.json.location=file:/opt/cas/etc/cas/services", \ "--spring.config.location=file:/opt/cas/etc/cas/config/application.yml"]

docker-compose.yml:

version: '3.8' services: cas-server: build: . ports: - "8443:8443" environment: - SPRING_PROFILES_ACTIVE=prod - CAS_SERVER_NAME=https://cas.mycompany.com:8443 volumes: - ./logs:/opt/cas/logs - ./keystore:/opt/cas/etc/cas networks: - cas-network postgres: image: postgres:13 environment: - POSTGRES_DB=cas - POSTGRES_USER=cas_user - POSTGRES_PASSWORD=cas_password volumes: - postgres-data:/var/lib/postgresql/data networks: - cas-network ldap: image: osixia/openldap:1.5.0 environment: - LDAP_DOMAIN=mycompany.com - LDAP_ADMIN_PASSWORD=admin volumes: - ldap-data:/var/lib/ldap networks: - cas-network volumes: postgres-data: ldap-data: networks: cas-network: driver: bridge

13. Monitoring and Management

CAS Actuator Endpoints:

package com.myapp.cas.monitoring; import org.springframework.boot.actuate.health.Health; import org.springframework.boot.actuate.health.HealthIndicator; import org.springframework.stereotype.Component; @Component public class CasHealthIndicator implements HealthIndicator { private final ServicesManager servicesManager; public CasHealthIndicator(ServicesManager servicesManager) { this.servicesManager = servicesManager; } @Override public Health health() { try { int serviceCount = servicesManager.count(); boolean healthy = serviceCount >= 0; // Basic health check if (healthy) { return Health.up() .withDetail("servicesRegistered", serviceCount) .withDetail("status", "CAS Server is healthy") .build(); } else { return Health.down() .withDetail("error", "No services registered") .build(); } } catch (Exception e) { return Health.down() .withDetail("error", e.getMessage()) .build(); } } }

14. Security Configuration

Security Configuration:

package com.myapp.cas.security; import org.apereo.cas.configuration.CasConfigurationProperties; import org.springframework.beans.factory.annotation.Autowired; 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.config.annotation.web.configuration.EnableWebSecurity; import org.springframework.security.web.SecurityFilterChain; @Configuration @EnableWebSecurity public class SecurityConfig { @Autowired private CasConfigurationProperties casProperties; @Bean public SecurityFilterChain filterChain(HttpSecurity http) throws Exception { http .csrf(csrf -> csrf.ignoringRequestMatchers( "/logout", "/validate", "/serviceValidate", "/proxyValidate", "/samlValidate" )) .authorizeHttpRequests(authz -> authz .requestMatchers("/", "/login", "/logout", "/error").permitAll() .requestMatchers("/actuator/health", "/actuator/info").permitAll() .requestMatchers("/actuator/**").hasRole("ADMIN") .requestMatchers("/api/admin/**").hasRole("ADMIN") .anyRequest().authenticated() ) .sessionManagement(session -> session .sessionFixation().migrateSession() ); return http.build(); } }

Benefits of Java CAS Server

Enterprise-Grade SSO - Production-ready single sign-on
Protocol Support - CAS, SAML, OAuth2, OpenID Connect
Extensible Architecture - Custom authentication handlers and flows
High Availability - Clustered ticket registry support
Security - Built-in protection against common attacks
Monitoring - Comprehensive metrics and health checks

Conclusion

Building a CAS server in Java using the Apereo CAS framework provides a robust, scalable solution for enterprise single sign-on. The framework's extensible architecture allows for custom authentication mechanisms, service registration, and integration with various identity providers.

The key to successful CAS implementation is:

Proper service registry management for application registration
Secure ticket storage with appropriate expiration policies
Comprehensive monitoring and health checks
Regular security updates and maintenance
Thorough testing of authentication flows

Start with a basic CAS setup and gradually add more advanced features like multi-factor authentication, delegated authentication, and protocol bridging as your requirements evolve.

Call to Action: Begin by setting up a development CAS server with file-based service registry and test authentication flows. Once validated, move to production with database-backed ticket registry and proper SSL configuration. Monitor the CAS server performance and security regularly to ensure reliable SSO services.