fix: ensure hash function is available

internal/app/siftool/modif_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2023, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -81,6 +81,16 @@ func TestApp_Add(t *testing.T) {
 				sif.OptSBOMMetadata(sif.SBOMFormatCycloneDXJSON),
 			},
 		},
+		{
+			name:     "OCIRootIndex",
+			data:     []byte("{}"),
+			dataType: sif.DataOCIRootIndex,
+		},
+		{
+			name:     "OCIBlob",
+			data:     []byte("{}"),
+			dataType: sif.DataOCIBlob,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

pkg/sif/descriptor.go

@@ -10,6 +10,7 @@ package sif
 import (
 	"bytes"
 	"crypto"
+	"crypto/sha256"
 	"encoding"
 	"encoding/binary"
 	"encoding/hex"
@@ -82,7 +83,7 @@ type ociBlob struct {
 // written to the returned ociBlob prior to calling MarshalBinary.
 func newOCIBlobDigest() *ociBlob {
 	return &ociBlob{
-		hasher: crypto.SHA256.New(),
+		hasher: sha256.New(),
 		digest: v1.Hash{
 			Algorithm: "sha256",
 		},

pkg/siftool/add_test.go

@@ -39,6 +39,12 @@ func Test_command_getAdd(t *testing.T) {
 				"--datatype", "10",
 			},
 		},
+		{
+			name: "DataOCIBlob",
+			flags: []string{
+				"--datatype", "11",
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {