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| The Apache Tomcat Servlet/JSP Container | |
| " border="0"></a></td><td><h1><font face="arial,helvetica,sanserif">Apache Tomcat 7</font></h1><font face="arial,helvetica,sanserif">Version 7.0.77, Mar 28 2017</font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="./images/asf-logo.svg" align="right" alt="Apache Logo" border="0" style="width: 266px;height: 83px;"></a></td></tr></table><table border="0" width="100%" cellspacing="4"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--LEFT SIDE NAVIGATION--><td width="20%" valign="top" nowrap class="noPrint"><p><strong>Links</strong></p><ul><li><a href="index.html">Docs Home</a></li><li><a href="http://wiki.apache.org/tomcat/FAQ">FAQ</a></li><li><a href="#comments_section">User Comments</a></li></ul><p><strong>User Guide</strong></p><ul><li><a href="introduction.html">1) Introduction</a></li><li><a href="setup.html">2) Setup</a></li><li><a href="appdev/index.html">3) First webapp</a></li><li><a href="deployer-howto.html">4) Deployer</a></li><li><a href="manager-howto.html">5) Manager</a></li><li><a href="realm-howto.html">6) Realms and AAA</a></li><li><a href="security-manager-howto.html">7) Security Manager</a></li><li><a href="jndi-resources-howto.html">8) JNDI Resources</a></li><li><a href="jndi-datasource-examples-howto.html">9) JDBC DataSources</a></li><li><a href="class-loader-howto.html">10) Classloading</a></li><li><a href="jasper-howto.html">11) JSPs</a></li><li><a href="ssl-howto.html">12) SSL/TLS</a></li><li><a href="ssi-howto.html">13) SSI</a></li><li><a href="cgi-howto.html">14) CGI</a></li><li><a href="proxy-howto.html">15) Proxy Support</a></li><li><a href="mbeans-descriptors-howto.html">16) MBeans Descriptors</a></li><li><a href="default-servlet.html">17) Default Servlet</a></li><li><a href="cluster-howto.html">18) Clustering</a></li><li><a href="balancer-howto.html">19) Load Balancer</a></li><li><a href="connectors.html">20) Connectors</a></li><li><a href="monitoring.html">21) Monitoring and Management</a></li><li><a href="logging.html">22) Logging</a></li><li><a href="apr.html">23) APR/Native</a></li><li><a href="virtual-hosting-howto.html">24) Virtual Hosting</a></li><li><a href="aio.html">25) Advanced IO</a></li><li><a href="extras.html">26) Additional Components</a></li><li><a href="maven-jars.html">27) Mavenized</a></li><li><a href="security-howto.html">28) Security Considerations</a></li><li><a href="windows-service-howto.html">29) Windows Service</a></li><li><a href="windows-auth-howto.html">30) Windows Authentication</a></li><li><a href="jdbc-pool.html">31) Tomcat's JDBC Pool</a></li><li><a href="web-socket-howto.html">32) WebSocket</a></li></ul><p><strong>Reference</strong></p><ul><li><a href="RELEASE-NOTES.txt">Release Notes</a></li><li><a href="config/index.html">Configuration</a></li><li><a href="api/index.html">Tomcat Javadocs</a></li><li><a href="servletapi/index.html">Servlet Javadocs</a></li><li><a href="jspapi/index.html">JSP 2.2 Javadocs</a></li><li><a href="elapi/index.html">EL 2.2 Javadocs</a></li><li><a href="websocketapi/index.html">WebSocket 1.1 Javadocs</a></li><li><a href="http://tomcat.apache.org/connectors-doc/">JK 1.2 Documentation</a></li></ul><p><strong>Apache Tomcat Development</strong></p><ul><li><a href="building.html">Building</a></li><li><a href="changelog.html">Changelog</a></li><li><a href="http://wiki.apache.org/tomcat/TomcatVersions">Status</a></li><li><a href="developers.html">Developers</a></li><li><a href="architecture/index.html">Architecture</a></li><li><a href="funcspecs/index.html">Functional Specs.</a></li><li><a href="tribes/introduction.html">Tribes</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left" id="mainBody"><h1>Security Considerations</h1><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Table of Contents"><!--()--></a><a name="Table_of_Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote> | |
| <ul><li><a href="#Introduction">Introduction</a></li><li><a href="#Non-Tomcat_settings">Non-Tomcat settings</a><ol><li><a href="#JMX">JMX</a></li></ol></li><li><a href="#Default_web_applications">Default web applications</a><ol><li><a href="#Default_web_applications/General">General</a></li><li><a href="#ROOT">ROOT</a></li><li><a href="#Documentation">Documentation</a></li><li><a href="#Examples">Examples</a></li><li><a href="#Default_web_applications/Manager">Manager</a></li><li><a href="#Host_Manager">Host Manager</a></li><li><a href="#Securing_Management_Applications">Securing Management Applications</a></li></ol></li><li><a href="#Security_manager">Security manager</a></li><li><a href="#server.xml">server.xml</a><ol><li><a href="#server.xml/General">General</a></li><li><a href="#Server">Server</a></li><li><a href="#Listeners">Listeners</a></li><li><a href="#Connectors">Connectors</a></li><li><a href="#Host">Host</a></li><li><a href="#Context">Context</a></li><li><a href="#Valves">Valves</a></li><li><a href="#Realms">Realms</a></li><li><a href="#server.xml/Manager">Manager</a></li><li><a href="#Cluster">Cluster</a></li></ol></li><li><a href="#System_Properties">System Properties</a></li><li><a href="#web.xml">web.xml</a></li><li><a href="#General">General</a></li></ul> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Tomcat is configured to be reasonably secure for most use cases by | |
| default. Some environments may require more, or less, secure configurations. | |
| This page is to provide a single point of reference for configuration | |
| options that may impact security and to offer some commentary on the | |
| expected impact of changing those options. The intention is to provide a | |
| list of configuration options that should be considered when assessing the | |
| security of a Tomcat installation.</p> | |
| <p><strong>Note</strong>: Reading this page is not a substitute for reading | |
| and understanding the detailed configuration documentation. Fuller | |
| descriptions of these attributes may be found in the relevant documentation | |
| pages.</p> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Non-Tomcat settings"><!--()--></a><a name="Non-Tomcat_settings"><strong>Non-Tomcat settings</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Tomcat configuration should not be the only line of defense. The other | |
| components in the system (operating system, network, database, etc.) should | |
| also be secured.</p> | |
| <p>Tomcat should not be run under the root user. Create a dedicated user for | |
| the Tomcat process and provide that user with the minimum necessary | |
| permissions for the operating system. For example, it should not be possible | |
| to log on remotely using the Tomcat user.</p> | |
| <p>File permissions should also be suitably restricted. Taking the Tomcat | |
| instances at the ASF as an example (where auto-deployment is disabled and | |
| web applications are deployed as exploded directories), the standard | |
| configuration is to have all Tomcat files owned by root with group Tomcat | |
| and whilst owner has read/write privileges, group only has read and world | |
| has no permissions. The exceptions are the logs, temp and work directory | |
| that are owned by the Tomcat user rather than root. This means that even if | |
| an attacker compromises the Tomcat process, they can't change the | |
| Tomcat configuration, deploy new web applications or modify existing web | |
| applications. The Tomcat process runs with a umask of 007 to maintain these | |
| permissions.</p> | |
| <p>At the network level, consider using a firewall to limit both incoming | |
| and outgoing connections to only those connections you expect to be | |
| present.</p> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="JMX"><strong>JMX</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The security of the JMX connection is dependent on the implementation | |
| provided by the JRE and therefore falls outside the control of Tomact.</p> | |
| <p>Typically, access control is very limited (either read-only to | |
| everything or read-write to everything). Tomcat exposes a large amount | |
| of internal information and control via JMX to aid debugging, monitoring | |
| and management. Give the limited access control available, JMX access | |
| should be treated as equivalent to local root/admin access and restricted | |
| accordingly.</p> | |
| <p>The JMX access control provided by most (all?) JRE vendors does not | |
| log failed authentication attempts, nor does it provide an account | |
| lock-out feature after repeated failed authentications. This makes a | |
| brute force attack easy to mount and difficult to detect.</p> | |
| <p>Given all of the above, care should be taken to ensure that, if used, | |
| the JMX interface is appropriately secured. Options you may wish to | |
| consider to secure the JMX interface include:</p> | |
| <ul> | |
| <li>configuring a strong password for all JMX users;</li> | |
| <li>binding the JMX listener only to an internal network;</li> | |
| <li>limiting network access to the JMX port to trusted clients; and</li> | |
| <li>providing an application specific health page for use by external | |
| monitoring systems.</li> | |
| </ul> | |
| </blockquote></td></tr></table> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Default web applications"><!--()--></a><a name="Default_web_applications"><strong>Default web applications</strong></a></font></td></tr><tr><td><blockquote> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Default web applications/General"><!--()--></a><a name="Default_web_applications/General"><strong>General</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Tomcat ships with a number of web applications that are enabled by | |
| default. Vulnerabilities have been discovered in these applications in the | |
| past. Applications that are not required should be removed so the system | |
| will not be at risk if another vulnerability is discovered.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="ROOT"><strong>ROOT</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The ROOT web application presents a very low security risk but it does | |
