supabase-audit-auth-signup

Imported from yoanbernabeu/supabase-pentest-skills (skills/audit-auth/supabase-audit-auth-signup/SKILL.md) via skills.sh. Install upstream with npx skills add yoanbernabeu/supabase-pentest-skills --skill supabase-audit-auth-signup. Copyright stays with the author.

Signup Flow 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 test completed
• Log to .sb-pentest-audit.log BEFORE and AFTER each 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 tests the user registration flow for security issues and misconfigurations.

When to Use This Skill

• To verify if signup is appropriately restricted
• To test for signup abuse vectors
• To check rate limiting on registration
• As part of authentication security audit

Prerequisites

• Supabase URL and anon key available
• Auth config audit completed (recommended)

Why Signup Security Matters

Open signup can lead to:

Tests Performed

Usage

Basic Signup Test

Test signup security on my Supabase project

Check Specific Aspects

Test if disposable emails are blocked for signup

Output Format

═══════════════════════════════════════════════════════════
 SIGNUP FLOW AUDIT
═══════════════════════════════════════════════════════════

 Project: abc123def.supabase.co
 Endpoint: /auth/v1/signup

 ─────────────────────────────────────────────────────────
 Signup Availability
 ─────────────────────────────────────────────────────────

 Status: ✅ OPEN (Anyone can register)

 Test Result:
 POST /auth/v1/signup
 Body: {"email": "test-xxxxx@example.com", "password": "TestPass123!"}
 Response: 200 OK - Account created

 Assessment: Signup is publicly available.
             Review if this is intended.

 ─────────────────────────────────────────────────────────
 Email Validation
 ─────────────────────────────────────────────────────────

 Valid email formats:
 ├── user@domain.com: ✅ Accepted (expected)
 ├── user+tag@domain.com: ✅ Accepted (expected)
 └── user@subdomain.domain.com: ✅ Accepted (expected)

 Invalid email formats:
 ├── user@: ❌ Rejected (good)
 ├── @domain.com: ❌ Rejected (good)
 ├── user@.com: ❌ Rejected (good)
 └── not-an-email: ❌ Rejected (good)

 Disposable Email Test:
 ├── user@mailinator.com: ✅ Accepted ← 🟠 P2
 ├── user@tempmail.com: ✅ Accepted ← 🟠 P2
 └── user@guerrillamail.com: ✅ Accepted ← 🟠 P2

 Finding: Disposable emails are not blocked.
 Risk: Users can create throwaway accounts.

 Recommendation: Consider using an email validation
 service or blocklist in your application logic.

 ─────────────────────────────────────────────────────────
 Password Policy
 ─────────────────────────────────────────────────────────

 Minimum Length Test:
 ├── "12345" (5 chars): ❌ Rejected
 ├── "123456" (6 chars): ✅ Accepted ← P2 Short
 └── "1234567890" (10 chars): ✅ Accepted

 Current Policy: Minimum 6 characters

 Weak Password Test:
 ├── "password": ✅ Accepted ← 🟠 P2
 ├── "123456": ✅ Accepted ← 🟠 P2
 ├── "qwerty123": ✅ Accepted ← 🟠 P2
 └── "letmein": ✅ Accepted ← 🟠 P2

 Finding: Common weak passwords are accepted.

 Recommendation:
 1. Increase minimum length to 8+ characters
 2. Consider password strength requirements
 3. Check against common password lists

 ─────────────────────────────────────────────────────────
 Rate Limiting
 ─────────────────────────────────────────────────────────

 Signup Rate Test (same IP):
 ├── Request 1: ✅ 200 OK
 ├── Request 2: ✅ 200 OK
 ├── Request 3: ✅ 200 OK
 ├── Request 4: ❌ 429 Too Many Requests
 └── Retry-After: 3600 seconds

 Rate Limit: 3 signups/hour per IP
 Assessment: ✅ Rate limiting is active (good)

 ─────────────────────────────────────────────────────────
 Information Disclosure
 ─────────────────────────────────────────────────────────

 Existing Email Test:
 POST /auth/v1/signup (with existing email)
 Response: "User already registered"

 Finding: 🟠 P2 - Response reveals email existence

 This allows:
 ├── Email enumeration attacks
 ├── Knowing if someone has an account
 └── Targeted phishing attempts

 Recommendation: Use generic message like
 "Check your email to continue" for both new
 and existing accounts.

 ─────────────────────────────────────────────────────────
 Email Confirmation
 ─────────────────────────────────────────────────────────

 Status: ❌ NOT REQUIRED (confirmed in auth-config)

 Test: Created account and checked session
 Result: User immediately authenticated without
         email confirmation.

