Fix storeInKeychain to accept LockedBuffer for data parameter

- Changed storeInKeychain to accept *memguard.LockedBuffer instead of []byte
- Updated caller in CreateKeychainUnlocker to create LockedBuffer before storing
- This ensures keychain data is protected in memory before being stored
- Added proper buffer cleanup with defer Destroy()

TODO.md

@@ -8,7 +8,7 @@ prioritized from most critical (top) to least critical (bottom).
 
 ### Functions accepting bare []byte for sensitive data
 - [x] **1. Secret.Save accepts unprotected data**: `internal/secret/secret.go:67` - `Save(value []byte, force bool)` - ✓ REMOVED - deprecated function deleted
-- [ ] **2. EncryptWithPassphrase accepts unprotected data**: `internal/secret/crypto.go:73` - `EncryptWithPassphrase(data []byte, passphrase *memguard.LockedBuffer)` - the data parameter should be LockedBuffer
+- [x] **2. EncryptWithPassphrase accepts unprotected data**: `internal/secret/crypto.go:73` - `EncryptWithPassphrase(data []byte, passphrase *memguard.LockedBuffer)` - ✓ FIXED - now accepts LockedBuffer for data
 - [ ] **3. storeInKeychain accepts unprotected data**: `internal/secret/keychainunlocker.go:469` - `storeInKeychain(itemName string, data []byte)` - stores secrets in keychain with unprotected data
 - [ ] **4. gpgEncryptDefault accepts unprotected data**: `internal/secret/pgpunlocker.go:351` - `gpgEncryptDefault(data []byte, keyID string)` - encrypts unprotected data
 

internal/secret/keychainunlocker.go

@@ -409,8 +409,12 @@ func CreateKeychainUnlocker(fs afero.Fs, stateDir string) (*KeychainUnlocker, er
 		return nil, fmt.Errorf("failed to marshal keychain data: %w", err)
 	}
 
+	// Create a secure buffer for keychain data
+	keychainDataBuffer := memguard.NewBufferFromBytes(keychainDataBytes)
+	defer keychainDataBuffer.Destroy()
+
 	// Step 8: Store data in keychain
-	if err := storeInKeychain(keychainItemName, keychainDataBytes); err != nil {
+	if err := storeInKeychain(keychainItemName, keychainDataBuffer); err != nil {
 		return nil, fmt.Errorf("failed to store data in keychain: %w", err)
 	}
 
@@ -466,14 +470,17 @@ func validateKeychainItemName(itemName string) error {
 }
 
 // storeInKeychain stores data in the macOS keychain using the security command
-func storeInKeychain(itemName string, data []byte) error {
+func storeInKeychain(itemName string, data *memguard.LockedBuffer) error {
+	if data == nil {
+		return fmt.Errorf("data buffer is nil")
+	}
 	if err := validateKeychainItemName(itemName); err != nil {
 		return fmt.Errorf("invalid keychain item name: %w", err)
 	}
 	cmd := exec.Command("/usr/bin/security", "add-generic-password", //nolint:gosec
 		"-a", itemName,
 		"-s", itemName,
-		"-w", string(data),
+		"-w", data.String(),
 		"-U") // Update if exists
 
 	if err := cmd.Run(); err != nil {