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cas 认证流程分析

道酬勤
 道酬勤
发布于 2017/07/23 11:26
字数 1443
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CAS主要分为两部分

CAS Server端: 需单独部署(作统一的认证处理中心),负责用户校验认证功能,认证方式可从XML中检索或从数据库中检索数据进行认证。

CAS Client端:与web应用整合,负责保护web资源,当有请求访问web受保护资源时,将请求重定向到CAS Server端进行用户认证 。

用户请求web应用,cas-client-core中的AuthenticationFilter会拦截请求,doFilter方法根据是否有登录过而决定是否要重定向。

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);
    Assertion assertion = session != null?(Assertion)session.getAttribute("_const_cas_assertion_"):null;
    if(assertion != null) {
        filterChain.doFilter(request, response);
    } else {
        String serviceUrl = this.constructServiceUrl(request, response);
        String ticket = CommonUtils.safeGetParameter(request, this.getArtifactParameterName());
        boolean wasGatewayed = this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);
        if(!CommonUtils.isNotBlank(ticket) && !wasGatewayed) {
            this.log.debug("no ticket and no assertion found");
            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, this.getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);
            if(this.log.isDebugEnabled()) {
                this.log.debug("redirecting to \"" + urlToRedirectTo + "\"");
            }

            response.sendRedirect(urlToRedirectTo);
        } else {
            filterChain.doFilter(request, response);
        }
    }
}

若是首次登录,则会重定向到Cas Server端。Cas Server端的验证配置主要在deployerConfigContext.xml中。

<?xml version="1.0" encoding="UTF-8"?>
<!--

    Licensed to Jasig under one or more contributor license
    agreements. See the NOTICE file distributed with this work
    for additional information regarding copyright ownership.
    Jasig licenses this file to you under the Apache License,
    Version 2.0 (the "License"); you may not use this file
    except in compliance with the License.  You may obtain a
    copy of the License at the following location:

      http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing,
    software distributed under the License is distributed on an
    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    KIND, either express or implied.  See the License for the
    specific language governing permissions and limitations
    under the License.

-->
<!--
| deployerConfigContext.xml centralizes into one file some of the declarative configuration that
| all CAS deployers will need to modify.
|
| This file declares some of the Spring-managed JavaBeans that make up a CAS deployment.  
| The beans declared in this file are instantiated at context initialization time by the Spring 
| ContextLoaderListener declared in web.xml.  It finds this file because this
| file is among those declared in the context parameter "contextConfigLocation".
|
| By far the most common change you will need to make in this file is to change the last bean
| declaration to replace the default authentication handler with
| one implementing your approach for authenticating usernames and passwords.
+-->

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:util="http://www.springframework.org/schema/util"
       xmlns:sec="http://www.springframework.org/schema/security"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
       http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-3.2.xsd
       http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">

    <!--
       | The authentication manager defines security policy for authentication by specifying at a minimum
       | the authentication handlers that will be used to authenticate credential. While the AuthenticationManager
       | interface supports plugging in another implementation, the default PolicyBasedAuthenticationManager should
       | be sufficient in most cases.
       +-->
    <bean id="authenticationManager" class="org.jasig.cas.authentication.PolicyBasedAuthenticationManager">
        <constructor-arg>
            <map>
                <!--
                   | IMPORTANT
                   | Every handler requires a unique name.
                   | If more than one instance of the same handler class is configured, you must explicitly
                   | set its name to something other than its default name (typically the simple class name).
                   -->
                <entry key-ref="proxyAuthenticationHandler" value-ref="proxyPrincipalResolver" />
                <entry key-ref="primaryAuthenticationHandler" value-ref="primaryPrincipalResolver" />
            </map>
        </constructor-arg>

        <!-- Uncomment the metadata populator to allow clearpass to capture and cache the password
             This switch effectively will turn on clearpass.
        <property name="authenticationMetaDataPopulators">
           <util:list>
              <bean class="org.jasig.cas.extension.clearpass.CacheCredentialsMetaDataPopulator"
                    c:credentialCache-ref="encryptedMap" />
           </util:list>
        </property>
        -->

        <!--
           | Defines the security policy around authentication. Some alternative policies that ship with CAS:
           |
           | * NotPreventedAuthenticationPolicy - all credential must either pass or fail authentication
           | * AllAuthenticationPolicy - all presented credential must be authenticated successfully
           | * RequiredHandlerAuthenticationPolicy - specifies a handler that must authenticate its credential to pass
           -->
        <property name="authenticationPolicy">
            <bean class="org.jasig.cas.authentication.AnyAuthenticationPolicy" />
        </property>
    </bean>

    <!-- Required for proxy ticket mechanism. -->
    <bean id="proxyAuthenticationHandler"
          class="org.jasig.cas.authentication.handler.support.HttpBasedServiceCredentialsAuthenticationHandler"
          p:httpClient-ref="httpClient" />

    <!--
       | TODO: Replace this component with one suitable for your enviroment.
       |
       | This component provides authentication for the kind of credential used in your environment. In most cases
       | credential is a username/password pair that lives in a system of record like an LDAP directory.
       | The most common authentication handler beans:
       |
       | * org.jasig.cas.authentication.LdapAuthenticationHandler
       | * org.jasig.cas.adaptors.jdbc.QueryDatabaseAuthenticationHandler
       | * org.jasig.cas.adaptors.x509.authentication.handler.support.X509CredentialsAuthenticationHandler
       | * org.jasig.cas.support.spnego.authentication.handler.support.JCIFSSpnegoAuthenticationHandler
       -->
	<!-- 
    <bean id="primaryAuthenticationHandler"
          class="org.jasig.cas.authentication.AcceptUsersAuthenticationHandler">
        <property name="users">
            <map>
                <entry key="casuser" value="Mellon"/>
            </map>
        </property>
    </bean>
	-->
	
