artifacts: initial support for artifacts/notaryv2 spec

https://github.com/oras-project/artifacts-spec
https://github.com/notaryproject/notaryproject

Fixes issue #264

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>

.github/workflows/ci-cd.yml

@@ -11,7 +11,7 @@ on:
 name: build-test
 jobs:
   build-test:
-    name: Build and test ZOT
+    name: Build and test zot
     runs-on: ubuntu-latest
     services:
       s3mock:
@@ -39,6 +39,9 @@ jobs:
           sudo apt-get install rpm
           sudo apt install snapd
           sudo snap install skopeo --edge --devmode
+          curl -Lo notation.tar.gz https://github.com/notaryproject/notation/releases/download/v0.7.1-alpha.1/notation_0.7.1-alpha.1_linux_amd64.tar.gz
+          sudo tar xvzf notation.tar.gz -C /usr/bin notation
+          go get github.com/wadey/gocovmerge
 
       - name: Run build and test
         timeout-minutes: 30

README.md

@@ -18,6 +18,7 @@ https://anuvu.github.io/zot/
   * ```make binary``` builds a zot with all extensions enabled 
 * Uses [OCI image layout](https://github.com/opencontainers/image-spec/blob/master/image-layout.md) for image storage
   * Can serve any OCI image layout as a registry 
+* Supports container image signatures - [cosign](https://github.com/sigstore/cosign) and [notation](https://github.com/notaryproject/notation)
 * Supports [helm charts](https://helm.sh/docs/topics/registries/)
 * Behavior controlled via [configuration](./examples/README.md)
 * Supports image deletion by tag

errors/errors.go

@@ -44,4 +44,5 @@ var (
 	ErrEmptyRepoList           = errors.New("search: no repository found")
 	ErrInvalidRepositoryName   = errors.New("routes: not a repository name")
 	ErrSyncMissingCatalog      = errors.New("sync: couldn't fetch upstream registry's catalog")
+	ErrMethodNotSupported      = errors.New("storage: method not supported")
 )

go.mod

@@ -28,15 +28,19 @@ require (
 	github.com/json-iterator/go v1.1.12
 	github.com/mitchellh/mapstructure v1.4.2
 	github.com/nmcclain/ldap v0.0.0-20210720162743-7f8d1e44eeba
+	github.com/notaryproject/notation v0.7.0-alpha.1
+	github.com/notaryproject/notation-go-lib v1.0.0-alpha-1
 	github.com/olekukonko/tablewriter v0.0.5
 	github.com/opencontainers/distribution-spec/specs-go v0.0.0-20211026153258-b3f631f25f1a
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.0.2-0.20211117181255-693428a734f5
 	github.com/opencontainers/umoci v0.4.8-0.20210922062158-e60a0cc726e6
+	github.com/oras-project/artifacts-spec v1.0.0-draft.1
 	github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
 	github.com/prometheus/client_golang v1.11.0
 	github.com/prometheus/client_model v0.2.0
 	github.com/rs/zerolog v1.26.0
+	github.com/sigstore/cosign v1.3.1
 	github.com/smartystreets/goconvey v1.7.2
 	github.com/spf13/cobra v1.2.1
 	github.com/spf13/viper v1.9.0

pkg/api/controller_test.go

@@ -1,3 +1,4 @@
+//go:build extended
 // +build extended
 
 package api_test
@@ -16,6 +17,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"os/exec"
 	"path"
 	"regexp"
 	"strings"
@@ -30,8 +32,14 @@ import (
