Phase 7: SEO/Security

> Search optimization and security enhancement

Purpose

Make the application discoverable through search and defend against security vulnerabilities.

What to Do in This Phase

1. SEO Optimization: Meta tags, structured data, sitemap
2. Performance Optimization: Core Web Vitals improvement
3. Security Enhancement: Authentication, authorization, vulnerability defense

Deliverables

docs/02-design/
├── seo-spec.md             # SEO specification
└── security-spec.md        # Security specification

src/
├── middleware/             # Security middleware
└── components/
    └── seo/                # SEO components

PDCA Application

• Plan: Define SEO/security requirements
• Design: Meta tags, security policy design
• Do: SEO/security implementation
• Check: Inspection and verification
• Act: Improve and proceed to Phase 8

Level-wise Application

| Level | Application Method | |-------|-------------------| | Starter | SEO only (minimal security) | | Dynamic | SEO + basic security | | Enterprise | SEO + advanced security |

SEO Checklist

Basic

• ] Per-page title, description
• ] Open Graph meta tags
• ] Canonical URL
• ] sitemap.xml
• ] robots.txt

Structured Data

• ] JSON-LD schema
• ] Breadcrumb
• ] Product/Review schema (if applicable)

Performance

• ] Image optimization (next/image)
• ] Font optimization
• ] Code splitting

Security Checklist

Authentication/Authorization

• ] Secure session management
• ] CSRF protection
• ] Proper permission checks

Data Protection

• ] Input validation
• ] SQL injection defense
• ] XSS defense

Communication Security

• ] HTTPS enforcement
• ] Security header configuration
• ] CORS policy

Security Architecture (Cross-Phase Connection)

Security Layer Structure

┌─────────────────────────────────────────────────────────────┐
│                     Client (Browser)                         │
├─────────────────────────────────────────────────────────────┤
│   Phase 6: UI Security                                       │
│   - XSS defense (input escaping)                            │
│   - CSRF token inclusion                                     │
│   - No sensitive info storage on client                      │
├─────────────────────────────────────────────────────────────┤
│   Phase 4/6: API Communication Security                      │
│   - HTTPS enforcement                                        │
│   - Authorization header (Bearer Token)                      │
│   - Content-Type validation                                  │
├─────────────────────────────────────────────────────────────┤
│   Phase 4: API Server Security                               │
│   - Input validation                                         │
│   - Rate Limiting                                            │
│   - Minimal error messages (prevent sensitive info exposure) │
├─────────────────────────────────────────────────────────────┤
│   Phase 2/9: Environment Variable Security                   │
│   - Secrets management                                       │
│   - Environment separation                                   │
│   - Client-exposed variable distinction                      │
└─────────────────────────────────────────────────────────────┘

Security Responsibilities by Phase

| Phase | Security Responsibility | Verification Items | |-------|------------------------|-------------------| | Phase 2 | Environment variable convention | NEXT_PUBLIC_ distinction, Secrets list | | Phase 4 | API security design | Auth method, error codes, input validation | | Phase 6 | Client security | XSS defense, token management, sensitive info | | Phase 7 | Security implementation/inspection | Full security checklist | | Phase 9 | Deployment security | Secrets injection, HTTPS, security headers |

Client Security (Phase 6 Connection)

XSS Defense Principles

⚠️ XSS (Cross-Site Scripting) Defense

1. Never use innerHTML directly
2. Always sanitize user input when rendering as HTML
3. Leverage React's automatic escaping
4. Use DOMPurify library when needed

No Sensitive Information Storage

typescript
// ❌ Forbidden: Sensitive info in localStorage
localStorage.setItem('password', password);
localStorage.setItem('creditCard', cardNumber);

// ✅ Allowed: Store only tokens (httpOnly cookies recommended)
localStorage.setItem('auth_token', token);

// ✅ More secure: httpOnly cookie (set by server)
// Set-Cookie: token=xxx; HttpOnly; Secure; SameSite=Strict

