Agent Skills: Realtime Channel Audit

Realtime Channel 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 channel tested
• Log to .sb-pentest-audit.log BEFORE and AFTER each subscription 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 Supabase Realtime WebSocket channels for security issues.

When to Use This Skill

• To check if Realtime channels are properly secured
• To detect unauthorized data streaming
• When Realtime is used for sensitive data
• As part of comprehensive security audit

Prerequisites

• Supabase URL and anon key available
• Detection completed

Understanding Supabase Realtime

Supabase Realtime enables:

wss://[project].supabase.co/realtime/v1/websocket

| Feature | Description | |---------|-------------| | Postgres Changes | Stream database changes | | Broadcast | Pub/sub messaging | | Presence | User presence tracking |

Security Model

Realtime respects RLS policies:

• ✅ If RLS blocks SELECT, Realtime won't stream
• ❌ If RLS allows SELECT, Realtime streams data
• ⚠️ Broadcast channels can be subscribed without RLS

Tests Performed

| Test | Purpose | |------|---------| | Channel enumeration | Find open channels | | Postgres Changes | Test table streaming | | Broadcast | Test pub/sub access | | Presence | Test presence channel access |

Usage

Basic Realtime Audit

Audit Realtime channels on my Supabase project

Test Specific Feature

Test if Postgres Changes streams sensitive data

Output Format

═══════════════════════════════════════════════════════════
 REALTIME CHANNEL AUDIT
═══════════════════════════════════════════════════════════

 Project: abc123def.supabase.co
 Endpoint: wss://abc123def.supabase.co/realtime/v1/websocket

 ─────────────────────────────────────────────────────────
 Connection Test
 ─────────────────────────────────────────────────────────

 WebSocket Connection: ✅ Established
 Authentication: Anon key accepted
 Protocol: Phoenix channels

 ─────────────────────────────────────────────────────────
 Postgres Changes Test
 ─────────────────────────────────────────────────────────

 Subscribing to table changes with anon key...

 Table: users
 ├── Subscribe: ✅ Subscribed
 ├── INSERT events: 🔴 P0 - RECEIVING ALL NEW USERS
 ├── UPDATE events: 🔴 P0 - RECEIVING ALL UPDATES
 └── DELETE events: 🔴 P0 - RECEIVING ALL DELETES

 Sample Event Received:
 ```json
 {
   "type": "INSERT",
   "table": "users",
   "record": {
     "id": "550e8400-e29b-...",
     "email": "newuser@example.com",  ← PII STREAMING!
     "name": "New User",
     "created_at": "2025-01-31T10:00:00Z"
   }
 }

Finding: 🔴 P0 - User data streaming without authentication! RLS may not be properly configured for Realtime.

Table: orders ├── Subscribe: ✅ Subscribed ├── INSERT events: ❌ Not receiving (RLS working) ├── UPDATE events: ❌ Not receiving (RLS working) └── DELETE events: ❌ Not receiving (RLS working)

Assessment: ✅ Orders table properly protected.

Table: posts ├── Subscribe: ✅ Subscribed ├── INSERT events: ✅ Receiving published only ├── UPDATE events: ✅ Receiving published only └── DELETE events: ✅ Receiving published only

Assessment: ✅ Posts streaming respects RLS (published only).

───────────────────────────────────────────────────────── Broadcast Channel Test ─────────────────────────────────────────────────────────

Attempting to subscribe to common channel names...

Channel: room:lobby ├── Subscribe: ✅ Success ├── Messages: Receiving broadcasts └── Assessment: ℹ️ Open channel (may be intentional)

Channel: admin ├── Subscribe: ✅ Success ← Should this be public? ├── Messages: Receiving admin notifications └── Assessment: 🟠 P1 - Admin channel publicly accessible

Channel: notifications ├── Subscribe: ✅ Success ├── Messages: Receiving user notifications for ALL users! └── Assessment: 🔴 P0 - User notifications exposed

Sample Notification:

{
  "user_id": "123...",
  "type": "payment_received",
  "amount": 150.00,
  "from": "customer@example.com"
}

───────────────────────────────────────────────────────── Presence Test ─────────────────────────────────────────────────────────

Channel: online-users ├── Subscribe: ✅ Success ├── Presence List: Receiving all online users └── Users Online: 47

Sample Presence Data:

{
  "user_id": "550e8400-...",
  "email": "user@example.com",
  "status": "online",
  "last_seen": "2025-01-31T14:00:00Z"
}

Assessment: 🟠 P1 - User presence data exposed Consider if email/user_id should be visible.

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

Postgres Changes: ├── 🔴 P0: users table streaming all data ├── ✅ PASS: orders table protected by RLS └── ✅ PASS: posts table correctly filtered

Broadcast: ├── 🔴 P0: notifications channel exposing user data ├── 🟠 P1: admin channel publicly accessible └── ℹ️ INFO: lobby channel open (review if intended)

Presence: └── 🟠 P1: online-users exposing user details

Critical Findings: 2 High Findings: 2

═══════════════════════════════════════════════════════════ Recommendations ═══════════════════════════════════════════════════════════

1. FIX USERS TABLE RLS Ensure RLS applies to Realtime:

   ALTER TABLE users ENABLE ROW LEVEL SECURITY;
   
   CREATE POLICY "Users see only themselves"
     ON users FOR SELECT
     USING (auth.uid() = id);
   

2. SECURE BROADCAST CHANNELS Use Realtime Authorization:

   // Require auth for sensitive channels
   const channel = supabase.channel('admin', {
     config: {
       broadcast: { ack: true },
       presence: { key: userId }
     }
   })
   
   // Server-side: validate channel access
   // Use RLS on realtime.channels table
   

3. LIMIT PRESENCE DATA Only share necessary information:

   channel.track({
     online_at: new Date().toISOString()
     // Don't include email, user_id unless needed
   })
   

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

## Realtime Security Model

### Postgres Changes + RLS