 	"github.com/chartmuseum/auth"
 	"github.com/mitchellh/mapstructure"
 	vldap "github.com/nmcclain/ldap"
+	notreg "github.com/notaryproject/notation/pkg/registry"
 	godigest "github.com/opencontainers/go-digest"
 	ispec "github.com/opencontainers/image-spec/specs-go/v1"
+	artifactspec "github.com/oras-project/artifacts-spec/specs-go/v1"
+	"github.com/sigstore/cosign/cmd/cosign/cli/generate"
+	"github.com/sigstore/cosign/cmd/cosign/cli/options"
+	"github.com/sigstore/cosign/cmd/cosign/cli/sign"
+	"github.com/sigstore/cosign/cmd/cosign/cli/verify"
 	. "github.com/smartystreets/goconvey/convey"
 	"github.com/stretchr/testify/assert"
 	"golang.org/x/crypto/bcrypt"
@@ -2775,6 +2783,318 @@ func TestHardLink(t *testing.T) {
 	})
 }
 
+func TestImageSignatures(t *testing.T) {
+	Convey("Validate signatures", t, func() {
+		// start a new server
+		port := GetFreePort()
+		baseURL := GetBaseURL(port)
+
+		conf := config.New()
+		conf.HTTP.Port = port
+
+		c := api.NewController(conf)
+		dir, err := ioutil.TempDir("", "oci-repo-test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(dir)
+		c.Config.Storage.RootDirectory = dir
+		go func(controller *api.Controller) {
+			// this blocks
+			if err := controller.Run(); err != nil {
+				return
+			}
+		}(c)
+		// wait till ready
+		for {
+			_, err := resty.R().Get(baseURL)
+			if err == nil {
+				break
+			}
+			time.Sleep(100 * time.Millisecond)
+		}
+		defer func(controller *api.Controller) {
+			ctx := context.Background()
+			_ = controller.Server.Shutdown(ctx)
+		}(c)
+
+		repoName := "signed-repo"
+
+		// create a blob/layer
+		resp, err := resty.R().Post(baseURL + fmt.Sprintf("/v2/%s/blobs/uploads/", repoName))
+		So(err, ShouldBeNil)
+		So(resp.StatusCode(), ShouldEqual, 202)
+		loc := Location(baseURL, resp)
+		So(loc, ShouldNotBeEmpty)
+
+		resp, err = resty.R().Get(loc)
+		So(err, ShouldBeNil)
+		So(resp.StatusCode(), ShouldEqual, 204)
+		content := []byte("this is a blob")
+		digest := godigest.FromBytes(content)
+		So(digest, ShouldNotBeNil)
+		// monolithic blob upload: success
+		resp, err = resty.R().SetQueryParam("digest", digest.String()).
+			SetHeader("Content-Type", "application/octet-stream").SetBody(content).Put(loc)
+		So(err, ShouldBeNil)
+		So(resp.StatusCode(), ShouldEqual, 201)
+		blobLoc := resp.Header().Get("Location")
+		So(blobLoc, ShouldNotBeEmpty)
+		So(resp.Header().Get("Content-Length"), ShouldEqual, "0")
+		So(resp.Header().Get(api.DistContentDigestKey), ShouldNotBeEmpty)
+
+		// create a manifest
+		m := ispec.Manifest{
+			Config: ispec.Descriptor{
+				Digest: digest,
+				Size:   int64(len(content)),
+			},
+			Layers: []ispec.Descriptor{
+				{
+					MediaType: "application/vnd.oci.image.layer.v1.tar",
+					Digest:    digest,
+					Size:      int64(len(content)),
+				},
+			},
+		}
+		m.SchemaVersion = 2
+		content, err = json.Marshal(m)
+		So(err, ShouldBeNil)
+		digest = godigest.FromBytes(content)
+		So(digest, ShouldNotBeNil)
+		resp, err = resty.R().SetHeader("Content-Type", "application/vnd.oci.image.manifest.v1+json").
