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Configuring SSL/TLS

TLS and SSL versions
Understanding Certificates and Keys
Configuring the Jetty SslContextFactory
Configuring SSL in Jetty Distribution
Configuring SNI
Disabling/Enabling Specific Cipher Suites

This document provides an overview of how to configure SSL and TLS for Jetty.

TLS and SSL versions

Which browser/OS supports which protocols can be found on Wikipedia.

  • TLS v1.2: The protocol which should be used wherever possible. All CBC based ciphers are supported since Java 7, the new GCM modes are supported since Java 8.

Older Protocols

TLS v1.0, v1.1 and SSL v3 are no longer supported by default. If your Jetty implementation requires these protocols for legacy support, they can be enabled manually.


Once TLS v1.3 is released, there will be no workaround available for TLS v1.0 or v1.1. Plans for TLS v1.3 include banning ciphers with known vulnerabilities from being present at any level. It is recommended to upgrade any clients using these ciphers as soon as possible or face being locked into a outdated version of Jetty, Java or even OS.

By default, Jetty excludes these ciphers in the SslContextFactory. You can re-enable these by re-declaring the ciphers you want excluded in code:

SslContextFactory sslContextFactory = new SslContextFactory();

If, after making these changes, you still have issues using these ciphers they are likely being blocked at the JVM level. Locate the $JAVA_HOME/jre/lib/security/ directory for the file and examine it for any configuration that is excluding ciphers or algorithms (depending on the version of the JVM you are using the nomenclature may be different).

Understanding Certificates and Keys

Configuring SSL can be a confusing experience of keys, certificates, protocols and formats, thus it helps to have a reasonable understanding of the basics. The following links provide some good starting points:

OpenSSL vs. Keytool

For testing, the keytool utility bundled with the JDK provides the simplest way to generate the key and certificate you need.

You can also use the OpenSSL tools to generate keys and certificates, or to convert those that you have used with Apache or other servers. Since Apache and other servers commonly use the OpenSSL tool suite to generate and manipulate keys and certificates, you might already have some keys and certificates created by OpenSSL, or you might also prefer the formats OpenSSL produces.

If you want the option of using the same certificate with Jetty or a web server such as Apache not written in Java, you might prefer to generate your private key and certificate with OpenSSL.

Configuring Jetty for SSL

To configure Jetty for SSL, complete the tasks in the following sections:

Generating Key Pairs and Certificates

The simplest way to generate keys and certificates is to use the keytool application that comes with the JDK, as it generates keys and certificates directly into the keystore. See Generating Keys and Certificates with JDK’s keytool.

If you already have keys and certificates, see Loading Keys and Certificates to load them into a JSSE keystore. This section also applies if you have a renewal certificate to replace one that is expiring.

The examples below generate only basic keys and certificates. You should read the full manuals of the tools you are using if you want to specify:

  • The key size
  • The certificate expiration date
  • Alternate security providers
Generating Keys and Certificates with JDK’s keytool

The following command generates a key pair and certificate directly into file keystore:

$ keytool -keystore keystore -alias jetty -genkey -keyalg RSA


The DSA key algorithm certificate produces an error after loading several pages. In a browser, it displays a message "Could not establish an encrypted connection because certificate presented by localhost as an invalid signature." The solution is to use RSA for the key algorithm.

This command prompts for information about the certificate and for passwords to protect both the keystore and the keys within it. The only mandatory response is to provide the fully qualified host name of the server at the "first and last name" prompt. For example:

$ keytool -keystore keystore -alias jetty -genkey -keyalg RSA -sigalg SHA256withRSA
 Enter keystore password:  password
 What is your first and last name?
 What is the name of your organizational unit?
   [Unknown]:  Jetty
 What is the name of your organization?
   [Unknown]:  Mort Bay Consulting Pty. Ltd.
 What is the name of your City or Locality?
 What is the name of your State or Province?
 What is the two-letter country code for this unit?
 Is, OU=Jetty, O=Mort Bay Consulting Pty. Ltd.,
 L=Unknown, ST=Unknown, C=Unknown correct?
   [no]:  yes

 Enter key password for <jetty>
         (RETURN if same as keystore password):

You now have the minimal requirements to run an SSL connection and could proceed directly to configure an SSL connector. However, the browser will not trust the certificate you have generated, and prompts the user to this effect. While what you have at this point is often sufficient for testing, most public sites need a trusted certificate, which is demonstrated in the section generating a CSR with keytool.

If you want to use only a self signed certificate for some kind of internal admin panel add -validity <days> to the keytool call above, otherwise your certificate is only valid for one month.

