Frequently Answered Questions (FAQ)

Spring Security provides you with a very flexible framework for your authentication and authorization requirements, but there are many other considerations for building a secure application that are outside its scope. Web applications are vulnerable to all kinds of attacks which you should be familiar with, preferably before you start development so you can design and code with them in mind from the beginning. Check out the OWASP web site for information on the major issues facing web application developers and the countermeasures you can use against them.

Let's assume you're developing an enterprise application based on Spring. There are four security concerns you typically need to address: authentication, web request security, service layer security (i.e. your methods that implement business logic), and domain object instance security (i.e. different domain objects have different permissions). With these typical requirements in mind:

For simple applications, servlet specification security may just be enough. Although when considered within the context of web container portability, configuration requirements, limited web request security flexibility, and non-existent services layer and domain object instance security, it becomes clear why developers often look to alternative solutions.

Spring Security 2.0.x requires a minimum JDK version of 1.4 and is built against Spring 2.0.x. It should also be compatible with applications using Spring 2.5.x.

Spring Security 3.0 requires JDK 1.5 as a minimum and will also require Spring 3.0.

Realistically, you need an understanding of the technolgies you are intending to use before you can successfully build applications with them. Security is complicated. Setting up a simple configuration using a login form and some hard-coded users using Spring Security's namespace is reasonably straightforward. Moving to using a backed JDBC database is also easy enough. But if you try and jump straight to a complicated deployment scenario like this you will almost certainly be frustrated. There is a big jump in the learning curve required to set up systems like CAS, configure LDAP servers and install SSL certificates properly. So you need to take things one step at a time.

From a Spring Security perspective, the first thing you should do is follow the “Getting Started” guide on the web site. This will take you through a series of steps to get up and running and get some idea of how the framework operates. If you are using other technologies which you aren't familiar with then you should do some research and try to make sure you can use them in isolation before combining them in a complex system.

A common user problem with infinite loop and redirecting to the login page is caused by accidently configuring the login page as a "secured" resource. Make sure your configuration allows anonymous access to the login page, either by excluding it from the security filter chain or marking it as requiring ROLE_ANONYMOUS.

If your AccessDecisionManager includes an AuthenticatedVoter, you can use the attribute "IS_AUTHENTICATED_ANONYMOUSLY". This is automatically available if you are using the standard namespace configuration setup.

From Spring Security 2.0.1 onwards, when you are using namespace-based configuration, a check will be made on loading the application context and a warning message logged if your login page appears to be protected.

This is a debug level message which occurs the first time an anonymous user attempts to access a protected resource.

    DEBUG [ExceptionTranslationFilter] - Access is denied (user is anonymous); redirecting to authentication entry point
    org.springframework.security.AccessDeniedException: Access is denied
    at org.springframework.security.vote.AffirmativeBased.decide(AffirmativeBased.java:68)
    at org.springframework.security.intercept.AbstractSecurityInterceptor.beforeInvocation(AbstractSecurityInterceptor.java:262)
                

It is normal and shouldn't be anything to worry about.

The most common reason for this is that your browser has cached the page and you are seeing a copy which is being retrieved from the browsers cache. Verify this by checking whether the browser is actually sending the request (check your server access logs, the debug log or use a suitable browser debugging plugin such as “Tamper Data” for Firefox). This has nothing to do with Spring Security and you should configure your application or server to set the appropriate Cache-Control response headers. Note that SSL requests are never cached.

This is a another debug level message which occurs the first time an anonymous user attempts to access a protected resource, but when you do not have an AnonymousAuthenticationFilter in your filter chain configuration.

    DEBUG [ExceptionTranslationFilter] - Authentication exception occurred; redirecting to authentication entry point
    org.springframework.security.AuthenticationCredentialsNotFoundException:
                   An Authentication object was not found in the SecurityContext
    at org.springframework.security.intercept.AbstractSecurityInterceptor.credentialsNotFound(AbstractSecurityInterceptor.java:342)
    at org.springframework.security.intercept.AbstractSecurityInterceptor.beforeInvocation(AbstractSecurityInterceptor.java:254)
                

It is normal and shouldn't be anything to worry about.

