Restrict inputs for compression flag to gzip and zstd

This change will ensure that users can only specify supported compression algorithms (`zstd`, `gzip`) to the `--compression` flag.

cmd/executor/cmd/root.go

@@ -225,7 +225,7 @@ func addKanikoOptionsFlags() {
 	RootCmd.PersistentFlags().StringVarP(&opts.ImageNameDigestFile, "image-name-with-digest-file", "", "", "Specify a file to save the image name w/ digest of the built image to.")
 	RootCmd.PersistentFlags().StringVarP(&opts.ImageNameTagDigestFile, "image-name-tag-with-digest-file", "", "", "Specify a file to save the image name w/ image tag w/ digest of the built image to.")
 	RootCmd.PersistentFlags().StringVarP(&opts.OCILayoutPath, "oci-layout-path", "", "", "Path to save the OCI image layout of the built image.")
-	RootCmd.PersistentFlags().StringVarP(&opts.Compression, "compression", "", "", "Compression algorithm (gzip, zstd)")
+	RootCmd.PersistentFlags().VarP(&opts.Compression, "compression", "", "Compression algorithm (gzip, zstd)")
 	RootCmd.PersistentFlags().IntVarP(&opts.CompressionLevel, "compression-level", "", -1, "Compression level")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Cache, "cache", "", false, "Use cache when building image")
 	RootCmd.PersistentFlags().BoolVarP(&opts.CompressedCaching, "compressed-caching", "", true, "Compress the cached layers. Decreases build time, but increases memory usage.")

pkg/config/options.go

@@ -22,8 +22,6 @@ import (
 	"strconv"
 	"strings"
 	"time"
-
-	"github.com/google/go-containerregistry/pkg/compression"
 )
 
 // CacheOptions are base image cache options that are set by command line arguments
@@ -70,7 +68,7 @@ type KanikoOptions struct {
 	ImageNameDigestFile      string
 	ImageNameTagDigestFile   string
 	OCILayoutPath            string
-	Compression              compression.Compression
+	Compression              Compression
 	CompressionLevel         int
 	ImageFSExtractRetry      int
 	SingleSnapshot           bool
@@ -129,6 +127,33 @@ func (k *KanikoGitOptions) Set(s string) error {
 	return nil
 }
 
+// Compression is an enumeration of the supported compression algorithms
+type Compression string
+
+// The collection of known MediaType values.
+const (
+	GZip Compression = "gzip"
+	ZStd Compression = "zstd"
+)
+
+func (c *Compression) String() string {
+	return string(*c)
+}
+
+func (c *Compression) Set(v string) error {
+	switch v {
+	case "gzip", "zstd":
+		*c = Compression(v)
+		return nil
+	default:
+		return errors.New(`must be either "gzip" or "zstd"`)
+	}
+}
+
+func (c *Compression) Type() string {
+	return "compression"
+}
+
 // WarmerOptions are options that are set by command line arguments to the cache warmer.
 type WarmerOptions struct {
 	CacheOptions

pkg/executor/push.go

@@ -308,8 +308,6 @@ func pushLayerToCache(opts *config.KanikoOptions, cacheKey string, tarPath strin
 	switch opts.Compression {
 	case "zstd":
 		layerOpts = append(layerOpts, tarball.WithCompression("zstd"))
-	case "none":
-		layerOpts = append(layerOpts, tarball.WithCompression("none"))
 	default:
 		// layer already gzipped by default
 	}