Spring Security

  Basic Authentication and Authorization:

1. You need to secure a REST API with basic authentication. How would you configure it in Spring Security?
2. A user needs to be authenticated against a custom user store instead of the default in-memory one. How do you implement this in Spring Security?
3. You need to restrict access to certain endpoints based on user roles. How would you configure this?
4. You want to implement form-based authentication with a custom login page. How do you do it?
5. You need to support both basic and form-based authentication for different endpoints. How would you configure this in Spring Security?
6. You need to allow unauthenticated access to certain public endpoints. How do you achieve this?
7. A specific endpoint should only be accessible by users with multiple roles. How would you configure this?
8. You want to display a custom access denied page for unauthorized users. How do you configure it in Spring Security?
9. You need to implement remember-me functionality in your application. How would you configure this?
10. The login process should be logged for audit purposes. How would you implement this in Spring Security?

Advanced Authentication Mechanisms:

11. You need to integrate LDAP-based authentication into your Spring Security application. How would you configure it?
12. How would you configure Spring Security to use OAuth2 for authentication with a third-party provider like Google?
13. You need to implement multi-factor authentication (MFA) in your Spring Security application. How would you go about this?
14. You have a custom token-based authentication mechanism. How do you integrate it with Spring Security?
15. You need to implement SSO (Single Sign-On) in a Spring Boot application. How do you achieve this using Spring Security?
16. How would you configure Spring Security to use JWT tokens for stateless authentication?
17. You need to authenticate users based on their IP address. How do you implement this in Spring Security?
18. You need to support SAML-based authentication in your Spring Security application. How would you configure it?
19. How would you implement custom authentication filters in Spring Security?
20. You need to handle multiple authentication providers (e.g., LDAP and database). How would you configure this?

Role-Based Access Control (RBAC):

21. How would you assign roles dynamically to users based on specific conditions during authentication?
22. A user’s roles need to be loaded from a database. How would you implement this in Spring Security?
23. You need to implement hierarchical roles (e.g., ADMIN > MANAGER > USER). How would you configure this in Spring Security?
24. How would you implement method-level security to restrict access to specific methods based on roles?
25. You need to implement role-based access control with custom roles not present in the user database. How would you achieve this?
26. How do you configure access control lists (ACLs) for securing domain objects in Spring Security?
27. You need to implement a role-based menu system where the menu options vary based on user roles. How would you implement this?
28. How would you implement role-based authorization checks at the controller level?
29. A user’s role needs to be updated dynamically during a session. How would you handle this in Spring Security?
30. How do you prevent users with certain roles from accessing specific URLs in a Spring Boot application?

Security Context and Session Management:

31. You need to manage user sessions to ensure only one active session per user. How would you configure this in Spring Security?
32. How would you implement session timeout handling in a Spring Security application?
33. You need to invalidate a user’s session programmatically. How would you achieve this in Spring Security?
34. You want to track the number of active sessions for a user. How would you implement this in Spring Security?
35. How would you configure Spring Security to store sessions in a distributed environment (e.g., Redis)?
36. You need to maintain a user’s authentication state across multiple applications. How would you implement this?
37. How would you configure Spring Security to handle session fixation attacks?
38. You need to programmatically access the current user’s authentication information. How do you achieve this?
39. How would you implement a custom session management strategy for a Spring Boot application?
40. You need to log out a user from all active sessions when they change their password. How would you implement this?

Custom Authentication and Authorization:

41. How would you implement a custom authentication provider to validate users against an external service?
42. You need to create a custom UserDetailsService to load user-specific data. How would you implement it?
43. How would you customize the authentication failure handling process in Spring Security?
44. You need to allow users to authenticate using a third-party API. How would you integrate this with Spring Security?
45. How would you implement custom access decision logic in Spring Security?
46. You need to create a custom GrantedAuthority implementation for dynamic permission assignment. How would you do this?
47. How would you customize the behavior of the SecurityContext in Spring Security?
48. You need to perform a security check on a request parameter before allowing access to a resource. How do you implement this?
49. How would you implement a custom logout handler in Spring Security?
50. You want to restrict access to certain endpoints based on dynamic conditions, such as time of day. How would you implement this?

Spring Security in Microservices:

51. You need to implement token-based authentication across multiple microservices. How would you achieve this?
52. How would you secure communication between microservices in a Spring Boot application?
53. You need to propagate user security context across microservices. How do you implement this?
54. How would you handle centralized authentication for multiple microservices using Spring Security?
55. You need to implement role-based access control across microservices. How would you manage this?
56. How do you secure service-to-service communication in a microservice architecture using Spring Security?
57. You need to implement a centralized authorization service for microservices. How would you configure this?
58. How would you handle authentication and authorization in a reactive microservice using Spring Security?
59. You need to implement JWT-based security for stateless microservices. How do you achieve this?
60. How would you implement API Gateway security in a microservice architecture using Spring Security?

Security Testing and Auditing:

61. How would you test a Spring Security configuration to ensure proper access controls?
62. You need to write unit tests for custom security filters. How would you do it?
63. How would you test method-level security in Spring Boot?
64. You need to audit login attempts and failed login events. How would you implement this in Spring Security?
65. How would you test a Spring Security configuration for various authentication scenarios?
66. You need to create a test suite to validate security roles and permissions. How would you set it up?
67. How would you ensure that your Spring Security configuration is compliant with security best practices?
68. You need to log and monitor security-related events. How would you configure this in Spring Security?
69. How would you implement security vulnerability testing for a Spring Boot application?
70. You need to simulate a CSRF attack in your tests. How would you configure this scenario?

Security for Specific Use Cases:

71. How would you implement CSRF protection in a Spring Boot application with REST APIs?
72. You need to secure WebSocket communication in a Spring Boot application. How would you configure this?
73. How would you implement custom CORS configuration for specific endpoints in Spring Security?
74. You need to secure file uploads in a Spring Boot application. How would you achieve this?
75. How would you implement security headers (e.g., X-Content-Type-Options) in a Spring Boot application?
76. You need to restrict file download access based on user roles. How would you implement this in Spring Security?
77. How would you secure a multi-tenant application where different tenants have different security requirements?
78. You need to handle password reset functionality securely. How would you implement this in Spring Security?
79. How would you implement encryption for sensitive data in a Spring Security application?
80. You need to enforce strong password policies for users. How would you implement this in Spring Security?

Integration with Other Frameworks and Technologies:

81. How would you integrate Spring Security with Thymeleaf for secure view rendering?
82. You need to secure a Spring Boot application that uses GraphQL. How would you implement security?
83. How would you configure Spring Security to work with Spring Data REST?
84. You need to integrate Spring Security with a custom front-end framework (e.g., Angular, React). How do you handle authentication?
85. How would you secure RESTful APIs in a Spring Boot application with OAuth2?
86. You need to implement role-based access control in a Spring Boot application using Keycloak. How would you configure it?
87. How would you secure a RESTful web service that communicates with an external OAuth2 provider?
88. You need to integrate Spring Security with Apache Shiro for a specific use case. How would you handle this?
89. How would you implement JWT authentication in a Spring Boot application with a custom front-end?
90. You need to secure a legacy application using Spring Security without altering much of the existing codebase. How do you approach this?

Security Best Practices and Optimization:

91. You need to ensure your application is resistant to common security vulnerabilities like XSS and SQL Injection. How would you implement this in Spring Security?
92. How would you optimize the performance of a Spring Security-enabled application under high load?
93. You need to implement secure logging practices in a Spring Boot application. How do you achieve this?
94. How would you implement HTTPS enforcement in a Spring Boot application?
95. You need to secure a Spring Boot application against brute force attacks. How would you implement rate limiting?
96. How would you ensure that your Spring Security configuration is scalable for a high-traffic application?
97. You need to implement content security policies (CSP) in your Spring Boot application. How would you configure this?
98. How would you secure sensitive endpoints that are accessible via APIs in a mobile application?
99. You need to implement security measures to protect against session hijacking. How would you handle this in Spring Security?
100. You need to ensure that user data is protected at rest and in transit. How would you implement this in Spring Security?

 

Basic Authentication & User Authentication

1. How would you secure a REST API with basic authentication in Spring Security?
   You can configure basic authentication by adding a security configuration class that extends WebSecurityConfigurerAdapter. Use http.basic() to enable basic authentication and configure a UserDetailsService to authenticate users against a custom store.

