Merge pull request #1687 from RichardScothern/signature-store

Remove signature store from registry.
This commit is contained in:
Richard Scothern 2016-05-31 09:09:39 -07:00
commit b370cfc940
14 changed files with 33 additions and 378 deletions

View file

@ -1067,13 +1067,13 @@ func testManifestAPISchema1(t *testing.T, env *testEnv, imageName reference.Name
t.Fatalf("error decoding fetched manifest: %v", err)
}
// check two signatures were roundtripped
// check only 1 signature is returned
signatures, err = fetchedManifestByDigest.Signatures()
if err != nil {
t.Fatal(err)
}
if len(signatures) != 2 {
if len(signatures) != 1 {
t.Fatalf("expected 2 signature from manifest, got: %d", len(signatures))
}

View file

@ -155,6 +155,7 @@ func NewApp(ctx context.Context, config *configuration.Configuration) *App {
app.configureRedis(config)
app.configureLogHook(config)
options := registrymiddleware.GetRegistryOptions()
if config.Compatibility.Schema1.TrustKey != "" {
app.trustKey, err = libtrust.LoadKeyFile(config.Compatibility.Schema1.TrustKey)
if err != nil {
@ -169,6 +170,8 @@ func NewApp(ctx context.Context, config *configuration.Configuration) *App {
}
}
options = append(options, storage.Schema1SigningKey(app.trustKey))
if config.HTTP.Host != "" {
u, err := url.Parse(config.HTTP.Host)
if err != nil {
@ -177,17 +180,10 @@ func NewApp(ctx context.Context, config *configuration.Configuration) *App {
app.httpHost = *u
}
options := registrymiddleware.GetRegistryOptions()
if app.isCache {
options = append(options, storage.DisableDigestResumption)
}
if config.Compatibility.Schema1.DisableSignatureStore {
options = append(options, storage.DisableSchema1Signatures)
options = append(options, storage.Schema1SigningKey(app.trustKey))
}
// configure deletion
if d, ok := config.Storage["delete"]; ok {
e, ok := d["enabled"]

View file

@ -60,12 +60,6 @@ func (sm statsManifest) Put(ctx context.Context, manifest distribution.Manifest,
return sm.manifests.Put(ctx, manifest)
}
/*func (sm statsManifest) Enumerate(ctx context.Context, manifests []distribution.Manifest, last distribution.Manifest) (n int, err error) {
sm.stats["enumerate"]++
return sm.manifests.Enumerate(ctx, manifests, last)
}
*/
type mockChallenger struct {
sync.Mutex
count int
@ -75,7 +69,6 @@ type mockChallenger struct {
func (m *mockChallenger) tryEstablishChallenges(context.Context) error {
m.Lock()
defer m.Unlock()
m.count++
return nil
}
@ -93,9 +86,15 @@ func newManifestStoreTestEnv(t *testing.T, name, tag string) *manifestStoreTestE
if err != nil {
t.Fatalf("unable to parse reference: %s", err)
}
k, err := libtrust.GenerateECP256PrivateKey()
if err != nil {
t.Fatal(err)
}
ctx := context.Background()
truthRegistry, err := storage.NewRegistry(ctx, inmemory.New(), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()))
truthRegistry, err := storage.NewRegistry(ctx, inmemory.New(),
storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()),
storage.Schema1SigningKey(k))
if err != nil {
t.Fatalf("error creating registry: %v", err)
}
@ -117,7 +116,7 @@ func newManifestStoreTestEnv(t *testing.T, name, tag string) *manifestStoreTestE
t.Fatalf(err.Error())
}
localRegistry, err := storage.NewRegistry(ctx, inmemory.New(), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), storage.EnableRedirect, storage.DisableDigestResumption)
localRegistry, err := storage.NewRegistry(ctx, inmemory.New(), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), storage.EnableRedirect, storage.DisableDigestResumption, storage.Schema1SigningKey(k))
if err != nil {
t.Fatalf("error creating registry: %v", err)
}