+			SetBody(content).Put(baseURL + fmt.Sprintf("/v2/%s/manifests/1.0", repoName))
+		So(err, ShouldBeNil)
+		So(resp.StatusCode(), ShouldEqual, 201)
+		d := resp.Header().Get(api.DistContentDigestKey)
+		So(d, ShouldNotBeEmpty)
+		So(d, ShouldEqual, digest.String())
+
+		Convey("Validate cosign signatures", func() {
+			cwd, err := os.Getwd()
+			So(err, ShouldBeNil)
+			defer func() { _ = os.Chdir(cwd) }()
+			tdir, err := ioutil.TempDir("", "cosign")
+			So(err, ShouldBeNil)
+			defer os.RemoveAll(tdir)
+			_ = os.Chdir(tdir)
+
+			// generate a keypair
+			os.Setenv("COSIGN_PASSWORD", "")
+			err = generate.GenerateKeyPairCmd(context.TODO(), "", nil)
+			So(err, ShouldBeNil)
+
+			// sign the image
+			err = sign.SignCmd(context.TODO(),
+				sign.KeyOpts{KeyRef: path.Join(tdir, "cosign.key"), PassFunc: generate.GetPass},
+				options.RegistryOptions{AllowInsecure: true},
+				map[string]interface{}{"tag": "1.0"},
+				[]string{fmt.Sprintf("localhost:%s/%s@%s", port, repoName, digest.String())},
+				"", true, "", false, false, "")
+			So(err, ShouldBeNil)
+
+			// verify the image
+			a := &options.AnnotationOptions{Annotations: []string{"tag=1.0"}}
+			amap, err := a.AnnotationsMap()
+			So(err, ShouldBeNil)
+			v := verify.VerifyCommand{
+				RegistryOptions: options.RegistryOptions{AllowInsecure: true},
+				CheckClaims:     true,
+				KeyRef:          path.Join(tdir, "cosign.pub"),
+				Annotations:     amap,
+			}
+			err = v.Exec(context.TODO(), []string{fmt.Sprintf("localhost:%s/%s:%s", port, repoName, "1.0")})
+			So(err, ShouldBeNil)
+
+			// verify the image with incorrect tag
+			a = &options.AnnotationOptions{Annotations: []string{"tag=2.0"}}
+			amap, err = a.AnnotationsMap()
+			So(err, ShouldBeNil)
+			v = verify.VerifyCommand{
+				RegistryOptions: options.RegistryOptions{AllowInsecure: true},
+				CheckClaims:     true,
+				KeyRef:          path.Join(tdir, "cosign.pub"),
+				Annotations:     amap,
+			}
+			err = v.Exec(context.TODO(), []string{fmt.Sprintf("localhost:%s/%s:%s", port, repoName, "1.0")})
+			So(err, ShouldNotBeNil)
+
+			// verify the image with incorrect key
+			a = &options.AnnotationOptions{Annotations: []string{"tag=1.0"}}
+			amap, err = a.AnnotationsMap()
+			So(err, ShouldBeNil)
+			v = verify.VerifyCommand{
+				CheckClaims:     true,
+				RegistryOptions: options.RegistryOptions{AllowInsecure: true},
+				KeyRef:          path.Join(tdir, "cosign.key"),
+				Annotations:     amap,
+			}
+			err = v.Exec(context.TODO(), []string{fmt.Sprintf("localhost:%s/%s:%s", port, repoName, "1.0")})
+			So(err, ShouldNotBeNil)
+
+			// generate another keypair
+			err = os.Remove(path.Join(tdir, "cosign.pub"))
+			So(err, ShouldBeNil)
+			err = os.Remove(path.Join(tdir, "cosign.key"))
+			So(err, ShouldBeNil)
+
+			os.Setenv("COSIGN_PASSWORD", "")
+			err = generate.GenerateKeyPairCmd(context.TODO(), "", nil)
+			So(err, ShouldBeNil)
+
+			// verify the image with incorrect key
+			a = &options.AnnotationOptions{Annotations: []string{"tag=1.0"}}
+			amap, err = a.AnnotationsMap()
+			So(err, ShouldBeNil)
+			v = verify.VerifyCommand{
+				CheckClaims:     true,
+				RegistryOptions: options.RegistryOptions{AllowInsecure: true},
+				KeyRef:          path.Join(tdir, "cosign.pub"),
+				Annotations:     amap,
+			}
+			err = v.Exec(context.TODO(), []string{fmt.Sprintf("localhost:%s/%s:%s", port, repoName, "1.0")})
+			So(err, ShouldNotBeNil)
+		})
+
+		Convey("Validate notation signatures", func() {
+			cwd, err := os.Getwd()
+			So(err, ShouldBeNil)
+			defer func() { _ = os.Chdir(cwd) }()
+			tdir, err := ioutil.TempDir("", "notation")
+			So(err, ShouldBeNil)
+			defer os.RemoveAll(tdir)
+			_ = os.Chdir(tdir)
+
+			// "notation" (notaryv2) doesn't yet support exported apis, so use the binary instead
+			notPath, err := exec.LookPath("notation")
+			So(notPath, ShouldNotBeNil)
+			So(err, ShouldBeNil)
+
+			os.Setenv("XDG_CONFIG_HOME", tdir)
+
+			// generate a keypair
+			cmd := exec.Command("notation", "cert", "generate-test", "--trust", "good")
+			err = cmd.Run()
+			So(err, ShouldBeNil)
+
+			// generate another keypair
+			cmd = exec.Command("notation", "cert", "generate-test", "--trust", "bad")
+			err = cmd.Run()
+			So(err, ShouldBeNil)
+
+			// sign the image
+			image := fmt.Sprintf("localhost:%s/%s:%s", port, repoName, "1.0")
+			cmd = exec.Command("notation", "sign", "--key", "good", "--plain-http", image)
+			err = cmd.Run()
+			So(err, ShouldBeNil)
+
+			// verify the image
+			cmd = exec.Command("notation", "verify", "--cert", "good", "--plain-http", image)
+			out, err := cmd.CombinedOutput()
+			So(err, ShouldBeNil)
+			msg := string(out)
+			So(msg, ShouldNotBeEmpty)
+			So(strings.Contains(msg, "verification failure"), ShouldBeFalse)
+
+			// verify the image with incorrect key
+			cmd = exec.Command("notation", "verify", "--cert", "bad", "--plain-http", image)
+			out, err = cmd.CombinedOutput()
+			So(err, ShouldNotBeNil)
+			msg = string(out)
+			So(msg, ShouldNotBeEmpty)
+			So(strings.Contains(msg, "verification failure"), ShouldBeTrue)
+
+			// check unsupported manifest media type
+			resp, err = resty.R().SetHeader("Content-Type", "application/vnd.unsupported.image.manifest.v1+json").
