Privilege Escalation in Flask with Cockroachdb

Privilege Escalation occurs when an attacker can gain elevated access beyond what their identity or role permits. In a Flask application using CockroachDB, the risk often arises from how queries are built, how roles are enforced, and how connection credentials are managed. CockroachDB implements PostgreSQL wire protocol and supports roles with granular privileges, but Flask code that does not enforce authorization checks or that dynamically builds SQL can bypass intended access controls.

One common pattern is constructing SQL by string interpolation with user input, such as an identifier or role name taken from request parameters. For example, if an endpoint accepts a table_name or role from the client and embeds it directly into a query, an attacker can supply crafted input to change the query’s semantics. In CockroachDB, this can allow an attacker to reference system tables or other schemas to which they should not have access, effectively escalating their permissions.

Flask applications often manage database sessions at the request level. If session handling does not properly scope permissions per request and relies on a shared, highly privileged connection, a compromised endpoint can be used to run statements as a higher-privileged user. CockroachDB’s role-based access control can mitigate this when roles are strictly enforced, but Flask code that does not validate authorization per operation can negate those controls. For instance, an endpoint intended to read user profile data might inadvertently execute administrative statements if the application logic does not enforce the principle of least privilege.

Another vector involves authentication and connection credentials. If Flask applications embed CockroachDB credentials in configuration files that are shared across roles or if they fail to rotate credentials, an attacker who compromises a lower-privilege service can reuse those credentials to perform actions beyond the intended scope. Additionally, CockroachDB supports multiple authentication methods, and Flask code that does not explicitly require secure authentication mechanisms may expose an unauthenticated or weakly authenticated path to sensitive operations.

Consider an endpoint that dynamically selects a column or table based on user input without validating against an allowlist. An attacker may supply a column name that references sensitive system columns in CockroachDB’s system tables, extracting metadata or configuration details that enable further escalation. When combined with missing authorization checks at the service layer, this creates a pathway for vertical or horizontal privilege escalation.

Remediation focuses on strict input validation, parameterized queries, and role-based access control at the application layer. Never embed user input directly into SQL identifiers or DDL statements. Use parameterized queries for data values and enforce allowlists for schema and object names. Below are concrete examples of secure patterns when working with CockroachDB in Flask.

First, establish a database connection using secure configuration and avoid embedding credentials in application code. Use environment variables and ensure the CockroachDB role used by Flask has the minimum required privileges.

import os
import psycopg2
from flask import Flask, request, g

app = Flask(__name__)

def get_db():
    if 'db' not in g:
        g.db = psycopg2.connect(
            dbname=os.getenv('COCKROACH_DB'),
            user=os.getenv('COCKROACH_USER'),
            password=os.getenv('COCKROACH_PASSWORD'),
            host=os.getenv('COCKROACH_HOST'),
            port=os.getenv('COCKROACH_PORT', '26257'),
            sslmode=os.getenv('COCKROACH_SSLMODE', 'require')
        )
    return g.db

@app.teardown_appcontext
def close_db(error):
    db = g.pop('db', None)
    if db is not None:
        db.close()

Second, when querying user-provided identifiers, use an allowlist and map them to safe values rather than interpolating them. For example, if a client specifies a profile table name, validate it against a predefined set:

ALLOWED_PROFILE_TABLES = {'public.profiles', 'tenant_data.profiles'}

@app.route('/profile')
def get_profile():
    table = request.args.get('table', 'public.profiles')
    if table not in ALLOWED_PROFILE_TABLES:
        return {'error': 'invalid table'}, 400
    
    conn = get_db()
    cur = conn.cursor()
    # Safe: table name is validated, not interpolated
    cur.execute(f'SELECT id, display_name FROM {table} WHERE user_id = %s', (current_user_id,))
    rows = cur.fetchall()
    return [dict(id=r[0], name=r[1]) for r in rows]

Third, for operations that require dynamic columns, use the information schema to validate existence and accessibility before constructing queries, rather than relying on raw user input:

@app.route('/user-data')
def get_user_data():
    column = request.args.get('column', 'email')
    conn = get_db()
    cur = conn.cursor()
    
    # Validate column against information schema
    cur.execute("""
        SELECT column_name FROM information_schema.columns 
        WHERE table_schema = 'public' AND table_name = 'users' AND column_name = %s
    """, (column,))
    if not cur.fetchone():
        return {'error': 'invalid column'}, 400
    
    # Safe: column has been validated
    cur.execute('SELECT id, %s FROM users WHERE id = %s', (column, current_user_id))
    row = cur.fetchone()
    return {'id': row[0], column: row[1]}

Fourth, enforce role-based access at the Flask route level and ensure the CockroachDB role used matches the intended permissions. Avoid using a single highly privileged role for all operations. Instead, define routes with explicit checks and use connection parameters that align with least privilege.

def require_role(required_role):
    def decorator(f):
        @wraps(f)
        def wrapped(*args, **kwargs):
            if get_current_role() != required_role:
                return {'error': 'forbidden'}, 403
            return f(*args, **kwargs)
        return wrapped
    return decorator

@app.route('/admin/reset')
@require_role('admin')
def admin_reset():
    conn = get_db()
    cur = conn.cursor()
    cur.execute('RESET ALL')  # Example admin-only operation
    return {'status': 'ok'}

These patterns reduce the attack surface by ensuring that CockroachDB interactions are constrained, validated, and aligned with the application’s authorization model, minimizing opportunities for privilege escalation through the Flask layer.