理解java.policy

Java是一门安全性很高的语言，因此也会考虑到用户代码对整个系统的侵入性。 试想一下，如果你引用了一个jar包，里面包含了依据system.exit()，每次执行到这里都直接退出，会不会很蛋疼！

Java开发者肯定想过如此的问题，所以引入了java安全策略机制，利用一个配置文件来管理所有的代码权限。

JDK中就有这样的文件，就是 jre/lib/security/java.policy   ，参考下该文件,就能理解其中的关系：

// default permissions granted to all domains  grant {    // Allows any thread to stop itself using the java.lang.Thread.stop()    // method that takes no argument.    // Note that this permission is granted by default only to remain    // backwards compatible.    // It is strongly recommended that you either remove this permission    // from this policy file or further restrict it to code sources    // that you specify, because Thread.stop() is potentially unsafe.    // See the API specification of java.lang.Thread.stop() for more    // information.    permission java.lang.RuntimePermission "stopThread";    // allows anyone to listen on dynamic ports    permission java.net.SocketPermission "localhost:0", "listen";    // "standard" properies that can be read by anyone    permission java.util.PropertyPermission "java.version", "read";    permission java.util.PropertyPermission "java.vendor", "read";    permission java.util.PropertyPermission "java.vendor.url", "read";    permission java.util.PropertyPermission "java.class.version", "read";    permission java.util.PropertyPermission "os.name", "read";    permission java.util.PropertyPermission "os.version", "read";    permission java.util.PropertyPermission "os.arch", "read";    permission java.util.PropertyPermission "file.separator", "read";    permission java.util.PropertyPermission "path.separator", "read";    permission java.util.PropertyPermission "line.separator", "read";    permission java.util.PropertyPermission "java.specification.version", "read";    permission java.util.PropertyPermission "java.specification.vendor", "read";    permission java.util.PropertyPermission "java.specification.name", "read";    permission java.util.PropertyPermission "java.vm.specification.version", "read";    permission java.util.PropertyPermission "java.vm.specification.vendor", "read";    permission java.util.PropertyPermission "java.vm.specification.name", "read";    permission java.util.PropertyPermission "java.vm.version", "read";    permission java.util.PropertyPermission "java.vm.vendor", "read";    permission java.util.PropertyPermission "java.vm.name", "read";  };

上面给出了基本的权限，例如任何人都可以监听动态端口，以及一些读操作。

基本过程如下面的图所示：

用户如果启用了安全管理，即在执行时添加了 -Djava.security.manager , 就会 在执行某些操作前 先读取 权限文件java.policy，检查是否具体相应权限 。

当然也可以自己定义安全文件，一般有两种方式：

一种是自己创建SecuirtyManager类，创建一些checkXXX的方法，进行验证；

另一种就是创建my.policy文件（名字随意），按照规定的语法配置权限，然后启动时添加-Djava.security.manager-Djava.security.policy=xxxx/my.policy参数。

关于java本身的安全管理不是本篇的重点，下面介绍下tomcat中的安全策略。

理解tomcat中的Security

Tomcat中的安全管理原理基本与前面JDK中的security类似，只是启动时需要在start后面添加-security参数，tomcat会自动读取 conf/catalina.policy  文件中的权限配置。启动命令如下：