If you are using Java 8 or later, then you may also use the SAN extension to set one or more names that the certificate applies to:

$ keytool -keystore keystore -alias jetty -genkey -keyalg RSA -sigalg SHA256withRSA -ext ',dns:*'
Generating Keys and Certificates with OpenSSL

The following command generates a key pair in the file jetty.key:

$ openssl genrsa -aes128 -out jetty.key

You might also want to use the -rand file argument to provide an arbitrary file that helps seed the random number generator.

The following command generates a certificate for the key into the file jetty.crt:

$ openssl req -new -x509 -newkey rsa:2048 -sha256 -key jetty.key -out jetty.crt

Adding -sha256 ensures to get a certificate with the now recommended SHA-256 signature algorithm. For the those with heightened security in mind, add -b4096 to get a 4069 bit key.

The next command prompts for information about the certificate and for passwords to protect both the keystore and the keys within it. The only mandatory response is to provide the fully qualified host name of the server at the "Common Name" prompt. For example:

$ openssl genrsa -aes128 -out jetty.key
Generating RSA private key, 2048 bit long modulus
e is 65537 (0x10001)
Enter pass phrase for jetty.key:
Verifying - Enter pass phrase for jetty.key:

$ openssl req -new -x509 -newkey rsa:2048 -sha256 -key jetty.key -out jetty.crt
Enter pass phrase for jetty.key:
You are about to be asked to enter information that will be incorporated into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank.
For some fields there will be a default value.
If you enter '.', the field will be left blank.

Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Mort Bay Consulting Pty. Ltd.
Organizational Unit Name (eg, section) []:Jetty
Common Name (e.g. server FQDN or YOUR name) []
Email Address []:


You now have the minimal requirements to run an SSL connection and could proceed directly to Loading Keys and Certificates to load these keys and certificates into a JSSE keystore. However the browser will not trust the certificate you have generated, and prompts the user to this effect. While what you have at this point is often sufficient for testing, most public sites need a trusted certificate, which is demonstrated in the section, Generating a CSR from OpenSSL to obtain a certificate.

Using Keys and Certificates from Other Sources

If you have keys and certificates from other sources, you can proceed directly to Loading Keys and Certificates.

Requesting a Trusted Certificate

The keys and certificates generated with JDK’s keytool and OpenSSL are sufficient to run an SSL connector. However the browser will not trust the certificate you have generated, and it will prompt the user to this effect.

To obtain a certificate that most common browsers will trust, you need to request a well-known certificate authority (CA) to sign your key/certificate. Such trusted CAs include: AddTrust, Entrust, GeoTrust, RSA Data Security, Thawte, VISA, ValiCert, Verisign, and beTRUSTed, among others. Each CA has its own instructions (look for JSSE or OpenSSL sections), but all involve a step that generates a certificate signing request (CSR).

Generating a CSR with keytool

The following command generates the file jetty.csr using keytool for a key/cert already in the keystore:

$ keytool -certreq -alias jetty -keystore keystore -file jetty.csr
Generating a CSR from OpenSSL

The following command generates the file jetty.csr using OpenSSL for a key in the file jetty.key:

$ openssl req -new -key jetty.key -out jetty.csr

Notice that this command uses only the existing key from jetty.key file, and not a certificate in jetty.crt as generated with OpenSSL. You need to enter the details for the certificate again.

Loading Keys and Certificates

Once a CA has sent you a certificate, or if you generated your own certificate without keytool, you need to load it into a JSSE keystore.


You need both the private key and the certificate in the JSSE keystore. You should load the certificate into the keystore used to generate the CSR with keytool. If your key pair is not already in a keystore (for example, because it has been generated with OpenSSL), you need to use the PKCS12 format to load both key and certificate (see PKCKS12 Keys &Certificates).

Loading Certificates with keytool

You can use keytool to load a certificate in PEM form directly into a keystore. The PEM format is a text encoding of certificates; it is produced by OpenSSL, and is returned by some CAs. An example PEM file is:


The following command loads a PEM encoded certificate in the jetty.crt file into a JSSE keystore:

$ keytool -keystore keystore -import -alias jetty -file jetty.crt -trustcacerts

If the certificate you receive from the CA is not in a format that keytool understands, you can use the openssl command to convert formats:

$ openssl x509 -in jetty.der -inform DER -outform PEM -out jetty.crt
Loading Keys and Certificates via PKCS12

If you have a key and certificate in separate files, you need to combine them into a PKCS12 format file to load into a new keystore. The certificate can be one you generated yourself or one returned from a CA in response to your CSR.

