CAS做单点登陆（SSO）——集成Java Web 项目

添加cas-client的jar包

下载cas-client，地址：http://www.ja-sig.org/downloads/cas-clients/，当前最新版本是cas-client-3.2.1-release.zip。然后解压cas-client-3.2.1-release.zip，在modules拷贝cas-client-core-3.2.1.jar到应用的WEB-INF/lib目录中。

撰写支持CAS集成的客户化包

除了在web.xml添加CAS内置的filter外（具体看配置web.xml），我们需要撰写自己支持CAS集成的客户化包。大致思路如下：

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest)servletRequest;
HttpServletResponse response = (HttpServletResponse)servletResponse;

HttpSession session = request.getSession();
//在session中自定义一个参数，以它来校验是否完成过自动登陆
Object user_login = session.getAttribute(AURORA_USER_LOGIN);
if (user_login != null){
//登陆过，就继续执行其他filter
filterChain.doFilter(request, response);
return;
}
//通过CAS的API获得登陆账号
String loginName = AssertionHolder.getAssertion().getPrincipal().getName();
try {
//执行本系统的登陆。跟平常同时校验用户名和密码不同，这里只有用户名。
executeLoginProc(request,response,loginName);
} catch (Exception e) {
logger.log(Level.SEVERE, "executeLoginProc error:", e);
return;
}
//登陆成功
session.setAttribute(AURORA_USER_LOGIN, Boolean.TRUE);
//跳转到登陆成功后的页面
response.sendRedirect(roleSelectPageUrl);
}

把这个class打包成一个jar拷贝到应用的WEB-INF/lib目录中。

如果有兴趣，还可以简单了解下org.jasig.cas.client.authentication.AuthenticationFilter这个CAS内置filter的功能

public final void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest)servletRequest;
HttpServletResponse response = (HttpServletResponse)servletResponse;
HttpSession session = request.getSession(false);
//检查自定义属性"_const_cas_assertion_"
Assertion assertion = session != null ? (Assertion)session.getAttribute("_const_cas_assertion_") : null;
if (assertion != null) {
//已经成功登陆过CAS
filterChain.doFilter(request, response);
return;
}
//拿到url，并检查url参数中的ticket是否有效
String serviceUrl = constructServiceUrl(request, response);
String ticket = CommonUtils.safeGetParameter(request, getArtifactParameterName());
boolean wasGatewayed = this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);
if ((CommonUtils.isNotBlank(ticket)) || (wasGatewayed)) {
//ticket有效
filterChain.doFilter(request, response);
return;
}
this.log.debug("no ticket and no assertion found");
String modifiedServiceUrl;
String modifiedServiceUrl;
if (this.gateway) {
this.log.debug("setting gateway attribute in session");
modifiedServiceUrl = this.gatewayStorage.storeGatewayInformation(request, serviceUrl);
} else {
modifiedServiceUrl = serviceUrl;
}
if (this.log.isDebugEnabled()) {
this.log.debug("Constructed service url: " + modifiedServiceUrl);
}
String urlToRedirectTo = CommonUtils.constructRedirectUrl(this.casServerLoginUrl, getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);
if (this.log.isDebugEnabled()) {
this.log.debug("redirecting to \"" + urlToRedirectTo + "\"");
}
//重定向到cas的登陆页面
response.sendRedirect(urlToRedirectTo);
}

修改web.xml

在应用WEB-INF/web.xml添加filter的内容，效果如下所示

<!-- ======================== 单点登录开始 ======================== -->
<!-- 用于单点退出，该过滤器用于实现单点登出功能，可选配置-->
<listener>
<listener-class>org.jasig.cas.client.session.SingleSignOutHttpSessionListener</listener-class>
</listener>

