1. Secrets Management
#### β NEVER Do This
```typescript
const apiKey = "sk-proj-xxxxx" // Hardcoded secret
const dbPassword = "password123" // In source code
```
#### β
ALWAYS Do This
```typescript
const apiKey = process.env.OPENAI_API_KEY
const dbUrl = process.env.DATABASE_URL
// Verify secrets exist
if (!apiKey) {
throw new Error('OPENAI_API_KEY not configured')
}
```
#### Verification Steps
- [ ] No hardcoded API keys, tokens, or passwords
- [ ] All secrets in environment variables
- [ ]
.env.local in .gitignore - [ ] No secrets in git history
- [ ] Production secrets in hosting platform (Vercel, Railway)
2. Input Validation
#### Always Validate User Input
```typescript
import { z } from 'zod'
// Define validation schema
const CreateUserSchema = z.object({
email: z.string().email(),
name: z.string().min(1).max(100),
age: z.number().int().min(0).max(150)
})
// Validate before processing
export async function createUser(input: unknown) {
try {
const validated = CreateUserSchema.parse(input)
return await db.users.create(validated)
} catch (error) {
if (error instanceof z.ZodError) {
return { success: false, errors: error.errors }
}
throw error
}
}
```
#### File Upload Validation
```typescript
function validateFileUpload(file: File) {
// Size check (5MB max)
const maxSize = 5 1024 1024
if (file.size > maxSize) {
throw new Error('File too large (max 5MB)')
}
// Type check
const allowedTypes = ['image/jpeg', 'image/png', 'image/gif']
if (!allowedTypes.includes(file.type)) {
throw new Error('Invalid file type')
}
// Extension check
const allowedExtensions = ['.jpg', '.jpeg', '.png', '.gif']
const extension = file.name.toLowerCase().match(/\.[^.]+$/)?.[0]
if (!extension || !allowedExtensions.includes(extension)) {
throw new Error('Invalid file extension')
}
return true
}
```
#### Verification Steps
- [ ] All user inputs validated with schemas
- [ ] File uploads restricted (size, type, extension)
- [ ] No direct use of user input in queries
- [ ] Whitelist validation (not blacklist)
- [ ] Error messages don't leak sensitive info
3. SQL Injection Prevention
#### β NEVER Concatenate SQL
```typescript
// DANGEROUS - SQL Injection vulnerability
const query = SELECT * FROM users WHERE email = '${userEmail}'
await db.query(query)
```
#### β
ALWAYS Use Parameterized Queries
```typescript
// Safe - parameterized query
const { data } = await supabase
.from('users')
.select('*')
.eq('email', userEmail)
// Or with raw SQL
await db.query(
'SELECT * FROM users WHERE email = $1',
[userEmail]
)
```
#### Verification Steps
- [ ] All database queries use parameterized queries
- [ ] No string concatenation in SQL
- [ ] ORM/query builder used correctly
- [ ] Supabase queries properly sanitized
4. Authentication & Authorization
#### JWT Token Handling
```typescript
// β WRONG: localStorage (vulnerable to XSS)
localStorage.setItem('token', token)
// β
CORRECT: httpOnly cookies
res.setHeader('Set-Cookie',
token=${token}; HttpOnly; Secure; SameSite=Strict; Max-Age=3600)
```
#### Authorization Checks
```typescript
export async function deleteUser(userId: string, requesterId: string) {
// ALWAYS verify authorization first
const requester = await db.users.findUnique({
where: { id: requesterId }
})
if (requester.role !== 'admin') {
return NextResponse.json(
{ error: 'Unauthorized' },
{ status: 403 }
)
}
// Proceed with deletion
await db.users.delete({ where: { id: userId } })
}
```
#### Row Level Security (Supabase)
```sql
-- Enable RLS on all tables
ALTER TABLE users ENABLE ROW LEVEL SECURITY;
-- Users can only view their own data
CREATE POLICY "Users view own data"
ON users FOR SELECT
USING (auth.uid() = id);
-- Users can only update their own data
CREATE POLICY "Users update own data"
ON users FOR UPDATE
USING (auth.uid() = id);
```
#### Verification Steps
- [ ] Tokens stored in httpOnly cookies (not localStorage)
- [ ] Authorization checks before sensitive operations
- [ ] Row Level Security enabled in Supabase
- [ ] Role-based access control implemented
- [ ] Session management secure
5. XSS Prevention
#### Sanitize HTML
```typescript
import DOMPurify from 'isomorphic-dompurify'
// ALWAYS sanitize user-provided HTML
function renderUserContent(html: string) {
const clean = DOMPurify.sanitize(html, {
ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'p'],
ALLOWED_ATTR: []
})
return
}
```
#### Content Security Policy
```typescript
