Merge pull request #259 from python-discord/SebastiaanZ/embed-detection-filter

Detecting self-botting/unofficial client use with a rich embed filter

4 files changed, 77 insertions, 20 deletions

diff --git a/bot/cogs/filtering.py b/bot/cogs/filtering.py
index 247ee26b8..570d6549f 100644
--- a/bot/cogs/filtering.py
+++ b/bot/cogs/filtering.py
@@ -45,6 +45,7 @@ class Filtering:
                 "enabled": Filter.filter_zalgo,
                 "function": self._has_zalgo,
                 "type": "filter",
+                "content_only": True,
                 "user_notification": Filter.notify_user_zalgo,
                 "notification_msg": (
                     "Your post has been removed for abusing Unicode character rendering (aka Zalgo text). "
@@ -55,6 +56,7 @@ class Filtering:
                 "enabled": Filter.filter_invites,
                 "function": self._has_invites,
                 "type": "filter",
+                "content_only": True,
                 "user_notification": Filter.notify_user_invites,
                 "notification_msg": (
                     f"Per Rule 10, your invite link has been removed. {_staff_mistake_str}\n\n"
@@ -65,20 +67,36 @@ class Filtering:
                 "enabled": Filter.filter_domains,
                 "function": self._has_urls,
                 "type": "filter",
+                "content_only": True,
                 "user_notification": Filter.notify_user_domains,
                 "notification_msg": (
                     f"Your URL has been removed because it matched a blacklisted domain. {_staff_mistake_str}"
                 )
             },
+            "filter_rich_embeds": {
+                "enabled": Filter.filter_rich_embeds,
+                "function": self._has_rich_embed,
+                "type": "filter",
+                "content_only": False,
+                "user_notification": Filter.notify_user_rich_embeds,
+                "notification_msg": (
+                    "Your post has been removed because it contained a rich embed. "
+                    "This indicates that you're either using an unofficial discord client or are using a self-bot, "
+                    f"both of which violate Discord's Terms of Service. {_staff_mistake_str}\n\n"
+                    "Please don't use a self-bot or an unofficial Discord client on our server."
+                )
+            },
             "watch_words": {
                 "enabled": Filter.watch_words,
                 "function": self._has_watchlist_words,
                 "type": "watchlist",
+                "content_only": True,
             },
             "watch_tokens": {
                 "enabled": Filter.watch_tokens,
                 "function": self._has_watchlist_tokens,
                 "type": "watchlist",
+                "content_only": True,
             },
         }
 
@@ -121,12 +139,35 @@ class Filtering:
         # If none of the above, we can start filtering.
         if filter_message:
             for filter_name, _filter in self.filters.items():
-
                 # Is this specific filter enabled in the config?
                 if _filter["enabled"]:
-                    triggered = await _filter["function"](msg.content)
+                    # Does the filter only need the message content or the full message?
+                    if _filter["content_only"]:
+                        triggered = await _filter["function"](msg.content)
+                    else:
+                        triggered = await _filter["function"](msg)
 
                     if triggered:
+                        # If this is a filter (not a watchlist), we should delete the message.
+                        if _filter["type"] == "filter":
+                            try:
+                                # Embeds (can?) trigger both the `on_message` and `on_message_edit`
+                                # event handlers, triggering filtering twice for the same message.
+                                #
+                                # If `on_message`-triggered filtering already deleted the message
+                                # then `on_message_edit`-triggered filtering will raise exception
+                                # since the message no longer exists.
+                                #
+                                # In addition, to avoid sending two notifications to the user, the
+                                # logs, and mod_alert, we return if the message no longer exists.
+                                await msg.delete()
+                            except discord.errors.NotFound:
+                                return
+
+                            # Notify the user if the filter specifies
+                            if _filter["user_notification"]:
+                                await self.notify_member(msg.author, _filter["notification_msg"], msg.channel)
+
                         if isinstance(msg.channel, DMChannel):
                             channel_str = "via DM"
                         else:
@@ -142,6 +183,8 @@ class Filtering:
 
                         log.debug(message)
 