View file

@ -69,7 +69,7 @@ var GCCmd = &cobra.Command{
os.Exit(1)
}
registry, err := storage.NewRegistry(ctx, driver, storage.DisableSchema1Signatures, storage.Schema1SigningKey(k))
registry, err := storage.NewRegistry(ctx, driver, storage.Schema1SigningKey(k))
if err != nil {
fmt.Fprintf(os.Stderr, "failed to construct registry: %v", err)
os.Exit(1)

View file

@ -75,7 +75,6 @@ func (bs *blobStore) Put(ctx context.Context, mediaType string, p []byte) (distr
}
// TODO(stevvooe): Write out mediatype here, as well.
return distribution.Descriptor{
Size: int64(len(p)),

View file

@ -6,7 +6,6 @@ import (
"github.com/docker/distribution"
"github.com/docker/distribution/context"
"github.com/docker/distribution/digest"
"github.com/docker/distribution/manifest/schema1"
"github.com/docker/distribution/manifest/schema2"
"github.com/docker/distribution/reference"
"github.com/docker/distribution/registry/storage/driver"
@ -71,22 +70,6 @@ func MarkAndSweep(ctx context.Context, storageDriver driver.StorageDriver, regis
}
switch manifest.(type) {
case *schema1.SignedManifest:
signaturesGetter, ok := manifestService.(distribution.SignaturesGetter)
if !ok {
return fmt.Errorf("unable to convert ManifestService into SignaturesGetter")
}
signatures, err := signaturesGetter.GetSignatures(ctx, dgst)
if err != nil {
return fmt.Errorf("failed to get signatures for signed manifest: %v", err)
}
for _, signatureDigest := range signatures {
if dryRun {
emit("%s: marking signature %s", repoName, signatureDigest)
}
markSet[signatureDigest] = struct{}{}
}
break
case *schema2.DeserializedManifest:
config := manifest.(*schema2.DeserializedManifest).Config
if dryRun {

View file

@ -12,6 +12,7 @@ import (
"github.com/docker/distribution/registry/storage/driver"
"github.com/docker/distribution/registry/storage/driver/inmemory"
"github.com/docker/distribution/testutil"
"github.com/docker/libtrust"
)
type image struct {
@ -22,7 +23,11 @@ type image struct {
func createRegistry(t *testing.T, driver driver.StorageDriver) distribution.Namespace {
ctx := context.Background()
registry, err := NewRegistry(ctx, driver, EnableDelete)
k, err := libtrust.GenerateECP256PrivateKey()
if err != nil {
t.Fatal(err)
}
registry, err := NewRegistry(ctx, driver, EnableDelete, Schema1SigningKey(k))
if err != nil {
t.Fatalf("Failed to construct namespace")
}
@ -139,13 +144,13 @@ func TestNoDeletionNoEffect(t *testing.T) {
ctx := context.Background()
inmemoryDriver := inmemory.New()
registry := createRegistry(t, inmemoryDriver)
registry := createRegistry(t, inmemory.New())
repo := makeRepository(t, registry, "palailogos")
manifestService, err := repo.Manifests(ctx)
image1 := uploadRandomSchema1Image(t, repo)
image2 := uploadRandomSchema1Image(t, repo)
image3 := uploadRandomSchema2Image(t, repo)
uploadRandomSchema2Image(t, repo)
// construct manifestlist for fun.
blobstatter := registry.BlobStatter()
@ -160,20 +165,17 @@ func TestNoDeletionNoEffect(t *testing.T) {
t.Fatalf("Failed to add manifest list: %v", err)
}
before := allBlobs(t, registry)
// Run GC
err = MarkAndSweep(context.Background(), inmemoryDriver, registry, false)
if err != nil {
t.Fatalf("Failed mark and sweep: %v", err)
}
blobs := allBlobs(t, registry)
// the +1 at the end is for the manifestList
// the first +3 at the end for each manifest's blob
// the second +3 at the end for each manifest's signature/config layer
totalBlobCount := len(image1.layers) + len(image2.layers) + len(image3.layers) + 1 + 3 + 3
if len(blobs) != totalBlobCount {
t.Fatalf("Garbage collection affected storage")
after := allBlobs(t, registry)
if len(before) != len(after) {
t.Fatalf("Garbage collection affected storage: %d != %d", len(before), len(after))
}
}

