# txt-domain-verification

A production-ready Node.js package for verifying domain ownership through DNS TXT records with authoritative nameserver queries, security features, and comprehensive error handling.

## 🚀 New in v2.0.0

- **Authoritative Nameserver Queries**: Queries domain nameservers directly instead of relying on OS/ISP resolvers
- **Secure Token Generation**: HMAC-based tokens with user binding and expiration
- **Domain Normalization**: Handles punycode, casing, and trailing dots consistently
- **Retry Logic**: Exponential backoff with configurable retry attempts
- **Partial Propagation Detection**: Reports when verification records are still propagating
- **TypeScript Support**: Full type definitions included
- **Dual Build**: Both CommonJS and ESM modules supported

## 🔒 Security Features

- **Fixed TXT Record Name**: Uses `_verify.example.com` for actual verification
- **HMAC Tokens**: Cryptographically secure tokens bound to user, domain, and timestamp
- **Token Expiration**: Configurable expiry (default: 72 hours)
- **Single-Use Tokens**: Designed for one-time verification
- **DNS-Only Verification**: No HTTP/HTTPS requests to prevent SSRF attacks

## 📦 Installation

```bash
npm install txt-domain-verification
```

```bash
yarn add txt-domain-verification
```

```bash
pnpm add txt-domain-verification
```

```bash
bun add txt-domain-verification
```

## 🛠️ Usage

### Basic Verification Flow

```javascript
const {
  generateVerificationCode,
  verifyDomain,
  CONFIG,
} = require('txt-domain-verification');

// 1. Generate verification code
const verificationCode = generateVerificationCode(
  'example.com', // Domain to verify
  'your-secret-key', // Secret for HMAC
  'user123', // User identifier
  'AcmeCorp', // Business name (optional)
  '{{businessName}} Verification: {{token}}' // Custom format
);

console.log(verificationCode.instructions);
// Output: Please add the following TXT record to your DNS settings for example.com:
// Name: _verify
// Value: AcmeCorp Verification: eyJ0b2tlbiI6ImFiY2RlZiJ9...

// 2. User adds TXT record to DNS
// 3. Verify domain ownership
const result = await verifyDomain('example.com', verificationCode.token);

if (result.verified) {
  console.log('Domain verified successfully!');
} else if (result.partialPropagation) {
  console.log(
    `Partial propagation: ${result.successfulQueries}/${result.totalNameservers} nameservers responding`
  );
}
```

### Advanced Verification with Options

```javascript
const result = await verifyDomain(
  'example.com',
  verificationCode.token,
  '_verify', // Custom verification prefix
  {
    maxRetries: 5, // Maximum retry attempts
    retryDelay: 2000, // Base delay between retries (ms)
  }
);

console.log('Verification result:', {
  verified: result.verified,
  domain: result.domain,
  totalNameservers: result.totalNameservers,
  successfulQueries: result.successfulQueries,
  partialPropagation: result.partialPropagation,
  timestamp: result.timestamp,
});
```

### Domain Normalization

```javascript
const { normalizeDomain } = require('txt-domain-verification');

const normalized = normalizeDomain('  EXAMPLE.COM.  ');
console.log(normalized); // 'example.com'
```

### Secure Token Generation

```javascript
const { generateSecureToken } = require('txt-domain-verification');

const token = generateSecureToken(
  'secret-key',
  'user123',
  'example.com',
  new Date()
);
```

## 🔧 Configuration

```javascript
const { CONFIG } = require('txt-domain-verification');

console.log(CONFIG);
// {
//   VERIFICATION_PREFIX: '_verify',
//   TOKEN_EXPIRY_HOURS: 72,
//   MAX_RETRIES: 3,
//   RETRY_DELAY_MS: 1000,
//   DNS_TIMEOUT_MS: 10000,
//   MIN_NAMESERVERS_VERIFIED: 1
// }
```

## 📊 Verification Results

The `verifyDomain` function returns detailed information about the verification process:

```javascript
{
  verified: boolean,           // Whether verification succeeded
  domain: string,              // Normalized domain name
  attempt: number,             // Current attempt number
  totalNameservers: number,    // Total nameservers found
  successfulQueries: number,   // Successfully queried nameservers
  failedQueries: number,       // Failed nameserver queries
  matchingRecords: Array,      // Records containing the token
  partialPropagation: boolean, // Whether some nameservers are still propagating
  nameserverResults: Array,    // Detailed results from each nameserver
  timestamp: Date              // When verification was performed
}
```

## 🌐 How It Works

1. **Nameserver Resolution**: Queries the domain's authoritative nameservers
2. **Direct DNS Queries**: Sends DNS queries directly to each nameserver
3. **Token Verification**: Checks TXT records for the secure verification token
4. **Propagation Detection**: Reports partial propagation status
5. **Retry Logic**: Implements exponential backoff for failed queries

## 🧪 Testing

```bash
npm test
npm run test:coverage
```

## 📦 Building

```bash
npm run build
```

This creates both CommonJS (`dist/index.js`) and ESM (`dist/index.mjs`) builds.

## 🔄 Migration from v1.x

### Old API (Deprecated)

```javascript
const {
  generateVerificationCode,
  verifyDomain,
} = require('txt-domain-verification');

// Old: Random hex codes
const result = generateVerificationCode('example.com', 'business');
const isVerified = await verifyDomain('example.com', result.formattedString);
```

### New API (Recommended)

```javascript
const {
  generateVerificationCode,
  verifyDomain,
} = require('txt-domain-verification');

// New: Secure HMAC tokens
const verificationCode = generateVerificationCode(
  'example.com',
  'your-secret-key',
  'user123',
  'business'
);

const result = await verifyDomain('example.com', verificationCode.token);
```

## 🚨 Important Notes

- **Secret Management**: Store your secret key securely (environment variables, secret management service)
- **Token Expiry**: Tokens expire after 72 hours by default
- **DNS Propagation**: Allow 5-60 minutes for DNS changes to propagate
- **Nameserver Queries**: The library queries authoritative nameservers directly for accuracy
- **Rate Limiting**: Implement rate limiting in your application for production use

## 📄 License

CC BY-SA

## 🤝 Contributing

Contributions are welcome! Please ensure all tests pass and add tests for new features.

## 📚 Examples

See `example-new.js` for comprehensive usage examples.