users_stage: Don't allow empty passwords

Make sure empty passwords are set to nil so they result in a locked
account.

Also add a test for the password hashing in NewUserStageOptions()

internal/osbuild/users_stage.go

@@ -36,6 +36,12 @@ func NewUsersStageOptions(userCustomizations []blueprint.UserCustomization, omit
 
 	users := make(map[string]UsersStageOptionsUser, len(userCustomizations))
 	for _, uc := range userCustomizations {
+		// Don't hash empty passwords, set to nil to lock account
+		if uc.Password != nil && len(*uc.Password) == 0 {
+			uc.Password = nil
+		}
+
+		// Hash non-empty un-hashed passwords
 		if uc.Password != nil && !crypt.PasswordIsCrypted(*uc.Password) {
 			cryptedPassword, err := crypt.CryptSHA512(*uc.Password)
 			if err != nil {

internal/osbuild/users_stage_test.go

@@ -1,9 +1,13 @@
 package osbuild
 
 import (
+	"strings"
 	"testing"
 
+	"github.com/osbuild/osbuild-composer/internal/blueprint"
+
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestNewUsersStage(t *testing.T) {
@@ -14,3 +18,43 @@ func TestNewUsersStage(t *testing.T) {
 	actualStage := NewUsersStage(&UsersStageOptions{})
 	assert.Equal(t, expectedStage, actualStage)
 }
+
+func TestNewUsersStageOptionsPassword(t *testing.T) {
+	Pass := "testpass"
+	EmptyPass := ""
+	CryptPass := "$6$RWdHzrPfoM6BMuIP$gKYlBXQuJgP.G2j2twbOyxYjFDPUQw8Jp.gWe1WD/obX0RMyfgw5vt.Mn/tLLX4mQjaklSiIzoAW3HrVQRg4Q." // #nosec G101
+
+	users := []blueprint.UserCustomization{
+		blueprint.UserCustomization{
+			Name:     "bart",
+			Password: &Pass,
+		},
+		blueprint.UserCustomization{
+			Name:     "lisa",
+			Password: &CryptPass,
+		},
+		blueprint.UserCustomization{
+			Name:     "maggie",
+			Password: &EmptyPass,
+		},
+		blueprint.UserCustomization{
+			Name: "homer",
+		},
+	}
+
+	options, err := NewUsersStageOptions(users, false)
+	require.Nil(t, err)
+	require.NotNil(t, options)
+
+	// bart's password should now be a hash
+	assert.True(t, strings.HasPrefix(*options.Users["bart"].Password, "$6$"))
+
+	// lisa's password should be left alone (already hashed)
+	assert.Equal(t, CryptPass, *options.Users["lisa"].Password)
+
+	// maggie's password should now be nil (locked account)
+	assert.Nil(t, options.Users["maggie"].Password)
+
+	// homer's password should still be nil (locked account)
+	assert.Nil(t, options.Users["homer"].Password)
+}