3、 CAS单点登录源码解析之【单点登出】

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前期准备

已经搭建好了集成了CAS客户端的应用系统和CAS服务器

1.应用系统webapp（http://127.0.0.1:8090/webapp/main.do）

2.CAS单点登录服务器端（http://127.0.0.1:8081/cas-server/）

本次讨论包括CAS单点登录客户端的部分源码，以及在此基础上进行单点登出二次开发，因此需要修改部分CAS客户端的源码，源码部分的修改在下面进行讨论。关于CAS客户端和服务器端的源码分析，请参考另外两篇文章

CAS客户端：/article/11163792.html

CAS服务器端：/article/11163793.html

应用系统web.xml部分代码

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<listener>

<listener-class>com.master.client.listener.SingleSignOutHttpSessionListener</listener-class>

</listener>

<filter>

<filter-name>CAS Single Sign Out Filter</filter-name>

<filter-class>com.master.client.filter.SingleSignOutFilter</filter-class>

</filter>

应用系统登出方法logout

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public String logout(HttpSession session, HttpServletResponse response,

HttpServletRequest request) {

try {

Properties conf = PropertiesUtil.getConfigProperties();

String service = ssoProperties.getProperty("service");

String logoutUrl = ssoProperties.getProperty("casServerLogoutUrl");

String serverName = ssoProperties.getProperty("serverName");

//生成CAS服务器端的登出URL

String serviceUrl = CommonUtils.constructServiceUrl(request, response, service, serverName, "ticket", true);

response.sendRedirect(logoutUrl + "?service=" + URLEncoder.encode(serviceUrl, "utf-8"));

} catch (URISyntaxException e) {

e.printStackTrace();

} catch (UnsupportedEncodingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

return null;

}

当我们在应用系统中，执行注销或退出操作时，会执行logout方法。应用系统登出方法logout要做是获取单点登录的配置文件（参考/article/11163792.html），获取service、logoutUrl和serverName参数。生成CAS服务器端的登出URL（http://127.0.0.1:8081/cas-server/logout?service=http://127.0.0.1:8090/webapp/main.do），response重定向到CAS服务器端的登出URL。

CAS服务器端cas-server.xml部分代码

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<bean id="handlerMappingC" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">

<property name="mappings">

<props>

<prop key="/logout">logoutController</prop><!-- 登出 -->

<prop key="/serviceValidate">serviceValidateController</prop>

<prop key="/validate">legacyValidateController</prop>

<prop key="/proxy">proxyController</prop>

<prop key="/proxyValidate">proxyValidateController</prop>

<prop key="/samlValidate">samlValidateController</prop>

<prop key="/services/add.html">addRegisteredServiceSimpleFormController</prop>

<prop key="/services/edit.html">editRegisteredServiceSimpleFormController</prop>

<prop key="/services/loggedOut.html">serviceLogoutViewController</prop>

<prop key="/services/viewStatistics.html">viewStatisticsController</prop>

<prop key="/services/*">manageRegisteredServicesMultiActionController</prop>

<prop key="/openid/*">openIdProviderController</prop>

<prop key="/authorizationFailure.html">passThroughController</prop>

<prop key="/403.html">passThroughController</prop>

<prop key="/status">healthCheckController</prop>

<prop key="/error">extErrorController</prop>

</props>

</property>

<property name="alwaysUseFullPath" value="true" />

</bean>

logoutController配置信息

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<bean id="logoutController" class="org.jasig.cas.web.LogoutController"

p:centralAuthenticationService-ref="centralAuthenticationService"

p:logoutView="casLogoutView" p:warnCookieGenerator-ref="warnCookieGenerator"

p:ticketGrantingTicketCookieGenerator-ref="ticketGrantingTicketCookieGenerator"

p:servicesManager-ref="servicesManager" p:followServiceRedirects="${cas.logout.followServiceRedirects:true}" />

根据配置信息，当CAS单点登录服务器端截获http://127.0.0.1:8081/cas-server/logout?service=http://127.0.0.1:8090/webapp/main.do链接时，会进入到LogoutController的handleRequestInternal方法。

LogoutController的handleRequestInternal方法

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protected ModelAndView handleRequestInternal(

final HttpServletRequest request, final HttpServletResponse response)

throws Exception {

//获取TGT

final String ticketGrantingTicketId = this.ticketGrantingTicketCookieGenerator.retrieveCookieValue(request);

//获取service

final String service = request.getParameter("service");

//如果TGT不为空

if (ticketGrantingTicketId != null) {

//销毁TGT

this.centralAuthenticationService.destroyTicketGrantingTicket(ticketGrantingTicketId);

//销毁TGTcookie

this.ticketGrantingTicketCookieGenerator.removeCookie(response);

//销毁warnCookieValue

this.warnCookieGenerator.removeCookie(response);

}

//如果service不会空

if (this.followServiceRedirects && service != null) {

final RegisteredService rService = this.servicesManager.findServiceBy(new SimpleWebApplicationServiceImpl(service));

if (rService != null && rService.isEnabled()) {

//跳转到service

return new ModelAndView(new RedirectView(service));

