586 lines
41 KiB
HTML
586 lines
41 KiB
HTML
<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Apache Tomcat 7 (7.0.108) - Security Considerations</title><style type="text/css" media="print">
|
|
.noPrint {display: none;}
|
|
td#mainBody {width: 100%;}
|
|
</style><style type="text/css">
|
|
code {background-color:rgb(224,255,255);padding:0 0.1em;}
|
|
code.attributeName, code.propertyName {background-color:transparent;}
|
|
|
|
|
|
table {
|
|
border-collapse: collapse;
|
|
text-align: left;
|
|
}
|
|
table *:not(table) {
|
|
/* Prevent border-collapsing for table child elements like <div> */
|
|
border-collapse: separate;
|
|
}
|
|
|
|
th {
|
|
text-align: left;
|
|
}
|
|
|
|
|
|
div.codeBox pre code, code.attributeName, code.propertyName, code.noHighlight, .noHighlight code {
|
|
background-color: transparent;
|
|
}
|
|
div.codeBox {
|
|
overflow: auto;
|
|
margin: 1em 0;
|
|
}
|
|
div.codeBox pre {
|
|
margin: 0;
|
|
padding: 4px;
|
|
border: 1px solid #999;
|
|
border-radius: 5px;
|
|
background-color: #eff8ff;
|
|
display: table; /* To prevent <pre>s from taking the complete available width. */
|
|
/*
|
|
When it is officially supported, use the following CSS instead of display: table
|
|
to prevent big <pre>s from exceeding the browser window:
|
|
max-width: available;
|
|
width: min-content;
|
|
*/
|
|
}
|
|
|
|
div.codeBox pre.wrap {
|
|
white-space: pre-wrap;
|
|
}
|
|
|
|
|
|
table.defaultTable tr, table.detail-table tr {
|
|
border: 1px solid #CCC;
|
|
}
|
|
|
|
table.defaultTable tr:nth-child(even), table.detail-table tr:nth-child(even) {
|
|
background-color: #FAFBFF;
|
|
}
|
|
|
|
table.defaultTable tr:nth-child(odd), table.detail-table tr:nth-child(odd) {
|
|
background-color: #EEEFFF;
|
|
}
|
|
|
|
table.defaultTable th, table.detail-table th {
|
|
background-color: #88b;
|
|
color: #fff;
|
|
}
|
|
|
|
table.defaultTable th, table.defaultTable td, table.detail-table th, table.detail-table td {
|
|
padding: 5px 8px;
|
|
}
|
|
|
|
|
|
p.notice {
|
|
border: 1px solid rgb(255, 0, 0);
|
|
background-color: rgb(238, 238, 238);
|
|
color: rgb(0, 51, 102);
|
|
padding: 0.5em;
|
|
margin: 1em 2em 1em 1em;
|
|
}
|
|
</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="https://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 7.0.108, Jan 28 2021</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="https://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="host-manager-howto.html">6) Host Manager</a></li><li><a href="realm-howto.html">7) Realms and AAA</a></li><li><a href="security-manager-howto.html">8) Security Manager</a></li><li><a href="jndi-resources-howto.html">9) JNDI Resources</a></li><li><a href="jndi-datasource-examples-howto.html">10) JDBC DataSources</a></li><li><a href="class-loader-howto.html">11) Classloading</a></li><li><a href="jasper-howto.html">12) JSPs</a></li><li><a href="ssl-howto.html">13) SSL/TLS</a></li><li><a href="ssi-howto.html">14) SSI</a></li><li><a href="cgi-howto.html">15) CGI</a></li><li><a href="proxy-howto.html">16) Proxy Support</a></li><li><a href="mbeans-descriptors-howto.html">17) MBeans Descriptors</a></li><li><a href="default-servlet.html">18) Default Servlet</a></li><li><a href="cluster-howto.html">19) Clustering</a></li><li><a href="balancer-howto.html">20) Load Balancer</a></li><li><a href="connectors.html">21) Connectors</a></li><li><a href="monitoring.html">22) Monitoring and Management</a></li><li><a href="logging.html">23) Logging</a></li><li><a href="apr.html">24) APR/Native</a></li><li><a href="virtual-hosting-howto.html">25) Virtual Hosting</a></li><li><a href="aio.html">26) Advanced IO</a></li><li><a href="extras.html">27) Additional Components</a></li><li><a href="maven-jars.html">28) Mavenized</a></li><li><a href="security-howto.html">29) Security Considerations</a></li><li><a href="windows-service-howto.html">30) Windows Service</a></li><li><a href="windows-auth-howto.html">31) Windows Authentication</a></li><li><a href="jdbc-pool.html">32) Tomcat's JDBC Pool</a></li><li><a href="web-socket-howto.html">33) 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="annotationapi/index.html">Common Annotations 1.1 Javadocs</a></li><li><a href="https://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="https://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="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. In the
|
|
<code>.tar.gz</code> distribution, files and directories are not world
|
|
readable and the group does not have write access. On Unix like operating
|
|
systems, Tomcat runs with a default umask of <code>0027</code> to maintain
|
|
these permissions for files created while Tomcat is running (e.g. log files,
|
|
expanded WARs, etc.).</p>
|
|
<p>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 Tomcat.</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. Given 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 JNI Library Loading Listener may be used to load native code. It should
|
|
only be used to load trusted libraries.</p>
|
|
<p>The Security Lifecycle 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, a non-TLS, HTTP/1.1 connector is configured on port 8080.
|
|
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 a connector listens on for connections. By default, a 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>discardFacades</strong> attribute set 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>encodedSolidusHandling</strong> attribute allows
|
|
non-standard parsing of the request URI. Setting this attribute to a
|
|
non-default value when behind a reverse proxy may enable an attacker to
|
|
bypass any security constraints enforced by the proxy.</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), 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 to
|
|
8.0.x is Apache-Coyote/1.1. From 8.5.x onwards this header is not set by
|
|
default. 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>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 (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 correct 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>
|
|
|
|
<p>The <strong>persistAuthentication</strong> controls whether the
|
|
authenticated Principal associated with the session (if any) is included
|
|
when the session is persisted during a restart or to a Store.</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>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 correct 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>When using the CGI Servlet on Windows with
|
|
<code>enableCmdLineArguments</code> enabled, review the setting of
|
|
<code>cmdLineArgumentsDecoded</code> carefully and ensure that it is
|
|
appropriate for your environment. The default value is secure. Insecure
|
|
configurations may expose the server to remote code execution. Further
|
|
information on the potential risks and mitigations may be found by
|
|
following the links in the <a href="cgi-howto.html">CGI How To</a>.</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><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em>
|
|
Copyright © 1999-2021, Apache Software Foundation
|
|
</em></font></div></td></tr></table></body></html> |