flawopen.com/bola-idor/Python

● CWE-639 · Критический
Исследования · FlawOpen

Нарушение авторизации на уровне объектов (BOLA / IDOR) в Python

Руководство по устранению уязвимостей BOLA (CWE-639) и IDOR в приложениях на FastAPI и Python путем жесткой привязки SQL-запросов к организации аутентифицированного пользователя.

💡 Простыми словами (ELI5)

Гостиничный ключ от номера 204, который открывает номер 205, если просто подправить цифру на замке. Отель проверил, что вы гость (аутентификация), но не проверил, ваш ли это номер (авторизация объекта).

Ключевые понятия и термины

Authentication vs. Authorization
Технический термин (Authentication vs. Authorization): Authentication confirms WHO the user is (valid login). Authorization confirms WHAT resources that specific user is permitted to view or modify.
BOLA (Broken Object Level Authorization)
Технический термин (BOLA (Broken Object Level Authorization)): The #1 OWASP API vulnerability where an endpoint exposes an object reference (e.g. /api/invoices/1042) without verifying tenant ownership.
IDOR (Insecure Direct Object Reference)
Технический термин (IDOR (Insecure Direct Object Reference)): The broader vulnerability class (CWE-639) where internal implementation objects are exposed directly to users without access control checks.
Tenancy Scope Injection
Технический термин (Tenancy Scope Injection): An architectural pattern where database queries automatically enforce WHERE organization_id = :auth_user_org_id at the ORM layer.
Non-Enumerable Identifiers (UUIDv4)
Технический термин (Non-Enumerable Identifiers (UUIDv4)): Using cryptographically random 128-bit identifiers instead of sequential auto-incrementing integers (1, 2, 3...) to prevent predictable enumeration.

Пошаговый сценарий атаки

Step 1

Legitimate Sign-In

An attacker creates a legitimate account on the platform and receives a valid JWT authentication bearer token.

Step 2

Resource Inspection

The attacker accesses their own billing invoice via GET /api/invoices/1042 and observes sequential database identifiers in use.

Step 3

Identifier Perturbation

The attacker modifies the URL to request GET /api/invoices/1041 using their own valid authentication token.

Step 4

Flawed Controller Logic

The FastAPI backend confirms the token is valid, but queries the database solely by Invoice.id == 1041 without verifying tenant ownership.

Step 5

Cross-Tenant Exfiltration

The server returns confidential invoice records, billing details, and personal data belonging to another organization.

Step 6

Automated Harvest

The attacker scripts a loop iterating over IDs 1 through 100,000, draining the entire multi-tenant database.

Исходный код: Уязвимый vs Защищённый вариант

✕ УЯЗВИМАЯ РЕАЛИЗАЦИЯ
# VULNERABLE: Verifies user login, but queries object solely by client ID
from fastapi import FastAPI, Depends, HTTPException, status
from sqlalchemy.orm import Session

@app.get("/api/invoices/{invoice_id}")
def get_invoice(invoice_id: int, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    # Flaw: Attacker passes invoice_id belonging to another tenant
    invoice = db.query(Invoice).filter(Invoice.id == invoice_id).first()
    
    if not invoice:
        raise HTTPException(status_code=404, detail="Invoice not found")
        
    # Leaks confidential billing records of competitor organizations!
    return invoice
✓ БЕЗОПАСНЫЙ ИСПРАВЛЕННЫЙ ВАРИАНТ
# HARDENED: Query is strictly bound to the authenticated tenant's organization ID
from fastapi import FastAPI, Depends, HTTPException, status
from sqlalchemy.orm import Session

@app.get("/api/invoices/{invoice_id}")
def get_invoice(invoice_id: int, current_user: User = Depends(get_current_user), db: Session = Depends(get_db)):
    # Defense-in-depth: query filters by BOTH invoice_id AND authenticated organization_id
    invoice = db.query(Invoice).filter(
        Invoice.id == invoice_id,
        Invoice.organization_id == current_user.organization_id
    ).first()
    
    if not invoice:
        # Return 404 rather than 403 to prevent object existence enumeration
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Invoice not found")
        
    return invoice

Чек-лист по защите системы для инженеров

References