aminghadersohi commented on code in PR #37972: URL: https://github.com/apache/superset/pull/37972#discussion_r2806712334
########## 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): + """ + JWT verifier that provides specific error messages for each + validation failure instead of generic "invalid_token". + + Overrides load_access_token() to perform step-by-step validation, + storing the specific failure reason in a ContextVar that the + custom BearerAuthBackend reads to return a descriptive 401 response. + """ + + async def load_access_token(self, token: str) -> AccessToken | None: # noqa: C901 + """ + Validate a JWT bearer token with detailed error reporting. + + Each validation step stores a specific failure reason in the + _jwt_failure_reason ContextVar before returning None. + """ + # Reset any previous failure reason + _jwt_failure_reason.set(None) + + try: + # Step 1: Decode header and check algorithm + try: + header = self._decode_token_header(token) + except (ValueError, DecodeError) as e: + reason = f"Malformed token header: {e}" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + token_alg = header.get("alg") + if self.algorithm and token_alg != self.algorithm: + reason = ( + f"Algorithm mismatch: token uses '{token_alg}', " + f"expected '{self.algorithm}'" + ) + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Step 2: Get verification key (static or JWKS) + try: + verification_key = await self._get_verification_key(token) + except ValueError as e: + reason = f"Failed to get verification key: {e}" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Step 3: Decode and verify signature + try: + claims = self.jwt.decode(token, verification_key) + except BadSignatureError: + reason = "Signature verification failed" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + except ExpiredTokenError: + reason = "Token has expired (detected during decode)" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + except JoseError as e: + reason = f"Token decode failed: {e}" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Extract client ID for logging + client_id = ( + claims.get("client_id") + or claims.get("azp") + or claims.get("sub") + or "unknown" + ) + + # Step 4: Check expiration + exp = claims.get("exp") + if exp and exp < time.time(): + reason = f"Token expired for client '{client_id}'" + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Step 5: Validate issuer + if self.issuer: + iss = claims.get("iss") + if isinstance(self.issuer, list): + issuer_valid = iss in self.issuer + else: + issuer_valid = iss == self.issuer + + if not issuer_valid: + reason = ( + f"Issuer mismatch: token has '{iss}', expected '{self.issuer}'" + ) + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Step 6: Validate audience + if self.audience: + aud = claims.get("aud") + if isinstance(self.audience, list): + if isinstance(aud, list): + audience_valid = any( + expected in aud + for expected in cast(list[str], self.audience) + ) + else: + audience_valid = aud in cast(list[str], self.audience) + else: + if isinstance(aud, list): + audience_valid = self.audience in aud + else: + audience_valid = aud == self.audience + + if not audience_valid: + reason = ( + f"Audience mismatch: token has '{aud}', " + f"expected '{self.audience}'" + ) + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # Step 7: Check required scopes + scopes = self._extract_scopes(claims) + if self.required_scopes: + token_scopes = set(scopes) + required = set(self.required_scopes) + if not required.issubset(token_scopes): + missing = required - token_scopes + reason = ( + f"Missing required scopes: {missing}. Token has: {token_scopes}" + ) + _jwt_failure_reason.set(reason) + logger.warning(reason) + return None + + # All validations passed Review Comment: Fixed in 74354ee — narrowed to `(ValueError, JoseError, KeyError, AttributeError, TypeError)` which covers the specific exception types that can occur from JWT library operations, dict access, and type conversion. -- 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]
