Apache Tomcat 10

Tomcat currently operates only on JKS, PKCS11 or PKCS12 format keystores. The JKS format is Java's standard "Java KeyStore" format, and is the format created by the keytool command-line utility. This tool is included in the JDK. The PKCS12 format is an internet standard, and can be manipulated via (among other things) OpenSSL and Microsoft's Key-Manager.

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 PKCS11 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.

To import an existing certificate into a JKS keystore, please read the documentation (in your JDK documentation package) about keytool. Note that OpenSSL often adds readable comments before the key, but keytool does not support that. So if your certificate has comments before the key data, remove them before importing the certificate with keytool.

To import an existing certificate signed by your own CA into a PKCS12 keystore using OpenSSL you would execute a command like:

openssl pkcs12 -export -in mycert.crt -inkey mykey.key
                       -out mycert.p12 -name tomcat -CAfile myCA.crt
                       -caname root -chain

For more advanced cases, consult the OpenSSL documentation.

To create a new JKS keystore from scratch, containing a single self-signed Certificate, execute the following from a terminal command line:

Windows:

"%JAVA_HOME%\bin\keytool" -genkey -alias tomcat -keyalg RSA

Unix:

$JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA

(The RSA algorithm should be preferred as a secure algorithm, and this also ensures general compatibility with other servers and components.)

This command will create a new file, in the home directory of the user under which you run it, named ".keystore". To specify a different location or filename, add the -keystore parameter, followed by the complete pathname to your keystore file, to the keytool command shown above. You will also need to reflect this new location in the server.xml configuration file, as described later. For example:

Windows:

"%JAVA_HOME%\bin\keytool" -genkey -alias tomcat -keyalg RSA
  -keystore \path\to\my\keystore

Unix:

$JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA
  -keystore /path/to/my/keystore

After executing this command, you will first be prompted for the keystore password. The default password used by Tomcat is "changeit" (all lower case), although you can specify a custom password if you like. You will also need to specify the custom password in the server.xml configuration file, as described later.

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.

Finally, you will be prompted for the key password, which is the password specifically for this Certificate (as opposed to any other Certificates stored in the same keystore file). The keytool prompt will tell you that pressing the ENTER key automatically uses the same password for the key as the keystore. You are free to use the same password or to select a custom one. If you select a different password to the keystore password, you will also need to specify the custom password in the server.xml configuration file.

If everything was successful, you now have a keystore file with a Certificate that can be used by your server.

Tomcat can use three different implementations of SSL:

• JSSE implementation provided as part of the Java runtime
• JSSE implementation that uses OpenSSL
• APR implementation (deprecated), which uses the OpenSSL engine by default

The exact configuration details depend on which implementation is being used. If you configured Connector by specifying generic protocol="HTTP/1.1" then the implementation used by Tomcat is chosen automatically. If the installation uses APR - i.e. you have installed the Tomcat native library - then it will use the JSSE OpenSSL implementation, otherwise it will use the Java JSSE implementation.

Auto-selection of implementation can be avoided if needed. It is done by specifying a classname in the protocol attribute of the Connector.

To define a Java (JSSE) connector, regardless of whether the APR library is loaded or not, use one of the following:

<!-- Define an HTTP/1.1 Connector on port 8443, JSSE NIO implementation -->
<Connector protocol="org.apache.coyote.http11.Http11NioProtocol"
           sslImplementationName="org.apache.tomcat.util.net.jsse.JSSEImplementation"
           port="8443" .../>

<!-- Define an HTTP/1.1 Connector on port 8443, JSSE NIO2 implementation -->
<Connector protocol="org.apache.coyote.http11.Http11Nio2Protocol"
           sslImplementationName="org.apache.tomcat.util.net.jsse.JSSEImplementation"
           port="8443" .../>

The OpenSSL JSSE implementation can also be configured explicitly if needed. If the APR library is installed (as for using the APR connector), using the sslImplementationName attribute allows enabling it. When using the OpenSSL JSSE implementation, the configuration can use either the JSSE attributes or the OpenSSL attributes (as used for the APR connector), but must not mix attributes from both types in the same SSLHostConfig or Connector element.

<!-- Define an HTTP/1.1 Connector on port 8443, JSSE NIO implementation and OpenSSL -->
<Connector protocol="org.apache.coyote.http11.Http11NioProtocol" port="8443"
           sslImplementationName="org.apache.tomcat.util.net.openssl.OpenSSLImplementation"
           .../>

Alternatively, to specify a deprecated APR connector (the APR library must be available) use:

<!-- Define an HTTP/1.1 Connector on port 8443, APR implementation -->
<Connector protocol="org.apache.coyote.http11.Http11AprProtocol"
           port="8443" .../>

If you are using APR or JSSE OpenSSL, you have the option of configuring an alternative engine to OpenSSL.

<Listener className="org.apache.catalina.core.AprLifecycleListener"
          SSLEngine="someengine" SSLRandomSeed="somedevice" />

The default value is

<Listener className="org.apache.catalina.core.AprLifecycleListener"
          SSLEngine="on" SSLRandomSeed="builtin" />

Also the useAprConnector attribute may be used to have Tomcat default to using the APR connector rather than the NIO connector:

<Listener className="org.apache.catalina.core.AprLifecycleListener"
          useAprConnector="true" SSLEngine="on" SSLRandomSeed="builtin" />

So to enable OpenSSL, make sure the SSLEngine attribute is set to something other than off. The default value is on and if you specify another value, it has to be a valid OpenSSL engine name.

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.

