Skip data URIs in transformer

emails/testsuite/transformer/test_transformer.py

@@ -66,6 +66,32 @@ def test_tag_attribute():
     assert m3.attachments['1.jpg'].content_disposition == "inline"
 
 
+def test_data_uri_preserved():
+    DATA_URI = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
+
+    # data URIs in img src should be left untouched
+    html = '<img src="%s"/>' % DATA_URI
+    m = emails.loader.from_string(html=html)
+    assert len(m.attachments.keys()) == 0
+    assert DATA_URI in m.html
+
+    # data URIs in css url() should be left untouched
+    html = '<div style="background: url(%s);">x</div>' % DATA_URI
+    m = emails.loader.from_string(html=html)
+    assert len(m.attachments.keys()) == 0
+
+    # data URIs in background attribute should be left untouched
+    html = '<table background="%s"/>' % DATA_URI
+    m = emails.loader.from_string(html=html)
+    assert len(m.attachments.keys()) == 0
+
+    # mixed-case scheme should also be preserved
+    mixed = DATA_URI.replace('data:', 'Data:')
+    html = '<img src="%s"/>' % mixed
+    m = emails.loader.from_string(html=html)
+    assert len(m.attachments.keys()) == 0
+
+
 ROOT = os.path.dirname(__file__)
 
 def test_local_premailer():

emails/transformer.py

@@ -242,6 +242,9 @@ def _load_attachment_func(self, uri, element=None, callback=None, **kw):
         # Return local uri
         #
 
+        if uri[:5].lower() == 'data:':
+            return uri
+
         if callback is None:
             # Default callback: skip images with data-emails="ignore" attribute
             callback = lambda _, hints: hints['attrib'] != 'ignore'