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TLS/SSL

You cannot use TLS/SSL when Symmetric Encryption is enabled. Also note that the symmetric encryption feature has been deprecated.

You can use the SSL (Secure Sockets Layer) protocol to establish an encrypted communication across your Hazelcast cluster with key stores and trust stores. Note that, if you are developing applications using Java 8, you will be using its successor TLS (Transport Layer Security).

It is NOT recommended to reuse the key stores and trust stores for external applications.

TLS/SSL for Hazelcast Members

Hazelcast allows you to encrypt socket level communication between Hazelcast members and between Hazelcast clients and members, for end to end encryption. To use it, you need to implement com.hazelcast.nio.ssl.SSLContextFactory and configure the SSL section in the network configuration.

The following is the implementation code snippet:

public class MySSLContextFactory implements SSLContextFactory {
    public void init( Properties properties ) throws Exception {
    }

    public SSLContext getSSLContext() {
        ...
        SSLContext sslCtx = SSLContext.getInstance( "the protocol to be used" );
        return sslCtx;
    }
}

The following is the base declarative configuration for the implemented SSLContextFactory:

  • XML

  • YAML

<hazelcast>
    ...
    <network>
        <ssl enabled="true">
            <factory-class-name>
                com.hazelcast.examples.MySSLContextFactory
            </factory-class-name>
            <properties>
                <property name="foo">bar</property>
            </properties>
        </ssl>
    </network>
    ...
</hazelcast>
hazelcast:
  network:
    ssl:
      enabled: true
      factory-class-name: com.hazelcast.examples.MySSLContextFactory
      properties:
        foo: bar

Hazelcast provides a default SSLContextFactory, com.hazelcast.nio.ssl.BasicSSLContextFactory, which uses the configured keystore to initialize SSLContext; see the following example configuration for TLS/SSL.

  • XML

  • YAML

<hazelcast>
    ...
    <network>
        <ssl enabled="true">
            <factory-class-name>
                com.hazelcast.nio.ssl.BasicSSLContextFactory
            </factory-class-name>
            <properties>
                <property name="protocol">TLSv1.2</property>
                <property name="mutualAuthentication">REQUIRED</property>
                <property name="keyStore">/opt/hazelcast-keystore.p12</property>
                <property name="keyStorePassword">secret.123</property>
                <property name="keyStoreType">PKCS12</property>
                <property name="trustStore">/opt/hazelcast-truststore.p12</property>
                <property name="trustStorePassword">changeit</property>
                <property name="trustStoreType">PKCS12</property>
            </properties>
        </ssl>
    </network>
    ...
</hazelcast>
hazelcast:
  network:
    ssl:
      enabled: true
      factory-class-name: com.hazelcast.nio.ssl.BasicSSLContextFactory
      properties:
        protocol: TLSv1.2
        mutualAuthentication: REQUIRED
        keyStore: /opt/hazelcast-keystore.p12
        keyStorePassword: secret.123
        keyStoreType: PKCS12
        trustStore: /opt/hazelcast-truststore.p12
        trustStorePassword: changeit
        trustStoreType: PKCS12

The following are the descriptions of the properties:

  • keyStore: Path of your keystore file.

  • keyStorePassword: Password to access the key from your keystore file.

  • keyManagerAlgorithm: Name of the algorithm based on which the authentication keys are provided.

  • keyStoreType: Type of the keystore. Its default value is JKS. Another commonly used type is the PKCS12. Available keystore/truststore types depend on your Operating system and the Java runtime.

  • trustStore: Path of your truststore file. The file truststore is a keystore file that contains a collection of certificates trusted by your application.

  • trustStorePassword: Password to unlock the truststore file.

  • trustManagerAlgorithm: Name of the algorithm based on which the trust managers are provided.

  • trustStoreType: Type of the truststore. Its default value is JKS. Another commonly used type is the PKCS12. Available keystore/truststore types depend on your Operating system and the Java runtime.