+				SetBody(content).Put(baseURL + fmt.Sprintf("/v2/%s/manifests/1.0", repoName))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, 415)
+
+			// check invalid content with artifact media type
+			resp, err = resty.R().SetHeader("Content-Type", artifactspec.MediaTypeArtifactManifest).
+				SetBody([]byte("bogus")).Put(baseURL + fmt.Sprintf("/v2/%s/manifests/1.0", repoName))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, 400)
+
+			Convey("Validate corrupted signature", func() {
+				// verify with corrupted signature
+				resp, err = resty.R().SetQueryParam("artifactType", notreg.ArtifactTypeNotation).Get(
+					fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+				So(err, ShouldBeNil)
+				So(resp.StatusCode(), ShouldEqual, http.StatusOK)
+				var refs api.ReferenceList
+				err = json.Unmarshal(resp.Body(), &refs)
+				So(err, ShouldBeNil)
+				So(len(refs.References), ShouldEqual, 1)
+				err = ioutil.WriteFile(path.Join(dir, repoName, "blobs",
+					strings.ReplaceAll(refs.References[0].Digest.String(), ":", "/")), []byte("corrupt"), 0600)
+				So(err, ShouldBeNil)
+				resp, err = resty.R().SetQueryParam("artifactType", notreg.ArtifactTypeNotation).Get(
+					fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+				So(err, ShouldBeNil)
+				So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+				cmd = exec.Command("notation", "verify", "--cert", "good", "--plain-http", image)
+				out, err = cmd.CombinedOutput()
+				So(err, ShouldNotBeNil)
+				msg = string(out)
+				So(msg, ShouldNotBeEmpty)
+			})
+
+			Convey("Validate deleted signature", func() {
+				// verify with corrupted signature
+				resp, err = resty.R().SetQueryParam("artifactType", notreg.ArtifactTypeNotation).Get(
+					fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+				So(err, ShouldBeNil)
+				So(resp.StatusCode(), ShouldEqual, http.StatusOK)
+				var refs api.ReferenceList
+				err = json.Unmarshal(resp.Body(), &refs)
+				So(err, ShouldBeNil)
+				So(len(refs.References), ShouldEqual, 1)
+				err = os.Remove(path.Join(dir, repoName, "blobs",
+					strings.ReplaceAll(refs.References[0].Digest.String(), ":", "/")))
+				So(err, ShouldBeNil)
+				resp, err = resty.R().SetQueryParam("artifactType", notreg.ArtifactTypeNotation).Get(
+					fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+				So(err, ShouldBeNil)
+				So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+				cmd = exec.Command("notation", "verify", "--cert", "good", "--plain-http", image)
+				out, err = cmd.CombinedOutput()
+				So(err, ShouldNotBeNil)
+				msg = string(out)
+				So(msg, ShouldNotBeEmpty)
+			})
+		})
+
+		Convey("GetReferrers", func() {
+			// cover error paths
+			resp, err := resty.R().Get(
+				fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, "badRepo", "badDigest"))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, http.StatusNotFound)
+
+			resp, err = resty.R().Get(
+				fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, "badDigest"))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+
+			resp, err = resty.R().Get(
+				fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+
+			resp, err = resty.R().SetQueryParam("artifactType", "badArtifact").Get(
+				fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, repoName, digest.String()))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+
+			resp, err = resty.R().SetQueryParam("artifactType", notreg.ArtifactTypeNotation).Get(
+				fmt.Sprintf("%s/oras/artifacts/v1/%s/manifests/%s/referrers", baseURL, "badRepo", digest.String()))
+			So(err, ShouldBeNil)
+			So(resp.StatusCode(), ShouldEqual, http.StatusNotFound)
+		})
+	})
+}
+
 func getAllBlobs(imagePath string) []string {
 	blobList := make([]string, 0)
 

pkg/api/routes.go

@@ -28,6 +28,8 @@ import (
 	_ "github.com/anuvu/zot/swagger" // as required by swaggo
 	"github.com/gorilla/mux"
 	jsoniter "github.com/json-iterator/go"
+	"github.com/notaryproject/notation-go-lib"
+	notreg "github.com/notaryproject/notation/pkg/registry"
 	ispec "github.com/opencontainers/image-spec/specs-go/v1"
 	httpSwagger "github.com/swaggo/http-swagger"
 )
@@ -93,6 +95,11 @@ func (rh *RouteHandler) SetupRoutes() {
 		g.HandleFunc("/",
 			rh.CheckVersionSupport).Methods("GET")
 	}
+
+	// support for oras artifact reference types (alpha 1) - image signature use case
+	rh.c.Router.HandleFunc(fmt.Sprintf("/oras/artifacts/v1/{name:%s}/manifests/{digest}/referrers", NameRegexp.String()),
+		rh.GetReferrers).Methods("GET")
+
 	// swagger swagger "/swagger/v2/index.html"
 	rh.c.Router.PathPrefix("/swagger/v2/").Methods("GET").Handler(httpSwagger.WrapHandler)
 	// Setup Extensions Routes
@@ -393,7 +400,7 @@ func (rh *RouteHandler) UpdateManifest(w http.ResponseWriter, r *http.Request) {
 	}
 
 	mediaType := r.Header.Get("Content-Type")
-	if mediaType != ispec.MediaTypeImageManifest {
+	if !storage.IsSupportedMediaType(mediaType) {
 		w.WriteHeader(http.StatusUnsupportedMediaType)
 		return
 	}
@@ -1290,3 +1297,68 @@ func getImageManifest(rh *RouteHandler, is storage.ImageStore, name,
 
 	return content, digest, mediaType, err
 }
+
+type ReferenceList struct {
+	References []notation.Descriptor `json:"references"`
+}
+
+// GetReferrers godoc
+// @Summary Get references for an image
+// @Description Get references for an image given a digest and artifact type
+// @Accept  json
+// @Produce json
+// @Param   name     path    string     true        "repository name"
+// @Param   digest   path    string     true        "image digest"
+// @Param 	artifactType	 query 	 string 	true	    "artifact type"
+// @Success 200 {string} string "ok"
+// @Failure 404 {string} string "not found"
+// @Failure 500 {string} string "internal server error"
+// @Router /oras/artifacts/v1/{name:%s}/manifests/{digest}/referrers [get].
