Add external auth provider

examples/README.md

@@ -38,3 +38,4 @@ To run all of these examples you can clone the entire repository to your disk. O
 this example the string `ExamplePartnerTag` will be added to the the user agent on every request.
 - **`staging_ingestion.py`** shows how the connector handles Databricks' experimental staging ingestion commands `GET`, `PUT`, and `REMOVE`.
 - **`sqlalchemy.py`** shows a basic example of connecting to Databricks with [SQLAlchemy](https://www.sqlalchemy.org/). 
+- **`custom_cred_provider.py`** shows how to pass a custom credential provider to bypass connector authentication. Please install databricks-sdk prior to running this example.

examples/custom_cred_provider.py

@@ -0,0 +1,29 @@
+# please install databricks-sdk prior to running this example.
+
+from databricks import sql
+from databricks.sdk.oauth import OAuthClient
+import os
+
+oauth_client = OAuthClient(host=os.getenv("DATABRICKS_SERVER_HOSTNAME"),
+                           client_id=os.getenv("DATABRICKS_CLIENT_ID"),
+                           client_secret=os.getenv("DATABRICKS_CLIENT_SECRET"),
+                           redirect_url=os.getenv("APP_REDIRECT_URL"),
+                           scopes=['all-apis', 'offline_access'])
+
+consent = oauth_client.initiate_consent()
+
+creds = consent.launch_external_browser()
+
+with sql.connect(server_hostname = os.getenv("DATABRICKS_SERVER_HOSTNAME"),
+                 http_path       = os.getenv("DATABRICKS_HTTP_PATH"),
+                 credentials_provider=creds) as connection:
+
+    for x in range(1, 5):
+        cursor = connection.cursor()
+        cursor.execute('SELECT 1+1')
+        result = cursor.fetchall()
+        for row in result:
+            print(row)
+        cursor.close()
+
+    connection.close()

src/databricks/sql/auth/auth.py

@@ -5,6 +5,7 @@
     AuthProvider,
     AccessTokenAuthProvider,
     BasicAuthProvider,
+    ExternalAuthProvider,
     DatabricksOAuthProvider,
 )
 from databricks.sql.experimental.oauth_persistence import OAuthPersistence
@@ -30,6 +31,7 @@ def __init__(
         use_cert_as_auth: str = None,
         tls_client_cert_file: str = None,
         oauth_persistence=None,
+        credentials_provider=None,
     ):
         self.hostname = hostname
         self.username = username
@@ -42,9 +44,12 @@ def __init__(
         self.use_cert_as_auth = use_cert_as_auth
         self.tls_client_cert_file = tls_client_cert_file
         self.oauth_persistence = oauth_persistence
+        self.credentials_provider = credentials_provider
 
 
 def get_auth_provider(cfg: ClientContext):
+    if cfg.credentials_provider:
+        return ExternalAuthProvider(cfg.credentials_provider)
     if cfg.auth_type == AuthType.DATABRICKS_OAUTH.value:
         assert cfg.oauth_redirect_port_range is not None
         assert cfg.oauth_client_id is not None
@@ -94,5 +99,6 @@ def get_python_sql_connector_auth_provider(hostname: str, **kwargs):
         if kwargs.get("oauth_client_id") and kwargs.get("oauth_redirect_port")
         else PYSQL_OAUTH_REDIRECT_PORT_RANGE,
         oauth_persistence=kwargs.get("experimental_oauth_persistence"),
+        credentials_provider=kwargs.get("credentials_provider"),
     )
     return get_auth_provider(cfg)

src/databricks/sql/auth/authenticators.py

@@ -1,6 +1,7 @@
+import abc
 import base64
 import logging
-from typing import Dict, List
+from typing import Callable, Dict, List
 
 from databricks.sql.auth.oauth import OAuthManager
 
@@ -14,6 +15,22 @@ def add_headers(self, request_headers: Dict[str, str]):
         pass
 
