django-access-review

name	django-access-review
description	Reviews Django and DRF access control by tracing whether User A can read, change, or delete User B objects: get_queryset scoping, permission_classes, has_object_permission, tenant managers, and IDOR on pk routes. Use when auditing Django authorization, object permissions, or tenant isolation. Not for Flask/FastAPI auth, generic SAST pattern dumps without a traced flow, or comment-only fixes.
version	1.0.1

Overview

Find access control vulnerabilities by investigating how the codebase answers one question: Can User A access, modify, or delete User B's data?

This skill uses an investigation-driven approach rather than generic pattern matching. Every codebase implements authorization differently; your job is to understand the specific implementation, then find gaps.

When to Use

• You need to review Django or DRF code for access control gaps, IDOR risk, or object-level authorization failures.
• The task involves confirming whether one user can access, modify, or delete another user's data.
• You want an investigation-driven authorization review instead of generic pattern matching.

Prerequisites

• Access to the target Django/DRF codebase.
• PowerShell environment if running search commands on a Windows host.

Procedure

Phase 1: Understand the Authorization Model

Before looking for bugs, answer these questions about the codebase:

1. Where are permission checks implemented?
   • Decorators? (@login_required, @permission_required, custom?)
   • Middleware? (TenantMiddleware, AuthorizationMiddleware?)
   • Base classes? (BaseAPIView, TenantScopedViewSet?)
   • Permission classes? (DRF permission_classes?)
   • Custom mixins? (OwnershipMixin, TenantMixin?)
2. How are queries scoped?
   • Custom managers? (TenantManager, UserScopedManager?)
   • get_queryset() overrides?
   • Middleware that sets query context?
3. What's the ownership model?
   • Single user ownership? (document.owner_id)
   • Organization/tenant ownership? (document.organization_id)
   • Hierarchical? (org -> team -> user -> resource)
   • Role-based within context? (org admin vs member)

Investigation commands (PowerShell):

# Find how auth is typically done
Get-ChildItem -Recurse -Filter *.py | Select-String -Pattern "permission_classes|@login_required|@permission_required" | Select-Object -First 20

# Find base classes that views inherit from
Get-ChildItem -Recurse -Filter *.py | Select-String -Pattern "class Base.*View|class.*Mixin.*:" | Select-Object -First 20

# Find custom managers
Get-ChildItem -Recurse -Filter *.py | Select-String -Pattern "class.*Manager|def get_queryset" | Select-Object -First 20

# Find ownership fields on models
Get-ChildItem -Recurse -Filter models.py | Select-String -Pattern "owner|user_id|organization|tenant" | Select-Object -First 30

Do not proceed until you understand the authorization model.

Phase 2: Map the Attack Surface

Identify endpoints that handle user-specific data:

1. What resources exist?
   • What models contain user data?
   • Which have ownership fields (owner_id, user_id, organization_id)?
   • Which are accessed via ID in URLs or request bodies?
2. What operations are exposed? For each resource, map:
   • List endpoints: what data is returned?
   • Detail/retrieve endpoints: how is the object fetched?
   • Create endpoints: who sets the owner?
   • Update endpoints: can users modify others' data?
   • Delete endpoints: can users delete others' data?
   • Custom actions: what do they access?

Phase 3: Ask Questions and Investigate

For each endpoint that handles user data, ask: "If I'm User A and I know the ID of User B's resource, can I access it?"

Trace the code to answer this:

1. Where does the resource ID enter the system? (URL path, query param, request body)
2. Where is that ID used to fetch data? (Find the ORM query or database call)
3. Between (1) and (2), what checks exist?
   • Is the query scoped to current user?
   • Is there an explicit ownership check?
   • Is there a permission check on the object?
   • Does a base class or mixin enforce access?
4. If you can't find a check, is there one you missed? (Check parent classes, middleware, managers, URL-level decorators)

Follow-Up Questions:

• For list endpoints: Does the query filter to user's data, or return everything?
• For create endpoints: Who sets the owner - the server or the request?
• For bulk operations: Are they scoped to user's data?
• For related resources: If I can access a document, can I access its comments? What if the document belongs to someone else?
• For tenant/org resources: Can User in Org A access Org B's data by changing the org_id in the URL?

Phase 4: Trace Specific Flows

Pick a concrete endpoint and trace it completely.

