Changed the type of Layer DiffID from string to digest.Digest in …

…order to preserve the hashing algorithm used. This change also facilitates usage of `ChainID` function for base image identification.

PiperOrigin-RevId: 715787917

artifact/image/image.go

@@ -27,6 +27,7 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/osv-scalibr/artifact/image/require"
 	"github.com/google/osv-scalibr/artifact/image/unpack"
+	"github.com/opencontainers/go-digest"
 
 	scalibrfs "github.com/google/osv-scalibr/fs"
 )
@@ -43,7 +44,7 @@ type Layer interface {
 	// produced by the FS method.
 	IsEmpty() bool
 	// DiffID is the hash of the uncompressed layer. Will be an empty string if the layer is empty.
-	DiffID() string
+	DiffID() digest.Digest
 	// Command is the specific command that produced the layer.
 	Command() string
 	// Uncompressed gives the uncompressed tar as a file reader.

artifact/image/layerscanning/image/image.go

@@ -153,9 +153,16 @@ func FromV1Image(v1Image v1.Image, config *Config) (*Image, error) {
 	// Add the root directory to each chain layer. If this is not done, then the virtual paths won't
 	// be rooted, and traversal in the virtual filesystem will be broken.
 	for _, chainLayer := range chainLayers {
+		var layerDigest string
+		if chainLayer.latestLayer.IsEmpty() {
+			layerDigest = ""
+		} else {
+			layerDigest = chainLayer.latestLayer.DiffID().Encoded()
+		}
+
 		err := chainLayer.fileNodeTree.Insert("/", &fileNode{
 			extractDir:    outputImage.ExtractDir,
-			originLayerID: chainLayer.latestLayer.DiffID(),
+			originLayerID: layerDigest,
 			virtualPath:   "/",
 			isWhiteout:    false,
 			mode:          fs.ModeDir,
@@ -176,14 +183,15 @@ func FromV1Image(v1Image v1.Image, config *Config) (*Image, error) {
 			continue
 		}
 
+		originLayerID := chainLayer.latestLayer.DiffID().Encoded()
+
 		// Create the chain layer directory if it doesn't exist.
-		dirPath := path.Join(tempPath, chainLayer.latestLayer.DiffID())
+		dirPath := path.Join(tempPath, originLayerID)
 		if err := os.Mkdir(dirPath, dirPermission); err != nil && !errors.Is(err, fs.ErrExist) {
 			return &outputImage, fmt.Errorf("failed to create chain layer directory: %w", err)
 		}
 
 		chainLayersToFill := chainLayers[i:]
-		originLayerID := chainLayer.latestLayer.DiffID()
 		layerReader, err := chainLayer.latestLayer.Uncompressed()
 		if err != nil {
 			return &outputImage, err

artifact/image/layerscanning/image/layer.go

@@ -26,6 +26,7 @@ import (
 	"github.com/google/osv-scalibr/artifact/image"
 	"github.com/google/osv-scalibr/artifact/image/pathtree"
 	scalibrfs "github.com/google/osv-scalibr/fs"
+	"github.com/opencontainers/go-digest"
 )
 
 var (
@@ -48,7 +49,7 @@ var (
 
 // Layer implements the Layer interface.
 type Layer struct {
-	diffID       string
+	diffID       digest.Digest
 	buildCommand string
 	isEmpty      bool
 	uncompressed io.ReadCloser
@@ -65,7 +66,7 @@ func (layer *Layer) IsEmpty() bool {
 }
 
 // DiffID returns the diff id of the layer.
-func (layer *Layer) DiffID() string {
+func (layer *Layer) DiffID() digest.Digest {
 	return layer.diffID
 }
 
@@ -94,7 +95,7 @@ func convertV1Layer(v1Layer v1.Layer, command string, isEmpty bool) (*Layer, err
 	}
 
 	return &Layer{
-		diffID:       diffID.Hex,
+		diffID:       digest.FromString(diffID.String()),
 		buildCommand: command,
 		isEmpty:      isEmpty,
 		uncompressed: uncompressed,

artifact/image/layerscanning/image/layer_test.go

@@ -48,7 +48,8 @@ func TestConvertV1Layer(t *testing.T) {
 			command: "ADD file",
 			isEmpty: false,
 			wantLayer: &Layer{
-				diffID:       "abc123",
+				// The diffID is the encoded string: digest.FromString("abc123").
+				diffID:       "sha256:27f2fb5c8ba6b6d955cbc3cd78e89a898cac60a0442260129235683f4cc74e90",
 				buildCommand: "ADD file",
 				isEmpty:      false,
 				uncompressed: reader,

artifact/image/layerscanning/testing/fakechainlayer/fake_chain_layer.go

@@ -25,21 +25,22 @@ import (
 
 	"github.com/google/osv-scalibr/artifact/image"
 	scalibrfs "github.com/google/osv-scalibr/fs"
+	"github.com/opencontainers/go-digest"
 )
 
 // FakeChainLayer is a fake implementation of the image.ChainLayer and scalibrfs.FS interface for
 // testing purposes.
 type FakeChainLayer struct {
 	index   int
-	diffID  string
 	command string
-	layer   image.Layer
 	testDir string
+	diffID  digest.Digest
+	layer   image.Layer
 	files   map[string]string
 }
 