| include the version of Tomcat that is being used. The ROOT web application | |
| should normally be removed from a publicly accessible Tomcat instance, not | |
| for security reasons, but so that a more appropriate default page is shown | |
| to users.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Documentation"><strong>Documentation</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The documentation web application presents a very low security risk but | |
| it does identify the version of Tomcat that is being used. It should | |
| normally be removed from a publicly accessible Tomcat instance.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Examples"><strong>Examples</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The examples web application should always be removed from any security | |
| sensitive installation. While the examples web application does not | |
| contain any known vulnerabilities, it is known to contain features | |
| (particularly the cookie examples that display the contents of all | |
| received and allow new cookies to be set) that may be used by an attacker | |
| in conjunction with a vulnerability in another application deployed on the | |
| Tomcat instance to obtain additional information that would otherwise be | |
| unavailable.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Default web applications/Manager"><!--()--></a><a name="Default_web_applications/Manager"><strong>Manager</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The Manager application allows the remote deployment of web | |
| applications and is frequently targeted by attackers due to the widespread | |
| use of weak passwords and publicly accessible Tomcat instances with the | |
| Manager application enabled. The Manager application is not accessible by | |
| default as no users are configured with the necessary access. If the | |
| Manager application is enabled then guidance in the section | |
| <strong>Securing Management Applications</strong> section should be | |
| followed.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Host Manager"><!--()--></a><a name="Host_Manager"><strong>Host Manager</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The Host Manager application allows the creation and management of | |
| virtual hosts - including the enabling of the Manager application for a | |
| virtual host. The Host Manager application is not accessible by default | |
| as no users are configured with the necessary access. If the Host Manager | |
| application is enabled then guidance in the section <strong>Securing | |
| Management Applications</strong> section should be followed.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Securing Management Applications"><!--()--></a><a name="Securing_Management_Applications"><strong>Securing Management Applications</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>When deploying a web application that provides management functions for | |
| the Tomcat instance, the following guidelines should be followed:</p> | |
| <ul> | |
| <li>Ensure that any users permitted to access the management application | |
| have strong passwords.</li> | |
| <li>Do not remove the use of the <a href="config/realm.html#LockOut_Realm_-_org.apache.catalina.realm.LockOutRealm">LockOutRealm</a> | |
| which prevents brute force attacks against user passwords.</li> | |
| <li>Uncomment the <a href="config/valve.html#Remote_Address_Filter">RemoteAddrValve</a> | |
| in <code>/META-INF/context.xml</code> which limits access to | |
| localhost. If remote access is required, limit it to specific IP | |
| addresses using this valve.</li> | |
| </ul> | |
| </blockquote></td></tr></table> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Security manager"><!--()--></a><a name="Security_manager"><strong>Security manager</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Enabling the security manager causes web applications to be run in a | |
| sandbox, significantly limiting a web application's ability to perform | |
| malicious actions such as calling System.exit(), establishing network | |
| connections or accessing the file system outside of the web application's | |
| root and temporary directories. However, it should be noted that there are | |
| some malicious actions, such as triggering high CPU consumption via an | |
| infinite loop, that the security manager cannot prevent.</p> | |
| <p>Enabling the security manager is usually done to limit the potential | |
| impact, should an attacker find a way to compromise a trusted web | |
| application . A security manager may also be used to reduce the risks of | |
| running untrusted web applications (e.g. in hosting environments) but it | |
| should be noted that the security manager only reduces the risks of | |
| running untrusted web applications, it does not eliminate them. If running | |
| multiple untrusted web applications, it is recommended that each web | |
| application is deployed to a separate Tomcat instance (and ideally separate | |
| hosts) to reduce the ability of a malicious web application impacting the | |
| availability of other applications.</p> | |
