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<!DOCTYPE document [
<!ENTITY project SYSTEM "project.xml">
]>
<document url="ssl-howto.html">
&project;
<properties>
<author email="ccain@apache.org">Christopher Cain</author>
<author email="yoavs@apache.org">Yoav Shapira</author>
<title>SSL Configuration HOW-TO</title>
</properties>
<body>
<section name="Table of Contents">
<toc/>
</section>
<section name="Quick Start">
<blockquote><em>
<p>The description below uses the variable name $CATALINA_BASE to refer the
base directory against which most relative paths are resolved. If you have
not configured Tomcat 6 for multiple instances by setting a CATALINA_BASE
directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
the directory into which you have installed Tomcat 6.</p>
</em></blockquote>
<p>To install and configure SSL support on Tomcat 6, you need to follow
these simple steps. For more information, read the rest of this HOW-TO.</p>
<ol>
<li>Create a keystore file to store the server's private key and
self-signed certificate by executing the following command:
<p>Windows:</p>
<source>
%JAVA_HOME%\bin\keytool -genkey -alias tomcat -keyalg RSA
</source>
<p>Unix:</p>
<source>
$JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA
</source>
<p></p>
and specify a password value of "changeit".</li><br/><br/>
<li>Uncomment the "SSL HTTP/1.1 Connector" entry in
<code>$CATALINA_BASE/conf/server.xml</code> and modify as described in
the <a href="#Configuration">Configuration section</a> below.</li>
<br/><br/>
</ol>
</section>
<section name="Introduction to SSL">
<p>SSL, or Secure Socket Layer, is a technology which allows web browsers and
web servers to communicate over a secured connection. This means that the data
being sent is encrypted by one side, transmitted, then decrypted by the other
side before processing. This is a two-way process, meaning that both the
server AND the browser encrypt all traffic before sending out data.</p>
<p>Another important aspect of the SSL protocol is Authentication. This means
that during your initial attempt to communicate with a web server over a secure
connection, that server will present your web browser with a set of
credentials, in the form of a "Certificate", as proof the site is who and what
it claims to be. In certain cases, the server may also request a Certificate
from your web browser, asking for proof that <em>you</em> are who you claim
to be. This is known as "Client Authentication," although in practice this is
used more for business-to-business (B2B) transactions than with individual
users. Most SSL-enabled web servers do not request Client Authentication.</p>
</section>
<section name="SSL and Tomcat">
<p>It is important to note that configuring Tomcat to take advantage of
secure sockets is usually only necessary when running it as a stand-alone
web server. When running Tomcat primarily as a Servlet/JSP container behind
another web server, such as Apache or Microsoft IIS, it is usually necessary
to configure the primary web server to handle the SSL connections from users.
Typically, this server will negotiate all SSL-related functionality, then
pass on any requests destined for the Tomcat container only after decrypting
those requests. Likewise, Tomcat will return cleartext responses, that will
be encrypted before being returned to the user's browser. In this environment,
Tomcat knows that communications between the primary web server and the
client are taking place over a secure connection (because your application
needs to be able to ask about this), but it does not participate in the
encryption or decryption itself.</p>
</section>
<section name="Certificates">
<p>In order to implement SSL, a web server must have an associated Certificate
for each external interface (IP address) that accepts secure connections.
The theory behind this design is that a server should provide some kind of
reasonable assurance that its owner is who you think it is, particularly
before receiving any sensitive information. While a broader explanation of
Certificates is beyond the scope of this document, think of a Certificate
as a "digital driver's license" for an Internet address. It states what
company the site is associated with, along with some basic contact
information about the site owner or administrator.</p>
<p>This "driver's license" is cryptographically signed by its owner, and is
therefore extremely difficult for anyone else to forge. For sites involved
in e-commerce, or any other business transaction in which authentication of
identity is important, a Certificate is typically purchased from a well-known
<em>Certificate Authority</em> (CA) such as VeriSign or Thawte. Such
certificates can be electronically verified -- in effect, the Certificate
Authority will vouch for the authenticity of the certificates that it grants,
so you can believe that that Certificate is valid if you trust the Certificate
Authority that granted it.</p>
<p>In many cases, however, authentication is not really a concern. An
administrator may simply want to ensure that the data being transmitted and
received by the server is private and cannot be snooped by anyone who may be
eavesdropping on the connection. Fortunately, Java provides a relatively
simple command-line tool, called <code>keytool</code>, which can easily create
a "self-signed" Certificate. Self-signed Certificates are simply user
generated Certificates which have not been officially registered with any
well-known CA, and are therefore not really guaranteed to be authentic at all.