Browsers generally maintain a single session per browser instance. You cannot have two separate sessions at once. So if you log in again in another window or tab you are just reauthenticating in the same session. The server doesn't know anything about tabs, windows or browser instances. All it sees are HTTP requests and it ties those to a particular session according to the value of the the JSESSIONID cookie that they contain. When a user authenticates during a session, Spring Security's concurrent session control checks the number of other authenticated sessions that they have. If they are already authenticated with the same session, then re-authenticating will have no effect.

With the default configuration, Spring Security invalidates the existing session when the user authenticates and creates a new one, transferring the session data to it. The intention is to change the session identifier to prevent “session-fixation” attacks. You can find more about this online and in the reference manual.

This happens because sessions created under HTTPS, for which the session cookie is marked as “secure”, cannot subsequently be used under HTTP. The browser will not send the cookie back to the server and any session state will be lost (including the security context information). Starting a session in HTTP first should work as the session cookie won't be marked as secure.

Sessions are maintained either by exchanging a session cookie or by adding the a jsessionid parameter to URLs (this happens automatically if you are using JSTL to output URLs, or if you call HttpServletResponse.encodeUrl on URLs (before a redirect, for example). If clients have cookies disabled, and you are not rewriting URLs to include the jsessionid, then the session will be lost. Note that the use of cookies is preferred for security reasons, as it does not expose the session information in the URL.

Make sure you have added the listener to your web.xml file. It is essential to make sure that the Spring Security session registry is notified when a session is destroyed. Without it, the session information will not be removed from the registry.

    <listener>
        <listener-class>org.springframework.security.ui.session.HttpSessionEventPublisher</listener-class>
    </listener> 
            

This usually means that the user's application is creating a session somewhere, but that they aren't aware of it. The most common culprit is a JSP. Many people aren't aware that JSPs create sessions by default. To prevent a JSP from creating a session, add the directive <%@ page session="false" %> to the top of the page.

If you are having trouble working out where a session is being created, you can add some debugging code to track down the location(s). One way to do this would be to add a javax.servlet.http.HttpSessionListener to your application, which calls Thread.dumpStack() in the sessionCreated method.

Filters are not applied by default to forwards or includes. If you really want the security filters to be applied to forwards and/or includes, then you have to configure these explicitly in your web.xml using the <dispatcher> element, a child element of <filter-mapping>.

The application context which holds the Spring MVC beans for the dispatcher servlet is a child application context of the main application context which is loaded using the ContextLoaderListener you define in your web.xml. The beans in the child context are not visible in the parent context so you need to either move the <global-method-security> declaration to the web context or moved the beans you want secured into the main application context.

Generally we would recommend applying method security at the service layer rather than on individual web controllers.

If you have excluded the request from the security filter chain using the attribute filters='none' in the <intercept-url> element that matches the URL pattern, then the SecurityContextHolder will not be populated for that request. Check the debug log to see whether the request is passing through the filter chain. (You are reading the debug log, right?).

The best way of locating classes is by installing the Spring Security source in your IDE. The distribution includes source jars for each of the modules the project is divided up into. Add these to your project source path and you can navigate directly to Spring Security classes (Ctrl-Shift-T in Eclipse). This also makes debugging easer and allows you to troubleshoot exceptions by looking directly at the code where they occur to see what's going on there.

There is a general overview of what beans are created by the namespace in the namespace appendix of the reference guide. There is also a detailed blog article called “Behind the Spring Security Namespace” on blog.springsource.com. If want to know the full details then the code is in the spring-security-config module within the Spring Security 3.0 distribution. You should probably read the chapters on namespace parsing in the standard Spring Framework reference documentation first.

Spring Security has a voter-based architecture which means that an access decision is made by a series of AccessDecisionVoters. The voters act on the “configuration attributes” which are specified for a secured resource (such as a method invocation). With this approach, not all attributes may be relevant to all voters and a voter needs to know when it should ignore an attribute (abstain) and when it should vote to grant or deny access based on the attribute value. The most common voter is the RoleVoter which by default votes whenever it finds an attribute with the “ROLE_” prefix. It makes a simple comparison of the attribute (such as “ROLE_USER”) with the name names of the authorities which the current user has been assigned. If it finds a match (they have an authority called “ROLE_USER”), it votes to grant access, otherwise it votes to deny access.

