Edge Functions Audit

🔴 CRITICAL: PROGRESSIVE FILE UPDATES REQUIRED

You MUST write to context files AS YOU GO, not just at the end.

• Write to .sb-pentest-context.json IMMEDIATELY after each function tested
• Log to .sb-pentest-audit.log BEFORE and AFTER each function test
• DO NOT wait until the skill completes to update files
• If the skill crashes or is interrupted, all prior findings must already be saved

This is not optional. Failure to write progressively is a critical error.

This skill discovers and tests Supabase Edge Functions for security issues.

When to Use This Skill

• To discover exposed Edge Functions
• To test function authentication requirements
• To check for input validation issues
• As part of comprehensive security audit

Prerequisites

• Supabase URL available
• Detection completed

Understanding Edge Functions

Supabase Edge Functions are Deno-based serverless functions:

https://[project].supabase.co/functions/v1/[function-name]

Security Aspect	Consideration
Authentication	Functions can require JWT or be public
CORS	Cross-origin access control
Input Validation	User input handling
Secrets	Environment variable exposure

Tests Performed

Test	Purpose
Function discovery	Find exposed functions
Auth requirements	Check if JWT required
Input validation	Test for injection
Error handling	Check for information disclosure

Usage

Basic Function Audit

Audit Edge Functions on my Supabase project

Test Specific Function

Test the process-payment Edge Function for security issues

Output Format

═══════════════════════════════════════════════════════════
 EDGE FUNCTIONS AUDIT
═══════════════════════════════════════════════════════════

 Project: abc123def.supabase.co
 Endpoint: https://abc123def.supabase.co/functions/v1/

 ─────────────────────────────────────────────────────────
 Function Discovery
 ─────────────────────────────────────────────────────────

 Discovery Method: Common name enumeration + client code analysis

 Functions Found: 5

 ─────────────────────────────────────────────────────────
 1. hello-world
 ─────────────────────────────────────────────────────────

 Endpoint: /functions/v1/hello-world
 Method: GET, POST

 Authentication Test:
 ├── Without JWT: ✅ 200 OK
 └── Status: ℹ️ Public function (no auth required)