+func (rh *RouteHandler) GetReferrers(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	name, ok := vars["name"]
+
+	if !ok || name == "" {
+		w.WriteHeader(http.StatusNotFound)
+		return
+	}
+
+	digest, ok := vars["digest"]
+	if !ok || digest == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	artifactTypes, ok := r.URL.Query()["artifactType"]
+	if !ok || len(artifactTypes) != 1 {
+		rh.c.Log.Error().Msg("invalid artifact types")
+		w.WriteHeader(http.StatusBadRequest)
+
+		return
+	}
+
+	artifactType := artifactTypes[0]
+
+	if artifactType != notreg.ArtifactTypeNotation {
+		rh.c.Log.Error().Str("artifactType", artifactType).Msg("invalid artifact type")
+		w.WriteHeader(http.StatusBadRequest)
+
+		return
+	}
+
+	is := rh.getImageStore(name)
+
+	rh.c.Log.Info().Str("digest", digest).Str("artifactType", artifactType).Msg("getting manifest")
+
+	refs, err := is.GetReferrers(name, digest, artifactType)
+	if err != nil {
+		rh.c.Log.Error().Err(err).Str("name", name).Str("digest", digest).Msg("unable to get references")
+		w.WriteHeader(http.StatusBadRequest)
+
+		return
+	}
+
+	rs := ReferenceList{References: refs}
+
+	WriteJSON(w, http.StatusOK, rs)
+}

pkg/storage/s3/s3_test.go

@@ -18,6 +18,7 @@ import (
 
 	"testing"
 
+	zerr "github.com/anuvu/zot/errors"
 	"github.com/anuvu/zot/pkg/extensions/monitoring"
 	"github.com/anuvu/zot/pkg/log"
 	"github.com/anuvu/zot/pkg/storage"
@@ -717,4 +718,16 @@ func TestNegativeCasesObjectsStorage(t *testing.T) {
 		err := il.DeleteBlob(testImage, d.String())
 		So(err, ShouldNotBeNil)
 	})
+
+	Convey("Test GetReferrers", t, func(c C) {
+		il = createMockStorage(testDir, &StorageDriverMock{
+			deleteFn: func(ctx context.Context, path string) error {
+				return errS3
+			},
+		})
+		d := godigest.FromBytes([]byte(""))
+		_, err := il.GetReferrers(testImage, d.String(), "application/image")
+		So(err, ShouldNotBeNil)
+		So(err, ShouldEqual, zerr.ErrMethodNotSupported)
+	})
 }

pkg/storage/s3/storage.go

@@ -17,6 +17,7 @@ import (
 	zlog "github.com/anuvu/zot/pkg/log"
 	"github.com/anuvu/zot/pkg/storage"
 	guuid "github.com/gofrs/uuid"
+	"github.com/notaryproject/notation-go-lib"
 	godigest "github.com/opencontainers/go-digest"
 	ispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/rs/zerolog"
@@ -1018,6 +1019,10 @@ func (is *ObjectStorage) GetBlobContent(repo string, digest string) ([]byte, err
 	return buf.Bytes(), nil
 }
 
+func (is *ObjectStorage) GetReferrers(repo, digest string, mediaType string) ([]notation.Descriptor, error) {
+	return nil, errors.ErrMethodNotSupported
+}
+
 func (is *ObjectStorage) GetIndexContent(repo string) ([]byte, error) {
 	dir := path.Join(is.rootDir, repo)
 

pkg/storage/storage.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"io"
 
+	"github.com/notaryproject/notation-go-lib"
 	"github.com/opencontainers/go-digest"
 )
 
@@ -40,4 +41,5 @@ type ImageStore interface {
 	DeleteBlob(repo string, digest string) error
 	GetIndexContent(repo string) ([]byte, error)
 	GetBlobContent(repo, digest string) ([]byte, error)
+	GetReferrers(repo, digest string, mediaType string) ([]notation.Descriptor, error)
 }

pkg/storage/storage_fs.go

@@ -15,11 +15,14 @@ import (
 	"sync"
 	"time"
 
+	artifactspec "github.com/oras-project/artifacts-spec/specs-go/v1"
+
 	"github.com/anuvu/zot/errors"
 	"github.com/anuvu/zot/pkg/extensions/monitoring"
 	zlog "github.com/anuvu/zot/pkg/log"
 	apexlog "github.com/apex/log"
 	guuid "github.com/gofrs/uuid"
+	"github.com/notaryproject/notation-go-lib"
 	godigest "github.com/opencontainers/go-digest"
 	ispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/opencontainers/umoci"
@@ -437,7 +440,7 @@ func (is *ImageStoreFS) PutImageManifest(repo string, reference string, mediaTyp
 		return "", err
 	}
 
-	if mediaType != ispec.MediaTypeImageManifest {
+	if !IsSupportedMediaType(mediaType) {
 		is.log.Debug().Interface("actual", mediaType).