  • mutualAuthentication: Mutual authentication configuration. It’s empty by default which means the client side of connection is not authenticated. Available values are:

    • REQUIRED - server forces usage of a trusted client certificate

    • OPTIONAL - server asks for a client certificate, but it doesn’t require it

  • ciphersuites: Comma-separated list of cipher suite names allowed to be used. Its default value are all supported suites in your Java runtime.

  • protocol: Name of the algorithm which is used in your TLS/SSL. Its default value is TLS. Available values are:

    • TLS

    • TLSv1

    • TLSv1.1

    • TLSv1.2

    • TLSv1.3

      For the protocol property, we recommend you to provide TLS with its version information, e.g., TLSv1.2. Note that if you write only TLS, your application chooses the TLS version according to your Java version.

  • validateIdentity: Flag which allows enabling endpoint identity validation. It means, during the TLS handshake client verifies if the server’s hostname (or IP address) matches the information in X.509 certificate (Subject Alternative Name extension). Possible values are "true" and "false" (default).

TLS/SSL for Hazelcast Clients

The TLS configuration in Hazelcast clients is very similar to member configuration.

  • XML

  • YAML

<hazelcast-client>
    ...
    <network>
        <ssl enabled="true">
            <factory-class-name>
                com.hazelcast.nio.ssl.BasicSSLContextFactory
            </factory-class-name>
            <properties>
                <property name="protocol">TLSv1.2</property>
                <property name="trustStore">/opt/hazelcast-client.truststore</property>
                <property name="trustStorePassword">changeit</property>
                <property name="trustStoreType">JKS</property>

                <!-- Following properties are only needed when the mutual authentication is used. -->
                <property name="keyStore">/opt/hazelcast-client.keystore</property>
                <property name="keyStorePassword">clientsSecret</property>
                <property name="keyStoreType">JKS</property>
            </properties>
        </ssl>
    </network>
    ...
</hazelcast-client>
hazelcast-client:
  network:
    ssl:
      enabled: true
      factory-class-name: com.hazelcast.nio.ssl.BasicSSLContextFactory
      properties:
        protocol: TLSv1.2

        trustStore: /opt/hazelcast-client.truststore
        trustStorePassword: changeit
        trustStoreType: JKS

        # Following properties are only needed when the mutual authentication is used.
        keyStore: /opt/hazelcast-client.keystore
        keyStorePassword: clientsSecret
        keyStoreType: JKS

The same BasicSSLContextFactory properties used for members are available on clients. Clients don’t need to set mutualAuthentication property as it’s used in configuring the server side of TLS connections.

Mutual Authentication

TLS connections have two sides: the one opening the connection (TLS client) and the one accepting the connection (TLS server). By default only the TLS server proves its identity by presenting a certificate to the TLS client. The mutual authentication means that also the TLS clients prove their identity to the TLS servers.

Hazelcast members can be on both sides of TLS connection - TLS servers and TLS clients. Hazelcast clients are always on the client side of a TLS connection.

By default Hazelcast members have keyStore used to identify themselves to the clients and other members. Both Hazelcast members and Hazelcast clients have trustStore used to define which members they can trust.

When the mutual authentication feature is enabled, Hazelcast clients need to provide keyStore. A client proves its identity by providing its certificate to the Hazelcast member it’s connecting to. The member only accepts the connection if the client’s certificate is present in the member’s trustStore.

