[Fix] Infer Azure tenant ID if not set (#638)

## Changes
Port of databricks/databricks-sdk-go#910 to the
Python SDK.

In order to use Azure U2M or M2M authentication with the Databricks SDK,
users must request a token from the Entra ID instance that the
underlying workspace or account belongs to, as Databricks rejects
requests to workspaces with a token from a different Entra ID tenant.
However, with Azure CLI auth, it is possible that a user is logged into
multiple tenants at the same time. Currently, the SDK uses the
subscription ID from the configured Azure Resource ID for the workspace
when issuing the `az account get-access-token` command. However, when
users don't specify the resource ID, the SDK simply fetches a token for
the active subscription for the user. If the active subscription is in a
different tenant than the workspace, users will see an error such as:

```
io.jsonwebtoken.IncorrectClaimException: Expected iss claim to be: https://sts.windows.net/72f988bf-86f1-41af-91ab-2d7cd011db47/, but was: https://sts.windows.net/e3fe3f22-4b98-4c04-82cc-d8817d1b17da/
```

This PR modifies Azure CLI and Azure SP credential providers to attempt
to load the tenant ID of the workspace if not provided before
authenticating. Currently, there are no unauthenticated endpoints that
the tenant ID can be directly fetched from. However, the tenant ID is
indirectly exposed via the redirect URL used when logging into a
workspace. In this PR, we fetch the tenant ID from this endpoint and
configure it if not already set.

Here, we lazily fetch the tenant ID only in the auth methods that need
it. This prevents us from making any unnecessary requests if these Azure
credential providers are not needed.

## Tests
Unit tests check that the tenant ID is fetched automatically if not
specified for an azure workspace when authenticating with client
ID/secret or with the CLI.

- [x] `make test` run locally
- [x] `make fmt` applied
- [x] relevant integration tests applied

databricks/sdk/config.py

@@ -363,6 +363,33 @@ def _fix_host_if_needed(self):
 
         self.host = urllib.parse.urlunparse((o.scheme, netloc, path, o.params, o.query, o.fragment))
 
+    def load_azure_tenant_id(self):
+        """[Internal] Load the Azure tenant ID from the Azure Databricks login page.
+
+        If the tenant ID is already set, this method does nothing."""
+        if not self.is_azure or self.azure_tenant_id is not None or self.host is None:
+            return
+        login_url = f'{self.host}/aad/auth'
+        logger.debug(f'Loading tenant ID from {login_url}')
+        resp = requests.get(login_url, allow_redirects=False)
+        if resp.status_code // 100 != 3:
+            logger.debug(
+                f'Failed to get tenant ID from {login_url}: expected status code 3xx, got {resp.status_code}')
+            return
+        entra_id_endpoint = resp.headers.get('Location')
+        if entra_id_endpoint is None:
+            logger.debug(f'No Location header in response from {login_url}')
+            return
+        # The Location header has the following form: https://login.microsoftonline.com/<tenant-id>/oauth2/authorize?...
+        # The domain may change depending on the Azure cloud (e.g. login.microsoftonline.us for US Government cloud).
+        url = urllib.parse.urlparse(entra_id_endpoint)
+        path_segments = url.path.split('/')
+        if len(path_segments) < 2:
+            logger.debug(f'Invalid path in Location header: {url.path}')
+            return
+        self.azure_tenant_id = path_segments[1]
+        logger.debug(f'Loaded tenant ID: {self.azure_tenant_id}')
+
     def _set_inner_config(self, keyword_args: Dict[str, any]):
         for attr in self.attributes():
             if attr.name not in keyword_args:

databricks/sdk/credentials_provider.py

@@ -233,8 +233,7 @@ def _ensure_host_present(cfg: 'Config', token_source_for: Callable[[str], TokenS
     cfg.host = f"https://{resp.json()['properties']['workspaceUrl']}"
 
