Tomcat 6 --- 你很少使用的安全管理SecurityManager
试想一下，如果你的JSP页面中包含一句代码“System.exit(1);”，你的web应用访问到该JSP时，会发生什么？
一般使用tomcat可能都没有注意到这个问题，本篇主要讲述tomcat 6中SecurityManager的管理机制，尽量使用简单明了的图片表示其中关系。
其他知识参考tomcat文档翻译。如有错误，请予指正。
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