F:apache-tomcat-xxx/bin/startup.bat -security

catalina.policy中默认已经配置了很多的安全策略，这里就不多说明了，下个部分会针对某一特定文件进行说明：

// Licensed to the Apache Software Foundation (ASF) under one or more  // contributor license agreements.  See the NOTICE file distributed with  // this work for additional information regarding copyright ownership.  // The ASF 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  //  //  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.  // ============================================================================  // catalina.policy - Security Policy Permissions for Tomcat 6  //  // This file contains a default set of security policies to be enforced (by the  // JVM) when Catalina is executed with the "-security" option.  In addition  // to the permissions granted here, the following additional permissions are  // granted to the codebase specific to each web application:  //  // * Read access to its document root directory  // * Read, write and delete access to its working directory  // ============================================================================  // ========== SYSTEM CODE PERMISSIONS =========================================  // These permissions apply to javac  grant codeBase "file:${java.home}/lib/-" {      permission java.security.AllPermission;  };  // These permissions apply to all shared system extensions  grant codeBase "file:${java.home}/jre/lib/ext/-" {      permission java.security.AllPermission;  };  // These permissions apply to javac when ${java.home] points at $JAVA_HOME/jre  grant codeBase "file:${java.home}/../lib/-" {      permission java.security.AllPermission;  };  // These permissions apply to all shared system extensions when  // ${java.home} points at $JAVA_HOME/jre  grant codeBase "file:${java.home}/lib/ext/-" {      permission java.security.AllPermission;  };  // ========== CATALINA CODE PERMISSIONS =======================================  // These permissions apply to the daemon code  grant codeBase "file:${catalina.home}/bin/commons-daemon.jar" {      permission java.security.AllPermission;  };  // These permissions apply to the logging API  // Note: If tomcat-juli.jar is in ${catalina.base} and not in ${catalina.home},  // update this section accordingly.  //  grant codeBase "file:${catalina.base}/bin/tomcat-juli.jar" {..}  grant codeBase "file:${catalina.home}/bin/tomcat-juli.jar" {      permission java.io.FilePermission       "${java.home}${file.separator}lib${file.separator}logging.properties", "read";       permission java.io.FilePermission       "${catalina.base}${file.separator}conf${file.separator}logging.properties", "read";      permission java.io.FilePermission       "${catalina.base}${file.separator}logs", "read, write";      permission java.io.FilePermission       "${catalina.base}${file.separator}logs${file.separator}*", "read, write";      permission java.lang.RuntimePermission "shutdownHooks";      permission java.lang.RuntimePermission "getClassLoader";      permission java.lang.RuntimePermission "setContextClassLoader";      permission java.util.logging.LoggingPermission "control";      permission java.util.PropertyPermission "java.util.logging.config.class", "read";      permission java.util.PropertyPermission "java.util.logging.config.file", "read";      permission java.util.PropertyPermission "catalina.base", "read";      // Note: To enable per context logging configuration, permit read access to      // the appropriate file. Be sure that the logging configuration is      // secure before enabling such access.      // E.g. for the examples web application (uncomment and unwrap      // the following to be on a single line):      // permission java.io.FilePermission "${catalina.base}${file.separator}      //  webapps${file.separator}examples${file.separator}WEB-INF      //  ${file.separator}classes${file.separator}logging.properties", "read";  };  // These permissions apply to the server startup code  grant codeBase "file:${catalina.home}/bin/bootstrap.jar" {      permission java.security.AllPermission;  };  // These permissions apply to the servlet API classes  // and those that are shared across all class loaders  // located in the "lib" directory  grant codeBase "file:${catalina.home}/lib/-" {      permission java.security.AllPermission;  };  // If using a per instance lib directory, i.e. ${catalina.base}/lib,  // then the following permission will need to be uncommented  // grant codeBase "file:${catalina.base}/lib/-" {  //   permission java.security.AllPermission;  // };  // ========== WEB APPLICATION PERMISSIONS =====================================  // These permissions are granted by default to all web applications  // In addition, a web application will be given a read FilePermission  // and JndiPermission for all files and directories in its document root.  grant {     // Required for JNDI lookup of named JDBC DataSource's and    // javamail named MimePart DataSource used to send mail    permission java.util.PropertyPermission "java.home", "read";    permission java.util.PropertyPermission "java.naming.