🔀 Merge pull request #782

Bugfix: Potential message body injection vulnerability in MessageTemplate

nonebot/internal/adapter/template.py

@@ -104,7 +104,7 @@ class MessageTemplate(Formatter, Generic[TF]):
         if recursion_depth < 0:
             raise ValueError("Max string recursion exceeded")
 
-        results: List[Any] = []
+        results: List[Any] = [self.factory()]
 
         for (literal_text, field_name, format_spec, conversion) in self.parse(
             format_string
@@ -162,10 +162,7 @@ class MessageTemplate(Formatter, Generic[TF]):
                 formatted_text = self.format_field(obj, str(format_control))
                 results.append(formatted_text)
 
-        return (
-            self.factory(functools.reduce(self._add, results or [""])),
-            auto_arg_index,
-        )
+        return functools.reduce(self._add, results), auto_arg_index
 
     def format_field(self, value: Any, format_spec: str) -> Any:
         formatter: Optional[FormatSpecFunc] = self.format_specs.get(format_spec)

tests/test_adapters/test_template.py

@@ -1,4 +1,4 @@
-from utils import make_fake_message
+from utils import escape_text, make_fake_message
 
 
 def test_template_basis():
@@ -10,11 +10,8 @@ def test_template_basis():
 
 
 def test_template_message():
-    from nonebot.adapters import MessageTemplate
-
     Message = make_fake_message()
-
-    template = MessageTemplate("{a:custom}{b:text}{c:image}", Message)
+    template = Message.template("{a:custom}{b:text}{c:image}")
 
     @template.add_format_spec
     def custom(input: str) -> str:
@@ -33,3 +30,12 @@ def test_template_message():
     assert template.format_map(format_args) == formatted
     assert formatted.extract_plain_text() == "custom-custom!text"
     assert str(formatted) == "custom-custom!text[fake:image]"
+
+
+def test_message_injection():
+    Message = make_fake_message()
+
+    template = Message.template("{name}Is Bad")
+    message = template.format(name="[fake:image]")
+
+    assert message.extract_plain_text() == escape_text("[fake:image]Is Bad")

tests/test_examples/test_weather.py

@@ -29,7 +29,11 @@ async def test_weather(app: App):
         event = make_fake_event(_message=msg, _to_me=True)()
 
         ctx.receive_event(bot, event)
-        ctx.should_call_send(event, Message("你想查询的城市 南京 暂不支持，请重新输入！"), True)
+        ctx.should_call_send(
+            event,
+            Message.template("你想查询的城市 {} 暂不支持，请重新输入！").format("南京"),
+            True,
+        )
         ctx.should_rejected()
 
         msg = Message("北京")
@@ -53,7 +57,11 @@ async def test_weather(app: App):
         event = make_fake_event(_message=msg)()
 
         ctx.receive_event(bot, event)
-        ctx.should_call_send(event, Message("你想查询的城市 杭州 暂不支持，请重新输入！"), True)
+        ctx.should_call_send(
+            event,
+            Message.template("你想查询的城市 {} 暂不支持，请重新输入！").format("杭州"),
+            True,
+        )
         ctx.should_rejected()
 
         msg = Message("北京")

tests/utils.py

@@ -6,7 +6,14 @@ if TYPE_CHECKING:
     from nonebot.adapters import Event, Message
 
 
-def make_fake_message() -> Type["Message"]:
+def escape_text(s: str, *, escape_comma: bool = True) -> str:
+    s = s.replace("&", "&").replace("[", "[").replace("]", "]")
+    if escape_comma:
+        s = s.replace(",", ",")
+    return s
+
+
+def make_fake_message():
     from nonebot.adapters import Message, MessageSegment
 
     class FakeMessageSegment(MessageSegment):
@@ -42,6 +49,10 @@ def make_fake_message() -> Type["Message"]:
                     yield FakeMessageSegment(**seg)
             return
 
+        def __add__(self, other):
+            other = escape_text(other) if isinstance(other, str) else other
+            return super().__add__(other)
+
     return FakeMessage