client: Use the umoci Go package instead of the command

Signed-off-by: Piotr Resztak <piotr.resztak@futurfusion.io>

client/oci_images.go

@@ -155,11 +155,6 @@ func (r *ProtocolOCI) GetImageFile(fingerprint string, req ImageFileRequest) (*I
 		return nil, fmt.Errorf("OCI image export currently requires root access")
 	}
 
-	_, err = exec.LookPath("umoci")
-	if err != nil {
-		return nil, fmt.Errorf("OCI container handling requires \"umoci\" be present on the system")
-	}
-
 	// Get some temporary storage.
 	ociPath, err := os.MkdirTemp("", "incus-oci-")
 	if err != nil {
@@ -183,6 +178,8 @@ func (r *ProtocolOCI) GetImageFile(fingerprint string, req ImageFileRequest) (*I
 		req.ProgressHandler(ioprogress.ProgressData{Text: "Retrieving OCI image from registry"})
 	}
 
+	imageTag := "latest"
+
 	stdout, _, err := subprocess.RunCommandSplit(
 		ctx,
 		env,
@@ -192,7 +189,7 @@ func (r *ProtocolOCI) GetImageFile(fingerprint string, req ImageFileRequest) (*I
 		"copy",
 		"--remove-signatures",
 		fmt.Sprintf("%s/%s", strings.Replace(r.httpHost, "https://", "docker://", 1), info.Alias),
-		fmt.Sprintf("oci:%s:latest", filepath.Join(ociPath, "oci")))
+		fmt.Sprintf("oci:%s:%s", filepath.Join(ociPath, "oci"), imageTag))
 	if err != nil {
 		logger.Debug("Error copying remote image to local", logger.Ctx{"image": info.Alias, "stdout": stdout, "stderr": err})
 		return nil, err
@@ -203,14 +200,9 @@ func (r *ProtocolOCI) GetImageFile(fingerprint string, req ImageFileRequest) (*I
 		req.ProgressHandler(ioprogress.ProgressData{Text: "Unpacking the OCI image"})
 	}
 
-	stdout, err = subprocess.RunCommand(
-		"umoci",
-		"unpack",
-		"--keep-dirlinks",
-		"--image", filepath.Join(ociPath, "oci"),
-		filepath.Join(ociPath, "image"))
+	err = unpackOCIImage(filepath.Join(ociPath, "oci"), imageTag, filepath.Join(ociPath, "image"))
 	if err != nil {
-		logger.Debug("Error unpacking OCI image", logger.Ctx{"image": filepath.Join(ociPath, "oci"), "stdout": stdout, "stderr": err})
+		logger.Debug("Error unpacking OCI image", logger.Ctx{"image": filepath.Join(ociPath, "oci"), "err": err})
 		return nil, err
 	}
 

client/oci_util.go

@@ -0,0 +1,11 @@
+//go:build !linux
+
+package incus
+
+import (
+	"fmt"
+)
+
+func unpackOCIImage(imagePath string, imageTag string, bundlePath string) error {
+	return fmt.Errorf("Platform isn't supported")
+}

client/oci_util_linux.go

@@ -0,0 +1,60 @@
+//go:build linux
+
+package incus
+
+import (
+	"fmt"
+
+	"github.com/apex/log"
+	"github.com/opencontainers/umoci"
+	"github.com/opencontainers/umoci/oci/cas/dir"
+	"github.com/opencontainers/umoci/oci/casext"
+	"github.com/opencontainers/umoci/oci/layer"
+
+	"github.com/lxc/incus/v6/shared/logger"
+)
+
+// Custom handler to intercept logs.
+type umociLogHandler struct {
+	Message string
+}
+
+// HandleLog implements a proxy between apex/log and our logger.
+func (h *umociLogHandler) HandleLog(e *log.Entry) error {
+	switch e.Level {
+	case log.DebugLevel:
+		logger.Debug(h.Message, logger.Ctx{"log": e.Message})
+	case log.InfoLevel:
+		logger.Info(h.Message, logger.Ctx{"log": e.Message})
+	case log.WarnLevel:
+		logger.Warn(h.Message, logger.Ctx{"log": e.Message})
+	case log.ErrorLevel:
+		logger.Error(h.Message, logger.Ctx{"log": e.Message})
+	case log.FatalLevel:
+		logger.Panic(h.Message, logger.Ctx{"log": e.Message})
+	default:
+		logger.Error("Unknown umoci log level", logger.Ctx{"log": e.Message})
+	}
+
+	return nil
+}
+
+func unpackOCIImage(imagePath string, imageTag string, bundlePath string) error {
+	// Set the custom handler
+	log.SetHandler(&umociLogHandler{Message: "Unpacking OCI image"})
+	defer log.SetHandler(nil)
+
+	var unpackOptions layer.UnpackOptions
+	unpackOptions.KeepDirlinks = true
+
+	// Get a reference to the CAS.
+	engine, err := dir.Open(imagePath)
+	if err != nil {
+		return fmt.Errorf("Open CAS: %w", err)
+	}
+
+	engineExt := casext.NewEngine(engine)
+	defer func() { _ = engine.Close() }()
+
+	return umoci.Unpack(engineExt, imageTag, bundlePath, unpackOptions)
+}