View file

@ -2,7 +2,6 @@ package storage
import (
"fmt"
"path"
"encoding/json"
"github.com/docker/distribution"
@ -12,7 +11,6 @@ import (
"github.com/docker/distribution/manifest/manifestlist"
"github.com/docker/distribution/manifest/schema1"
"github.com/docker/distribution/manifest/schema2"
"github.com/docker/distribution/registry/storage/driver"
)
// A ManifestHandler gets and puts manifests of a particular type.
@ -141,48 +139,3 @@ func (ms *manifestStore) Enumerate(ctx context.Context, ingester func(digest.Dig
})
return err
}
// Only valid for schema1 signed manifests
func (ms *manifestStore) GetSignatures(ctx context.Context, manifestDigest digest.Digest) ([]digest.Digest, error) {
// sanity check that digest refers to a schema1 digest
manifest, err := ms.Get(ctx, manifestDigest)
if err != nil {
return nil, err
}
if _, ok := manifest.(*schema1.SignedManifest); !ok {
return nil, fmt.Errorf("digest %v is not for schema1 manifest", manifestDigest)
}
signaturesPath, err := pathFor(manifestSignaturesPathSpec{
name: ms.repository.Named().Name(),
revision: manifestDigest,
})
if err != nil {
return nil, err
}
var digests []digest.Digest
alg := string(digest.SHA256)
signaturePaths, err := ms.blobStore.driver.List(ctx, path.Join(signaturesPath, alg))
switch err.(type) {
case nil:
break
case driver.PathNotFoundError:
// Manifest may have been pushed with signature store disabled
return digests, nil
default:
return nil, err
}
for _, sigPath := range signaturePaths {
sigdigest, err := digest.ParseDigest(alg + ":" + path.Base(sigPath))
if err != nil {
// merely found not a digest
continue
}
digests = append(digests, sigdigest)
}
return digests, nil
}

View file

@ -52,15 +52,11 @@ func newManifestStoreTestEnv(t *testing.T, name reference.Named, tag string, opt
}
func TestManifestStorage(t *testing.T) {
testManifestStorage(t, BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), EnableDelete, EnableRedirect)
}
func TestManifestStorageDisabledSignatures(t *testing.T) {
k, err := libtrust.GenerateECP256PrivateKey()
if err != nil {
t.Fatal(err)
}
testManifestStorage(t, BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), EnableDelete, EnableRedirect, DisableSchema1Signatures, Schema1SigningKey(k))
testManifestStorage(t, BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), EnableDelete, EnableRedirect, Schema1SigningKey(k))
}
func testManifestStorage(t *testing.T, options ...RegistryOption) {
@ -71,7 +67,6 @@ func testManifestStorage(t *testing.T, options ...RegistryOption) {
if err != nil {
t.Fatal(err)
}
equalSignatures := env.registry.(*registry).schema1SignaturesEnabled
m := schema1.Manifest{
Versioned: manifest.Versioned{
@ -175,12 +170,6 @@ func testManifestStorage(t *testing.T, options ...RegistryOption) {
t.Fatalf("fetched payload does not match original payload: %q != %q", fetchedManifest.Canonical, sm.Canonical)
}
if equalSignatures {
if !reflect.DeepEqual(fetchedManifest, sm) {
t.Fatalf("fetched manifest not equal: %#v != %#v", fetchedManifest.Manifest, sm.Manifest)
}
}
_, pl, err := fetchedManifest.Payload()
if err != nil {
t.Fatalf("error getting payload %#v", err)
@ -223,12 +212,6 @@ func testManifestStorage(t *testing.T, options ...RegistryOption) {
t.Fatalf("fetched manifest not equal: %q != %q", byDigestManifest.Canonical, fetchedManifest.Canonical)
}
if equalSignatures {
if !reflect.DeepEqual(fetchedByDigest, fetchedManifest) {
t.Fatalf("fetched manifest not equal: %#v != %#v", fetchedByDigest, fetchedManifest)
}
}
sigs, err := fetchedJWS.Signatures()
if err != nil {
t.Fatalf("unable to extract signatures: %v", err)
@ -285,17 +268,6 @@ func testManifestStorage(t *testing.T, options ...RegistryOption) {
t.Fatalf("unexpected error verifying manifest: %v", err)
}
// Assemble our payload and two signatures to get what we expect!
expectedJWS, err := libtrust.NewJSONSignature(payload, sigs[0], sigs2[0])
if err != nil {
t.Fatalf("unexpected error merging jws: %v", err)
}
expectedSigs, err := expectedJWS.Signatures()
if err != nil {
t.Fatalf("unexpected error getting expected signatures: %v", err)
}
_, pl, err = fetched.Payload()
if err != nil {
t.Fatalf("error getting payload %#v", err)
@ -315,19 +287,6 @@ func testManifestStorage(t *testing.T, options ...RegistryOption) {
t.Fatalf("payloads are not equal")
}
if equalSignatures {
receivedSigs, err := receivedJWS.Signatures()
if err != nil {
t.Fatalf("error getting signatures: %v", err)
}
for i, sig := range receivedSigs {
if !bytes.Equal(sig, expectedSigs[i]) {
t.Fatalf("mismatched signatures from remote: %v != %v", string(sig), string(expectedSigs[i]))
}
}
}
// Test deleting manifests
err = ms.Delete(ctx, dgst)
if err != nil {

