13. WebClient for Servlet Environments

Note

The following documentation is for use within Servlet environments. For all other environments, refer to WebClient for Reactive environments.

Spring Framework has built in support for setting a Bearer token.

webClient.get()
    .headers(h -> h.setBearerAuth(token))
    ...

Spring Security builds on this support to provide additional benefits:

  • Spring Security will automatically refresh expired tokens (if a refresh token is present)

  • If an access token is requested and not present, Spring Security will automatically request the access token.

  • For authorization_code this involves performing the redirect and then replaying the original request

    • For client_credentials the token is simply requested and saved
  • Support for the ability to transparently include the current OAuth token or explicitly select which token should be used.

13.1 WebClient OAuth2 Setup

The first step is ensuring to setup the WebClient correctly. An example of setting up WebClient in a servlet environment can be found below:

@Bean
WebClient webClient(ClientRegistrationRepository clientRegistrations,
        OAuth2AuthorizedClientRepository authorizedClients) {
    ServletOAuth2AuthorizedClientExchangeFilterFunction oauth =
            new ServletOAuth2AuthorizedClientExchangeFilterFunction(clientRegistrations, authorizedClients);
    // (optional) explicitly opt into using the oauth2Login to provide an access token implicitly
    // oauth.setDefaultOAuth2AuthorizedClient(true);
    // (optional) set a default ClientRegistration.registrationId
    // oauth.setDefaultClientRegistrationId("client-registration-id");
    return WebClient.builder()
            .apply(oauth2.oauth2Configuration())
            .build();
}

13.2 Implicit OAuth2AuthorizedClient

If we set defaultOAuth2AuthorizedClient to true in our setup and the user authenticated with oauth2Login (i.e. OIDC), then the current authentication is used to automatically provide the access token. Alternatively, if we set defaultClientRegistrationId to a valid ClientRegistration id, that registration is used to provide the access token. This is convenient, but in environments where not all endpoints should get the access token, it is dangerous (you might provide the wrong access token to an endpoint).

Mono<String> body = this.webClient
        .get()
        .uri(this.uri)
        .retrieve()
        .bodyToMono(String.class);

13.3 Explicit OAuth2AuthorizedClient

The OAuth2AuthorizedClient can be explicitly provided by setting it on the request attributes. In the example below we resolve the OAuth2AuthorizedClient using Spring WebFlux or Spring MVC argument resolver support. However, it does not matter how the OAuth2AuthorizedClient is resolved.

@GetMapping("/explicit")
Mono<String> explicit(@RegisteredOAuth2AuthorizedClient("client-id") OAuth2AuthorizedClient authorizedClient) {
    return this.webClient
            .get()
            .uri(this.uri)
            .attributes(oauth2AuthorizedClient(authorizedClient))
            .retrieve()
            .bodyToMono(String.class);
}

13.4 clientRegistrationId

Alternatively, it is possible to specify the clientRegistrationId on the request attributes and the WebClient will attempt to lookup the OAuth2AuthorizedClient . If it is not found, one will automatically be acquired.

Mono<String> body = this.webClient
        .get()
        .uri(this.uri)
        .attributes(clientRegistrationId("client-id"))
        .retrieve()
        .bodyToMono(String.class);

13.5 JSP Tag Libraries

Spring Security has its own taglib which provides basic support for accessing security information and applying security constraints in JSPs.

13.5.1 Declaring the Taglib

To use any of the tags, you must have the security taglib declared in your JSP:

<%@ taglib prefix="sec" uri="http://www.springframework.org/security/tags" %>

13.5.2 The authorize Tag

This tag is used to determine whether its contents should be evaluated or not. In Spring Security 3.0, it can be used in two ways [21]. The first approach uses a web-security expression, specified in the access attribute of the tag. The expression evaluation will be delegated to the SecurityExpressionHandler<FilterInvocation> defined in the application context (you should have web expressions enabled in your <http> namespace configuration to make sure this service is available). So, for example, you might have

<sec:authorize access="hasRole('supervisor')">

This content will only be visible to users who have the "supervisor" authority in their list of <tt>GrantedAuthority</tt>s.

</sec:authorize>

When used in conjuction with Spring Security’s PermissionEvaluator, the tag can also be used to check permissions. For example:

<sec:authorize access="hasPermission(#domain,'read') or hasPermission(#domain,'write')">

This content will only be visible to users who have read or write permission to the Object found as a request attribute named "domain".

</sec:authorize>

A common requirement is to only show a particular link, if the user is actually allowed to click it. How can we determine in advance whether something will be allowed? This tag can also operate in an alternative mode which allows you to define a particular URL as an attribute. If the user is allowed to invoke that URL, then the tag body will be evaluated, otherwise it will be skipped. So you might have something like

<sec:authorize url="/admin">

This content will only be visible to users who are authorized to send requests to the "/admin" URL.

</sec:authorize>

To use this tag there must also be an instance of WebInvocationPrivilegeEvaluator in your application context. If you are using the namespace, one will automatically be registered. This is an instance of DefaultWebInvocationPrivilegeEvaluator , which creates a dummy web request for the supplied URL and invokes the security interceptor to see whether the request would succeed or fail. This allows you to delegate to the access-control setup you defined using intercept-url declarations within the <http> namespace configuration and saves having to duplicate the information (such as the required roles) within your JSPs. This approach can also be combined with a method attribute, supplying the HTTP method, for a more specific match.

The Boolean result of evaluating the tag (whether it grants or denies access) can be stored in a page context scope variable by setting the var attribute to the variable name, avoiding the need for duplicating and re-evaluating the condition at other points in the page.

Disabling Tag Authorization for Testing

Hiding a link in a page for unauthorized users doesn’t prevent them from accessing the URL. They could just type it into their browser directly, for example. As part of your testing process, you may want to reveal the hidden areas in order to check that links really are secured at the back end. If you set the system property spring.security.disableUISecurity to true , the authorize tag will still run but will not hide its contents. By default it will also surround the content with <span class="securityHiddenUI">…</span> tags. This allows you to display "hidden" content with a particular CSS style such as a different background colour. Try running the "tutorial" sample application with this property enabled, for example.

You can also set the properties spring.security.securedUIPrefix and spring.security.securedUISuffix if you want to change surrounding text from the default span tags (or use empty strings to remove it completely).

13.5.3 The authentication Tag

This tag allows access to the current Authentication object stored in the security context. It renders a property of the object directly in the JSP. So, for example, if the principal property of the Authentication is an instance of Spring Security’s UserDetails object, then using <sec:authentication property="principal.username" /> will render the name of the current user.

Of course, it isn’t necessary to use JSP tags for this kind of thing and some people prefer to keep as little logic as possible in the view. You can access the Authentication object in your MVC controller (by calling SecurityContextHolder.getContext().getAuthentication() ) and add the data directly to your model for rendering by the view.

13.5.4 The accesscontrollist Tag

This tag is only valid when used with Spring Security’s ACL module. It checks a comma-separated list of required permissions for a specified domain object. If the current user has all of those permissions, then the tag body will be evaluated. If they don’t, it will be skipped. An example might be

Warning

In general this tag should be considered deprecated. Instead use the Section 13.5.2, “The authorize Tag”.

<sec:accesscontrollist hasPermission="1,2" domainObject="${someObject}">

This will be shown if the user has all of the permissions represented by the values "1" or "2" on the given object.

</sec:accesscontrollist>

The permissions are passed to the PermissionFactory defined in the application context, converting them to ACL Permission instances, so they may be any format which is supported by the factory - they don’t have to be integers, they could be strings like READ or WRITE . If no PermissionFactory is found, an instance of DefaultPermissionFactory will be used. The AclService from the application context will be used to load the Acl instance for the supplied object. The Acl will be invoked with the required permissions to check if all of them are granted.

This tag also supports the var attribute, in the same way as the authorize tag.

13.5.5 The csrfInput Tag

If CSRF protection is enabled, this tag inserts a hidden form field with the correct name and value for the CSRF protection token. If CSRF protection is not enabled, this tag outputs nothing.

Normally Spring Security automatically inserts a CSRF form field for any <form:form> tags you use, but if for some reason you cannot use <form:form> , csrfInput is a handy replacement.

You should place this tag within an HTML <form></form> block, where you would normally place other input fields. Do NOT place this tag within a Spring <form:form></form:form> block. Spring Security handles Spring forms automatically.

