cli: Pin image to digest using content trust

Implement notary-based digest lookup in the client when
DOCKER_CONTENT_TRUST=1.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

command/service/create.go

@@ -72,6 +72,10 @@ func runCreate(dockerCli *command.DockerCli, opts *serviceOptions) error {
 
 	ctx := context.Background()
 
+	if err := resolveServiceImageDigest(dockerCli, &service); err != nil {
+		return err
+	}
+
 	// only send auth if flag was set
 	if opts.registryAuth {
 		// Retrieve encoded auth token from the image reference

command/service/trust.go

@@ -0,0 +1,96 @@
+package service
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/docker/distribution/digest"
+	distreference "github.com/docker/distribution/reference"
+	"github.com/docker/docker/api/types/swarm"
+	"github.com/docker/docker/cli/command"
+	"github.com/docker/docker/cli/trust"
+	"github.com/docker/docker/reference"
+	"github.com/docker/docker/registry"
+	"github.com/docker/notary/tuf/data"
+	"github.com/pkg/errors"
+	"golang.org/x/net/context"
+)
+
+func resolveServiceImageDigest(dockerCli *command.DockerCli, service *swarm.ServiceSpec) error {
+	if !command.IsTrusted() {
+		// Digests are resolved by the daemon when not using content
+		// trust.
+		return nil
+	}
+
+	image := service.TaskTemplate.ContainerSpec.Image
+
+	// We only attempt to resolve the digest if the reference
+	// could be parsed as a digest reference. Specifying an image ID
+	// is valid but not resolvable. There is no warning message for
+	// an image ID because it's valid to use one.
+	if _, err := digest.ParseDigest(image); err == nil {
+		return nil
+	}
+
+	ref, err := reference.ParseNamed(image)
+	if err != nil {
+		return fmt.Errorf("Could not parse image reference %s", service.TaskTemplate.ContainerSpec.Image)
+	}
+	if _, ok := ref.(reference.Canonical); !ok {
+		ref = reference.WithDefaultTag(ref)
+
+		taggedRef, ok := ref.(reference.NamedTagged)
+		if !ok {
+			// This should never happen because a reference either
+			// has a digest, or WithDefaultTag would give it a tag.
+			return errors.New("Failed to resolve image digest using content trust: reference is missing a tag")
+		}
+
+		resolvedImage, err := trustedResolveDigest(context.Background(), dockerCli, taggedRef)
+		if err != nil {
+			return fmt.Errorf("Failed to resolve image digest using content trust: %v", err)
+		}
+		logrus.Debugf("resolved image tag to %s using content trust", resolvedImage.String())
+		service.TaskTemplate.ContainerSpec.Image = resolvedImage.String()
+	}
+	return nil
+}
+
+func trustedResolveDigest(ctx context.Context, cli *command.DockerCli, ref reference.NamedTagged) (distreference.Canonical, error) {
+	repoInfo, err := registry.ParseRepositoryInfo(ref)
+	if err != nil {
+		return nil, err
+	}
+
+	authConfig := command.ResolveAuthConfig(ctx, cli, repoInfo.Index)
+
+	notaryRepo, err := trust.GetNotaryRepository(cli, repoInfo, authConfig, "pull")
+	if err != nil {
+		return nil, errors.Wrap(err, "error establishing connection to trust repository")
+	}
+
+	t, err := notaryRepo.GetTargetByName(ref.Tag(), trust.ReleasesRole, data.CanonicalTargetsRole)
+	if err != nil {
+		return nil, trust.NotaryError(repoInfo.FullName(), err)
+	}
+	// Only get the tag if it's in the top level targets role or the releases delegation role
+	// ignore it if it's in any other delegation roles
+	if t.Role != trust.ReleasesRole && t.Role != data.CanonicalTargetsRole {
+		return nil, trust.NotaryError(repoInfo.FullName(), fmt.Errorf("No trust data for %s", ref.String()))
+	}
+
+	logrus.Debugf("retrieving target for %s role\n", t.Role)
+	h, ok := t.Hashes["sha256"]
+	if !ok {
+		return nil, errors.New("no valid hash, expecting sha256")
+	}
+
+	dgst := digest.NewDigestFromHex("sha256", hex.EncodeToString(h))
+
+	// Using distribution reference package to make sure that adding a
+	// digest does not erase the tag. When the two reference packages
+	// are unified, this will no longer be an issue.
+	return distreference.WithDigest(ref, dgst)
+}

command/service/update.go

@@ -103,6 +103,12 @@ func runUpdate(dockerCli *command.DockerCli, flags *pflag.FlagSet, serviceID str
 		return err
 	}
 
+	if flags.Changed("image") {
+		if err := resolveServiceImageDigest(dockerCli, spec); err != nil {
+			return err
+		}
+	}
+
 	updatedSecrets, err := getUpdatedSecrets(apiClient, flags, spec.TaskTemplate.ContainerSpec.Secrets)
 	if err != nil {
 		return err