*", "read";    permission java.util.PropertyPermission "javax.sql.*", "read";    // OS Specific properties to allow read access    permission java.util.PropertyPermission "os.name", "read";    permission java.util.PropertyPermission "os.version", "read";    permission java.util.PropertyPermission "os.arch", "read";    permission java.util.PropertyPermission "file.separator", "read";    permission java.util.PropertyPermission "path.separator", "read";    permission java.util.PropertyPermission "line.separator", "read";    // JVM properties to allow read access    permission java.util.PropertyPermission "java.version", "read";    permission java.util.PropertyPermission "java.vendor", "read";    permission java.util.PropertyPermission "java.vendor.url", "read";    permission java.util.PropertyPermission "java.class.version", "read";    permission java.util.PropertyPermission "java.specification.version", "read";    permission java.util.PropertyPermission "java.specification.vendor", "read";    permission java.util.PropertyPermission "java.specification.name", "read";    permission java.util.PropertyPermission "java.vm.specification.version", "read";    permission java.util.PropertyPermission "java.vm.specification.vendor", "read";    permission java.util.PropertyPermission "java.vm.specification.name", "read";    permission java.util.PropertyPermission "java.vm.version", "read";    permission java.util.PropertyPermission "java.vm.vendor", "read";    permission java.util.PropertyPermission "java.vm.name", "read";    // Required for OpenJMX    permission java.lang.RuntimePermission "getAttribute";    // Allow read of JAXP compliant XML parser debug    permission java.util.PropertyPermission "jaxp.debug", "read";    // Precompiled JSPs need access to these packages.    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.jasper.el";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.jasper.runtime";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.jasper.runtime.*";    // Precompiled JSPs need access to these system properties.    permission java.util.PropertyPermission     "org.apache.jasper.runtime.BodyContentImpl.LIMIT_BUFFER", "read";    permission java.util.PropertyPermission "org.apache.el.parser.COERCE_TO_ZERO", "read";  };  // The Manager application needs access to the following packages to support the  // session display functionality. These settings support the following  // configurations:  // - default CATALINA_HOME == CATALINA_BASE  // - CATALINA_HOME != CATALINA_BASE, per instance Manager in CATALINA_BASE  // - CATALINA_HOME != CATALINA_BASE, shared Manager in CATALINA_HOME  grant codeBase "file:${catalina.base}/webapps/manager/-" {    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager.util";  };  grant codeBase "file:${catalina.home}/webapps/manager/-" {    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager";    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager.util";  };  // You can assign additional permissions to particular web applications by  // adding additional "grant" entries here, based on the code base for that  // application, /WEB-INF/classes/, or /WEB-INF/lib/ jar files.  //  // Different permissions can be granted to JSP pages, classes loaded from  // the /WEB-INF/classes/ directory, all jar files in the /WEB-INF/lib/  // directory, or even to individual jar files in the /WEB-INF/lib/ directory.  //  // For instance, assume that the standard "examples" application  // included a JDBC driver that needed to establish a network connection to the  // corresponding database and used the scrape taglib to get the weather from  // the NOAA web server.  You might create a "grant" entries like this:  //  // The permissions granted to the context root directory apply to JSP pages.  // grant codeBase "file:${catalina.base}/webapps/examples/-" {  //   permission java.net.SocketPermission "dbhost.mycompany.com:5432", "connect";  //   permission java.net.SocketPermission "*.noaa.gov:80", "connect";  // };  //  // The permissions granted to the context WEB-INF/classes directory  // grant codeBase "file:${catalina.base}/webapps/examples/WEB-INF/classes/-" {  // };  //  // The permission granted to your JDBC driver  // grant codeBase "jar:file:${catalina.base}/webapps/examples/WEB-INF/lib/driver.jar!/-" {  //   permission java.net.SocketPermission "dbhost.mycompany.com:5432", "connect";  // };  // The permission granted to the scrape taglib  // grant codeBase "jar:file:${catalina.base}/webapps/examples/WEB-INF/lib/scrape.jar!/-" {  //   permission java.net.SocketPermission "*.noaa.gov:80", "connect";  // };