 			Interface("expected", ispec.MediaTypeImageManifest).Msg("bad manifest media type")
 		return "", errors.ErrBadManifest
@@ -448,6 +451,7 @@ func (is *ImageStoreFS) PutImageManifest(repo string, reference string, mediaTyp
 		return "", errors.ErrBadManifest
 	}
 
+	if mediaType == ispec.MediaTypeImageManifest {
 		var m ispec.Manifest
 		if err := json.Unmarshal(body, &m); err != nil {
 			is.log.Error().Err(err).Msg("unable to unmarshal JSON")
@@ -469,6 +473,13 @@ func (is *ImageStoreFS) PutImageManifest(repo string, reference string, mediaTyp
 				return digest.String(), errors.ErrBlobNotFound
 			}
 		}
+	} else if mediaType == artifactspec.MediaTypeArtifactManifest {
+		var m notation.Descriptor
+		if err := json.Unmarshal(body, &m); err != nil {
+			is.log.Error().Err(err).Msg("unable to unmarshal JSON")
+			return "", errors.ErrBadManifest
+		}
+	}
 
 	mDigest := godigest.FromBytes(body)
 	refIsDigest := false
@@ -1264,6 +1275,90 @@ func (is *ImageStoreFS) DeleteBlob(repo string, digest string) error {
 	return nil
 }
 
+func (is *ImageStoreFS) GetReferrers(repo, digest string, mediaType string) ([]notation.Descriptor, error) {
+	dir := path.Join(is.rootDir, repo)
+	if !is.DirExists(dir) {
+		return nil, errors.ErrRepoNotFound
+	}
+
+	gdigest, err := godigest.Parse(digest)
+	if err != nil {
+		is.log.Error().Err(err).Str("digest", digest).Msg("failed to parse digest")
+		return nil, errors.ErrBadBlobDigest
+	}
+
+	is.RLock()
+	defer is.RUnlock()
+
+	buf, err := ioutil.ReadFile(path.Join(dir, "index.json"))
+
+	if err != nil {
+		is.log.Error().Err(err).Str("dir", dir).Msg("failed to read index.json")
+
+		if os.IsNotExist(err) {
+			return nil, errors.ErrRepoNotFound
+		}
+
+		return nil, err
+	}
+
+	var index ispec.Index
+	if err := json.Unmarshal(buf, &index); err != nil {
+		is.log.Error().Err(err).Str("dir", dir).Msg("invalid JSON")
+		return nil, err
+	}
+
+	found := false
+
+	result := []notation.Descriptor{}
+
+	for _, m := range index.Manifests {
+		if m.MediaType != artifactspec.MediaTypeArtifactManifest {
+			continue
+		}
+
+		p := path.Join(dir, "blobs", m.Digest.Algorithm().String(), m.Digest.Encoded())
+
+		buf, err = ioutil.ReadFile(p)
+
+		if err != nil {
+			is.log.Error().Err(err).Str("blob", p).Msg("failed to read manifest")
+
+			if os.IsNotExist(err) {
+				return nil, errors.ErrManifestNotFound
+			}
+
+			return nil, err
+		}
+
+		var manifest artifactspec.Manifest
+		if err := json.Unmarshal(buf, &manifest); err != nil {
+			is.log.Error().Err(err).Str("dir", dir).Msg("invalid JSON")
+			return nil, err
+		}
+
+		if mediaType != manifest.ArtifactType || gdigest != manifest.Subject.Digest {
+			continue
+		}
+
+		result = append(result, notation.Descriptor{MediaType: m.MediaType,
+			Digest: m.Digest, Size: m.Size, Annotations: m.Annotations})
+
+		found = true
+	}
+
+	if !found {
+		return nil, errors.ErrManifestNotFound
+	}
+
+	return result, nil
+}
+
+func IsSupportedMediaType(mediaType string) bool {
+	return mediaType == ispec.MediaTypeImageManifest ||
+		mediaType == artifactspec.MediaTypeArtifactManifest
+}
+
 // garbage collection
 
 // Scrub will clean up all unreferenced blobs.

pkg/storage/storage_fs_test.go

@@ -122,6 +122,16 @@ func TestStorageFSAPIs(t *testing.T) {
 				panic(err)
 			}
 
+			// invalid GetReferrers
+			_, err = il.GetReferrers("invalid", "invalid", "invalid")
+			So(err, ShouldNotBeNil)
+
+			_, err = il.GetReferrers(repoName, "invalid", "invalid")
+			So(err, ShouldNotBeNil)
+
+			_, err = il.GetReferrers(repoName, d.String(), "invalid")
+			So(err, ShouldNotBeNil)
+
 			// invalid DeleteImageManifest
 			indexPath := path.Join(il.RootDir(), repoName, "index.json")
 			err = os.Chmod(indexPath, 0000)