<form method="post" action="/do/something">
    <sec:csrfInput />
    Name:
<input type="text" name="name" /> ... </form>

13.5.6 The csrfMetaTags Tag

If CSRF protection is enabled, this tag inserts meta tags containing the CSRF protection token form field and header names and CSRF protection token value. These meta tags are useful for employing CSRF protection within JavaScript in your applications.

You should place csrfMetaTags within an HTML <head></head> block, where you would normally place other meta tags. Once you use this tag, you can access the form field name, header name, and token value easily using JavaScript. JQuery is used in this example to make the task easier.

<!DOCTYPE html>
<html>
    <head>
        <title>CSRF Protected JavaScript Page</title>
        <meta name="description" content="This is the description for this page" />
        <sec:csrfMetaTags />
        <script type="text/javascript" language="javascript">

            var csrfParameter = $("meta[name='_csrf_parameter']").attr("content");
            var csrfHeader = $("meta[name='_csrf_header']").attr("content");
            var csrfToken = $("meta[name='_csrf']").attr("content");

            // using XMLHttpRequest directly to send an x-www-form-urlencoded request
            var ajax = new XMLHttpRequest();
            ajax.open("POST", "http://www.example.org/do/something", true);
            ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded data");
            ajax.send(csrfParameter + "=" + csrfToken + "&name=John&...");

            // using XMLHttpRequest directly to send a non-x-www-form-urlencoded request
            var ajax = new XMLHttpRequest();
            ajax.open("POST", "http://www.example.org/do/something", true);
            ajax.setRequestHeader(csrfHeader, csrfToken);
            ajax.send("...");

            // using JQuery to send an x-www-form-urlencoded request
            var data = {};
            data[csrfParameter] = csrfToken;
            data["name"] = "John";
            ...
            $.ajax({
                url: "http://www.example.org/do/something",
                type: "POST",
                data: data,
                ...
            });

            // using JQuery to send a non-x-www-form-urlencoded request
            var headers = {};
            headers[csrfHeader] = csrfToken;
            $.ajax({
                url: "http://www.example.org/do/something",
                type: "POST",
                headers: headers,
                ...
            });

        <script>
    </head>
    <body>
        ...
    </body>
</html>

If CSRF protection is not enabled, csrfMetaTags outputs nothing.

13.6 Java Authentication and Authorization Service (JAAS) Provider

13.6.1 Overview

Spring Security provides a package able to delegate authentication requests to the Java Authentication and Authorization Service (JAAS). This package is discussed in detail below.

13.6.2 AbstractJaasAuthenticationProvider

The AbstractJaasAuthenticationProvider is the basis for the provided JAAS AuthenticationProvider implementations. Subclasses must implement a method that creates the LoginContext . The AbstractJaasAuthenticationProvider has a number of dependencies that can be injected into it that are discussed below.

JAAS CallbackHandler

Most JAAS LoginModule s require a callback of some sort. These callbacks are usually used to obtain the username and password from the user.

In a Spring Security deployment, Spring Security is responsible for this user interaction (via the authentication mechanism). Thus, by the time the authentication request is delegated through to JAAS, Spring Security’s authentication mechanism will already have fully-populated an Authentication object containing all the information required by the JAAS LoginModule .

Therefore, the JAAS package for Spring Security provides two default callback handlers, JaasNameCallbackHandler and JaasPasswordCallbackHandler . Each of these callback handlers implement JaasAuthenticationCallbackHandler . In most cases these callback handlers can simply be used without understanding the internal mechanics.

For those needing full control over the callback behavior, internally AbstractJaasAuthenticationProvider wraps these JaasAuthenticationCallbackHandler s with an InternalCallbackHandler . The InternalCallbackHandler is the class that actually implements JAAS normal CallbackHandler interface. Any time that the JAAS LoginModule is used, it is passed a list of application context configured InternalCallbackHandler s. If the LoginModule requests a callback against the InternalCallbackHandler s, the callback is in-turn passed to the JaasAuthenticationCallbackHandler s being wrapped.

JAAS AuthorityGranter

JAAS works with principals. Even "roles" are represented as principals in JAAS. Spring Security, on the other hand, works with Authentication objects. Each Authentication object contains a single principal, and multiple GrantedAuthority s. To facilitate mapping between these different concepts, Spring Security’s JAAS package includes an AuthorityGranter interface.

An AuthorityGranter is responsible for inspecting a JAAS principal and returning a set of String s, representing the authorities assigned to the principal. For each returned authority string, the AbstractJaasAuthenticationProvider creates a JaasGrantedAuthority (which implements Spring Security’s GrantedAuthority interface) containing the authority string and the JAAS principal that the AuthorityGranter was passed. The AbstractJaasAuthenticationProvider obtains the JAAS principals by firstly successfully authenticating the user’s credentials using the JAAS LoginModule , and then accessing the LoginContext it returns. A call to LoginContext.getSubject().getPrincipals() is made, with each resulting principal passed to each AuthorityGranter defined against the AbstractJaasAuthenticationProvider.setAuthorityGranters(List) property.

Spring Security does not include any production AuthorityGranter s given that every JAAS principal has an implementation-specific meaning. However, there is a TestAuthorityGranter in the unit tests that demonstrates a simple AuthorityGranter implementation.

13.6.3 DefaultJaasAuthenticationProvider

The DefaultJaasAuthenticationProvider allows a JAAS Configuration object to be injected into it as a dependency. It then creates a LoginContext using the injected JAAS Configuration . This means that DefaultJaasAuthenticationProvider is not bound any particular implementation of Configuration as JaasAuthenticationProvider is.

InMemoryConfiguration

In order to make it easy to inject a Configuration into DefaultJaasAuthenticationProvider , a default in-memory implementation named InMemoryConfiguration is provided. The implementation constructor accepts a Map where each key represents a login configuration name and the value represents an Array of AppConfigurationEntry s. InMemoryConfiguration also supports a default Array of AppConfigurationEntry objects that will be used if no mapping is found within the provided Map . For details, refer to the class level javadoc of InMemoryConfiguration .

DefaultJaasAuthenticationProvider Example Configuration

While the Spring configuration for InMemoryConfiguration can be more verbose than the standarad JAAS configuration files, using it in conjuction with DefaultJaasAuthenticationProvider is more flexible than JaasAuthenticationProvider since it not dependant on the default Configuration implementation.

An example configuration of DefaultJaasAuthenticationProvider using InMemoryConfiguration is provided below. Note that custom implementations of Configuration can easily be injected into DefaultJaasAuthenticationProvider as well.

<bean id="jaasAuthProvider"
class="org.springframework.security.authentication.jaas.DefaultJaasAuthenticationProvider">
<property name="configuration">
<bean class="org.springframework.security.authentication.jaas.memory.InMemoryConfiguration">
<constructor-arg>
    <map>
    <!--
    SPRINGSECURITY is the default loginContextName
    for AbstractJaasAuthenticationProvider
    -->
    <entry key="SPRINGSECURITY">
    <array>
    <bean class="javax.security.auth.login.AppConfigurationEntry">
        <constructor-arg value="sample.SampleLoginModule" />
        <constructor-arg>
        <util:constant static-field=
            "javax.security.auth.login.AppConfigurationEntry$LoginModuleControlFlag.REQUIRED"/>
        </constructor-arg>
        <constructor-arg>
        <map></map>
        </constructor-arg>
        </bean>
    </array>
    </entry>
    </map>
    </constructor-arg>
</bean>
</property>
<property name="authorityGranters">
<list>
    <!-- You will need to write your own implementation of AuthorityGranter -->
    <bean class="org.springframework.security.authentication.jaas.TestAuthorityGranter"/>
</list>
</property>
</bean>

13.6.4 JaasAuthenticationProvider

The JaasAuthenticationProvider assumes the default Configuration is an instance of ConfigFile. This assumption is made in order to attempt to update the Configuration . The JaasAuthenticationProvider then uses the default Configuration to create the LoginContext .