Example Investigation:

1. Find the view handling GET /api/documents/{pk}/ -> DocumentViewSet.retrieve() in api/views.py
2. Check what DocumentViewSet inherits from -> class DocumentViewSet(viewsets.ModelViewSet) (No custom base class with authorization)
3. Check permission_classes -> permission_classes = [IsAuthenticated] (Only checks login, not ownership)
4. Check get_queryset() -> return Document.objects.all() (Returns ALL documents!)
5. Check for has_object_permission() -> Not implemented
6. Check retrieve() method -> Uses default, which calls get_object() -> get_object() uses get_queryset(), which returns all
7. Conclusion: IDOR - Any authenticated user can access any document

What to look for when tracing:

• Potential gap indicators (investigate further, don't auto-flag):
  • get_queryset() returns .all() or filters without user
  • Direct Model.objects.get(pk=pk) without ownership in query
  • ID comes from request body for sensitive operations
  • Permission class checks auth but not ownership
  • No has_object_permission() and queryset isn't scoped
• Likely safe patterns (but verify the implementation):
  • get_queryset() filters by request.user or user's org
  • Custom permission class with has_object_permission()
  • Base class that enforces scoping
  • Manager that auto-filters

Phase 5: Report Findings

Only report issues you've confirmed through investigation.

Confidence Levels:

• HIGH: Traced the flow, confirmed no check exists. Report with evidence.
• MEDIUM: Check may exist but couldn't confirm. Note for manual verification.
• LOW: Theoretical, likely mitigated. Do not report.

Suggested Fixes Must Enforce, Not Document: A comment or docstring does not enforce authorization. Your suggested fix must include actual code that:

• Validates the user has permission before proceeding
• Raises an exception or returns an error if unauthorized
• Makes unauthorized access impossible, not just discouraged

Example of a BAD fix suggestion:

def get_resource(resource_id):
    # IMPORTANT: Caller must ensure user has access to this resource
    return Resource.objects.get(pk=resource_id)

Example of a GOOD fix suggestion:

def get_resource(resource_id, user):
    resource = Resource.objects.get(pk=resource_id)
    if resource.owner_id != user.id:
        raise PermissionDenied("Access denied")
    return resource

Report Format:

## Access Control Review: [Component]

### Authorization Model
[Brief description of how this codebase handles authorization]

### Findings

#### [IDOR-001] [Title] (Severity: High/Medium)
- **Location**: `path/to/file.py:123`
- **Confidence**: High - confirmed through code tracing
- **The Question**: Can User A access User B's documents?
- **Investigation**:
  1. Traced GET /api/documents/{pk}/ to DocumentViewSet
  2. Checked get_queryset() - returns Document.objects.all()
  3. Checked permission_classes - only IsAuthenticated
  4. Checked for has_object_permission() - not implemented
  5. Verified no relevant middleware or base class checks
- **Evidence**: [Code snippet showing the gap]
- **Impact**: Any authenticated user can read any document by ID
- **Suggested Fix**: [Code that enforces authorization - NOT a comment]

### Needs Manual Verification
[Issues where authorization exists but couldn't confirm effectiveness]

### Areas Not Reviewed
[Endpoints or flows not covered in this review]

Pitfalls

• Suggesting documentation as a fix: Comments and docstrings do not enforce authorization. Always suggest actual code that validates permissions and raises exceptions.
• Auto-flagging patterns: Do not scan for predefined vulnerable patterns without tracing the actual data flow. A .all() query might be safe if a middleware restricts it.
• Missing hidden checks: Authorization might be enforced in parent classes, middleware, or custom managers. Do not conclude a vulnerability exists without checking these layers.
• Ignoring ownership assignment: For create endpoints, verify whether the owner is set server-side or if it can be manipulated via the request body.

Verification

Use this checklist to guide your review, not as a pass/fail checklist:

• I understand how authorization is typically implemented in this codebase
• I've identified the ownership model (user, org, tenant, etc.)
• I've mapped the key endpoints that handle user data
• For each sensitive endpoint, I've traced the flow and asked:
  • Where does the ID come from?
  • Where is data fetched?
  • What checks exist between input and data access?
• I've verified my findings by checking parent classes and middleware
• I've only reported issues I've confirmed through investigation
• All suggested fixes include actual enforcement code, not just comments