Skip to content

Encrypt PXC traffic

There are two kinds of traffic in Percona XtraDB Cluster:

  1. Client-server traffic (the one between client applications and cluster nodes),

  2. Replication traffic, that includes SST, IST, write-set replication, and various service messages.

Percona XtraDB Cluster supports encryption for all types of traffic. Replication traffic encryption can be configured either automatically or manually.

Encrypt client-server communication

Percona XtraDB Cluster uses the underlying MySQL encryption mechanism to secure communication between client applications and cluster nodes.

MySQL generates default key and certificate files and places them in the data directory. You can override auto-generated files with manually created ones, as described in the section Generate keys and certificates manually.

The auto-generated files are suitable for automatic SSL configuration, but you should use the same key and certificate files on all nodes.

Specify the following settings in the my.cnf configuration file for each node:



After it is restarted, the node uses these files to encrypt communication with clients. MySQL clients require only the second part of the configuration to communicate with cluster nodes.

MySQL generates the default key and certificate files and places them in the data directory. You can either use them or generate new certificates. For generation of new certificate please refer to Generate keys and certificates manually section.

Encrypt replication traffic

Replication traffic refers to the inter-node traffic which includes the SST traffic, IST traffic, and replication traffic.

The traffic of each type is transferred via a different channel, and so it is important to configure secure channels for all 3 variants to completely secure the replication traffic.

Percona XtraDB Cluster supports a single configuration option which helps to secure the complete replication traffic, and is often referred to as SSL automatic configuration. You can also configure the security of each channel by specifying independent parameters.

SSL automatic configuration

The automatic configuration of the SSL encryption needs a key and certificate files. MySQL generates a default key and certificate files and places them in the data directory.


It is important that your cluster use the same SSL certificates on all nodes.

Enable pxc-encrypt-cluster-traffic

Percona XtraDB Cluster includes the pxc-encrypt-cluster-traffic variable that enables automatic configuration of SSL encryption there-by encrypting SST, IST, and replication traffic.

By default, pxc-encrypt-cluster-traffic is enabled thereby using a secured channel for replication. This variable is not dynamic and so it cannot be changed at runtime.

Enabled, pxc-encrypt-cluster-traffic has the effect of applying the following settings: encrypt, ssl_key, ssl-ca, ssl-cert.

Setting pxc-encrypt-cluster-traffic=ON has the effect of applying the following settings in the my.cnf configuration file:



For wsrep_provider_options, only the mentioned options are affected (socket.ssl_key, socket,ssl_cert, and socket.ssl_ca), the rest is not modified.


Disabling pxc-encrypt-cluster-traffic

The default value of pxc-encrypt-cluster-traffic helps improve the security of your system.

When pxc-encrypt-cluster-traffic is not enabled, anyone with the access to your network can connect to any PXC node either as a client or as another node joining the cluster. This potentially lets them query your data or get a complete copy of it.

If you must disable pxc-encrypt-cluster-traffic, you need to stop the cluster and update [mysqld] section of the configuration file: pxc-encrypt-cluster-traffic=OFF of each node. Then, restart the cluster.

The automatic configuration of the SSL encryption needs key and certificate files. MySQL generates default key and certificate files and places them in data directory. These auto-generated files are suitable for automatic SSL configuration, but you should use the same key and certificate files on all nodes. Also you can override auto-generated files with manually created ones, as covered in Generate keys and certificates manually.

The necessary key and certificate files are first searched at the ssl-ca, ssl-cert, and ssl-key options under [mysqld]. If these options are not set, the data directory is searched for ca.pem, server-cert.pem, and server-key.pem files.


The [sst] section is not searched.

If all three files are found, they are used to configure encryption. If any of the files is missing, a fatal error is generated.

SSL manual configuration

If user wants to enable encryption for specific channel only or use different certificates or other mix-match, then user can opt for manual configuration. This helps to provide more flexibility to end-users.