 
-@oauth_credentials_strategy('azure-client-secret',
-                            ['is_azure', 'azure_client_id', 'azure_client_secret', 'azure_tenant_id'])
+@oauth_credentials_strategy('azure-client-secret', ['is_azure', 'azure_client_id', 'azure_client_secret'])
 def azure_service_principal(cfg: 'Config') -> CredentialsProvider:
     """ Adds refreshed Azure Active Directory (AAD) Service Principal OAuth tokens
     to every request, while automatically resolving different Azure environment endpoints. """
@@ -248,6 +247,7 @@ def token_source_for(resource: str) -> TokenSource:
                                  use_params=True)
 
     _ensure_host_present(cfg, token_source_for)
+    cfg.load_azure_tenant_id()
     logger.info("Configured AAD token for Service Principal (%s)", cfg.azure_client_id)
     inner = token_source_for(cfg.effective_azure_login_app_id)
     cloud = token_source_for(cfg.arm_environment.service_management_endpoint)
@@ -432,11 +432,13 @@ def refresh(self) -> Token:
 class AzureCliTokenSource(CliTokenSource):
     """ Obtain the token granted by `az login` CLI command """
 
-    def __init__(self, resource: str, subscription: str = ""):
+    def __init__(self, resource: str, subscription: Optional[str] = None, tenant: Optional[str] = None):
         cmd = ["az", "account", "get-access-token", "--resource", resource, "--output", "json"]
-        if subscription != "":
+        if subscription is not None:
             cmd.append("--subscription")
             cmd.append(subscription)
+        if tenant:
+            cmd.extend(["--tenant", tenant])
         super().__init__(cmd=cmd,
                          token_type_field='tokenType',
                          access_token_field='accessToken',
@@ -464,8 +466,10 @@ def is_human_user(self) -> bool:
     @staticmethod
     def for_resource(cfg: 'Config', resource: str) -> 'AzureCliTokenSource':
         subscription = AzureCliTokenSource.get_subscription(cfg)
-        if subscription != "":
-            token_source = AzureCliTokenSource(resource, subscription)
+        if subscription is not None:
+            token_source = AzureCliTokenSource(resource,
+                                               subscription=subscription,
+                                               tenant=cfg.azure_tenant_id)
             try:
                 # This will fail if the user has access to the workspace, but not to the subscription
                 # itself.
@@ -475,25 +479,26 @@ def for_resource(cfg: 'Config', resource: str) -> 'AzureCliTokenSource':
             except OSError:
                 logger.warning("Failed to get token for subscription. Using resource only token.")
 
-        token_source = AzureCliTokenSource(resource)
+        token_source = AzureCliTokenSource(resource, subscription=None, tenant=cfg.azure_tenant_id)
         token_source.token()
         return token_source
 
     @staticmethod
-    def get_subscription(cfg: 'Config') -> str:
+    def get_subscription(cfg: 'Config') -> Optional[str]:
         resource = cfg.azure_workspace_resource_id
         if resource is None or resource == "":
-            return ""
+            return None
         components = resource.split('/')
         if len(components) < 3:
             logger.warning("Invalid azure workspace resource ID")
-            return ""
+            return None
         return components[2]
 
 
 @credentials_strategy('azure-cli', ['is_azure'])
 def azure_cli(cfg: 'Config') -> Optional[CredentialsProvider]:
     """ Adds refreshed OAuth token granted by `az login` command to every request. """
+    cfg.load_azure_tenant_id()
     token_source = None
     mgmt_token_source = None
     try:
@@ -517,11 +522,6 @@ def azure_cli(cfg: 'Config') -> Optional[CredentialsProvider]:
 