The final step is to configure the Connector in the $CATALINA_BASE/conf/server.xml file, where $CATALINA_BASE represents the base directory for the Tomcat instance. An example <Connector> element for an SSL connector is included in the default server.xml file installed with Tomcat. To configure an SSL connector that uses JSSE with the JSSE configuration style, you will need to remove the comments and edit it so it looks something like this:

<!-- Define an SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector
    protocol="org.apache.coyote.http11.Http11NioProtocol"
    port="8443"
    maxThreads="150"
    SSLEnabled="true">
  <SSLHostConfig>
    <Certificate
      certificateKeystoreFile="${user.home}/.keystore"
      certificateKeystorePassword="changeit"
      type="RSA"
      />
    </SSLHostConfig>
</Connector>

Note: If tomcat-native is installed, the configuration will use JSSE with an OpenSSL implementation.

The APR configuration style uses different attributes for many SSL settings, particularly keys and certificates. An example of an APR configuration style is:

<!-- Define an SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector
    protocol="org.apache.coyote.http11.Http11AprProtocol"
    port="8443"
    maxThreads="150"
    SSLEnabled="true" >
  <SSLHostConfig>
    <Certificate
        certificateKeyFile="conf/localhost-rsa-key.pem"
        certificateFile="conf/localhost-rsa-cert.pem"
        certificateChainFile="conf/localhost-rsa-chain.pem"
        type="RSA"
        />
  </SSLHostConfig>
</Connector>

The configuration options and information on which attributes are mandatory, are documented in the SSL Support section of the HTTP connector configuration reference. Tomcat supports either configuration style (JSSE or OpenSSL) with all TLS connectors.

The port attribute 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 https 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.

If you change the port number here, you should also change the value specified for the redirectPort 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.

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:

https://localhost:8443/

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.

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:

• Create a local self-signed Certificate (as described in the previous section):

  keytool -genkey -alias tomcat -keyalg RSA
      -keystore <your_keystore_filename>

  Note: In some cases you will have to enter the domain of your website (i.e. www.myside.org) in the field "first- and lastname" in order to create a working Certificate.
• The CSR is then created with:

  keytool -certreq -keyalg RSA -alias tomcat -file certreq.csr
      -keystore <your_keystore_filename>

Now you have a file called certreq.csr 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.

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.

• Download a Chain Certificate from the Certificate Authority you obtained the Certificate from.
  For Verisign.com commercial certificates go to: http://www.verisign.com/support/install/intermediate.html
  For Verisign.com trial certificates go to: http://www.verisign.com/support/verisign-intermediate-ca/Trial_Secure_Server_Root/index.html
  For Trustcenter.de go to: http://www.trustcenter.de/certservices/cacerts/en/en.htm#server
  For Thawte.com go to: http://www.thawte.com/certs/trustmap.html
  
• Import the Chain Certificate into your keystore

  keytool -import -alias root -keystore <your_keystore_filename>
      -trustcacerts -file <filename_of_the_chain_certificate>

• And finally import your new Certificate

  keytool -import -alias tomcat -keystore <your_keystore_filename>
      -file <your_certificate_filename>

Each Certificate Authority tends to differ slightly from the others. They may require slightly different information and/or provide the certificate and associated certificate chain in different formats. Additionally, the rules that the Certificate Authorities use for issuing certifcates change over time. As a result you may find that the commands given above may need to be modified. If you require assitance then help is available via the Apache Tomcat users mailing list.

Apache Tomcat requires the OCSP-enabled certificate to have the OCSP responder location encoded in the certificate. The basic OCSP-related certificate authority settings in the openssl.cnf file could look as follows:

#... omitted for brevity

[x509]
x509_extensions = v3_issued

[v3_issued]
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer
# The address of your responder
authorityInfoAccess = OCSP;URI:http://127.0.0.1:8088
keyUsage = critical,digitalSignature,nonRepudiation,keyEncipherment,dataEncipherment,keyAgreement,keyCertSign,cRLSign,encipherOnly,decipherOnly
basicConstraints=critical,CA:FALSE
nsComment="Testing OCSP Certificate"

#... omitted for brevity

The settings above encode the OCSP responder address 127.0.0.1:8088 into the certificate. Note that for the following steps, you must have openssl.cnf and other configuration of your CA ready. To generate an OCSP-enabled certificate:

• Create a private key:

  openssl genrsa -aes256 -out ocsp-cert.key 4096

• Create a signing request (CSR):

  openssl req -config openssl.cnf -new -sha256 \
    -key ocsp-cert.key -out ocsp-cert.csr

• Sign the CSR:

  openssl ca -openssl.cnf -extensions ocsp -days 375 -notext \
    -md sha256 -in ocsp-cert.csr -out ocsp-cert.crt

• You may verify the certificate:

  openssl x509 -noout -text -in ocsp-cert.crt

To configure the OCSP connector, first verify that you are loading the Tomcat APR library. Check the Apache Portable Runtime (APR) based Native library for Tomcat for more information about installation of APR. A basic OCSP-enabled connector definition in the server.xml file looks as follows:

<Connector
    port="8443"
    protocol="org.apache.coyote.http11.Http11AprProtocol"
    secure="true"
    scheme="https"
    SSLEnabled="true"
  <SSLHostConfig
      caCertificateFile="/path/to/ca.pem"
      certificateVerification="require"
      certificateVerificationDepth="10" >
    <Certificate
        certificateFile="/path/to/ocsp-cert.crt"
        certificateKeyFile="/path/to/ocsp-cert.key" />
  </SSLHostConfig>

Apache Tomcat will query an OCSP responder server to get the certificate status. When testing, an easy way to create an OCSP responder is by executing the following:

openssl ocsp -port 127.0.0.1:8088 \
    -text -sha256 -index index.txt \
    -CA ca-chain.cert.pem -rkey ocsp-cert.key \
    -rsigner ocsp-cert.crt

Do note that when using OCSP, the responder encoded in the connector certificate must be running. For further information, see OCSP documentation .