1 files changed, 429 insertions, 0 deletions
diff --git a/pkg/v1/tarball/image.go b/pkg/v1/tarball/image.go
new file mode 100644
index 0000000..1f977e1
--- /dev/null
+++ b/pkg/v1/tarball/image.go
@@ -0,0 +1,429 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tarball
+
+import (
+	"archive/tar"
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"sync"
+
+	comp "github.com/google/go-containerregistry/internal/compression"
+	"github.com/google/go-containerregistry/pkg/compression"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/partial"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+type image struct {
+	opener        Opener
+	manifest      *Manifest
+	config        []byte
+	imgDescriptor *Descriptor
+
+	tag *name.Tag
+}
+
+type uncompressedImage struct {
+	*image
+}
+
+type compressedImage struct {
+	*image
+	manifestLock sync.Mutex // Protects manifest
+	manifest     *v1.Manifest
+}
+
+var _ partial.UncompressedImageCore = (*uncompressedImage)(nil)
+var _ partial.CompressedImageCore = (*compressedImage)(nil)
+
+// Opener is a thunk for opening a tar file.
+type Opener func() (io.ReadCloser, error)
+
+func pathOpener(path string) Opener {
+	return func() (io.ReadCloser, error) {
+		return os.Open(path)
+	}
+}
+
+// ImageFromPath returns a v1.Image from a tarball located on path.
+func ImageFromPath(path string, tag *name.Tag) (v1.Image, error) {
+	return Image(pathOpener(path), tag)
+}
+
+// LoadManifest load manifest
+func LoadManifest(opener Opener) (Manifest, error) {
+	m, err := extractFileFromTar(opener, "manifest.json")
+	if err != nil {
+		return nil, err
+	}
+	defer m.Close()
+
+	var manifest Manifest
+
+	if err := json.NewDecoder(m).Decode(&manifest); err != nil {
+		return nil, err
+	}
+	return manifest, nil
+}
+
+// Image exposes an image from the tarball at the provided path.
+func Image(opener Opener, tag *name.Tag) (v1.Image, error) {
+	img := &image{
+		opener: opener,
+		tag:    tag,
+	}
+	if err := img.loadTarDescriptorAndConfig(); err != nil {
+		return nil, err
+	}
+
+	// Peek at the first layer and see if it's compressed.
+	if len(img.imgDescriptor.Layers) > 0 {
+		compressed, err := img.areLayersCompressed()
+		if err != nil {
+			return nil, err
+		}
+		if compressed {
+			c := compressedImage{
+				image: img,
+			}
+			return partial.CompressedToImage(&c)
+		}
+	}
+
+	uc := uncompressedImage{
+		image: img,
+	}
+	return partial.UncompressedToImage(&uc)
+}
+
+func (i *image) MediaType() (types.MediaType, error) {
+	return types.DockerManifestSchema2, nil
+}
+
+// Descriptor stores the manifest data for a single image inside a `docker save` tarball.
+type Descriptor struct {
+	Config   string
+	RepoTags []string
+	Layers   []string
+
+	// Tracks foreign layer info. Key is DiffID.
+	LayerSources map[v1.Hash]v1.Descriptor `json:",omitempty"`
+}
+
+// Manifest represents the manifests of all images as the `manifest.json` file in a `docker save` tarball.
+type Manifest []Descriptor
+
+func (m Manifest) findDescriptor(tag *name.Tag) (*Descriptor, error) {
+	if tag == nil {
+		if len(m) != 1 {
+			return nil, errors.New("tarball must contain only a single image to be used with tarball.Image")
+		}
+		return &(m)[0], nil
+	}
+	for _, img := range m {
+		for _, tagStr := range img.RepoTags {
+			repoTag, err := name.NewTag(tagStr)
+			if err != nil {
+				return nil, err
+			}
+
+			// Compare the resolved names, since there are several ways to specify the same tag.
+			if repoTag.Name() == tag.Name() {
+				return &img, nil
+			}
+		}
+	}
+	return nil, fmt.Errorf("tag %s not found in tarball", tag)
+}
+
+func (i *image) areLayersCompressed() (bool, error) {
+	if len(i.imgDescriptor.Layers) == 0 {
+		return false, errors.New("0 layers found in image")
+	}
+	layer := i.imgDescriptor.Layers[0]
+	blob, err := extractFileFromTar(i.opener, layer)
+	if err != nil {
+		return false, err
+	}
+	defer blob.Close()
+
+	cp, _, err := comp.PeekCompression(blob)
+	if err != nil {
+		return false, err
+	}
+
+	return cp != compression.None, nil
+}
+
+func (i *image) loadTarDescriptorAndConfig() error {
+	m, err := extractFileFromTar(i.opener, "manifest.json")
+	if err != nil {
+		return err
+	}
+	defer m.Close()
+
+	if err := json.NewDecoder(m).Decode(&i.manifest); err != nil {
+		return err
+	}
+
+	if i.manifest == nil {
+		return errors.New("no valid manifest.json in tarball")
+	}
+
+	i.imgDescriptor, err = i.manifest.findDescriptor(i.tag)
+	if err != nil {
+		return err
+	}
+
+	cfg, err := extractFileFromTar(i.opener, i.imgDescriptor.Config)
+	if err != nil {
+		return err
+	}
+	defer cfg.Close()
+
+	i.config, err = io.ReadAll(cfg)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (i *image) RawConfigFile() ([]byte, error) {
+	return i.config, nil
+}
+
+// tarFile represents a single file inside a tar. Closing it closes the tar itself.
+type tarFile struct {
+	io.Reader
+	io.Closer
+}
+
+func extractFileFromTar(opener Opener, filePath string) (io.ReadCloser, error) {
+	f, err := opener()
+	if err != nil {
+		return nil, err
+	}
+	close := true
+	defer func() {
+		if close {
+			f.Close()
+		}
+	}()
+
+	tf := tar.NewReader(f)
+	for {
+		hdr, err := tf.Next()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		if hdr.Name == filePath {
+			if hdr.Typeflag == tar.TypeSymlink || hdr.Typeflag == tar.TypeLink {
+				currentDir := filepath.Dir(filePath)
+				return extractFileFromTar(opener, path.Join(currentDir, path.Clean(hdr.Linkname)))
+			}
+			close = false
+			return tarFile{
+				Reader: tf,
+				Closer: f,
+			}, nil
+		}
+	}
+	return nil, fmt.Errorf("file %s not found in tar", filePath)
+}
+
+// uncompressedLayerFromTarball implements partial.UncompressedLayer
+type uncompressedLayerFromTarball struct {
+	diffID    v1.Hash
+	mediaType types.MediaType
+	opener    Opener
+	filePath  string
+}
+
+// foreignUncompressedLayer implements partial.UncompressedLayer but returns
+// a custom descriptor. This allows the foreign layer URLs to be included in
+// the generated image manifest for uncompressed layers.
+type foreignUncompressedLayer struct {
+	uncompressedLayerFromTarball
+	desc v1.Descriptor
+}
+
+func (fl *foreignUncompressedLayer) Descriptor() (*v1.Descriptor, error) {
+	return &fl.desc, nil
+}
+
+// DiffID implements partial.UncompressedLayer
+func (ulft *uncompressedLayerFromTarball) DiffID() (v1.Hash, error) {
+	return ulft.diffID, nil
+}
+
+// Uncompressed implements partial.UncompressedLayer
+func (ulft *uncompressedLayerFromTarball) Uncompressed() (io.ReadCloser, error) {
+	return extractFileFromTar(ulft.opener, ulft.filePath)
+}
+
+func (ulft *uncompressedLayerFromTarball) MediaType() (types.MediaType, error) {
+	return ulft.mediaType, nil
+}
+
+func (i *uncompressedImage) LayerByDiffID(h v1.Hash) (partial.UncompressedLayer, error) {
+	cfg, err := partial.ConfigFile(i)
+	if err != nil {
+		return nil, err
+	}
+	for idx, diffID := range cfg.RootFS.DiffIDs {
+		if diffID == h {
+			// Technically the media type should be 'application/tar' but given that our
+			// v1.Layer doesn't force consumers to care about whether the layer is compressed
+			// we should be fine returning the DockerLayer media type
+			mt := types.DockerLayer
+			if bd, ok := i.imgDescriptor.LayerSources[h]; ok {
+				// Overwrite the mediaType for foreign layers.
