From b5cacb09e3a8e9f04bbf92d179f9c2c96ea05011 Mon Sep 17 00:00:00 2001
From: Andrew Godwin
Date: Sun, 13 Nov 2022 19:03:43 -0700
Subject: Permit Mastodon's weird HTML through

---
 activities/admin.py             |  6 ++++++
 activities/models/post.py       | 15 +++++++++++++++
 core/html.py                    | 24 ++++++++++++++++++++++--
 templates/activities/_post.html |  2 +-
 users/views/activitypub.py      |  2 +-
 5 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/activities/admin.py b/activities/admin.py
index d4603a4..947a596 100644
--- a/activities/admin.py
+++ b/activities/admin.py
@@ -7,6 +7,12 @@ from activities.models import FanOut, Post, PostInteraction, TimelineEvent
 class PostAdmin(admin.ModelAdmin):
     list_display = ["id", "state", "author", "created"]
     raw_id_fields = ["to", "mentions"]
+    actions = ["force_fetch"]
+
+    @admin.action(description="Force Fetch")
+    def force_fetch(self, request, queryset):
+        for instance in queryset:
+            instance.debug_fetch()
 
 
 @admin.register(TimelineEvent)
diff --git a/activities/models/post.py b/activities/models/post.py
index d847307..74b335b 100644
--- a/activities/models/post.py
+++ b/activities/models/post.py
@@ -274,3 +274,18 @@ class Post(StatorModel):
             TimelineEvent.add_post(follow.source, post)
         # Force it into fanned_out as it's not ours
         post.transition_perform(PostStates.fanned_out)
+
+    def debug_fetch(self):
+        """
+        Fetches the Post from its original URL again and updates us with it
+        """
+        response = httpx.get(
+            self.object_uri,
+            headers={"Accept": "application/json"},
+            follow_redirects=True,
+        )
+        if 200 <= response.status_code < 300:
+            return self.by_ap(
+                canonicalise(response.json(), include_security=True),
+                update=True,
+            )
diff --git a/core/html.py b/core/html.py
index e63dda3..fd41a50 100644
--- a/core/html.py
+++ b/core/html.py
@@ -1,11 +1,31 @@
 import bleach
+from bleach.linkifier import LinkifyFilter
 from django.utils.safestring import mark_safe
 
 
+def allow_a(tag: str, name: str, value: str):
+    if name in ["href", "title", "class"]:
+        return True
+    elif name == "rel":
+        # Only allow rel attributes with a small subset of values
+        # (we're defending against, for example, rel=me)
+        rel_values = value.split()
+        if all(v in ["nofollow", "noopener", "noreferrer", "tag"] for v in rel_values):
+            return True
+    return False
+
+
 def sanitize_post(post_html: str) -> str:
     """
     Only allows a, br, p and span tags, and class attributes.
     """
-    return mark_safe(
-        bleach.clean(post_html, tags=["a", "br", "p", "span"], attributes=["class"])
+    cleaner = bleach.Cleaner(
+        tags=["a", "br", "p", "span"],
+        attributes={  # type:ignore
+            "a": allow_a,
+            "p": ["class"],
+            "span": ["class"],
+        },
+        filters=[LinkifyFilter],
     )
+    return mark_safe(cleaner.clean(post_html))
diff --git a/templates/activities/_post.html b/templates/activities/_post.html
index 601466e..bf4b189 100644
--- a/templates/activities/_post.html
+++ b/templates/activities/_post.html
@@ -1,6 +1,6 @@
 {% load static %}
 {% load activity_tags %}
-<div class="post">
+<div class="post" data-takahe-id="{{ post.id }}">
 
     {% if post.author.icon_uri %}
         <img src="{{post.author.icon_uri}}" class="icon">
diff --git a/users/views/activitypub.py b/users/views/activitypub.py
index 54f04bc..1a709ac 100644
--- a/users/views/activitypub.py
+++ b/users/views/activitypub.py
@@ -118,7 +118,7 @@ class Inbox(View):
             # See if we can fetch it right now
             async_to_sync(identity.fetch_actor)()
         if not identity.public_key:
-            print("Cannot get actor")
+            print("Cannot get actor", document["actor"])
             return HttpResponseBadRequest("Cannot retrieve actor")
         # If there's a "signature" payload, verify against that
         if "signature" in document:
-- 
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