```sql
-- This RLS policy applies to Realtime too
CREATE POLICY "Users see own data"
  ON users FOR SELECT
  USING (auth.uid() = id);

-- With this policy:
-- - API SELECT: Only own data
-- - Realtime: Only own data changes

Broadcast Security

-- Realtime authorization (Supabase extension)
-- Add policies to realtime.channels virtual table

-- Only authenticated users can join
CREATE POLICY "Authenticated users join channels"
  ON realtime.channels FOR SELECT
  USING (auth.role() = 'authenticated');

-- Or restrict specific channels
CREATE POLICY "Admin channel for admins"
  ON realtime.channels FOR SELECT
  USING (
    name != 'admin' OR
    (SELECT is_admin FROM profiles WHERE id = auth.uid())
  );

Context Output

{
  "realtime_audit": {
    "timestamp": "2025-01-31T14:00:00Z",
    "connection": "established",
    "postgres_changes": {
      "users": {
        "subscribed": true,
        "receiving_events": true,
        "severity": "P0",
        "finding": "All user data streaming without RLS"
      },
      "orders": {
        "subscribed": true,
        "receiving_events": false,
        "severity": null,
        "finding": "Properly protected by RLS"
      }
    },
    "broadcast": {
      "notifications": {
        "accessible": true,
        "severity": "P0",
        "finding": "User notifications exposed"
      },
      "admin": {
        "accessible": true,
        "severity": "P1",
        "finding": "Admin channel publicly accessible"
      }
    },
    "presence": {
      "online-users": {
        "accessible": true,
        "severity": "P1",
        "users_visible": 47,
        "finding": "User presence data exposed"
      }
    }
  }
}

Common Realtime Issues

| Issue | Cause | Fix | |-------|-------|-----| | All data streaming | RLS not enabled/configured | Enable and configure RLS | | Broadcast open | No channel authorization | Add channel policies | | Presence exposed | Too much data tracked | Minimize tracked data |

Remediation Examples

Secure Table Streaming

-- Ensure RLS is enabled
ALTER TABLE users ENABLE ROW LEVEL SECURITY;

-- Policy for authenticated users only
CREATE POLICY "Users see own profile" ON users
  FOR SELECT
  USING (auth.uid() = id);

-- Realtime will now only stream changes for the authenticated user's row

Secure Broadcast Channels

// Client: Check access before subscribing
const { data: canAccess } = await supabase
  .from('channel_access')
  .select('*')
  .eq('channel', 'admin')
  .eq('user_id', userId)
  .single();

if (canAccess) {
  const channel = supabase.channel('admin');
  channel.subscribe();
}

Minimal Presence Data

// Before (too much data)
channel.track({
  user_id: userId,
  email: email,
  name: fullName,
  avatar: avatarUrl
});

// After (minimal data)
channel.track({
  online_at: new Date().toISOString()
  // User details fetched separately if needed
});

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 channel → Log the action to .sb-pentest-audit.log
2. After each data exposure found → Immediately update .sb-pentest-context.json
3. After each subscription test → 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:

   {
     "realtime_audit": {
       "timestamp": "...",
       "connection": "established",
       "postgres_changes": { ... },
       "broadcast": { ... },
       "presence": { ... }
     }
   }
   

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

   [TIMESTAMP] [supabase-audit-realtime] [START] Auditing Realtime channels
   [TIMESTAMP] [supabase-audit-realtime] [FINDING] P0: users table streaming all data
   [TIMESTAMP] [supabase-audit-realtime] [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/06-realtime-audit/

Evidence Files to Create

| File | Content | |------|---------| | websocket-connection.json | WebSocket connection test | | postgres-changes/[table].json | Table subscription results | | broadcast-channels/[channel].json | Broadcast channel access | | presence-data/[channel].json | Presence data exposure |

Evidence Format

{
  "evidence_id": "RT-001",
  "timestamp": "2025-01-31T11:05:00Z",
  "category": "realtime-audit",
  "type": "postgres_changes",
  "severity": "P0",

  "table": "users",

  "subscription_test": {
    "channel": "realtime:public:users",
    "subscribed": true,
    "events_received": true
  },

  "sample_event": {
    "type": "INSERT",
    "table": "users",
    "record": {
      "id": "[REDACTED]",
      "email": "[REDACTED]@example.com",
      "name": "[REDACTED]"
    },
    "redacted": true
  },

  "impact": {
    "pii_streaming": true,
    "affected_columns": ["email", "name"],
    "rls_bypass": true
  },

  "websocket_url": "wss://abc123def.supabase.co/realtime/v1/websocket",

  "reproduction_code": "const channel = supabase.channel('realtime:public:users').on('postgres_changes', { event: '*', schema: 'public', table: 'users' }, (payload) => console.log(payload)).subscribe()"
}

Related Skills

• supabase-audit-rls — RLS affects Realtime
• supabase-audit-tables-read — API access is related
• supabase-report — Include in final report