2. How do you authenticate a user against a custom user store instead of the default in-memory one in Spring Security?
   You can implement a UserDetailsService that fetches user details from your custom user store (e.g., database, LDAP, etc.) and register it in the security configuration.

3. How do you restrict access to certain endpoints based on user roles in Spring Security?
   Use the .authorizeRequests() method to define role-based access control for specific endpoints, e.g., .antMatchers("/admin/**").hasRole("ADMIN").

4. How would you implement form-based authentication with a custom login page in Spring Security?
   Use .formLogin().loginPage("/custom-login") to specify a custom login page, then configure the loginProcessingUrl() and defaultSuccessUrl() for handling authentication and redirects.

5. How would you support both basic and form-based authentication for different endpoints in Spring Security?
   You can configure different authentication mechanisms for different endpoints using .httpBasic() for basic authentication and .formLogin() for form-based authentication within the http security configuration.

6. How would you allow unauthenticated access to certain public endpoints in Spring Security?
   Use .authorizeRequests().antMatchers("/public/**").permitAll() to allow unauthenticated access to specific URLs.

7. How do you restrict access to an endpoint by users with multiple roles in Spring Security?
   You can use .antMatchers("/restricted/**").hasAnyRole("ADMIN", "MANAGER") to allow access to users with either of the specified roles.

8. How would you display a custom access denied page for unauthorized users in Spring Security?
   Configure .exceptionHandling().accessDeniedPage("/access-denied") to specify a custom access denied page.

9. How do you implement remember-me functionality in Spring Security?
   Enable the remember-me feature using .rememberMe().key("uniqueAndSecret") in the security configuration, and it will store the user's authentication information in a cookie.

10. How do you log the login process for audit purposes in Spring Security?
    You can use a custom AuthenticationSuccessHandler or AuthenticationFailureHandler to log login attempts, or use Spring's SecurityContext to log authentication events.

Advanced Authentication Mechanisms

11. How do you integrate LDAP-based authentication in Spring Security?
    Configure LdapAuthenticationProvider with your LDAP server details in the security configuration, using ldapAuthentication().

12. How would you configure Spring Security to use OAuth2 for authentication with a third-party provider like Google?
    Use Spring Security OAuth2 client support and configure oauth2Login() with client details for Google, including client ID, secret, and redirect URI.

13. How do you implement multi-factor authentication (MFA) in Spring Security?
    Implement MFA by integrating an additional authentication step after the first one (e.g., SMS, email, or TOTP). You can configure this via a custom AuthenticationProvider.

14. How do you integrate a custom token-based authentication mechanism with Spring Security?
    Implement a custom AuthenticationFilter that processes the token, then register it in the Spring Security filter chain.

15. How do you implement Single Sign-On (SSO) in a Spring Boot application using Spring Security?
    Configure Spring Security to work with an external SSO provider (e.g., Okta, Keycloak, or a custom OAuth2 provider) using oauth2Login() or sso().

16. How do you configure Spring Security to use JWT tokens for stateless authentication?
    Use a custom JWTAuthenticationFilter that processes the JWT token and integrates it with the Spring Security context. This typically involves using a JwtTokenProvider class.

17. How do you authenticate users based on their IP address in Spring Security?
    Implement a custom AuthenticationProvider or filter that checks the user's IP address before authenticating.

18. How do you implement SAML-based authentication in Spring Security?
    Use Spring Security SAML extension and configure a SAMLAuthenticationProvider with an Identity Provider (IdP).

19. How do you implement custom authentication filters in Spring Security?
    You can create a custom OncePerRequestFilter or extend AbstractAuthenticationProcessingFilter and register it in the Spring Security filter chain.

20. How do you handle multiple authentication providers (e.g., LDAP and database) in Spring Security?
    Configure multiple AuthenticationManager instances for different authentication mechanisms and use the AuthenticationManagerBuilder to register them.

Role-Based Access Control (RBAC)

21. How would you assign roles dynamically to users based on specific conditions during authentication in Spring Security?
    Customize the UserDetailsService to assign roles dynamically based on the user's attributes or conditions.

