Graphql Introspection in Flask with Cockroachdb

GraphQL introspection in a Flask application that uses CockroachDB can expose your schema, data structure, and operational details to unauthenticated attackers. Introspection is a core GraphQL feature that allows clients to query the schema for types, queries, and mutations. While valuable for development, leaving introspection enabled in production is a significant security risk.

When Flask serves a GraphQL endpoint backed by CockroachDB, introspection responses reveal table-like structures, field names, and relationship patterns that map closely to your underlying database schema. An attacker can use introspection queries to enumerate entities that align with CockroachDB tables and columns, effectively turning your GraphQL layer into a schema discovery mechanism. This becomes especially dangerous if role-based or row-level security is not consistently enforced, as the GraphQL API may leak what the database is allowed to store.

The risk is compounded when the Flask GraphQL server does not enforce authentication for introspection queries. Without authentication, an unauthenticated attacker can run the standard __schema query to retrieve full type information. If the naming conventions in your GraphQL types mirror CockroachDB identifiers (for example, users, transactions, or audit_logs), an attacker gains a clear map of your data model. This mapping facilitates further attacks such as BOLA/IDOR or targeted injection attempts, increasing the likelihood of successful exploitation.

Insecure default configurations in some Flask development setups may also allow introspection without explicit opt-in, while production deployments sometimes forget to disable it. CockroachDB’s strong consistency and SQL interface do not inherently protect against this; the exposure happens at the GraphQL abstraction layer. Therefore, the combination of a permissive Flask GraphQL server, an introspective GraphQL schema, and a CockroachDB backend can unintentionally disclose sensitive structural information without requiring any database credentials.

To secure a Flask GraphQL service backed by CockroachDB, you must disable introspection for non-developer contexts and enforce strict access controls. Below are concrete, realistic code examples you can apply in your Flask application.

1. Disable introspection in production

Using graphql-core, you can disable introspection by providing a custom schema or wrapping the default introspection resolver. This example shows how to disable introspection entirely for production environments:

from graphql import GraphQLSchema, graphql_sync
from graphql.type import GraphQLObjectType, GraphQLField, GraphQLString
from flask import Flask, request, jsonify

app = Flask(__name__)

# Define a minimal schema without exposing introspection in production
query_type = GraphQLObjectType(
    name='Query',
    fields={
        'health': GraphQLField(
            GraphQLString,
            resolve=lambda obj, info: 'ok'
        )
    }
)

schema = GraphQLSchema(query=query_type)

@app.route('/graphql', methods=['POST'])
def graphql_server():
    data = request.get_json(force=True)
    query = data.get('query')

    # Block introspection queries in production
    if 'introspection' in query and app.config.get('ENV') == 'production':
        return jsonify({'errors': [{'message': 'Introspection is disabled'}]}), 400

    result = graphql_sync(schema, query)
    return jsonify(result.to_dict())

2. Parameterized CockroachDB queries with SQLAlchemy

When interacting with CockroachDB, always use parameterized queries to prevent injection. Here is an example using SQLAlchemy with Flask and CockroachDB:

from flask import Flask, request, jsonify
from sqlalchemy import create_engine, text
import os

app = Flask(__name__)

# CockroachDB connection string (use secure credentials in practice)
engine = create_engine(os.getenv('COCKROACH_DATABASE_URL'))

@app.route('/users/', methods=['GET'])
def get_user(user_id):
    with engine.connect() as conn:
        # Use text() and parameters to avoid injection
        result = conn.execute(text('SELECT id, username, email FROM users WHERE id = :uid'), {'uid': user_id})
        rows = result.fetchall()
        if not rows:
            return jsonify({'error': 'User not found'}), 404
        return jsonify([dict(row._mapping) for row in rows])

3. Apply schema directives or field-level permissions

You can define custom rules to restrict introspection based on roles or environment. For example, allow introspection only for authenticated admin users:

from flask_jwt_extended import jwt_required, get_jwt_identity

@app.route('/graphql', methods=['POST'])
def graphql_server():
    data = request.get_json(force=True)
    query = data.get('query')

    # Require authentication to run introspection
    if '__schema' in query or '__type' in query:
        if not jwt_required():  # simplified check
            return jsonify({'errors': [{'message': 'Authentication required'}]}), 401
        # Optionally restrict by role
        identity = get_jwt_identity()
        if not is_admin(identity):
            return jsonify({'errors': [{'message': 'Insufficient permissions'}]}), 403

    result = graphql_sync(schema, query)
    return jsonify(result.to_dict())

4. Use environment-aware configuration

Ensure your Flask configuration distinguishes between development and production:

app.config.from_mapping(
    ENV=os.getenv('FLASK_ENV', 'development'),
    DEBUG=False if os.getenv('FLASK_ENV') == 'production' else True,
)