Load template files only from their known source

Modify get_class to ensure that user-defined resources cannot result in
reads from the local filesystem. Only resources defined by the operator
in the global environment should read local files.

To make this work, this patch also adds a separate
get_class_to_instantiate() method to the Environment.

We were previously using get_class for two different purposes - to get a
resource plugin on which we could perform introspection to obtain the
properties and attributes schema, and to get a resource plugin we could
instantiate to create a Resource object. These are both the same except in
the case of a TemplateResource, where having two different use cases for
the same piece of code was adding considerable extra complexity. Combining
the use cases in this way also made the error handling confusing (leading
to bug 1518458).

This change separates out the two cases.

Change-Id: I845e7d23c73242a4a4c9c40599690ab705c75caa
Closes-Bug: #1496277
Related-Bug: #1447194
Related-Bug: #1518458
Related-Bug: #1508115
(cherry picked from commit 06a713c4456203cd561f16721dc8ac3bcbb37a3
                       and 26e6d5f6d776c1027c4f27058767952a58d15e25)

7 files changed, 58 insertions, 40 deletions

diff --git a/heat/engine/environment.py b/heat/engine/environment.py
index 0fd51b313..af8b32830 100644
--- a/heat/engine/environment.py
+++ b/heat/engine/environment.py
@@ -118,6 +118,12 @@ class ResourceInfo(object):
     def matches(self, resource_type):
         return False
 
+    def get_class(self):
+        raise NotImplemented
+
+    def get_class_to_instantiate(self):
+        return self.get_class()
+
     def __str__(self):
         return '[%s](User:%s) %s -> %s' % (self.description,
                                            self.user_resource,
@@ -146,10 +152,23 @@ class TemplateResourceInfo(ResourceInfo):
 
     def get_class(self, files=None):
         from heat.engine.resources import template_resource
+        if files and self.template_name in files:
+            data = files[self.template_name]
+        else:
+            if self.user_resource:
+                allowed_schemes = template_resource.REMOTE_SCHEMES
+            else:
+                allowed_schemes = template_resource.LOCAL_SCHEMES
+            data = template_resource.TemplateResource.get_template_file(
+                self.template_name,
+                allowed_schemes)
         env = self.registry.environment
-        return template_resource.generate_class(str(self.name),
-                                                self.template_name,
-                                                env, files=files)
+        return template_resource.generate_class_from_template(str(self.name),
+                                                              data, env)
+
+    def get_class_to_instantiate(self):
+        from heat.engine.resources import template_resource
+        return template_resource.TemplateResource
 
 
 class MapResourceInfo(ResourceInfo):
@@ -418,6 +437,13 @@ class ResourceRegistry(object):
                 return match
 
     def get_class(self, resource_type, resource_name=None, files=None):
+        info = self.get_resource_info(resource_type,
+                                      resource_name=resource_name)
+        if info is None:
+            raise exception.ResourceTypeNotFound(type_name=resource_type)
+        return info.get_class(files=files)
+
+    def get_class_to_instantiate(self, resource_type, resource_name=None):
         if resource_type == "":
             msg = _('Resource "%s" has no type') % resource_name
             raise exception.StackValidationFailed(message=msg)
@@ -434,7 +460,7 @@ class ResourceRegistry(object):
         if info is None:
             msg = _("Unknown resource Type : %s") % resource_type
             raise exception.StackValidationFailed(message=msg)
-        return info.get_class(files=files)
+        return info.get_class_to_instantiate()
 
     def as_dict(self):
         """Return user resources in a dict format."""
@@ -582,6 +608,10 @@ class Environment(object):
         return self.registry.get_class(resource_type, resource_name,
                                        files=files)
 
+    def get_class_to_instantiate(self, resource_type, resource_name=None):
+        return self.registry.get_class_to_instantiate(resource_type,
+                                                      resource_name)
+
     def get_types(self,
                   cnxt=None,
                   support_status=None,
diff --git a/heat/engine/resource.py b/heat/engine/resource.py
index e820692bb..0db8c405e 100644
--- a/heat/engine/resource.py
+++ b/heat/engine/resource.py
@@ -128,15 +128,10 @@ class Resource(object):
             # Call is already for a subclass, so pass it through
             ResourceClass = cls
         else:
-            from heat.engine.resources import template_resource
-
             registry = stack.env.registry
-            try:
-                ResourceClass = registry.get_class(definition.resource_type,
-                                                   resource_name=name,
-                                                   files=stack.t.files)
-            except exception.NotFound:
-                ResourceClass = template_resource.TemplateResource
+            ResourceClass = registry.get_class_to_instantiate(
+                definition.resource_type,
+                resource_name=name)
 
             assert issubclass(ResourceClass, Resource)
 
diff --git a/heat/engine/resources/openstack/heat/resource_group.py b/heat/engine/resources/openstack/heat/resource_group.py
index c0c555546..f28dfe0e0 100644
--- a/heat/engine/resources/openstack/heat/resource_group.py
+++ b/heat/engine/resources/openstack/heat/resource_group.py
@@ -282,11 +282,7 @@ class ResourceGroup(stack_resource.StackResource):
         val_templ = template.Template(test_tmpl)
         res_def = val_templ.resource_definitions(self.stack)["0"]
         # make sure we can resolve the nested resource type
-        try:
-            self.stack.env.get_class(res_def.resource_type)
-        except exception.NotFound:
-            # its a template resource
-            pass
+        self.stack.env.get_class_to_instantiate(res_def.resource_type)
 
         try:
             name = "%s-%s" % (self.stack.name, self.name)
diff --git a/heat/engine/resources/template_resource.py b/heat/engine/resources/template_resource.py
index fddb81390..eae54ad03 100644
--- a/heat/engine/resources/template_resource.py
+++ b/heat/engine/resources/template_resource.py
@@ -27,12 +27,11 @@ from heat.engine.resources import stack_resource
 from heat.engine import template
 
