wrap activity ids and urls and actor ids in our /r/ endpoint

for #16, #32. cc @swentel.

common.py

@@ -267,6 +267,9 @@ def postprocess_as2(activity, target=None, key=None):
 
     assert activity.get('id') or (isinstance(obj, dict) and obj.get('id'))
 
+    activity['id'] = redirect_wrap(activity['id'])
+    activity['url'] = redirect_wrap(activity['url'])
+
     # cc public and target's author(s) and recipients
     # https://www.w3.org/TR/activitystreams-vocabulary/#audienceTargeting
     # https://w3c.github.io/activitypub/#delivery
@@ -299,6 +302,21 @@ def postprocess_as2_actor(actor):
         domain = urlparse.urlparse(url).netloc
         actor.setdefault('preferredUsername', domain)
         actor['id'] = '%s/%s' % (appengine_config.HOST_URL, domain)
+        actor['url'] = redirect_wrap(url)
+
+
+def redirect_wrap(url):
+    """Returns a URL on our domain that redirects to this URL.
+
+    ...to satisfy Mastodon's non-standard domain matching requirement. :(
+
+    https://github.com/snarfed/bridgy-fed/issues/16#issuecomment-424799599
+    https://github.com/tootsuite/mastodon/pull/6219#issuecomment-429142747
+    """
+    prefix = urlparse.urljoin(appengine_config.HOST_URL, '/r/')
+    if url.startswith(prefix):
+        return url
+    return prefix + url
 
 
 def beautifulsoup_parse(html, **kwargs):

tests/test_activitypub.py

@@ -42,7 +42,7 @@ class ActivityPubTest(testutil.TestCase):
             'name': 'Mrs. ☕ Foo',
             'preferredUsername': 'foo.com',
             'id': 'http://localhost/foo.com',
-            'url': 'https://foo.com/about-me',
+            'url': 'http://localhost/r/https://foo.com/about-me',
             'inbox': 'http://localhost/foo.com/inbox',
             'publicKey': {
                 'publicKeyPem': MagicKey.get_by_id('foo.com').public_pem(),

tests/test_webmention.py

@@ -110,8 +110,8 @@ class WebmentionTest(testutil.TestCase):
         self.repost_as2 = {
             '@context': 'https://www.w3.org/ns/activitystreams',
             'type': 'Announce',
-            'id': 'http://a/repost',
-            'url': 'http://a/repost',
+            'id': 'http://localhost/r/http://a/repost',
+            'url': 'http://localhost/r/http://a/repost',
             'name': 'reposted!',
             'object': 'tag:orig,2017:as2',
             'cc': [
@@ -123,7 +123,7 @@ class WebmentionTest(testutil.TestCase):
             'actor': {
                 'type': 'Person',
                 'id': 'http://localhost/orig',
-                'url': 'http://orig',
+                'url': 'http://localhost/r/http://orig',
                 'name': 'Ms. ☕ Baz',
                 'preferredUsername': 'orig',
             },
@@ -157,8 +157,8 @@ class WebmentionTest(testutil.TestCase):
             'object': {
                 '@context': 'https://www.w3.org/ns/activitystreams',
                 'type': 'Note',
-                'id': 'http://a/reply',
-                'url': 'http://a/reply',
+                'id': 'http://localhost/r/http://a/reply',
+                'url': 'http://localhost/r/http://a/reply',
                 'name': 'foo ☕ bar',
                 'content': '<a class="u-in-reply-to" href="http://orig/post">foo ☕ bar</a>\n<a href="https://fed.brid.gy/"></a>',
                 'inReplyTo': 'tag:orig,2017:as2',
@@ -171,7 +171,7 @@ class WebmentionTest(testutil.TestCase):
                 'attributedTo': [{
                     'type': 'Person',
                     'id': 'http://localhost/orig',
-                    'url': 'http://orig',
+                    'url': 'http://localhost/r/http://orig',
                     'preferredUsername': 'orig',
                     'name': 'Ms. ☕ Baz',
                 }],