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"
@@ -432,15 +431,13 @@ 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))
 	}
-	}
 	return nil
 }
 

registry/session_v2.go

@@ -1,6 +1,7 @@
 package registry
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -8,6 +9,7 @@ import (
 	"strconv"
 
 	log "github.com/Sirupsen/logrus"
+	"github.com/docker/distribution/digest"
 	"github.com/docker/docker/registry/v2"
 	"github.com/docker/docker/utils"
 )
@@ -95,11 +97,12 @@ func (r *Session) GetV2ImageManifest(ep *Endpoint, imageName, tagName string, au
 		return nil, "", utils.NewHTTPRequestError(fmt.Sprintf("Server error: %d trying to fetch for %s:%s", res.StatusCode, imageName, tagName), res)
 	}
 
-	buf, err := ioutil.ReadAll(res.Body)
+	manifestBytes, err := ioutil.ReadAll(res.Body)
 	if err != nil {
 		return nil, "", fmt.Errorf("Error while reading the http response: %s", err)
 	}
-	return buf, res.Header.Get(DockerDigestHeader), nil
+
+	return manifestBytes, res.Header.Get(DockerDigestHeader), nil
 }
 
 // - Succeeded to head image blob (already exists)
@@ -263,7 +266,7 @@ func (r *Session) PutV2ImageBlob(ep *Endpoint, imageName, sumType, sumStr string
 }
 
 // Finally Push the (signed) manifest of the blobs we've just pushed
-func (r *Session) PutV2ImageManifest(ep *Endpoint, imageName, tagName string, manifestRdr io.Reader, auth *RequestAuthorization) (string, error) {
+func (r *Session) PutV2ImageManifest(ep *Endpoint, imageName, tagName string, signedManifest, rawManifest []byte, auth *RequestAuthorization) (digest.Digest, error) {
 	routeURL, err := getV2Builder(ep).BuildManifestURL(imageName, tagName)
 	if err != nil {
 		return "", err
@@ -271,7 +274,7 @@ func (r *Session) PutV2ImageManifest(ep *Endpoint, imageName, tagName string, ma
 
 	method := "PUT"
 	log.Debugf("[registry] Calling %q %s", method, routeURL)
-	req, err := r.reqFactory.NewRequest(method, routeURL, manifestRdr)
+	req, err := r.reqFactory.NewRequest(method, routeURL, bytes.NewReader(signedManifest))
 	if err != nil {
 		return "", err
 	}
@@ -297,7 +300,24 @@ func (r *Session) PutV2ImageManifest(ep *Endpoint, imageName, tagName string, ma
 		return "", utils.NewHTTPRequestError(fmt.Sprintf("Server error: %d trying to push %s:%s manifest", res.StatusCode, imageName, tagName), res)
 	}
 
-	return res.Header.Get(DockerDigestHeader), nil
+	hdrDigest, err := digest.ParseDigest(res.Header.Get(DockerDigestHeader))
+	if err != nil {
+		return "", fmt.Errorf("invalid manifest digest from registry: %s", err)
+	}
+
+	dgstVerifier, err := digest.NewDigestVerifier(hdrDigest)
+	if err != nil {
+		return "", fmt.Errorf("invalid manifest digest from registry: %s", err)
+	}
+
+	dgstVerifier.Write(rawManifest)
+
+	if !dgstVerifier.Verified() {
+		computedDigest, _ := digest.FromBytes(rawManifest)
+		return "", fmt.Errorf("unable to verify manifest digest: registry has %q, computed %q", hdrDigest, computedDigest)
+	}
+
+	return hdrDigest, nil
 }
 
 type remoteTags struct {