Let’s assume we have a JAAS login configuration file, /WEB-INF/login.conf , with the following contents:

JAASTest {
    sample.SampleLoginModule required;
};

Like all Spring Security beans, the JaasAuthenticationProvider is configured via the application context. The following definitions would correspond to the above JAAS login configuration file:

<bean id="jaasAuthenticationProvider"
class="org.springframework.security.authentication.jaas.JaasAuthenticationProvider">
<property name="loginConfig" value="/WEB-INF/login.conf"/>
<property name="loginContextName" value="JAASTest"/>
<property name="callbackHandlers">
<list>
<bean
    class="org.springframework.security.authentication.jaas.JaasNameCallbackHandler"/>
<bean
    class="org.springframework.security.authentication.jaas.JaasPasswordCallbackHandler"/>
</list>
</property>
<property name="authorityGranters">
    <list>
    <bean class="org.springframework.security.authentication.jaas.TestAuthorityGranter"/>
    </list>
</property>
</bean>

13.6.5 Running as a Subject

If configured, the JaasApiIntegrationFilter will attempt to run as the Subject on the JaasAuthenticationToken . This means that the Subject can be accessed using:

Subject subject = Subject.getSubject(AccessController.getContext());

This integration can easily be configured using the jaas-api-provision attribute. This feature is useful when integrating with legacy or external API’s that rely on the JAAS Subject being populated.

13.7 CAS Authentication

13.7.1 Overview

JA-SIG produces an enterprise-wide single sign on system known as CAS. Unlike other initiatives, JA-SIG’s Central Authentication Service is open source, widely used, simple to understand, platform independent, and supports proxy capabilities. Spring Security fully supports CAS, and provides an easy migration path from single-application deployments of Spring Security through to multiple-application deployments secured by an enterprise-wide CAS server.

You can learn more about CAS at http://www.ja-sig.org/cas. You will also need to visit this site to download the CAS Server files.

13.7.2 How CAS Works

Whilst the CAS web site contains documents that detail the architecture of CAS, we present the general overview again here within the context of Spring Security. Spring Security 3.x supports CAS 3. At the time of writing, the CAS server was at version 3.4.

Somewhere in your enterprise you will need to setup a CAS server. The CAS server is simply a standard WAR file, so there isn’t anything difficult about setting up your server. Inside the WAR file you will customise the login and other single sign on pages displayed to users.

When deploying a CAS 3.4 server, you will also need to specify an AuthenticationHandler in the deployerConfigContext.xml included with CAS. The AuthenticationHandler has a simple method that returns a boolean as to whether a given set of Credentials is valid. Your AuthenticationHandler implementation will need to link into some type of backend authentication repository, such as an LDAP server or database. CAS itself includes numerous AuthenticationHandler s out of the box to assist with this. When you download and deploy the server war file, it is set up to successfully authenticate users who enter a password matching their username, which is useful for testing.

Apart from the CAS server itself, the other key players are of course the secure web applications deployed throughout your enterprise. These web applications are known as "services". There are three types of services. Those that authenticate service tickets, those that can obtain proxy tickets, and those that authenticate proxy tickets. Authenticating a proxy ticket differs because the list of proxies must be validated and often times a proxy ticket can be reused.

Spring Security and CAS Interaction Sequence

The basic interaction between a web browser, CAS server and a Spring Security-secured service is as follows:

  • The web user is browsing the service’s public pages. CAS or Spring Security is not involved.

  • The user eventually requests a page that is either secure or one of the beans it uses is secure. Spring Security’s ExceptionTranslationFilter will detect the AccessDeniedException or AuthenticationException .

  • Because the user’s Authentication object (or lack thereof) caused an AuthenticationException , the ExceptionTranslationFilter will call the configured AuthenticationEntryPoint . If using CAS, this will be the CasAuthenticationEntryPoint class.

  • The CasAuthenticationEntryPoint will redirect the user’s browser to the CAS server. It will also indicate a service parameter, which is the callback URL for the Spring Security service (your application). For example, the URL to which the browser is redirected might be https://my.company.com/cas/login?service=https%3A%2F%2Fserver3.company.com%2Fwebapp%2Flogin/cas.

  • After the user’s browser redirects to CAS, they will be prompted for their username and password. If the user presents a session cookie which indicates they’ve previously logged on, they will not be prompted to login again (there is an exception to this procedure, which we’ll cover later). CAS will use the PasswordHandler (or AuthenticationHandler if using CAS 3.0) discussed above to decide whether the username and password is valid.

  • Upon successful login, CAS will redirect the user’s browser back to the original service. It will also include a ticket parameter, which is an opaque string representing the "service ticket". Continuing our earlier example, the URL the browser is redirected to might be https://server3.company.com/webapp/login/cas?ticket=ST-0-ER94xMJmn6pha35CQRoZ.

  • Back in the service web application, the CasAuthenticationFilter is always listening for requests to /login/cas (this is configurable, but we’ll use the defaults in this introduction). The processing filter will construct a UsernamePasswordAuthenticationToken representing the service ticket. The principal will be equal to CasAuthenticationFilter.CAS_STATEFUL_IDENTIFIER , whilst the credentials will be the service ticket opaque value. This authentication request will then be handed to the configured AuthenticationManager .

  • The AuthenticationManager implementation will be the ProviderManager , which is in turn configured with the CasAuthenticationProvider . The CasAuthenticationProvider only responds to UsernamePasswordAuthenticationToken s containing the CAS-specific principal (such as CasAuthenticationFilter.CAS_STATEFUL_IDENTIFIER ) and CasAuthenticationToken s (discussed later).

  • CasAuthenticationProvider will validate the service ticket using a TicketValidator implementation. This will typically be a Cas20ServiceTicketValidator which is one of the classes included in the CAS client library. In the event the application needs to validate proxy tickets, the Cas20ProxyTicketValidator is used. The TicketValidator makes an HTTPS request to the CAS server in order to validate the service ticket. It may also include a proxy callback URL, which is included in this example: https://my.company.com/cas/proxyValidate?service=https%3A%2F%2Fserver3.company.com%2Fwebapp%2Flogin/cas&ticket=ST-0-ER94xMJmn6pha35CQRoZ&pgtUrl=https://server3.company.com/webapp/login/cas/proxyreceptor.

  • Back on the CAS server, the validation request will be received. If the presented service ticket matches the service URL the ticket was issued to, CAS will provide an affirmative response in XML indicating the username. If any proxy was involved in the authentication (discussed below), the list of proxies is also included in the XML response.

  • [OPTIONAL] If the request to the CAS validation service included the proxy callback URL (in the pgtUrl parameter), CAS will include a pgtIou string in the XML response. This pgtIou represents a proxy-granting ticket IOU. The CAS server will then create its own HTTPS connection back to the pgtUrl . This is to mutually authenticate the CAS server and the claimed service URL. The HTTPS connection will be used to send a proxy granting ticket to the original web application. For example, https://server3.company.com/webapp/login/cas/proxyreceptor?pgtIou=PGTIOU-0-R0zlgrl4pdAQwBvJWO3vnNpevwqStbSGcq3vKB2SqSFFRnjPHt&pgtId=PGT-1-si9YkkHLrtACBo64rmsi3v2nf7cpCResXg5MpESZFArbaZiOKH.

  • The Cas20TicketValidator will parse the XML received from the CAS server. It will return to the CasAuthenticationProvider a TicketResponse , which includes the username (mandatory), proxy list (if any were involved), and proxy-granting ticket IOU (if the proxy callback was requested).

  • Next CasAuthenticationProvider will call a configured CasProxyDecider . The CasProxyDecider indicates whether the proxy list in the TicketResponse is acceptable to the service. Several implementations are provided with Spring Security: RejectProxyTickets , AcceptAnyCasProxy and NamedCasProxyDecider . These names are largely self-explanatory, except NamedCasProxyDecider which allows a List of trusted proxies to be provided.

  • CasAuthenticationProvider will next request a AuthenticationUserDetailsService to load the GrantedAuthority objects that apply to the user contained in the Assertion .

  • If there were no problems, CasAuthenticationProvider constructs a CasAuthenticationToken including the details contained in the TicketResponse and the GrantedAuthority s.

  • Control then returns to CasAuthenticationFilter , which places the created CasAuthenticationToken in the security context.

  • The user’s browser is redirected to the original page that caused the AuthenticationException (or a custom destination depending on the configuration).

It’s good that you’re still here! Let’s now look at how this is configured

13.7.3 Configuration of CAS Client

The web application side of CAS is made easy due to Spring Security. It is assumed you already know the basics of using Spring Security, so these are not covered again below. We’ll assume a namespace based configuration is being used and add in the CAS beans as required. Each section builds upon the previous section. A fullCAS sample application can be found in the Spring Security Samples.