 // New creates a new FakeChainLayer.
-func New(testDir string, index int, diffID string, command string, layer image.Layer, files map[string]string) (*FakeChainLayer, error) {
+func New(testDir string, index int, diffID digest.Digest, command string, layer image.Layer, files map[string]string) (*FakeChainLayer, error) {
 	for name, contents := range files {
 		filename := filepath.Join(testDir, name)
 		file, err := os.Create(filename)

artifact/image/layerscanning/testing/fakelayer/fake_layer.go

@@ -21,16 +21,17 @@ import (
 	"io"
 
 	scalibrfs "github.com/google/osv-scalibr/fs"
+	"github.com/opencontainers/go-digest"
 )
 
 // FakeLayer is a fake implementation of the image.Layer interface for testing purposes.
 type FakeLayer struct {
-	diffID       string
+	diffID       digest.Digest
 	buildCommand string
 }
 
 // New creates a new FakeLayer.
-func New(diffID string, buildCommand string) *FakeLayer {
+func New(diffID digest.Digest, buildCommand string) *FakeLayer {
 	return &FakeLayer{
 		diffID:       diffID,
 		buildCommand: buildCommand,
@@ -43,7 +44,7 @@ func (fakeLayer *FakeLayer) FS() scalibrfs.FS {
 }
 
 // DiffID returns the diffID of the layer.
-func (fakeLayer *FakeLayer) DiffID() string {
+func (fakeLayer *FakeLayer) DiffID() digest.Digest {
 	return fakeLayer.diffID
 }
 

artifact/image/layerscanning/trace/trace.go

@@ -56,9 +56,16 @@ func PopulateLayerDetails(ctx context.Context, inventory []*extractor.Inventory,
 
 	// Create list of layer details struct to be referenced by inventory.
 	for i, chainLayer := range chainLayers {
+		var diffID string
+		if chainLayer.Layer().IsEmpty() {
+			diffID = ""
+		} else {
+			diffID = chainLayer.Layer().DiffID().Encoded()
+		}
+
 		chainLayerDetailsList = append(chainLayerDetailsList, &extractor.LayerDetails{
 			Index:       i,
-			DiffID:      chainLayer.Layer().DiffID(),
+			DiffID:      diffID,
 			Command:     chainLayer.Layer().Command(),
 			InBaseImage: false,
 		})

artifact/image/layerscanning/trace/trace_test.go

@@ -27,9 +27,10 @@ import (
 	"github.com/google/osv-scalibr/extractor/filesystem"
 	"github.com/google/osv-scalibr/stats"
 	"github.com/google/osv-scalibr/testing/fakeextractor"
+	"github.com/opencontainers/go-digest"
 )
 
-func setupFakeChainLayer(t *testing.T, testDir string, index int, diffID string, command string, fileContents map[string]string) *fakechainlayer.FakeChainLayer {
+func setupFakeChainLayer(t *testing.T, testDir string, index int, diffID digest.Digest, command string, fileContents map[string]string) *fakechainlayer.FakeChainLayer {
 	t.Helper()
 
 	layer := fakelayer.New(diffID, command)
@@ -56,7 +57,8 @@ func TestPopulateLayerDetails(t *testing.T) {
 	// Chain Layer 1: Start with foo and bar packages.
 	// - foo.txt
 	// - bar.txt
-	fakeChainLayer1 := setupFakeChainLayer(t, t.TempDir(), 0, "diff-id-1", "command-1", map[string]string{
+	digest1 := digest.NewDigestFromEncoded(digest.SHA256, "diff-id-1")
+	fakeChainLayer1 := setupFakeChainLayer(t, t.TempDir(), 0, digest1, "command-1", map[string]string{
 		fooFile: fooPackage,
 		barFile: barPackage,
 	})
@@ -71,7 +73,8 @@ func TestPopulateLayerDetails(t *testing.T) {
 
 	// Chain Layer 2: Deletes bar package.
 	// - foo.txt
-	fakeChainLayer2 := setupFakeChainLayer(t, t.TempDir(), 1, "diff-id-2", "command-2", map[string]string{
+	digest2 := digest.NewDigestFromEncoded(digest.SHA256, "diff-id-2")
+	fakeChainLayer2 := setupFakeChainLayer(t, t.TempDir(), 1, digest2, "command-2", map[string]string{
 		fooFile: fooPackage,
 	})
 	fakeExtractor2 := fakeextractor.New("fake-extractor-2", 1, []string{fooFile}, map[string]fakeextractor.NamesErr{
@@ -83,7 +86,8 @@ func TestPopulateLayerDetails(t *testing.T) {
 	// Chain Layer 3: Adds baz package.
 	// - foo.txt
 	// - baz.txt
-	fakeChainLayer3 := setupFakeChainLayer(t, t.TempDir(), 2, "diff-id-3", "command-3", map[string]string{
+	digest3 := digest.NewDigestFromEncoded(digest.SHA256, "diff-id-3")
+	fakeChainLayer3 := setupFakeChainLayer(t, t.TempDir(), 2, digest3, "command-3", map[string]string{
 		fooFile: fooPackage,
 		bazFile: bazPackage,
 	})
@@ -100,7 +104,8 @@ func TestPopulateLayerDetails(t *testing.T) {
 	// - foo.txt
 	// - bar.txt
 	// - baz.txt
-	fakeChainLayer4 := setupFakeChainLayer(t, t.TempDir(), 3, "diff-id-4", "command-4", map[string]string{
+	digest4 := digest.NewDigestFromEncoded(digest.SHA256, "diff-id-4")
+	fakeChainLayer4 := setupFakeChainLayer(t, t.TempDir(), 3, digest4, "command-4", map[string]string{
 		fooFile: fooPackage,
 		barFile: barPackage,
 		bazFile: bazPackage,