CSRF Defense

typescript
// Include CSRF token in API client
// lib/api/client.ts
private async request<T>(endpoint: string, config: RequestConfig = {}) {
  const headers = new Headers(config.headers);

  // Add CSRF token
  const csrfToken = this.getCsrfToken();
  if (csrfToken) {
    headers.set('X-CSRF-Token', csrfToken);
  }
  // ...
}

API Security (Phase 4 Connection)

Input Validation (Server-side)

typescript
// All input must be validated on the server
import { z } from 'zod';

const CreateUserSchema = z.object({
  email: z.string().email(),
  password: z.string().min(8).max(100),
  name: z.string().min(1).max(50),
});

// Usage in API Route
export async function POST(req: Request) {
  const body = await req.json();

  const result = CreateUserSchema.safeParse(body);
  if (!result.success) {
    return Response.json({
      error: {
        code: 'VALIDATION_ERROR',
        message: 'Input is invalid.',
        details: result.error.flatten().fieldErrors,
      }
    }, { status: 400 });
  }

  const { email, password, name } = result.data;
}

Error Message Security

typescript
// ❌ Dangerous: Detailed error info exposure
{
  message: 'User with email test@test.com not found',
  stack: error.stack,  // Stack trace exposed!
}

// ✅ Safe: Minimal information only
{
  code: 'NOT_FOUND',
  message: 'User not found.',
}

// Detailed logs only on server
console.error(`User not found: ${email}`, error);

Rate Limiting

typescript
// middleware.ts
import { Ratelimit } from '@upstash/ratelimit';

const ratelimit = new Ratelimit({
  redis: Redis.fromEnv(),
  limiter: Ratelimit.slidingWindow(10, '10 s'),
});

export async function middleware(request: NextRequest) {
  const ip = request.ip ?? '127.0.0.1';
  const { success } = await ratelimit.limit(ip);

  if (!success) {
    return new Response('Too Many Requests', { status: 429 });
  }
}

Environment Variable Security (Phase 2/9 Connection)

Client Exposure Check

typescript
// lib/env.ts
const serverEnvSchema = z.object({
  DATABASE_URL: z.string(),      // Server only
  AUTH_SECRET: z.string(),       // Server only
});

const clientEnvSchema = z.object({
  NEXT_PUBLIC_APP_URL: z.string(),   // Can be exposed to client
});

export const serverEnv = serverEnvSchema.parse(process.env);
export const clientEnv = clientEnvSchema.parse({
  NEXT_PUBLIC_APP_URL: process.env.NEXT_PUBLIC_APP_URL,
});

Security Header Configuration

javascript
// next.config.js
const securityHeaders = [
  { key: 'Strict-Transport-Security', value: 'max-age=63072000' },
  { key: 'X-Frame-Options', value: 'SAMEORIGIN' },
  { key: 'X-Content-Type-Options', value: 'nosniff' },
  { key: 'Referrer-Policy', value: 'origin-when-cross-origin' },
];

module.exports = {
  async headers() {
    return [{ source: '/:path*', headers: securityHeaders }];
  },
};

Security Verification Checklist (Phase 8 Connection)

Required (All Levels)

• ] HTTPS enforcement
• ] No sensitive info exposed to client
• ] Input validation (server-side)
• ] XSS defense
• ] No sensitive info in error messages

Recommended (Dynamic and above)

• ] CSRF token applied
• ] Rate Limiting applied
• ] Security headers configured
• ] httpOnly cookies (auth token)

Advanced (Enterprise)

• ] Content Security Policy (CSP)
• ] Security audit logs
• ] Regular security scans

Next.js SEO Example

tsx
// app/layout.tsx
export const metadata: Metadata = {
  title: {
    default: 'Site Name',
    template: '%s | Site Name',
  },
  description: 'Site description',
  openGraph: {
    type: 'website',
    locale: 'en_US',
    url: 'https://example.com',
    siteName: 'Site Name',
  },
};

Template

See templates/pipeline/phase-7-seo-security.template.md

Next Phase

Phase 8: Review → After optimization, verify overall code quality