Unpack filesystem and whitelist from /proc/self/mountinfo

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/cloud_prepper.go

@@ -0,0 +1,72 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"io/ioutil"
+	"strings"
+
+	"github.com/containers/image/docker"
+	"github.com/containers/image/types"
+	"github.com/docker/docker/client"
+)
+
+// CloudPrepper prepares images sourced from a Cloud registry
+type CloudPrepper struct {
+	Source      string
+	Client      *client.Client
+	ImageSource types.ImageSource
+}
+
+func (p CloudPrepper) Name() string {
+	return "Cloud Registry"
+}
+
+func (p CloudPrepper) GetSource() string {
+	return p.Source
+}
+
+func (p CloudPrepper) GetImage() (Image, error) {
+	image, err := getImage(p)
+	image.Type = ImageTypeCloud
+	return image, err
+}
+
+func (p CloudPrepper) GetFileSystem() (string, error) {
+	ref, err := docker.ParseReference("//" + p.Source)
+	if err != nil {
+		return "", err
+	}
+	sanitizedName := strings.Replace(p.Source, ":", "", -1)
+	sanitizedName = strings.Replace(sanitizedName, "/", "", -1)
+
+	path, err := ioutil.TempDir("", sanitizedName)
+	if err != nil {
+		return "", err
+	}
+
+	return path, GetFileSystemFromReference(ref, p.ImageSource, path, nil)
+}
+
+func (p CloudPrepper) GetConfig() (ConfigSchema, error) {
+	ref, err := docker.ParseReference("//" + p.Source)
+	if err != nil {
+		return ConfigSchema{}, err
+	}
+
+	return getConfigFromReference(ref, p.Source)
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/daemon_prepper.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"context"
+	"io/ioutil"
+	"strings"
+
+	"github.com/containers/image/docker/daemon"
+
+	"github.com/docker/docker/client"
+	"github.com/sirupsen/logrus"
+)
+
+type DaemonPrepper struct {
+	Source string
+	Client *client.Client
+}
+
+func (p DaemonPrepper) Name() string {
+	return "Local Daemon"
+}
+
+func (p DaemonPrepper) GetSource() string {
+	return p.Source
+}
+
+func (p DaemonPrepper) GetImage() (Image, error) {
+	image, err := getImage(p)
+	image.Type = ImageTypeDaemon
+	return image, err
+}
+
+func (p DaemonPrepper) GetFileSystem() (string, error) {
+	ref, err := daemon.ParseReference(p.Source)
+	if err != nil {
+		return "", err
+	}
+
+	src, err := ref.NewImageSource(nil)
+	if err != nil {
+		return "", err
+	}
+
+	sanitizedName := strings.Replace(p.Source, ":", "", -1)
+	sanitizedName = strings.Replace(sanitizedName, "/", "", -1)
+
+	path, err := ioutil.TempDir("", sanitizedName)
+	if err != nil {
+		return "", err
+	}
+	return path, GetFileSystemFromReference(ref, src, path, nil)
+}
+
+func (p DaemonPrepper) GetConfig() (ConfigSchema, error) {
+	ref, err := daemon.ParseReference(p.Source)
+	if err != nil {
+		return ConfigSchema{}, err
+	}
+	return getConfigFromReference(ref, p.Source)
+}
+
+func (p DaemonPrepper) GetHistory() []ImageHistoryItem {
+	history, err := p.Client.ImageHistory(context.Background(), p.Source)
+	if err != nil {
+		logrus.Errorf("Could not obtain image history for %s: %s", p.Source, err)
+	}
+	historyItems := []ImageHistoryItem{}
+	for _, item := range history {
+		historyItems = append(historyItems, ImageHistoryItem{CreatedBy: item.CreatedBy})
+	}
+	return historyItems
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/docker_utils.go

@@ -0,0 +1,123 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"archive/tar"
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/docker/docker/client"
+)
+
+type Event struct {
+	Status         string `json:"status"`
+	Error          string `json:"error"`
+	Progress       string `json:"progress"`
+	ProgressDetail struct {
+		Current int `json:"current"`
+		Total   int `json:"total"`
+	} `json:"progressDetail"`
+}
+
+func NewClient() (*client.Client, error) {
+	cli, err := client.NewEnvClient()
+	if err != nil {
+		return nil, fmt.Errorf("Error getting docker client: %s", err)
+	}
+	cli.NegotiateAPIVersion(context.Background())
+
+	return cli, nil
+}
+
+func getLayersFromManifest(r io.Reader) ([]string, error) {
+	type Manifest struct {
+		Layers []string
+	}
+
+	manifestJSON, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+
+	var imageManifest []Manifest
+	if err := json.Unmarshal(manifestJSON, &imageManifest); err != nil {
+		return []string{}, fmt.Errorf("Could not unmarshal manifest to get layer order: %s", err)
+	}
+	return imageManifest[0].Layers, nil
+}
+
+func unpackDockerSave(tarPath string, target string) error {
+	if _, ok := os.Stat(target); ok != nil {
+		os.MkdirAll(target, 0775)
+	}
+	f, err := os.Open(tarPath)
+	if err != nil {
+		return err
+	}
+
+	tr := tar.NewReader(f)
+
+	// Unpack the layers into a map, since we need to sort out the order later.