Service Ticket Authentication

This section describes how to setup Spring Security to authenticate Service Tickets. Often times this is all a web application requires. You will need to add a ServiceProperties bean to your application context. This represents your CAS service:

<bean id="serviceProperties"
    class="org.springframework.security.cas.ServiceProperties">
<property name="service"
    value="https://localhost:8443/cas-sample/login/cas"/>
<property name="sendRenew" value="false"/>
</bean>

The service must equal a URL that will be monitored by the CasAuthenticationFilter . The sendRenew defaults to false, but should be set to true if your application is particularly sensitive. What this parameter does is tell the CAS login service that a single sign on login is unacceptable. Instead, the user will need to re-enter their username and password in order to gain access to the service.

The following beans should be configured to commence the CAS authentication process (assuming you’re using a namespace configuration):

<security:http entry-point-ref="casEntryPoint">
...
<security:custom-filter position="CAS_FILTER" ref="casFilter" />
</security:http>

<bean id="casFilter"
    class="org.springframework.security.cas.web.CasAuthenticationFilter">
<property name="authenticationManager" ref="authenticationManager"/>
</bean>

<bean id="casEntryPoint"
    class="org.springframework.security.cas.web.CasAuthenticationEntryPoint">
<property name="loginUrl" value="https://localhost:9443/cas/login"/>
<property name="serviceProperties" ref="serviceProperties"/>
</bean>

For CAS to operate, the ExceptionTranslationFilter must have its authenticationEntryPoint property set to the CasAuthenticationEntryPoint bean. This can easily be done using entry-point-ref as is done in the example above. The CasAuthenticationEntryPoint must refer to the ServiceProperties bean (discussed above), which provides the URL to the enterprise’s CAS login server. This is where the user’s browser will be redirected.

The CasAuthenticationFilter has very similar properties to the UsernamePasswordAuthenticationFilter (used for form-based logins). You can use these properties to customize things like behavior for authentication success and failure.

Next you need to add a CasAuthenticationProvider and its collaborators:

<security:authentication-manager alias="authenticationManager">
<security:authentication-provider ref="casAuthenticationProvider" />
</security:authentication-manager>

<bean id="casAuthenticationProvider"
    class="org.springframework.security.cas.authentication.CasAuthenticationProvider">
<property name="authenticationUserDetailsService">
    <bean class="org.springframework.security.core.userdetails.UserDetailsByNameServiceWrapper">
    <constructor-arg ref="userService" />
    </bean>
</property>
<property name="serviceProperties" ref="serviceProperties" />
<property name="ticketValidator">
    <bean class="org.jasig.cas.client.validation.Cas20ServiceTicketValidator">
    <constructor-arg index="0" value="https://localhost:9443/cas" />
    </bean>
</property>
<property name="key" value="an_id_for_this_auth_provider_only"/>
</bean>

<security:user-service id="userService">
<!-- Password is prefixed with {noop} to indicate to DelegatingPasswordEncoder that
NoOpPasswordEncoder should be used.
This is not safe for production, but makes reading
in samples easier.
Normally passwords should be hashed using BCrypt -->
<security:user name="joe" password="{noop}joe" authorities="ROLE_USER" />
...
</security:user-service>

The CasAuthenticationProvider uses a UserDetailsService instance to load the authorities for a user, once they have been authenticated by CAS. We’ve shown a simple in-memory setup here. Note that the CasAuthenticationProvider does not actually use the password for authentication, but it does use the authorities.

The beans are all reasonably self-explanatory if you refer back to the How CAS Works section.

This completes the most basic configuration for CAS. If you haven’t made any mistakes, your web application should happily work within the framework of CAS single sign on. No other parts of Spring Security need to be concerned about the fact CAS handled authentication. In the following sections we will discuss some (optional) more advanced configurations.

Single Logout

The CAS protocol supports Single Logout and can be easily added to your Spring Security configuration. Below are updates to the Spring Security configuration that handle Single Logout

<security:http entry-point-ref="casEntryPoint">
...
<security:logout logout-success-url="/cas-logout.jsp"/>
<security:custom-filter ref="requestSingleLogoutFilter" before="LOGOUT_FILTER"/>
<security:custom-filter ref="singleLogoutFilter" before="CAS_FILTER"/>
</security:http>

<!-- This filter handles a Single Logout Request from the CAS Server -->
<bean id="singleLogoutFilter" class="org.jasig.cas.client.session.SingleSignOutFilter"/>

<!-- This filter redirects to the CAS Server to signal Single Logout should be performed -->
<bean id="requestSingleLogoutFilter"
    class="org.springframework.security.web.authentication.logout.LogoutFilter">
<constructor-arg value="https://localhost:9443/cas/logout"/>
<constructor-arg>
    <bean class=
        "org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler"/>
</constructor-arg>
<property name="filterProcessesUrl" value="/logout/cas"/>
</bean>

The logout element logs the user out of the local application, but does not terminate the session with the CAS server or any other applications that have been logged into. The requestSingleLogoutFilter filter will allow the URL of /spring_security_cas_logout to be requested to redirect the application to the configured CAS Server logout URL. Then the CAS Server will send a Single Logout request to all the services that were signed into. The singleLogoutFilter handles the Single Logout request by looking up the HttpSession in a static Map and then invalidating it.

It might be confusing why both the logout element and the singleLogoutFilter are needed. It is considered best practice to logout locally first since the SingleSignOutFilter just stores the HttpSession in a static Map in order to call invalidate on it. With the configuration above, the flow of logout would be:

  • The user requests /logout which would log the user out of the local application and send the user to the logout success page.

  • The logout success page, /cas-logout.jsp , should instruct the user to click a link pointing to /logout/cas in order to logout out of all applications.

  • When the user clicks the link, the user is redirected to the CAS single logout URL (https://localhost:9443/cas/logout).

  • On the CAS Server side, the CAS single logout URL then submits single logout requests to all the CAS Services. On the CAS Service side, JASIG’s SingleSignOutFilter processes the logout request by invaliditing the original session.

The next step is to add the following to your web.xml

<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>
    org.springframework.web.filter.CharacterEncodingFilter
</filter-class>
<init-param>
    <param-name>encoding</param-name>
    <param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<listener>
<listener-class>
    org.jasig.cas.client.session.SingleSignOutHttpSessionListener
</listener-class>
</listener>

When using the SingleSignOutFilter you might encounter some encoding issues. Therefore it is recommended to add the CharacterEncodingFilter to ensure that the character encoding is correct when using the SingleSignOutFilter . Again, refer to JASIG’s documentation for details. The SingleSignOutHttpSessionListener ensures that when an HttpSession expires, the mapping used for single logout is removed.

Authenticating to a Stateless Service with CAS

This section describes how to authenticate to a service using CAS. In other words, this section discusses how to setup a client that uses a service that authenticates with CAS. The next section describes how to setup a stateless service to Authenticate using CAS.

Configuring CAS to Obtain Proxy Granting Tickets

In order to authenticate to a stateless service, the application needs to obtain a proxy granting ticket (PGT). This section describes how to configure Spring Security to obtain a PGT building upon thencas-st[Service Ticket Authentication] configuration.

The first step is to include a ProxyGrantingTicketStorage in your Spring Security configuration. This is used to store PGT’s that are obtained by the CasAuthenticationFilter so that they can be used to obtain proxy tickets. An example configuration is shown below

<!--
NOTE: In a real application you should not use an in memory implementation.
You will also want to ensure to clean up expired tickets by calling
ProxyGrantingTicketStorage.cleanup()
-->
<bean id="pgtStorage" class="org.jasig.cas.client.proxy.ProxyGrantingTicketStorageImpl"/>

The next step is to update the CasAuthenticationProvider to be able to obtain proxy tickets. To do this replace the Cas20ServiceTicketValidator with a Cas20ProxyTicketValidator . The proxyCallbackUrl should be set to a URL that the application will receive PGT’s at. Last, the configuration should also reference the ProxyGrantingTicketStorage so it can use a PGT to obtain proxy tickets. You can find an example of the configuration changes that should be made below.

