Fix SIGSEGV when resolving charts dependencies

internal/helm/chart/dependency_manager.go

@@ -98,7 +98,9 @@ func NewDependencyManager(opts ...DependencyManagerOption) *DependencyManager {
 func (dm *DependencyManager) Clear() error {
 	var errs []error
 	for _, v := range dm.downloaders {
-		errs = append(errs, v.Clear())
+		if v != nil {
+			errs = append(errs, v.Clear())
+		}
 	}
 	return errors.NewAggregate(errs)
 }
@@ -257,6 +259,10 @@ func (dm *DependencyManager) resolveRepository(url string) (repo repository.Down
 	defer dm.mu.Unlock()
 
 	nUrl := repository.NormalizeURL(url)
+	err = repository.ValidateDepURL(nUrl)
+	if err != nil {
+		return
+	}
 	if _, ok := dm.downloaders[nUrl]; !ok {
 		if dm.getChartDownloaderCallback == nil {
 			err = fmt.Errorf("no chart repository for URL '%s'", nUrl)

internal/helm/chart/dependency_manager_test.go

@@ -93,6 +93,7 @@ func TestDependencyManager_Clear(t *testing.T) {
 		},
 		"with credentials":    ociRepoWithCreds,
 		"without credentials": &repository.OCIChartRepository{},
+		"nil downloader":      nil,
 	}
 
 	dm := NewDependencyManager(WithRepositories(downloaders))
@@ -428,6 +429,14 @@ func TestDependencyManager_addRemoteDependency(t *testing.T) {
 			},
 			wantErr: "no chart repository for URL",
 		},
+		{
+			name:        "resolve aliased repository error",
+			downloaders: map[string]repository.Downloader{},
+			dep: &helmchart.Dependency{
+				Repository: "@fantastic-charts",
+			},
+			wantErr: "aliased repository dependency is not supported",
+		},
 		{
 			name: "strategic load error",
 			downloaders: map[string]repository.Downloader{

internal/helm/repository/utils.go

@@ -17,11 +17,23 @@ limitations under the License.
 package repository
 
 import (
+	"fmt"
 	"strings"
 
 	helmreg "helm.sh/helm/v3/pkg/registry"
 )
 
+const (
+	alias = "@"
+)
+
+var (
+	// errInvalidDepURL is returned when the dependency URL is not supported
+	errInvalidDepURL = fmt.Errorf("invalid dependency repository URL")
+	// errInvalidAliasedDep is returned when the dependency URL is an alias
+	errInvalidAliasedDep = fmt.Errorf("aliased repository dependency is not supported")
+)
+
 // NormalizeURL normalizes a ChartRepository URL by its scheme.
 func NormalizeURL(repositoryURL string) string {
 	if repositoryURL == "" {
@@ -35,3 +47,19 @@ func NormalizeURL(repositoryURL string) string {
 	return strings.TrimRight(repositoryURL, "/") + "/"
 
 }
+
+// ValidateDepURL returns an error if the given depended repository URL declaration is not supported
+// The reason for this is that the dependency manager will not be able to resolve the alias declaration
+// e.g. repository: "@fantastic-charts"
+func ValidateDepURL(repositoryURL string) error {
+	switch {
+	case strings.HasPrefix(repositoryURL, helmreg.OCIScheme):
+		return nil
+	case strings.HasPrefix(repositoryURL, "https://") || strings.HasPrefix(repositoryURL, "http://"):
+		return nil
+	case strings.HasPrefix(repositoryURL, alias):
+		return fmt.Errorf("%w: %s", errInvalidAliasedDep, repositoryURL)
+	default:
+		return fmt.Errorf("%w: %s", errInvalidDepURL, repositoryURL)
+	}
+}