feat: add a composite service to provide fallback mechanisms

2 files changed, 90 insertions, 0 deletions

diff --git a/pkg/authz/composite_check_service.go b/pkg/authz/composite_check_service.go
new file mode 100644
index 0000000..5dfdfa8
--- /dev/null
+++ b/pkg/authz/composite_check_service.go
@@ -0,0 +1,34 @@
+package authz
+
+import (
+	"context"
+	"errors"
+
+	auth "github.com/envoyproxy/go-control-plane/envoy/service/auth/v3"
+	"gitlab.com/gitlab-org/software-supply-chain-security/authorization/sparkled/pkg/pls"
+)
+
+type CompositeCheckService struct {
+	services []auth.AuthorizationServer
+	auth.UnimplementedAuthorizationServer
+}
+
+func NewCheckService(services []auth.AuthorizationServer) auth.AuthorizationServer {
+	return &CompositeCheckService{
+		services: services,
+	}
+}
+
+func (svc *CompositeCheckService) Check(ctx context.Context, request *auth.CheckRequest) (*auth.CheckResponse, error) {
+	for _, client := range svc.services {
+		response, err := client.Check(ctx, request)
+		if err != nil {
+			pls.LogError(ctx, err)
+			continue
+		}
+
+		return response, err
+	}
+
+	return nil, errors.New("Unable to perform check")
+}
diff --git a/pkg/authz/composite_check_service_test.go b/pkg/authz/composite_check_service_test.go
new file mode 100644
index 0000000..dc0286c
--- /dev/null
+++ b/pkg/authz/composite_check_service_test.go
@@ -0,0 +1,56 @@
+package authz
+
+import (
+	"testing"
+
+	auth "github.com/envoyproxy/go-control-plane/envoy/service/auth/v3"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
+)
+
+func TestCompositeCheckService(t *testing.T) {
+	t.Run("without any services", func(t *testing.T) {
+		svc := NewCheckService([]auth.AuthorizationServer{})
+
+		response, err := svc.Check(t.Context(), &auth.CheckRequest{})
+
+		require.Error(t, err)
+		require.Nil(t, response)
+	})
+
+	t.Run("with a single service", func(t *testing.T) {
+		svc := NewCheckService([]auth.AuthorizationServer{
+			NewLocalCheckService(),
+		})
+
+		response, err := svc.Check(t.Context(), &auth.CheckRequest{})
+
+		require.NoError(t, err)
+		assert.Equal(t, int32(codes.PermissionDenied), response.Status.Code)
+	})
+
+	t.Run("with a multiple services", func(t *testing.T) {
+		svc := NewCheckService([]auth.AuthorizationServer{
+			NewRemoteCheckService(nil),
+			NewLocalCheckService(),
+		})
+
+		response, err := svc.Check(t.Context(), &auth.CheckRequest{})
+
+		require.NoError(t, err)
+		assert.Equal(t, int32(codes.PermissionDenied), response.Status.Code)
+	})
+
+	t.Run("with a multiple failing services", func(t *testing.T) {
+		svc := NewCheckService([]auth.AuthorizationServer{
+			NewRemoteCheckService(nil),
+			NewRemoteCheckService(nil),
+		})
+
+		response, err := svc.Check(t.Context(), &auth.CheckRequest{})
+
+		require.Error(t, err)
+		require.Nil(t, response)
+	})
+}