Introduction to Spring Method Security

1. Introduction

Simply put, Spring Security supports authorization semantics at the method level.

Typically, we could secure our service layer by, for example, restricting which roles are able to execute a particular method – and test it using dedicated method-level security test support.

In this article, we’re going to review the use of some security annotations first. Then, we’ll focus on testing our method security with different strategies.

2. Enabling Method Security

First of all, to use Spring Method Security, we need to add the spring-security-config dependency:

<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-config</artifactId>
</dependency>

We can find its latest version on Maven Central.

If we want to use Spring Boot, we can use the spring-boot-starter-security dependency which includes spring-security-config:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

Again, the latest version can be found on Maven Central.

Next, we need to enable global Method Security:

@Configuration
@EnableGlobalMethodSecurity(
  prePostEnabled = true, 
  securedEnabled = true, 
  jsr250Enabled = true)
public class MethodSecurityConfig 
  extends GlobalMethodSecurityConfiguration {
}

• The prePostEnabled property enables Spring Security pre/post annotations
• The securedEnabled property determines if the @Secured annotation should be enabled
• The jsr250Enabled property allows us to use the @RoleAllowed annotation

We’ll explore more about these annotations in the next section.

3. Applying Method Security

3.1. Using @Secured Annotation

The @Secured annotation is used to specify a list of roles on a method. Hence, a user only can access that method if she has at least one of the specified roles.

Let’s define a getUsername method:

@Secured("ROLE_VIEWER")
public String getUsername() {
    SecurityContext securityContext = SecurityContextHolder.getContext();
    return securityContext.getAuthentication().getName();
}

Here, the @Secured(“ROLE_VIEWER”) annotation defines that only users who have the role ROLE_VIEWER are able to execute the getUsername method.

Besides, we can define a list of roles in a @Secured annotation:

@Secured({ "ROLE_VIEWER", "ROLE_EDITOR" })
public boolean isValidUsername(String username) {
    return userRoleRepository.isValidUsername(username);
}

In this case, the configuration states that if a user has either ROLE_VIEWER or ROLE_EDITOR, that user can invoke the isValidUsername method.

The @Secured annotation doesn’t support Spring Expression Language (SpEL).

3.2. Using @RoleAllowed Annotation

The @RoleAllowed annotation is the JSR-250’s equivalent annotation of the @Secured annotation.  

Basically, we can use the @RoleAllowed annotation in a similar way as @Secured. Thus, we could re-define getUsername and isValidUsername methods:

@RolesAllowed("ROLE_VIEWER")
public String getUsername2() {
    //...
}
    
@RolesAllowed({ "ROLE_VIEWER", "ROLE_EDITOR" })
public boolean isValidUsername2(String username) {
    //...
}

Similarly, only the user who has role ROLE_VIEWER can execute getUsername2.

Again, a user is able to invoke isValidUsername2 only if she has at least one of ROLE_VIEWER or ROLER_EDITOR roles.

3.3. Using @PreAuthorize and @PostAuthorize Annotations

Both @PreAuthorize and @PostAuthorize annotations provide expression-based access control. Hence, predicates can be written using SpEL (Spring Expression Language).

The @PreAuthorize annotation checks the given expression before entering the method, whereas, the @PostAuthorize annotation verifies it after the execution of the method and could alter the result.

Now, let’s declare a getUsernameInUpperCase method as below:

@PreAuthorize("hasRole('ROLE_VIEWER')")
public String getUsernameInUpperCase() {
    return getUsername().toUpperCase();
}

The @PreAuthorize(“hasRole(‘ROLE_VIEWER’)”) has the same meaning as @Secured(“ROLE_VIEWER”) which we used in the previous section. Feel free to discover more security expressions details in previous articles.

Consequently, the annotation @Secured({“ROLE_VIEWER”,”ROLE_EDITOR”}) can be replaced with @PreAuthorize(“hasRole(‘ROLE_VIEWER’) or hasRole(‘ROLE_EDITOR’)”):

@PreAuthorize("hasRole('ROLE_VIEWER') or hasRole('ROLE_EDITOR')")
public boolean isValidUsername3(String username) {
    //...
}

Moreover, we can actually use the method argument as part of the expression:

@PreAuthorize("#username == authentication.principal.username")
public String getMyRoles(String username) {
    //...
}

Here, a user can invoke the getMyRoles method only if the value of the argument username is the same as current principal’s username.

It’s worth to note that @PreAuthorize expressions can be replaced by @PostAuthorize ones.

Let’s rewrite getMyRoles:

@PostAuthorize("#username == authentication.principal.username")
public String getMyRoles2(String username) {
    //...
}

In the previous example, however, the authorization would get delayed after the execution of the target method.

