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" %>

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.

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.

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

	Caution
	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.

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:<br />
    <input type="text" name="name" />
    ...
</form>

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.

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.

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.

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.

<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>

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>

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.

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.

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.

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.

<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>

<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>

<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>

<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>

<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>

<!--
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"/>

<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>

<bean id="casFilter"
        class="org.springframework.security.cas.web.CasAuthenticationFilter">
    ...
    <property name="proxyGrantingTicketStorage" ref="pgtStorage"/>
    <property name="proxyReceptorUrl" value="/login/cas/proxyreceptor"/>
</bean>

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");
...
}

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

<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>

<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>

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

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:

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.

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.

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

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

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.

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.

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

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

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

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

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

KeyGenerators.secureRandom(16);

KeyGenerators.shared(16);

KeyGenerators.string();

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));

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:

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.

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:

@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.

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.

	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.

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 DispatcherServlets 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>

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 ...
}

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";
    }
};
}

	Associating SecurityContext to Callable’s
	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.