22. How would you load user roles from a database in Spring Security?
    Implement a custom UserDetailsService that loads user roles from the database and map them to GrantedAuthority objects.

23. How do you implement hierarchical roles in Spring Security (e.g., ADMIN > MANAGER > USER)?
    Use role prefixing (ROLE_) in the database or configuration and configure access control for each role using .hasRole() or .hasAuthority().

24. How do you implement method-level security in Spring Security based on roles?
    Enable method security using @EnableGlobalMethodSecurity(prePostEnabled = true) and use annotations like @PreAuthorize or @Secured to control access at the method level.

25. How would you implement role-based access control with custom roles not present in the user database in Spring Security?
    Define custom GrantedAuthority objects in your UserDetailsService and map them to your custom roles.

26. How do you configure access control lists (ACLs) for securing domain objects in Spring Security?
    Use Spring Security ACL module to define access rules for domain objects. Set up ACL entries for each object with appropriate permissions.

27. How do you implement a role-based menu system based on user roles in Spring Security?
    Create conditional logic in your views (e.g., Thymeleaf) to display menu options based on the authenticated user's roles.

28. How do you implement role-based authorization checks at the controller level in Spring Security?
    Use @PreAuthorize or @Secured annotations at the controller methods to check for roles before granting access.

29. How do you update a user’s role dynamically during a session in Spring Security?
    Use SecurityContextHolder to manually update the authentication object with new roles during the session.

30. How do you prevent users with certain roles from accessing specific URLs in Spring Boot?
    Use .antMatchers("/url").hasRole("ROLE_ADMIN") to restrict access based on roles.

Security Context and Session Management

31. How do you manage user sessions to ensure only one active session per user in Spring Security?
    Configure sessionManagement().maximumSessions(1).maxSessionsPreventsLogin(true) to limit active sessions.

32. How do you implement session timeout handling in Spring Security?
    Use .sessionManagement().invalidSessionUrl("/session-timeout") to redirect to a timeout page and .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.IF_REQUIRED) to control session creation.

33. How do you invalidate a user’s session programmatically in Spring Security?
    Call SecurityContextHolder.clearContext() and invalidate the session with HttpSession.invalidate().

34. How do you track the number of active sessions for a user in Spring Security?
    Use sessionManagement().sessionFixation().none() and implement session tracking using HttpSessionListener or custom session management.

35. How would you configure Spring Security to store sessions in a distributed environment (e.g., Redis)?
    Use Spring Session to store sessions in Redis by adding dependencies and configuring @EnableRedisHttpSession.

36. How would you maintain a user’s authentication state across multiple applications in Spring Security?
    Implement a centralized authentication mechanism (e.g., using OAuth2 or SSO) to share the security context across applications.

37. How do you configure Spring Security to handle session fixation attacks?
    Use .sessionManagement().sessionFixation().migrateSession() to migrate the session to a new one after authentication.

38. How do you programmatically access the current user’s authentication information in Spring Security?
    Access the authentication information via SecurityContextHolder.getContext().getAuthentication().

39. How would you implement a custom session management strategy in Spring Boot using Spring Security?
    Override session management behavior by configuring a custom SessionAuthenticationStrategy or SessionManagementFilter.

40. How do you log out a user from all active sessions when they change their password in Spring Security?
    Use a SecurityContextLogoutHandler and invalidate all sessions associated with the user upon password change.

Custom Authentication and Authorization

41. How do you implement a custom authentication provider to validate users against an external service in Spring Security?
    Implement a custom AuthenticationProvider that communicates with the external service for authentication.

42. How do you create a custom UserDetailsService to load user-specific data in Spring Security?
    Implement the UserDetailsService interface to load user information (e.g., username, roles, password) from a custom source like a database.

43. How do you customize the authentication failure handling process in Spring Security?
    Implement a custom AuthenticationFailureHandler to handle failed login attempts (e.g., logging, redirecting, etc.).

44. How do you allow users to authenticate using a third-party API in Spring Security?
    Use Spring Security OAuth2 or a custom authentication filter to integrate third-party APIs (e.g., social login).