 
+HeaderFactory = Callable[[], Dict[str, str]]
+
+# In order to keep compatibility with SDK
+class CredentialsProvider(abc.ABC):
+    """CredentialsProvider is the protocol (call-side interface)
+    for authenticating requests to Databricks REST APIs"""
+
+    @abc.abstractmethod
+    def auth_type(self) -> str:
+        ...
+
+    @abc.abstractmethod
+    def __call__(self, *args, **kwargs) -> HeaderFactory:
+        ...
+
+
 # Private API: this is an evolving interface and it will change in the future.
 # Please must not depend on it in your applications.
 class AccessTokenAuthProvider(AuthProvider):
@@ -120,3 +137,13 @@ def _update_token_if_expired(self):
         except Exception as e:
             logging.error(f"unexpected error in oauth token update", e, exc_info=True)
             raise e
+
+
+class ExternalAuthProvider(AuthProvider):
+    def __init__(self, credentials_provider: CredentialsProvider) -> None:
+        self._header_factory = credentials_provider()
+
+    def add_headers(self, request_headers: Dict[str, str]):
+        headers = self._header_factory()
+        for k, v in headers.items():
+            request_headers[k] = v

tests/unit/test_auth.py

@@ -1,7 +1,8 @@
 import unittest
 
-from databricks.sql.auth.auth import AccessTokenAuthProvider, BasicAuthProvider, AuthProvider
+from databricks.sql.auth.auth import AccessTokenAuthProvider, BasicAuthProvider, AuthProvider, ExternalAuthProvider
 from databricks.sql.auth.auth import get_python_sql_connector_auth_provider
+from databricks.sql.auth.authenticators import CredentialsProvider, HeaderFactory
 
 
 class Auth(unittest.TestCase):
@@ -37,6 +38,22 @@ def test_noop_auth_provider(self):
         self.assertEqual(len(http_request.keys()), 1)
         self.assertEqual(http_request['myKey'], 'myVal')
 
+    def test_external_provider(self):
+        class MyProvider(CredentialsProvider):
+                def auth_type(self) -> str:
+                    return "mine"
+
+                def __call__(self, *args, **kwargs) -> HeaderFactory:
+                    return lambda: {"foo": "bar"}
+
+        auth = ExternalAuthProvider(MyProvider())
+
+        http_request = {'myKey': 'myVal'}
+        auth.add_headers(http_request)
+        self.assertEqual(http_request['foo'], 'bar')
+        self.assertEqual(len(http_request.keys()), 2)
+        self.assertEqual(http_request['myKey'], 'myVal')
+
     def test_get_python_sql_connector_auth_provider_access_token(self):
         hostname = "moderakh-test.cloud.databricks.com"
         kwargs = {'access_token': 'dpi123'}
@@ -47,6 +64,24 @@ def test_get_python_sql_connector_auth_provider_access_token(self):
         auth_provider.add_headers(headers)
         self.assertEqual(headers['Authorization'], 'Bearer dpi123')
 
+    def test_get_python_sql_connector_auth_provider_external(self):
+
+        class MyProvider(CredentialsProvider):
+                def auth_type(self) -> str:
+                    return "mine"
+
+                def __call__(self, *args, **kwargs) -> HeaderFactory:
+                    return lambda: {"foo": "bar"}
+
+        hostname = "moderakh-test.cloud.databricks.com"
+        kwargs = {'credentials_provider': MyProvider()}
+        auth_provider = get_python_sql_connector_auth_provider(hostname, **kwargs)
+        self.assertTrue(type(auth_provider).__name__, "ExternalAuthProvider")
+
+        headers = {}
+        auth_provider.add_headers(headers)
+        self.assertEqual(headers['foo'], 'bar')
+
     def test_get_python_sql_connector_auth_provider_username_password(self):
         username = "moderakh"
         password = "Elevate Databricks 123!!!"