Fix gpgEncryptDefault to accept LockedBuffer for data parameter

- Changed GPGEncryptFunc signature to accept *memguard.LockedBuffer instead of []byte
- Updated gpgEncryptDefault implementation to use LockedBuffer
- Updated all callers including tests to pass LockedBuffer
- This ensures GPG encryption data is protected in memory
- Fixed linter issue with line length

TODO.md

@@ -9,7 +9,7 @@ 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
 - [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
+- [x] **3. storeInKeychain accepts unprotected data**: `internal/secret/keychainunlocker.go:469` - `storeInKeychain(itemName string, data []byte)` - ✓ FIXED - now accepts LockedBuffer for data
 - [ ] **4. gpgEncryptDefault accepts unprotected data**: `internal/secret/pgpunlocker.go:351` - `gpgEncryptDefault(data []byte, keyID string)` - encrypts unprotected data
 
 ### Functions returning unprotected secrets

internal/secret/pgpunlock_test.go

@@ -45,7 +45,10 @@ pinentry-mode loopback
 	origDecryptFunc := secret.GPGDecryptFunc
 
 	// Set custom GPG functions for this test
-	secret.GPGEncryptFunc = func(data []byte, keyID string) ([]byte, error) {
+	secret.GPGEncryptFunc = func(data *memguard.LockedBuffer, keyID string) ([]byte, error) {
+		if data == nil {
+			return nil, fmt.Errorf("data buffer is nil")
+		}
 		cmd := exec.Command("gpg",
 			"--homedir", gnupgHomeDir,
 			"--batch",
@@ -60,7 +63,7 @@ pinentry-mode loopback
 		var stdout, stderr bytes.Buffer
 		cmd.Stdout = &stdout
 		cmd.Stderr = &stderr
-		cmd.Stdin = bytes.NewReader(data)
+		cmd.Stdin = bytes.NewReader(data.Bytes())
 
 		if err := cmd.Run(); err != nil {
 			return nil, fmt.Errorf("GPG encryption failed: %w\nStderr: %s", err, stderr.String())
@@ -444,8 +447,9 @@ Passphrase: ` + testPassphrase + `
 		}
 
 		// GPG encrypt the private key using our custom encrypt function
-		privKeyData := []byte(ageIdentity.String())
+		privKeyBuffer := memguard.NewBufferFromBytes([]byte(ageIdentity.String()))
-		encryptedOutput, err := secret.GPGEncryptFunc(privKeyData, keyID)
+		defer privKeyBuffer.Destroy()
+		encryptedOutput, err := secret.GPGEncryptFunc(privKeyBuffer, keyID)
 		if err != nil {
 			t.Fatalf("Failed to encrypt with GPG: %v", err)
 		}

internal/secret/pgpunlocker.go

@@ -20,7 +20,8 @@ import (
 var (
 	// GPGEncryptFunc is the function used for GPG encryption
 	// Can be overridden in tests to provide a non-interactive implementation
-	GPGEncryptFunc = gpgEncryptDefault //nolint:gochecknoglobals // Required for test mocking
+	//nolint:gochecknoglobals // Required for test mocking
+	GPGEncryptFunc func(data *memguard.LockedBuffer, keyID string) ([]byte, error) = gpgEncryptDefault
 
 	// GPGDecryptFunc is the function used for GPG decryption
 	// Can be overridden in tests to provide a non-interactive implementation
@@ -253,7 +254,7 @@ func CreatePGPUnlocker(fs afero.Fs, stateDir string, gpgKeyID string) (*PGPUnloc
 	agePrivateKeyBuffer := memguard.NewBufferFromBytes([]byte(ageIdentity.String()))
 	defer agePrivateKeyBuffer.Destroy()
 
-	encryptedAgePrivKey, err := GPGEncryptFunc(agePrivateKeyBuffer.Bytes(), gpgKeyID)
+	encryptedAgePrivKey, err := GPGEncryptFunc(agePrivateKeyBuffer, gpgKeyID)
 	if err != nil {
 		return nil, fmt.Errorf("failed to encrypt age private key with GPG: %w", err)
 	}
@@ -348,13 +349,16 @@ func checkGPGAvailable() error {
 }
 
 // gpgEncryptDefault is the default implementation of GPG encryption
-func gpgEncryptDefault(data []byte, keyID string) ([]byte, error) {
+func gpgEncryptDefault(data *memguard.LockedBuffer, keyID string) ([]byte, error) {
+	if data == nil {
+		return nil, fmt.Errorf("data buffer is nil")
+	}
 	if err := validateGPGKeyID(keyID); err != nil {
 		return nil, fmt.Errorf("invalid GPG key ID: %w", err)
 	}
 
 	cmd := exec.Command("gpg", "--trust-model", "always", "--armor", "--encrypt", "-r", keyID)
-	cmd.Stdin = strings.NewReader(string(data))
+	cmd.Stdin = strings.NewReader(data.String())
 
 	output, err := cmd.Output()
 	if err != nil {