feat(secrets): implement SecretStore interface and StaticStore/LocalStore for credential management

pkg/secrets/encryption.go

@@ -0,0 +1,75 @@
+package secrets
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+// Derive a unique AES key per SecretID using HKDF
+func deriveAESKey(masterKey []byte, secretID string) []byte {
+	salt := []byte(secretID)
+	hkdf := hkdf.New(sha256.New, masterKey, salt, nil)
+	derivedKey := make([]byte, 32) // AES-256 key
+	io.ReadFull(hkdf, derivedKey)
+	return derivedKey
+}
+
+// Encrypt data using AES-GCM
+func encryptAESGCM(key, plaintext []byte) (string, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", err
+	}
+
+	aesGCM, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+
+	nonce := make([]byte, aesGCM.NonceSize())
+	_, err = io.ReadFull(rand.Reader, nonce)
+	if err != nil {
+		return "", err
+	}
+
+	ciphertext := aesGCM.Seal(nonce, nonce, plaintext, nil)
+	return hex.EncodeToString(ciphertext), nil
+}
+
+// Decrypt data using AES-GCM
+func decryptAESGCM(key []byte, encryptedData string) (string, error) {
+	data, err := hex.DecodeString(encryptedData)
+	if err != nil {
+		return "", err
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", err
+	}
+
+	aesGCM, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+
+	nonceSize := aesGCM.NonceSize()
+	if len(data) < nonceSize {
+		return "", fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
+	plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return "", err
+	}
+
+	return string(plaintext), nil
+}