+                        additional_embeds = msg.embeds if filter_name == "filter_rich_embeds" else None
+
                         # Send pretty mod log embed to mod-alerts
                         await self.mod_log.send_log_message(
                             icon_url=Icons.filtering,
@@ -151,16 +194,9 @@ class Filtering:
                             thumbnail=msg.author.avatar_url_as(static_format="png"),
                             channel_id=Channels.mod_alerts,
                             ping_everyone=Filter.ping_everyone,
+                            additional_embeds=additional_embeds,
                         )
 
-                        # If this is a filter (not a watchlist), we should delete the message.
-                        if _filter["type"] == "filter":
-                            await msg.delete()
-
-                            # Notify the user if the filter specifies
-                            if _filter["user_notification"]:
-                                await self.notify_member(msg.author, _filter["notification_msg"], msg.channel)
-
                         break  # We don't want multiple filters to trigger
 
     @staticmethod
@@ -272,6 +308,16 @@ class Filtering:
                 return True
         return False
 
+    @staticmethod
+    async def _has_rich_embed(msg: Message):
+        """
+        Returns True if any of the embeds in the message
+        are of type 'rich', returns False otherwise
+        """
+        if msg.embeds:
+            return any(embed.type == "rich" for embed in msg.embeds)
+        return False
+
     async def notify_member(self, filtered_member: Member, reason: str, channel: TextChannel):
         """
         Notify filtered_member about a moderation action with the reason str
diff --git a/bot/cogs/modlog.py b/bot/cogs/modlog.py
index 0561b5afb..c96838a54 100644
--- a/bot/cogs/modlog.py
+++ b/bot/cogs/modlog.py
@@ -106,7 +106,7 @@ class ModLog:
     async def send_log_message(
             self, icon_url: Optional[str], colour: Colour, title: Optional[str], text: str,
             thumbnail: str = None, channel_id: int = Channels.modlog, ping_everyone: bool = False,
-            files: List[File] = None, content: str = None
+            files: List[File] = None, content: str = None, additional_embeds: List[Embed] = None,
     ):
         embed = Embed(description=text)
 
@@ -125,7 +125,14 @@ class ModLog:
             else:
                 content = "@everyone"
 
-        await self.bot.get_channel(channel_id).send(content=content, embed=embed, files=files)
+        channel = self.bot.get_channel(channel_id)
+
+        await channel.send(content=content, embed=embed, files=files)
+
+        if additional_embeds:
+            await channel.send("With the following embed(s):")
+            for additional_embed in additional_embeds:
+                await channel.send(embed=additional_embed)
 
     async def on_guild_channel_create(self, channel: GUILD_CHANNEL):
         if channel.guild.id != GuildConstant.id:
diff --git a/bot/constants.py b/bot/constants.py
index bbe6c1604..c1375bb13 100644
--- a/bot/constants.py
+++ b/bot/constants.py
@@ -201,6 +201,7 @@ class Filter(metaclass=YAMLGetter):
     filter_zalgo: bool
     filter_invites: bool
     filter_domains: bool
+    filter_rich_embeds: bool
     watch_words: bool
     watch_tokens: bool
 
@@ -208,6 +209,7 @@ class Filter(metaclass=YAMLGetter):
     notify_user_zalgo: bool
     notify_user_invites: bool
     notify_user_domains: bool
+    notify_user_rich_embeds: bool
 
     ping_everyone: bool
     guild_invite_whitelist: List[int]
diff --git a/config-default.yml b/config-default.yml
index a51d00778..21d7f20b9 100644
--- a/config-default.yml
+++ b/config-default.yml
@@ -134,17 +134,19 @@ guild:
 filter:
 
     # What do we filter?
-    filter_zalgo:   false
-    filter_invites: true
-    filter_domains: true
-    watch_words:    true
-    watch_tokens:   true
+    filter_zalgo:       false
+    filter_invites:     true
+    filter_domains:     true
+    filter_rich_embeds: true
+    watch_words:        true
+    watch_tokens:       true
 
     # Notify user on filter?
     # Notifications are not expected for "watchlist" type filters
-    notify_user_zalgo:   false
-    notify_user_invites: true
-    notify_user_domains: false
+    notify_user_zalgo:       false
+    notify_user_invites:     true
+    notify_user_domains:     false
+    notify_user_rich_embeds: true
 
     # Filter configuration
     ping_everyone: true  # Ping @everyone when we send a mod-alert?