<bean id="casAuthenticationProvider"
    class="org.springframework.security.cas.authentication.CasAuthenticationProvider">
...
<property name="ticketValidator">
    <bean class="org.jasig.cas.client.validation.Cas20ProxyTicketValidator">
    <constructor-arg value="https://localhost:9443/cas"/>
        <property name="proxyCallbackUrl"
        value="https://localhost:8443/cas-sample/login/cas/proxyreceptor"/>
    <property name="proxyGrantingTicketStorage" ref="pgtStorage"/>
    </bean>
</property>
</bean>

The last step is to update the CasAuthenticationFilter to accept PGT and to store them in the ProxyGrantingTicketStorage . It is important the proxyReceptorUrl matches the proxyCallbackUrl of the Cas20ProxyTicketValidator . An example configuration is shown below.

<bean id="casFilter"
        class="org.springframework.security.cas.web.CasAuthenticationFilter">
    ...
    <property name="proxyGrantingTicketStorage" ref="pgtStorage"/>
    <property name="proxyReceptorUrl" value="/login/cas/proxyreceptor"/>
</bean>
Calling a Stateless Service Using a Proxy Ticket

Now that Spring Security obtains PGTs, you can use them to create proxy tickets which can be used to authenticate to a stateless service. The CAS sample application contains a working example in the ProxyTicketSampleServlet . Example code can be found below:

protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
// NOTE: The CasAuthenticationToken can also be obtained using
// SecurityContextHolder.getContext().getAuthentication()
final CasAuthenticationToken token = (CasAuthenticationToken) request.getUserPrincipal();
// proxyTicket could be reused to make calls to the CAS service even if the
// target url differs
final String proxyTicket = token.getAssertion().getPrincipal().getProxyTicketFor(targetUrl);

// Make a remote call using the proxy ticket
final String serviceUrl = targetUrl+"?ticket="+URLEncoder.encode(proxyTicket, "UTF-8");
String proxyResponse = CommonUtils.getResponseFromServer(serviceUrl, "UTF-8");
...
}

Proxy Ticket Authentication

The CasAuthenticationProvider distinguishes between stateful and stateless clients. A stateful client is considered any that submits to the filterProcessUrl of the CasAuthenticationFilter . A stateless client is any that presents an authentication request to CasAuthenticationFilter on a URL other than the filterProcessUrl .

Because remoting protocols have no way of presenting themselves within the context of an HttpSession , it isn’t possible to rely on the default practice of storing the security context in the session between requests. Furthermore, because the CAS server invalidates a ticket after it has been validated by the TicketValidator , presenting the same proxy ticket on subsequent requests will not work.

One obvious option is to not use CAS at all for remoting protocol clients. However, this would eliminate many of the desirable features of CAS. As a middle-ground, the CasAuthenticationProvider uses a StatelessTicketCache . This is used solely for stateless clients which use a principal equal to CasAuthenticationFilter.CAS_STATELESS_IDENTIFIER . What happens is the CasAuthenticationProvider will store the resulting CasAuthenticationToken in the StatelessTicketCache , keyed on the proxy ticket. Accordingly, remoting protocol clients can present the same proxy ticket and the CasAuthenticationProvider will not need to contact the CAS server for validation (aside from the first request). Once authenticated, the proxy ticket could be used for URLs other than the original target service.

This section builds upon the previous sections to accommodate proxy ticket authentication. The first step is to specify to authenticate all artifacts as shown below.

<bean id="serviceProperties"
    class="org.springframework.security.cas.ServiceProperties">
...
<property name="authenticateAllArtifacts" value="true"/>
</bean>

The next step is to specify serviceProperties and the authenticationDetailsSource for the CasAuthenticationFilter . The serviceProperties property instructs the CasAuthenticationFilter to attempt to authenticate all artifacts instead of only ones present on the filterProcessUrl . The ServiceAuthenticationDetailsSource creates a ServiceAuthenticationDetails that ensures the current URL, based upon the HttpServletRequest , is used as the service URL when validating the ticket. The method for generating the service URL can be customized by injecting a custom AuthenticationDetailsSource that returns a custom ServiceAuthenticationDetails .

<bean id="casFilter"
    class="org.springframework.security.cas.web.CasAuthenticationFilter">
...
<property name="serviceProperties" ref="serviceProperties"/>
<property name="authenticationDetailsSource">
    <bean class=
    "org.springframework.security.cas.web.authentication.ServiceAuthenticationDetailsSource">
    <constructor-arg ref="serviceProperties"/>
    </bean>
</property>
</bean>

You will also need to update the CasAuthenticationProvider to handle proxy tickets. To do this replace the Cas20ServiceTicketValidator with a Cas20ProxyTicketValidator . You will need to configure the statelessTicketCache and which proxies you want to accept. You can find an example of the updates required to accept all proxies below.

<bean id="casAuthenticationProvider"
    class="org.springframework.security.cas.authentication.CasAuthenticationProvider">
...
<property name="ticketValidator">
    <bean class="org.jasig.cas.client.validation.Cas20ProxyTicketValidator">
    <constructor-arg value="https://localhost:9443/cas"/>
    <property name="acceptAnyProxy" value="true"/>
    </bean>
</property>
<property name="statelessTicketCache">
    <bean class="org.springframework.security.cas.authentication.EhCacheBasedTicketCache">
    <property name="cache">
        <bean class="net.sf.ehcache.Cache"
            init-method="initialise" destroy-method="dispose">
        <constructor-arg value="casTickets"/>
        <constructor-arg value="50"/>
        <constructor-arg value="true"/>
        <constructor-arg value="false"/>
        <constructor-arg value="3600"/>
        <constructor-arg value="900"/>
        </bean>
    </property>
    </bean>
</property>
</bean>

13.8 X.509 Authentication

13.8.1 Overview

The most common use of X.509 certificate authentication is in verifying the identity of a server when using SSL, most commonly when using HTTPS from a browser. The browser will automatically check that the certificate presented by a server has been issued (ie digitally signed) by one of a list of trusted certificate authorities which it maintains.

You can also use SSL with "mutual authentication"; the server will then request a valid certificate from the client as part of the SSL handshake. The server will authenticate the client by checking that its certificate is signed by an acceptable authority. If a valid certificate has been provided, it can be obtained through the servlet API in an application. Spring Security X.509 module extracts the certificate using a filter. It maps the certificate to an application user and loads that user’s set of granted authorities for use with the standard Spring Security infrastructure.

You should be familiar with using certificates and setting up client authentication for your servlet container before attempting to use it with Spring Security. Most of the work is in creating and installing suitable certificates and keys. For example, if you’re using Tomcat then read the instructions here http://tomcat.apache.org/tomcat-6.0-doc/ssl-howto.html. It’s important that you get this working before trying it out with Spring Security

13.8.2 Adding X.509 Authentication to Your Web Application

Enabling X.509 client authentication is very straightforward. Just add the <x509/> element to your http security namespace configuration.

<http>
...
    <x509 subject-principal-regex="CN=(.*?)," user-service-ref="userService"/>;
</http>

The element has two optional attributes:

  • subject-principal-regex . The regular expression used to extract a username from the certificate’s subject name. The default value is shown above. This is the username which will be passed to the UserDetailsService to load the authorities for the user.

  • user-service-ref . This is the bean Id of the UserDetailsService to be used with X.509. It isn’t needed if there is only one defined in your application context.

The subject-principal-regex should contain a single group. For example the default expression "CN=(.*?)," matches the common name field. So if the subject name in the certificate is "CN=Jimi Hendrix, OU=…", this will give a user name of "Jimi Hendrix". The matches are case insensitive. So "emailAddress=(.?)," will match "EMAILADDRESS=[email protected],CN=…" giving a user name "[email protected]". If the client presents a certificate and a valid username is successfully extracted, then there should be a valid Authentication object in the security context. If no certificate is found, or no corresponding user could be found then the security context will remain empty. This means that you can easily use X.509 authentication with other options such as a form-based login.

13.8.3 Setting up SSL in Tomcat

There are some pre-generated certificates in the samples/certificate directory in the Spring Security project. You can use these to enable SSL for testing if you don’t want to generate your own. The file server.jks contains the server certificate, private key and the issuing certificate authority certificate. There are also some client certificate files for the users from the sample applications. You can install these in your browser to enable SSL client authentication.

