From 163f3efdc5a962e5aa9de5f4cc1ae234cf1ed31d Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Sat, 13 May 2023 15:58:00 +0300
Subject: [PATCH] Start switching webhook secrets to not contain room ID

---
 github/api/webhook.py     |  6 +++++-
 github/bot.py             |  1 +
 github/webhook/manager.py | 24 ++++++++++++++++++++++--
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/github/api/webhook.py b/github/api/webhook.py
index fb7d8c4..633bcbf 100644
--- a/github/api/webhook.py
+++ b/github/api/webhook.py
@@ -33,6 +33,7 @@
 
     class WebhookInfo(Protocol):
         secret: str
+        old_secret: str
 
 
     class HandlerFunc(Protocol):
@@ -109,7 +110,10 @@ async def _handle(self, request: web.Request, webhook_info: 'WebhookInfo') -> we
         secret = webhook_info.secret.encode("utf-8")
         digest = f"sha1={hmac.new(secret, text_binary, hashlib.sha1).hexdigest()}"
         if not hmac.compare_digest(signature, digest):
-            return web.Response(status=401, text="Invalid signature")
+            old_secret = webhook_info.old_secret.encode("utf-8")
+            old_digest = f"sha1={hmac.new(old_secret, text_binary, hashlib.sha1).hexdigest()}"
+            if not hmac.compare_digest(signature, old_digest):
+                return web.Response(status=401, text="Invalid signature")
         try:
             data = json.loads(text)
         except json.JSONDecodeError:
diff --git a/github/bot.py b/github/bot.py
index dd1f423..b4aa95b 100644
--- a/github/bot.py
+++ b/github/bot.py
@@ -57,6 +57,7 @@ async def start(self) -> None:
         self.clients.load_db()
 
         self.register_handler_class(self.webhook_receiver)
+        self.register_handler_class(self.webhook_manager)
         self.register_handler_class(self.clients)
         self.register_handler_class(self.commands)
 
diff --git a/github/webhook/manager.py b/github/webhook/manager.py
index dfb6d93..8780235 100644
--- a/github/webhook/manager.py
+++ b/github/webhook/manager.py
@@ -21,7 +21,8 @@
 from sqlalchemy import MetaData, Table, Column, String, Integer, UniqueConstraint, and_
 from sqlalchemy.engine.base import Engine
 
-from mautrix.types import UserID, RoomID
+from mautrix.types import UserID, RoomID, EventType, StateEvent, RoomTombstoneStateEventContent
+from maubot.handlers import event
 
 from ..util import UUIDType
 
@@ -61,13 +62,20 @@ def __setattr__(self, key: str, value: Any) -> None:
         super().__setattr__(key, value)
 
     @property
-    def secret(self) -> str:
+    def old_secret(self) -> str:
         secret = hmac.new(key=self._secret_key, digestmod=hashlib.sha256)
         secret.update(self.id.bytes)
         secret.update(self.user_id.encode("utf-8"))
         secret.update(self.room_id.encode("utf-8"))
         return secret.hexdigest()
 
+    @property
+    def secret(self) -> str:
+        secret = hmac.new(key=self._secret_key, digestmod=hashlib.sha256)
+        secret.update(self.id.bytes)
+        secret.update(self.user_id.encode("utf-8"))
+        return secret.hexdigest()
+
 
 class WebhookManager:
     _table: Table
@@ -99,6 +107,18 @@ def create(self, repo: str, user_id: UserID, room_id: RoomID) -> WebhookInfo:
         self._webhooks[info.id] = info
         return info
 
+    @event.on(EventType.ROOM_TOMBSTONE)
+    async def handle_room_upgrade(self, evt: StateEvent) -> None:
+        assert isinstance(evt.content, RoomTombstoneStateEventContent)
+        self._db.execute(
+            self._table.update()
+                .where(self._table.c.room_id == evt.room_id)
+                .values(room_id=evt.content.replacement_room)
+        )
+        for webhook in self._webhooks.values():
+            if webhook.room_id == evt.room_id:
+                webhook.room_id = evt.content.replacement_room
+
     def set_github_id(self, info: WebhookInfo, github_id: int) -> WebhookInfo:
         self._db.execute(self._table.update()
                          .where(self._table.c.id == info.id)