The prefix can be changed by setting the rolePrefix property of RoleVoter. If you only need to use roles in your application and have no need for other custom voters, then you can set the prefix to a blank string, in which case the RoleVoter will treat all attributes as roles.

It will depend on what features you are using and what type of application you are developing. With Spring Security 3.0, the project jars are divided into clearly distinct areas of functionality, so it is straightforward to work out which Spring Security jars you need from your application requirements. All applications will need the spring-security-core jar. If you're developing a web application, you need the spring-security-web jar. If you're using security namespace configuration you need the spring-security-config jar, for LDAP support you need the spring-security-ldap jar and so on.

For third-party jars the situation isn't always quite so obvious. A good starting point is to copy those from one of the pre-built sample applications WEB-INF/lib directories. For a basic application, you can start with the tutorial sample. If you want to use LDAP, with an embedded test server, then use the LDAP sample as a starting point.

If you are building your project with maven, then adding the appropriate Spring Security modules as dependencies to your pom.xml will automatically pull in the core jars that the framework requires. Any which are marked as "optional" in the Spring Security POM files will have to be added to your own pom.xml file if you need them.

This question comes up repeatedly in the Spring Security forum so you will find more information there by searching the archives (or through google).

The submitted login information is processed by an instance of UsernamePasswordAuthenticationFilter. You will need to customize this class to handle the extra data field(s). One option is to use your own customized authentication token class (rather than the standard UsernamePasswordAuthenticationToken), another is simply to concatenate the extra fields with the username (for example, using a ":" as the separator) and pass them in the username property of UsernamePasswordAuthenticationToken.

You will also need to customize the actual authentication process. If you are using a custom authentication token class, for example, you will have to write an AuthenticationProvider to handle it (or extend the standard DaoAuthenticationProvider). If you have concatenated the fields, you can implement your own UserDetailsService which splits them up and loads the appropriate user data for authentication.

You can't do this, since the fragment is not transmitted from the browser to the server. The URLs above are identical from the server's perspective. This is a common question from GWT users.

Obviously you can't (without resorting to something like thread-local variables) since the only information supplied to the interface is the username. Instead of implementing UserDetailsService, you should implement AuthenticationProvider directly and extract the information from the supplied Authentication token.

In a standard web setup, the getDetails() method on the Authentication object will return an instance of WebAuthenticationDetails. If you need additional information, you can inject a custom AuthenticationDetailsSource into the authentication filter you are using. If you are using the namespace, for example with the <form-login> element, then you should remove this element and replace it with a <custom-filter> declaration pointing to an explicitly configured UsernamePasswordAuthenticationFilter.

You can't, since the UserDetailsService has no awareness of the servlet API. If you want to store custom user data, then you should customize the UserDetails object which is returned. This can then be accessed at any point, via the thread-local SecurityContextHolder. A call to SecurityContextHolder.getContext().getAuthentication().getPrincipal() will return this custom object.

If you really need to access the session, then it must be done by customizing the web tier.

People often ask about how to store the mapping between secured URLs and security metadata attributes in a database, rather than in the application context.

The first thing you should ask yourself is if you really need to do this. If an application requires securing, then it also requires that the security be tested thoroughly based on a defined policy. It may require auditing and acceptance testing before being rolled out into a production environment. A security-conscious organization should be aware that the benefits of their diligent testing process could be wiped out instantly by allowing the security settings to be modified at runtime by changing a row or two in a configuration database. If you have taken this into account (perhaps using multiple layers of security within your application) then Spring Security allows you to fully customize the source of security metadata. You can make it fully dynamic if you choose.

Both method and web security are protected by subclasses of AbstractSecurityInterceptor which is configured with a SecurityMetadataSource from which it obtains the metadata for a particular method or filter invocation. For web security, the interceptor class is FilterSecurityInterceptor and it uses the marker interface FilterInvocationSecurityMetadataSource. The “secured object” type it operates on is a FilterInvocation. The default implementation which is used (both in the namespace <http> and when configuring the interceptor explicitly, stores the list of URL patterns and their corresponding list of “configuration attributes” (instances of ConfigAttribute) in an in-memory map.

