Revert disabling MD5 checksums

This was a significant breaking change that was landed despite explicit
disagreement by some community members (myself included). It has already
resulted in an accidental Ironic CI breakage, has broken Bifrost and has
a potential of breaking Metal3. In case of Metal3, MD5 support is a part
of its public API.

While MD5 is a potential security hazard, I don't see the need to hurry
this change without giving the community time to prepare. This change
reverts the new option md5_enabled to True.

Change-Id: I32b291ea162e8eb22429712c15cb5b225a6daafd

ironic_python_agent/config.py

@@ -329,8 +329,9 @@ cli_opts = [
                      'cluster which may be visible over a storage fabric '
                      'such as FibreChannel.'),
     cfg.BoolOpt('md5_enabled',
-                default=False,
-                help='If the MD5 algorithm is enabled for file checksums.'),
+                default=True,
+                help='If the MD5 algorithm is enabled for file checksums. '
+                     'Will be changed to False in the future.'),
 ]
 
 CONF.register_cli_opts(cli_opts)

ironic_python_agent/tests/unit/extensions/test_standby.py

@@ -123,6 +123,7 @@ class TestStandbyExtension(base.IronicAgentTest):
         standby._validate_image_info(None, image_info)
 
     def test_validate_image_info_legacy_md5_checksum(self):
+        CONF.set_override('md5_enabled', False)
         image_info = _build_fake_image_info()
         del image_info['os_hash_algo']
         del image_info['os_hash_value']

releasenotes/notes/disable-md5-image-checksum-7def176928d36e75.yaml

@@ -6,14 +6,7 @@ features:
     (SHA-2) and SHA256 (SHA-2) checksums to be identified and utilized without
     an explicit declaration of the checksum type utilizing the
     ``os_hash_algo`` value.
-upgrade:
-  - |
-    MD5 support for checksums have been disabled by default. This may result
-    in rebulids or manual deploy attempts to fail if no updated checksum has
-    been supplied for the ``os_hash_value`` and ``os_hash_algo`` settings.
-    To re-enable MD5 support, you may utilize a the ``[DEFAULT]md5_enabled``
-    setting.
 deprecations:
   - |
-    Support for MD5 checksums have been deprecated and disabled by default.
-    Support for MD5 checksums will be removed after the 2024 Release.
+    Support for MD5 checksums have been deprecated and will be removed after
+    the 2024 Release.