| <p>Tomcat is tested with the security manager enabled; but the majority of | |
| Tomcat users do not run with a security manager, so Tomcat is not as well | |
| user-tested in this configuration. There have been, and continue to be, | |
| bugs reported that are triggered by running under a security manager.</p> | |
| <p>The restrictions imposed by a security manager are likely to break most | |
| applications if the security manager is enabled. The security manager should | |
| not be used without extensive testing. Ideally, the use of a security | |
| manager should be introduced at the start of the development cycle as it can | |
| be time-consuming to track down and fix issues caused by enabling a security | |
| manager for a mature application.</p> | |
| <p>Enabling the security manager changes the defaults for the following | |
| settings:</p> | |
| <ul> | |
| <li>The default value for the <strong>deployXML</strong> attribute of the | |
| <strong>Host</strong> element is changed to <code>false</code>.</li> | |
| </ul> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="server.xml"><strong>server.xml</strong></a></font></td></tr><tr><td><blockquote> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="server.xml/General"><strong>General</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The default server.xml contains a large number of comments, including | |
| some example component definitions that are commented out. Removing these | |
| comments makes it considerably easier to read and comprehend | |
| server.xml.</p> | |
| <p>If a component type is not listed, then there are no settings for that | |
| type that directly impact security.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Server"><strong>Server</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Setting the <strong>port</strong> attribute to <code>-1</code> disables | |
| the shutdown port.</p> | |
| <p>If the shutdown port is not disabled, a strong password should be | |
| configured for <strong>shutdown</strong>.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Listeners"><strong>Listeners</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The APR Lifecycle Listener is not stable if compiled on Solaris using | |
| gcc. If using the APR/native connector on Solaris, compile it with the | |
| Sun Studio compiler.</p> | |
| <p>The Security Listener should be enabled and configured as appropriate. | |
| </p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Connectors"><strong>Connectors</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>By default, an HTTP and an AJP connector are configured. Connectors | |
| that will not be used should be removed from server.xml.</p> | |
| <p>The <strong>address</strong> attribute may be used to control which IP | |
| address the connector listens on for connections. By default, the | |
| connector listens on all configured IP addresses.</p> | |
| <p>The <strong>allowTrace</strong> attribute may be used to enable TRACE | |
| requests which can be useful for debugging. Due to the way some browsers | |
| handle the response from a TRACE request (which exposes the browser to an | |
| XSS attack), support for TRACE requests is disabled by default.</p> | |
| <p>The <strong>maxPostSize</strong> attribute controls the maximum size | |
| of a POST request that will be parsed for parameters. The parameters are | |
| cached for the duration of the request so this is limited to 2MB by | |
| default to reduce exposure to a DOS attack.</p> | |
| <p>The <strong>maxSavePostSize</strong> attribute controls the saving of | |
| POST requests during FORM and CLIENT-CERT authentication. The parameters | |
| are cached for the duration of the authentication (which may be many | |
| minutes) so this is limited to 4KB by default to reduce exposure to a DOS | |
| attack.</p> | |
| <p>The <strong>maxParameterCount</strong> attribute controls the | |
| maximum number of parameter and value pairs (GET plus POST) that can | |
| be parsed and stored in the request. Excessive parameters are ignored. | |
| If you want to reject such requests, configure a | |
| <a href="config/filter.html">FailedRequestFilter</a>.</p> | |
| <p>The <strong>xpoweredBy</strong> attribute controls whether or not the | |
| X-Powered-By HTTP header is sent with each request. If sent, the value of | |
| the header contains the Servlet and JSP specification versions, the full | |
| Tomcat version (e.g. Apache Tomcat/7.0.0), the name of the JVM vendor and | |
| the version of the JVM. This header is disabled by default. This header | |
| can provide useful information to both legitimate clients and attackers. | |
| </p> | |
| <p>The <strong>server</strong> attribute controls the value of the Server | |
| HTTP header. The default value of this header for Tomcat 4.1.x, 5.0.x, | |
| 5.5.x, 6.0.x and 7.0.x is Apache-Coyote/1.1. This header can provide | |
| limited information to both legitimate clients and attackers.</p> | |
| <p>The <strong>SSLEnabled</strong>, <strong>scheme</strong> and | |
