Add option to toggle validation of signed image

Without this patch, if the barbican tempest plugin is installed in an
environment running with `[glance]/verify_glance_signatures] set to
false in nova.conf, which is the default value, the test will fail.
Enabling glance signature verification unconditionally in order to
support this test is not realistic, as it then prevents users from
booting from unsigned images which may not always be desired. This patch
adds a configuration option to allow for disabling the
`test_signed_image_upload_boot_failure` test, so that we can still run
the majority of the plugin tests for a standard environment with default
nova configuration. The new option defaults to `True`, meaning assume
that nova's configuration has been overrridden to enforce image
verification, which allows the barbican CI to run as normal with no
configuration changes, but it allows operators to explicitly disable the
test as needed.

Change-Id: Ibb5c06ce2773e0ee13bda97717e8e18e77e0be7c

barbican_tempest_plugin/config.py

@@ -43,3 +43,14 @@ EphemeralStorageEncryptionGroup = [
                default=256,
                help="The key size used to encrypt ephemeral storage."),
 ]
+
+image_signature_verification_group = cfg.OptGroup(
+    name="image_signature_verification",
+    title="Image Signature Verification Options")
+
+ImageSignatureVerificationGroup = [
+    cfg.BoolOpt('enforced',
+                default=True,
+                help="Does the test environment enforce glance image "
+                     "verification?"),
+]

barbican_tempest_plugin/plugin.py

@@ -37,6 +37,8 @@ class BarbicanTempestPlugin(plugins.TempestPlugin):
         conf.register_group(project_config.ephemeral_storage_encryption_group)
         conf.register_opts(project_config.EphemeralStorageEncryptionGroup,
                            project_config.ephemeral_storage_encryption_group)
+        conf.register_opts(project_config.ImageSignatureVerificationGroup,
+                           project_config.image_signature_verification_group)
 
     def get_opt_lists(self):
         return [('service_available', [project_config.service_option])]

barbican_tempest_plugin/tests/scenario/test_image_signing.py

@@ -70,6 +70,10 @@ class ImageSigningTest(barbican_manager.BarbicanScenarioTest):
             * Attempt to boot the incorrectly signed image
             * Confirm an exception is thrown
         """
+        if not CONF.image_signature_verification.enforced:
+            raise self.skipException("Image signature verification is not "
+                                     "enforced in this environment")
+
         img_uuid = self.sign_and_upload_image()
 
         LOG.debug("Modifying image signature to be incorrect")