// next.config.js
const securityHeaders = [
{
key: 'Content-Security-Policy',
value: `
default-src 'self';
script-src 'self' 'unsafe-eval' 'unsafe-inline';
style-src 'self' 'unsafe-inline';
img-src 'self' data: https:;
font-src 'self';
connect-src 'self' https://api.example.com;
`.replace(/\s{2,}/g, ' ').trim()
}
]
```
#### Verification Steps
- [ ] User-provided HTML sanitized
- [ ] CSP headers configured
- [ ] No unvalidated dynamic content rendering
- [ ] React's built-in XSS protection used
6. CSRF Protection
#### CSRF Tokens
```typescript
import { csrf } from '@/lib/csrf'
export async function POST(request: Request) {
const token = request.headers.get('X-CSRF-Token')
if (!csrf.verify(token)) {
return NextResponse.json(
{ error: 'Invalid CSRF token' },
{ status: 403 }
)
}
// Process request
}
```
#### SameSite Cookies
```typescript
res.setHeader('Set-Cookie',
session=${sessionId}; HttpOnly; Secure; SameSite=Strict)
```
#### Verification Steps
- [ ] CSRF tokens on state-changing operations
- [ ] SameSite=Strict on all cookies
- [ ] Double-submit cookie pattern implemented
7. Rate Limiting
#### API Rate Limiting
```typescript
import rateLimit from 'express-rate-limit'
const limiter = rateLimit({
windowMs: 15 60 1000, // 15 minutes
max: 100, // 100 requests per window
message: 'Too many requests'
})
// Apply to routes
app.use('/api/', limiter)
```
#### Expensive Operations
```typescript
// Aggressive rate limiting for searches
const searchLimiter = rateLimit({
windowMs: 60 * 1000, // 1 minute
max: 10, // 10 requests per minute
message: 'Too many search requests'
})
app.use('/api/search', searchLimiter)
```
#### Verification Steps
- [ ] Rate limiting on all API endpoints
- [ ] Stricter limits on expensive operations
- [ ] IP-based rate limiting
- [ ] User-based rate limiting (authenticated)
8. Sensitive Data Exposure
#### Logging
```typescript
// β WRONG: Logging sensitive data
console.log('User login:', { email, password })
console.log('Payment:', { cardNumber, cvv })
// β
CORRECT: Redact sensitive data
console.log('User login:', { email, userId })
console.log('Payment:', { last4: card.last4, userId })
```
#### Error Messages
```typescript
// β WRONG: Exposing internal details
catch (error) {
return NextResponse.json(
{ error: error.message, stack: error.stack },
{ status: 500 }
)
}
// β
CORRECT: Generic error messages
catch (error) {
console.error('Internal error:', error)
return NextResponse.json(
{ error: 'An error occurred. Please try again.' },
{ status: 500 }
)
}
```
#### Verification Steps
- [ ] No passwords, tokens, or secrets in logs
- [ ] Error messages generic for users
- [ ] Detailed errors only in server logs
- [ ] No stack traces exposed to users
9. Blockchain Security (Solana)
#### Wallet Verification
```typescript
import { verify } from '@solana/web3.js'
async function verifyWalletOwnership(
publicKey: string,
signature: string,
message: string
) {
try {
const isValid = verify(
Buffer.from(message),
Buffer.from(signature, 'base64'),
Buffer.from(publicKey, 'base64')
)
return isValid
} catch (error) {
return false
}
}
```
#### Transaction Verification
```typescript
async function verifyTransaction(transaction: Transaction) {
// Verify recipient
if (transaction.to !== expectedRecipient) {
throw new Error('Invalid recipient')
}
// Verify amount
if (transaction.amount > maxAmount) {
throw new Error('Amount exceeds limit')
}
// Verify user has sufficient balance
const balance = await getBalance(transaction.from)
if (balance < transaction.amount) {
throw new Error('Insufficient balance')
}
return true
}
```
#### Verification Steps
- [ ] Wallet signatures verified
- [ ] Transaction details validated
- [ ] Balance checks before transactions
- [ ] No blind transaction signing
10. Dependency Security
#### Regular Updates
```bash
# Check for vulnerabilities
npm audit
# Fix automatically fixable issues
npm audit fix
# Update dependencies
npm update
# Check for outdated packages
npm outdated
```
#### Lock Files
```bash
# ALWAYS commit lock files
git add package-lock.json
# Use in CI/CD for reproducible builds
npm ci # Instead of npm install
```
#### Verification Steps
- [ ] Dependencies up to date
- [ ] No known vulnerabilities (npm audit clean)
- [ ] Lock files committed
- [ ] Dependabot enabled on GitHub
- [ ] Regular security updates
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