View file

@ -30,8 +30,6 @@ const (
// revisions
// -> <manifest digest path>
// -> link
// -> signatures
// <algorithm>/<digest>/link
// tags/<tag>
// -> current/link
// -> index
@ -62,8 +60,7 @@ const (
//
// The third component of the repository directory is the manifests store,
// which is made up of a revision store and tag store. Manifests are stored in
// the blob store and linked into the revision store. Signatures are separated
// from the manifest payload data and linked into the blob store, as well.
// the blob store and linked into the revision store.
// While the registry can save all revisions of a manifest, no relationship is
// implied as to the ordering of changes to a manifest. The tag store provides
// support for name, tag lookups of manifests, using "current/link" under a
@ -77,8 +74,6 @@ const (
// manifestRevisionsPathSpec: <root>/v2/repositories/<name>/_manifests/revisions/
// manifestRevisionPathSpec: <root>/v2/repositories/<name>/_manifests/revisions/<algorithm>/<hex digest>/
// manifestRevisionLinkPathSpec: <root>/v2/repositories/<name>/_manifests/revisions/<algorithm>/<hex digest>/link
// manifestSignaturesPathSpec: <root>/v2/repositories/<name>/_manifests/revisions/<algorithm>/<hex digest>/signatures/
// manifestSignatureLinkPathSpec: <root>/v2/repositories/<name>/_manifests/revisions/<algorithm>/<hex digest>/signatures/<algorithm>/<hex digest>/link
//
// Tags:
//
@ -148,33 +143,6 @@ func pathFor(spec pathSpec) (string, error) {
}
return path.Join(root, "link"), nil
case manifestSignaturesPathSpec:
root, err := pathFor(manifestRevisionPathSpec{
name: v.name,
revision: v.revision,
})
if err != nil {
return "", err
}
return path.Join(root, "signatures"), nil
case manifestSignatureLinkPathSpec:
root, err := pathFor(manifestSignaturesPathSpec{
name: v.name,
revision: v.revision,
})
if err != nil {
return "", err
}
signatureComponents, err := digestPathComponents(v.signature, false)
if err != nil {
return "", err
}
return path.Join(root, path.Join(append(signatureComponents, "link")...)), nil
case manifestTagsPathSpec:
return path.Join(append(repoPrefix, v.name, "_manifests", "tags")...), nil
case manifestTagPathSpec:
@ -325,26 +293,6 @@ type manifestRevisionLinkPathSpec struct {
func (manifestRevisionLinkPathSpec) pathSpec() {}
// manifestSignaturesPathSpec describes the path components for the directory
// containing all the signatures for the target blob. Entries are named with
// the underlying key id.
type manifestSignaturesPathSpec struct {
name string
revision digest.Digest
}
func (manifestSignaturesPathSpec) pathSpec() {}
// manifestSignatureLinkPathSpec describes the path components used to look up
// a signature file by the hash of its blob.
type manifestSignatureLinkPathSpec struct {
name string
revision digest.Digest
signature digest.Digest
}
func (manifestSignatureLinkPathSpec) pathSpec() {}
// manifestTagsPathSpec describes the path elements required to point to the
// manifest tags directory.
type manifestTagsPathSpec struct {

