chunked: skip validation for prefetched images

if the image is created locally there is no need to validate again the
files.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/chunked/storage_linux.go

@@ -74,6 +74,8 @@ type chunkedDiffer struct {
 
 	convertToZstdChunked bool
 
+	skipValidation bool
+
 	blobSize int64
 
 	storeOpts *types.StoreOptions
@@ -935,8 +937,10 @@ func (c *chunkedDiffer) appendCompressedStreamToFile(compression compressedFileT
 		if err := appendHole(int(destFile.file.Fd()), size); err != nil {
 			return err
 		}
-		if err := hashHole(destFile.hash, size, c.copyBuffer); err != nil {
-			return err
+		if destFile.hash != nil {
+			if err := hashHole(destFile.hash, size, c.copyBuffer); err != nil {
+				return err
+			}
 		}
 	default:
 		return fmt.Errorf("unknown file type %q", c.fileType)
@@ -945,33 +949,43 @@ func (c *chunkedDiffer) appendCompressedStreamToFile(compression compressedFileT
 }
 
 type destinationFile struct {
-	dirfd    int
-	file     *os.File
-	digester digest.Digester
-	hash     hash.Hash
-	to       io.Writer
-	metadata *internal.FileMetadata
-	options  *archive.TarOptions
+	digester       digest.Digester
+	dirfd          int
+	file           *os.File
+	hash           hash.Hash
+	metadata       *internal.FileMetadata
+	options        *archive.TarOptions
+	skipValidation bool
+	to             io.Writer
 }
 
-func openDestinationFile(dirfd int, metadata *internal.FileMetadata, options *archive.TarOptions) (*destinationFile, error) {
+func openDestinationFile(dirfd int, metadata *internal.FileMetadata, options *archive.TarOptions, skipValidation bool) (*destinationFile, error) {
 	file, err := openFileUnderRoot(metadata.Name, dirfd, newFileFlags, 0)
 	if err != nil {
 		return nil, err
 	}
 
-	digester := digest.Canonical.Digester()
-	hash := digester.Hash()
-	to := io.MultiWriter(file, hash)
+	var digester digest.Digester
+	var hash hash.Hash
+	var to io.Writer
+
+	if skipValidation {
+		to = file
+	} else {
+		digester = digest.Canonical.Digester()
+		hash = digester.Hash()
+		to = io.MultiWriter(file, hash)
+	}
 
 	return &destinationFile{
-		file:     file,
-		digester: digester,
-		hash:     hash,
-		to:       to,
-		metadata: metadata,
-		options:  options,
-		dirfd:    dirfd,
+		file:           file,
+		digester:       digester,
+		hash:           hash,
+		to:             to,
+		metadata:       metadata,
+		options:        options,
+		dirfd:          dirfd,
+		skipValidation: skipValidation,
 	}, nil
 }
 
@@ -983,12 +997,14 @@ func (d *destinationFile) Close() (Err error) {
 		}
 	}()
 
-	manifestChecksum, err := digest.Parse(d.metadata.Digest)
-	if err != nil {
-		return err
-	}
-	if d.digester.Digest() != manifestChecksum {
-		return fmt.Errorf("checksum mismatch for %q (got %q instead of %q)", d.file.Name(), d.digester.Digest(), manifestChecksum)
+	if !d.skipValidation {
+		manifestChecksum, err := digest.Parse(d.metadata.Digest)
+		if err != nil {
+			return err
+		}
+		if d.digester.Digest() != manifestChecksum {
+			return fmt.Errorf("checksum mismatch for %q (got %q instead of %q)", d.file.Name(), d.digester.Digest(), manifestChecksum)
+		}
 	}
 
 	return setFileAttrs(d.dirfd, d.file, os.FileMode(d.metadata.Mode), d.metadata, d.options, false)
@@ -1088,7 +1104,7 @@ func (c *chunkedDiffer) storeMissingFiles(streams chan io.ReadCloser, errs chan
 					}
 					filesToClose <- destFile
 				}
-				destFile, err = openDestinationFile(dirfd, mf.File, options)
+				destFile, err = openDestinationFile(dirfd, mf.File, options, c.skipValidation)
 				if err != nil {
 					Err = err
 					goto exit
@@ -1512,6 +1528,7 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 		c.fileType = fileTypeZstdChunked
 		c.manifest = manifest
 		c.convertToZstdChunked = false
+		c.skipValidation = true
 		c.tarSplit = tarSplit
 		// since we retrieved the whole file, use the diffID instead of the TOC digest.
 		c.tocDigest = diffID