From 46c2224a4f07f0dfa9f65094caf3ba186374c569 Mon Sep 17 00:00:00 2001
From: Danielle McLean <dani@00dani.me>
Date: Fri, 11 May 2018 13:23:47 +1000
Subject: [PATCH] Replace the previous WebFinger implementation with a fairly
 simple forwarder to Bridgy Fed, so that Bridgy Fed will work eventually

---
 users/models.py               |  6 ++-
 wellknowns/views/webfinger.py | 81 +++++++++++++++++++----------------
 2 files changed, 50 insertions(+), 37 deletions(-)

diff --git a/users/models.py b/users/models.py
index f6fd500..607a41c 100644
--- a/users/models.py
+++ b/users/models.py
@@ -84,7 +84,11 @@ class User(ModelMeta, AbstractUser):
         return '{0} {1}'.format(self.first_name, self.last_name)
 
     def get_absolute_url(self):
-        return self.url
+        return self.absolute_url
+
+    @property
+    def absolute_url(self):
+        return self.full_url
 
     @property
     def full_url(self):
diff --git a/wellknowns/views/webfinger.py b/wellknowns/views/webfinger.py
index ba3f0f2..05684a9 100644
--- a/wellknowns/views/webfinger.py
+++ b/wellknowns/views/webfinger.py
@@ -1,50 +1,59 @@
-from django.http import HttpResponseBadRequest, HttpResponseNotFound
-from django.http import JsonResponse
+from django.http import HttpResponseBadRequest, HttpResponseRedirect
+from urllib.parse import urlencode, urlparse
+
 from users.models import User
-from django.shortcuts import get_object_or_404
-from urllib.parse import urlparse, urljoin
-from lemoncurry.utils import origin
 
 AVATAR = 'http://webfinger.net/rel/avatar'
 PROFILE_PAGE = 'http://webfinger.net/rel/profile-page'
+BRIDGY_FED = 'https://fed.brid.gy/.well-known/webfinger'
+
+
+def https_resource_matching(resource):
+    """
+    Takes a `urllib.parse.urlparse` tuple representing a WebFinger resource and
+    translates ``mailto:`` and ``xmpp:`` resources to an equivalent ``https:``
+    resource, if a user with matching email or XMPP address exists locally.
+    Will throw `User.DoesNotExist` if no such user exists.
+    """
+    if resource.scheme == 'mailto':
+        query = {'email': resource.path}
+    else:
+        query = {'xmpp': resource.path}
+    return User.objects.get(**query).absolute_url
 
 
 def webfinger(request):
+    """
+    A thin wrapper around Bridgy Fed's implementation of WebFinger.
+
+    In most cases, this view simply redirects to the same endpoint at Bridgy.
+    However, Bridgy does not support the ``mailto:`` and ``xmpp:`` resource
+    schemes - quite reasonably, since there's no possible way to discover the
+    ``acct:`` they go with! - so resources with those schemes are translated
+    locally into an ``https:`` URL representing the same person, and *then*
+    redirected to Bridgy.
+
+    Additionally, WebFinger requests with a missing or malformed resource will
+    be rejected immediately rather than passed on to Bridgy.
+
+    Note that the translation step will only be applied if there exists a
+    :model:`users.User` with matching email or XMPP address. Otherwise, the
+    original resource will be preserved in the redirect - and likely fail to
+    find anything at Bridgy's end either.
+    """
     if 'resource' not in request.GET:
         return HttpResponseBadRequest('resource parameter missing')
+    resource = request.GET['resource']
     try:
-        resource = urlparse(request.GET['resource'])
+        res = urlparse(resource)
     except ValueError:
         return HttpResponseBadRequest('resource parameter malformed')
 
-    if resource.scheme in ('mailto', 'acct', 'xmpp'):
-        user = get_object_or_404(User, email=resource.path)
-    elif resource.scheme in ('http', 'https'):
-        user = get_object_or_404(User, pk=1)
-    else:
-        return HttpResponseNotFound('resource not found on this server')
+    if res.scheme in ('mailto', 'xmpp'):
+        try:
+            resource = https_resource_matching(res)
+        except User.DoesNotExist:
+            pass
 
-    base = origin(request)
-
-    def link(rel, href, type):
-        return {'rel': rel, 'href': urljoin(base, href), 'type': type}
-
-    key_links = tuple(link(
-        rel='pgpkey',
-        href=key.file.url,
-        type='application/pgp-keys',
-    ) for key in user.keys.all())
-
-    info = {
-        'subject': 'acct:' + user.email,
-        'aliases': (
-            urljoin(base, user.url),
-            'mailto:' + user.email,
-            'xmpp:' + user.xmpp,
-        ),
-        'links': (
-            link(rel=AVATAR, href=user.avatar.url, type='image/png'),
-            link(rel=PROFILE_PAGE, href=user.url, type='text/html'),
-        ) + key_links,
-    }
-    return JsonResponse(info, content_type='application/jrd+json')
+    query = urlencode({'resource': resource})
+    return HttpResponseRedirect(BRIDGY_FED + '?' + query)