Again, this may or may not even be important, depending on your needs.</p>
</section>
<section name="General Tips on Running SSL">
<p>The first time a user attempts to access a secured page on your site,
he or she is typically presented with a dialog containing the details of
the certificate (such as the company and contact name), and asked if he or she
wishes to accept the Certificate as valid and continue with the transaction.
Some browsers will provide an option for permanently accepting a given
Certificate as valid, in which case the user will not be bothered with a
prompt each time they visit your site. Other browsers do not provide this
option. Once approved by the user, a Certificate will be considered valid
for at least the entire browser session.</p>
<p>Also, while the SSL protocol was designed to be as efficient as securely
possible, encryption/decryption is a computationally expensive process from
a performance standpoint. It is not strictly necessary to run an entire
web application over SSL, and indeed a developer can pick and choose which
pages require a secure connection and which do not. For a reasonably busy
site, it is customary to only run certain pages under SSL, namely those
pages where sensitive information could possibly be exchanged. This would
include things like login pages, personal information pages, and shopping
cart checkouts, where credit card information could possibly be transmitted.
Any page within an application can be requested over a secure socket by
simply prefixing the address with <code>https:</code> instead of
<code>http:</code>. Any pages which absolutely <strong>require</strong>
a secure connection should check the protocol type associated with the
page request and take the appropriate action if <code>https</code> is not
specified.</p>
<p>Finally, using name-based virtual hosts on a secured connection can be
problematic. This is a design limitation of the SSL protocol itself. The SSL
handshake, where the client browser accepts the server certificate, must occur
before the HTTP request is accessed. As a result, the request information
containing the virtual host name cannot be determined prior to authentication,
and it is therefore not possible to assign multiple certificates to a single
IP address. If all virtual hosts on a single IP address need to authenticate
against the same certificate, the addition of multiple virtual hosts should not
interfere with normal SSL operations on the server. Be aware, however, that
most client browsers will compare the server's domain name against the domain
name listed in the certificate, if any (applicable primarily to official,
CA-signed certificates). If the domain names do not match, these browsers will
display a warning to the client user. In general, only address-based virtual
hosts are commonly used with SSL in a production environment.</p>
</section>
<section name="Configuration">
<subsection name="Prepare the Certificate Keystore">
<p>Tomcat currently operates only on <code>JKS</code>, <code>PKCS11</code> or
<code>PKCS12</code> format keystores. The <code>JKS</code> format
is Java's standard "Java KeyStore" format, and is the format created by the
<code>keytool</code> command-line utility. This tool is included in the JDK.
The <code>PKCS12</code> format is an internet standard, and can be manipulated
via (among other things) OpenSSL and Microsoft's Key-Manager.
</p>
<p>Each entry in a keystore is identified by an alias string. Whilst many
keystore implementations treat aliases in a case insensitive manner, case
sensitive implementations are available. The <code>PKCS11</code> specification,
for example, requires that aliases are case sensitive. To avoid issues related
to the case sensitivity of aliases, it is not recommended to use aliases that
differ only in case.
</p>
<p>To import an existing certificate into a JKS keystore, please read the
documentation (in your JDK documentation package) about <code>keytool</code>.
Note that OpenSSL often adds readable comments before the key,
<code>keytool</code>does not support that, so remove the OpenSSL comments if
they exist before importing the key using <code>keytool</code>.
</p>
<p>To import an existing certificate signed by your own CA into a PKCS12
keystore using OpenSSL you would execute a command like:
<source>openssl pkcs12 -export -in mycert.crt -inkey mykey.key \
-out mycert.p12 -name tomcat -CAfile myCA.crt \
-caname root -chain
</source>
For more advanced cases, consult the <a href="http://www.openssl.org/">OpenSSL
documentation</a>.
