New

internal/crypto/crypto.go

@@ -0,0 +1,76 @@
+// Filename: internal/crypto/crypto.go
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"gemini-balancer/internal/config" // [NEW] Crypto service now depends on Config
+	"io"
+	"os"
+)
+
+type Service struct {
+	gcm cipher.AEAD
+}
+
+func NewService(cfg *config.Config) (*Service, error) {
+	keyHex := cfg.EncryptionKey
+	if keyHex == "" {
+		// Fallback to environment variable if not in config file
+		keyHex = os.Getenv("ENCRYPTION_KEY")
+		if keyHex == "" {
+			return nil, fmt.Errorf("encryption key is not configured: please set 'encryption_key' in config.yaml or the ENCRYPTION_KEY environment variable")
+		}
+	}
+	key, err := hex.DecodeString(keyHex)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode encryption key from hex: %w", err)
+	}
+	if len(key) != 32 {
+		return nil, fmt.Errorf("invalid encryption key length: must be 32 bytes (64 hex characters), got %d bytes", len(key))
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil { // ... (rest is the same)
+		return nil, fmt.Errorf("failed to create AES cipher block: %w", err)
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create GCM block cipher: %w", err)
+	}
+	return &Service{gcm: gcm}, nil
+}
+
+// Encrypt encrypts plaintext and returns hex-encoded ciphertext.
+func (s *Service) Encrypt(plaintext string) (string, error) {
+	nonce := make([]byte, s.gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", fmt.Errorf("failed to generate nonce: %w", err)
+	}
+
+	ciphertext := s.gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+	return hex.EncodeToString(ciphertext), nil
+}
+
+// Decrypt decrypts a hex-encoded ciphertext and returns the plaintext.
+func (s *Service) Decrypt(hexCiphertext string) (string, error) {
+	ciphertext, err := hex.DecodeString(hexCiphertext)
+	if err != nil {
+		return "", fmt.Errorf("ciphertext hex decode error: %w", err)
+	}
+
+	nonceSize := s.gcm.NonceSize()
+	if len(ciphertext) < nonceSize {
+		return "", fmt.Errorf("invalid ciphertext: too short")
+	}
+
+	nonce, encryptedMessage := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	plaintext, err := s.gcm.Open(nil, nonce, encryptedMessage, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to decrypt: %w", err)
+	}
+
+	return string(plaintext), nil
+}