test_malformed_input.py•6.45 kB
# Claude Debug
"""Test for HackerOne vulnerability report #3156202 - malformed input DOS."""
from typing import Any
import anyio
import pytest
from mcp.server.models import InitializationOptions
from mcp.server.session import ServerSession
from mcp.shared.message import SessionMessage
from mcp.types import (
INVALID_PARAMS,
JSONRPCError,
JSONRPCMessage,
JSONRPCRequest,
ServerCapabilities,
)
@pytest.mark.anyio
async def test_malformed_initialize_request_does_not_crash_server():
"""
Test that malformed initialize requests return proper error responses
instead of crashing the server (HackerOne #3156202).
"""
# Create in-memory streams for testing
read_send_stream, read_receive_stream = anyio.create_memory_object_stream[
SessionMessage | Exception
](10)
write_send_stream, write_receive_stream = anyio.create_memory_object_stream[SessionMessage](10)
try:
# Create a malformed initialize request (missing required params field)
malformed_request = JSONRPCRequest(
jsonrpc="2.0",
id="f20fe86132ed4cd197f89a7134de5685",
method="initialize",
# params=None # Missing required params field
)
# Wrap in session message
request_message = SessionMessage(message=JSONRPCMessage(malformed_request))
# Start a server session
async with ServerSession(
read_stream=read_receive_stream,
write_stream=write_send_stream,
init_options=InitializationOptions(
server_name="test_server",
server_version="1.0.0",
capabilities=ServerCapabilities(),
),
):
# Send the malformed request
await read_send_stream.send(request_message)
# Give the session time to process the request
await anyio.sleep(0.1)
# Check that we received an error response instead of a crash
try:
response_message = write_receive_stream.receive_nowait()
response = response_message.message.root
# Verify it's a proper JSON-RPC error response
assert isinstance(response, JSONRPCError)
assert response.jsonrpc == "2.0"
assert response.id == "f20fe86132ed4cd197f89a7134de5685"
assert response.error.code == INVALID_PARAMS
assert "Invalid request parameters" in response.error.message
# Verify the session is still alive and can handle more requests
# Send another malformed request to confirm server stability
another_malformed_request = JSONRPCRequest(
jsonrpc="2.0",
id="test_id_2",
method="tools/call",
# params=None # Missing required params
)
another_request_message = SessionMessage(
message=JSONRPCMessage(another_malformed_request)
)
await read_send_stream.send(another_request_message)
await anyio.sleep(0.1)
# Should get another error response, not a crash
second_response_message = write_receive_stream.receive_nowait()
second_response = second_response_message.message.root
assert isinstance(second_response, JSONRPCError)
assert second_response.id == "test_id_2"
assert second_response.error.code == INVALID_PARAMS
except anyio.WouldBlock:
pytest.fail("No response received - server likely crashed")
finally:
# Close all streams to ensure proper cleanup
await read_send_stream.aclose()
await write_send_stream.aclose()
await read_receive_stream.aclose()
await write_receive_stream.aclose()
@pytest.mark.anyio
async def test_multiple_concurrent_malformed_requests():
"""
Test that multiple concurrent malformed requests don't crash the server.
"""
# Create in-memory streams for testing
read_send_stream, read_receive_stream = anyio.create_memory_object_stream[
SessionMessage | Exception
](100)
write_send_stream, write_receive_stream = anyio.create_memory_object_stream[SessionMessage](100)
try:
# Start a server session
async with ServerSession(
read_stream=read_receive_stream,
write_stream=write_send_stream,
init_options=InitializationOptions(
server_name="test_server",
server_version="1.0.0",
capabilities=ServerCapabilities(),
),
):
# Send multiple malformed requests concurrently
malformed_requests: list[SessionMessage] = []
for i in range(10):
malformed_request = JSONRPCRequest(
jsonrpc="2.0",
id=f"malformed_{i}",
method="initialize",
# params=None # Missing required params
)
request_message = SessionMessage(message=JSONRPCMessage(malformed_request))
malformed_requests.append(request_message)
# Send all requests
for request in malformed_requests:
await read_send_stream.send(request)
# Give time to process
await anyio.sleep(0.2)
# Verify we get error responses for all requests
error_responses: list[Any] = []
try:
while True:
response_message = write_receive_stream.receive_nowait()
error_responses.append(response_message.message.root)
except anyio.WouldBlock:
pass # No more messages
# Should have received 10 error responses
assert len(error_responses) == 10
for i, response in enumerate(error_responses):
assert isinstance(response, JSONRPCError)
assert response.id == f"malformed_{i}"
assert response.error.code == INVALID_PARAMS
finally:
# Close all streams to ensure proper cleanup
await read_send_stream.aclose()
await write_send_stream.aclose()
await read_receive_stream.aclose()
await write_receive_stream.aclose()