Work around bug in Docker 28.3.3 that prevents pushing to registry without authentication. (#1110)

changelogs/fragments/1110-push-fix.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - "docker_image, docker_image_push - work around a bug in Docker 28.3.3 that prevents pushing without authentication to a registry
+     (https://github.com/ansible-collections/community.docker/pull/1110)."

plugins/modules/docker_image.py

@@ -363,6 +363,7 @@ stdout:
   version_added: 1.0.0
 """
 
+import base64
 import errno
 import json
 import os
@@ -716,8 +717,11 @@ class ImageManager(DockerBaseClass):
                     push_registry, dummy = resolve_repository_name(push_repository)
                     headers = {}
                     header = get_config_header(self.client, push_registry)
-                    if header:
-                        headers['X-Registry-Auth'] = header
+                    if not header:
+                        # For some reason, from Docker 28.3.3 on not specifying X-Registry-Auth seems to be invalid.
+                        # See https://github.com/moby/moby/issues/50614.
+                        header = base64.urlsafe_b64encode(b"{}")
+                    headers['X-Registry-Auth'] = header
                     response = self.client._post_json(
                         self.client._url("/images/{0}/push", push_repository),
                         data=None,

plugins/modules/docker_image_push.py

@@ -72,6 +72,7 @@ image:
   sample: {}
 """
 
+import base64
 import traceback
 
 from ansible.module_utils.common.text.converters import to_native
@@ -142,8 +143,11 @@ class ImagePusher(DockerBaseClass):
 
             headers = {}
             header = get_config_header(self.client, push_registry)
-            if header:
-                headers['X-Registry-Auth'] = header
+            if not header:
+                # For some reason, from Docker 28.3.3 on not specifying X-Registry-Auth seems to be invalid.
+                # See https://github.com/moby/moby/issues/50614.
+                header = base64.urlsafe_b64encode(b"{}")
+            headers['X-Registry-Auth'] = header
             response = self.client._post_json(
                 self.client._url("/images/{0}/push", self.name),
                 data=None,