Antonio-RiveroMartnez commented on code in PR #37972: URL: https://github.com/apache/superset/pull/37972#discussion_r2832561251
########## superset/mcp_service/jwt_verifier.py: ########## @@ -0,0 +1,305 @@ +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you under the Apache License, Version 2.0 (the +# "License"); you may not use this file except in compliance +# with the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, +# software distributed under the License is distributed on an +# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +# KIND, either express or implied. See the License for the +# specific language governing permissions and limitations +# under the License. +""" +Detailed JWT verification for the MCP service. + +Provides step-by-step JWT validation with specific error messages +instead of the generic "invalid_token" response from the base JWTVerifier. +""" + +import base64 +import logging +import time +from contextvars import ContextVar +from typing import Any, cast + +from authlib.jose.errors import ( + BadSignatureError, + DecodeError, + ExpiredTokenError, + JoseError, +) +from fastmcp.server.auth.auth import AccessToken +from fastmcp.server.auth.providers.jwt import JWTVerifier +from mcp.server.auth.middleware.auth_context import AuthContextMiddleware +from mcp.server.auth.middleware.bearer_auth import BearerAuthBackend +from starlette.authentication import AuthenticationError +from starlette.middleware import Middleware +from starlette.middleware.authentication import AuthenticationMiddleware +from starlette.requests import HTTPConnection +from starlette.responses import JSONResponse + +from superset.utils import json + +logger = logging.getLogger(__name__) + +# Thread-safe storage for the specific JWT failure reason. +# Set by DetailedJWTVerifier.load_access_token() on failure, +# read by DetailedBearerAuthBackend.authenticate() to raise +# an AuthenticationError with the specific reason. +_jwt_failure_reason: ContextVar[str | None] = ContextVar( + "_jwt_failure_reason", default=None +) + + +def _sanitize_header_value(value: str) -> str: + """Sanitize a string for safe use in HTTP header values. + + Removes/replaces characters that could enable header injection + (CR, LF, quotes) from attacker-controlled JWT claims. + """ + return value.replace("\r", " ").replace("\n", " ").replace('"', "'") + + +def _json_auth_error_handler( + conn: HTTPConnection, exc: AuthenticationError +) -> JSONResponse: + """Return a JSON 401 response with the specific JWT failure reason.""" + reason = str(exc) + safe_reason = _sanitize_header_value(reason) + return JSONResponse( + status_code=401, + content={ + "error": "invalid_token", + "error_description": reason, + }, + headers={ + "WWW-Authenticate": f'Bearer error="invalid_token", ' + f'error_description="{safe_reason}"', + }, + ) + + +class DetailedBearerAuthBackend(BearerAuthBackend): + """ + Bearer auth backend that raises AuthenticationError with specific + JWT failure reasons instead of silently returning None. + """ + + async def authenticate(self, conn: HTTPConnection) -> tuple[Any, Any] | None: + result = await super().authenticate(conn) + + if result is not None: + # Clear any stale failure reason on success + _jwt_failure_reason.set(None) + return result + + # Check if there's a Bearer token present - if so, there was a + # validation failure we can report with a specific reason + auth_header = next( + ( + conn.headers.get(key) + for key in conn.headers + if key.lower() == "authorization" + ), + None, + ) + if auth_header and auth_header.lower().startswith("bearer "): + reason = _jwt_failure_reason.get() + if reason: + _jwt_failure_reason.set(None) + raise AuthenticationError(reason) + + return None + + +class DetailedJWTVerifier(JWTVerifier): Review Comment: Seems like this is going against the standard ([RFC 6750](https://datatracker.ietf.org/doc/html/rfc6750#section-3.1)). Verbose JWT errors led to real exploits. [CVE-2022-29266](https://nvd.nist.gov/vuln/detail/cve-2022-29266) [CVE-2019-7644](https://nvd.nist.gov/vuln/detail/CVE-2019-7644), should we instead have some way to log debug messages server side as a config option? `MCP_JWT_DEBUG_ERRORS` but still the client only knows about a generic error? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