| <strong>secure</strong> attributes may all be independently set. These are | |
| normally used when Tomcat is located behind a reverse proxy and the proxy | |
| is connecting to Tomcat via HTTP or HTTPS. They allow Tomcat to see the | |
| SSL attributes of the connections between the client and the proxy rather | |
| than the proxy and Tomcat. For example, the client may connect to the | |
| proxy over HTTPS but the proxy connects to Tomcat using HTTP. If it is | |
| necessary for Tomcat to be able to distinguish between secure and | |
| non-secure connections received by a proxy, the proxy must use separate | |
| connectors to pass secure and non-secure requests to Tomcat. If the | |
| proxy uses AJP then the SSL attributes of the client connection are | |
| passed via the AJP protocol and separate connectors are not needed.</p> | |
| <p>The <strong>sslEnabledProtocols</strong> attribute determines which | |
| versions of the SSL/TLS protocol are used. Since the POODLE attack in | |
| 2014, all SSL protocols are considered unsafe and a secure setting for | |
| this attribute in a standalone Tomcat setup might be | |
| <code>sslEnabledProtocols="TLSv1,TLSv1.1,TLSv1.2"</code></p> | |
| <p>The <strong>ciphers</strong> attribute controls the ciphers used for | |
| SSL connections. By default, the default ciphers for the JVM will be used. | |
| This usually means that the weak export grade ciphers will be included in | |
| the list of available ciphers. Secure environments will normally want to | |
| configure a more limited set of ciphers.</p> | |
| <p>The <strong>tomcatAuthentication</strong> and | |
| <strong>tomcatAuthorization</strong> attributes are used with the | |
| AJP connectors to determine if Tomcat should handle all authentication and | |
| authorisation or if authentication should be delegated to the reverse | |
| proxy (the authenticated user name is passed to Tomcat as part of the AJP | |
| protocol) with the option for Tomcat to still perform authorization.</p> | |
| <p>The <strong>allowUnsafeLegacyRenegotiation</strong> attribute provides | |
| a workaround for | |
| <a href="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-3555"> | |
| CVE-2009-3555</a>, a TLS man in the middle attack. This workaround applies | |
| to the BIO connector. It is only necessary if the underlying SSL | |
| implementation is vulnerable to CVE-2009-3555. For more information on the | |
| current state of this vulnerability and the work-arounds available see the | |
| <a href="http://tomcat.apache.org/security-7.html">Tomcat 7 security | |
| page</a>.</p> | |
| <p>The <strong>requiredSecret</strong> attribute in AJP connectors | |
| configures shared secret between Tomcat and reverse proxy in front of | |
| Tomcat. It is used to prevent unauthorized connections over AJP protocol.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Host"><strong>Host</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The host element controls deployment. Automatic deployment allows for | |
| simpler management but also makes it easier for an attacker to deploy a | |
| malicious application. Automatic deployment is controlled by the | |
| <strong>autoDeploy</strong> and <strong>deployOnStartup</strong> | |
| attributes. If both are <code>false</code>, only Contexts defined in | |
| server.xml will be deployed and any changes will require a Tomcat restart. | |
| </p> | |
| <p>In a hosted environment where web applications may not be trusted, set | |
| the <strong>deployXML</strong> attribute to <code>false</code> to ignore | |
| any context.xml packaged with the web application that may try to assign | |
| increased privileges to the web application. Note that if the security | |
| manager is enabled that the <strong>deployXML</strong> attribute will | |
| default to <code>false</code>.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Context"><strong>Context</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>This applies to <a href="config/context.html">Context</a> | |
| elements in all places where they can be defined: | |
| <code>server.xml</code> file, | |
| default <code>context.xml</code> file, | |
| per-host <code>context.xml.default</code> file, | |
| web application context file in per-host configuration directory | |
| or inside the web application.</p> | |
| <p>The <strong>crossContext</strong> attribute controls if a context is | |
| allowed to access the resources of another context. It is | |
| <code>false</code> by default and should only be changed for trusted web | |
| applications.</p> | |
| <p>The <strong>privileged</strong> attribute controls if a context is | |
| allowed to use container provided servlets like the Manager servlet. It is | |
| <code>false</code> by default and should only be changed for trusted web | |
| applications.</p> | |
| <p>The <strong>allowLinking</strong> attribute controls if a context is | |
| allowed to use linked files. If enabled and the context is undeployed, the | |
| links will be followed when deleting the context resources. To avoid this | |
| behaviour, use the <strong>aliases</strong> attribute. Changing this | |
