@@ -6,6 +6,7 @@ import (

 	"io/ioutil"

 	"os"

 	"path/filepath"

+	"strings"

 	"testing"

 	"github.com/docker/distribution/digest"

@@ -56,7 +57,7 @@ func newTestGraphDriver(t *testing.T) (graphdriver.Driver, func()) {

 	}

 }

-func newTestStore(t *testing.T) (Store, func()) {

+func newTestStore(t *testing.T) (Store, string, func()) {

 	td, err := ioutil.TempDir("", "layerstore-")

 	if err != nil {

 		t.Fatal(err)

@@ -72,7 +73,7 @@ func newTestStore(t *testing.T) (Store, func()) {

 		t.Fatal(err)

 	}

-	return ls, func() {

+	return ls, td, func() {

 		graphcleanup()

 		os.RemoveAll(td)

 	}

@@ -265,7 +266,7 @@ func assertLayerEqual(t *testing.T, l1, l2 Layer) {

 }

 func TestMountAndRegister(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	li := initWithFiles(newTestFile("testfile.txt", []byte("some test data"), 0644))

@@ -306,7 +307,7 @@ func TestMountAndRegister(t *testing.T) {

 }

 func TestLayerRelease(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	layer1, err := createLayer(ls, "", initWithFiles(newTestFile("layer1.txt", []byte("layer 1 file"), 0644)))

@@ -351,7 +352,7 @@ func TestLayerRelease(t *testing.T) {

 }

 func TestStoreRestore(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	layer1, err := createLayer(ls, "", initWithFiles(newTestFile("layer1.txt", []byte("layer 1 file"), 0644)))

@@ -472,7 +473,7 @@ func TestStoreRestore(t *testing.T) {

 }

 func TestTarStreamStability(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	files1 := []FileApplier{

@@ -668,7 +669,7 @@ func assertActivityCount(t *testing.T, l RWLayer, expected int) {

 }

 func TestRegisterExistingLayer(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	baseFiles := []FileApplier{

@@ -702,3 +703,69 @@ func TestRegisterExistingLayer(t *testing.T) {

 	assertReferences(t, layer2a, layer2b)

 }

+

+func TestTarStreamVerification(t *testing.T) {

+	ls, tmpdir, cleanup := newTestStore(t)

+	defer cleanup()

+

+	files1 := []FileApplier{

+		newTestFile("/foo", []byte("abc"), 0644),

+		newTestFile("/bar", []byte("def"), 0644),

+	}

+	files2 := []FileApplier{

+		newTestFile("/foo", []byte("abc"), 0644),

+		newTestFile("/bar", []byte("def"), 0600), // different perm

+	}

+

+	tar1, err := tarFromFiles(files1...)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	tar2, err := tarFromFiles(files2...)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	layer1, err := ls.Register(bytes.NewReader(tar1), "")

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	layer2, err := ls.Register(bytes.NewReader(tar2), "")

+	if err != nil {

+		t.Fatal(err)

+	}

+	id1 := digest.Digest(layer1.ChainID())

+	id2 := digest.Digest(layer2.ChainID())

+

+	// Replace tar data files

+	src, err := os.Open(filepath.Join(tmpdir, id1.Algorithm().String(), id1.Hex(), "tar-split.json.gz"))

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	dst, err := os.Create(filepath.Join(tmpdir, id2.Algorithm().String(), id2.Hex(), "tar-split.json.gz"))

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	if _, err := io.Copy(dst, src); err != nil {

+		t.Fatal(err)

+	}

+

+	src.Close()

+	dst.Close()

+

+	ts, err := layer2.TarStream()

+	if err != nil {

+		t.Fatal(err)

+	}

+	_, err = io.Copy(ioutil.Discard, ts)

+	if err == nil {

+		t.Fatal("expected data verification to fail")

+	}

+	if !strings.Contains(err.Error(), "could not verify layer data") {

+		t.Fatalf("wrong error returned from tarstream: %q", err)

+	}

+}

@@ -16,7 +16,7 @@ func graphDiffSize(ls Store, l Layer) (int64, error) {

 // Unix as Windows graph driver does not support Changes which is indirectly

 // invoked by calling DiffSize on the driver

 func TestLayerSize(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	content1 := []byte("Base contents")

@@ -268,7 +268,7 @@ func TestLayerMigrationNoTarsplit(t *testing.T) {

 }

 func TestMountMigration(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	baseFiles := []FileApplier{

@@ -11,7 +11,7 @@ import (

 )

 func TestMountInit(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	basefile := newTestFile("testfile.txt", []byte("base data!"), 0644)

@@ -63,7 +63,7 @@ func TestMountInit(t *testing.T) {

 }

 func TestMountSize(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	content1 := []byte("Base contents")

@@ -105,7 +105,7 @@ func TestMountSize(t *testing.T) {

 }

 func TestMountChanges(t *testing.T) {

-	ls, cleanup := newTestStore(t)

+	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

 	basefiles := []FileApplier{

@@ -1,6 +1,11 @@

 package layer

-import "io"

+import (

+	"fmt"

+	"io"

+

+	"github.com/docker/distribution/digest"

+)

 type roLayer struct {

 	chainID    ChainID

@@ -29,7 +34,11 @@ func (rl *roLayer) TarStream() (io.ReadCloser, error) {

 			pw.Close()

 		}

 	}()

-	return pr, nil

+	rc, err := newVerifiedReadCloser(pr, digest.Digest(rl.diffID))

+	if err != nil {

+		return nil, err

+	}

+	return rc, nil

 }

 func (rl *roLayer) ChainID() ChainID {

@@ -117,3 +126,39 @@ func storeLayer(tx MetadataTransaction, layer *roLayer) error {

 	return nil

 }

+

+func newVerifiedReadCloser(rc io.ReadCloser, dgst digest.Digest) (io.ReadCloser, error) {

+	verifier, err := digest.NewDigestVerifier(dgst)

+	if err != nil {

+		return nil, err

+	}

+	return &verifiedReadCloser{

+		rc:       rc,

+		dgst:     dgst,

+		verifier: verifier,

+	}, nil

+}

+

+type verifiedReadCloser struct {

+	rc       io.ReadCloser

+	dgst     digest.Digest

+	verifier digest.Verifier

+}

+

+func (vrc *verifiedReadCloser) Read(p []byte) (n int, err error) {

+	n, err = vrc.rc.Read(p)

+	if n > 0 {

+		if n, err := vrc.verifier.Write(p[:n]); err != nil {

+			return n, err

+		}

+	}

+	if err == io.EOF {

+		if !vrc.verifier.Verified() {

+			err = fmt.Errorf("could not verify layer data for: %s. This may be because internal files in the layer store were modified. Re-pulling or rebuilding this image may resolve the issue", vrc.dgst)

+		}

+	}

+	return

+}

+func (vrc *verifiedReadCloser) Close() error {

+	return vrc.rc.Close()

+}