View file

@ -26,21 +26,6 @@ func TestPathMapper(t *testing.T) {
},
expected: "/docker/registry/v2/repositories/foo/bar/_manifests/revisions/sha256/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/link",
},
{
spec: manifestSignatureLinkPathSpec{
name: "foo/bar",
revision: "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
signature: "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
},
expected: "/docker/registry/v2/repositories/foo/bar/_manifests/revisions/sha256/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/signatures/sha256/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/link",
},
{
spec: manifestSignaturesPathSpec{
name: "foo/bar",
revision: "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
},
expected: "/docker/registry/v2/repositories/foo/bar/_manifests/revisions/sha256/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/signatures",
},
{
spec: manifestTagsPathSpec{
name: "foo/bar",
@ -113,7 +98,7 @@ func TestPathMapper(t *testing.T) {
// Add a few test cases to ensure we cover some errors
// Specify a path that requires a revision and get a digest validation error.
badpath, err := pathFor(manifestSignaturesPathSpec{
badpath, err := pathFor(manifestRevisionPathSpec{
name: "foo/bar",
})

View file

@ -18,7 +18,6 @@ type registry struct {
blobDescriptorCacheProvider cache.BlobDescriptorCacheProvider
deleteEnabled bool
resumableDigestEnabled bool
schema1SignaturesEnabled bool
schema1SigningKey libtrust.PrivateKey
blobDescriptorServiceFactory distribution.BlobDescriptorServiceFactory
}
@ -47,17 +46,8 @@ func DisableDigestResumption(registry *registry) error {
return nil
}
// DisableSchema1Signatures is a functional option for NewRegistry. It disables
// signature storage and ensures all schema1 manifests will only be returned
// with a signature from a provided signing key.
func DisableSchema1Signatures(registry *registry) error {
registry.schema1SignaturesEnabled = false
return nil
}
// Schema1SigningKey returns a functional option for NewRegistry. It sets the
// signing key for adding a signature to all schema1 manifests. This should be
// used in conjunction with disabling signature store.
// key for signing all schema1 manifests.
func Schema1SigningKey(key libtrust.PrivateKey) RegistryOption {
return func(registry *registry) error {
registry.schema1SigningKey = key
@ -116,9 +106,8 @@ func NewRegistry(ctx context.Context, driver storagedriver.StorageDriver, option
statter: statter,
pathFn: bs.path,
},
statter: statter,
resumableDigestEnabled: true,
schema1SignaturesEnabled: true,
statter: statter,
resumableDigestEnabled: true,
}
for _, option := range options {
@ -231,11 +220,6 @@ func (repo *repository) Manifests(ctx context.Context, options ...distribution.M
ctx: ctx,
repository: repo,
blobStore: blobStore,
signatures: &signatureStore{
ctx: ctx,
repository: repo,
blobStore: repo.blobStore,
},
},
schema2Handler: &schema2ManifestHandler{
ctx: ctx,