45. How do you implement custom access decision logic in Spring Security?
    Implement a custom AccessDecisionManager and AccessDecisionVoter to define your own authorization rules.

46. How do you create a custom GrantedAuthority implementation for dynamic permission assignment in Spring Security?
    Create a custom class that implements GrantedAuthority and override the getAuthority() method to return dynamic roles or permissions.

47. How do you customize the behavior of the SecurityContext in Spring Security?
    You can customize the SecurityContext by implementing a custom SecurityContextRepository.

48. How do you perform a security check on a request parameter before allowing access to a resource in Spring Security?
    Implement a custom filter that checks request parameters before passing control to other filters.

49. How do you implement a custom logout handler in Spring Security?
    Implement a custom LogoutHandler and register it with logout().addLogoutHandler() to handle specific logout behavior.

50. How would you restrict access to certain endpoints based on dynamic conditions, such as the time of day, in Spring Security?
    Implement a custom AccessDecisionVoter or Filter that checks the current time and dynamically applies access control.

 

Spring Security in Microservices

51. How would you implement token-based authentication across multiple microservices in Spring Security?
    You can use JWT tokens to authenticate users across microservices. Each microservice would validate the JWT token on every request to authenticate the user, and you can use Spring Security's OAuth2 or a custom filter to handle token verification.

52. How would you secure communication between microservices in a Spring Boot application?
    To secure communication between microservices, you can use mutual TLS (mTLS), API gateways, or OAuth2 tokens. You can also use Spring Security's @EnableOAuth2Client for client-side OAuth2 or Spring Cloud Security for integration with microservices.

53. How do you propagate user security context across microservices in Spring Security?
    Use Spring Security’s OAuth2 or JWT-based token propagation mechanism to pass security context between microservices. Each microservice will extract and validate the token to keep the user context intact.

54. How would you handle centralized authentication for multiple microservices using Spring Security?
    You can implement centralized authentication using an OAuth2 or SSO mechanism, such as Keycloak or Okta, where a single service handles authentication, and other microservices rely on it for authorization via tokens.

55. How do you implement role-based access control across microservices in Spring Security?
    Each microservice can use role-based access control (RBAC) by validating the roles from JWT tokens or OAuth2 scopes. The token carries the user's roles or claims, which can be used to authorize access to specific resources.

56. How do you secure service-to-service communication in a microservice architecture using Spring Security?
    Secure service-to-service communication by using OAuth2 or mutual TLS (mTLS). With OAuth2, each service can authenticate requests using bearer tokens, ensuring that only authorized services can access specific APIs.

57. How do you implement a centralized authorization service for microservices?
    Set up a centralized service for managing user roles and permissions (e.g., using Keycloak, Auth0). Each microservice can query this service for authorization or rely on token-based authorization.

58. How would you handle authentication and authorization in a reactive microservice using Spring Security?
    In a reactive Spring Security setup, use the ReactiveSecurityContextHolder for handling the security context, and configure the authentication mechanism using SecurityWebFilterChain. You can authenticate using OAuth2 or JWT in a non-blocking, reactive way.

59. How do you implement JWT-based security for stateless microservices in Spring Security?
    Use a custom JWTAuthenticationFilter to extract and validate the JWT token from the request headers. This approach ensures stateless authentication because there is no session involved.

60. How would you implement API Gateway security in a microservice architecture using Spring Security?
    Implement security at the API Gateway level by securing all routes through a single entry point. You can configure Spring Security to validate JWT tokens or handle OAuth2-based authentication, acting as a reverse proxy for all services.

Security Testing and Auditing

61. How would you test a Spring Security configuration to ensure proper access controls?
    Use integration tests with @WebMvcTest or @SpringBootTest annotations to validate that the access control rules are enforced. You can also use MockMvc to simulate requests and verify that the correct access control behavior is applied.

62. How would you write unit tests for custom security filters in Spring Security?
    Write unit tests using Mockito and Spring Security’s TestContext. Mock HTTP requests and verify the behavior of your custom filters, including correct authentication handling and request processing.

63. How would you test method-level security in Spring Boot?
    Enable method security and write tests using @PreAuthorize or @Secured annotations. Use @WithMockUser to simulate user roles during tests and ensure the correct method-level security is applied.

