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+ </style></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="http://tomcat.apache.org/"><img src="./images/tomcat.gif" align="right" alt="
+ 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 7.0.42, Jul 2 2013</font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="./images/asf-logo.gif" align="right" alt="Apache Logo" border="0"></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</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-descriptor-howto.html">16) MBean Descriptor</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="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></li><li><a href="#Default_web_applications">Default web applications</a></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="#Manager">Manager</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 suitable 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 priviliges, 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>
+ </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>
+ <p>Tomcat ships with a number of web applications 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="#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>
+ </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>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> attribute is used with the
+ AJP connectors to determine if Tomcat should authenticate the user or if
+ authentication can be delegated to the reverse proxy that will then pass
+ the authenticated username to Tomcat as part of the AJP protocol.</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. </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>
+ </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, 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 align="left"><table cellspacing="4" cellpadding="0" border="0"><tr><td bgcolor="#023264" width="1" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td><td bgcolor="#023264" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td><td bgcolor="#023264" width="1" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td></tr><tr><td bgcolor="#023264" width="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td><td bgcolor="#ffffff" height="1"><pre>
+server.info=Apache Tomcat/7.0.x
+ </pre></td><td bgcolor="#023264" width="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td></tr><tr><td bgcolor="#023264" width="1" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td><td bgcolor="#023264" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td><td bgcolor="#023264" width="1" height="1"><img src="./images/void.gif" alt="" width="1" height="1" vspace="0" hspace="0" border="0"></td></tr></table></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.</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="Manager"><strong>Manager</strong></a></font></td></tr><tr><td><blockquote>
+ <p>The manager component is used to generate session IDs.</p>
+
+ <p>The default <strong>entropy</strong> value has been shown to generate predictable values
+ under certain conditions. For more secure session generation, this should
+ be set to a long string. This is done automatically if the APR/native
+ library is installed; a random value will be obtained from the APR/native
+ library.</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>
+ </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><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>
+ </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
+ on improving documentation for Apache Tomcat.<br><br>
+ If you have trouble and need help, read
+ <a href="http://tomcat.apache.org/findhelp.html">Find Help</a> page
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