feat: add tiktok link sanitization

Main.py

@@ -45,6 +45,7 @@
     "cogs.quotes",
     "cogs.reminder",
     "cogs.roles",
+    "cogs.sanitizer",
     "cogs.score",
     "cogs.subscribers",    # Do not remove this terminating comma.
 ]

cogs/sanitizer.py

@@ -0,0 +1,82 @@
+# Copyright (C) idoneam (2016-2021)
+#
+# This file is part of Canary
+#
+# Canary is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Canary is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Canary. If not, see <https://www.gnu.org/licenses/>.
+
+import discord
+from discord.ext import commands
+import re
+import aiohttp
+
+TIKTOK_SHORTLINK = re.compile(r"https?:\/\/vm\.tiktok\.com\/[A-Za-z0-9]+")
+TIKTOK_MOBILE = re.compile(
+    r"(https?:\/\/m\.tiktok\.com\/v\/[0-9]+)\.html\?[A-Za-z0-9_&=%\.\?\-\/]+")
+TIKTOK_DESKTOP = re.compile(
+    r"(https?:\/\/www\.tiktok\.com\/@[A-Za-z0-9_\.]+\/video\/[0-9]+)\?[A-Za-z0-9_&=%\.\?\-\/]+"
+)
+
+
+async def unroll_tiktok(link) -> str:
+    async with aiohttp.ClientSession() as session:
+        async with session.head(link,
+                                headers={"User-Agent": "Mozilla/5.0 (X11)"},
+                                allow_redirects=True) as r:
+            return str(r.url)
+
+
+async def short_replace(msg, match) -> str:
+    short_match = match.group()
+    return msg.replace(short_match, await unroll_tiktok(short_match))
+
+
+async def mobile_replace(msg, match) -> str:
+    full, clean = match.group(0, 1)
+    return msg.replace(full, await unroll_tiktok(clean))
+
+
+async def desktop_replace(msg, match) -> str:
+    full, clean = match.group(0, 1)
+    return msg.replace(full, clean)
+
+
+class Sanitizer(commands.Cog):
+    def __init__(self, bot):
+        self.bot = bot
+
+    @commands.Cog.listener("on_message")
+    async def tiktok_link_sanitizer(self, msg):
+        msg_txt: str = str(msg.content)
+        replace: bool = False
+
+        for reg, fun in [(TIKTOK_SHORTLINK, short_replace),
+                         (TIKTOK_MOBILE, mobile_replace),
+                         (TIKTOK_DESKTOP, desktop_replace)]:
+            for match in reg.finditer(msg_txt):
+                msg_txt = await fun(msg_txt, match)
+                replace = True
+
+        if replace:
+            await msg.delete()
+            await msg.channel.send(embed=discord.Embed().set_author(
+                name=msg.author.display_name,
+                icon_url=str(msg.author.avatar_url)
+            ).add_field(name="sanitized message", value=msg_txt).set_footer(
+                text=
+                "unsanitized tiktok URLs can contain potentially sensitive info"
+            ))
+
+
+def setup(bot):
+    bot.add_cog(Sanitizer(bot))