Using Polaris with Keycloak as external IDP

This example uses Keycloak as an external identity provider for Polaris. The “iceberg” realm is automatically created and configured from the iceberg-realm.json file.

This Keycloak realm contains 1 client definition: client1:s3cr3t. It is configured to return tokens with the following fixed claims:

• principal_id: the principal ID of the user. It is always set to zero (0) in this example.
• principal_name: the principal name of the user. It is always set to “root” in this example.
• principal_roles: the principal roles of the user. It is always set to ["server_admin", "catalog_admin"] in this example.

This is obviously not a realistic configuration. In a real-world scenario, you would configure Keycloak to return the actual principal ID, name and roles of the user. Note that principals and principal roles must have been created in Polaris beforehand, and the principal ID, name and roles must match the ones returned by Keycloak.

Polaris is configured with 3 realms:

• realm-internal: This is the default realm, and is configured to use the internal authentication only. It accepts token issues by Polaris itself only.
• realm-external: This realm is configured to use an external identity provider (IDP) for authentication only. It accepts tokens issued by Keycloak only.
• realm-mixed: This realm is configured to use both the internal and external authentication. It accepts tokens issued by both Polaris and Keycloak.

For more information about how to configure Polaris with external authentication, see the Polaris documentation.

Starting the Example

1. Build the Polaris server image if it’s not already present locally:

   ./gradlew \
      :polaris-server:assemble \
      :polaris-server:quarkusAppPartsBuild --rerun \
      -Dquarkus.container-image.build=true
   

2. Start the docker compose group by running the following command from the root of the repository:

   docker compose -f getting-started/keycloak/docker-compose.yml up
   

Requesting a Token

Note: the commands below require jq to be installed on your machine.

From Polaris

You can request a token from Polaris for realms realm-internal and realm-mixed:

1. Open a terminal and run the following command to request an access token for the realm-internal realm:

   polaris_token_realm_internal=$(curl -s http://localhost:8181/api/catalog/v1/oauth/tokens \
     --user root:s3cr3t \
     -H 'Polaris-Realm: realm-internal' \
     -d 'grant_type=client_credentials' \
     -d 'scope=PRINCIPAL_ROLE:ALL' | jq -r .access_token)
   

   This token is valid only for the realm-internal realm.

2. Open a terminal and run the following command to request an access token for the realm-mixed realm:

   polaris_token_realm_mixed=$(curl -s http://localhost:8181/api/catalog/v1/oauth/tokens \
     --user root:s3cr3t \
     -H 'Polaris-Realm: realm-mixed' \
     -d 'grant_type=client_credentials' \
     -d 'scope=PRINCIPAL_ROLE:ALL' | jq -r .access_token)
   

   This token is valid only for the realm-mixed realm.

Polaris tokens are valid for 1 hour.

Note: if you request a Polaris token for the realm-external realm, it will not work because Polaris won’t issue tokens for this realm:

curl -v http://localhost:8181/api/catalog/v1/oauth/tokens \
  --user root:s3cr3t \
  -H 'Polaris-Realm: realm-external' \
  -d 'grant_type=client_credentials' \
  -d 'scope=PRINCIPAL_ROLE:ALL'

This will return a 501 Not Implemented error because for this realm, the internal token endpoint has been deactivated.

From Keycloak

You can request a token from Keycloak for the realm-external and realm-mixed realms:

1. Open a terminal and run the following command to request an access token from Keycloak:

   keycloak_token=$(curl -s http://keycloak:8080/realms/iceberg/protocol/openid-connect/token \
     --resolve keycloak:8080:127.0.0.1 \
     --user client1:s3cr3t \
     -d 'grant_type=client_credentials' | jq -r .access_token)
   

Note the --resolve option: it is used to send the request with the Host header set to keycloak. This is necessary because Keycloak issues tokens with the iss claim matching the request’s Host header; without this, the token would not be valid when used against Polaris because the iss claim would be 127.0.0.1, but Polaris expects it to be keycloak, since that’s Keycloak’s hostname within the Docker network.

Tokens issued by Keycloak can be used to access Polaris with the realm-external or realm-mixed realms. Access tokens are valid for 1 hour.

You can also access the Keycloak admin console. Open a browser and go to http://localhost:8080, then log in with the username admin and password admin (you can change this in the docker-compose file).

Accessing Polaris with the Tokens

You can access Polaris using the tokens you obtained above. The following examples show how to use the tokens with curl:

Using the Polaris Token

1. Open a terminal and run the following command to list the principal roles in the realm-internal realm:

   curl -v http://localhost:8181/api/management/v1/catalogs \
     -H "Authorization: Bearer $polaris_token_realm_internal" \
     -H 'Polaris-Realm: realm-internal' \
     -H 'Accept: application/json'
   

2. Open a terminal and run the following command to list the principal roles in the realm-mixed realm:

   curl -v http://localhost:8181/api/management/v1/catalogs \
     -H "Authorization: Bearer $polaris_token_realm_mixed" \
     -H 'Polaris-Realm: realm-mixed' \
     -H 'Accept: application/json'
   

Note: you cannot mix tokens from different realms. For example, you cannot use a token from the realm-internal realm to access the realm-mixed realm:

curl -v http://localhost:8181/api/management/v1/catalogs \
  -H "Authorization: Bearer $polaris_token_realm_internal" \
  -H 'Polaris-Realm: realm-mixed' \
  -H 'Accept: application/json'

This will return a 401 Unauthorized error because the token is not valid for the realm-mixed realm.

Using the Keycloak Token

The same Keycloak token can be used to access both the realm-external and realm-mixed realms, as it is valid for both (both realms share the same OIDC tenant configuration).

1. Open a terminal and run the following command to list the principal roles in the realm-external realm:

   curl -v http://localhost:8181/api/management/v1/catalogs \
     -H "Authorization: Bearer $keycloak_token" \
     -H 'Polaris-Realm: realm-external' \
     -H 'Accept: application/json'
   

2. Open a terminal and run the following command to list the principal roles in the realm-mixed realm:

   curl -v http://localhost:8181/api/management/v1/catalogs \
     -H "Authorization: Bearer $keycloak_token" \
     -H 'Polaris-Realm: realm-mixed' \
     -H 'Accept: application/json'
   

Note: you cannot use a Keycloak token to access the realm-internal realm:

curl -v http://localhost:8181/api/management/v1/catalogs \
  -H "Authorization: Bearer $keycloak_token" \
  -H 'Polaris-Realm: realm-internal' \
  -H 'Accept: application/json'

This will return a 401 Unauthorized error because the token is not valid for the realm-internal realm.