From a4f00e6242344cdd398ed05eb38fd92da1739193 Mon Sep 17 00:00:00 2001
From: Alek Ratzloff <alekratz@gmail.com>
Date: Wed, 13 Jul 2022 21:28:07 -0700
Subject: [PATCH] Add user post deletion

Users can delete their posts as long as they don't clear their cookies,
and as long as server-side user sessions are persistent.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
---
 board/forms.py         |  3 ++-
 board/models.py        |  4 ++++
 board/utils.py         | 11 +++++++++++
 board/views.py         | 17 ++++++++++++++++-
 threadchat/settings.py |  6 ++++++
 5 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/board/forms.py b/board/forms.py
index 20dd71f..07391b6 100644
--- a/board/forms.py
+++ b/board/forms.py
@@ -25,11 +25,12 @@ class PostForm(ModelForm):
         model = Post
         fields = ["subject", "name", "text", "capcode", "image"]
 
-    def __init__(self, *args, user, board, ip, **kwargs):
+    def __init__(self, *args, user, board, ip, user_token, **kwargs):
         super(PostForm, self).__init__(*args, **kwargs)
         self.user = user
         self.instance.board = board
         self.instance.ip = ip
+        self.instance.user_token = user_token
         self.fields["capcode"].queryset = get_objects_for_user(
             self.user, "board.use_capcode"
         )
diff --git a/board/models.py b/board/models.py
index d76260a..112383e 100644
--- a/board/models.py
+++ b/board/models.py
@@ -124,6 +124,10 @@ class Post(models.Model):
     # Image width and height
     image_width = models.IntegerField(null=True, blank=True)
     image_height = models.IntegerField(null=True, blank=True)
+    # The user token that was used to make this post. This is used for
+    # verification when a user wants to delete their post. It is not
+    # particularly secret and does not need to be hashed.
+    user_token = models.CharField(max_length=30, null=True)
 
     class Meta:
         permissions = [
diff --git a/board/utils.py b/board/utils.py
index 268be2b..8bc7a63 100644
--- a/board/utils.py
+++ b/board/utils.py
@@ -1,6 +1,9 @@
 from typing import Optional, TYPE_CHECKING
 from django.utils import timezone
+from django.conf import settings
 import ipaddress
+import random
+import string
 
 from board.models import Ban, RangeBan
 
@@ -45,3 +48,11 @@ def is_banned(ip: str, board: Optional["Board"]) -> bool:
         return bool(active)
     else:
         return False
+
+
+def generate_user_token() -> str:
+    """
+    Generates a non-secure user token.
+    User tokens need not be secure so this is a simple implementation.
+    """
+    return "".join(random.choices(string.ascii_letters, k=settings.USER_TOKEN_LENGTH))
diff --git a/board/views.py b/board/views.py
index face8da..4f7a52a 100644
--- a/board/views.py
+++ b/board/views.py
@@ -8,7 +8,7 @@ from django.http import Http404, HttpResponseRedirect
 from django.http.request import QueryDict
 from django.shortcuts import get_object_or_404
 from django.views.generic.base import TemplateView
-from django.views.generic import detail, edit
+from django.views.generic import edit
 from django.urls import reverse, reverse_lazy
 from django.utils import timezone
 
@@ -147,6 +147,10 @@ class PostCreateView(CreateView):
     def get_form_kwargs(self):
         kwargs = super(PostCreateView, self).get_form_kwargs()
         kwargs["user"] = self.request.user
+        if "user_token" not in self.request.session:
+            # Generate a user token
+            self.request.session["user_token"] = generate_user_token()
+        kwargs["user_token"] = self.request.session["user_token"]
         return kwargs
 
     def get_success_url(self) -> str:
@@ -213,6 +217,10 @@ class ReplyCreateView(CreateView):
         post = get_object_or_404(Post, id=post_id)
         kwargs["op"] = post
         kwargs["user"] = self.request.user
+        if "user_token" not in self.request.session:
+            # Generate a user token
+            self.request.session["user_token"] = generate_user_token()
+        kwargs["user_token"] = self.request.session["user_token"]
         return kwargs
 
     def get_success_url(self) -> str:
@@ -256,6 +264,13 @@ class PostDeleteView(PermissionRequiredMixin, edit.DeleteView):
     success_url = reverse_lazy("board:post_delete_success")
     raise_exception = True
 
+    def has_permission(self) -> bool:
+        object = self.get_object()
+        user_token = self.request.session.get("user_token", None)
+        return self.request.user.has_perm("board.delete_post") or (
+            user_token and object.user_token == user_token
+        )
+
     def form_valid(self, form):
         success_url = self.get_success_url()
         if form["image_only"].value() != "0":
diff --git a/threadchat/settings.py b/threadchat/settings.py
index c02ad90..ef6f68e 100644
--- a/threadchat/settings.py
+++ b/threadchat/settings.py
@@ -174,3 +174,9 @@ BAN_WINDOW_CLOSE_TIMEOUT = 0
 # By default, wait 0 seconds. If there is an error, the window won't close
 # because it will be redirected elsewhere.
 POST_WINDOW_CLOSE_TIMEOUT = 0
+
+# This is the length of a user's token, which is held in a server-side session.
+# This token is used to identify a user's individual web client, outside of IP
+# address. You probably don't need to change this.
+# It should be at most 30, and probably at least 10.
+USER_TOKEN_LENGTH = 30