# Apache Tomcat 7

Version 7.0.54, May 19 2014

 Quick Start The description below uses the variable name $CATALINA_BASE to refer the base directory against which most relative paths are resolved. If you have not configured Tomcat for multiple instances by setting a CATALINA_BASE directory, then$CATALINA_BASE will be set to the value of $CATALINA_HOME, the directory into which you have installed Tomcat. To install and configure SSL support on Tomcat, you need to follow these simple steps. For more information, read the rest of this HOW-TO. Create a keystore file to store the server's private key and self-signed certificate by executing the following command: Windows:  %JAVA_HOME%\bin\keytool -genkey -alias tomcat -keyalg RSA  Unix: $JAVA_HOME/bin/keytool -genkey -alias tomcat -keyalg RSA  and specify a password value of "changeit". Uncomment the "SSL HTTP/1.1 Connector" entry in $CATALINA_BASE/conf/server.xml and modify as described in the Configuration section below.  Introduction to SSL 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. 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 you 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.  SSL and Tomcat 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.  Certificates 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. 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 Certificate Authority (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. 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 keytool, 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.  General Tips on Running SSL 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. 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 https: instead of http:. Any pages which absolutely require a secure connection should check the protocol type associated with the page request and take the appropriate action if https is not specified. 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. Configuration  Prepare the Certificate Keystore 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, keytooldoes not support that, so remove the OpenSSL comments if they exist before importing the key using 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 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.  Edit the Tomcat Configuration File Tomcat can use two different implementations of SSL: the JSSE implementation provided as part of the Java runtime (since 1.4) the APR implementation, which uses the OpenSSL engine by default. 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 APR - 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. To avoid auto configuration you can define which implementation to use 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 do:   Alternatively, to specify an APR connector (the APR library must be available) use:   If you are using APR, you have the option of configuring an alternative engine to OpenSSL.   The default value is   So to use SSL under APR, 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 engine name. If you haven't compiled in SSL support into your Tomcat Native library, then you can turn this initialization off   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  element for an SSL connector is included in the default server.xml file installed with Tomcat. To configure an SSL connector that uses JSSE, you will need to remove the comments and edit it so it looks something like this:   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 many SSL settings, particularly keys and certificates. An example of an APR configuration is:   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