SSH tunnel connections

Materialize can connect to data sources like Kafka, Confluent, and PostgreSQL with a secure SSH bastion host. In this guide, you will create an SSH tunnel connection, configure your Materialize authentication settings, and create a source connection.

Before you begin

Before you begin, make sure you have access to a bastion host. You will need:

The bastion host IP address and port number
The bastion host username

Create an SSH tunnel connection

In Materialize, create an SSH tunnel connection to the bastion host:

CREATE CONNECTION ssh_connection TO SSH TUNNEL (
    HOST '<SSH_BASTION_HOST>',
    USER '<SSH_BASTION_USER>',
    PORT <SSH_BASTION_PORT>
);

Configure the SSH bastion host

The bastion host needs a public key to connect to the Materialize tunnel you created in the previous step.

Materialize stores public keys for SSH tunnels in the system catalog. Query mz_ssh_tunnel_connections to retrieve the public keys for the SSH tunnel connection you just created:

SELECT
    mz_connections.name,
    mz_ssh_tunnel_connections.*
FROM
    mz_connections JOIN
    mz_ssh_tunnel_connections USING(id)
WHERE
    mz_connections.name = 'ssh_connection';

| id    | public_key_1                          | public_key_2                          |
|-------|---------------------------------------|---------------------------------------|
| u75   | ssh-ed25519 AAAA...76RH materialize   | ssh-ed25519 AAAA...hLYV materialize   |

Materialize provides two public keys to allow you to rotate keys without connection downtime. Review the ALTER CONNECTION documentation for more information on how to rotate your keys.

# Command for Linux
echo "ssh-ed25519 AAAA...76RH materialize" >> ~/.ssh/authorized_keys
echo "ssh-ed25519 AAAA...hLYV materialize" >> ~/.ssh/authorized_keys

Configure your internal firewall to allow the SSH bastion host to connect to your Kafka cluster or PostgreSQL instance.

If you are using a cloud provider like AWS or GCP, update the security group or firewall rules for your PostgreSQL instance or Kafka brokers.

Allow incoming traffic from the SSH bastion host IP address on the necessary ports.

For example, use port 5432 for PostgreSQL and ports 9092, 9094, and 9096 for Kafka.

Test the connection from the bastion host to the Kafka cluster or PostgreSQL instance.
```
telnet <KAFKA_BROKER_HOST> <KAFKA_BROKER_PORT>
telnet <POSTGRES_HOST> <POSTGRES_PORT>
```
If the command hangs, double-check your security group and firewall settings. If the connection is successful, you can proceed to the next step.
Verify the SSH tunnel connection from your source to your bastion host:
```
# Command for Linux
ssh -L 9092:kafka-broker:9092 <SSH_BASTION_USER>@<SSH_BASTION_HOST>
```
Verify that you can connect to the Kafka broker or PostgreSQL instance via the SSH tunnel:
```
telnet localhost 9092
```
If you are unable to connect using the telnet command, enable AllowTcpForwarding and PermitTunnel on your bastion host SSH configuration file.

On your SSH bastion host, open the SSH config file (usually located at /etc/ssh/sshd_config) using a text editor:
```
sudo nano /etc/ssh/sshd_config
```
Add or uncomment the following lines:
```
AllowTcpForwarding yes
PermitTunnel yes
```
Save the changes and restart the SSH service:
```
sudo systemctl restart sshd
```
Retrieve the static egress IPs from Materialize and configure the firewall rules (e.g. AWS Security Groups) for your bastion host to allow SSH traffic for those IP addresses only.
```
SELECT * FROM mz_catalog.mz_egress_ips;
```
```
XXX.140.90.33
XXX.198.159.213
XXX.100.27.23
```

Validate the SSH tunnel connection

To confirm that the SSH tunnel connection is correctly configured, use the VALIDATE CONNECTION command:

VALIDATE CONNECTION ssh_connection;

If no validation errors are returned, the connection can be used to create a source connection.

Create a source connection

In Materialize, create a source connection that uses the SSH tunnel connection you configured in the previous section:

CREATE CONNECTION kafka_connection TO KAFKA (
    BROKER 'broker1:9092',
    SSH TUNNEL ssh_connection
);

You can reuse this Kafka connection across multiple CREATE SOURCE statements:

CREATE SOURCE json_source
  FROM KAFKA CONNECTION kafka_connection (TOPIC 'test_topic')
  FORMAT JSON;

CREATE SECRET pgpass AS '<POSTGRES_PASSWORD>';

CREATE CONNECTION pg_connection TO POSTGRES (
  HOST 'instance.foo000.us-west-1.rds.amazonaws.com',
  PORT 5432,
  USER 'postgres',
  PASSWORD SECRET pgpass,
  SSL MODE 'require',
  DATABASE 'postgres'
  SSH TUNNEL ssh_connection
);

You can reuse this PostgreSQL connection across multiple CREATE SOURCE statements:

CREATE SOURCE mz_source
  FROM POSTGRES CONNECTION pg_connection (PUBLICATION 'mz_source')
  FOR ALL TABLES;

CREATE SECRET mysqlpass AS '<POSTGRES_PASSWORD>';

    CREATE CONNECTION mysql_connection TO MYSQL (
    HOST '<host>',
    SSH TUNNEL ssh_connection,
    );

You can reuse this MySQL connection across multiple CREATE SOURCE statements:

    CREATE SOURCE mz_source
      FROM mysql CONNECTION mysql_connection
      FOR ALL TABLES;