Fix: adds support for slightly nonstandard mediaType string in docker image layers (#487)

* fix: adds support for application/vnd.docker.image.rootfs.diff.tar.zstd layer mediaType

Signed-off-by: Zach Hill <[email protected]>

* add tests

Signed-off-by: Alex Goodman <[email protected]>

---------

Signed-off-by: Zach Hill <[email protected]>
Signed-off-by: Alex Goodman <[email protected]>
Co-authored-by: Alex Goodman <[email protected]>

Author: zhill

pkg/image/layer.go

@@ -22,7 +22,10 @@ import (
 	"github.com/anchore/stereoscope/pkg/filetree"
 )
 
-const SingularitySquashFSLayer = "application/vnd.sylabs.sif.layer.v1.squashfs"
+const (
+	SingularitySquashFSLayer    = "application/vnd.sylabs.sif.layer.v1.squashfs"
+	BuildKitZstdCompressedLayer = "application/vnd.docker.image.rootfs.diff.tar.zstd"
+)
 
 // Layer represents a single layer within a container image.
 type Layer struct {
@@ -101,7 +104,8 @@ func (l *Layer) Read(catalog *FileCatalog, idx int, uncompressedLayersCacheDir s
 		types.OCILayerZStd,
 		types.DockerLayer,
 		types.DockerForeignLayer,
-		types.DockerUncompressedLayer:
+		types.DockerUncompressedLayer,
+		BuildKitZstdCompressedLayer:
 
 		err := l.readStandardImageLayer(idx, uncompressedLayersCacheDir, tree)
 		if err != nil {

pkg/image/layer_test.go

@@ -79,9 +79,41 @@ func TestRead(t *testing.T) {
 			wantErrContents: "no media type for you",
 		},
 		{
-			name:      "no error",
+			name:      "support OCI layer",
+			mediaType: v1Types.OCILayer,
+		},
+		{
+			name:      "support OCI uncompressed layer",
+			mediaType: v1Types.OCIUncompressedLayer,
+		},
+		{
+			name:      "support OCI restricted layer",
+			mediaType: v1Types.OCIRestrictedLayer,
+		},
+		{
+			name:      "support OCI uncompressed restricted layer",
+			mediaType: v1Types.OCIUncompressedRestrictedLayer,
+		},
+		{
+			name:      "support OCI zstd layer",
+			mediaType: v1Types.OCILayerZStd,
+		},
+		{
+			name:      "support docker tar.gz layer",
 			mediaType: v1Types.DockerLayer,
 		},
+		{
+			name:      "support docker foreign layer",
+			mediaType: v1Types.DockerForeignLayer,
+		},
+		{
+			name:      "support docker uncompressed layer",
+			mediaType: v1Types.DockerUncompressedLayer,
+		},
+		{
+			name:      "support docker tar.zstd layer",
+			mediaType: BuildKitZstdCompressedLayer,
+		},
 	}
 
 	for _, tt := range tests {