Encrypt git token

backend/internal/crypto/crypto.go

@@ -0,0 +1,115 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+)
+
+var (
+	ErrKeyRequired    = errors.New("encryption key is required")
+	ErrInvalidKeySize = errors.New("encryption key must be 32 bytes (256 bits) when decoded")
+)
+
+type Crypto struct {
+	key []byte
+}
+
+// ValidateKey checks if the provided key is suitable for AES-256
+func ValidateKey(key string) error {
+	if key == "" {
+		return ErrKeyRequired
+	}
+
+	// Attempt to decode base64
+	keyBytes, err := base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		return fmt.Errorf("invalid base64 encoding: %w", err)
+	}
+
+	if len(keyBytes) != 32 {
+		return fmt.Errorf("%w: got %d bytes", ErrInvalidKeySize, len(keyBytes))
+	}
+
+	// Verify the key can be used for AES
+	_, err = aes.NewCipher(keyBytes)
+	if err != nil {
+		return fmt.Errorf("invalid encryption key: %w", err)
+	}
+
+	return nil
+}
+
+// New creates a new Crypto instance with the provided base64-encoded key
+func New(key string) (*Crypto, error) {
+	if err := ValidateKey(key); err != nil {
+		return nil, err
+	}
+
+	keyBytes, _ := base64.StdEncoding.DecodeString(key)
+	return &Crypto{key: keyBytes}, nil
+}
+
+// Encrypt encrypts the plaintext using AES-256-GCM
+func (c *Crypto) Encrypt(plaintext string) (string, error) {
+	if plaintext == "" {
+		return "", nil
+	}
+
+	block, err := aes.NewCipher(c.key)
+	if err != nil {
+		return "", err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", err
+	}
+
+	ciphertext := gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+	return base64.StdEncoding.EncodeToString(ciphertext), nil
+}
+
+// Decrypt decrypts the ciphertext using AES-256-GCM
+func (c *Crypto) Decrypt(ciphertext string) (string, error) {
+	if ciphertext == "" {
+		return "", nil
+	}
+
+	data, err := base64.StdEncoding.DecodeString(ciphertext)
+	if err != nil {
+		return "", err
+	}
+
+	block, err := aes.NewCipher(c.key)
+	if err != nil {
+		return "", err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(data) < nonceSize {
+		return "", errors.New("ciphertext too short")
+	}
+
+	nonce, ciphertextBytes := data[:nonceSize], data[nonceSize:]
+	plaintext, err := gcm.Open(nil, nonce, ciphertextBytes, nil)
+	if err != nil {
+		return "", err
+	}
+
+	return string(plaintext), nil
+}