Update the GetAttributes payloads to support KMIP 2.0

This change updates the GetAttributes payloads to support KMIP 2.0
features, including swapping out Attribute Names for the Attribute
Reference structure in the request payload and the Attribute list
for the Attributes structure in the response payload. Unit tests
have been added to cover these changes.

kmip/core/messages/payloads/get_attributes.py

@@ -124,6 +124,10 @@ class GetAttributesRequestPayload(primitives.Struct):
             kmip_version (KMIPVersion): An enumeration defining the KMIP
                 version with which the object will be decoded. Optional,
                 defaults to KMIP 1.0.
+
+        Raises:
+            InvalidKmipEncoding: Raised if an invalid type is found for the
+                AttributeReference encoding for KMIP 2.0+ encodings.
         """
         super(GetAttributesRequestPayload, self).read(
             input_buffer,
@@ -143,11 +147,45 @@ class GetAttributesRequestPayload(primitives.Struct):
             self._unique_identifier = None
 
         names = list()
-        while self.is_tag_next(enums.Tags.ATTRIBUTE_NAME, local_buffer):
-            name = primitives.TextString(tag=enums.Tags.ATTRIBUTE_NAME)
-            name.read(local_buffer, kmip_version=kmip_version)
-            names.append(name)
-        self._attribute_names = names
+        if kmip_version < enums.KMIPVersion.KMIP_2_0:
+            while self.is_tag_next(enums.Tags.ATTRIBUTE_NAME, local_buffer):
+                name = primitives.TextString(tag=enums.Tags.ATTRIBUTE_NAME)
+                name.read(local_buffer, kmip_version=kmip_version)
+                names.append(name)
+            self._attribute_names = names
+        else:
+            while self.is_tag_next(
+                    enums.Tags.ATTRIBUTE_REFERENCE,
+                    local_buffer
+            ):
+                if self.is_type_next(enums.Types.STRUCTURE, local_buffer):
+                    reference = objects.AttributeReference()
+                    reference.read(local_buffer, kmip_version=kmip_version)
+                    names.append(
+                        primitives.TextString(
+                            value=reference.attribute_name,
+                            tag=enums.Tags.ATTRIBUTE_NAME
+                        )
+                    )
+                elif self.is_type_next(enums.Types.ENUMERATION, local_buffer):
+                    reference = primitives.Enumeration(
+                        enums.Tags,
+                        tag=enums.Tags.ATTRIBUTE_REFERENCE
+                    )
+                    reference.read(local_buffer, kmip_version=kmip_version)
+                    name = enums.convert_attribute_tag_to_name(reference.value)
+                    names.append(
+                        primitives.TextString(
+                            value=name,
+                            tag=enums.Tags.ATTRIBUTE_NAME
+                        )
+                    )
+                else:
+                    raise exceptions.InvalidKmipEncoding(
+                        "The GetAttributes request payload encoding contains "
+                        "an invalid AttributeReference type."
+                    )
+            self._attribute_names = names
 
         self.is_oversized(local_buffer)
 
@@ -172,8 +210,25 @@ class GetAttributesRequestPayload(primitives.Struct):
                 kmip_version=kmip_version
             )
 
-        for attribute_name in self._attribute_names:
-            attribute_name.write(local_buffer, kmip_version=kmip_version)
+        if kmip_version < enums.KMIPVersion.KMIP_2_0:
+            for attribute_name in self._attribute_names:
+                attribute_name.write(local_buffer, kmip_version=kmip_version)
+        else:
+            # NOTE (ph) This approach simplifies backwards compatible issues
+            #           but limits easy support for using AttributeReference
+            #           structures going forward, specifically limiting the
+            #           use of VendorIdentification for custom attributes.
+            #           If custom attributes need to be retrieved using
+            #           the GetAttributes operation for KMIP 2.0 applications
+            #           this code will need to change.
+            for attribute_name in self._attribute_names:
+                t = enums.convert_attribute_name_to_tag(attribute_name.value)
+                e = primitives.Enumeration(
+                    enums.Tags,
+                    value=t,
+                    tag=enums.Tags.ATTRIBUTE_REFERENCE
+                )
+                e.write(local_buffer, kmip_version=kmip_version)
 
         self.length = local_buffer.length()
         super(GetAttributesRequestPayload, self).write(
@@ -321,11 +376,26 @@ class GetAttributesResponsePayload(primitives.Struct):
                 "unique identifier."
             )
 
-        self._attributes = list()
-        while self.is_tag_next(enums.Tags.ATTRIBUTE, local_buffer):
-            attribute = objects.Attribute()
-            attribute.read(local_buffer, kmip_version=kmip_version)
-            self._attributes.append(attribute)
+        if kmip_version < enums.KMIPVersion.KMIP_2_0:
+            self._attributes = list()
+            while self.is_tag_next(enums.Tags.ATTRIBUTE, local_buffer):
+                attribute = objects.Attribute()
+                attribute.read(local_buffer, kmip_version=kmip_version)
+                self._attributes.append(attribute)
+        else:
+            if self.is_tag_next(enums.Tags.ATTRIBUTES, local_buffer):
+                attributes = objects.Attributes()
+                attributes.read(local_buffer, kmip_version=kmip_version)
+                # TODO (ph) Add a new utility to avoid using TemplateAttributes
+                temp_attr = objects.convert_attributes_to_template_attribute(
+                    attributes
+                )
+                self._attributes = temp_attr.attributes
+            else:
+                raise exceptions.InvalidKmipEncoding(
+                    "The GetAttributes response payload encoding is missing "
+                    "the attributes structure."
+                )
 
         self.is_oversized(local_buffer)
 
@@ -355,8 +425,24 @@ class GetAttributesResponsePayload(primitives.Struct):
                 "identifier field."
             )
 
-        for attribute in self._attributes:
-            attribute.write(local_buffer, kmip_version=kmip_version)
+        if kmip_version < enums.KMIPVersion.KMIP_2_0:
+            for attribute in self._attributes:
+                attribute.write(local_buffer, kmip_version=kmip_version)
+        else:
+            if self._attributes:
+                # TODO (ph) Add a new utility to avoid using TemplateAttributes
+                template_attribute = objects.TemplateAttribute(
+                    attributes=self.attributes
+                )
+                attributes = objects.convert_template_attribute_to_attributes(
+                    template_attribute
+                )
+                attributes.write(local_buffer, kmip_version=kmip_version)
+            else:
+                raise exceptions.InvalidField(
+                    "The GetAttributes response payload is missing the "
+                    "attributes list."
+                )
 
         self.length = local_buffer.length()
         super(GetAttributesResponsePayload, self).write(