The following OpenSSL command combines the keys in jetty.key and the certificate in the jetty.crt file into the jetty.pkcs12 file:

$ openssl pkcs12 -inkey jetty.key -in jetty.crt -export -out jetty.pkcs12

If you have a chain of certificates, because your CA is an intermediary, build the PKCS12 file as follows:

$ cat example.crt intermediate.crt [intermediate2.crt] ... rootCA.crt > cert-chain.txt
$ openssl pkcs12 -export -inkey example.key -in cert-chain.txt -out example.pkcs12


The order of certificates must be from server to rootCA, as per RFC2246 section 7.4.2.

OpenSSL asks for an export password. A non-empty password is required to make the next step work. Load the resulting PKCS12 file into a JSSE keystore with keytool:

$ keytool -importkeystore -srckeystore jetty.pkcs12 -srcstoretype PKCS12 -destkeystore keystore

Renewing Certificates

If you are updating your configuration to use a newer certificate, as when the old one is expiring, just load the newer certificate as described in the section, Loading Keys and Certificates. If you imported the key and certificate originally using the PKCS12 method, use an alias of "1" rather than "jetty", because that is the alias the PKCS12 process enters into the keystore.

Configuring the Jetty SslContextFactory

The generated SSL certificates from above are held in the key store are configured in an instance of SslContextFactory object.

The SslContextFactory is responsible for:

  • Creating the Java SslEngine used by Jetty’s Connectors and Jetty’s Clients (HTTP/1, HTTP/2, and WebSocket).
  • Managing Keystore Access
  • Managing Truststore Access
  • Managing Protocol selection via Excludes / Includes list
  • Managing Cipher Suite selection via Excludes / Includes list
  • Managing order of Ciphers offered (important for TLS/1.2 and HTTP/2 support)
  • SSL Session Caching options
  • Certificate Revocation Lists and Distribution Points (CRLDP)
  • OCSP Support
  • Client Authentication Support

For Jetty Connectors, the configured SslContextFactory is injected into a specific ServerConnector SslConnectionFactory.

For Jetty Clients, the various constructors support using a configured SslContextFactory.

While the SslContextFactory can operate without a keystore (this mode is most suitable for the various Jetty Clients) it is best practice to at least configure the keystore being used.

The configured keystore to use for all SSL/TLS in configured Jetty Connector (or Client).


As a keystore is vital security information, it can be desirable to locate the file in a directory with very restricted access.

The keystore password may be set here in plain text, or as some measure of protection from casual observation, it may be obfuscated using the Password class.
This is used if validating client certificates and is typically set to the same path as the keystore.
The password that is passed to the KeyManagerFactory.init(...). If there is no keymanagerpassword, then the keystorepassword is used instead. If there is no trustmanager set, then the keystore is used as the trust store and the keystorepassword is used as the truststore password.
setExcludeCipherSuites / setIncludeCipherSuites
This allows for the customization of the selected Cipher Suites that will be used by SSL/TLS.
setExcludeProtocols / setIncludeProtocols
This allows for the customization of the selected Protocols that will be used by SSL/TLS.


When working with Includes / Excludes, it is important to know that Excludes will always win. The selection process is to process the JVM list of available Cipher Suites or Protocols against the include list, then remove the excluded ones. Be aware that each Include / Exclude list has a Set method (replace the list) or Add method (append the list).


The key and truststore passwords may also be set using the system properties: org.eclipse.jetty.ssl.keypassword org.eclipse.jetty.ssl.password. This is not a recommended usage.

Configuring SSL in Jetty Distribution

For those of you using the Jetty Distribution, the provided modules for https and http2 will automatically setup the SslContextFactory, the appropriate SslConnectionFactory, and associated ServerConnectors for you in the correct order.

An example of this setup:

$ cd /path/to/mybase
$ java -jar /path/to/jetty-dist/start.jar --add-to-start=https
INFO: ssl             initialised (transitively) in ${jetty.base}/start.ini
INFO: https           initialised in ${jetty.base}/start.ini
INFO: Base directory was modified
$ ls -l
drwxrwxr-x.  2 user group  4096 Feb  2 11:47 etc/
-rw-rw-r--.  1 user group  4259 Feb  2 11:47 start.ini
$ ls -l etc
-rw-rw-r--.  1 user group  3697 Feb  2 11:47 keystore

When you check the start.ini, you’ll see many commented properties ready for you to configure the SslContextFactory basics.

