Make referrers attestations OCI compliant (#80)

* Single attestation when creating VSA

* Create single layer images for referrers attestations

* Move mock to test package. Add artifacts test

* Add test for envelope detection

* Add tests for image/index saving

* Add mirror tests

* Remove AttestationImage field from AttestationManifest

* Update naming. strictReferers != laxReferrers

* Add specific test for SaveReferrers

internal/test/mocks.go

@@ -0,0 +1,64 @@
+package test
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+
+	"github.com/docker/attest/pkg/attestation"
+	"github.com/docker/attest/pkg/oci"
+	"github.com/docker/attest/pkg/signerverifier"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/secure-systems-lab/go-securesystemslib/dsse"
+)
+
+type MockResolver struct {
+	Envs []*attestation.Envelope
+}
+
+func (r MockResolver) Attestations(ctx context.Context, mediaType string) ([]*attestation.Envelope, error) {
+	return r.Envs, nil
+}
+
+func (r MockResolver) ImageName(ctx context.Context) (string, error) {
+	return "library/alpine:latest", nil
+}
+
+func (r MockResolver) ImageDescriptor(ctx context.Context) (*v1.Descriptor, error) {
+	digest, err := v1.NewHash("sha256:da8b190665956ea07890a0273e2a9c96bfe291662f08e2860e868eef69c34620")
+	if err != nil {
+		return nil, err
+	}
+	return &v1.Descriptor{
+		Digest:    digest,
+		Size:      1234,
+		MediaType: "application/vnd.oci.image.manifest.v1+json",
+	}, nil
+
+}
+
+func (r MockResolver) ImagePlatform(ctx context.Context) (*v1.Platform, error) {
+	return oci.ParsePlatform("linux/amd64")
+}
+
+type MockRegistryResolver struct {
+	Subject      *v1.Descriptor
+	ImageNameStr string
+	*MockResolver
+}
+
+func (r *MockRegistryResolver) ImageDescriptor(ctx context.Context) (*v1.Descriptor, error) {
+	return r.Subject, nil
+}
+
+func (r *MockRegistryResolver) ImageName(ctx context.Context) (string, error) {
+	return r.ImageNameStr, nil
+}
+
+func GetMockSigner(ctx context.Context) (dsse.SignerVerifier, error) {
+	priv, err := os.ReadFile(filepath.Join("..", "..", "test", "testdata", "test-signing-key.pem"))
+	if err != nil {
+		return nil, err
+	}
+	return signerverifier.LoadKeyPair(priv)
+}

internal/test/test.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 
@@ -82,14 +81,6 @@ func Setup(t *testing.T) (context.Context, dsse.SignerVerifier) {
 	return ctx, signer
 }
 
-func GetMockSigner(ctx context.Context) (dsse.SignerVerifier, error) {
-	priv, err := os.ReadFile(filepath.Join("..", "..", "test", "testdata", "test-signing-key.pem"))
-	if err != nil {
-		return nil, err
-	}
-	return signerverifier.LoadKeyPair(priv)
-}
-
 type AnnotatedStatement struct {
 	OCIDescriptor   *v1.Descriptor
 	InTotoStatement *intoto.Statement