Check push permissions before building images (#622)

* Check push permissions before building images

* Fix doc comment

* improve error messages

Gopkg.toml

@@ -37,7 +37,7 @@ required = [
 
 [[constraint]]
   name = "github.com/google/go-containerregistry"
-  revision = "8c1640add99804503b4126abc718931a4d93c31a"
+  revision = "8621d738a07bc74b2adeafd175a3c738423577a0"
 
 [[override]]
   name = "k8s.io/apimachinery"

cmd/executor/cmd/root.go

@@ -24,12 +24,11 @@ import (
 	"strings"
 	"time"
 
-	"github.com/GoogleContainerTools/kaniko/pkg/timing"
-
 	"github.com/GoogleContainerTools/kaniko/pkg/buildcontext"
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
 	"github.com/GoogleContainerTools/kaniko/pkg/constants"
 	"github.com/GoogleContainerTools/kaniko/pkg/executor"
+	"github.com/GoogleContainerTools/kaniko/pkg/timing"
 	"github.com/GoogleContainerTools/kaniko/pkg/util"
 	"github.com/genuinetools/amicontained/container"
 	"github.com/pkg/errors"
@@ -79,6 +78,9 @@ var RootCmd = &cobra.Command{
 			}
 			logrus.Warn("kaniko is being run outside of a container. This can have dangerous effects on your system")
 		}
+		if err := executor.CheckPushPermissions(opts); err != nil {
+			exit(errors.Wrap(err, "error checking push permissions -- make sure you entered the correct tag name, and that you are authenticated correctly, and try again"))
+		}
 		if err := os.Chdir("/"); err != nil {
 			exit(errors.Wrap(err, "error changing to root dir"))
 		}

pkg/executor/push.go

@@ -47,6 +47,30 @@ func (w *withUserAgent) RoundTrip(r *http.Request) (*http.Response, error) {
 	return w.t.RoundTrip(r)
 }
 
+// CheckPushPermissionos checks that the configured credentials can be used to
+// push to every specified destination.
+func CheckPushPermissions(opts *config.KanikoOptions) error {
+	if opts.NoPush {
+		return nil
+	}
+
+	checked := map[string]bool{}
+	for _, destination := range opts.Destinations {
+		destRef, err := name.NewTag(destination, name.WeakValidation)
+		if err != nil {
+			return errors.Wrap(err, "getting tag for destination")
+		}
+		if checked[destRef.Context().RepositoryStr()] {
+			continue
+		}
+		if err := remote.CheckPushPermission(destRef, creds.GetKeychain(), http.DefaultTransport); err != nil {
+			return errors.Wrapf(err, "checking push permission for %q", destRef)
+		}
+		checked[destRef.Context().RepositoryStr()] = true
+	}
+	return nil
+}
+
 // DoPush is responsible for pushing image to the destinations specified in opts
 func DoPush(image v1.Image, opts *config.KanikoOptions) error {
 	t := timing.Start("Total Push Time")