Fix #592

Author: RobertoPrevato

CHANGELOG.md

@@ -40,6 +40,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Correct bug that prevented request body input to be mapped properly to
   a `list` using the default logic.
 - Upgrade `pytest-asyncio` to the latest version. Fix [#596](https://github.com/Neoteroi/BlackSheep/issues/596).
+- Fix a Cython segmentation fault happening when the user defines an exception handler
+  with a wrong signature ([#592](https://github.com/Neoteroi/BlackSheep/issues/592)),
+  or that contains a bug and causes exceptions itself.
+  Replace the Application `exception_handlers` dictionary with a user defined
+  dictionary that validates values, and change a piece of code that causes
+  a recursive error when an exception handler itself is buggy.
+- Fix `license` field in `pyproject.toml`.
 
 ## [2.4.0] - 2025-06-22
 

blacksheep/baseapp.pxd

@@ -12,7 +12,7 @@ cdef class BaseApplication:
     cdef public bint show_error_details
     cdef readonly object router
     cdef readonly object logger
-    cdef public dict exceptions_handlers
+    cdef public object exceptions_handlers
     cpdef object get_http_exception_handler(self, HTTPException http_exception)
     cdef object get_exception_handler(self, Exception exception, type stop_at)
     cdef bint is_handled_exception(self, Exception exception)

blacksheep/baseapp.py

@@ -1,8 +1,17 @@
 import http
+import inspect
 import logging
+from collections import UserDict
+
+from blacksheep.server.errors import ServerErrorDetailsHandler
 
 from .contents import Content, TextContent
-from .exceptions import HTTPException, InternalServerError, NotFound
+from .exceptions import (
+    HTTPException,
+    InternalServerError,
+    InvalidExceptionHandler,
+    NotFound,
+)
 from .messages import Response
 from .utils import get_class_instance_hierarchy
 
@@ -12,6 +21,21 @@
     ValidationError = None
 
 
+class ExceptionHandlersDict(UserDict):
+
+    def __setitem__(self, key, item) -> None:
+        if not inspect.iscoroutinefunction(item):
+            raise InvalidExceptionHandler()
+        signature = inspect.Signature.from_callable(item)
+        if len(signature.parameters) != 3 and not any(
+            param
+            for param in signature.parameters
+            if signature.parameters[param].kind == 2
+        ):
+            raise InvalidExceptionHandler()
+        return super().__setitem__(key, item)
+
+
 async def handle_not_found(app, request, http_exception):
     return Response(404, content=TextContent("Resource not found"))
 
@@ -58,9 +82,12 @@ def __init__(self, show_error_details, router):
         self.exceptions_handlers = self.init_exceptions_handlers()
         self.show_error_details = show_error_details
         self.logger = get_logger()
+        self.server_error_details_handler: ServerErrorDetailsHandler
 
     def init_exceptions_handlers(self):
-        default_handlers = {404: handle_not_found, 400: handle_bad_request}
+        default_handlers = ExceptionHandlersDict(
+            {404: handle_not_found, 400: handle_bad_request}
+        )
         if ValidationError is not None:
             default_handlers[ValidationError] = (
                 _default_pydantic_validation_error_handler
@@ -159,7 +186,16 @@ async def _apply_exception_handler(self, request, exc, exception_handler):
         try:
             return await exception_handler(self, request, exc)
         except Exception as server_ex:
-            return await self.handle_exception(request, server_ex)
+            # If the exception happens in the user-defined exception handler,
+            # we need to fallback to the default handlers.
+            self.logger.error(
+                "Unhandled exception in exception_handler: %s",
+                exception_handler.__name__,
+            )
+            if self.show_error_details:
+                return self.server_error_details_handler.produce_response(request, exc)
+
+            return await handle_internal_server_error(self, request, server_ex)
 
     async def handle_http_exception(self, request, http_exception):
         exception_handler = self.get_http_exception_handler(http_exception)

blacksheep/baseapp.pyx

@@ -1,8 +1,17 @@
 import http
+import inspect
 import logging
+import sys
+from collections import UserDict
 
 from .contents cimport Content, TextContent
-from .exceptions cimport BadRequest, HTTPException, InternalServerError, NotFound
+from .exceptions cimport (
+    BadRequest,
+    HTTPException,
+    InternalServerError,
+    InvalidExceptionHandler,
+    NotFound,
+)
 from .messages cimport Request, Response
 
 from .utils import get_class_instance_hierarchy
@@ -14,6 +23,26 @@ except ImportError:
     ValidationError = None
 
