fix(mp): Throws a 403 exception when a user try to quote a wrong post.

1. Creates a decorator.py file in the mp module.
2. Adds the method is_participant to apply checks on view.
3. Adds this permission on the view PrivatePostAnswer.
4. Adds a test case.

zds/mp/decorator.py

@@ -0,0 +1,23 @@
+# coding: utf-8
+
+from django.core.exceptions import PermissionDenied
+from django.shortcuts import get_object_or_404
+from zds.mp.models import PrivateTopic, PrivatePost
+
+
+def is_participant(func):
+    """
+    Checks if the current user is a participant of the private topic specified in the URL
+    and if the post specified in the GET parameter `cite` is on the private topic.
+    :param func: the decorated function
+    :return: `True` if the current user can read and write, `False` otherwise.
+    """
+    def _is_participant(request, *args, **kwargs):
+        private_topic = get_object_or_404(PrivateTopic, pk=kwargs.get('pk'))
+        if not request.user == private_topic.author and request.user not in list(private_topic.participants.all()):
+            raise PermissionDenied
+        if 'cite' in request.GET:
+            if PrivatePost.objects.filter(privatetopic=private_topic).filter(pk=request.GET.get('cite')).count() != 1:
+                raise PermissionDenied
+        return func(request, *args, **kwargs)
+    return _is_participant

zds/mp/tests/tests_views.py

@@ -492,6 +492,25 @@ def test_fail_cite_post_no_exist(self):
 
         self.assertEqual(404, response.status_code)
 
+    def test_fail_cite_post_not_in_current_topic(self):
+        another_topic = PrivateTopicFactory(author=self.profile2.user)
+        another_post = PrivatePostFactory(
+            privatetopic=another_topic,
+            author=self.profile2.user,
+            position_in_topic=1)
+
+        response = self.client.get(reverse('private-posts-new', args=[self.topic1.pk, self.topic1.slug()]) +
+                                   '?cite={}'.format(another_post.pk))
+
+        self.assertEqual(403, response.status_code)
+
+    def test_success_cite_post(self):
+
+        response = self.client.get(reverse('private-posts-new', args=[self.topic1.pk, self.topic1.slug()]) +
+                                   '?cite={}'.format(self.post2.pk))
+
+        self.assertEqual(200, response.status_code)
+
     def test_success_preview_answer(self):
 
         response = self.client.post(

zds/mp/views.py

@@ -23,6 +23,7 @@
 from django.utils.translation import ugettext as _
 
 from zds.member.models import Profile
+from zds.mp.decorator import is_participant
 from zds.utils.mps import send_mp
 from zds.utils.paginator import ZdSPagingListView
 from zds.utils.templatetags.emarkdown import emarkdown
@@ -287,6 +288,7 @@ class PrivatePostAnswer(CreateView):
     queryset = PrivateTopic.objects.all()
 
     @method_decorator(login_required)
+    @method_decorator(is_participant)
     def dispatch(self, request, *args, **kwargs):
         return super(PrivatePostAnswer, self).dispatch(request, *args, **kwargs)
 
@@ -296,9 +298,6 @@ def get_object(self, queryset=None):
             .filter(privatetopic=self.topic) \
             .prefetch_related() \
             .order_by("-pubdate")[:settings.ZDS_APP['forum']['posts_per_page']]
-        if not self.request.user == self.topic.author \
-                and self.request.user not in list(self.topic.participants.all()):
-            raise PermissionDenied
         return self.topic
 
     def get(self, request, *args, **kwargs):