[Core] PREVIEW: Support managed identity on Azure Arc-enabled Windows server (Azure#29187)

Author: jiasli

src/azure-cli-core/azure/cli/core/_profile.py

@@ -220,6 +220,10 @@ def login(self,
         return deepcopy(consolidated)
 
     def login_with_managed_identity(self, identity_id=None, allow_no_subscriptions=None):
+        if _on_azure_arc_windows():
+            return self.login_with_managed_identity_azure_arc_windows(
+                identity_id=identity_id, allow_no_subscriptions=allow_no_subscriptions)
+
         import jwt
         from azure.mgmt.core.tools import is_valid_resource_id
         from azure.cli.core.auth.adal_authentication import MSIAuthenticationWrapper
@@ -282,6 +286,33 @@ def login_with_managed_identity(self, identity_id=None, allow_no_subscriptions=N
         self._set_subscriptions(consolidated)
         return deepcopy(consolidated)
 
+    def login_with_managed_identity_azure_arc_windows(self, identity_id=None, allow_no_subscriptions=None):
+        import jwt
+        identity_type = MsiAccountTypes.system_assigned
+        from .auth.msal_credentials import ManagedIdentityCredential
+
+        cred = ManagedIdentityCredential()
+        token = cred.get_token(*self._arm_scope).token
+        logger.info('Managed identity: token was retrieved. Now trying to initialize local accounts...')
+        decode = jwt.decode(token, algorithms=['RS256'], options={"verify_signature": False})
+        tenant = decode['tid']
+
+        subscription_finder = SubscriptionFinder(self.cli_ctx)
+        subscriptions = subscription_finder.find_using_specific_tenant(tenant, cred)
+        base_name = ('{}-{}'.format(identity_type, identity_id) if identity_id else identity_type)
+        user = _USER_ASSIGNED_IDENTITY if identity_id else _SYSTEM_ASSIGNED_IDENTITY
+        if not subscriptions:
+            if allow_no_subscriptions:
+                subscriptions = self._build_tenant_level_accounts([tenant])
+            else:
+                raise CLIError('No access was configured for the managed identity, hence no subscriptions were found. '
+                               "If this is expected, use '--allow-no-subscriptions' to have tenant level access.")
+
+        consolidated = self._normalize_properties(user, subscriptions, is_service_principal=True,
+                                                  user_assigned_identity_id=base_name)
+        self._set_subscriptions(consolidated)
+        return deepcopy(consolidated)
+
     def login_in_cloud_shell(self):
         import jwt
         from .auth.msal_credentials import CloudShellCredential
@@ -354,13 +385,18 @@ def get_login_credentials(self, resource=None, client_id=None, subscription_id=N
             # Cloud Shell
             from .auth.msal_credentials import CloudShellCredential
             from azure.cli.core.auth.credential_adaptor import CredentialAdaptor
-            cs_cred = CloudShellCredential()
-            # The cloud shell credential must be wrapped by CredentialAdaptor so that it can work with Track 1 SDKs.
-            cred = CredentialAdaptor(cs_cred, resource=resource)
+            # The credential must be wrapped by CredentialAdaptor so that it can work with Track 1 SDKs.
+            cred = CredentialAdaptor(CloudShellCredential(), resource=resource)
 
         elif managed_identity_type:
             # managed identity
-            cred = MsiAccountTypes.msi_auth_factory(managed_identity_type, managed_identity_id, resource)
+            if _on_azure_arc_windows():
+                from .auth.msal_credentials import ManagedIdentityCredential
+                from azure.cli.core.auth.credential_adaptor import CredentialAdaptor
+                # The credential must be wrapped by CredentialAdaptor so that it can work with Track 1 SDKs.
+                cred = CredentialAdaptor(ManagedIdentityCredential(), resource=resource)
+            else:
+                cred = MsiAccountTypes.msi_auth_factory(managed_identity_type, managed_identity_id, resource)
 
         else:
             # user and service principal
@@ -415,9 +451,13 @@ def get_raw_token(self, resource=None, scopes=None, subscription=None, tenant=No
             # managed identity
             if tenant:
                 raise CLIError("Tenant shouldn't be specified for managed identity account")
-            from .auth.util import scopes_to_resource
-            cred = MsiAccountTypes.msi_auth_factory(managed_identity_type, managed_identity_id,
-                                                    scopes_to_resource(scopes))
+            if _on_azure_arc_windows():
+                from .auth.msal_credentials import ManagedIdentityCredential
+                cred = ManagedIdentityCredential()
+            else:
+                from .auth.util import scopes_to_resource
+                cred = MsiAccountTypes.msi_auth_factory(managed_identity_type, managed_identity_id,
+                                                        scopes_to_resource(scopes))
 
         else:
             cred = self._create_credential(account, tenant)
@@ -918,3 +958,8 @@ def _create_identity_instance(cli_ctx, *args, **kwargs):
     return Identity(*args, encrypt=encrypt, use_msal_http_cache=use_msal_http_cache,
                     enable_broker_on_windows=enable_broker_on_windows,
                     instance_discovery=instance_discovery, **kwargs)
+
+
+def _on_azure_arc_windows():
+    # This indicates an Azure Arc-enabled Windows server
+    return "IDENTITY_ENDPOINT" in os.environ and "IMDS_ENDPOINT" in os.environ

src/azure-cli-core/azure/cli/core/auth/msal_credentials.py

@@ -18,7 +18,8 @@
 
 from knack.log import get_logger
 from knack.util import CLIError
-from msal import PublicClientApplication, ConfidentialClientApplication
+from msal import (PublicClientApplication, ConfidentialClientApplication,
+                  ManagedIdentityClient, SystemAssignedManagedIdentity)
 
 from .constants import AZURE_CLI_CLIENT_ID
 from .util import check_result, build_sdk_access_token
@@ -131,3 +132,21 @@ def get_token(self, *scopes, **kwargs):
         result = self._msal_app.acquire_token_interactive(list(scopes), prompt="none", **kwargs)
         check_result(result, scopes=scopes)
         return build_sdk_access_token(result)
+
+
+class ManagedIdentityCredential:  # pylint: disable=too-few-public-methods
+    """Managed identity credential implementing get_token interface.
+    Currently, only Azure Arc's system-assigned managed identity is supported.
+    """
+
+    def __init__(self):
+        import requests
+        self._msal_client = ManagedIdentityClient(SystemAssignedManagedIdentity(), http_client=requests.Session())
+
+    def get_token(self, *scopes, **kwargs):
+        logger.debug("ManagedIdentityCredential.get_token: scopes=%r, kwargs=%r", scopes, kwargs)
+
+        from .util import scopes_to_resource
+        result = self._msal_client.acquire_token_for_client(resource=scopes_to_resource(scopes))
+        check_result(result)
+        return build_sdk_access_token(result)