feat(security): ✨ Add two-factor authentication support

* Implement TwoFactorAuthenticator for 2FA login.
* Create DatabaseTwoFactorProvider for PostgreSQL integration.
* Add MemoryTwoFactorProvider for in-memory testing.
* Develop TOTPGenerator for generating and validating codes.
* Include tests for all new functionalities.
* Ensure backup codes are securely hashed and validated.

pkg/security/totp.go

@@ -0,0 +1,188 @@
+package security
+
+import (
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/base32"
+	"encoding/binary"
+	"fmt"
+	"hash"
+	"math"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// TwoFactorAuthProvider defines interface for 2FA operations
+type TwoFactorAuthProvider interface {
+	// Generate2FASecret creates a new secret for a user
+	Generate2FASecret(userID int, issuer, accountName string) (*TwoFactorSecret, error)
+
+	// Validate2FACode verifies a TOTP code
+	Validate2FACode(secret string, code string) (bool, error)
+
+	// Enable2FA activates 2FA for a user (store secret in your database)
+	Enable2FA(userID int, secret string, backupCodes []string) error
+
+	// Disable2FA deactivates 2FA for a user
+	Disable2FA(userID int) error
+
+	// Get2FAStatus checks if user has 2FA enabled
+	Get2FAStatus(userID int) (bool, error)
+
+	// Get2FASecret retrieves the user's 2FA secret
+	Get2FASecret(userID int) (string, error)
+
+	// GenerateBackupCodes creates backup codes for 2FA
+	GenerateBackupCodes(userID int, count int) ([]string, error)
+
+	// ValidateBackupCode checks and consumes a backup code
+	ValidateBackupCode(userID int, code string) (bool, error)
+}
+
+// TwoFactorSecret contains 2FA setup information
+type TwoFactorSecret struct {
+	Secret      string   `json:"secret"`       // Base32 encoded secret
+	QRCodeURL   string   `json:"qr_code_url"`  // URL for QR code generation
+	BackupCodes []string `json:"backup_codes"` // One-time backup codes
+	Issuer      string   `json:"issuer"`       // Application name
+	AccountName string   `json:"account_name"` // User identifier (email/username)
+}
+
+// TwoFactorConfig holds TOTP configuration
+type TwoFactorConfig struct {
+	Algorithm  string // SHA1, SHA256, SHA512
+	Digits     int    // Number of digits in code (6 or 8)
+	Period     int    // Time step in seconds (default 30)
+	SkewWindow int    // Number of time steps to check before/after (default 1)
+}
+
+// DefaultTwoFactorConfig returns standard TOTP configuration
+func DefaultTwoFactorConfig() *TwoFactorConfig {
+	return &TwoFactorConfig{
+		Algorithm:  "SHA1",
+		Digits:     6,
+		Period:     30,
+		SkewWindow: 1,
+	}
+}
+
+// TOTPGenerator handles TOTP code generation and validation
+type TOTPGenerator struct {
+	config *TwoFactorConfig
+}
+
+// NewTOTPGenerator creates a new TOTP generator with config
+func NewTOTPGenerator(config *TwoFactorConfig) *TOTPGenerator {
+	if config == nil {
+		config = DefaultTwoFactorConfig()
+	}
+	return &TOTPGenerator{
+		config: config,
+	}
+}
+
+// GenerateSecret creates a random base32-encoded secret
+func (t *TOTPGenerator) GenerateSecret() (string, error) {
+	secret := make([]byte, 20)
+	_, err := rand.Read(secret)
+	if err != nil {
+		return "", fmt.Errorf("failed to generate random secret: %w", err)
+	}
+	return base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(secret), nil
+}
+
+// GenerateQRCodeURL creates a URL for QR code generation
+func (t *TOTPGenerator) GenerateQRCodeURL(secret, issuer, accountName string) string {
+	params := url.Values{}
+	params.Set("secret", secret)
+	params.Set("issuer", issuer)
+	params.Set("algorithm", t.config.Algorithm)
+	params.Set("digits", fmt.Sprintf("%d", t.config.Digits))
+	params.Set("period", fmt.Sprintf("%d", t.config.Period))
+
+	label := url.PathEscape(fmt.Sprintf("%s:%s", issuer, accountName))
+	return fmt.Sprintf("otpauth://totp/%s?%s", label, params.Encode())
+}
+
+// GenerateCode creates a TOTP code for a given time
+func (t *TOTPGenerator) GenerateCode(secret string, timestamp time.Time) (string, error) {
+	// Decode secret
+	key, err := base32.StdEncoding.WithPadding(base32.NoPadding).DecodeString(strings.ToUpper(secret))
+	if err != nil {
+		return "", fmt.Errorf("invalid secret: %w", err)
+	}
+
+	// Calculate counter (time steps since Unix epoch)
+	counter := uint64(timestamp.Unix()) / uint64(t.config.Period)
+
+	// Generate HMAC
+	h := t.getHashFunc()
+	mac := hmac.New(h, key)
+
+	// Convert counter to 8-byte array
+	buf := make([]byte, 8)
+	binary.BigEndian.PutUint64(buf, counter)
+	mac.Write(buf)
+
+	sum := mac.Sum(nil)
+
+	// Dynamic truncation
+	offset := sum[len(sum)-1] & 0x0f
+	truncated := binary.BigEndian.Uint32(sum[offset:]) & 0x7fffffff
+
+	// Generate code with specified digits
+	code := truncated % uint32(math.Pow10(t.config.Digits))
+
+	format := fmt.Sprintf("%%0%dd", t.config.Digits)
+	return fmt.Sprintf(format, code), nil
+}
+
+// ValidateCode checks if a code is valid for the secret
+func (t *TOTPGenerator) ValidateCode(secret, code string) (bool, error) {
+	now := time.Now()
+
+	// Check current time and skew window
+	for i := -t.config.SkewWindow; i <= t.config.SkewWindow; i++ {
+		timestamp := now.Add(time.Duration(i*t.config.Period) * time.Second)
+		expected, err := t.GenerateCode(secret, timestamp)
+		if err != nil {
+			return false, err
+		}
+
+		if code == expected {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}
+
+// getHashFunc returns the hash function based on algorithm
+func (t *TOTPGenerator) getHashFunc() func() hash.Hash {
+	switch strings.ToUpper(t.config.Algorithm) {
+	case "SHA256":
+		return sha256.New
+	case "SHA512":
+		return sha512.New
+	default:
+		return sha1.New
+	}
+}
+
+// GenerateBackupCodes creates random backup codes
+func GenerateBackupCodes(count int) ([]string, error) {
+	codes := make([]string, count)
+	for i := 0; i < count; i++ {
+		code := make([]byte, 4)
+		_, err := rand.Read(code)
+		if err != nil {
+			return nil, fmt.Errorf("failed to generate backup code: %w", err)
+		}
+		codes[i] = fmt.Sprintf("%08X", binary.BigEndian.Uint32(code))
+	}
+	return codes, nil
+}