| setting from the default of <code>false</code> on case insensitive | |
| operating systems (this includes Windows) will disable a number of | |
| security measures and allow, among other things, direct access to the | |
| WEB-INF directory.</p> | |
| <p>The <strong>sessionCookiePathUsesTrailingSlash</strong> can be used to | |
| work around a bug in a number of browsers (Internet Explorer, Safari and | |
| Edge) to prevent session cookies being exposed across applications when | |
| applications share a common path prefix. However, enabling this option | |
| can create problems for applications with Servlets mapped to | |
| <code>/*</code>. It should also be noted the RFC6265 section 8.5 makes it | |
| clear that different paths should not be considered sufficient to isolate | |
| cookies from other applications.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Valves"><strong>Valves</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>It is strongly recommended that an AccessLogValve is configured. The | |
| default Tomcat configuration includes an AccessLogValve. These are | |
| normally configured per host but may also be configured per engine or per | |
| context as required.</p> | |
| <p>Any administrative application should be protected by a | |
| RemoteAddrValve. (Note that this Valve is also available as a Filter.) | |
| The <strong>allow</strong> attribute should be used to limit access to a | |
| set of known trusted hosts.</p> | |
| <p>The default ErrorReportValve includes the Tomcat version number in the | |
| response sent to clients. To avoid this, custom error handling can be | |
| configured within each web application. Alternatively, you can explicitly | |
| configure an <a href="config/valve.html">ErrorReportValve</a> and set its | |
| <strong>showServerInfo</strong> attribute to <code>false</code>. | |
| Alternatively, the version number can be changed by creating the file | |
| CATALINA_BASE/lib/org/apache/catalina/util/ServerInfo.properties with | |
| content as follows:</p> | |
| <div class="codeBox"><pre><code> | |
| server.info=Apache Tomcat/7.0.x | |
| </code></pre></div> | |
| <p>Modify the values as required. Note that this will also change the version | |
| number reported in some of the management tools and may make it harder to | |
| determine the real version installed. The CATALINA_HOME/bin/version.bat|sh | |
| script will still report the version number.</p> | |
| <p>The default ErrorReportValve can display stack traces and/or JSP | |
| source code to clients when an error occurs. To avoid this, custom error | |
| handling can be configured within each web application. Alternatively, you | |
| can explicitly configure an <a href="config/valve.html">ErrorReportValve</a> | |
| and set its <strong>showReport</strong> attribute to <code>false</code>.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Realms"><strong>Realms</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The MemoryRealm is not intended for production use as any changes to | |
| tomcat-users.xml require a restart of Tomcat to take effect.</p> | |
| <p>The JDBCRealm is not recommended for production use as it is single | |
| threaded for all authentication and authorization options. Use the | |
| DataSourceRealm instead.</p> | |
| <p>The UserDatabaseRealm is not intended for large-scale installations. It | |
| is intended for small-scale, relatively static environments.</p> | |
| <p>The JAASRealm is not widely used and therefore the code is not as | |
| mature as the other realms. Additional testing is recommended before using | |
| this realm.</p> | |
| <p>By default, the realms do not implement any form of account lock-out. | |
| This means that brute force attacks can be successful. To prevent a brute | |
| force attack, the chosen realm should be wrapped in a LockOutRealm.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="server.xml/Manager"><strong>Manager</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The manager component is used to generate session IDs.</p> | |
| <p>The class used to generate random session IDs may be changed with | |
| the <strong>randomClass</strong> attribute.</p> | |
| <p>The length of the session ID may be changed with the | |
| <strong>sessionIdLength</strong> attribute.</p> | |
| </blockquote></td></tr></table> | |
| <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Cluster"><strong>Cluster</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>The cluster implementation is written on the basis that a secure, | |
| trusted network is used for all of the cluster related network traffic. It | |
| is not safe to run a cluster on a insecure, untrusted network.</p> | |
| </blockquote></td></tr></table> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="System Properties"><!--()--></a><a name="System_Properties"><strong>System Properties</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>Setting <strong>org.apache.catalina.connector.RECYCLE_FACADES</strong> | |
| system property to <code>true</code> will cause a new facade object to be | |
