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Migrate remote clusters from certificate to API key authentication

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Migrate remote clusters from certificate to API key authentication

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The API key based security model for remote clusters offers administrators more fine-grained access controls compared to the TLS certificate based security model. For that reason, you may want to migrate from the certificate based security model to the API key based model.

While it is possible to migrate by defining a new remote cluster connection, using a new alias, this has several downsides:

For cross-cluster replication, it’s not possible to change the leader cluster alias for existing tasks. As a result, with a new remote cluster, follower indices would need to be re-created from scratch.
For cross-cluster search, transform and anomaly detection jobs do allow updating the remote cluster alias. However, if the job was created with wildcards, for example *:source_index, and superuser, adding a new remote cluster will cause the job to do double the amount of work and potentially skew results with duplications.

For these reasons, you may prefer to migrate a remote cluster in-place, by following these steps:

If you run into any issues, refer to Troubleshooting.

Prerequisites

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The nodes of the local and remote clusters must be on version 8.10 or later.
The local and remote clusters must have an appropriate license. For more information, refer to https://www.elastic.co/subscriptions.

Reconfigure the remote cluster and generate a cross-cluster API key

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On the remote cluster:

Enable the remote cluster server on every node of the remote cluster. In elasticsearch.yml:
1. Set remote_cluster_server.enabled to true.
2. Configure the bind and publish address for remote cluster server traffic, for example using remote_cluster.host. Without configuring the address, remote cluster traffic may be bound to the local interface, and remote clusters running on other machines can’t connect.
3. Optionally, configure the remote server port using remote_cluster.port (defaults to 9443).
Next, generate a certificate authority (CA) and a server certificate/key pair. On one of the nodes of the remote cluster, from the directory where Elasticsearch has been installed:
1. Create a CA, if you don’t have a CA already:
```
./bin/elasticsearch-certutil ca --pem --out=cross-cluster-ca.zip --pass CA_PASSWORD
```
  Replace CA_PASSWORD with the password you want to use for the CA. You can remove the --pass option and its argument if you are not deploying to a production environment.
2. Unzip the generated cross-cluster-ca.zip file. This compressed file contains the following content:
```
/ca
|_ ca.crt
|_ ca.key
```
3. Generate a certificate and private key pair for the nodes in the remote cluster:
```
./bin/elasticsearch-certutil cert --out=cross-cluster.p12 --pass=CERT_PASSWORD --ca-cert=ca/ca.crt --ca-key=ca/ca.key --ca-pass=CA_PASSWORD --dns=example.com --ip=127.0.0.1
```
  - Replace CA_PASSWORD with the CA password from the previous step.
  - Replace CERT_PASSWORD with the password you want to use for the generated private key.
  - Use the --dns option to specify the relevant DNS name for the certificate. You can specify it multiple times for multiple DNS.
  - Use the --ip option to specify the relevant IP address for the certificate. You can specify it multiple times for multiple IP addresses.
4. If the remote cluster has multiple nodes, you can either:
  - create a single wildcard certificate for all nodes;
  - or, create separate certificates for each node either manually or in batch with the silent mode.
On every node of the remote cluster:
1. Copy the cross-cluster.p12 file from the earlier step to the config directory. If you didn’t create a wildcard certificate, make sure you copy the correct node-specific p12 file.
2. Add following configuration to elasticsearch.yml:
```
xpack.security.remote_cluster_server.ssl.enabled: true
xpack.security.remote_cluster_server.ssl.keystore.path: cross-cluster.p12
```
3. Add the SSL keystore password to the Elasticsearch keystore:
```
./bin/elasticsearch-keystore add xpack.security.remote_cluster_server.ssl.keystore.secure_password
```
  When prompted, enter the CERT_PASSWORD from the earlier step.
Restart the remote cluster.
On the remote cluster, generate a cross-cluster API key that provides access to the indices you want to use for cross-cluster search or cross-cluster replication. You can use the Create Cross-Cluster API key API or Kibana.
Copy the encoded key (encoded in the response) to a safe location. You will need it to connect to the remote cluster later.

Stop cross-cluster operations

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On the local cluster, stop any persistent tasks that refer to the remote cluster:

Use the Stop transforms API to stop any transforms.
Use the Close jobs API to close any anomaly detection jobs.
Use the Pause auto-follow pattern API to pause any auto-follow cross-cluster replication.
Use the Pause follower API to pause any manual cross-cluster replication or existing indices that were created from the auto-follow pattern.

Reconnect to the remote cluster

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On the local cluster:

