背景知識(shí)

Java 的 SecurityManager 能讓 Web 瀏覽器在它自身的沙盒中運(yùn)行小型應(yīng)用（applet），從而具有防止不可信代碼訪問(wèn)本地文件系統(tǒng)的文件以及防止其連接到主機(jī)，而不是加載該應(yīng)用的位置，等等。如同 SecurityManager 能防止不可信的小型應(yīng)用在你的瀏覽器上運(yùn)行，運(yùn)行 Tomcat 時(shí)，使用 SecurityManager 也能保護(hù)服務(wù)器，使其免受木馬型的 applet、JSP、JSP Bean 以及標(biāo)簽庫(kù)的侵害，甚至也可以防止由于無(wú)意中的疏忽所造成的問(wèn)題。

假設(shè)網(wǎng)站有一位經(jīng)授權(quán)可發(fā)布 JSP 的用戶，他在無(wú)意中將下面這些代碼加入了 JSP 中：

<% System.exit(1); %>

每當(dāng) Tomcat 執(zhí)行這個(gè) JSP 文件時(shí)，Tomcat 都會(huì)退出。Java 的 SecurityManager 構(gòu)成了系統(tǒng)管理員保證服務(wù)器安全可靠的另一道防線。

警告：使用 Tomcat 代碼庫(kù)時(shí)會(huì)執(zhí)行一個(gè)安全審核。大多數(shù)關(guān)鍵包已受到保護(hù)，新的安全包保護(hù)機(jī)制已經(jīng)實(shí)施。然而，在允許不可信用戶發(fā)布 Web 應(yīng)用、JSP、servlet、bean 或標(biāo)簽庫(kù)之前，你仍要反復(fù)確定自己配置的 SecurityManager 是否滿足了要求。但不管怎么說(shuō)，利用 SecurityManager 來(lái)運(yùn)行 Tomcat 肯定比沒(méi)有它好得多

權(quán)限

權(quán)限類用于定義 Tomcat 加載的類所具有的權(quán)限。標(biāo)準(zhǔn) JDK 中包含了很多標(biāo)準(zhǔn)權(quán)限類，你還可以針對(duì)自己的 Web 應(yīng)用自定義權(quán)限類。Tomcat 支持這兩種技術(shù)。

標(biāo)準(zhǔn)權(quán)限

關(guān)于適用于 Tomcat 的標(biāo)準(zhǔn)系統(tǒng) SecurityManager 權(quán)限類，以下僅是一個(gè)簡(jiǎn)短的總結(jié)。詳情請(qǐng)查看 http://docs.oracle.com/javase/7/docs/technotes/guides/security/。

• java.util.PropertyPermission——控制對(duì) JVM 屬性的讀/寫，比如說(shuō) java.home。
• java.lang.RuntimePermission——控制一些系統(tǒng)/運(yùn)行時(shí)函數(shù)的使用，比如 exit() 和 exec()。 另外也控制包的訪問(wèn)/定義。
• java.io.FilePermission——控制對(duì)文件和目錄的讀/寫/執(zhí)行。
• java.net.SocketPermission——控制網(wǎng)絡(luò)套接字的使用。
• java.net.NetPermission——控制組播網(wǎng)絡(luò)連接的使用。
• java.lang.reflect.ReflectPermission——控制類反射的使用。
• java.security.SecurityPermission——控制對(duì) Security 方法的訪問(wèn)。
• java.security.AllPermission——允許訪問(wèn)任何權(quán)限，仿佛沒(méi)有 SecurityManager。

Tomcat 自定義權(quán)限

Tomcat 使用了一個(gè)自定義權(quán)限類 org.apache.naming.JndiPermission。該權(quán)限能夠控制對(duì) JNDI 命名的基于文件的資源的可讀訪問(wèn)。權(quán)限名就是 JNDI 名，無(wú)任何行為。后面的 * 可以用來(lái)在授權(quán)時(shí)進(jìn)行模糊匹配。比如，可以在策略文件中加入以下內(nèi)容：

permission org.apache.naming.JndiPermission "jndi://localhost/examples/*";

從而為每個(gè)部署的 Web 應(yīng)用動(dòng)態(tài)生成這樣的權(quán)限項(xiàng)，允許它們讀取自己的靜態(tài)資源，而不允許讀取其他的文件（除非顯式地賦予這些文件權(quán)限）。

另外，Tomcat 還能動(dòng)態(tài)生成下面這樣的文件權(quán)限。

permission java.io.FilePermission "** your application context**", "read";

permission java.io.FilePermission
  "** application working directory**", "read,write";
permission java.io.FilePermission
  "** application working directory**/-", "read,write,delete";

*application working directory 是部署應(yīng)用所用的文件夾或 WAR 文件。 application working directory 是應(yīng) Servlet 規(guī)范需要而提供給應(yīng)用的暫時(shí)性目錄。

