attestations: replace intoto media type with vendored const

We were using a mixture of own custom const and the vendored const. For
consistency, we should use only the vendored const everywhere.

Signed-off-by: Justin Chadwell <me@jedevc.com>

exporter/containerimage/writer.go

@@ -437,7 +437,7 @@ func (ic *ImageWriter) commitAttestationsManifest(ctx context.Context, opts *Ima
 		}
 		digest := digest.FromBytes(data)
 		desc := ocispecs.Descriptor{
-			MediaType: attestationTypes.MediaTypeDockerSchema2AttestationType,
+			MediaType: intoto.PayloadType,
 			Digest:    digest,
 			Size:      int64(len(data)),
 			Annotations: map[string]string{

solver/llbsolver/solver.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 	"time"
 
+	intoto "github.com/in-toto/in-toto-golang/in_toto"
 	slsa02 "github.com/in-toto/in-toto-golang/in_toto/slsa_provenance/v0.2"
 	controlapi "github.com/moby/buildkit/api/services/control"
 	"github.com/moby/buildkit/cache"
@@ -26,7 +27,6 @@ import (
 	"github.com/moby/buildkit/solver/llbsolver/provenance"
 	"github.com/moby/buildkit/solver/result"
 	spb "github.com/moby/buildkit/sourcepolicy/pb"
-	"github.com/moby/buildkit/util/attestation"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/compression"
 	"github.com/moby/buildkit/util/entitlements"
@@ -210,7 +210,7 @@ func (s *Solver) recordBuildHistory(ctx context.Context, id string, req frontend
 			if err != nil {
 				return nil, nil, err
 			}
-			w, err := s.history.OpenBlobWriter(ctx, attestation.MediaTypeDockerSchema2AttestationType)
+			w, err := s.history.OpenBlobWriter(ctx, intoto.PayloadType)
 			if err != nil {
 				return nil, nil, err
 			}

util/attestation/types.go

@@ -1,8 +1,6 @@
 package attestation
 
 const (
-	MediaTypeDockerSchema2AttestationType = "application/vnd.in-toto+json"
-
 	DockerAnnotationReferenceType        = "vnd.docker.reference.type"
 	DockerAnnotationReferenceDigest      = "vnd.docker.reference.digest"
 	DockerAnnotationReferenceDescription = "vnd.docker.reference.description"

util/imageutil/config.go

@@ -13,7 +13,7 @@ import (
 	"github.com/containerd/containerd/reference"
 	"github.com/containerd/containerd/remotes"
 	"github.com/containerd/containerd/remotes/docker"
-	"github.com/moby/buildkit/util/attestation"
+	intoto "github.com/in-toto/in-toto-golang/in_toto"
 	"github.com/moby/buildkit/util/contentutil"
 	"github.com/moby/buildkit/util/leaseutil"
 	"github.com/moby/buildkit/util/resolver/limited"
@@ -174,7 +174,7 @@ func childrenConfigHandler(provider content.Provider, platform platforms.MatchCo
 				descs = append(descs, index.Manifests...)
 			}
 		case images.MediaTypeDockerSchema2Config, ocispecs.MediaTypeImageConfig, docker.LegacyConfigMediaType,
-			attestation.MediaTypeDockerSchema2AttestationType:
+			intoto.PayloadType:
 			// childless data types.
 			return nil, nil
 		default:

util/push/push.go

@@ -15,7 +15,6 @@ import (
 	"github.com/containerd/containerd/remotes/docker"
 	"github.com/docker/distribution/reference"
 	"github.com/moby/buildkit/session"
-	"github.com/moby/buildkit/util/attestation"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/flightcontrol"
 	"github.com/moby/buildkit/util/imageutil"
@@ -250,7 +249,7 @@ func childrenHandler(provider content.Provider) images.HandlerFunc {
 		case images.MediaTypeDockerSchema2Layer, images.MediaTypeDockerSchema2LayerGzip,
 			images.MediaTypeDockerSchema2Config, ocispecs.MediaTypeImageConfig,
 			ocispecs.MediaTypeImageLayer, ocispecs.MediaTypeImageLayerGzip,
-			attestation.MediaTypeDockerSchema2AttestationType:
+			intoto.PayloadType:
 			// childless data types.
 			return nil, nil
 		default: