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| Version: 9.3.28.v20191105</span></td><td style="width: 50%"></td></tr></table><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Limiting Form Content</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="configuring-security-authentication.html"><i class="fa fa-chevron-left" aria-hidden="true"></i> Previous</a> </td><th width="60%" align="center">Chapter 7. Configuring Security<br><a accesskey="p" href="index.html"><i class="fa fa-home" aria-hidden="true"></i> Home</a></th><td width="20%" align="right"> <a accesskey="n" href="serving-aliased-files.html">Next <i class="fa fa-chevron-right" aria-hidden="true"></i></a></td></tr></table><hr></div><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="jetty-callout"><h5 class="callout"><a href="http://www.webtide.com/">Contact the core Jetty developers at |
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| </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="configuring-form-size"></a>Limiting Form Content</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="configuring-form-size.html#_configuring_form_limits_for_a_webapp">Configuring Form Limits for a Webapp</a></span></dt><dt><span class="section"><a href="configuring-form-size.html#_configuring_form_limits_for_the_server">Configuring Form Limits for the Server</a></span></dt></dl></div><p>Form content sent to the server is processed by Jetty into a map of parameters to be used by the web application. |
| This can be vulnerable to denial of service (DOS) attacks since significant memory and CPU can be consumed if a malicious clients sends very large form content or large number of form keys. |
| Thus Jetty limits the amount of data and keys that can be in a form posted to Jetty.</p><p>The default maximum size Jetty permits is 200000 bytes and 1000 keys. |
| You can change this default for a particular webapp or for all webapps on a particular Server instance.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_configuring_form_limits_for_a_webapp"></a>Configuring Form Limits for a Webapp</h3></div></div></div><p>To configure the form limits for a single web application, the context handler (or webappContext) instance must be configured using the following methods:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code>ContextHandler.setMaxFormContentSize(int maxSizeInBytes); |
| ContextHandler.setMaxFormKeys(int formKeys);</code></pre><p>These methods may be called directly when embedding Jetty, but more commonly are configured from a context XML file or WEB-INF/jetty-web.xml file:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code><Configure class="org.eclipse.jetty.webapp.WebAppContext"> |
| |
| ... |
| |
| <Set name="maxFormContentSize">200000</Set> |
| <Set name="maxFormKeys">200</Set> |
| </Configure></code></pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_configuring_form_limits_for_the_server"></a>Configuring Form Limits for the Server</h3></div></div></div><p>If a context does not have specific form limits configured, then the server attributes are inspected to see if a server wide limit has been set on the size or keys. |
| The following XML shows how these attributes can be set in <code class="literal">jetty.xml</code>:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code><configure class="org.eclipse.jetty.server.Server"> |
| |
| ... |
| |
| <Call name="setAttribute"> |
| <Arg>org.eclipse.jetty.server.Request.maxFormContentSize</Arg> |
| <Arg>100000</Arg> |
| </Call> |
| <Call name="setAttribute"> |
| <Arg>org.eclipse.jetty.server.Request.maxFormKeys</Arg> |
| <Arg>2000</Arg> |
| </Call> |
| </configure></code></pre></div></div><script type="text/javascript"> |
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