     _ensure_host_present(cfg, lambda resource: AzureCliTokenSource.for_resource(cfg, resource))
     logger.info("Using Azure CLI authentication with AAD tokens")
-    if not cfg.is_account_client and AzureCliTokenSource.get_subscription(cfg) == "":
-        logger.warning(
-            "azure_workspace_resource_id field not provided. "
-            "It is recommended to specify this field in the Databricks configuration to avoid authentication errors."
-        )
 
     def inner() -> Dict[str, str]:
         token = token_source.token()

tests/conftest.py

@@ -77,3 +77,16 @@ def set_az_path(monkeypatch):
         monkeypatch.setenv('COMSPEC', 'C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe')
     else:
         monkeypatch.setenv('PATH', __tests__ + "/testdata:/bin")
+
+
+@pytest.fixture
+def mock_tenant(requests_mock):
+
+    def stub_tenant_request(host, tenant_id="test-tenant-id"):
+        mock = requests_mock.get(
+            f'https://{host}/aad/auth',
+            status_code=302,
+            headers={'Location': f'https://login.microsoftonline.com/{tenant_id}/oauth2/authorize'})
+        return mock
+
+    return stub_tenant_request

tests/test_auth.py

@@ -193,9 +193,10 @@ def test_config_azure_pat():
     assert cfg.is_azure
 
 
-def test_config_azure_cli_host(monkeypatch):
+def test_config_azure_cli_host(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     cfg = Config(host='https://adb-123.4.azuredatabricks.net', azure_workspace_resource_id='/sub/rg/ws')
 
     assert cfg.auth_type == 'azure-cli'
@@ -229,20 +230,22 @@ def test_config_azure_cli_host_pat_conflict_with_config_file_present_without_def
     cfg = Config(token='x', azure_workspace_resource_id='/sub/rg/ws')
 
 
-def test_config_azure_cli_host_and_resource_id(monkeypatch):
+def test_config_azure_cli_host_and_resource_id(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     cfg = Config(host='https://adb-123.4.azuredatabricks.net', azure_workspace_resource_id='/sub/rg/ws')
 
     assert cfg.auth_type == 'azure-cli'
     assert cfg.host == 'https://adb-123.4.azuredatabricks.net'
     assert cfg.is_azure
 
 
-def test_config_azure_cli_host_and_resource_i_d_configuration_precedence(monkeypatch):
+def test_config_azure_cli_host_and_resource_i_d_configuration_precedence(monkeypatch, mock_tenant):
     monkeypatch.setenv('DATABRICKS_CONFIG_PROFILE', 'justhost')
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     cfg = Config(host='https://adb-123.4.azuredatabricks.net', azure_workspace_resource_id='/sub/rg/ws')
 
     assert cfg.auth_type == 'azure-cli'

tests/test_auth_manual_tests.py

@@ -3,9 +3,10 @@
 from .conftest import set_az_path, set_home
 
 
-def test_azure_cli_workspace_header_present(monkeypatch):
+def test_azure_cli_workspace_header_present(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     resource_id = '/subscriptions/123/resourceGroups/abc/providers/Microsoft.Databricks/workspaces/abc123'
     cfg = Config(auth_type='azure-cli',
                  host='https://adb-123.4.azuredatabricks.net',
@@ -14,19 +15,21 @@ def test_azure_cli_workspace_header_present(monkeypatch):
     assert cfg.authenticate()['X-Databricks-Azure-Workspace-Resource-Id'] == resource_id
 
 
-def test_azure_cli_user_with_management_access(monkeypatch):
+def test_azure_cli_user_with_management_access(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     resource_id = '/subscriptions/123/resourceGroups/abc/providers/Microsoft.Databricks/workspaces/abc123'
     cfg = Config(auth_type='azure-cli',
                  host='https://adb-123.4.azuredatabricks.net',
                  azure_workspace_resource_id=resource_id)
     assert 'X-Databricks-Azure-SP-Management-Token' in cfg.authenticate()
 