To enable encryption manually, the location of the required key and certificate files shoud be specified in the Percona XtraDB Cluster configuration. If you do not have the necessary files, see Generate keys and certificates manually.


Encryption settings are not dynamic. To enable it on a running cluster, you need to restart the entire cluster.

There are three aspects of Percona XtraDB Cluster operation, where you can enable encryption:

Encrypt SST traffic

This refers to full data transfer that usually occurs when a new node (JOINER) joins the cluster and receives data from an existing node (DONOR).

For more information, see State snapshot transfer.


If keyring_file plugin is used, then SST encryption is mandatory: when copying encrypted data via SST, the keyring must be sent over with the files for decryption. In this case following options are to be set in my.cnf on all nodes:

The cluster will not work if keyring configuration across nodes is different.

The only available SST method is xtrabackup-v2 which uses Percona XtraBackup.


This is the only available SST method (the wsrep_sst_method is always set to xtrabackup-v2), which uses Percona XtraBackup to perform non-blocking transfer of files. For more information, see Percona XtraBackup SST Configuration.

Encryption mode for this method is selected using the encrypt option:

  • encrypt=0 is the default value, meaning that encryption is disabled.

  • encrypt=4 enables encryption based on key and certificate files generated with OpenSSL. For more information, see Generating Keys and Certificates Manually.

To enable encryption for SST using XtraBackup, specify the location of the keys and certificate files in the each node’s configuration under [sst]:



SSL clients require DH parameters to be at least 1024 bits, due to the logjam vulnerability. However, versions of socat earlier than 1.7.3 use 512-bit parameters. If a dhparams.pem file of required length is not found during SST in the data directory, it is generated with 2048 bits, which can take several minutes. To avoid this delay, create the dhparams.pem file manually and place it in the data directory before joining the node to the cluster:

$ openssl dhparam -out /path/to/datadir/dhparams.pem 2048

For more information, see this blog post.

Encrypt replication/IST traffic

Replication traffic refers to the following:

  • Write-set replication which is the main workload of Percona XtraDB Cluster (replicating transactions that execute on one node to all other nodes).

  • Incremental State Transfer (IST) which is copying only missing transactions from DONOR to JOINER node.

  • Service messages which ensure that all nodes are synchronized.

All this traffic is transferred via the same underlying communication channel (gcomm). Securing this channel will ensure that IST traffic, write-set replication, and service messages are encrypted. (For IST, a separate channel is configured using the same configuration parameters, so 2 sections are described together).

To enable encryption for all these processes, define the paths to the key, certificate and certificate authority files using the following wsrep provider options:

To set these options, use the wsrep_provider_options variable in the configuration file:

$ wsrep_provider_options="socket.ssl=yes;socket.ssl_ca=/etc/mysql/certs/ca.pem;socket.ssl_cert=/etc/mysql/certs/server-cert.pem;socket.ssl_key=/etc/mysql/certs/server-key.pem"


You must use the same key and certificate files on all nodes, preferably those used for Encrypt client-server communication.

Check upgrade-certificate section on how to upgrade existing certificates.

Generate keys and certificates manually

As mentioned above, MySQL generates default key and certificate files and places them in the data directory. If you want to override these certificates, the following new sets of files can be generated:

  • Certificate Authority (CA) key and certificate to sign the server and client certificates.

  • Server key and certificate to secure database server activity and write-set replication traffic.

  • Client key and certificate to secure client communication traffic.

These files should be generated using OpenSSL.


The Common Name value used for the server and client keys and certificates must differ from that value used for the CA certificate.

The Certificate Authority is used to verify the signature on certificates.