+	var layers []string
+	layerMap := map[string][]byte{}
+	for {
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
+		}
+
+		// Docker save contains files and directories. Ignore the directories.
+		// We care about the layers and the manifest. The layers look like:
+		// $SHA/layer.tar
+		// and they are referenced that way in the manifest.
+		switch t := hdr.Typeflag; t {
+		case tar.TypeReg:
+			if hdr.Name == "manifest.json" {
+				layers, err = getLayersFromManifest(tr)
+				if err != nil {
+					return err
+				}
+			} else if strings.HasSuffix(hdr.Name, ".tar") {
+				layerMap[hdr.Name], err = ioutil.ReadAll(tr)
+				if err != nil {
+					return err
+				}
+			}
+		case tar.TypeDir:
+			continue
+		default:
+			return fmt.Errorf("unsupported file type %v found in file %s tar %s", t, hdr.Name, tarPath)
+		}
+	}
+
+	for _, layer := range layers {
+		if err = UnTar(bytes.NewReader(layerMap[layer]), target, nil); err != nil {
+			return fmt.Errorf("Could not unpack layer %s: %s", layer, err)
+		}
+	}
+	return nil
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/fs_utils.go

@@ -0,0 +1,181 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Directory stores a representation of a file directory.
+type Directory struct {
+	Root    string
+	Content []string
+}
+
+type DirectoryEntry struct {
+	Name string
+	Size int64
+}
+
+func GetSize(path string) int64 {
+	stat, err := os.Stat(path)
+	if err != nil {
+		logrus.Errorf("Could not obtain size for %s: %s", path, err)
+		return -1
+	}
+	if stat.IsDir() {
+		size, err := getDirectorySize(path)
+		if err != nil {
+			logrus.Errorf("Could not obtain directory size for %s: %s", path, err)
+		}
+		return size
+	}
+	return stat.Size()
+}
+
+//GetFileContents returns the contents of a file at the specified path
+func GetFileContents(path string) (*string, error) {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		return nil, err
+	}
+
+	contents, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	strContents := string(contents)
+	//If file is empty, return nil
+	if strContents == "" {
+		return nil, nil
+	}
+	return &strContents, nil
+}
+
+func getDirectorySize(path string) (int64, error) {
+	var size int64
+	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return err
+	})
+	return size, err
+}
+
+// GetDirectoryContents converts the directory starting at the provided path into a Directory struct.
