feat: add attest sign/verify

pkg/oci/types.go

@@ -1,8 +1,69 @@
 package oci
 
+import (
+	"fmt"
+	"log"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/layout"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+)
+
 const (
 	DockerReferenceType     = "vnd.docker.reference.type"
 	DockerReferenceDigest   = "vnd.docker.reference.digest"
 	AttestationManifestType = "attestation-manifest"
 	InTotoPredicateType     = "in-toto.io/predicate-type"
+	OciReferenceTarget      = "org.opencontainers.image.ref.name"
 )
+
+type AttestationIndex struct {
+	Index v1.ImageIndex
+	Name  string
+}
+
+func AttestationIndexFromPath(path string) (*AttestationIndex, error) {
+	wrapperIdx, err := layout.ImageIndexFromPath(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to load image index: %w", err)
+	}
+
+	idxm, err := wrapperIdx.IndexManifest()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get digest: %w", err)
+	}
+	imageName := idxm.Manifests[0].Annotations[OciReferenceTarget]
+	idxDigest := idxm.Manifests[0].Digest
+
+	idx, err := wrapperIdx.ImageIndex(idxDigest)
+	if err != nil {
+		return nil, fmt.Errorf("failed to extract ImageIndex for digest %s: %w", idxDigest.String(), err)
+	}
+	return &AttestationIndex{
+		Index: idx,
+		Name:  imageName,
+	}, nil
+}
+
+func AttestationIndexFromRemote(image string) (*AttestationIndex, error) {
+	ref, err := name.ParseReference(image)
+	if err != nil {
+		log.Fatalf("Failed to parse image name: %v", err)
+	}
+	// Get the authenticator from the default Docker keychain
+	auth, err := authn.DefaultKeychain.Resolve(ref.Context())
+	if err != nil {
+		log.Fatalf("Failed to get authenticator: %v", err)
+	}
+	// Pull the image from the registry
+	idx, err := remote.Index(ref, remote.WithAuth(auth))
+	if err != nil {
+		return nil, fmt.Errorf("failed to pull image %s: %w", image, err)
+	}
+	return &AttestationIndex{
+		Index: idx,
+		Name:  image,
+	}, nil
+}