+				return &foreignUncompressedLayer{
+					uncompressedLayerFromTarball: uncompressedLayerFromTarball{
+						diffID:    diffID,
+						mediaType: bd.MediaType,
+						opener:    i.opener,
+						filePath:  i.imgDescriptor.Layers[idx],
+					},
+					desc: bd,
+				}, nil
+			}
+			return &uncompressedLayerFromTarball{
+				diffID:    diffID,
+				mediaType: mt,
+				opener:    i.opener,
+				filePath:  i.imgDescriptor.Layers[idx],
+			}, nil
+		}
+	}
+	return nil, fmt.Errorf("diff id %q not found", h)
+}
+
+func (c *compressedImage) Manifest() (*v1.Manifest, error) {
+	c.manifestLock.Lock()
+	defer c.manifestLock.Unlock()
+	if c.manifest != nil {
+		return c.manifest, nil
+	}
+
+	b, err := c.RawConfigFile()
+	if err != nil {
+		return nil, err
+	}
+
+	cfgHash, cfgSize, err := v1.SHA256(bytes.NewReader(b))
+	if err != nil {
+		return nil, err
+	}
+
+	c.manifest = &v1.Manifest{
+		SchemaVersion: 2,
+		MediaType:     types.DockerManifestSchema2,
+		Config: v1.Descriptor{
+			MediaType: types.DockerConfigJSON,
+			Size:      cfgSize,
+			Digest:    cfgHash,
+		},
+	}
+
+	for i, p := range c.imgDescriptor.Layers {
+		cfg, err := partial.ConfigFile(c)
+		if err != nil {
+			return nil, err
+		}
+		diffid := cfg.RootFS.DiffIDs[i]
+		if d, ok := c.imgDescriptor.LayerSources[diffid]; ok {
+			// If it's a foreign layer, just append the descriptor so we can avoid
+			// reading the entire file.
+			c.manifest.Layers = append(c.manifest.Layers, d)
+		} else {
+			l, err := extractFileFromTar(c.opener, p)
+			if err != nil {
+				return nil, err
+			}
+			defer l.Close()
+			sha, size, err := v1.SHA256(l)
+			if err != nil {
+				return nil, err
+			}
+			c.manifest.Layers = append(c.manifest.Layers, v1.Descriptor{
+				MediaType: types.DockerLayer,
+				Size:      size,
+				Digest:    sha,
+			})
+		}
+	}
+	return c.manifest, nil
+}
+
+func (c *compressedImage) RawManifest() ([]byte, error) {
+	return partial.RawManifest(c)
+}
+
+// compressedLayerFromTarball implements partial.CompressedLayer
+type compressedLayerFromTarball struct {
+	desc     v1.Descriptor
+	opener   Opener
+	filePath string
+}
+
+// Digest implements partial.CompressedLayer
+func (clft *compressedLayerFromTarball) Digest() (v1.Hash, error) {
+	return clft.desc.Digest, nil
+}
+
+// Compressed implements partial.CompressedLayer
+func (clft *compressedLayerFromTarball) Compressed() (io.ReadCloser, error) {
+	return extractFileFromTar(clft.opener, clft.filePath)
+}
+
+// MediaType implements partial.CompressedLayer
+func (clft *compressedLayerFromTarball) MediaType() (types.MediaType, error) {
+	return clft.desc.MediaType, nil
+}
+
+// Size implements partial.CompressedLayer
+func (clft *compressedLayerFromTarball) Size() (int64, error) {
+	return clft.desc.Size, nil
+}
+
+func (c *compressedImage) LayerByDigest(h v1.Hash) (partial.CompressedLayer, error) {
+	m, err := c.Manifest()
+	if err != nil {
+		return nil, err
+	}
+	for i, l := range m.Layers {
+		if l.Digest == h {
+			fp := c.imgDescriptor.Layers[i]
+			return &compressedLayerFromTarball{
+				desc:     l,
+				opener:   c.opener,
+				filePath: fp,
+			}, nil
+		}
+	}
+	return nil, fmt.Errorf("blob %v not found", h)
+}