Additionally, the @PostAuthorize annotation provides the ability to access the method result:

@PostAuthorize
  ("returnObject.username == authentication.principal.nickName")
public CustomUser loadUserDetail(String username) {
    return userRoleRepository.loadUserByUserName(username);
}

In this example, the loadUserDetail method would only execute successfully if the username of the returned CustomUser is equal to the current authentication principal’s nickname.

In this section, we mostly use simple Spring expressions. For more complex scenarios, we could create custom security expressions.

3.4. Using @PreFilter and @PostFilter Annotations

Spring Security provides the @PreFilter annotation to filter a collection argument before executing the method:

@PreFilter("filterObject != authentication.principal.username")
public String joinUsernames(List<String> usernames) {
    return usernames.stream().collect(Collectors.joining(";"));
}

In this example, we’re joining all usernames except for the one who is authenticated.

Here, our expression uses the name filterObject to represent the current object in the collection.

However, if the method has more than one argument which is a collection type, we need to use the filterTarget property to specify which argument we want to filter:

@PreFilter
  (value = "filterObject != authentication.principal.username",
  filterTarget = "usernames")
public String joinUsernamesAndRoles(
  List<String> usernames, List<String> roles) {
 
    return usernames.stream().collect(Collectors.joining(";")) 
      + ":" + roles.stream().collect(Collectors.joining(";"));
}

Additionally, we can also filter the returned collection of a method by using @PostFilter annotation:

@PostFilter("filterObject != authentication.principal.username")
public List<String> getAllUsernamesExceptCurrent() {
    return userRoleRepository.getAllUsernames();
}

In this case, the name filterObject refers to the current object in the returned collection.

With that configuration, Spring Security will iterate through the returned list and remove any value which matches with the principal’s username.

More detail of @PreFilter and @PostFilter can be found in the Spring Security – @PreFilter and @PostFilter article.

3.5. Method Security Meta-Annotation

We typically find ourselves in a situation where we protect different methods using the same security configuration.

In this case, we can define a security meta-annotation:

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@PreAuthorize("hasRole('VIEWER')")
public @interface IsViewer {
}

Next, we can directly use the @IsViewer annotation to secure our method:

@IsViewer
public String getUsername4() {
    //...
}

Security meta-annotations are a great idea because they add more semantics and decouple our business logic from the security framework.

3.6. Security Annotation at the Class Level

If we find ourselves using the same security annotation for every method within one class, we can consider putting that annotation at class level:

@Service
@PreAuthorize("hasRole('ROLE_ADMIN')")
public class SystemService {

    public String getSystemYear(){
        //...
    }
 
    public String getSystemDate(){
        //...
    }
}

In above example, the security rule hasRole(‘ROLE_ADMIN’) will be applied to both getSystemYear and getSystemDate methods.

3.7. Multiple Security Annotations on a Method

We can also use multiple security annotations on one method:

@PreAuthorize("#username == authentication.principal.username")
@PostAuthorize("returnObject.username == authentication.principal.nickName")
public CustomUser securedLoadUserDetail(String username) {
    return userRoleRepository.loadUserByUserName(username);
}

Hence, Spring will verify authorization both before and after the execution of the securedLoadUserDetail method.

4. Important Considerations

There are two points we’d like to remind regarding method security:

• By default, Spring AOP proxying is used to apply method security – if a secured method A is called by another method within the same class, security in A is ignored altogether. This means method A will execute without any security checking. The same applies to private methods
• Spring SecurityContext is thread-bound – by default, the security context isn’t propagated to child-threads. For more information, we can refer to Spring Security Context Propagation article

5. Testing Method Security

5.1. Configuration

To test Spring Security with JUnit, we need the spring-security-test dependency:

<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-test</artifactId>
</dependency>

We don’t need to specify the dependency version because we’re using the Spring Boot plugin. Latest versions of this dependency can be found on Maven Central.

Next, let’s configure a simple Spring Integration test by specifying the runner and the ApplicationContext configuration:

@RunWith(SpringRunner.class)
@ContextConfiguration
public class TestMethodSecurity {
    // ...
}

5.2. Testing Username and Roles 

Now that our configuration is ready, let’s try to test our getUsername method which is secured by the annotation @Secured(“ROLE_VIEWER”):

@Secured("ROLE_VIEWER")
public String getUsername() {
    SecurityContext securityContext = SecurityContextHolder.getContext();
    return securityContext.getAuthentication().getName();
}

Since we use the @Secured annotation here, it requires a user to be authenticated to invoke the method. Otherwise, we’ll get an AuthenticationCredentialsNotFoundException.