To run tomcat with SSL support, drop the server.jks file into the tomcat conf directory and add the following connector to the server.xml file

<Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true" scheme="https" secure="true"
            clientAuth="true" sslProtocol="TLS"
            keystoreFile="${catalina.home}/conf/server.jks"
            keystoreType="JKS" keystorePass="password"
            truststoreFile="${catalina.home}/conf/server.jks"
            truststoreType="JKS" truststorePass="password"
/>

clientAuth can also be set to want if you still want SSL connections to succeed even if the client doesn’t provide a certificate. Clients which don’t present a certificate won’t be able to access any objects secured by Spring Security unless you use a non-X.509 authentication mechanism, such as form authentication.

13.9 Run-As Authentication Replacement

13.9.1 Overview

The AbstractSecurityInterceptor is able to temporarily replace the Authentication object in the SecurityContext and SecurityContextHolder during the secure object callback phase. This only occurs if the original Authentication object was successfully processed by the AuthenticationManager and AccessDecisionManager . The RunAsManager will indicate the replacement Authentication object, if any, that should be used during the SecurityInterceptorCallback .

By temporarily replacing the Authentication object during the secure object callback phase, the secured invocation will be able to call other objects which require different authentication and authorization credentials. It will also be able to perform any internal security checks for specific GrantedAuthority objects. Because Spring Security provides a number of helper classes that automatically configure remoting protocols based on the contents of the SecurityContextHolder , these run-as replacements are particularly useful when calling remote web services

13.9.2 Configuration

A RunAsManager interface is provided by Spring Security:

Authentication buildRunAs(Authentication authentication, Object object,
    List<ConfigAttribute> config);

boolean supports(ConfigAttribute attribute);

boolean supports(Class clazz);

The first method returns the Authentication object that should replace the existing Authentication object for the duration of the method invocation. If the method returns null , it indicates no replacement should be made. The second method is used by the AbstractSecurityInterceptor as part of its startup validation of configuration attributes. The supports(Class) method is called by a security interceptor implementation to ensure the configured RunAsManager supports the type of secure object that the security interceptor will present.

One concrete implementation of a RunAsManager is provided with Spring Security. The RunAsManagerImpl class returns a replacement RunAsUserToken if any ConfigAttribute starts with RUN_AS_ . If any such ConfigAttribute is found, the replacement RunAsUserToken will contain the same principal, credentials and granted authorities as the original Authentication object, along with a new SimpleGrantedAuthority for each RUN_AS_ ConfigAttribute . Each new SimpleGrantedAuthority will be prefixed with ROLE_ , followed by the RUN_AS ConfigAttribute . For example, a RUN_AS_SERVER will result in the replacement RunAsUserToken containing a ROLE_RUN_AS_SERVER granted authority.

The replacement RunAsUserToken is just like any other Authentication object. It needs to be authenticated by the AuthenticationManager , probably via delegation to a suitable AuthenticationProvider . The RunAsImplAuthenticationProvider performs such authentication. It simply accepts as valid any RunAsUserToken presented.

To ensure malicious code does not create a RunAsUserToken and present it for guaranteed acceptance by the RunAsImplAuthenticationProvider , the hash of a key is stored in all generated tokens. The RunAsManagerImpl and RunAsImplAuthenticationProvider is created in the bean context with the same key:

<bean id="runAsManager"
    class="org.springframework.security.access.intercept.RunAsManagerImpl">
<property name="key" value="my_run_as_password"/>
</bean>

<bean id="runAsAuthenticationProvider"
    class="org.springframework.security.access.intercept.RunAsImplAuthenticationProvider">
<property name="key" value="my_run_as_password"/>
</bean>

By using the same key, each RunAsUserToken can be validated it was created by an approved RunAsManagerImpl . The RunAsUserToken is immutable after creation for security reasons

13.10 Spring Security Crypto Module

13.10.1 Introduction

The Spring Security Crypto module provides support for symmetric encryption, key generation, and password encoding. The code is distributed as part of the core module but has no dependencies on any other Spring Security (or Spring) code.

13.10.2 Encryptors

The Encryptors class provides factory methods for constructing symmetric encryptors. Using this class, you can create ByteEncryptors to encrypt data in raw byte[] form. You can also construct TextEncryptors to encrypt text strings. Encryptors are thread-safe.

BytesEncryptor

Use the Encryptors.standard factory method to construct a "standard" BytesEncryptor:

Encryptors.standard("password", "salt");

The "standard" encryption method is 256-bit AES using PKCS #5’s PBKDF2 (Password-Based Key Derivation Function #2). This method requires Java 6. The password used to generate the SecretKey should be kept in a secure place and not be shared. The salt is used to prevent dictionary attacks against the key in the event your encrypted data is compromised. A 16-byte random initialization vector is also applied so each encrypted message is unique.

The provided salt should be in hex-encoded String form, be random, and be at least 8 bytes in length. Such a salt may be generated using a KeyGenerator:

String salt = KeyGenerators.string().generateKey(); // generates a random 8-byte salt that is then hex-encoded

TextEncryptor

Use the Encryptors.text factory method to construct a standard TextEncryptor:

Encryptors.text("password", "salt");

A TextEncryptor uses a standard BytesEncryptor to encrypt text data. Encrypted results are returned as hex-encoded strings for easy storage on the filesystem or in the database.

Use the Encryptors.queryableText factory method to construct a "queryable" TextEncryptor:

Encryptors.queryableText("password", "salt");

The difference between a queryable TextEncryptor and a standard TextEncryptor has to do with initialization vector (iv) handling. The iv used in a queryable TextEncryptor#encrypt operation is shared, or constant, and is not randomly generated. This means the same text encrypted multiple times will always produce the same encryption result. This is less secure, but necessary for encrypted data that needs to be queried against. An example of queryable encrypted text would be an OAuth apiKey.

13.10.3 Key Generators

The KeyGenerators class provides a number of convenience factory methods for constructing different types of key generators. Using this class, you can create a BytesKeyGenerator to generate byte[] keys. You can also construct a StringKeyGenerator to generate string keys. KeyGenerators are thread-safe.

BytesKeyGenerator

Use the KeyGenerators.secureRandom factory methods to generate a BytesKeyGenerator backed by a SecureRandom instance:

BytesKeyGenerator generator = KeyGenerators.secureRandom();
byte[] key = generator.generateKey();

The default key length is 8 bytes. There is also a KeyGenerators.secureRandom variant that provides control over the key length:

KeyGenerators.secureRandom(16);

Use the KeyGenerators.shared factory method to construct a BytesKeyGenerator that always returns the same key on every invocation:

KeyGenerators.shared(16);

StringKeyGenerator

Use the KeyGenerators.string factory method to construct a 8-byte, SecureRandom KeyGenerator that hex-encodes each key as a String:

KeyGenerators.string();

13.10.4 Password Encoding

The password package of the spring-security-crypto module provides support for encoding passwords. PasswordEncoder is the central service interface and has the following signature:

public interface PasswordEncoder {

String encode(String rawPassword);

boolean matches(String rawPassword, String encodedPassword);
}

The matches method returns true if the rawPassword, once encoded, equals the encodedPassword. This method is designed to support password-based authentication schemes.

The BCryptPasswordEncoder implementation uses the widely supported "bcrypt" algorithm to hash the passwords. Bcrypt uses a random 16 byte salt value and is a deliberately slow algorithm, in order to hinder password crackers. The amount of work it does can be tuned using the "strength" parameter which takes values from 4 to 31. The higher the value, the more work has to be done to calculate the hash. The default value is 10. You can change this value in your deployed system without affecting existing passwords, as the value is also stored in the encoded hash.

// Create an encoder with strength 16
BCryptPasswordEncoder encoder = new BCryptPasswordEncoder(16);
String result = encoder.encode("myPassword");
assertTrue(encoder.matches("myPassword", result));

The Pbkdf2PasswordEncoder implementation uses PBKDF2 algorithm to hash the passwords. In order to defeat password cracking PBKDF2 is a deliberately slow algorithm and should be tuned to take about .5 seconds to verify a password on your system.

// Create an encoder with all the defaults
Pbkdf2PasswordEncoder encoder = new Pbkdf2PasswordEncoder();
String result = encoder.encode("myPassword");
assertTrue(encoder.matches("myPassword", result));

13.11 Concurrency Support

In most environments, Security is stored on a per Thread basis. This means that when work is done on a new Thread , the SecurityContext is lost. Spring Security provides some infrastructure to help make this much easier for users. Spring Security provides low level abstractions for working with Spring Security in multi-threaded environments. In fact, this is what Spring Security builds on to integration with the section called “AsyncContext.start(Runnable)” and Section 13.12.4, “Spring MVC Async Integration”.