+func GetDirectory(path string, deep bool) (Directory, error) {
+	var directory Directory
+	directory.Root = path
+	var err error
+	if deep {
+		walkFn := func(currPath string, info os.FileInfo, err error) error {
+			newContent := strings.TrimPrefix(currPath, directory.Root)
+			if newContent != "" {
+				directory.Content = append(directory.Content, newContent)
+			}
+			return nil
+		}
+
+		err = filepath.Walk(path, walkFn)
+	} else {
+		contents, err := ioutil.ReadDir(path)
+		if err != nil {
+			return directory, err
+		}
+
+		for _, file := range contents {
+			fileName := "/" + file.Name()
+			directory.Content = append(directory.Content, fileName)
+		}
+	}
+	return directory, err
+}
+
+func GetDirectoryEntries(d Directory) []DirectoryEntry {
+	return CreateDirectoryEntries(d.Root, d.Content)
+}
+
+func CreateDirectoryEntries(root string, entryNames []string) (entries []DirectoryEntry) {
+	for _, name := range entryNames {
+		entryPath := filepath.Join(root, name)
+		size := GetSize(entryPath)
+
+		entry := DirectoryEntry{
+			Name: name,
+			Size: size,
+		}
+		entries = append(entries, entry)
+	}
+	return entries
+}
+
+func CheckSameFile(f1name, f2name string) (bool, error) {
+	// Check first if files differ in size and immediately return
+	f1stat, err := os.Stat(f1name)
+	if err != nil {
+		return false, err
+	}
+	f2stat, err := os.Stat(f2name)
+	if err != nil {
+		return false, err
+	}
+
+	if f1stat.Size() != f2stat.Size() {
+		return false, nil
+	}
+
+	// Next, check file contents
+	f1, err := ioutil.ReadFile(f1name)
+	if err != nil {
+		return false, err
+	}
+	f2, err := ioutil.ReadFile(f2name)
+	if err != nil {
+		return false, err
+	}
+
+	if !bytes.Equal(f1, f2) {
+		return false, nil
+	}
+	return true, nil
+}
+
+// HasFilepathPrefix checks if the given file path begins with prefix
+func HasFilepathPrefix(path, prefix string) bool {
+	path = filepath.Clean(path)
+	prefix = filepath.Clean(prefix)
+	pathArray := strings.Split(path, "/")
+	prefixArray := strings.Split(prefix, "/")
+
+	if len(pathArray) < len(prefixArray) {
+		return false
+	}
+	for index := range prefixArray {
+		if prefixArray[index] == pathArray[index] {
+			continue
+		}
+		return false
+	}
+	return true
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/image_prep_utils.go

@@ -0,0 +1,214 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"archive/tar"
+	"encoding/json"
+	"errors"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/GoogleCloudPlatform/container-diff/cmd/util/output"
+	"github.com/containers/image/docker"
+	"github.com/containers/image/manifest"
+	"github.com/containers/image/pkg/compression"
+	"github.com/containers/image/types"
+	"github.com/sirupsen/logrus"
+)
+
+type Prepper interface {
+	Name() string
+	GetConfig() (ConfigSchema, error)
+	GetFileSystem() (string, error)
+	GetImage() (Image, error)
+	GetSource() string
+}
+
+type ImageType int
+
+const (
+	ImageTypeTar ImageType = iota
+	ImageTypeDaemon
+	ImageTypeCloud
+)
+
+type Image struct {
+	Source string
+	FSPath string
+	Config ConfigSchema
+	Type   ImageType
+}
+
+func (i *Image) IsTar() bool {
+	return i.Type == ImageTypeTar
+}
+
+func (i *Image) IsDaemon() bool {
+	return i.Type == ImageTypeDaemon
+}
+
+func (i *Image) IsCloud() bool {
+	return i.Type == ImageTypeCloud
+}
+
+func (i *Image) GetRemoteDigest() (string, error) {
+	ref, err := docker.ParseReference("//" + i.Source)
+	if err != nil {
+		return "", err
+	}
+	return getDigestFromReference(ref, i.Source)
+}
+
+func (i *Image) GetName() string {
+	return strings.Split(i.Source, ":")[0]
+}
+
+type ImageHistoryItem struct {
+	CreatedBy string `json:"created_by"`
+}
+
+type ConfigObject struct {
+	Env          []string            `json:"Env"`
+	Entrypoint   []string            `json:"Entrypoint"`
+	ExposedPorts map[string]struct{} `json:"ExposedPorts"`
+	Cmd          []string            `json:"Cmd"`
+	Volumes      map[string]struct{} `json:"Volumes"`
+	Workdir      string              `json:"WorkingDir"`
+	Labels       map[string]string   `json:"Labels"`
+}
+
+type ConfigSchema struct {
+	Config  ConfigObject       `json:"config"`
+	History []ImageHistoryItem `json:"history"`
+}
+
+func getImage(p Prepper) (Image, error) {
+	output.PrintToStdErr("Retrieving image %s from source %s\n", p.GetSource(), p.Name())
+	imgPath, err := p.GetFileSystem()
+	if err != nil {
+		return Image{}, err
+	}
+
+	config, err := p.GetConfig()
+	if err != nil {
+		logrus.Error("Error retrieving History: ", err)
+	}
+
+	logrus.Infof("Finished prepping image %s", p.GetSource())
+	return Image{
+		Source: p.GetSource(),
+		FSPath: imgPath,
+		Config: config,
+	}, nil
+}
+
+func getImageFromTar(tarPath string) (string, error) {
+	logrus.Info("Extracting image tar to obtain image file system")
+	tempPath, err := ioutil.TempDir("", ".container-diff")
+	if err != nil {
+		return "", err
+	}
+	return tempPath, unpackDockerSave(tarPath, tempPath)
+}
+
+func GetFileSystemFromReference(ref types.ImageReference, imgSrc types.ImageSource, path string, whitelist []string) error {
+	img, err := ref.NewImage(nil)
+	if err != nil {
+		return err
+	}
+	defer img.Close()
+	for _, b := range img.LayerInfos() {
+		bi, _, err := imgSrc.GetBlob(b)
+		if err != nil {
+			return err
+		}
+		defer bi.Close()
+		f, reader, err := compression.DetectCompression(bi)
+		if err != nil {
+			return err
+		}
+		// Decompress if necessary.
+		if f != nil {
+			reader, err = f(reader)
+			if err != nil {
+				return err
+			}
+		}
+		tr := tar.NewReader(reader)
+		if err := unpackTar(tr, path, whitelist); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func getDigestFromReference(ref types.ImageReference, source string) (string, error) {
+	img, err := ref.NewImage(nil)
+	if err != nil {
+		logrus.Errorf("Error referencing image %s from registry: %s", source, err)
+		return "", errors.New("Could not obtain image digest")
+	}
+	defer img.Close()
+
+	rawManifest, _, err := img.Manifest()
+	if err != nil {
+		logrus.Errorf("Error referencing image %s from registry: %s", source, err)
+		return "", errors.New("Could not obtain image digest")
+	}
+
+	digest, err := manifest.Digest(rawManifest)
+	if err != nil {
+		logrus.Errorf("Error referencing image %s from registry: %s", source, err)
+		return "", errors.New("Could not obtain image digest")
+	}
+
+	return digest.String(), nil
+}
+
+func getConfigFromReference(ref types.ImageReference, source string) (ConfigSchema, error) {
+	img, err := ref.NewImage(nil)
+	if err != nil {
+		logrus.Errorf("Error referencing image %s from registry: %s", source, err)
+		return ConfigSchema{}, errors.New("Could not obtain image config")
+	}
+	defer img.Close()
+
+	configBlob, err := img.ConfigBlob()
+	if err != nil {
+		logrus.Errorf("Error obtaining config blob for image %s from registry: %s", source, err)
+		return ConfigSchema{}, errors.New("Could not obtain image config")
+	}
+
+	var config ConfigSchema
+	err = json.Unmarshal(configBlob, &config)
+	if err != nil {
+		logrus.Errorf("Error with config file struct for image %s: %s", source, err)
+		return ConfigSchema{}, errors.New("Could not obtain image config")
+	}
+	return config, nil
+}
+
+func CleanupImage(image Image) {
+	if image.FSPath != "" {
+		logrus.Infof("Removing image filesystem directory %s from system", image.FSPath)
+		if err := os.RemoveAll(image.FSPath); err != nil {
+			logrus.Error(err.Error())
+		}
+	}
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/image_utils.go

@@ -0,0 +1,69 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/docker/docker/pkg/system"
+	"github.com/sirupsen/logrus"
+)
+
+func GetImageLayers(pathToImage string) []string {
+	layers := []string{}
+	contents, err := ioutil.ReadDir(pathToImage)