}

}

return new ModelAndView(this.logoutView);

}

LogoutController的handleRequestInternal要做是从request的cookies中获取TGC，从request中获取service，同时销毁服务器缓存的TGT和response中的TGC。并跳转到应用系统的service（http://127.0.0.1:8090/webapp/main.do）页面。

CentralAuthenticationServiceImpl的destroyTicketGrantingTicket方法

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public void destroyTicketGrantingTicket(final String ticketGrantingTicketId) {

Assert.notNull(ticketGrantingTicketId);

if (log.isDebugEnabled()) {

log.debug("Removing ticket [" + ticketGrantingTicketId + "] from registry.");

}

final TicketGrantingTicket ticket = (TicketGrantingTicket) this.ticketRegistry.getTicket(ticketGrantingTicketId,

TicketGrantingTicket.class);

if (ticket == null) {

return;

}

if (log.isDebugEnabled()) {

log.debug("Ticket found. Expiring and then deleting.");

}

ticket.expire();

this.ticketRegistry.deleteTicket(ticketGrantingTicketId);

}

之前在CAS服务器端创建TGT的时候，我们把TGT放到了ticketRegistry对象中，所以此时需要对ticketRegistry中的TGT进行操作，从ticketRegistry对象中获取TGT，并执行TGT的expire方法，设置TGT的属性为过期，expire方法同会时执行logOutOfServices方法。

TicketGrantingTicket的expire方法和logOutOfServices方法

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public synchronized void expire() {

this.expired = true;

logOutOfServices();

}

private void logOutOfServices() {

for (final Entry<String, Service> entry : this.services.entrySet()) {

if (!entry.getValue().logOutOfService(entry.getKey())) {

LOG.warn("Logout message not sent to [" + entry.getValue().getId() + "]; Continuing processing...");

}

}

}

logOutOfServices方法会循环所有的Service（AbstractWebApplicationService实现类），并执行logOutOfService方法。

AbstractWebApplicationService的logOutOfServices方法

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public synchronized boolean logOutOfService(final String sessionIdentifier) {

if (this.loggedOutAlready) {

return true;

}

LOG.debug("Sending logout request for: " + getId());

final String logoutRequest = "<samlp:LogoutRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\" ID=\""

+ GENERATOR.getNewTicketId("LR")

+ "\" Version=\"2.0\" IssueInstant=\"" + SamlUtils.getCurrentDateAndTime()

+ "\"><saml:NameID xmlns:saml=\"urn:oasis:names:tc:SAML:2.0:assertion\">@NOT_USED@</saml:NameID><samlp:SessionIndex>"

+ sessionIdentifier + "</samlp:SessionIndex></samlp:LogoutRequest>";

this.loggedOutAlready = true;

if (this.httpClient != null) {

return this.httpClient.sendMessageToEndPoint(getOriginalUrl(), logoutRequest, true);

}

return false;

}

logOutOfService会构造logoutRequest对象，同时执行HttpClient的sendMessageToEndPoint方法访问客户端，此时，客户端的过滤器会拦截这个请求，并对logoutRequest进行解析，获取sessionIndex（sessionIdentifier），并根据sessionIndex销毁session信息。

SingleSignOutFilter的doFilter方法

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public void doFilter(ServletRequest servletRequest,

ServletResponse servletResponse, FilterChain filterChain)

throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) servletRequest;

//request是否有ticket

if (handler.isTokenRequest(request)) {

//sessionMappingStorage记录session。

handler.recordSession(request);

} else {

//request是否有logoutRequest

if (handler.isLogoutRequest(request)) {

//sessionMappingStorag注销session。

handler.destroySession(request);

//不执行后续过滤器

return;

}

this.log.trace("Ignoring URI " + request.getRequestURI());

}

filterChain.doFilter(servletRequest, servletResponse);

}

SingleSignOutFilter的doFilter方法，要做的是如果request有ticket参数，则记录session到sessionMappingStorage中，执行后续过滤器。如果request有logoutRequest参数，则从sessionMappingStorage销毁session，不执行后续过滤器。

SingleSignOutHttpSessionListener类源码

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private SessionMappingStorage sessionMappingStorage;

public void sessionCreated(final HttpSessionEvent event) {

// nothing to do at the moment

}

public void sessionDestroyed(final HttpSessionEvent event) {

if (sessionMappingStorage == null) {

sessionMappingStorage = getSessionMappingStorage();

}

final HttpSession session = event.getSession();

//从sessionMappingStorage删除session

sessionMappingStorage.removeBySessionById(session.getId());

}

protected static SessionMappingStorage getSessionMappingStorage() {

return SingleSignOutFilter.getSingleSignOutHandler().getSessionMappingStorage();

}

当session销毁时，会触发SingleSignOutHttpSessionListener类（父类HttpSessionListener）的销毁事件，此时，sessionDestroyed方法会从sessionMappingStorage中删除session信息。完成之后，会继续执行LogoutController的handleRequestInternal方法，并跳转到应用系统的service（http://127.0.0.1:8090/webapp/main.do）页面。

至此，CAS的单点登出操作流程已经完成，正常情况下会显示CAS的登录页面。