Enhance any roles used by local cluster users with the required remote indices privileges for cross-cluster replication and cross-cluster search. Refer to Configure roles and users. Note:
- You only need to assign additional remote_indices privileges to existing roles used for cross-cluster operations. You should be able to copy these privileges from the original roles on the remote cluster, where they are defined under the certification based security model.
- The roles on the local cluster can’t exceed the access privilege granted by the cross-cluster API key. Any extra local privileges will be suppressed by the cross-cluster API key’s privileges.
- No update is needed if the cross-cluster replication or cross-cluster search tasks have been configured with a superuser role. The superuser role is automatically updated to allow access to all remote indices.
- Tasks that are run as regular users with named roles are immediately updated with the new privileges. A task will load a new definition the next time it runs.
- You need to restart tasks that are run using an API key (done in a later step).
If you’ve dynamically configured the remote cluster (via the cluster settings API):
1. Retrieve the current remote cluster configuration, and store it in a safe place. You may need it later in case you need to roll back. Use the cluster settings API:
```
response = client.cluster.get_settings(
  filter_path: 'persistent.cluster.remote'
)
puts response
```
```
GET /_cluster/settings?filter_path=persistent.cluster.remote
```
2. Remove the existing remote cluster definition by setting the remote cluster settings to null.
If you’ve statically configured the remote cluster (via elasticsearch.yml), copy the cluster.remote settings from elasticsearch.yml, and store them in a safe place. You may need them later in case you need to roll back.
On every node of the local cluster:
1. Copy the ca.crt file generated on the remote cluster earlier into the config directory, renaming the file remote-cluster-ca.crt.
2. Add following configuration to elasticsearch.yml:
```
xpack.security.remote_cluster_client.ssl.enabled: true
xpack.security.remote_cluster_client.ssl.certificate_authorities: [ "remote-cluster-ca.crt" ]
```
3. Add the cross-cluster API key, created on the remote cluster earlier, to the keystore:
```
./bin/elasticsearch-keystore add cluster.remote.ALIAS.credentials
```
  Replace ALIAS with the same alias that was used for cross-cluster operations before the migration. When prompted, enter the encoded cross-cluster API key created on the remote cluster earlier.

If you’ve dynamically configured the remote cluster (via the cluster settings API):

Restart the local cluster to load changes to the keystore and settings.

Re-add the remote cluster. Use the same remote cluster alias, and change the transport port into the remote cluster port. For example:

response = client.cluster.put_settings(
  body: {
    persistent: {
      cluster: {
        remote: {
          my_remote: {
            mode: 'proxy',
            proxy_address: 'my.remote.cluster.com:9443'
          }
        }
      }
    }
  }
)
puts response

PUT /_cluster/settings
{
  "persistent" : {
    "cluster" : {
      "remote" : {
        "my_remote" : { 
          "mode": "proxy",
          "proxy_address": "my.remote.cluster.com:9443" 
        }
      }
    }
  }
}

	The remote cluster alias. Use the same alias that was used before the migration.
	The remote cluster address with the remote cluster port, which defaults to `9443`.

If you’ve statically configured the remote cluster (via elasticsearch.yml):
1. Update the cluster.remote settings in elasticsearch.yml on each node of the local cluster. Change the port into the remote cluster port, which defaults to 9443.
2. Restart the local cluster to load changes to the keystore and settings.

Use the remote cluster info API to verify that the local cluster has successfully connected to the remote cluster:

response = client.cluster.remote_info
puts response

GET /_remote/info

The API response should indicate that the local cluster has connected to the remote cluster:

{
  "my_remote": {
    "connected": true, 
    "mode": "proxy",
    "proxy_address": "my.remote.cluster.com:9443",
    "server_name": "",
    "num_proxy_sockets_connected": 0,
    "max_proxy_socket_connections": 18,
    "initial_connect_timeout": "30s",
    "skip_unavailable": false,
    "cluster_credentials": "::es_redacted::" 
  }
}

	The remote cluster is connected.
	If present, indicates the remote cluster has connected using API key authentication.

Resume cross-cluster operations

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Resume any persistent tasks that you stopped earlier. Tasks should be restarted by the same user or API key that created the task before the migration. Ensure the roles of this user or API key have been updated with the required remote_indices privileges. For users, tasks capture the caller’s credentials when started and run in that user’s security context. For API keys, restarting a task will update the task with the updated API key.

Use the Start transform API to start any transforms.
Use the Open jobs API to open any anomaly detection jobs.
Use the Resume follower API to resume any auto-follow cross-cluster replication.
Use the Resume auto-follow pattern API to resume any manual cross-cluster replication or existing indices that were created from the auto-follow pattern.

Disable certificate based authentication and authorization

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Only proceed with this step if the migration has been proved successful on the local cluster. If the migration is unsuccessful, either find out what the problem is and attempt to fix it or roll back.

Next, disable the certification based connection. Optionally, you can also revoke the authorization.

There is no particular setting to enable or disable a certificate based cross cluster connection, because it shares the same transport protocol with the intra-cluster node-to-node communication.

One way a remote cluster administrator can stop an existing local cluster from connecting, is by changing TLS trust. The exact steps vary, depending on how the clusters have been configured. A generic solution is to recreate the CA and certificate/key used by the remote transport interface so that any existing certificate/key, locally or distributed, is no longer trusted.

Another solution is to apply IP filters to the transport interface, blocking traffic from outside the cluster.
Optionally, delete any roles on the remote cluster that were only used for cross-cluster operations. These roles are no longer used under the API key based security model.

Rollback

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If you need to roll back, follow these steps on the local cluster:

Stop any persistent tasks that refer to the remote cluster.
Remove the remote cluster definition by setting the remote cluster settings to null.
Remove the remote_indices privileges from any roles that were updated during the migration.
On each node, remove the remote_cluster_client.ssl.* settings from elasticsearch.yml.
Restart the local cluster to apply changes to the keystore and elasticsearch.yml.
On the local cluster, apply the original remote cluster settings. If the remote cluster connection has been configured statically (using the elasticsearch.yml file), restart the cluster.
Use the remote cluster info API to verify that the local cluster has connected to the remote cluster. The response should have "connected": true and not have "cluster_credentials": "::es_redacted::".
Restart any persistent tasks that you’ve stopped earlier.

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