	<!--
	<bean id="primaryAuthenticationHandler" class="com.distinct.SearchModeSearchDatabaseAuthenticationHandler" >
		<property name="tableUsers"><value>t_user</value></property>
		<property name="fieldUser"><value>account</value></property>
		<property name="fieldPassword"><value>password</value></property>
		<property name="dataSource" ref="dataSource" />
		<property name="passwordEncoder" ref="passwordEncoder" />
	 </bean>
	-->
	
  <!-- 设置密码的加密方式,这里使用的是MD5加密 -->
	<bean id="passwordEncoder"
      class="org.jasig.cas.authentication.handler.DefaultPasswordEncoder"
      c:encodingAlgorithm="MD5"
      p:characterEncoding="UTF-8" />

  <!-- 通过数据库验证身份,自定义 -->
	<bean id="primaryAuthenticationHandler"
      class="com.cas.jdbc.QueryDatabaseAuthenticationHandler"
      p:dataSource-ref="dataSource"
      p:passwordEncoder-ref="passwordEncoder"
      p:sql="select password from t_user where account=? and status = 'active'" />



    <!-- Required for proxy ticket mechanism -->
    <bean id="proxyPrincipalResolver"
          class="org.jasig.cas.authentication.principal.BasicPrincipalResolver" />

    <!--
       | Resolves a principal from a credential using an attribute repository that is configured to resolve
       | against a deployer-specific store (e.g. LDAP).
       -->
    <bean id="primaryPrincipalResolver"
          class="org.jasig.cas.authentication.principal.PersonDirectoryPrincipalResolver" >
        <property name="attributeRepository" ref="attributeRepository" />
    </bean>

    <!--
    Bean that defines the attributes that a service may return.  This example uses the Stub/Mock version.  A real implementation
    may go against a database or LDAP server.  The id should remain "attributeRepository" though.
    +-->
    <bean id="attributeRepository" class="org.jasig.services.persondir.support.StubPersonAttributeDao"
            p:backingMap-ref="attrRepoBackingMap" />
    
    <util:map id="attrRepoBackingMap">
        <entry key="uid" value="uid" />
        <entry key="eduPersonAffiliation" value="eduPersonAffiliation" /> 
        <entry key="groupMembership" value="groupMembership" />
    </util:map>

    <!-- 
    Sample, in-memory data store for the ServiceRegistry. A real implementation
    would probably want to replace this with the JPA-backed ServiceRegistry DAO
    The name of this bean should remain "serviceRegistryDao".
    +-->
    <bean id="serviceRegistryDao" class="org.jasig.cas.services.InMemoryServiceRegistryDaoImpl"
            p:registeredServices-ref="registeredServicesList" />

    <util:list id="registeredServicesList">
        <bean class="org.jasig.cas.services.RegexRegisteredService"
              p:id="0" p:name="HTTP and IMAP" p:description="Allows HTTP(S) and IMAP(S) protocols"
              p:serviceId="^(https?|imaps?)://.*" p:evaluationOrder="10000001" />
        <!--
        Use the following definition instead of the above to further restrict access
        to services within your domain (including sub domains).
        Note that example.com must be replaced with the domain you wish to permit.
        This example also demonstrates the configuration of an attribute filter
        that only allows for attributes whose length is 3.
        -->
        <!--
        <bean class="org.jasig.cas.services.RegexRegisteredService">
            <property name="id" value="1" />
            <property name="name" value="HTTP and IMAP on example.com" />
            <property name="description" value="Allows HTTP(S) and IMAP(S) protocols on example.com" />
            <property name="serviceId" value="^(https?|imaps?)://([A-Za-z0-9_-]+\.)*example\.com/.*" />
            <property name="evaluationOrder" value="0" />
            <property name="attributeFilter">
              <bean class="org.jasig.cas.services.support.RegisteredServiceRegexAttributeFilter" c:regex="^\w{3}$" /> 
            </property>
        </bean>
        -->
    </util:list>
    
    <bean id="auditTrailManager" class="com.github.inspektr.audit.support.Slf4jLoggingAuditTrailManager" />
    
    <bean id="healthCheckMonitor" class="org.jasig.cas.monitor.HealthCheckMonitor" p:monitors-ref="monitorsList" />
  
    <util:list id="monitorsList">
      <bean class="org.jasig.cas.monitor.MemoryMonitor" p:freeMemoryWarnThreshold="10" />
      <!--
        NOTE
        The following ticket registries support SessionMonitor:
          * DefaultTicketRegistry
          * JpaTicketRegistry
        Remove this monitor if you use an unsupported registry.
      -->
      <bean class="org.jasig.cas.monitor.SessionMonitor"
          p:ticketRegistry-ref="ticketRegistry"
          p:serviceTicketCountWarnThreshold="5000"
          p:sessionCountWarnThreshold="100000" />
    </util:list>

	
    <!-- 设置数据源 -->
	 <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		  <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
		  <property name="url" value="jdbc:mysql://127.0.0.1:3306/cas?useUnicode=true&amp;characterEncoding=utf8"></property>
		  <property name="username" value="root"></property>
		  <property name="password" value="root"></property>
    </bean>
	
</beans>

登录认证过程:

用户输入登录资料后,提交至Cas Server端后,Cas Server端会返回一个ticket,及将TGC写入到Cookie中,

浏览器得到ticket后,向Cas Client发起请求(带上ticket),Cas Client端再向Cas Server端请求认证ticket

认证通过后,则Cas Client 端跳转成功页面。

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