apache / apache/iceberg-python

Cannot connect to a Hive Metastore with Kerberos when the principal's host differs from the URI host

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Descripción

### Apache Iceberg version

0.11.0 (latest release)

### Please describe the bug 🐞

When connecting to a Kerberos-enabled Hive Metastore, authentication fails if the service principal's host does not match the host in the connection URI, and there is no setting to correct it.

I connect to the metastore through three HA hosts:

```python
from pyiceberg.catalog import load_catalog

catalog = load_catalog("hive", **{
"type": "hive",
"uri": "thrift://myhms1:9083,thrift://myhms2:9083,thrift://myhms3:9083",
"hive.kerberos-authentication": "true",
"hive.kerberos-service-name": "myservice",
})
catalog.list_namespaces()
```

The last line fails with:

```
Traceback (most recent call last):
File "test.py", line 24, in
ns = catalog.list_namespaces()
File ".../pyiceberg/catalog/hive.py", line 769, in list_namespaces
with self._client as open_client:
File ".../pyiceberg/catalog/hive.py", line 180, in __enter__
self._transport.open()
File ".../thrift/transport/TTransport.py", line 382, in open
initial_response = self.sasl.process()
File ".../puresasl/client.py", line 148, in process
return self._chosen_mech.process(challenge)
File ".../puresasl/mechanisms.py", line 505, in process
kerberos.authGSSClientStep(self.context, '')
kerberos.GSSError
```

Enabling `KRB5_TRACE` shows that the failure happens when the client asks the KDC for a service ticket:

```
set-error: -1765328243: Did not find credential for myservice/myhms1@EXAMPLE.COM in cache FILE:...
set-error: -1765328377: Error from KDC: LOOKING_UP_SERVER while looking up 'myservice/myhms1@EXAMPLE.COM'
```

My Hive Metastore's service principal is `myservice/hive-host@EXAMPLE.COM`.
PyIceberg, however, requests a ticket using my HMS server hostname (`myhms1`) as the hostname component, which is not a valid service principal, so the request fails.

A Kerberos service principal has the form `Service/Hostname@REALM` (see [3.2 Principal](https://www.kerberos.org/software/tutorial.html#1.3.2) in the Kerberos tutorial), and with SASL/GSSAPI those two components come from the `service` and `host` arguments passed to the client.
PyIceberg always derives that `host` from the connection URI, so it is forced to be whichever host you connect to.
`hive.kerberos-service-name` (added in #2141) makes the `Service` part configurable, but there is no equivalent for `Hostname`.

The relevant line is [`pyiceberg/catalog/hive.py#L167`](https://github.com/apache/iceberg-python/blob/pyiceberg-0.11.x/pyiceberg/catalog/hive.py#L167) (`_HiveClient._init_thrift_transport`):

```python
return TTransport.TSaslClientTransport(socket, host=url_parts.hostname, service=self._kerberos_service_name)
```

There is no way to avoid this from the client side. The `uri` has to contain the hostnames I actually connect to, and the principal's hostname component is not one of them.
Listing multiple URIs does not help either, because the client is built from the first URI and the failure happens later, during authentication.

So I patch that line locally and hardcode the host:

```python
-return TTransport.TSaslClientTransport(socket, host=url_parts.hostname, service=self._kerberos_service_name)
+return TTransport.TSaslClientTransport(socket, host="hive-host", service=self._kerberos_service_name)
```

With that one change everything works well.
PyIceberg requests `myservice/hive-host@EXAMPLE.COM` and `catalog.list_namespaces()` succeeds.

I would like to propose a new configuration property, `hive.kerberos-service-host`. It could be added in the same way as [#2141](https://github.com/apache/iceberg-python/pull/2141).
When the property is not set, the URI host would be used as the default, so the current behavior is preserved for backward compatibility.

I have finished the implementation including unit tests, and verified it end-to-end against the same metastore.

If this is welcome, I would like to submit the PR myself.

### Willingness to contribute

- [x] I can contribute a fix for this bug independently
- [ ] I would be willing to contribute a fix for this bug with guidance from the Iceberg community
- [ ] I cannot contribute a fix for this bug at this time

Guía de contribución

No hay ninguna guía de contribución indexada para este repositorio

Línea de trabajo

Comienza en pyiceberg/catalog/hive.py#L167, en _HiveClient._init_thrift_transport, y revisa cómo se selecciona el host del servicio Kerberos a partir de la URI. Añade la propiedad de configuración propuesta, conservando el host de la URI como valor predeterminado; después, ejecuta las pruebas unitarias mencionadas en el issue y verifica el comportamiento de la conexión Kerberos.

Escrito por el modelo de indexación a partir del texto del issue.

Evaluación

Stack tecnológico
python
Área
authentication, databases
Tipo de issue
Error
Dificultad
2/5
Tiempo estimado
1-3 horas
Estado de actividad
Tranquilo
Claridad
Bien especificado
Aptitud para principiantes
78/100

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