To load the data from an alternative source, you must be using an explicitly declared security filter chain (typically Spring Security's FilterChainProxy) in order to customize the FilterSecurityInterceptor bean. You can't use the namespace. You would then implement FilterInvocationSecurityMetadataSource to load the data as you please for a particular FilterInvocation^[1]. A very basic outline would look something like this:

  public class MyFilterSecurityMetadataSource implements FilterInvocationSecurityMetadataSource {

    public List<ConfigAttribute> getAttributes(Object object) {
      FilterInvocation fi = (FilterInvocation) object;
        String url = fi.getRequestUrl();
        String httpMethod = fi.getRequest().getMethod();
        List<ConfigAttribute> attributes = new ArrayList<ConfigAttribute>();

        // Lookup your database (or other source) using this information and populate the
        // list of attributes

        return attributes;
    }

    public Collection<ConfigAttribute> getAllConfigAttributes() {
      return null;
    }

    public boolean supports(Class<?> clazz) {
      return FilterInvocation.class.isAssignableFrom(clazz);
    }
  }
  

For more information, look at the code for DefaultFilterInvocationSecurityMetadataSource.

The LdapAuthenticationProvider bean (which handles normal LDAP authentication in Spring Security) is configured with two separate strategy interfaces, one which performs the authenticatation and one which loads the user authorities, called LdapAuthenticator and LdapAuthoritiesPopulator respectively. The DefaultLdapAuthoritiesPopulator loads the user authorities from the LDAP directory and has various configuration parameters to allow you to specify how these should be retrieved.

To use JDBC instead, you can implement the interface yourself, using whatever SQL is appropriate for your schema:

  public class MyAuthoritiesPopulator implements LdapAuthoritiesPopulator {
    @Autowired
    JdbcTemplate template;

    List<GrantedAuthority> getGrantedAuthorities(DirContextOperations userData, String username) {
      List<GrantedAuthority> = template.query("select role from roles where username = ?",
                                                   new String[] {username},
                                                   new RowMapper<GrantedAuthority>() {
        /**
         *  We're assuming here that you're using the standard convention of using the role
         *  prefix "ROLE_" to mark attributes which are supported by Spring Security's RoleVoter.
         */
        public GrantedAuthority mapRow(ResultSet rs, int rowNum) throws SQLException {
          return new GrantedAuthorityImpl("ROLE_" + rs.getString(1);
        }
      }
    }
  }
  

You would then add a bean of this type to your application context and inject it into the LdapAuthenticationProvider. This is covered in the section on configuring LDAP using explicit Spring beans in the LDAP chapter of the reference manual. Note that you can't use the namespace for configuration in this case. You should also consult the Javadoc for the relevant classes and interfaces.

The namespace functionality is intentionally limited, so it doesn't cover everything that you can do with plain beans. If you want to do something simple, like modify a bean, or inject a different dependency, you can do this by adding a BeanPostProcessor to your configuration. More information can be found in the Spring Reference Manual. In order to do this, you need to know a bit about which beans are created, so you should also read the blog article in the above question on how the namespace maps to Spring beans.

Normally, you would add the functionality you require to the postProcessBeforeInitialization method of BeanPostProcessor. Let's say that you want to customize the AuthenticationDetailsSource used by the UsernamePasswordAuthenticationFilter, (created by the form-login element). You want to extract a particular header called CUSTOM_HEADERfrom the request and make use of it while authenticating the user. The processor class would look like this:

public class BeanPostProcessor implements BeanPostProcessor {

    public Object postProcessAfterInitialization(Object bean, String name) {
        if (bean instanceof UsernamePasswordAuthenticationFilter) {
            System.out.println("********* Post-processing " + name);
            ((UsernamePasswordAuthenticationFilter)bean).setAuthenticationDetailsSource(
                    new AuthenticationDetailsSource() {
                        public Object buildDetails(Object context) {
                            return ((HttpServletRequest)context).getHeader("CUSTOM_HEADER");
                        }
                    });
        }
        return bean;
    }

    public Object postProcessBeforeInitialization(Object bean, String name) {
        return bean;
    }
}

You would then register this bean in your application context. Spring will automatically invoke it on the beans defined in the application context.