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

 Signup: Open to public
 Rate Limiting: ✅ Active (3/hour)
 Email Confirmation: ❌ Not required

 Findings:
 ├── P1: Email confirmation disabled
 ├── P2: Disposable emails accepted
 ├── P2: Weak passwords accepted
 └── P2: Email enumeration possible

 Security Score: 5/10

 Priority Actions:
 1. Enable email confirmation
 2. Strengthen password policy
 3. Consider disposable email blocking
 4. Use generic error messages

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

Test Details

Disposable Email Detection

Common disposable email domains tested:

• mailinator.com
• tempmail.com
• guerrillamail.com
• 10minutemail.com
• throwaway.email

Weak Password List

Common passwords tested:

• password, password123
• 123456, 12345678
• qwerty, qwerty123
• letmein, welcome
• admin, administrator

Rate Limit Testing

Attempt 1: 200 OK
Attempt 2: 200 OK
Attempt 3: 200 OK
Attempt 4: 429 Too Many Requests

Context Output

{
  "signup_audit": {
    "timestamp": "2025-01-31T13:00:00Z",
    "signup_open": true,
    "rate_limit": {
      "enabled": true,
      "limit": 3,
      "period": "hour"
    },
    "email_validation": {
      "basic_validation": true,
      "disposable_blocked": false
    },
    "password_policy": {
      "min_length": 6,
      "weak_passwords_blocked": false
    },
    "information_disclosure": {
      "email_enumeration": true
    },
    "findings": [
      {
        "severity": "P1",
        "issue": "Email confirmation disabled"
      },
      {
        "severity": "P2",
        "issue": "Disposable emails accepted"
      },
      {
        "severity": "P2",
        "issue": "Weak passwords accepted"
      },
      {
        "severity": "P2",
        "issue": "Email enumeration possible"
      }
    ]
  }
}

Remediation Examples

Block Disposable Emails

// In your signup handler or Edge Function
import { isDisposable } from 'email-validator-package';

if (isDisposable(email)) {
  throw new Error('Please use a permanent email address');
}

Strengthen Password Requirements

// Custom password validation
function validatePassword(password: string): boolean {
  if (password.length < 8) return false;
  if (!/[A-Z]/.test(password)) return false;
  if (!/[a-z]/.test(password)) return false;
  if (!/[0-9]/.test(password)) return false;
  return true;
}

Prevent Email Enumeration

// Always return same message
async function signup(email, password) {
  try {
    await supabase.auth.signUp({ email, password });
  } catch (error) {
    // Don't reveal if email exists
  }
  return { message: 'Check your email to continue' };
}

Restrict Signup

If signup should be invite-only:

// Use admin API to invite users
const { data, error } = await supabaseAdmin.auth.admin.inviteUserByEmail(
  'user@example.com'
);

// Or disable signup in dashboard and use:
const { data, error } = await supabaseAdmin.auth.admin.createUser({
  email: 'user@example.com',
  email_confirm: true
});

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 each signup test → Log the action to .sb-pentest-audit.log
2. After each vulnerability found → Immediately update .sb-pentest-context.json
3. After rate limit tests → Log the results 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:

   {
     "signup_audit": {
       "timestamp": "...",
       "signup_open": true,
       "rate_limit": { ... },
       "findings": [ ... ]
     }
   }

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

   [TIMESTAMP] [supabase-audit-auth-signup] [START] Testing signup security
   [TIMESTAMP] [supabase-audit-auth-signup] [FINDING] P2: Weak passwords accepted
   [TIMESTAMP] [supabase-audit-auth-signup] [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/05-auth-audit/signup-tests/

Evidence Files to Create

Evidence Format

{
  "evidence_id": "AUTH-SIGNUP-001",
  "timestamp": "2025-01-31T10:55:00Z",
  "category": "auth-audit",
  "type": "signup_test",

  "tests": [
    {
      "test_name": "weak_password_acceptance",
      "severity": "P2",
      "request": {
        "method": "POST",
        "url": "https://abc123def.supabase.co/auth/v1/signup",
        "body": {"email": "test@example.com", "password": "123456"},
        "curl_command": "curl -X POST '$URL/auth/v1/signup' -H 'apikey: $ANON_KEY' -H 'Content-Type: application/json' -d '{\"email\": \"test@example.com\", \"password\": \"123456\"}'"
      },
      "response": {
        "status": 200,
        "message": "User created"
      },
      "result": "VULNERABLE",
      "impact": "Weak passwords (6 chars) accepted"
    },
    {
      "test_name": "disposable_email",
      "severity": "P2",
      "request": {
        "body": {"email": "test@mailinator.com", "password": "Test123456!"}
      },
      "response": {
        "status": 200,
        "message": "User created"
      },
      "result": "VULNERABLE",
      "impact": "Disposable emails not blocked"
    }
  ]
}

Related Skills

• supabase-audit-auth-config — Full auth configuration
• supabase-audit-auth-users — User enumeration testing
• supabase-audit-rls — Protect user data with RLS