</p>
<p>To create a new keystore from scratch, containing a single self-signed
Certificate, execute the following from a terminal command line:</p>
<p>Windows:</p>
<source>
%JAVA_HOME%\bin\keytool -genkey -alias tomcat -keyalg RSA
</source>
<p>Unix:</p>
<source>
$JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA
</source>
<p>(The RSA algorithm should be preferred as a secure algorithm, and this
also ensures general compatibility with other servers and components.)</p>
<p>This command will create a new file, in the home directory of the user
under which you run it, named "<code>.keystore</code>". To specify a
different location or filename, add the <code>-keystore</code> parameter,
followed by the complete pathname to your keystore file,
to the <code>keytool</code> command shown above. You will also need to
reflect this new location in the <code>server.xml</code> configuration file,
as described later. For example:</p>
<p>Windows:</p>
<source>
%JAVA_HOME%\bin\keytool -genkey -alias tomcat -keyalg RSA \
-keystore \path\to\my\keystore
</source>
<p>Unix:</p>
<source>
$JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA \
-keystore /path/to/my/keystore
</source>
<p>After executing this command, you will first be prompted for the keystore
password. The default password used by Tomcat is "<code>changeit</code>"
(all lower case), although you can specify a custom password if you like.
You will also need to specify the custom password in the
<code>server.xml</code> configuration file, as described later.</p>
<p>Next, you will be prompted for general information about this Certificate,
such as company, contact name, and so on. This information will be displayed
to users who attempt to access a secure page in your application, so make
sure that the information provided here matches what they will expect.</p>
<p>Finally, you will be prompted for the <em>key password</em>, which is the
password specifically for this Certificate (as opposed to any other
Certificates stored in the same keystore file). You <strong>MUST</strong>
use the same password here as was used for the keystore password itself.
This is a restriction of the Tomcat implementation.
(Currently, the <code>keytool</code> prompt will tell you that pressing the
ENTER key does this for you automatically.)</p>
<p>If everything was successful, you now have a keystore file with a
Certificate that can be used by your server.</p>
<p><strong>Note:</strong> your private key password and keystore password
should be the same. If they differ, you will get an error along the lines
of <code>java.io.IOException: Cannot recover key</code>, as documented in
<a href="http://issues.apache.org/bugzilla/show_bug.cgi?id=38217">Bugzilla issue 38217</a>,
which contains further references for this issue.</p>
</subsection>
<subsection name="Edit the Tomcat Configuration File">
<p>
Tomcat can use two different implementations of SSL:
<ul>
<li>the JSSE implementation provided as part of the Java runtime (since 1.4)</li>
<li>the APR implementation, which uses the OpenSSL engine by default.</li>
</ul>
The exact configuration details depend on which implementation is being used.
The implementation used by Tomcat is chosen automatically unless it is overriden as described below.
If the installation uses <a href="apr.html">APR</a>
- i.e. you have installed the Tomcat native library -
then it will use the APR SSL implementation, otherwise it will use the Java JSSE implementation.
</p>
<p>
To avoid auto configuration you can define which implementation to use by specifying a classname
in the <b>protocol</b> attribute of the Connector.<br/>
To define a Java (JSSE) connector, regardless of whether the APR library is loaded or not do:
<source>
<-- Define a blocking Java SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector protocol="org.apache.coyote.http11.Http11Protocol"
port="8443" .../>
<-- Define a non-blocking Java SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector protocol="org.apache.coyote.http11.Http11NioProtocol"
port="8443" .../>
</source>
Alternatively, to specify an APR connector (the APR library must be available) use:
<source>
<-- Define a APR SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector protocol="org.apache.coyote.http11.Http11AprProtocol"
port="8443" .../>
</source>
</p>
<p>If you are using APR, you have the option of configuring an alternative engine to OpenSSL.
<source>
<Listener className="org.apache.catalina.core.AprLifecycleListener"
SSLEngine="someengine" SSLRandomSeed="somedevice" />
</source>
The default value is
<source>
<Listener className="org.apache.catalina.core.AprLifecycleListener"
SSLEngine="on" SSLRandomSeed="builtin" />
</source>
So to use SSL under APR, make sure the SSLEngine attribute is set to something other than <code>off</code>.
The default value is <code>on</code> and if you specify another value, it has to be a valid engine name.