Hence, we need to provide a user to test our secured method. To achieve this, we decorate the test method with @WithMockUser and provide a user and roles:

@Test
@WithMockUser(username = "john", roles = { "VIEWER" })
public void givenRoleViewer_whenCallGetUsername_thenReturnUsername() {
    String userName = userRoleService.getUsername();
    
    assertEquals("john", userName);
}

We’ve provided an authenticated user whose username is john and whose role is ROLE_VIEWER. If we don’t specify the username or role, the default username is user and default role is ROLE_USER.

Note that it isn’t necessary to add the ROLE_ prefix here, Spring Security will add that prefix automatically.

If we don’t want to have that prefix, we can consider using authority instead of role. 

For example, let’s declare a getUsernameInLowerCase method:

@PreAuthorize("hasAuthority('SYS_ADMIN')")
public String getUsernameLC(){
    return getUsername().toLowerCase();
}

We could test that using authorities:

@Test
@WithMockUser(username = "JOHN", authorities = { "SYS_ADMIN" })
public void givenAuthoritySysAdmin_whenCallGetUsernameLC_thenReturnUsername() {
    String username = userRoleService.getUsernameInLowerCase();

    assertEquals("john", username);
}

Conveniently, if we want to use the same user for many test cases, we can declare the @WithMockUser annotation at test class:

@RunWith(SpringRunner.class)
@ContextConfiguration
@WithMockUser(username = "john", roles = { "VIEWER" })
public class TestWithMockUserAtClassLevel {
    //...
}

If we wanted to run our test as an anonymous user, we could use the @WithAnonymousUser annotation:

@Test(expected = AccessDeniedException.class)
@WithAnonymousUser
public void givenAnomynousUser_whenCallGetUsername_thenAccessDenied() {
    userRoleService.getUsername();
}

In the example above, we expect an AccessDeniedException because the anonymous user isn’t granted the role ROLE_VIEWER or the authority SYS_ADMIN.

5.3. Testing with a Custom UserDetailsService

For most applications, it’s common to use a custom class as authentication principal. In this case, the custom class needs to implement the org.springframework.security.core.userdetails.UserDetails interface.

In this article, we declare a CustomUser class which extends the existing implementation of UserDetails, which is org.springframework.security.core.userdetails.User:

public class CustomUser extends User {
    private String nickName;
    // getter and setter
}

Let’s take back the example with the @PostAuthorize annotation in section 3:

@PostAuthorize("returnObject.username == authentication.principal.nickName")
public CustomUser loadUserDetail(String username) {
    return userRoleRepository.loadUserByUserName(username);
}

In this case, the method would only execute successfully if the username of the returned CustomUser is equal to the current authentication principal’s nickname.

If we wanted to test that method, we could provide an implementation of UserDetailsService which could load our CustomUser based on the username:

@Test
@WithUserDetails(
  value = "john", 
  userDetailsServiceBeanName = "userDetailService")
public void whenJohn_callLoadUserDetail_thenOK() {
 
    CustomUser user = userService.loadUserDetail("jane");

    assertEquals("jane", user.getNickName());
}

Here, the @WithUserDetails annotation states that we’ll use a UserDetailsService to initialize our authenticated user. The service is referred by the userDetailsServiceBeanName property. This UserDetailsService might be a real implementation or a fake for testing purposes.

Additionally, the service will use the value of the property value as the username to load UserDetails.

Conveniently, we can also decorate with a @WithUserDetails annotation at the class level, similarly to what we did with the @WithMockUser annotation.

5.4. Testing with Meta Annotations

We often find ourselves reusing the same user/roles over and over again in various tests.

For these situations, it’s convenient to create a meta-annotation.

Taking back the previous example @WithMockUser(username=”john”, roles={“VIEWER”}), we can declare a meta-annotation as:

@Retention(RetentionPolicy.RUNTIME)
@WithMockUser(value = "john", roles = "VIEWER")
public @interface WithMockJohnViewer { }

Then we can simply use @WithMockJohnViewer in our test:

@Test
@WithMockJohnViewer
public void givenMockedJohnViewer_whenCallGetUsername_thenReturnUsername() {
    String userName = userRoleService.getUsername();

    assertEquals("john", userName);
}

Likewise, we can use meta-annotations to create domain-specific users using @WithUserDetails.

6. Conclusion

In this tutorial, we’ve explored various options for using Method Security in Spring Security.

We also have gone through a few techniques to easily test method security and learned how to reuse mocked users in different tests.

All examples of this tutorial can be found over on Github.