Add VNFS image cache of oci registry based images

internal/pkg/oci/puller.go

@@ -0,0 +1,182 @@
+package oci
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/containers/image/copy"
+	"github.com/containers/image/docker"
+	"github.com/containers/image/oci/layout"
+	"github.com/containers/image/signature"
+	"github.com/containers/image/types"
+	imgSpecs "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/opencontainers/umoci"
+	"github.com/opencontainers/umoci/oci/layer"
+)
+
+type pullerOpt func(*puller) error
+
+func optSetBlobCachePath(path string) pullerOpt {
+	return func(p *puller) error {
+		p.blobCachePath = path
+		return nil
+	}
+}
+
+func optSetTmpDirPath(path string) pullerOpt {
+	return func(p *puller) error {
+		p.tmpDirPath = path
+		return nil
+	}
+}
+
+func optSetSystemContext(s *types.SystemContext) pullerOpt {
+	return func(p *puller) error {
+		p.sysCtx = s
+		return nil
+	}
+}
+
+type puller struct {
+	id            string
+	blobCachePath string
+	tmpDirPath    string
+	sysCtx        *types.SystemContext
+}
+
+func newPuller(opts ...pullerOpt) (*puller, error) {
+	p := &puller{
+		// default to a sensible value, but caller should set this with opts
+		blobCachePath: filepath.Join(defaultCachePath, blobPrefix),
+	}
+
+	for _, o := range opts {
+		if err := o(p); err != nil {
+			return nil, err
+		}
+	}
+
+	return p, nil
+}
+
+// stripScheme prepares the docker uri for external library parsing and returns an error
+// if it detects a malformed schema
+func stripScheme(uri string) (string, error) {
+	if !strings.HasPrefix(uri, "docker://") {
+		return "", fmt.Errorf("unsupported uri schema: %q", uri)
+	}
+
+	return strings.TrimPrefix(uri, "docker:"), nil
+}
+
+// generateID stores and returns a unique identifier derived from the sha256sum of the image manifest
+func (p *puller) generateID(ctx context.Context, uri string) (string, error) {
+	cleanURI, err := stripScheme(uri)
+	if err != nil {
+		return "", err
+	}
+
+	ref, err := docker.ParseReference(cleanURI)
+	if err != nil {
+		return "", err
+	}
+
+	src, err := ref.NewImageSource(ctx, nil)
+	if err != nil {
+		return "", err
+	}
+
+	manifestBytes, _, err := src.GetManifest(ctx, nil)
+	if err != nil {
+		return "", err
+	}
+
+	p.id = fmt.Sprintf("sha256:%x", sha256.Sum256(manifestBytes))
+	return p.id, nil
+}
+
+func (p *puller) pull(ctx context.Context, uri, dst string) (err error) {
+	cleanURI, err := stripScheme(uri)
+	if err != nil {
+		return err
+	}
+
+	srcRef, err := docker.ParseReference(cleanURI)
+	if err != nil {
+		return fmt.Errorf("unable to parse uri: %v", err)
+	}
+
+	cacheRef, err := layout.ParseReference(p.blobCachePath + ":" + p.id)
+	if err != nil {
+		return fmt.Errorf("unable to generate local oci reference: %v", err)
+	}
+
+	// Create a wide open oci image signature policy
+	policy := &signature.Policy{Default: []signature.PolicyRequirement{signature.NewPRInsecureAcceptAnything()}}
+	policyCtx, err := signature.NewPolicyContext(policy)
+	if err != nil {
+		return fmt.Errorf("unable to create policy context: %v", err)
+	}
+
+	// copy to cache location
+	_, err = copy.Image(ctx, policyCtx, cacheRef, srcRef, &copy.Options{
+		ReportWriter: os.Stdout,
+		SourceCtx:    p.sysCtx,
+	})
+	if err != nil {
+		return err
+	}
+
+	// defaults to $TMPDIR or /tmp
+	tmpDir, err := ioutil.TempDir(p.tmpDirPath, "oci-bundle-")
+	if err != nil {
+		return err
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// create an oci bundle our tmpdir to avoid issues with umoci.UnpackRootfs()
+	tmpRef, err := layout.ParseReference(tmpDir + ":" + "tmp")
+	if err != nil {
+		return fmt.Errorf("unable to generate local oci reference: %v", err)
+	}
+
+	// copy to temporary location
+	_, err = copy.Image(ctx, policyCtx, tmpRef, cacheRef, &copy.Options{})
+	if err != nil {
+		return err
+	}
+
+	tmp, err := tmpRef.NewImageSource(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	manifestBytes, _, err := tmp.GetManifest(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	var manifest imgSpecs.Manifest
+	if err := json.Unmarshal(manifestBytes, &manifest); err != nil {
+		return fmt.Errorf("unable to unmarshall mafinest json: %v", err)
+	}
+
+	eng, err := umoci.OpenLayout(tmpDir)
+	if err != nil {
+		return fmt.Errorf("unable to open oci layout: %v", err)
+	}
+
+	var mo layer.MapOptions
+	err = layer.UnpackRootfs(ctx, eng, dst, manifest, &mo, nil, imgSpecs.Descriptor{})
+	if err != nil {
+		return fmt.Errorf("unable to unpack rootfs: %v", err)
+	}
+
+	return nil
+}