+	if err != nil {
+		logrus.Error(err.Error())
+	}
+
+	for _, file := range contents {
+		if file.IsDir() {
+			layers = append(layers, file.Name())
+		}
+	}
+	return layers
+}
+
+// copyToFile writes the content of the reader to the specified file
+func copyToFile(outfile string, r io.Reader) error {
+	// We use sequential file access here to avoid depleting the standby list
+	// on Windows. On Linux, this is a call directly to ioutil.TempFile
+	tmpFile, err := system.TempFileSequential(filepath.Dir(outfile), ".docker_temp_")
+	if err != nil {
+		return err
+	}
+
+	tmpPath := tmpFile.Name()
+
+	_, err = io.Copy(tmpFile, r)
+	tmpFile.Close()
+
+	if err != nil {
+		os.Remove(tmpPath)
+		return err
+	}
+
+	if err = os.Rename(tmpPath, outfile); err != nil {
+		os.Remove(tmpPath)
+		return err
+	}
+
+	return nil
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/tar_prepper.go

@@ -0,0 +1,98 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"encoding/json"
+	"errors"
+	"github.com/containers/image/docker/tarfile"
+	"github.com/docker/docker/client"
+	"github.com/sirupsen/logrus"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+type TarPrepper struct {
+	Source string
+	Client *client.Client
+}
+
+func (p TarPrepper) Name() string {
+	return "Tar Archive"
+}
+
+func (p TarPrepper) GetSource() string {
+	return p.Source
+}
+
+func (p TarPrepper) GetImage() (Image, error) {
+	image, err := getImage(p)
+	image.Type = ImageTypeTar
+	return image, err
+}
+
+func (p TarPrepper) GetFileSystem() (string, error) {
+	return getImageFromTar(p.Source)
+}
+
+func (p TarPrepper) GetConfig() (ConfigSchema, error) {
+	tempDir, err := ioutil.TempDir("", ".container-diff")
+	if err != nil {
+		return ConfigSchema{}, nil
+	}
+	defer os.RemoveAll(tempDir)
+	f, err := os.Open(p.Source)
+	if err != nil {
+		return ConfigSchema{}, err
+	}
+	defer f.Close()
+	if err := UnTar(f, tempDir, nil); err != nil {
+		return ConfigSchema{}, err
+	}
+
+	var config ConfigSchema
+	// First open the manifest, then find the referenced config.
+	manifestPath := filepath.Join(tempDir, "manifest.json")
+	contents, err := ioutil.ReadFile(manifestPath)
+	if err != nil {
+		return ConfigSchema{}, err
+	}
+
+	manifests := []tarfile.ManifestItem{}
+	if err := json.Unmarshal(contents, &manifests); err != nil {
+		return ConfigSchema{}, err
+	}
+
+	if len(manifests) != 1 {
+		return ConfigSchema{}, errors.New("specified tar file contains multiple images")
+	}
+
+	cfgFilename := filepath.Join(tempDir, manifests[0].Config)
+	file, err := ioutil.ReadFile(cfgFilename)
+	if err != nil {
+		logrus.Errorf("Could not read config file %s: %s", cfgFilename, err)
+		return ConfigSchema{}, errors.New("Could not obtain image config")
+	}
+	err = json.Unmarshal(file, &config)
+	if err != nil {
+		logrus.Errorf("Could not marshal config file %s: %s", cfgFilename, err)
+		return ConfigSchema{}, errors.New("Could not obtain image config")
+	}
+
+	return config, nil
+}

vendor/github.com/GoogleCloudPlatform/container-diff/pkg/util/tar_utils.go

@@ -0,0 +1,166 @@
+/*
+Copyright 2017 Google, Inc. 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 util
+
+import (
+	"archive/tar"
+	"github.com/sirupsen/logrus"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func unpackTar(tr *tar.Reader, path string, whitelist []string) error {
+	for {
+		header, err := tr.Next()
+		if err == io.EOF {
+			// end of tar archive
+			break
+		}
+		if err != nil {
+			logrus.Error("Error getting next tar header")
+			return err
+		}
+		if strings.Contains(header.Name, ".wh.") {
+			rmPath := filepath.Join(path, header.Name)
+			// Remove the .wh file if it was extracted.
+			if _, err := os.Stat(rmPath); !os.IsNotExist(err) {
+				if err := os.Remove(rmPath); err != nil {
+					logrus.Error(err)
+				}
+			}
+
+			// Remove the whited-out path.