To highlight some of the more commonly used properties:
Configures which interfaces the SSL/TLS Connector should listen on.
Configures which port the SSL/TLS Connector should listen on.
If a webapp needs to redirect to a secure version of the same resource, then this is the port reported back on the response location line (having this be separate is useful if you have something sitting in front of Jetty, such as a Load Balancer or proxy).
Sets the location of the keystore that you configured with your certificates.
Sets the Password for the keystore.

Configuring SNI

From Java 8, the JVM contains support for the Server Name Indicator (SNI) extension, which allows a SSL connection handshake to indicate one or more DNS names that it applies to. To support this, the ExtendedSslContextFactory is used that will look for multiple X509 certificates within the keystore, each of which may have multiple DNS names (including wildcards) associated with the Subject Alternate Name extension. When using the ExtendedSSlContextFactory, the correct certificate is automatically selected if the SNI extension is present in the handshake.

Disabling/Enabling Specific Cipher Suites

As an example, to avoid the BEAST attack it is necessary to configure a specific set of cipher suites. This can either be done via SslContext.setIncludeCipherSuites(java.lang.String…​) or viaSslContext.setExcludeCipherSuites(java.lang.String…​).


It’s crucial that you use the exact names of the cipher suites as used/known by the JDK. You can get them by obtaining an instance of SSLEngine and call getSupportedCipherSuites(). Tools like might report slightly different names which will be ignored.


It’s recommended to install the Java Cryptography Extension (JCE) Unlimited Strength policy files in your JRE to get full strength ciphers such as AES-256. The files can be found on the Java download page. Just overwrite the two present JAR files in <JRE_HOME>/lib/security/.

Both setIncludeCipherSuites and setExcludeCipherSuites can be fed by the exact cipher suite name used in the JDK or by using regular expressions.

If you have a need to adjust the Includes or Excludes, then this is best done with a custom blow-in XML that configures the SslContextFactory to suit your needs.

To do this, first create a new ${jetty.base}/etc/tweak-ssl.xml file (this can be any name, just avoid prefixing it with "jetty-").

<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN"
<!-- Tweak SsslContextFactory Includes / Excludes -->
<Configure id="sslContextFactory" class="org.eclipse.jetty.util.ssl.SslContextFactory">
  <!-- Mitigate SLOTH Attack -->
  <Call name="addExcludeCipherSuites">
      <Array type="String">

This new XML will configure the id sslContextFactory further (this id is first created by the ssl module and its associated ${jetty.home}/etc/jetty-ssl-context.xml). You can do anything you want with the SslContextFactory in use by the Jetty Distribution from this tweaked XML.

To make sure that your ${jetty.base} uses this new XML, add it to the end of your ${jetty.base}/start.ini or ${jetty.base}/start.d/server.ini.

$ cd /path/to/mybase
$ ls -l
drwxrwxr-x.  2 user group  4096 Feb  2 11:47 etc/
-rw-rw-r--.  1 user group  4259 Feb  2 11:47 start.ini
$ tail start.ini
# Module: https


The default SslContextFactory implementation applies the latest SSL/TLS recommendations surrounding vulnerabilities in SSL/TLS. Check the release notes (the VERSION.txt found in the root of the Jetty Distribution, or the alternate (classified version) artifacts for the jetty-project componenton Maven Central) for updates. The Java JVM is also applying exclusions at the JVM level and as such if you have a need to enable something that is generally accepted by the industry as being insecure or vulnerable you will likely have to enable it in BOTH the Java JVM and the Jetty configuration.


You can enable the org.eclipse.jetty.util.ssl named logger at DEBUG level to see what the list of selected Protocols and Cipher suites are at startup of Jetty.

Additional Include / Exclude examples:

Example: Include all ciphers which support Forward Secrecy using regex:

  <!-- Enable Forward Secrecy Ciphers.
       Note: this replaces the default Include Cipher list -->
  <Set name="IncludeCipherSuites">
    <Array type="String">

Example: Exclude all old, insecure or anonymous cipher suites:

  <!-- Eliminate Old / Insecure / Anonymous Ciphers -->
  <Call name="addExcludeCipherSuites">
      <Array type="String">

Example: Since 2014 SSLv3 is considered insecure and should be disabled.

  <!-- Eliminate Insecure Protocols -->
  <Call name="addExcludeProtocols">
     <Array type="java.lang.String">


Note that disabling SSLv3 prevents very old browsers like Internet Explorer 6 on Windows XP from connecting.

Example: TLS renegotiation could be disabled too to prevent an attack based on this feature.

  <Set name="renegotiationAllowed">FALSE</Set>

See an error or something missing? Contribute to this documentation at Github!(Generated: 2016-09-15)