这里需要注意的是其配置语法：

grant [signedBy <signer>,] [codeBase <code source>] {    permission <class> [<name> [, <action list>]];  };

都要按照上面的格式进行配置。其中：

codeBase 是通过URL的方式指定文件，可以使用变量${java.home}或者${catalina.home}来表示JDK和tomcat的根目录。

class 指定了相应的操作

[name,[,action]] name指定具体的操作或者文件，action指定可选的动作（比如read write等等）。

具体的配置样例，可以参考上面的默认文件。

另外要说明的就是都可以配置哪些操作，也就是permission后面都可以跟哪些类，他们的作用都是什么？

上面列表中，最常用的java.io.FilePermission用于文件的操作、java.lang.RuntimePermission（可以通过禁用该权限达到防止system.exit(1)的目的）等等。

Security配置实战

在tomcat中配置security，可以按照下面几个步骤：

1 在样例代码中执行特殊权限操作：

<%@ page language="java" contentType="text/html; charset=utf-8"    import="java.net.*,java.io.*"    pageEncoding="utf-8"%>  <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  <html>  <head>  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">  <title>security Test</title>  </head>  <body>    <h1>security Test</h1>    <hr>    <%!    String txt2String(File file){      String result = "";      try{        BufferedReader br = new BufferedReader(new FileReader(file));//构造一个BufferedReader类来读取文件        String s = null;        while((s = br.readLine())!=null){//使用readLine方法，一次读一行          result = result + "\n" +s;        }        br.close();       }catch(Exception e){        e.printStackTrace();      }      return result;    }    %>    <%    //是否启用了security，如果没有启用会输入null。    System.out.println("SecurityManager: " + System.getSecurityManager());    File file = new File("C:/Users/Administrator/Desktop/test.txt");    //执行文件读操作,即java.io.FilePermission    System.out.println(txt2String(file));    //执行获取文件属性操作，即java.util.PropertyPermission    System.out.println(System.getProperty("file.encoding"));    %>  </body>  </html>

当访问该页面时，会自动执行下面的代码，如果不具有相应的权限，会直接报错：

//执行文件读操作,即java.io.FilePermission      System.out.println(txt2String(file));      //执行获取文件属性操作，即java.util.PropertyPermission      System.out.println(System.getProperty("file.encoding"));

2 配置安全策略文件catalina.policy：

只需要在catalina.policy末尾添加如下的配置即可：

grant {       permission java.io.FilePermission "C:/Users/Administrator/Desktop/test.txt", "read";      permission java.util.PropertyPermission "file.encoding", "read";  };

3 在命令行中添加-security启动

访问JSP执行代码，样例中访问 http://localhost:8080/JSPTest/securityTest.jsp

可以看到控制台正常输出：

对比下正常启动的输出，SecurityManager会输出null （ 此时，如果JSP中有system.exit(1);程序就会直接退出 ）：

如果没有配置读写文件的权限，会报错（注释掉安全配置的第一句）：

grant {       //permission java.io.FilePermission "C:/Users/Administrator/Desktop/test.txt", "read";      permission java.util.PropertyPermission "file.encoding", "read";  };

如果没有配置获取文件属性权限，则会报错：

grant {       permission java.io.FilePermission "C:/Users/Administrator/Desktop/test.txt", "read";      //permission java.util.PropertyPermission "file.encoding", "read";  };

因此，如果在安全管理模式下，进行了越权的操作，就会报错有的甚至直接导致程序退出。

通过报错信息，可以快速的知道缺乏什么权限，根绝该报错就可以方便的配置安全策略。

参考

【1】Java.security.policy文件：http://www.tmser.com/post-187.html

【2】Java安全管理器：http://bubuko.com/infodetail-306759.html

【3】tomcat 6.0 security manager:http://tomcat.apache.org/tomcat-6.0-doc/security-manager-howto.html