To enable the mutual authentication, set the mutualAuthentication property value to REQUIRED on the member side, as shown below:

Config cfg = new Config();
Properties props = new Properties();

props.setProperty("mutualAuthentication", "REQUIRED");
props.setProperty("keyStore", "/opt/hazelcast.keystore");
props.setProperty("keyStorePassword", "123456");
props.setProperty("trustStore", "/opt/hazelcast.truststore");
props.setProperty("trustStorePassword", "123456");

cfg.getNetworkConfig().setSSLConfig(new SSLConfig().setEnabled(true).setProperties(props));
Hazelcast.newHazelcastInstance(cfg);

And on the client side, you need to set client identity by providing the keystore:

clientSslProps.setProperty("keyStore", "/opt/client.keystore");
clientSslProps.setProperty("keyStorePassword", "123456");

The property mutualAuthentication has the following options:

  • REQUIRED: Server asks for client certificate. If the client does not provide a keystore or the provided keystore is not verified against member’s truststore, the client is not authenticated.

  • OPTIONAL: Server asks for client certificate, but client is not required to provide any valid certificate.

When a new client is introduced with a new keystore, the truststore on the member side should be updated accordingly to include new clients' information to be able to accept it.

See the below example snippet to see the full configuration on the client side:

ClientConfig config = new ClientConfig();
Properties clientSslProps = new Properties();
clientSslProps.setProperty("keyStore", "/opt/client.keystore");
clientSslProps.setProperty("keyStorePassword", "123456");
clientSslProps.setProperty("trustStore", "/opt/client.truststore");
clientSslProps.setProperty("trustStorePassword", "123456");

config.getNetworkConfig().setSSLConfig(new SSLConfig().setEnabled(true).setProperties(clientSslProps));
HazelcastClient.newHazelcastClient(config);

If the mutual authentication is not required, the Hazelcast members accept all incoming TLS connections without verifying if the connecting side is trusted. Therefore it’s recommended to require the mutual authentication in Hazelcast members configuration.

TLS/SSL for WAN Replication

Hazelcast allows you to secure the communications between the WAN replicated clusters using TLS/SSL. WAN connections, cluster members and clients can have their own unique TLS/SSL certificates. You can also choose to have TLS/SSL configured on some of the members/clients and not on the others.

You can configure TLS/SSL for WAN replication using the advanced network configuration. See the Securing the Connections for WAN Replication section for the details.

TLS/SSL Performance Improvements for Java

TLS/SSL can have a significant impact on performance. There are a few ways to increase the performance.

The first thing that can be done is making sure that AES intrinsics are used. Modern CPUs (2010 or newer Westmere) have hardware support for AES encryption/decryption and if a Java 8 or newer JVM is used, the JIT automatically makes use of these AES intrinsics. They can also be explicitly enabled using -XX:+UseAES -XX:+UseAESIntrinsics, or disabled using -XX:-UseAES -XX:-UseAESIntrinsics.

A lot of encryption algorithms make use of padding because they encrypt/decrypt in fixed sized blocks. If there is no enough data for a block, the algorithm relies on random number generation to pad. Under Linux, the JVM automatically makes use of /dev/random for the generation of random numbers. /dev/random relies on entropy to be able to generate random numbers. However, if this entropy is insufficient to keep up with the rate requiring random numbers, it can slow down the encryption/decryption since /dev/random will block; it could block for minutes waiting for sufficient entropy . This can be fixed by setting the -Djava.security.egd=file:/dev/./urandom system property. For a more permanent solution, modify the <JAVA_HOME>/jre/lib/security/java.security file, look for the securerandom.source=/dev/urandom and change it to securerandom.source=file:/dev/./urandom. Switching to /dev/urandom could be controversial because /dev/urandom will not block if there is a shortage of entropy and the returned random values could theoretically be vulnerable to a cryptographic attack. If this is a concern in your application, use /dev/random instead.

Hazelcast’s Java smart client automatically makes use of extra I/O threads for encryption/decryption and this have a significant impact on the performance. This can be changed using the hazelcast.client.io.input.thread.count and hazelcast.client.io.output.thread.count client system properties. By default it is 1 input thread and 1 output thread. If TLS/SSL is enabled, it defaults to 3 input threads and 3 output threads. Having more client I/O threads than members in the cluster does not lead to an increased performance. So with a 2-member cluster, 2 in and 2 out threads give the best performance.