copy: add support for ForceCompressionFormat

ForceCompressionFormat allows end users to force selected compression format
(set in DestinationCtx.CompressionFormat) which ensures that while copying
blobs of other compression algorithms are not reused.

Following flag is a frontend wrapper for: containers#2023
Will help in:
* containers/buildah#4613
* containers/podman#18660

Signed-off-by: Aditya R <[email protected]>

copy/copy.go

@@ -133,6 +133,10 @@ type Options struct {
 	// Invalid when copying a non-multi-architecture image. That will probably
 	// change in the future.
 	EnsureCompressionVariantsExist []OptionCompressionVariant
+	// ForceCompressionFormat ensures that the compression algorithm set in
+	// DestinationCtx.CompressionFormat is used exclusively, and blobs of other
+	// compression algorithms are not reused.
+	ForceCompressionFormat bool
 }
 
 // OptionCompressionVariant allows to supply information about
@@ -163,6 +167,14 @@ type copier struct {
 	signersToClose                []*signer.Signer    // Signers that should be closed when this copier is destroyed.
 }
 
+// Internal function to validate `requireCompressionFormatMatch` for copySingleImageOptions
+func shouldRequireCompressionFormatMatch(options *Options) (bool, error) {
+	if options.ForceCompressionFormat && (options.DestinationCtx == nil || options.DestinationCtx.CompressionFormat == nil) {
+		return false, fmt.Errorf("cannot use ForceCompressionFormat with undefined default compression format")
+	}
+	return options.ForceCompressionFormat, nil
+}
+
 // Image copies image from srcRef to destRef, using policyContext to validate
 // source image admissibility.  It returns the manifest which was written to
 // the new copy of the image.
@@ -269,8 +281,12 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		if len(options.EnsureCompressionVariantsExist) > 0 {
 			return nil, fmt.Errorf("EnsureCompressionVariantsExist is not implemented when not creating a multi-architecture image")
 		}
+		requireCompressionFormatMatch, err := shouldRequireCompressionFormatMatch(options)
+		if err != nil {
+			return nil, err
+		}
 		// The simple case: just copy a single image.
-		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
+		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, copySingleImageOptions{requireCompressionFormatMatch: requireCompressionFormatMatch})
 		if err != nil {
 			return nil, err
 		}
@@ -279,6 +295,10 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		if len(options.EnsureCompressionVariantsExist) > 0 {
 			return nil, fmt.Errorf("EnsureCompressionVariantsExist is not implemented when not creating a multi-architecture image")
 		}
+		requireCompressionFormatMatch, err := shouldRequireCompressionFormatMatch(options)
+		if err != nil {
+			return nil, err
+		}
 		// This is a manifest list, and we weren't asked to copy multiple images.  Choose a single image that
 		// matches the current system to copy, and copy it.
 		mfest, manifestType, err := c.unparsedToplevel.Manifest(ctx)
@@ -295,7 +315,7 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		}
 		logrus.Debugf("Source is a manifest list; copying (only) instance %s for current system", instanceDigest)
 		unparsedInstance := image.UnparsedInstance(rawSource, &instanceDigest)
-		single, err := c.copySingleImage(ctx, unparsedInstance, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
+		single, err := c.copySingleImage(ctx, unparsedInstance, nil, copySingleImageOptions{requireCompressionFormatMatch: requireCompressionFormatMatch})
 		if err != nil {
 			return nil, fmt.Errorf("copying system image from manifest list: %w", err)
 		}

copy/multiple.go

@@ -32,6 +32,10 @@ type instanceCopy struct {
 	op           instanceCopyKind
 	sourceDigest digest.Digest
 
+	// Fields which can be used by callers when operation
+	// is `instanceCopyCopy`
+	copyForceCompressionFormat bool
+
 	// Fields which can be used by callers when operation
 	// is `instanceCopyClone`
 	cloneCompressionVariant OptionCompressionVariant
@@ -122,9 +126,14 @@ func prepareInstanceCopies(list internalManifest.List, instanceDigests []digest.
 		if err != nil {
 			return res, fmt.Errorf("getting details for instance %s: %w", instanceDigest, err)
 		}
+		forceCompressionFormat, err := shouldRequireCompressionFormatMatch(options)
+		if err != nil {
+			return nil, err
+		}
 		res = append(res, instanceCopy{
-			op:           instanceCopyCopy,
-			sourceDigest: instanceDigest,
+			op:                         instanceCopyCopy,
+			sourceDigest:               instanceDigest,
+			copyForceCompressionFormat: forceCompressionFormat,
 		})
 		platform := platformV1ToPlatformComparable(instanceDetails.ReadOnly.Platform)
 		compressionList := compressionsByPlatform[platform]
@@ -230,7 +239,7 @@ func (c *copier) copyMultipleImages(ctx context.Context) (copiedManifest []byte,
 			logrus.Debugf("Copying instance %s (%d/%d)", instance.sourceDigest, i+1, len(instanceCopyList))
 			c.Printf("Copying image %s (%d/%d)\n", instance.sourceDigest, i+1, len(instanceCopyList))
 			unparsedInstance := image.UnparsedInstance(c.rawSource, &instanceCopyList[i].sourceDigest)
-			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, copySingleImageOptions{requireCompressionFormatMatch: false})
+			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, copySingleImageOptions{requireCompressionFormatMatch: instance.copyForceCompressionFormat})
 			if err != nil {
 				return nil, fmt.Errorf("copying image %d/%d from manifest list: %w", i+1, len(instanceCopyList), err)
 			}

copy/multiple_test.go

@@ -32,7 +32,7 @@ func TestPrepareCopyInstancesforInstanceCopyCopy(t *testing.T) {
 
 	for _, instance := range sourceInstances {
 		compare = append(compare, instanceCopy{op: instanceCopyCopy,
-			sourceDigest: instance})
+			sourceDigest: instance, copyForceCompressionFormat: false})
 	}
 	assert.Equal(t, instancesToCopy, compare)
 
@@ -42,6 +42,9 @@ func TestPrepareCopyInstancesforInstanceCopyCopy(t *testing.T) {
 	compare = []instanceCopy{{op: instanceCopyCopy,
 		sourceDigest: sourceInstances[1]}}
 	assert.Equal(t, instancesToCopy, compare)
+
+	_, err = prepareInstanceCopies(list, sourceInstances, &Options{Instances: []digest.Digest{sourceInstances[1]}, ImageListSelection: CopySpecificImages, ForceCompressionFormat: true})
+	require.EqualError(t, err, "cannot use ForceCompressionFormat with undefined default compression format")
 }
 
 // Test `instanceCopyClone` cases.