 
-def generate_class(name, template_name, env, files=None):
-    data = None
-    if files is not None:
-        data = files.get(template_name)
-    if data is None:
-        data = TemplateResource.get_template_file(template_name, ('file',))
+REMOTE_SCHEMES = ('http', 'https')
+LOCAL_SCHEMES = ('file',)
+
+
+def generate_class_from_template(name, data, env):
     tmpl = template.Template(template_format.parse(data))
     props, attrs = TemplateResource.get_schemas(tmpl, env.param_defaults)
     cls = type(name, (TemplateResource,),
@@ -85,9 +84,9 @@ class TemplateResource(stack_resource.StackResource):
             self.resource_type = tri.name
             self.resource_path = tri.path
             if tri.user_resource:
-                self.allowed_schemes = ('http', 'https')
+                self.allowed_schemes = REMOTE_SCHEMES
             else:
-                self.allowed_schemes = ('http', 'https', 'file')
+                self.allowed_schemes = REMOTE_SCHEMES + LOCAL_SCHEMES
 
         return tri
 
diff --git a/heat/engine/service.py b/heat/engine/service.py
index 5706451ff..e1b7cc0ea 100644
--- a/heat/engine/service.py
+++ b/heat/engine/service.py
@@ -1212,8 +1212,6 @@ class EngineService(service.Service):
         self.resource_enforcer.enforce(cnxt, type_name)
         try:
             resource_class = resources.global_env().get_class(type_name)
-        except exception.StackValidationFailed:
-            raise exception.ResourceTypeNotFound(type_name=type_name)
         except exception.NotFound:
             LOG.exception(_LE('Error loading resource type %s '
                               'from global environment.'),
@@ -1260,17 +1258,16 @@ class EngineService(service.Service):
         self.resource_enforcer.enforce(cnxt, type_name)
         try:
             resource_class = resources.global_env().get_class(type_name)
-            if resource_class.support_status.status == support.HIDDEN:
-                raise exception.NotSupported(type_name)
-            return resource_class.resource_to_template(type_name,
-                                                       template_type)
-        except exception.StackValidationFailed:
-            raise exception.ResourceTypeNotFound(type_name=type_name)
         except exception.NotFound:
             LOG.exception(_LE('Error loading resource type %s '
                               'from global environment.'),
                           type_name)
             raise exception.InvalidGlobalResource(type_name=type_name)
+        else:
+            if resource_class.support_status.status == support.HIDDEN:
+                raise exception.NotSupported(type_name)
+            return resource_class.resource_to_template(type_name,
+                                                       template_type)
 
     @context.request_context
     def list_events(self, cnxt, stack_identity, filters=None, limit=None,
diff --git a/heat/tests/test_provider_template.py b/heat/tests/test_provider_template.py
index d84726c40..eca767f0a 100644
--- a/heat/tests/test_provider_template.py
+++ b/heat/tests/test_provider_template.py
@@ -665,7 +665,11 @@ class ProviderTemplateTest(common.HeatTestCase):
 
         env_str = {'resource_registry': {'resources': {'fred': {
             "OS::ResourceType": test_templ_name}}}}
-        env = environment.Environment(env_str)
+        global_env = environment.Environment({}, user_env=False)
+        global_env.load(env_str)
+        with mock.patch('heat.engine.resources._environment',
+                        global_env):
+            env = environment.Environment({})
         cls = env.get_class('OS::ResourceType', 'fred')
         self.assertNotEqual(template_resource.TemplateResource, cls)
         self.assertTrue(issubclass(cls, template_resource.TemplateResource))
@@ -692,10 +696,6 @@ class ProviderTemplateTest(common.HeatTestCase):
         self.assertTrue(test_templ, "Empty test template")
         self.m.StubOutWithMock(urlfetch, "get")
         urlfetch.get(test_templ_name,
-                     allowed_schemes=('file',)
-                     ).AndRaise(urlfetch.URLFetchError(
-                         _('Failed to retrieve template')))
-        urlfetch.get(test_templ_name,
                      allowed_schemes=('http', 'https')).AndReturn(test_templ)
         parsed_test_templ = template_format.parse(test_templ)
         self.m.ReplayAll()
diff --git a/heat/tests/test_resource.py b/heat/tests/test_resource.py
index cb70bac19..29096277b 100644
--- a/heat/tests/test_resource.py
+++ b/heat/tests/test_resource.py
@@ -69,12 +69,13 @@ class ResourceTest(common.HeatTestCase):
         self.dummy_timeout = 10
 
     def test_get_class_ok(self):
-        cls = resources.global_env().get_class('GenericResourceType')
+        cls = resources.global_env().get_class_to_instantiate(
+            'GenericResourceType')
         self.assertEqual(generic_rsrc.GenericResource, cls)
 
     def test_get_class_noexist(self):
         self.assertRaises(exception.StackValidationFailed,
-                          resources.global_env().get_class,
+                          resources.global_env().get_class_to_instantiate,
                           'NoExistResourceType')
 
     def test_resource_new_ok(self):