  1. Generate the CA key file:

    $ openssl genrsa 2048 > ca-key.pem
  2. Generate the CA certificate file:

    $ openssl req -new -x509 -nodes -days 3600
        -key ca-key.pem -out ca.pem
  1. Generate the server key file:

    $ openssl req -newkey rsa:2048 -days 3600 \
        -nodes -keyout server-key.pem -out server-req.pem
  2. Remove the passphrase:

    $ openssl rsa -in server-key.pem -out server-key.pem
  3. Generate the server certificate file:

    $ openssl x509 -req -in server-req.pem -days 3600 \
        -CA ca.pem -CAkey ca-key.pem -set_serial 01 \
        -out server-cert.pem
  1. Generate the client key file:

    $ openssl req -newkey rsa:2048 -days 3600 \
        -nodes -keyout client-key.pem -out client-req.pem
  2. Remove the passphrase:

    $ openssl rsa -in client-key.pem -out client-key.pem
  3. Generate the client certificate file:

    $ openssl x509 -req -in client-req.pem -days 3600 \
       -CA ca.pem -CAkey ca-key.pem -set_serial 01 \
       -out client-cert.pem

Verify certificates

To verify that the server and client certificates are correctly signed by the CA certificate, run the following command:

$ openssl verify -CAfile ca.pem server-cert.pem client-cert.pem

If the verification is successful, you should see the following output:

server-cert.pem: OK
client-cert.pem: OK

Failed validation caused by matching CN

Sometimes, an SSL configuration may fail if the certificate and the CA files contain the same .

To check if this is the case run openssl command as follows and verify that the CN field differs for the Subject and Issuer lines.

$ openssl x509 -in server-cert.pem -text -noout

Incorrect values

Version: 1 (0x0)
Serial Number: 1 (0x1)
Signature Algorithm: sha256WithRSAEncryption
Issuer:, O=Database Performance., C=US
Subject:, O=Database Performance., C=AU

To obtain a more compact output run openssl specifying -subject and -issuer parameters:

$ openssl x509 -in server-cert.pem -subject -issuer -noout
Expected output
subject= / Performance./C=AU
issuer= / Performance./C=US

Deploy keys and certificates

Use a secure method (for example, scp or sftp) to send the key and certificate files to each node. Place them under the /etc/mysql/certs/ directory or similar location where you can find them later.


Make sure that this directory is protected with proper permissions. Most likely, you only want to give read permissions to the user running mysqld.

The following files are required:

  • Certificate Authority certificate file (ca.pem)

This file is used to verify signatures.

  • Server key and certificate files (server-key.pem and server-cert.pem)

These files are used to secure database server activity and write-set replication traffic.

  • Client key and certificate files (client-key.pem and client-cert.pem)

These files are required only if the node should act as a MySQL client. For example, if you are planning to perform SST using mysqldump.


Upgrade certificates subsection covers the details on upgrading certificates, if necessary.

Upgrade certificates

The following procedure shows how to upgrade certificates used for securing replication traffic when there are two nodes in the cluster.

  1. Restart the first node with the socket.ssl_ca option set to a combination of the the old and new certificates in a single file.

    For example, you can merge contents of old-ca.pem and new-ca.pem into upgrade-ca.pem as follows:

    $ cat old-ca.pem > upgrade-ca.pem && \
    cat new-ca.pem >> upgrade-ca.pem

    Set the wsrep_provider_options variable as follows:

    $ wsrep_provider_options="socket.ssl=yes;socket.ssl_ca=/etc/mysql/certs/upgrade-ca.pem;socket.ssl_cert=/etc/mysql/certs/old-cert.pem;socket.ssl_key=/etc/mysql/certs/old-key.pem"
  2. Restart the second node with the socket.ssl_ca, socket.ssl_cert, and socket.ssl_key options set to the corresponding new certificate files.

    $ wsrep_provider_options="socket.ssl=yes;socket.ssl_ca=/etc/mysql/certs/new-ca.pem;socket.ssl_cert=/etc/mysql/certs/new-cert.pem;socket.ssl_key=/etc/mysql/certs/new-key.pem"
  3. Restart the first node with the new certificate files, as in the previous step.

  4. You can remove the old certificate files.

Get expert help

If you need assistance, visit the community forum for comprehensive and free database knowledge, or contact our Percona Database Experts for professional support and services.

Last update: 2024-03-14