64. How would you audit login attempts and failed login events in Spring Security?
    Implement a custom AuthenticationFailureHandler and AuthenticationSuccessHandler to log login attempts. Store the logs for auditing purposes and use Spring’s SecurityContext to capture authentication events.

65. How would you test a Spring Security configuration for various authentication scenarios?
    Write tests with different user roles and scenarios using MockMvc or @WebMvcTest, verifying that the correct security rules are enforced for each test case (e.g., valid/invalid credentials, different user roles).

66. How would you create a test suite to validate security roles and permissions in Spring Security?
    Use a combination of unit tests, integration tests, and mock authentication with @WithMockUser or @SpringBootTest to validate the role-based access control mechanisms.

67. How would you ensure that your Spring Security configuration is compliant with security best practices?
    Use static analysis tools like SonarQube or check compliance with OWASP security guidelines. Regularly audit your security configurations and make sure features like HTTPS, CSRF protection, and password hashing are implemented correctly.

68. How would you log and monitor security-related events in Spring Security?
    Use Spring Security's built-in logging and configure it with a logging framework like Logback or SLF4J. You can log authentication and authorization events, and use tools like ELK (Elasticsearch, Logstash, Kibana) for centralized monitoring.

69. How would you implement security vulnerability testing for a Spring Boot application?
    Perform regular security vulnerability scanning using tools like OWASP ZAP, Snyk, or Dependency-Check. Also, conduct penetration testing and security audits.

70. How would you simulate a CSRF attack in your tests?
    Simulate a CSRF attack by disabling CSRF protection in tests or using a tool to submit a form without the required CSRF token, then verify that Spring Security blocks the attack.

Security for Specific Use Cases

71. How would you implement CSRF protection in a Spring Boot application with REST APIs?
    Enable CSRF protection globally using http.csrf().enable() in your Spring Security configuration, but ensure it’s disabled for stateless REST APIs where tokens are used for security instead.

72. How would you secure WebSocket communication in a Spring Boot application?
    Secure WebSockets by using Spring Security’s WebSocket support with authentication and authorization. Configure the WebSocket endpoints and ensure that only authenticated users can access them.

73. How would you implement custom CORS configuration for specific endpoints in Spring Security?
    Use @CrossOrigin on controllers or methods to enable CORS. Alternatively, configure global CORS handling in the Spring Security configuration using http.cors() and a custom CorsConfigurationSource.

74. How do you secure file uploads in a Spring Boot application?
    Secure file uploads by validating file types, size limits, and ensuring that files are stored in secure directories. Use Spring Security’s @PreAuthorize annotations to restrict access to file upload endpoints.

75. How would you implement security headers (e.g., X-Content-Type-Options) in a Spring Boot application?
    Add security headers using a Filter or within the Spring Security configuration using http.headers().xssProtection().and().contentSecurityPolicy(). You can configure headers like Strict-Transport-Security, X-Content-Type-Options, etc.

76. How would you restrict file download access based on user roles in Spring Security?
    Use role-based access control with .antMatchers("/download/**").hasRole("ADMIN") to restrict access to certain file download endpoints based on roles.

77. How would you secure a multi-tenant application where different tenants have different security requirements?
    Use a TenantContext to manage tenant-specific authentication and authorization. You can implement a custom AuthenticationProvider and adjust access control dynamically based on the tenant.

78. How do you handle password reset functionality securely in Spring Security?
    Implement a secure password reset flow by generating a token with an expiration time. Send the token via email, then allow the user to reset their password with a valid token.

79. How would you implement encryption for sensitive data in a Spring Security application?
    Use Spring Security's Encryption API or external libraries like JCE (Java Cryptography Extension) to encrypt sensitive data. Encrypt passwords using BCryptPasswordEncoder or other secure hash algorithms.

80. How would you enforce strong password policies for users in Spring Security?
    Use PasswordEncoder with strength configurations, such as BCryptPasswordEncoder with a work factor. You can also integrate custom validators to enforce password policies like minimum length, special characters, etc.

Integration with Other Frameworks and Technologies

81. How would you integrate Spring Security with Thymeleaf for secure view rendering?
    Use Spring Security’s th:sec attributes in Thymeleaf templates to secure parts of the page based on user roles or authentication. You can use sec:authorize="isAuthenticated()" to conditionally render content.

