Update group system grant policies for admins

This commit updates the policies for adding and removing system
assignments from groups to be consistent with other system-scoped
policies.

Subsequent patches will build on this work and:

  - add domain user test coverage
  - add project user test coverage
  - remove obsolete policies from policy.v3cloudsample.json

Change-Id: I90ecc67dbae60c74b69bb227a08205d4415bd16e
Related-Bug: 1805368
Related-Bug: 1750669
Related-Bug: 1806762
(cherry picked from commit ba09e89ba1)

keystone/common/policies/grant.py

@@ -39,6 +39,14 @@ deprecated_list_system_grants_for_group = policy.DeprecatedRule(
     name=base.IDENTITY % 'list_system_grants_for_group',
     check_str=base.RULE_ADMIN_REQUIRED
 )
+deprecated_create_system_grant_for_group = policy.DeprecatedRule(
+    name=base.IDENTITY % 'create_system_grant_for_group',
+    check_str=base.RULE_ADMIN_REQUIRED
+)
+deprecated_revoke_system_grant_for_group = policy.DeprecatedRule(
+    name=base.IDENTITY % 'revoke_system_grant_for_group',
+    check_str=base.RULE_ADMIN_REQUIRED
+)
 
 DEPRECATED_REASON = """
 As of the Stein release, the system assignment API now understands default
@@ -239,7 +247,7 @@ grant_policies = [
     ),
     policy.DocumentedRuleDefault(
         name=base.IDENTITY % 'create_system_grant_for_group',
-        check_str=base.RULE_ADMIN_REQUIRED,
+        check_str=base.SYSTEM_ADMIN,
         scope_types=['system'],
         description='Grant a group a role on the system.',
         operations=[
@@ -247,11 +255,14 @@ grant_policies = [
                 'path': '/v3/system/groups/{group_id}/roles/{role_id}',
                 'method': ['PUT']
             }
-        ]
+        ],
+        deprecated_rule=deprecated_create_system_grant_for_group,
+        deprecated_reason=DEPRECATED_REASON,
+        deprecated_since=versionutils.deprecated.STEIN
     ),
     policy.DocumentedRuleDefault(
         name=base.IDENTITY % 'revoke_system_grant_for_group',
-        check_str=base.RULE_ADMIN_REQUIRED,
+        check_str=base.SYSTEM_ADMIN,
         scope_types=['system'],
         description='Remove a role from a group on the system.',
         operations=[
@@ -259,7 +270,10 @@ grant_policies = [
                 'path': '/v3/system/groups/{group_id}/roles/{role_id}',
                 'method': ['DELETE']
             }
-        ]
+        ],
+        deprecated_rule=deprecated_revoke_system_grant_for_group,
+        deprecated_reason=DEPRECATED_REASON,
+        deprecated_since=versionutils.deprecated.STEIN
     )
 ]
 

keystone/tests/unit/protection/v3/test_system_assignments.py

@@ -359,6 +359,34 @@ class SystemAdminTests(base_classes.TestCaseWithBootstrap,
                 ), headers=self.headers
             )
 
+    def test_user_can_grant_group_system_assignments(self):
+        group = PROVIDERS.identity_api.create_group(
+            unit.new_group_ref(CONF.identity.default_domain_id)
+        )
+
+        with self.test_client() as c:
+            c.put(
+                '/v3/system/groups/%s/roles/%s' % (
+                    group['id'], self.bootstrapper.member_role_id
+                ), headers=self.headers,
+            )
+
+    def test_user_can_revoke_group_system_assignments(self):
+        group = PROVIDERS.identity_api.create_group(
+            unit.new_group_ref(CONF.identity.default_domain_id)
+        )
+
+        PROVIDERS.assignment_api.create_system_grant_for_group(
+            group['id'], self.bootstrapper.member_role_id
+        )
+
+        with self.test_client() as c:
+            c.delete(
+                '/v3/system/groups/%s/roles/%s' % (
+                    group['id'], self.bootstrapper.member_role_id
+                ), headers=self.headers
+            )
+
 
 class DomainUserTests(base_classes.TestCaseWithBootstrap,
                       common_auth.AuthTestMixin,