Information Disclosure in Flask with Cockroachdb

Information disclosure occurs when a Flask application using CockroachDB unintentionally exposes sensitive data through its API responses, error messages, or configuration. This combination is risky because Flask’s default development server and CockroachDB’s wire protocol can reveal stack traces, schema details, or data when errors are not handled explicitly.

When a Flask route queries CockroachDB using raw SQL or an ORM and does not sanitize inputs, an attacker can supply malformed or malicious payloads that trigger verbose errors. For example, a missing index or type mismatch in CockroachDB may produce detailed error messages that include table names, column definitions, or internal SQL logic. If Flask returns these errors directly to the client, sensitive schema information is disclosed.

Additionally, if the Flask app exposes database connection parameters—such as host, port, or database name—through debug pages or misconfigured logging, an attacker can learn infrastructure details that facilitate further attacks. CockroachDB’s distributed nature means that diagnostic endpoints or logs might include node addresses or transaction IDs, which should not be surfaced to unauthenticated users.

Common OWASP API Top 10 risks related to information disclosure include Improper Error Handling (API1004) and Excessive Data Exposure (API1005). In this stack, a typical vulnerable pattern is a Flask route that executes a CockroachDB query without prepared statements and returns the full exception object to the client.

Real-world examples include endpoints that accept user-supplied identifiers and directly interpolate them into SQL strings. If CockroachDB rejects the query due to constraint violations or type errors, the traceback may include file paths, line numbers, and variable contents. Without proper error handling and response normalization, the API becomes an unintentional source of intelligence for an attacker.

To mitigate information disclosure when using CockroachDB with Flask, implement strict error handling, parameterized queries, and response normalization. Below are concrete, secure code examples.

1. Parameterized Queries with psycopg2 (CockroachDB wire protocol compatible)

import psycopg2
from flask import Flask, jsonify

app = Flask(__name__)

# Secure: parameterized query with explicit error handling
@app.route('/user/')
def get_user(user_id):
    conn = psycopg2.connect(
        host='localhost',
        port=26257,
        dbname='mydb',
        user='app_user',
        password='secure_password'
    )
    try:
        with conn.cursor() as cur:
            # Use placeholders to prevent SQL injection and avoid verbose errors
            cur.execute('SELECT id, username, email FROM users WHERE id = %s', (user_id,))
            row = cur.fetchone()
            if row:
                return jsonify({'id': row[0], 'username': row[1], 'email': row[2]})
            return jsonify({'error': 'User not found'}), 404
    except psycopg2.Error as e:
        # Log the full error internally; return generic message to client
        app.logger.error(f'Database error: {e}')
        return jsonify({'error': 'Internal server error'}), 500
    finally:
        conn.close()

2. Centralized Error Handler to Prevent Schema Leakage

from flask import Flask, jsonify

app = Flask(__name__)

@app.errorhandler(500)
def handle_500(e):
    # Ensure no stack trace or CockroachDB details are returned
    app.logger.exception('Unhandled exception')
    return jsonify({'error': 'An unexpected error occurred'}), 500

@app.errorhandler(404)
def handle_404(e):
    return jsonify({'error': 'Not found'}), 404

3. Secure Logging and Configuration

Ensure that CockroachDB connection details are not logged or exposed. Use environment variables and avoid printing debug information in production.

import os
from flask import Flask

app = Flask(__name__)

# Load from environment; do not hardcode
DB_HOST = os.getenv('COCKROACH_HOST', 'localhost')
DB_PORT = os.getenv('COCKROACH_PORT', '26257')
DB_NAME = os.getenv('COCKROACH_DB', 'mydb')
DB_USER = os.getenv('COCKROACH_USER', 'app_user')
DB_PASSWORD = os.getenv('COCKROACH_PASSWORD', '')

# Example of safe connection setup
@app.before_request
def validate_config():
    if not all([DB_HOST, DB_PORT, DB_NAME, DB_USER, DB_PASSWORD]):
        raise RuntimeError('Database configuration is incomplete')

4. Input Validation and Schema-Aware Responses

Validate incoming data against expected types and ranges before sending to CockroachDB. This reduces the chance of database-specific errors that could disclose schema details.

from flask import request, jsonify

@app.route('/create', methods=['POST'])
def create_item():
    data = request.get_json()
    if not isinstance(data.get('email'), str) or '@' not in data.get('email', ''):
        return jsonify({'error': 'Invalid email'}), 400
    # Proceed with parameterized query
    return jsonify({'status': 'ok'})