Add verification of image manifest digests

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

graph/manifest.go

@@ -6,8 +6,10 @@ import (
 	"fmt"
 
 	log "github.com/Sirupsen/logrus"
+	"github.com/docker/distribution/digest"
 	"github.com/docker/docker/engine"
 	"github.com/docker/docker/registry"
+	"github.com/docker/docker/utils"
 	"github.com/docker/libtrust"
 )
 
@@ -16,7 +18,7 @@ import (
 // contains no signatures by a trusted key for the name in the manifest, the
 // image is not considered verified. The parsed manifest object and a boolean
 // for whether the manifest is verified is returned.
-func (s *TagStore) loadManifest(eng *engine.Engine, manifestBytes []byte) (*registry.ManifestData, bool, error) {
+func (s *TagStore) loadManifest(eng *engine.Engine, manifestBytes []byte, dgst, ref string) (*registry.ManifestData, bool, error) {
 	sig, err := libtrust.ParsePrettySignature(manifestBytes, "signatures")
 	if err != nil {
 		return nil, false, fmt.Errorf("error parsing payload: %s", err)
@@ -32,6 +34,31 @@ func (s *TagStore) loadManifest(eng *engine.Engine, manifestBytes []byte) (*regi
 		return nil, false, fmt.Errorf("error retrieving payload: %s", err)
 	}
 
+	var manifestDigest digest.Digest
+
+	if dgst != "" {
+		manifestDigest, err = digest.ParseDigest(dgst)
+		if err != nil {
+			return nil, false, fmt.Errorf("invalid manifest digest from registry: %s", err)
+		}
+
+		dgstVerifier, err := digest.NewDigestVerifier(manifestDigest)
+		if err != nil {
+			return nil, false, fmt.Errorf("unable to verify manifest digest from registry: %s", err)
+		}
+
+		dgstVerifier.Write(payload)
+
+		if !dgstVerifier.Verified() {
+			computedDigest, _ := digest.FromBytes(payload)
+			return nil, false, fmt.Errorf("unable to verify manifest digest: registry has %q, computed %q", manifestDigest, computedDigest)
+		}
+	}
+
+	if utils.DigestReference(ref) && ref != manifestDigest.String() {
+		return nil, false, fmt.Errorf("mismatching image manifest digest: got %q, expected %q", manifestDigest, ref)
+	}
+
 	var manifest registry.ManifestData
 	if err := json.Unmarshal(payload, &manifest); err != nil {
 		return nil, false, fmt.Errorf("error unmarshalling manifest: %s", err)

graph/pull.go

@@ -430,12 +430,15 @@ func (s *TagStore) pullV2Repository(eng *engine.Engine, r *registry.Session, out
 
 func (s *TagStore) pullV2Tag(eng *engine.Engine, r *registry.Session, out io.Writer, endpoint *registry.Endpoint, repoInfo *registry.RepositoryInfo, tag string, sf *utils.StreamFormatter, parallel bool, auth *registry.RequestAuthorization) (bool, error) {
 	log.Debugf("Pulling tag from V2 registry: %q", tag)
+
 	manifestBytes, manifestDigest, err := r.GetV2ImageManifest(endpoint, repoInfo.RemoteName, tag, auth)
 	if err != nil {
 		return false, err
 	}
 
-	manifest, verified, err := s.loadManifest(eng, manifestBytes)
+	// loadManifest ensures that the manifest payload has the expected digest
+	// if the tag is a digest reference.
+	manifest, verified, err := s.loadManifest(eng, manifestBytes, manifestDigest, tag)
 	if err != nil {
 		return false, fmt.Errorf("error verifying manifest: %s", err)
 	}
@@ -605,7 +608,7 @@ func (s *TagStore) pullV2Tag(eng *engine.Engine, r *registry.Session, out io.Wri
 		out.Write(sf.FormatStatus(utils.ImageReference(repoInfo.CanonicalName, tag), "The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security."))
 	}
 
-	if len(manifestDigest) > 0 {
+	if manifestDigest != "" {
 		out.Write(sf.FormatStatus("", "Digest: %s", manifestDigest))
 	}
 

graph/push.go

@@ -1,7 +1,6 @@
 package graph
 
 import (
-	"bytes"
 	"crypto/sha256"
 	"encoding/json"
 	"errors"
@@ -432,14 +431,12 @@ func (s *TagStore) pushV2Repository(r *registry.Session, localRepo Repository, o
 		log.Infof("Signed manifest for %s:%s using daemon's key: %s", repoInfo.LocalName, tag, s.trustKey.KeyID())
 
 		// push the manifest
-		digest, err := r.PutV2ImageManifest(endpoint, repoInfo.RemoteName, tag, bytes.NewReader(signedBody), auth)
+		digest, err := r.PutV2ImageManifest(endpoint, repoInfo.RemoteName, tag, signedBody, mBytes, auth)
 		if err != nil {
 			return err
 		}
 
-		if len(digest) > 0 {
-			out.Write(sf.FormatStatus("", "Digest: %s", digest))
-		}
+		out.Write(sf.FormatStatus("", "Digest: %s", digest))
 	}
 	return nil
 }