| created for each request. This reduces the chances of a bug in an | |
| application exposing data from one request to another.</p> | |
| <p>The <strong> | |
| org.apache.catalina.connector.CoyoteAdapter.ALLOW_BACKSLASH</strong> and | |
| <strong>org.apache.tomcat.util.buf.UDecoder.ALLOW_ENCODED_SLASH</strong> | |
| system properties allow non-standard parsing of the request URI. Using | |
| these options when behind a reverse proxy may enable an attacker to bypass | |
| any security constraints enforced by the proxy.</p> | |
| <p>The <strong> | |
| org.apache.catalina.connector.Response.ENFORCE_ENCODING_IN_GET_WRITER | |
| </strong> system property has security implications if disabled. Many user | |
| agents, in breach of RFC2616, try to guess the character encoding of text | |
| media types when the specification-mandated default of ISO-8859-1 should be | |
| used. Some browsers will interpret as UTF-7 a response containing characters | |
| that are safe for ISO-8859-1 but trigger an XSS vulnerability if interpreted | |
| as UTF-7.</p> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="web.xml"><strong>web.xml</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>This applies to the default <code>conf/web.xml</code> file and | |
| <code>WEB-INF/web.xml</code> files in web applications if they define | |
| the components mentioned here.</p> | |
| <p>The <a href="default-servlet.html">DefaultServlet</a> is configured | |
| with <strong>readonly</strong> set to | |
| <code>true</code>. Changing this to <code>false</code> allows clients to | |
| delete or modify static resources on the server and to upload new | |
| resources. This should not normally be changed without requiring | |
| authentication.</p> | |
| <p>The DefaultServlet is configured with <strong>listings</strong> set to | |
| <code>false</code>. This isn't because allowing directory listings is | |
| considered unsafe but because generating listings of directories with | |
| thousands of files can consume significant CPU leading to a DOS attack. | |
| </p> | |
| <p>The DefaultServlet is configured with <strong>showServerInfo</strong> | |
| set to <code>true</code>. When the directory listings is enabled the Tomcat | |
| version number is included in the response sent to clients. To avoid this, | |
| you can explicitly configure a DefaultServlet and set its | |
| <strong>showServerInfo</strong> attribute to false. | |
| Alternatively, the version number can be changed by creating the file | |
| CATALINA_BASE/lib/org/apache/catalina/util/ServerInfo.properties with | |
| content as follows:</p> | |
| <div class="codeBox"><pre><code>server.info=Apache Tomcat/7.0.x</code></pre></div> | |
| <p>Modify the values as required. Note that this will also change the version | |
| number reported in some of the management tools and may make it harder to | |
| determine the real version installed. The CATALINA_HOME/bin/version.bat|sh | |
| script will still report the version number. | |
| </p> | |
| <p>The CGI Servlet is disabled by default. If enabled, the debug | |
| initialisation parameter should not be set to <code>10</code> or higher on a | |
| production system because the debug page is not secure.</p> | |
| <p><a href="config/filter.html">FailedRequestFilter</a> | |
| can be configured and used to reject requests that had errors during | |
| request parameter parsing. Without the filter the default behaviour is | |
| to ignore invalid or excessive parameters.</p> | |
| <p><a href="config/filter.html">HttpHeaderSecurityFilter</a> can be | |
| used to add headers to responses to improve security. If clients access | |
| Tomcat directly, then you probably want to enable this filter and all the | |
| headers it sets unless your application is already setting them. If Tomcat | |
| is accessed via a reverse proxy, then the configuration of this filter needs | |
| to be co-ordinated with any headers that the reverse proxy sets.</p> | |
| </blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="General"><strong>General</strong></a></font></td></tr><tr><td><blockquote> | |
| <p>BASIC and FORM authentication pass user names and passwords in clear | |
| text. Web applications using these authentication mechanisms with clients | |
| connecting over untrusted networks should use SSL.</p> | |
| <p>The session cookie for a session with an authenticated user are nearly | |
| as useful as the user's password to an attacker and in nearly all | |
| circumstances should be afforded the same level of protection as the | |
| password itself. This usually means authenticating over SSL and continuing | |
| to use SSL until the session ends.</p> | |
| </blockquote></td></tr></table></td></tr><tr class="noPrint"><td width="20%" valign="top" nowrap class="noPrint"></td><td width="80%" valign="top" align="left"><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="comments_section" id="comments_section"><strong>Comments</strong></a></font></td></tr><tr><td><blockquote><p class="notice"><strong>Notice: </strong>This comments section collects your suggestions | |
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