82. How would you secure a Spring Boot application that uses GraphQL?
    Secure GraphQL endpoints by configuring Spring Security’s HTTP security to require authentication and authorization for the GraphQL queries and mutations, often using JWT or OAuth2 for token-based authentication.

83. How would you configure Spring Security to work with Spring Data REST?
    Secure Spring Data REST repositories using @RepositoryRestResource with Spring Security annotations like @PreAuthorize to control access to the REST API.

84. How do you integrate Spring Security with a custom front-end framework (e.g., Angular, React)?
    Use JWT or OAuth2 for authentication, where the front-end sends the token in HTTP headers (Authorization header). The back-end (Spring Boot) validates the token with Spring Security filters.

85. How would you secure RESTful APIs in a Spring Boot application with OAuth2?
    Use Spring Security’s OAuth2 client and resource server configuration to secure REST APIs. The client will need to authenticate with an OAuth2 provider (e.g., Google or Facebook), and the server will validate the token.

86. How would you integrate Spring Security with Keycloak for role-based access control in a Spring Boot application?
    Configure Spring Security to use Keycloak for authentication and authorization by integrating with the KeycloakSpringBootAdapter or SpringSecurityOAuth2.

87. How would you secure a RESTful web service that communicates with an external OAuth2 provider?
    Use Spring Security's OAuth2 client support to configure the external provider details (e.g., client ID, client secret, authorization URI, etc.) and secure the communication with OAuth2 tokens.

88. How would you integrate Spring Security with Apache Shiro for a specific use case?
    Spring Security can be integrated with Apache Shiro by customizing authentication filters or using Spring Shiro modules for managing sessions and security.

89. How would you implement JWT authentication in a Spring Boot application with a custom front-end?
    Use JWT for stateless authentication. The front-end sends a token to the back-end via HTTP headers, and Spring Security validates it with a custom filter.

90. How would you secure a legacy application using Spring Security without altering much of the existing codebase?
    Integrate Spring Security gradually by securing the authentication flow and adding Spring Security’s filter chain while leaving other parts of the legacy system untouched.

Security Best Practices and Optimization

91. How would you ensure your application is resistant to common security vulnerabilities like XSS and SQL Injection?
    Use proper input validation and sanitization, implement CSP headers, and use ORM frameworks (like Hibernate) to prevent SQL injection.

92. How would you optimize the performance of a Spring Security-enabled application under high load?
    Use stateless authentication (e.g., JWT), enable caching for security-related operations, and reduce the number of authentication checks by centralizing authorization in middleware.

93. How do you implement secure logging practices in a Spring Boot application?
    Use SLF4J with Logback or Log4j for logging. Avoid logging sensitive data, and ensure that logs are stored securely.

94. How would you implement HTTPS enforcement in a Spring Boot application?
    Configure Spring Security to enforce HTTPS by setting http.requiresChannel().anyRequest().requiresSecure() to redirect HTTP requests to HTTPS.

95. How do you secure a Spring Boot application against brute force attacks?
    Implement rate limiting using Spring Security or integrate with services like Guava RateLimiter to prevent brute force attacks.

96. How would you ensure that your Spring Security configuration is scalable for a high-traffic application?
    Use distributed session management (e.g., Redis), enable caching for authorization checks, and optimize authentication queries (e.g., caching user roles).

97. How do you implement content security policies (CSP) in your Spring Boot application?
    Add Content-Security-Policy headers to HTTP responses by configuring Spring Security's http.headers() method or by using a custom filter.

98. How would you secure sensitive endpoints that are accessible via APIs in a mobile application?
    Use OAuth2 tokens or JWT tokens to secure the endpoints and ensure secure communication by enabling HTTPS.

99. How would you implement security measures to protect against session hijacking in Spring Security?
    Enable secure cookies (HttpOnly, Secure flags), use session fixation protection, and employ multi-factor authentication (MFA).

100. How would you ensure that user data is protected at rest and in transit?
     Encrypt sensitive data using AES encryption for data at rest, and use TLS (HTTPS) for securing data in transit.