<br/>
If you haven't compiled in SSL support into your Tomcat Native library, then you can turn this initialization off
<source>
<Listener className="org.apache.catalina.core.AprLifecycleListener"
SSLEngine="off" />
</source>
SSLRandomSeed allows to specify a source of entropy. Productive system needs a reliable source of entropy
but entropy may need a lot of time to be collected therefore test systems could use no blocking entropy
sources like "/dev/urandom" that will allow quicker starts of Tomcat.
</p>
<p>The final step is to configure the Connector in the
<code>$CATALINA_BASE/conf/server.xml</code> file, where
<code>$CATALINA_BASE</code> represents the base directory for the
Tomcat 6 instance. An example <code><Connector></code> element
for an SSL connector is included in the default <code>server.xml</code>
file installed with Tomcat. For JSSE, it should look something like this:</p>
<source>
<-- Define a SSL Coyote HTTP/1.1 Connector on port 8443 -->
<!--
<Connector
port="8443" maxThreads="200"
scheme="https" secure="true" SSLEnabled="true"
keystoreFile="${user.home}/.keystore" keystorePass="changeit"
clientAuth="false" sslProtocol="TLS"/>
-->
</source>
<p>
The example above will throw an error if you have the APR and the Tomcat Native libraries in your path,
as Tomcat will try to use the APR connector. The APR connector uses different attributes for
SSL keys and certificates. An example of an APR configuration is:
<source>
<-- Define a SSL Coyote HTTP/1.1 Connector on port 8443 -->
<!--
<Connector
port="8443" maxThreads="200"
scheme="https" secure="true" SSLEnabled="true"
SSLCertificateFile="/usr/local/ssl/server.crt"
SSLCertificateKeyFile="/usr/local/ssl/server.pem"
clientAuth="optional" SSLProtocol="TLSv1"/>
-->
</source>
</p>
<p>You will note that the example SSL connector elements are commented out by
default. You can either remove the comment tags from around the the example SSL
connector you wish to use or add a new Connector element of your own. In either
case, you will need to configure the SSL Connector for your requirements
and environment. The configuration options and information on which attributes
are mandatory for the JSSE based connectors (BIO and NIO) are documented in the
SSL Support section of the <a href="config/http.html#SSL Support">HTTP
connector</a> configuration reference. The configuration options and information
on which attributes are mandatory for the APR connector are documented in the
HTTPS section of the <a href="apr.html#HTTPS">APR How-To</a>.</p>
<p>The <code>port</code> attribute (default value is 8443) is the TCP/IP
port number on which Tomcat will listen for secure connections. You can
change this to any port number you wish (such as to the default port for
<code>https</code> communications, which is 443). However, special setup
(outside the scope of this document) is necessary to run Tomcat on port
numbers lower than 1024 on many operating systems.</p>
<blockquote><em>
<p>If you change the port number here, you should also change the
value specified for the <code>redirectPort</code> attribute on the
non-SSL connector. This allows Tomcat to automatically redirect
users who attempt to access a page with a security constraint specifying
that SSL is required, as required by the Servlet Specification.</p>
</em></blockquote>
<p>After completing these configuration changes, you must restart Tomcat as
you normally do, and you should be in business. You should be able to access
any web application supported by Tomcat via SSL. For example, try:</p>
<source>
https://localhost:8443
</source>
<p>and you should see the usual Tomcat splash page (unless you have modified
the ROOT web application). If this does not work, the following section
contains some troubleshooting tips.</p>
</subsection>
</section>
<section name="Installing a Certificate from a Certificate Authority">
<p>To obtain and install a Certificate from a Certificate Authority (like verisign.com, thawte.com
or trustcenter.de), read the previous section and then follow these instructions:</p>
<subsection name="Create a local Certificate Signing Request (CSR)">
<p>In order to obtain a Certificate from the Certificate Authority of your choice
you have to create a so called Certificate Signing Request (CSR). That CSR will be used
by the Certificate Authority to create a Certificate that will identify your website
as "secure". To create a CSR follow these steps:</p>
<ul>
<li>Create a local Certificate (as described in the previous section):
<source>keytool -genkey -alias tomcat -keyalg RSA \
-keystore <your_keystore_filename></source>
Note: In some cases you will have to enter the domain of your website (i.e. <code>www.myside.org</code>)
in the field "first- and lastname" in order to create a working Certificate.