View file

@ -1,131 +0,0 @@
package storage
import (
"path"
"sync"
"github.com/docker/distribution/context"
"github.com/docker/distribution/digest"
)
type signatureStore struct {
repository *repository
blobStore *blobStore
ctx context.Context
}
func (s *signatureStore) Get(dgst digest.Digest) ([][]byte, error) {
signaturesPath, err := pathFor(manifestSignaturesPathSpec{
name: s.repository.Named().Name(),
revision: dgst,
})
if err != nil {
return nil, err
}
// Need to append signature digest algorithm to path to get all items.
// Perhaps, this should be in the pathMapper but it feels awkward. This
// can be eliminated by implementing listAll on drivers.
signaturesPath = path.Join(signaturesPath, "sha256")
signaturePaths, err := s.blobStore.driver.List(s.ctx, signaturesPath)
if err != nil {
return nil, err
}
var wg sync.WaitGroup
type result struct {
index int
signature []byte
err error
}
ch := make(chan result)
bs := s.linkedBlobStore(s.ctx, dgst)
for i, sigPath := range signaturePaths {
sigdgst, err := digest.ParseDigest("sha256:" + path.Base(sigPath))
if err != nil {
context.GetLogger(s.ctx).Errorf("could not get digest from path: %q, skipping", sigPath)
continue
}
wg.Add(1)
go func(idx int, sigdgst digest.Digest) {
defer wg.Done()
context.GetLogger(s.ctx).
Debugf("fetching signature %q", sigdgst)
r := result{index: idx}
if p, err := bs.Get(s.ctx, sigdgst); err != nil {
context.GetLogger(s.ctx).
Errorf("error fetching signature %q: %v", sigdgst, err)
r.err = err
} else {
r.signature = p
}
ch <- r
}(i, sigdgst)
}
done := make(chan struct{})
go func() {
wg.Wait()
close(done)
}()
// aggregrate the results
signatures := make([][]byte, len(signaturePaths))
loop:
for {
select {
case result := <-ch:
signatures[result.index] = result.signature
if result.err != nil && err == nil {
// only set the first one.
err = result.err
}
case <-done:
break loop
}
}
return signatures, err
}
func (s *signatureStore) Put(dgst digest.Digest, signatures ...[]byte) error {
bs := s.linkedBlobStore(s.ctx, dgst)
for _, signature := range signatures {
if _, err := bs.Put(s.ctx, "application/json", signature); err != nil {
return err
}
}
return nil
}
// linkedBlobStore returns the namedBlobStore of the signatures for the
// manifest with the given digest. Effectively, each signature link path
// layout is a unique linked blob store.
func (s *signatureStore) linkedBlobStore(ctx context.Context, revision digest.Digest) *linkedBlobStore {
linkpath := func(name string, dgst digest.Digest) (string, error) {
return pathFor(manifestSignatureLinkPathSpec{
name: name,
revision: revision,
signature: dgst,
})
}
return &linkedBlobStore{
ctx: ctx,
repository: s.repository,
blobStore: s.blobStore,
blobAccessController: &linkedBlobStatter{
blobStore: s.blobStore,
repository: s.repository,
linkPathFns: []linkPathFunc{linkpath},
},
linkPathFns: []linkPathFunc{linkpath},
}
}

View file

@ -18,7 +18,6 @@ type signedManifestHandler struct {
repository *repository
blobStore *linkedBlobStore
ctx context.Context
signatures *signatureStore
}
var _ ManifestHandler = &signedManifestHandler{}
@ -30,13 +29,6 @@ func (ms *signedManifestHandler) Unmarshal(ctx context.Context, dgst digest.Dige
signatures [][]byte
err error
)
if ms.repository.schema1SignaturesEnabled {
// Fetch the signatures for the manifest
signatures, err = ms.signatures.Get(dgst)
if err != nil {
return nil, err
}
}
jsig, err := libtrust.NewJSONSignature(content, signatures...)
if err != nil {
@ -47,8 +39,6 @@ func (ms *signedManifestHandler) Unmarshal(ctx context.Context, dgst digest.Dige
if err := jsig.Sign(ms.repository.schema1SigningKey); err != nil {
return nil, err
}
} else if !ms.repository.schema1SignaturesEnabled {
return nil, fmt.Errorf("missing signing key with signature store disabled")
}
// Extract the pretty JWS
@ -90,18 +80,6 @@ func (ms *signedManifestHandler) Put(ctx context.Context, manifest distribution.
return "", err
}
if ms.repository.schema1SignaturesEnabled {
// Grab each json signature and store them.
signatures, err := sm.Signatures()
if err != nil {
return "", err
}
if err := ms.signatures.Put(revision.Digest, signatures...); err != nil {
return "", err
}
}
return revision.Digest, nil
}