+			newName := strings.Replace(rmPath, ".wh.", "", 1)
+			if err = os.RemoveAll(newName); err != nil {
+				logrus.Error(err)
+			}
+			continue
+		}
+		target := filepath.Join(path, header.Name)
+		// Make sure the target isn't part of the whitelist
+		if checkWhitelist(target, whitelist) {
+			continue
+		}
+		mode := header.FileInfo().Mode()
+		switch header.Typeflag {
+
+		// if its a dir and it doesn't exist create it
+		case tar.TypeDir:
+			if _, err := os.Stat(target); os.IsNotExist(err) {
+				if err := os.MkdirAll(target, mode); err != nil {
+					return err
+				}
+				// In some cases, MkdirAll doesn't change the permissions, so run Chmod
+				if err := os.Chmod(target, mode); err != nil {
+					return err
+				}
+			}
+
+		// if it's a file create it
+		case tar.TypeReg:
+			// It's possible for a file to be included before the directory it's in is created.
+			baseDir := filepath.Dir(target)
+			if _, err := os.Stat(baseDir); os.IsNotExist(err) {
+				logrus.Debugf("baseDir %s for file %s does not exist. Creating.", baseDir, target)
+				if err := os.MkdirAll(baseDir, 0755); err != nil {
+					return err
+				}
+			}
+			// It's possible we end up creating files that can't be overwritten based on their permissions.
+			// Explicitly delete an existing file before continuing.
+			if _, err := os.Stat(target); !os.IsNotExist(err) {
+				logrus.Debugf("Removing %s for overwrite.", target)
+				if err := os.Remove(target); err != nil {
+					return err
+				}
+			}
+
+			currFile, err := os.Create(target)
+			if err != nil {
+				logrus.Errorf("Error creating file %s %s", target, err)
+				return err
+			}
+			// manually set permissions on file, since the default umask (022) will interfere
+			if err = os.Chmod(target, mode); err != nil {
+				logrus.Errorf("Error updating file permissions on %s", target)
+				return err
+			}
+			_, err = io.Copy(currFile, tr)
+			if err != nil {
+				return err
+			}
+			currFile.Close()
+		case tar.TypeSymlink:
+			// It's possible we end up creating files that can't be overwritten based on their permissions.
+			// Explicitly delete an existing file before continuing.
+			if _, err := os.Stat(target); !os.IsNotExist(err) {
+				logrus.Debugf("Removing %s to create symlink.", target)
+				if err := os.RemoveAll(target); err != nil {
+					logrus.Debugf("Unable to remove %s: %s", target, err)
+				}
+			}
+
+			if err = os.Symlink(header.Linkname, target); err != nil {
+				logrus.Errorf("Failed to create symlink between %s and %s: %s", header.Linkname, target, err)
+			}
+		}
+	}
+	return nil
+}
+
+func checkWhitelist(target string, whitelist []string) bool {
+	for _, w := range whitelist {
+		if HasFilepathPrefix(target, w) {
+			logrus.Debugf("Not extracting %s, as it has prefix %s which is whitelisted", target, w)
+			return true
+		}
+	}
+	return false
+}
+
+// UnTar takes in a path to a tar file and writes the untarred version to the provided target.
+// Only untars one level, does not untar nested tars.
+func UnTar(r io.Reader, target string, whitelist []string) error {
+	if _, ok := os.Stat(target); ok != nil {
+		os.MkdirAll(target, 0775)
+	}
+
+	tr := tar.NewReader(r)
+	if err := unpackTar(tr, target, whitelist); err != nil {
+		return err
+	}
+	return nil
+}
+
+func IsTar(path string) bool {
+	return filepath.Ext(path) == ".tar" ||
+		filepath.Ext(path) == ".tar.gz" ||
+		filepath.Ext(path) == ".tgz"
+}
+
+func CheckTar(image string) bool {
+	if strings.TrimSuffix(image, ".tar") == image {
+		return false
+	}
+	if _, err := os.Stat(image); err != nil {
+		logrus.Errorf("%s does not exist", image)
+		return false
+	}
+	return true
+}