Fix Container.image resolving the wrong image

docker/models/containers.py

@@ -38,10 +38,15 @@ def image(self):
         """
         The image of the container.
         """
-        image_id = self.attrs.get('ImageID', self.attrs['Image'])
+        image_id = self.attrs.get('ImageID') or self.attrs.get('Image')
         if image_id is None:
             return None
-        return self.client.images.get(image_id.split(':')[1])
+        # ``ImageID`` is a digest; strip the algorithm prefix from it. Daemons
+        # that omit ``ImageID`` report a name such as ``busybox:latest`` in
+        # ``Image`` instead, which must not be split on its tag separator.
+        if image_id.startswith('sha256:'):
+            image_id = image_id[len('sha256:'):]
+        return self.client.images.get(image_id)
 
     @property
     def labels(self):

tests/unit/models_containers_test.py

@@ -725,6 +725,24 @@ def test_image(self):
         client = make_fake_client()
         container = client.containers.get(FAKE_CONTAINER_ID)
         assert container.image.id == FAKE_IMAGE_ID
+        # The container reports no 'ImageID', so the name in 'Image' is looked
+        # up as-is rather than being split on its tag separator.
+        client.api.inspect_image.assert_called_with('busybox:latest')
+
+    def test_image_from_image_id(self):
+        client = make_fake_client()
+        container = client.containers.get(FAKE_CONTAINER_ID)
+        container.attrs['ImageID'] = FAKE_IMAGE_ID
+        assert container.image.id == FAKE_IMAGE_ID
+        client.api.inspect_image.assert_called_with(
+            FAKE_IMAGE_ID[len('sha256:'):]
+        )
+
+    def test_image_without_image_id_or_image(self):
+        client = make_fake_client()
+        container = client.containers.get(FAKE_CONTAINER_ID)
+        del container.attrs['Image']
+        assert container.image is None
 
     def test_kill(self):
         client = make_fake_client()