利用 SecurityManager 配置 Tomcat

策略文件格式

Java SecurityManager 所實(shí)現(xiàn)的安全策略配置在 $CATALINA_BASE/conf/catalina.policy 文件中。該文件完全替代了 JDK 系統(tǒng)目錄中提供的 java.policy 文件。既可以手動(dòng)編輯 catalina.policy 文件，也可以使用Java 1.2 或以后版本附帶的 policytool 應(yīng)用。

catalina.policy 文件中的項(xiàng)使用標(biāo)準(zhǔn)的 java.policy 文件格式，如下所示：

// 策略文件項(xiàng)范例  

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

signedBy 和 codeBase 兩項(xiàng)在授予權(quán)限時(shí)是可選項(xiàng)。注釋行以 // 開(kāi)始，在當(dāng)前行結(jié)束。codeBase 以 URL 的形式。對(duì)于文件 URL，可以使用 ${java.home} 與 ${catalina.home}屬性（這些屬性代表的是使用 JAVA_HOME、CATALINA_HOME 和 CATALINA_BASE 環(huán)境變量為這些屬性定義的目錄路徑）。

默認(rèn)策略文件

默認(rèn)的 $CATALINA_BASE/conf/catalina.policy 文件如下所示：

// 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
//
// 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 each web application:
//
// * Read access to the web application's document root directory
// * Read, write and delete access to the web application's 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.lang.management.ManagementPermission "monitor";

        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 "org.apache.juli.AsyncLoggerPollInterval", "read";
        permission java.util.PropertyPermission "org.apache.juli.AsyncMaxRecordCount", "read";
        permission java.util.PropertyPermission "org.apache.juli.AsyncOverflowDropType", "read";
        permission java.util.PropertyPermission "org.apache.juli.ClassLoaderLogManager.debug", "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
// 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";

    // All JSPs need to be able to read this package
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.tomcat";

    // 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 cookie code needs these.
    permission java.util.PropertyPermission
     "org.apache.catalina.STRICT_SERVLET_COMPLIANCE", "read";
    permission java.util.PropertyPermission
     "org.apache.tomcat.util.http.ServerCookie.STRICT_NAMING", "read";
    permission java.util.PropertyPermission
     "org.apache.tomcat.util.http.ServerCookie.FWD_SLASH_IS_SEPARATOR", "read";

    // Applications using Comet need to be able to access this package
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.comet";

    // Applications using WebSocket need to be able to access these packages
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.tomcat.websocket";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.tomcat.websocket.server";
};

// 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:${catalina.base}/webapps/manager/-" {
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.ha.session";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager.util";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.util";
};
grant codeBase "file:${catalina.home}/webapps/manager/-" {
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.ha.session";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.manager.util";
    permission java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.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";
// };

使用 SecurityManager 啟動(dòng) Tomcat

一旦配置好了用于 SecurityManager 的 catalina.policy 文件，就可以使用 -security 選項(xiàng)啟動(dòng)帶有 SecurityManager 的 Tomcat。

$CATALINA_HOME/bin/catalina.sh start -security    (Unix)
%CATALINA_HOME%\bin\catalina start -security      (Windows)

配置 Tomcat 中的包保護(hù)

從 Tomcat 5 開(kāi)始，可以通過(guò)配置保護(hù) Tomcat 內(nèi)部包，使其免于被定義與訪問(wèn)。詳情查看 http://www.oracle.com/technetwork/java/seccodeguide-139067.html。

警告：假如去除默認(rèn)的包保護(hù)，可能會(huì)造成安全漏洞。

默認(rèn)屬性文件

默認(rèn)的 $CATALINA_BASE/conf/catalina.properties 文件如下所示：

#
# List of comma-separated packages that start with or equal this string
# will cause a security exception to be thrown when
# passed to checkPackageAccess unless the
# corresponding RuntimePermission ("accessClassInPackage."+package) has
# been granted.
package.access=sun.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,
org.apache.jasper.
#
# List of comma-separated packages that start with or equal this string
# will cause a security exception to be thrown when
# passed to checkPackageDefinition unless the
# corresponding RuntimePermission ("defineClassInPackage."+package) has
# been granted.
#
# by default, no packages are restricted for definition, and none of
# the class loaders supplied with the JDK call checkPackageDefinition.
#
package.definition=sun.,java.,org.apache.catalina.,org.apache.coyote.,
org.apache.tomcat.,org.apache.jasper.

一旦為 SecurityManager 配置了 catalina.properties 文件 ，記得重啟 Tomcat。

疑難解答

假如應(yīng)用執(zhí)行一個(gè)由于缺乏所需權(quán)限而被禁止的操作，當(dāng) SecurityManager 偵測(cè)到這種違規(guī)時(shí)，就會(huì)拋出 AccessControLException 或 SecurityException 異常。雖然調(diào)試缺失的權(quán)限是很有難度的，但還是有一個(gè)辦法，那就是將在執(zhí)行中制定的所有安全決策的調(diào)試輸出打開(kāi)，這需要在啟動(dòng) Tomcat 之前設(shè)置一個(gè)系統(tǒng)屬性。最簡(jiǎn)單的方法就是通過(guò) CATALINA_OPTS 環(huán)境變量來(lái)實(shí)現(xiàn)，命令如下所示：

export CATALINA_OPTS=-Djava.security.debug=all    (Unix)
set CATALINA_OPTS=-Djava.security.debug=all       (Windows)

記住，一定要在啟動(dòng) Tomcat 之前去做。

警告：這將生成很多兆的輸出內(nèi)容！但是，它能通過(guò)搜索關(guān)鍵字 FAILED 來(lái)鎖定問(wèn)題所在位置，確定需要檢查的權(quán)限。此外，查閱 Java 安全文檔可了解更多的可設(shè)置選項(xiàng)。