 
-def test_azure_cli_user_no_management_access(monkeypatch):
+def test_azure_cli_user_no_management_access(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     monkeypatch.setenv('FAIL_IF', 'https://management.core.windows.net/')
     resource_id = '/subscriptions/123/resourceGroups/abc/providers/Microsoft.Databricks/workspaces/abc123'
     cfg = Config(auth_type='azure-cli',
@@ -35,9 +38,10 @@ def test_azure_cli_user_no_management_access(monkeypatch):
     assert 'X-Databricks-Azure-SP-Management-Token' not in cfg.authenticate()
 
 
-def test_azure_cli_fallback(monkeypatch):
+def test_azure_cli_fallback(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     monkeypatch.setenv('FAIL_IF', 'subscription')
     resource_id = '/subscriptions/123/resourceGroups/abc/providers/Microsoft.Databricks/workspaces/abc123'
     cfg = Config(auth_type='azure-cli',
@@ -46,9 +50,10 @@ def test_azure_cli_fallback(monkeypatch):
     assert 'X-Databricks-Azure-SP-Management-Token' in cfg.authenticate()
 
 
-def test_azure_cli_with_warning_on_stderr(monkeypatch):
+def test_azure_cli_with_warning_on_stderr(monkeypatch, mock_tenant):
     set_home(monkeypatch, '/testdata/azure')
     set_az_path(monkeypatch)
+    mock_tenant('adb-123.4.azuredatabricks.net')
     monkeypatch.setenv('WARN', 'this is a warning')
     resource_id = '/subscriptions/123/resourceGroups/abc/providers/Microsoft.Databricks/workspaces/abc123'
     cfg = Config(auth_type='azure-cli',

tests/test_config.py

@@ -1,3 +1,4 @@
+import os
 import platform
 
 import pytest
@@ -6,7 +7,9 @@
 from databricks.sdk.config import Config, with_product, with_user_agent_extra
 from databricks.sdk.version import __version__
 
-from .conftest import noop_credentials
+from .conftest import noop_credentials, set_az_path
+
+__tests__ = os.path.dirname(__file__)
 
 
 def test_config_supports_legacy_credentials_provider():
@@ -74,3 +77,40 @@ def test_config_copy_deep_copies_user_agent_other_info(config):
     assert "blueprint/0.4.6" in config.user_agent
     assert "blueprint/0.4.6" in config_copy.user_agent
     useragent._reset_extra(original_extra)
+
+
+def test_load_azure_tenant_id_404(requests_mock, monkeypatch):
+    set_az_path(monkeypatch)
+    mock = requests_mock.get('https://abc123.azuredatabricks.net/aad/auth', status_code=404)
+    cfg = Config(host="https://abc123.azuredatabricks.net")
+    assert cfg.azure_tenant_id is None
+    assert mock.called_once
+
+
+def test_load_azure_tenant_id_no_location_header(requests_mock, monkeypatch):
+    set_az_path(monkeypatch)
+    mock = requests_mock.get('https://abc123.azuredatabricks.net/aad/auth', status_code=302)
+    cfg = Config(host="https://abc123.azuredatabricks.net")
+    assert cfg.azure_tenant_id is None
+    assert mock.called_once
+
+
+def test_load_azure_tenant_id_unparsable_location_header(requests_mock, monkeypatch):
+    set_az_path(monkeypatch)
+    mock = requests_mock.get('https://abc123.azuredatabricks.net/aad/auth',
+                             status_code=302,
+                             headers={'Location': 'https://unexpected-location'})
+    cfg = Config(host="https://abc123.azuredatabricks.net")
+    assert cfg.azure_tenant_id is None
+    assert mock.called_once
+
+
+def test_load_azure_tenant_id_happy_path(requests_mock, monkeypatch):
+    set_az_path(monkeypatch)
+    mock = requests_mock.get(
+        'https://abc123.azuredatabricks.net/aad/auth',
+        status_code=302,
+        headers={'Location': 'https://login.microsoftonline.com/tenant-id/oauth2/authorize'})
+    cfg = Config(host="https://abc123.azuredatabricks.net")
+    assert cfg.azure_tenant_id == 'tenant-id'
+    assert mock.called_once