13.11.1 DelegatingSecurityContextRunnable

One of the most fundamental building blocks within Spring Security’s concurrency support is the DelegatingSecurityContextRunnable . It wraps a delegate Runnable in order to initialize the SecurityContextHolder with a specified SecurityContext for the delegate. It then invokes the delegate Runnable ensuring to clear the SecurityContextHolder afterwards. The DelegatingSecurityContextRunnable looks something like this:

public void run() {
try {
    SecurityContextHolder.setContext(securityContext);
    delegate.run();
} finally {
    SecurityContextHolder.clearContext();
}
}

While very simple, it makes it seamless to transfer the SecurityContext from one Thread to another. This is important since, in most cases, the SecurityContextHolder acts on a per Thread basis. For example, you might have used Spring Security’s the section called “<global-method-security>” support to secure one of your services. You can now easily transfer the SecurityContext of the current Thread to the Thread that invokes the secured service. An example of how you might do this can be found below:

Runnable originalRunnable = new Runnable() {
public void run() {
    // invoke secured service
}
};

SecurityContext context = SecurityContextHolder.getContext();
DelegatingSecurityContextRunnable wrappedRunnable =
    new DelegatingSecurityContextRunnable(originalRunnable, context);

new Thread(wrappedRunnable).start();

The code above performs the following steps:

  • Creates a Runnable that will be invoking our secured service. Notice that it is not aware of Spring Security

  • Obtains the SecurityContext that we wish to use from the SecurityContextHolder and initializes the DelegatingSecurityContextRunnable

  • Use the DelegatingSecurityContextRunnable to create a Thread

  • Start the Thread we created

Since it is quite common to create a DelegatingSecurityContextRunnable with the SecurityContext from the SecurityContextHolder there is a shortcut constructor for it. The following code is the same as the code above:

Runnable originalRunnable = new Runnable() {
public void run() {
    // invoke secured service
}
};

DelegatingSecurityContextRunnable wrappedRunnable =
    new DelegatingSecurityContextRunnable(originalRunnable);

new Thread(wrappedRunnable).start();

The code we have is simple to use, but it still requires knowledge that we are using Spring Security. In the next section we will take a look at how we can utilize DelegatingSecurityContextExecutor to hide the fact that we are using Spring Security.

13.11.2 DelegatingSecurityContextExecutor

In the previous section we found that it was easy to use the DelegatingSecurityContextRunnable , but it was not ideal since we had to be aware of Spring Security in order to use it. Let’s take a look at how DelegatingSecurityContextExecutor can shield our code from any knowledge that we are using Spring Security.

The design of DelegatingSecurityContextExecutor is very similar to that of DelegatingSecurityContextRunnable except it accepts a delegate Executor instead of a delegate Runnable . You can see an example of how it might be used below:

SecurityContext context = SecurityContextHolder.createEmptyContext();
Authentication authentication =
    new UsernamePasswordAuthenticationToken("user","doesnotmatter", AuthorityUtils.createAuthorityList("ROLE_USER"));
context.setAuthentication(authentication);

SimpleAsyncTaskExecutor delegateExecutor =
    new SimpleAsyncTaskExecutor();
DelegatingSecurityContextExecutor executor =
    new DelegatingSecurityContextExecutor(delegateExecutor, context);

Runnable originalRunnable = new Runnable() {
public void run() {
    // invoke secured service
}
};

executor.execute(originalRunnable);

The code performs the following steps:

  • Creates the SecurityContext to be used for our DelegatingSecurityContextExecutor . Note that in this example we simply create the SecurityContext by hand. However, it does not matter where or how we get the SecurityContext (i.e. we could obtain it from the SecurityContextHolder if we wanted).

  • Creates a delegateExecutor that is in charge of executing submitted Runnable s

  • Finally we create a DelegatingSecurityContextExecutor which is in charge of wrapping any Runnable that is passed into the execute method with a DelegatingSecurityContextRunnable . It then passes the wrapped Runnable to the delegateExecutor. In this instance, the same SecurityContext will be used for every Runnable submitted to our DelegatingSecurityContextExecutor . This is nice if we are running background tasks that need to be run by a user with elevated privileges.

  • At this point you may be asking yourself "How does this shield my code of any knowledge of Spring Security?" Instead of creating the SecurityContext and the DelegatingSecurityContextExecutor in our own code, we can inject an already initialized instance of DelegatingSecurityContextExecutor .

@Autowired
private Executor executor; // becomes an instance of our DelegatingSecurityContextExecutor

public void submitRunnable() {
Runnable originalRunnable = new Runnable() {
    public void run() {
    // invoke secured service
    }
};
executor.execute(originalRunnable);
}

Now our code is unaware that the SecurityContext is being propagated to the Thread , then the originalRunnable is executed, and then the SecurityContextHolder is cleared out. In this example, the same user is being used to execute each Thread. What if we wanted to use the user from SecurityContextHolder at the time we invoked executor.execute(Runnable) (i.e. the currently logged in user) to process originalRunnable ? This can be done by removing the SecurityContext argument from our DelegatingSecurityContextExecutor constructor. For example:

SimpleAsyncTaskExecutor delegateExecutor = new SimpleAsyncTaskExecutor();
DelegatingSecurityContextExecutor executor =
    new DelegatingSecurityContextExecutor(delegateExecutor);

Now anytime executor.execute(Runnable) is executed the SecurityContext is first obtained by the SecurityContextHolder and then that SecurityContext is used to create our DelegatingSecurityContextRunnable . This means that we are executing our Runnable with the same user that was used to invoke the executor.execute(Runnable) code.

13.11.3 Spring Security Concurrency Classes

Refer to the Javadoc for additional integrations with both the Java concurrent APIs and the Spring Task abstractions. They are quite self-explanatory once you understand the previous code.

  • DelegatingSecurityContextCallable

  • DelegatingSecurityContextExecutor

  • DelegatingSecurityContextExecutorService

  • DelegatingSecurityContextRunnable

  • DelegatingSecurityContextScheduledExecutorService

  • DelegatingSecurityContextSchedulingTaskExecutor

  • DelegatingSecurityContextAsyncTaskExecutor

  • DelegatingSecurityContextTaskExecutor

13.12 Spring MVC Integration

Spring Security provides a number of optional integrations with Spring MVC. This section covers the integration in further detail.

13.12.1 @EnableWebMvcSecurity

Note

As of Spring Security 4.0, @EnableWebMvcSecurity is deprecated. The replacement is @EnableWebSecurity which will determine adding the Spring MVC features based upon the classpath.

To enable Spring Security integration with Spring MVC add the @EnableWebSecurity annotation to your configuration.

Note

Spring Security provides the configuration using Spring MVC’s WebMvcConfigurer. This means that if you are using more advanced options, like integrating with WebMvcConfigurationSupport directly, then you will need to manually provide the Spring Security configuration.

13.12.2 MvcRequestMatcher

Spring Security provides deep integration with how Spring MVC matches on URLs with MvcRequestMatcher . This is helpful to ensure your Security rules match the logic used to handle your requests.

In order to use MvcRequestMatcher you must place the Spring Security Configuration in the same ApplicationContext as your DispatcherServlet . This is necessary because Spring Security’s MvcRequestMatcher expects a HandlerMappingIntrospector bean with the name of mvcHandlerMappingIntrospector to be registered by your Spring MVC configuration that is used to perform the matching.

For a web.xml this means that you should place your configuration in the DispatcherServlet.xml .

<listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<!-- All Spring Configuration (both MVC and Security) are in /WEB-INF/spring/ -->
<context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>/WEB-INF/spring/*.xml</param-value>
</context-param>

<servlet>
  <servlet-name>spring</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <!-- Load from the ContextLoaderListener -->
  <init-param>
    <param-name>contextConfigLocation</param-name>
    <param-value></param-value>
  </init-param>
</servlet>

<servlet-mapping>
  <servlet-name>spring</servlet-name>
  <url-pattern>/</url-pattern>
</servlet-mapping>

Below WebSecurityConfiguration in placed in the DispatcherServlet s ApplicationContext .

public class SecurityInitializer extends
    AbstractAnnotationConfigDispatcherServletInitializer {

  @Override
  protected Class<?>[] getRootConfigClasses() {
    return null;
  }

  @Override
  protected Class<?>[] getServletConfigClasses() {
    return new Class[] { RootConfiguration.class,
        WebMvcConfiguration.class };
  }

  @Override
  protected String[] getServletMappings() {
    return new String[] { "/" };
  }
}

Note

It is always recommended to provide authorization rules by matching on the HttpServletRequest and method security.

