Merge pull request #425 from AzureAD/region-env-var

Detecting Regional Endpoint from env var

msal/application.py

@@ -286,7 +286,8 @@ def __init__(
             which you will later provide via one of the acquire-token request.
 
         :param str azure_region:
-            Added since MSAL Python 1.12.0.
+            AAD provides regional endpoints for apps to opt in
+            to keep their traffic remain inside that region.
 
             As of 2021 May, regional service is only available for
             ``acquire_token_for_client()`` sent by any of the following scenarios::
@@ -303,9 +304,7 @@ def __init__(
 
             4. An app which already onboard to the region's allow-list.
 
-            MSAL's default value is None, which means region behavior remains off.
-            If enabled, the `acquire_token_for_client()`-relevant traffic
-            would remain inside that region.
+            This parameter defaults to None, which means region behavior remains off.
 
             App developer can opt in to a regional endpoint,
             by provide its region name, such as "westus", "eastus2".
@@ -331,6 +330,9 @@ def __init__(
                 or provide a custom http_client which has a short timeout.
                 That way, the latency would be under your control,
                 but still less performant than opting out of region feature.
+
+            New in version 1.12.0.
+
         :param list[str] exclude_scopes: (optional)
             Historically MSAL hardcodes `offline_access` scope,
             which would allow your app to have prolonged access to user's data.
@@ -492,17 +494,18 @@ def _build_telemetry_context(
             correlation_id=correlation_id, refresh_reason=refresh_reason)
 
     def _get_regional_authority(self, central_authority):
-        is_region_specified = bool(self._region_configured
-            and self._region_configured != self.ATTEMPT_REGION_DISCOVERY)
         self._region_detected = self._region_detected or _detect_region(
             self.http_client if self._region_configured is not None else None)
-        if (is_region_specified and self._region_configured != self._region_detected):
+        if (self._region_configured != self.ATTEMPT_REGION_DISCOVERY
+                and self._region_configured != self._region_detected):
             logger.warning('Region configured ({}) != region detected ({})'.format(
                 repr(self._region_configured), repr(self._region_detected)))
         region_to_use = (
-            self._region_configured if is_region_specified else self._region_detected)
+            self._region_detected
+            if self._region_configured == self.ATTEMPT_REGION_DISCOVERY
+            else self._region_configured)  # It will retain the None i.e. opted out
+        logger.debug('Region to be used: {}'.format(repr(region_to_use)))
         if region_to_use:
-            logger.info('Region to be used: {}'.format(repr(region_to_use)))
             regional_host = ("{}.r.login.microsoftonline.com".format(region_to_use)
                 if central_authority.instance in (
                     # The list came from https://github.com/AzureAD/microsoft-authentication-library-for-python/pull/358/files#r629400328

msal/region.py

@@ -5,6 +5,9 @@
 
 
 def _detect_region(http_client=None):
+    region = os.environ.get("REGION_NAME", "").replace(" ", "").lower()  # e.g. westus2
+    if region:
+        return region
     if http_client:
         return _detect_region_of_azure_vm(http_client)  # It could hang for minutes
     return None

tests/test_e2e.py

@@ -791,16 +791,15 @@ class WorldWideRegionalEndpointTestCase(LabBasedTestCase):
     region = "westus"
     timeout = 2  # Short timeout makes this test case responsive on non-VM
 
-    def test_acquire_token_for_client_should_hit_regional_endpoint(self):
+    def _test_acquire_token_for_client(self, configured_region, expected_region):
         """This is the only grant supported by regional endpoint, for now"""
         self.app = get_lab_app(  # Regional endpoint only supports confidential client
 
             ## FWIW, the MSAL<1.12 versions could use this to achieve similar result
             #authority="https://westus.login.microsoft.com/microsoft.onmicrosoft.com",
             #validate_authority=False,
             authority="https://login.microsoftonline.com/microsoft.onmicrosoft.com",
-            azure_region=self.region,  # Explicitly use this region, regardless of detection
-
+            azure_region=configured_region,
             timeout=2,  # Short timeout makes this test case responsive on non-VM
             )
         scopes = ["https://graph.microsoft.com/.default"]
@@ -809,9 +808,11 @@ def test_acquire_token_for_client_should_hit_regional_endpoint(self):
                 self.app.http_client, "post", return_value=MinimalResponse(
                 status_code=400, text='{"error": "mock"}')) as mocked_method:
             self.app.acquire_token_for_client(scopes)
+            expected_host = '{}.r.login.microsoftonline.com'.format(
+                expected_region) if expected_region else 'login.microsoftonline.com'
             mocked_method.assert_called_with(
-                'https://westus.r.login.microsoftonline.com/{}/oauth2/v2.0/token'.format(
-                    self.app.authority.tenant),
+                'https://{}/{}/oauth2/v2.0/token'.format(
+                    expected_host, self.app.authority.tenant),
                 params=ANY, data=ANY, headers=ANY)
         result = self.app.acquire_token_for_client(
             scopes,
@@ -820,6 +821,29 @@ def test_acquire_token_for_client_should_hit_regional_endpoint(self):
         self.assertIn('access_token', result)
         self.assertCacheWorksForApp(result, scopes)
 
+    def test_acquire_token_for_client_should_hit_global_endpoint_by_default(self):
+        self._test_acquire_token_for_client(None, None)
+
+    def test_acquire_token_for_client_should_ignore_env_var_by_default(self):
+        os.environ["REGION_NAME"] = "eastus"
+        self._test_acquire_token_for_client(None, None)
+        del os.environ["REGION_NAME"]
+
+    def test_acquire_token_for_client_should_use_a_specified_region(self):
+        self._test_acquire_token_for_client("westus", "westus")
+
+    def test_acquire_token_for_client_should_use_an_env_var_with_short_region_name(self):
+        os.environ["REGION_NAME"] = "eastus"
+        self._test_acquire_token_for_client(
+            msal.ConfidentialClientApplication.ATTEMPT_REGION_DISCOVERY, "eastus")
+        del os.environ["REGION_NAME"]
+
+    def test_acquire_token_for_client_should_use_an_env_var_with_long_region_name(self):
+        os.environ["REGION_NAME"] = "East Us 2"
+        self._test_acquire_token_for_client(
+            msal.ConfidentialClientApplication.ATTEMPT_REGION_DISCOVERY, "eastus2")
+        del os.environ["REGION_NAME"]
+
     @unittest.skipUnless(
         os.getenv("LAB_OBO_CLIENT_SECRET"),
         "Need LAB_OBO_CLIENT_SECRET from https://aka.ms/GetLabSecret?Secret=TodoListServiceV2-OBO")