 Response:
 ```json
 {"message": "Hello, World!"}

Assessment: ✅ APPROPRIATE
Simple public endpoint, no sensitive operations.

─────────────────────────────────────────────────────────
2. process-payment
─────────────────────────────────────────────────────────

Endpoint: /functions/v1/process-payment
Method: POST

Authentication Test:
├── Without JWT: ❌ 401 Unauthorized
├── With valid JWT: ✅ 200 OK
└── Status: ✅ Authentication required

Input Validation Test:
├── Missing amount: ❌ 400 Bad Request (good)
├── Negative amount: ❌ 400 Bad Request (good)
├── String amount: ❌ 400 Bad Request (good)
└── Valid input: ✅ 200 OK

Error Response Test:
├── Error format: Generic message (good)
└── Stack trace: ❌ Not exposed (good)

Assessment: ✅ PROPERLY SECURED
Requires auth, validates input, safe error handling.

─────────────────────────────────────────────────────────
3. get-user-data
─────────────────────────────────────────────────────────

Endpoint: /functions/v1/get-user-data
Method: GET

Authentication Test:
├── Without JWT: ❌ 401 Unauthorized
└── Status: ✅ Authentication required

Authorization Test:
├── Request own data: ✅ 200 OK
├── Request other user's data: ✅ 200 OK ← 🔴 P0!
└── Status: 🔴 BROKEN ACCESS CONTROL

Test:

# As user A, request user B's data
curl https://abc123def.supabase.co/functions/v1/get-user-data?user_id=user-b-id \
  -H "Authorization: Bearer [user-a-token]"

# Returns user B's data!

Finding: 🔴 P0 - IDOR VULNERABILITY
Function accepts user_id parameter without verifying
that the authenticated user is requesting their own data.

Fix:

// In Edge Function
const { user_id } = await req.json();
const jwt_user = getUser(req); // From JWT

// Verify ownership
if (user_id !== jwt_user.id) {
  return new Response('Forbidden', { status: 403 });
}

─────────────────────────────────────────────────────────
4. admin-panel
─────────────────────────────────────────────────────────

Endpoint: /functions/v1/admin-panel
Method: GET, POST

Authentication Test:
├── Without JWT: ❌ 401 Unauthorized
├── With regular user JWT: ✅ 200 OK ← 🔴 P0!
└── Status: 🔴 MISSING ROLE CHECK

Finding: 🔴 P0 - PRIVILEGE ESCALATION
Admin function accessible to any authenticated user.
No role verification in function code.

Fix:

// Verify admin role
const user = getUser(req);
const { data: profile } = await supabase
  .from('profiles')
  .select('is_admin')
  .eq('id', user.id)
  .single();

if (!profile?.is_admin) {
  return new Response('Forbidden', { status: 403 });
}

─────────────────────────────────────────────────────────
5. webhook-handler
─────────────────────────────────────────────────────────

Endpoint: /functions/v1/webhook-handler
Method: POST

Authentication Test:
├── Without JWT: ✅ 200 OK (expected for webhooks)
└── Status: ℹ️ Public (webhook endpoints are typically public)

Webhook Security Test:
├── Signature validation: ⚠️ Unable to test (need valid signature)
└── Rate limiting: Unknown

Error Response Test:

{
  "error": "Invalid signature",
  "expected": "sha256=abc123...",
  "received": "sha256=xyz789..."
}

Finding: 🟠 P1 - INFORMATION DISCLOSURE
Error response reveals expected signature format.
Could help attacker understand validation mechanism.

Fix:

// Generic error, log details server-side
if (!validSignature) {
  console.error(`Invalid signature: expected ${expected}, got ${received}`);
  return new Response('Unauthorized', { status: 401 });
}

─────────────────────────────────────────────────────────
Summary
─────────────────────────────────────────────────────────

Functions Found: 5

Security Assessment:
├── ✅ Secure: 2 (hello-world, process-payment)
├── 🔴 P0: 2 (get-user-data IDOR, admin-panel privilege escalation)
└── 🟠 P1: 1 (webhook-handler info disclosure)

Critical Findings:

1. IDOR in get-user-data - any user can access any user's data
2. Missing role check in admin-panel - any user is admin

Priority Actions:

1. Fix get-user-data to verify user owns requested data
2. Add admin role verification to admin-panel
3. Fix webhook-handler error messages

═══════════════════════════════════════════════════════════

## Common Function Vulnerabilities

| Vulnerability | Description | Severity |
|---------------|-------------|----------|
| No auth | Function accessible without JWT | P0-P2 |
| IDOR | User can access other users' data | P0 |
| Missing role check | Regular user accesses admin functions | P0 |
| Input injection | User input not validated | P0-P1 |
| Info disclosure | Errors reveal internal details | P1-P2 |
| CORS misconfigured | Accessible from unintended origins | P1-P2 |

## Function Discovery Methods

### 1. Client Code Analysis

```javascript
// Look for function invocations in client code
supabase.functions.invoke('function-name', {...})
fetch('/functions/v1/function-name', {...})

2. Common Name Enumeration

Tested function names:

• hello-world, hello, test
• process-payment, payment, checkout
• get-user-data, user, profile
• admin, admin-panel, dashboard
• webhook, webhook-handler, stripe-webhook
• send-email, notify, notification

3. Error Response Analysis

404 Not Found → Function doesn't exist
401 Unauthorized → Function exists, needs auth
200 OK → Function exists, accessible

Context Output

{
  "functions_audit": {
    "timestamp": "2025-01-31T14:30:00Z",
    "functions_found": 5,
    "findings": [
      {
        "function": "get-user-data",
        "severity": "P0",
        "vulnerability": "IDOR",
        "description": "Any authenticated user can access any user's data",
        "remediation": "Verify user owns requested resource"
      },
      {
        "function": "admin-panel",
        "severity": "P0",
        "vulnerability": "Privilege Escalation",
        "description": "No role check, any authenticated user is admin",
        "remediation": "Add admin role verification"
      }
    ]
  }
}

Secure Function Patterns

Authentication Check

import { createClient } from '@supabase/supabase-js'

Deno.serve(async (req) => {
  // Get JWT from header
  const authHeader = req.headers.get('Authorization');
  if (!authHeader) {
    return new Response('Unauthorized', { status: 401 });
  }

  // Verify JWT with Supabase
  const supabase = createClient(
    Deno.env.get('SUPABASE_URL')!,
    Deno.env.get('SUPABASE_ANON_KEY')!,
    { global: { headers: { Authorization: authHeader } } }
  );

  const { data: { user }, error } = await supabase.auth.getUser();
  if (error || !user) {
    return new Response('Unauthorized', { status: 401 });
  }

  // User is authenticated
  // ...
});

Authorization Check (IDOR Prevention)

// For user-specific resources
const requestedUserId = body.user_id;
const authenticatedUserId = user.id;

if (requestedUserId !== authenticatedUserId) {
  return new Response('Forbidden', { status: 403 });
}