Providing authorization rules by matching on HttpServletRequest is good because it happens very early in the code path and helps reduce the attack surface. Method security ensures that if someone has bypassed the web authorization rules, that your application is still secured. This is what is known as Defence in Depth

Consider a controller that is mapped as follows:

@RequestMapping("/admin")
public String admin() {

If we wanted to restrict access to this controller method to admin users, a developer can provide authorization rules by matching on the HttpServletRequest with the following:

protected configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
            .antMatchers("/admin").hasRole("ADMIN");
}

or in XML

<http>
    <intercept-url pattern="/admin" access="hasRole('ADMIN')"/>
</http>

With either configuration, the URL /admin will require the authenticated user to be an admin user. However, depending on our Spring MVC configuration, the URL /admin.html will also map to our admin() method. Additionally, depending on our Spring MVC configuration, the URL /admin/ will also map to our admin() method.

The problem is that our security rule is only protecting /admin . We could add additional rules for all the permutations of Spring MVC, but this would be quite verbose and tedious.

Instead, we can leverage Spring Security’s MvcRequestMatcher . The following configuration will protect the same URLs that Spring MVC will match on by using Spring MVC to match on the URL.

protected configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
            .mvcMatchers("/admin").hasRole("ADMIN");
}

or in XML

<http request-matcher="mvc">
    <intercept-url pattern="/admin" access="hasRole('ADMIN')"/>
</http>

13.12.3 @AuthenticationPrincipal

Spring Security provides AuthenticationPrincipalArgumentResolver which can automatically resolve the current Authentication.getPrincipal() for Spring MVC arguments. By using @EnableWebSecurity you will automatically have this added to your Spring MVC configuration. If you use XML based configuration, you must add this yourself. For example:

<mvc:annotation-driven>
        <mvc:argument-resolvers>
                <bean class="org.springframework.security.web.method.annotation.AuthenticationPrincipalArgumentResolver" />
        </mvc:argument-resolvers>
</mvc:annotation-driven>

Once AuthenticationPrincipalArgumentResolver is properly configured, you can be entirely decoupled from Spring Security in your Spring MVC layer.

Consider a situation where a custom UserDetailsService that returns an Object that implements UserDetails and your own CustomUser Object . The CustomUser of the currently authenticated user could be accessed using the following code:

@RequestMapping("/messages/inbox")
public ModelAndView findMessagesForUser() {
    Authentication authentication =
    SecurityContextHolder.getContext().getAuthentication();
    CustomUser custom = (CustomUser) authentication == null ? null : authentication.getPrincipal();

    // .. find messages for this user and return them ...
}

As of Spring Security 3.2 we can resolve the argument more directly by adding an annotation. For example:

import org.springframework.security.core.annotation.AuthenticationPrincipal;

// ...

@RequestMapping("/messages/inbox")
public ModelAndView findMessagesForUser(@AuthenticationPrincipal CustomUser customUser) {

    // .. find messages for this user and return them ...
}

Sometimes it may be necessary to transform the principal in some way. For example, if CustomUser needed to be final it could not be extended. In this situation the UserDetailsService might returns an Object that implements UserDetails and provides a method named getCustomUser to access CustomUser . For example, it might look like:

public class CustomUserUserDetails extends User {
        // ...
        public CustomUser getCustomUser() {
                return customUser;
        }
}

We could then access the CustomUser using a SpEL expression that uses Authentication.getPrincipal() as the root object:

import org.springframework.security.core.annotation.AuthenticationPrincipal;

// ...

@RequestMapping("/messages/inbox")
public ModelAndView findMessagesForUser(@AuthenticationPrincipal(expression = "customUser") CustomUser customUser) {

    // .. find messags for this user and return them ...
}

We can also refer to Beans in our SpEL expressions. For example, the following could be used if we were using JPA to manage our Users and we wanted to modify and save a property on the current user.

import org.springframework.security.core.annotation.AuthenticationPrincipal;

// ...

@PutMapping("/users/self")
public ModelAndView updateName(@AuthenticationPrincipal(expression = "@jpaEntityManager.merge(#this)") CustomUser attachedCustomUser,
        @RequestParam String firstName) {

    // change the firstName on an attached instance which will be persisted to the database
    attachedCustomUser.setFirstName(firstName);

    // ...
}

We can further remove our dependency on Spring Security by making @AuthenticationPrincipal a meta annotation on our own annotation. Below we demonstrate how we could do this on an annotation named @CurrentUser .

Note

It is important to realize that in order to remove the dependency on Spring Security, it is the consuming application that would create @CurrentUser . This step is not strictly required, but assists in isolating your dependency to Spring Security to a more central location.

@Target({ElementType.PARAMETER, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@AuthenticationPrincipal
public @interface CurrentUser {}

Now that @CurrentUser has been specified, we can use it to signal to resolve our CustomUser of the currently authenticated user. We have also isolated our dependency on Spring Security to a single file.

@RequestMapping("/messages/inbox")
public ModelAndView findMessagesForUser(@CurrentUser CustomUser customUser) {

    // .. find messages for this user and return them ...
}

13.12.4 Spring MVC Async Integration

Spring Web MVC 3.2+ has excellent support for Asynchronous Request Processing. With no additional configuration, Spring Security will automatically setup the SecurityContext to the Thread that executes a Callable returned by your controllers. For example, the following method will automatically have its Callable executed with the SecurityContext that was available when the Callable was created:

@RequestMapping(method=RequestMethod.POST)
public Callable<String> processUpload(final MultipartFile file) {

return new Callable<String>() {
    public Object call() throws Exception {
    // ...
    return "someView";
    }
};
}

Note

More technically speaking, Spring Security integrates with WebAsyncManager . The SecurityContext that is used to process the Callable is the SecurityContext that exists on the SecurityContextHolder at the time startCallableProcessing is invoked.

There is no automatic integration with a DeferredResult that is returned by controllers. This is because DeferredResult is processed by the users and thus there is no way of automatically integrating with it. However, you can still use Concurrency Support to provide transparent integration with Spring Security.

13.12.5 Spring MVC and CSRF Integration

Automatic Token Inclusion

Spring Security will automatically include the CSRF Token within forms that use the Spring MVC form tag. For example, the following JSP:

<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page"
    xmlns:c="http://java.sun.com/jsp/jstl/core"
    xmlns:form="http://www.springframework.org/tags/form" version="2.0">
    <jsp:directive.page language="java" contentType="text/html" />
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
    <!-- ... -->

    <c:url var="logoutUrl" value="/logout"/>
    <form:form action="${logoutUrl}"
        method="post">
    <input type="submit"
        value="Log out" />
    <input type="hidden"
        name="${_csrf.parameterName}"
        value="${_csrf.token}"/>
    </form:form>

    <!-- ... -->
</html>
</jsp:root>

Will output HTML that is similar to the following:

<!-- ... -->

<form action="/context/logout" method="post">
<input type="submit" value="Log out"/>
<input type="hidden" name="_csrf" value="f81d4fae-7dec-11d0-a765-00a0c91e6bf6"/>
</form>

<!-- ... -->

Resolving the CsrfToken

Spring Security provides CsrfTokenArgumentResolver which can automatically resolve the current CsrfToken for Spring MVC arguments. By using @EnableWebSecurity you will automatically have this added to your Spring MVC configuration. If you use XML based configuraiton, you must add this yourself.

Once CsrfTokenArgumentResolver is properly configured, you can expose the CsrfToken to your static HTML based application.

@RestController
public class CsrfController {

    @RequestMapping("/csrf")
    public CsrfToken csrf(CsrfToken token) {
        return token;
    }
}

It is important to keep the CsrfToken a secret from other domains. This means if you are using Cross Origin Sharing (CORS), you should NOT expose the CsrfToken to any external domains.


[21]The legacy options from Spring Security 2.0 are also supported, but discouraged.