 
+_IS_PYTHON_39_OR_OLDER = sys.version_info < (3, 10)
+
+
+class ExceptionHandlersDict(UserDict):
+
+    def __setitem__(self, key, item) -> None:
+        # In Python 3.9, inspect.iscoroutinefunction does not return the right
+        # answer for Cython async functions.
+        if not _IS_PYTHON_39_OR_OLDER and not inspect.iscoroutinefunction(item):
+            raise InvalidExceptionHandler()
+        signature = inspect.Signature.from_callable(item)
+        if len(signature.parameters) != 3 and not any(
+            param
+            for param in signature.parameters
+            if signature.parameters[param].kind == 2
+        ):
+            raise InvalidExceptionHandler()
+        return super().__setitem__(key, item)
+
+
 async def handle_not_found(app, Request request, HTTPException http_exception):
     """Default Not Found handler, returns a simple 404 response."""
     return Response(404, content=TextContent("Resource not found"))
@@ -56,10 +85,10 @@ cdef class BaseApplication:
         self.logger = get_logger()
 
     def init_exceptions_handlers(self):
-        default_handlers = {
+        default_handlers = ExceptionHandlersDict({
             404: handle_not_found,
             400: handle_bad_request
-        }
+        })
         if ValidationError is not None:
             default_handlers[ValidationError] = _default_pydantic_validation_error_handler
         return default_handlers
@@ -178,7 +207,13 @@ cdef class BaseApplication:
         try:
             return await exception_handler(self, request, exc)
         except Exception as server_ex:
-            return await self.handle_exception(request, server_ex)
+            # If the exception happens in the user-defined exception handler,
+            # we need to fallback to the default handlers.
+            self.logger.error("Unhandled exception in exception_handler: %s", exception_handler.__name__)
+            if self.show_error_details:
+                return self.server_error_details_handler.produce_response(request, exc)
+
+            return await handle_internal_server_error(self, request, server_ex)
 
     async def handle_http_exception(self, Request request, HTTPException http_exception):
         exception_handler = self.get_http_exception_handler(http_exception)

blacksheep/exceptions.pxd

@@ -35,3 +35,7 @@ cdef class InvalidOperation(Exception):
 
 cdef class FailedRequestError(HTTPException):
     cdef public str data
+
+
+cdef class InvalidExceptionHandler(Exception):
+    pass

blacksheep/exceptions.py

@@ -77,3 +77,13 @@ def __init__(self):
         super().__init__(
             "The message was aborted before the client sent its whole content."
         )
+
+
+class InvalidExceptionHandler(Exception):
+
+    def __init__(self) -> None:
+        super().__init__(
+            "Invalid Exception handler. Exception handlers must be asynchronous "
+            "functions with signature: "
+            "async def handler(app: Application, request: Request, exc: Exception)"
+        )

blacksheep/exceptions.pyi

@@ -69,3 +69,6 @@ class FailedRequestError(HTTPException):
             f"The response status code does not indicate success: {status}. Response body: {data}",
         )
         self.data = data
+
+class InvalidExceptionHandler(Exception):
+    pass

blacksheep/exceptions.pyx

@@ -88,3 +88,13 @@ cdef class MessageAborted(Exception):
         super().__init__(
             "The message was aborted before the client sent its whole content."
         )
+
+
+cdef class InvalidExceptionHandler(Exception):
+
+    def __init__(self) -> None:
+        super().__init__(
+            "Invalid Exception handler. Exception handlers must be asynchronous "
+            "functions with signature: "
+            "async def handler(app: Application, request: Request, exc: Exception)"
+        )

issue592.py

@@ -7,7 +7,8 @@ name = "blacksheep"
 dynamic = ["version"]
 authors = [{ name = "Roberto Prevato", email = "[email protected]" }]
 description = "Fast web framework for Python asyncio"
-license = { file = "LICENSE" }
+license = "MIT"
+license-files = ["LICENSE"]
 readme = "README.md"
 requires-python = ">=3.8"
 classifiers = [