Fix "oras" OCI client compatibility (#34666)

Fix #25846

1. the ImageConfig can be empty, fall back to default
2. the blob size can be empty, it still needs "Content-Length" header

modules/packages/container/metadata.go

@@ -4,6 +4,7 @@
 package container
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"strings"
@@ -83,7 +84,8 @@ func ParseImageConfig(mt string, r io.Reader) (*Metadata, error) {
 
 func parseOCIImageConfig(r io.Reader) (*Metadata, error) {
 	var image oci.Image
-	if err := json.NewDecoder(r).Decode(&image); err != nil {
+	// EOF means empty input, still use the default data
+	if err := json.NewDecoder(r).Decode(&image); err != nil && !errors.Is(err, io.EOF) {
 		return nil, err
 	}
 

modules/packages/container/metadata_test.go

@@ -11,6 +11,7 @@ import (
 
 	oci "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestParseImageConfig(t *testing.T) {
@@ -59,3 +60,9 @@ func TestParseImageConfig(t *testing.T) {
 	assert.Equal(t, projectURL, metadata.ProjectURL)
 	assert.Equal(t, repositoryURL, metadata.RepositoryURL)
 }
+
+func TestParseOCIImageConfig(t *testing.T) {
+	metadata, err := parseOCIImageConfig(strings.NewReader(""))
+	require.NoError(t, err)
+	assert.Equal(t, &Metadata{Type: TypeOCI, Platform: DefaultPlatform, ImageLayers: []string{}}, metadata)
+}

routers/api/packages/container/container.go

@@ -21,6 +21,7 @@ import (
 	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
 	packages_module "code.gitea.io/gitea/modules/packages"
 	container_module "code.gitea.io/gitea/modules/packages/container"
 	"code.gitea.io/gitea/modules/setting"
@@ -50,7 +51,7 @@ type containerHeaders struct {
 	Range         string
 	Location      string
 	ContentType   string
-	ContentLength int64
+	ContentLength optional.Option[int64]
 }
 
 // https://github.com/opencontainers/distribution-spec/blob/main/spec.md#legacy-docker-support-http-headers
@@ -64,8 +65,8 @@ func setResponseHeaders(resp http.ResponseWriter, h *containerHeaders) {
 	if h.ContentType != "" {
 		resp.Header().Set("Content-Type", h.ContentType)
 	}
-	if h.ContentLength != 0 {
-		resp.Header().Set("Content-Length", strconv.FormatInt(h.ContentLength, 10))
+	if h.ContentLength.Has() {
+		resp.Header().Set("Content-Length", strconv.FormatInt(h.ContentLength.Value(), 10))
 	}
 	if h.UploadUUID != "" {
 		resp.Header().Set("Docker-Upload-Uuid", h.UploadUUID)
@@ -505,7 +506,7 @@ func HeadBlob(ctx *context.Context) {
 
 	setResponseHeaders(ctx.Resp, &containerHeaders{
 		ContentDigest: blob.Properties.GetByName(container_module.PropertyDigest),
-		ContentLength: blob.Blob.Size,
+		ContentLength: optional.Some(blob.Blob.Size),
 		Status:        http.StatusOK,
 	})
 }
@@ -644,7 +645,7 @@ func HeadManifest(ctx *context.Context) {
 	setResponseHeaders(ctx.Resp, &containerHeaders{
 		ContentDigest: manifest.Properties.GetByName(container_module.PropertyDigest),
 		ContentType:   manifest.Properties.GetByName(container_module.PropertyMediaType),
-		ContentLength: manifest.Blob.Size,
+		ContentLength: optional.Some(manifest.Blob.Size),
 		Status:        http.StatusOK,
 	})
 }
@@ -708,14 +709,14 @@ func serveBlob(ctx *context.Context, pfd *packages_model.PackageFileDescriptor)
 	headers := &containerHeaders{
 		ContentDigest: pfd.Properties.GetByName(container_module.PropertyDigest),
 		ContentType:   pfd.Properties.GetByName(container_module.PropertyMediaType),
-		ContentLength: pfd.Blob.Size,
+		ContentLength: optional.Some(pfd.Blob.Size),
 		Status:        http.StatusOK,
 	}
 
 	if u != nil {
 		headers.Status = http.StatusTemporaryRedirect
 		headers.Location = u.String()
-		headers.ContentLength = 0 // do not set Content-Length for redirect responses
+		headers.ContentLength = optional.None[int64]() // do not set Content-Length for redirect responses
 		setResponseHeaders(ctx.Resp, headers)
 		return
 	}

tests/integration/api_packages_container_test.go

@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"crypto/sha256"
 	"encoding/base64"
+	"encoding/hex"
 	"fmt"
 	"net/http"
 	"strconv"
@@ -623,6 +624,22 @@ func TestPackageContainer(t *testing.T) {
 				assert.Equal(t, blobContent, resp.Body.Bytes())
 			})
 
+			t.Run("GetBlob/Empty", func(t *testing.T) {
+				defer tests.PrintCurrentTest(t)()
+				emptyDigestBuf := sha256.Sum256(nil)
+				emptyDigest := "sha256:" + hex.EncodeToString(emptyDigestBuf[:])
+				req := NewRequestWithBody(t, "POST", fmt.Sprintf("%s/blobs/uploads?digest=%s", url, emptyDigest), strings.NewReader("")).AddTokenAuth(userToken)
+				MakeRequest(t, req, http.StatusCreated)
+
+				req = NewRequest(t, "HEAD", fmt.Sprintf("%s/blobs/%s", url, emptyDigest)).AddTokenAuth(userToken)
+				resp := MakeRequest(t, req, http.StatusOK)
+				assert.Equal(t, "0", resp.Header().Get("Content-Length"))
+
+				req = NewRequest(t, "GET", fmt.Sprintf("%s/blobs/%s", url, emptyDigest)).AddTokenAuth(userToken)
+				resp = MakeRequest(t, req, http.StatusOK)
+				assert.Equal(t, "0", resp.Header().Get("Content-Length"))
+			})
+
 			t.Run("GetTagList", func(t *testing.T) {
 				defer tests.PrintCurrentTest(t)()