</li>
<li>The CSR is then created with:
<source>keytool -certreq -keyalg RSA -alias tomcat -file certreq.csr \
-keystore <your_keystore_filename></source>
</li>
</ul>
<p>Now you have a file called <code>certreq.csr</code> that you can submit to the Certificate Authority (look at the
documentation of the Certificate Authority website on how to do this). In return you get a Certificate.</p>
</subsection>
<subsection name="Importing the Certificate">
<p>Now that you have your Certificate you can import it into you local keystore.
First of all you have to import a so called Chain Certificate or Root Certificate into your keystore.
After that you can proceed with importing your Certificate.</p>
<ul>
<li>Download a Chain Certificate from the Certificate Authority you obtained the Certificate from.<br/>
For Verisign.com commercial certificates go to:
http://www.verisign.com/support/install/intermediate.html<br/>
For Verisign.com trial certificates go to:
http://www.verisign.com/support/verisign-intermediate-ca/Trial_Secure_Server_Root/index.html<br/>
For Trustcenter.de go to:
http://www.trustcenter.de/certservices/cacerts/en/en.htm#server<br/>
For Thawte.com go to:
http://www.thawte.com/certs/trustmap.html<br/>
</li>
<li>Import the Chain Certificate into your keystore
<source>keytool -import -alias root -keystore <your_keystore_filename> \
-trustcacerts -file <filename_of_the_chain_certificate></source>
</li>
<li>And finally import your new Certificate
<source>keytool -import -alias tomcat -keystore <your_keystore_filename> \
-file <your_certificate_filename></source>
</li>
</ul>
</subsection>
</section>
<section name="Troubleshooting">
<p>Here is a list of common problems that you may encounter when setting up
SSL communications, and what to do about them.</p>
<ul>
<li>When Tomcat starts up, I get an exception like
"java.io.FileNotFoundException: {some-directory}/{some-file} not found".
<blockquote>
<p>A likely explanation is that Tomcat cannot find the keystore file
where it is looking. By default, Tomcat expects the keystore file to
be named <code>.keystore</code> in the user home directory under which
Tomcat is running (which may or may not be the same as yours :-). If
the keystore file is anywhere else, you will need to add a
<code>keystoreFile</code> attribute to the <code><Factory></code>
element in the <a href="#Edit the Tomcat Configuration File">Tomcat
configuration file</a>.</p>
</blockquote></li>
<li>When Tomcat starts up, I get an exception like
"java.io.FileNotFoundException: Keystore was tampered with, or
password was incorrect".
<blockquote>
<p>Assuming that someone has not <em>actually</em> tampered with
your keystore file, the most likely cause is that Tomcat is using
a different password than the one you used when you created the
keystore file. To fix this, you can either go back and
<a href="#Prepare the Certificate Keystore">recreate the keystore
file</a>, or you can add or update the <code>keystorePass</code>
attribute on the <code><Connector></code> element in the
<a href="#Edit the Tomcat Configuration File">Tomcat configuration
file</a>. <strong>REMINDER</strong> - Passwords are case sensitive!</p>
</blockquote></li>
<li>When Tomcat starts up, I get an exception like
"java.net.SocketException: SSL handshake errorjavax.net.ssl.SSLException: No
available certificate or key corresponds to the SSL cipher suites which are
enabled."
<blockquote>
<p>A likely explanation is that Tomcat cannot find the alias for the server
key within the specified keystore. Check that the correct
<code>keystoreFile</code> and <code>keyAlias</code> are specified in the
<code><Connector></code> element in the
<a href="#Edit the Tomcat Configuration File">Tomcat configuration file</a>.
<strong>REMINDER</strong> - <code>keyAlias</code> values may be case
sensitive!</p>
</blockquote></li>
</ul>
<p>If you are still having problems, a good source of information is the
<strong>TOMCAT-USER</strong> mailing list. You can find pointers to archives
of previous messages on this list, as well as subscription and unsubscription
information, at
<a href="http://tomcat.apache.org/lists.html">http://tomcat.apache.org/lists.html</a>.</p>
</section>
<section name="Miscellaneous Tips and Bits">
<p>To access the SSL session ID from the request, use:<br />
<code>
String sslID = (String)request.getAttribute("javax.servlet.request.ssl_session");
</code>
<br />
For additional discussion on this area, please see
<a href="http://issues.apache.org/bugzilla/show_bug.cgi?id=22679">Bugzilla</a>.
</p>
</section>
</body>
</document>