<!-- 该过滤器用于实现单点登出功能，可选配置。 -->
<filter>
<filter-name>CAS Single Sign Out Filter</filter-name>
<filter-class>org.jasig.cas.client.session.SingleSignOutFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CAS Single Sign Out Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!-- 该过滤器负责用户的认证工作，必须启用它 -->
<filter>
<filter-name>CASFilter</filter-name>
<filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class>
<init-param>
<param-name>casServerLoginUrl</param-name>
<param-value>https://sso.aurora-framework.org:8080/cas/login</param-value>
<!--这里的server是服务端的IP-->
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>https://sso.aurora-framework.org:8080</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CASFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!-- 该过滤器负责对Ticket的校验工作，必须启用它 -->
<filter>
<filter-name>CAS Validation Filter</filter-name>
<filter-class>
org.jasig.cas.client.validation.Cas20ProxyReceivingTicketValidationFilter</filter-class>
<init-param>
<param-name>casServerUrlPrefix</param-name>
<param-value>https://sso.aurora-framework.org:8080/cas</param-value>
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>https://sso.aurora-framework.org:8080</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CAS Validation Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!--
该过滤器负责实现HttpServletRequest请求的包裹，
比如允许开发者通过HttpServletRequest的getRemoteUser()方法获得SSO登录用户的登录名，可选配置。
-->
<filter>
<filter-name>CAS HttpServletRequest Wrapper Filter</filter-name>
<filter-class>
org.jasig.cas.client.util.HttpServletRequestWrapperFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CAS HttpServletRequest Wrapper Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!--
该过滤器使得开发者可以通过org.jasig.cas.client.util.AssertionHolder来获取用户的登录名。
比如AssertionHolder.getAssertion().getPrincipal().getName()。
-->
<filter>
<filter-name>CAS Assertion Thread Local Filter</filter-name>
<filter-class>org.jasig.cas.client.util.AssertionThreadLocalFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CAS Assertion Thread Local Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!-- 自动根据单点登录的结果设置本系统的用户信息-->
<filter>
<display-name>AutoSetUserAdapterFilter</display-name>
<filter-name>AutoSetUserAdapterFilter</filter-name>
<filter-class>aurora.plugin.sso.cas.AutoSetUserFilter</filter-class>
<init-param>
<param-name>roleSelectPageUrl</param-name>
<param-value>https://sso.aurora-framework.org:8080/yourapp/role_select.screen</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>AutoSetUserAdapterFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- ======================== 单点登录结束 ======================== -->

前面几个都是CAS的标准配置，最后一个AutoSetUserAdapterFilter（自定义，可以取其他任意名字）才是我们支持cas的客户化程序。其中roleSelectPageUrl是指用户完成单点登录后跳转的页面。

本文档撰写时java web项目和CAS用同一个tomcat，所以都用的https。否则只需要配置CAS的链接为HTTPS，本项目连接用HTTP。

修改CAS的认证逻辑

CAS默认的逻辑是用户名和密码一致就可以登陆，现在需要把原web系统的用户名和密码校验挪到CAS中。这里假设原先web系统中有一张sys_user表存储了用户名和MD5散列后的密码。

打开cas/WEB-INF/deployerConfigContext.xml

注释掉SimpleTestUsernamePasswordAuthenticationHandler这个Handler，并添加

<bean class="org.jasig.cas.adaptors.jdbc.QueryDatabaseAuthenticationHandler">
<property ref="dataSource" name="dataSource"></property>
<property name="sql" value="select t.encrypted_user_password from sys_user t where t.user_name=?"></property>
<property ref="MD5PasswordEncoder" name="passwordEncoder"></property>
</bean>

在文件末尾之前加入数据库的链接：

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName">
<value>oracle.jdbc.driver.OracleDriver</value>
</property>
<property name="url">
<value>jdbc:oracle:thin:@yourIP:1521:yourOracleInstanceId</value>
</property>
<property name="username">
<value>yourName</value>
</property>
<property name="password">
<value>yourPassword</value>
</property>
</bean>
<bean id="MD5PasswordEncoder" class="org.jasig.cas.authentication.handler.DefaultPasswordEncoder">
<constructor-arg index="0">
<value>MD5</value>
</constructor-arg>
</bean>

cas加入jdbc支持

复制cas-server-3.5.2\modules\cas-server-support-jdbc-3.5.2.jar和oracle驱动（这里采用oracle数据）的ojdbc14.jar或者classes12.jar放到cas/WEB-INF/lib目录下。

重新登陆Web系统

重启tomcat，在浏览器中输入https://sso.aurora-framework.org:8080/yourapp/，自动跳转到如下页面：


输入web系统预先定义的用户名和密码，并跳转到自定义（web.xml中定义的）登陆成功后的页面。