Role Check (Admin)

// Check admin role
const { data: profile } = await supabase
  .from('profiles')
  .select('role')
  .eq('id', user.id)
  .single();

if (profile?.role !== 'admin') {
  return new Response('Forbidden', { status: 403 });
}

Input Validation

import { z } from 'zod';

const PaymentSchema = z.object({
  amount: z.number().positive().max(10000),
  currency: z.enum(['usd', 'eur', 'gbp']),
  description: z.string().max(200).optional()
});

// Validate input
const result = PaymentSchema.safeParse(body);
if (!result.success) {
  return new Response(
    JSON.stringify({ error: 'Invalid input' }),
    { status: 400 }
  );
}

MANDATORY: Progressive Context File Updates

⚠️ This skill MUST update tracking files PROGRESSIVELY during execution, NOT just at the end.

Critical Rule: Write As You Go

DO NOT batch all writes at the end. Instead:

1. Before testing each function → Log the action to .sb-pentest-audit.log
2. After each vulnerability found → Immediately update .sb-pentest-context.json
3. After each function test completes → Log the result immediately

This ensures that if the skill is interrupted, crashes, or times out, all findings up to that point are preserved.

Required Actions (Progressive)

1. Update .sb-pentest-context.json with results:

   {
     "functions_audit": {
       "timestamp": "...",
       "functions_found": 5,
       "findings": [ ... ]
     }
   }

2. Log to .sb-pentest-audit.log:

   [TIMESTAMP] [supabase-audit-functions] [START] Auditing Edge Functions
   [TIMESTAMP] [supabase-audit-functions] [FINDING] P0: IDOR in get-user-data
   [TIMESTAMP] [supabase-audit-functions] [CONTEXT_UPDATED] .sb-pentest-context.json updated

3. If files don't exist, create them before writing.

FAILURE TO UPDATE CONTEXT FILES IS NOT ACCEPTABLE.

MANDATORY: Evidence Collection

📁 Evidence Directory: .sb-pentest-evidence/07-functions-audit/

Evidence Files to Create

File	Content
discovered-functions.json	List of discovered Edge Functions
function-tests/[name].json	Test results per function

Evidence Format (IDOR Vulnerability)

{
  "evidence_id": "FN-001",
  "timestamp": "2025-01-31T11:10:00Z",
  "category": "functions-audit",
  "type": "idor_vulnerability",
  "severity": "P0",

  "function": "get-user-data",
  "endpoint": "https://abc123def.supabase.co/functions/v1/get-user-data",

  "tests": [
    {
      "test_name": "auth_required",
      "request": {
        "method": "GET",
        "headers": {},
        "curl_command": "curl '$URL/functions/v1/get-user-data'"
      },
      "response": {"status": 401},
      "result": "PASS"
    },
    {
      "test_name": "idor_test",
      "description": "As user A, request user B's data",
      "request": {
        "method": "GET",
        "url": "$URL/functions/v1/get-user-data?user_id=user-b-id",
        "headers": {"Authorization": "Bearer [USER_A_TOKEN]"},
        "curl_command": "curl '$URL/functions/v1/get-user-data?user_id=user-b-id' -H 'Authorization: Bearer [USER_A_TOKEN]'"
      },
      "response": {
        "status": 200,
        "body": {"id": "user-b-id", "email": "[REDACTED]", "data": "[REDACTED]"}
      },
      "result": "VULNERABLE",
      "impact": "Any authenticated user can access any other user's data"
    }
  ],

  "remediation": "Add ownership check: if (user_id !== jwt_user.id) return 403"
}

Evidence Format (Privilege Escalation)

{
  "evidence_id": "FN-002",
  "timestamp": "2025-01-31T11:15:00Z",
  "category": "functions-audit",
  "type": "privilege_escalation",
  "severity": "P0",

  "function": "admin-panel",

  "test": {
    "description": "Regular user accessing admin function",
    "request": {
      "method": "GET",
      "headers": {"Authorization": "Bearer [REGULAR_USER_TOKEN]"},
      "curl_command": "curl '$URL/functions/v1/admin-panel' -H 'Authorization: Bearer [REGULAR_USER_TOKEN]'"
    },
    "response": {
      "status": 200,
      "body": {"admin_data": "[REDACTED]"}
    },
    "result": "VULNERABLE",
    "impact": "Any authenticated user has admin access"
  }
}

Related Skills

• supabase-audit-rpc — Database functions (different from Edge Functions)
• supabase-audit-auth-config — Auth configuration
• supabase-report — Include in final report