feat(imagepush): 写出按架构的发布镜像包并支持按名推送

cmd/felis/imagebundle.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+
+	"felis.lolicon.best/internal/imagepush"
+)
+
+// cmdImageBundle writes a release's image bundle: one OCI layout tar holding every
+// image an install runs, for one platform, plus its listing (one "role name
+// manifest-digest config-digest" line per image). deploy/build-release-artifacts.sh
+// runs it in CI; deploy/bootstrap.sh imports the tar into k3s's containerd and
+// pushes it into the platform registry with push-image --image.
+//
+//	--layout role=name=path   an image buildx wrote with --output type=oci
+//	--pull role=ref           a digest-pinned public image, named repository@digest
+//
+// The tar and the listing are written beside their final paths and renamed into
+// place, so a failed run leaves neither behind.
+func cmdImageBundle(args []string, _, stderr io.Writer) int {
+	fs := flag.NewFlagSet("image-bundle", flag.ContinueOnError)
+	fs.SetOutput(stderr)
+	platform := fs.String("platform", "", "os/arch the bundle is for, e.g. linux/arm64")
+	out := fs.String("out", "", "path of the bundle tar to write")
+	list := fs.String("list", "", "path of the listing to write")
+	var images []imagepush.BundleImage
+	fs.Func("layout", "role=name=path of an OCI layout tar (repeatable)", func(v string) error {
+		role, rest, ok := strings.Cut(v, "=")
+		name, path, ok2 := strings.Cut(rest, "=")
+		if !ok || !ok2 || role == "" || name == "" || path == "" {
+			return fmt.Errorf("want role=name=path, got %q", v)
+		}
+		images = append(images, imagepush.BundleImage{Role: role, Name: name, Layout: path})
+		return nil
+	})
+	fs.Func("pull", "role=ref of a digest-pinned public image (repeatable)", func(v string) error {
+		role, ref, ok := strings.Cut(v, "=")
+		if !ok || role == "" || !strings.Contains(ref, "@sha256:") {
+			return fmt.Errorf("want role=ref with ref pinned by digest, got %q", v)
+		}
+		images = append(images, imagepush.BundleImage{Role: role, Name: imagepush.PinnedName(ref), Source: ref})
+		return nil
+	})
+	if err := fs.Parse(args); err != nil {
+		if errors.Is(err, flag.ErrHelp) {
+			return 0
+		}
+		return 2
+	}
+	if *platform == "" || *out == "" || *list == "" || len(images) == 0 {
+		fmt.Fprintln(stderr, "felis image-bundle: --platform, --out, --list and at least one --layout or --pull are required")
+		return 2
+	}
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+	if err := writeImageBundle(ctx, &imagepush.Source{Platform: *platform}, images, *out, *list); err != nil {
+		fmt.Fprintf(stderr, "felis image-bundle: %v\n", err)
+		return 1
+	}
+	return 0
+}
+
+func writeImageBundle(ctx context.Context, s *imagepush.Source, images []imagepush.BundleImage, out, list string) (err error) {
+	tmpOut, tmpList := out+".tmp", list+".tmp"
+	defer func() {
+		if err != nil {
+			os.Remove(tmpOut)
+			os.Remove(tmpList)
+		}
+	}()
+	f, err := os.Create(tmpOut)
+	if err != nil {
+		return err
+	}
+	w := bufio.NewWriterSize(f, 1<<20)
+	entries, err := imagepush.WriteBundle(ctx, s, images, w)
+	if err == nil {
+		err = w.Flush()
+	}
+	if err == nil {
+		err = f.Sync()
+	}
+	if cerr := f.Close(); err == nil {
+		err = cerr
+	}
+	if err != nil {
+		return err
+	}
+	var b strings.Builder
+	for _, e := range entries {
+		fmt.Fprintf(&b, "%s %s %s %s\n", e.Role, e.Name, e.Digest, e.Config)
+	}
+	if err := os.WriteFile(tmpList, []byte(b.String()), 0o644); err != nil {
+		return err
+	}
+	if err := os.Rename(tmpOut, out); err != nil {
+		return err
+	}
+	return os.Rename(tmpList, list)
+}

cmd/felis/imagebundle_test.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"archive/tar"
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// writeTestLayout writes an OCI layout tar holding one linux/arch image with one
+// layer, the way buildx --output type=oci leaves a single-platform build, and
+// returns its path with the manifest and config digests.
+func writeTestLayout(t *testing.T, dir, arch, layer string) (path, manifestDigest, configDigest string) {
+	t.Helper()
+	blobs := map[string][]byte{}
+	add := func(b []byte) (string, int) {
+		sum := sha256.Sum256(b)
+		d := "sha256:" + hex.EncodeToString(sum[:])
+		blobs[d] = b
+		return d, len(b)
+	}
+	cfgDigest, cfgSize := add([]byte(`{"architecture":"` + arch + `","os":"linux","rootfs":{"type":"layers"}}`))
+	layerDigest, layerSize := add([]byte(layer))
+	manifest := fmt.Sprintf(`{"schemaVersion":2,"mediaType":"application/vnd.oci.image.manifest.v1+json",`+
+		`"config":{"mediaType":"application/vnd.oci.image.config.v1+json","digest":%q,"size":%d},`+
+		`"layers":[{"mediaType":"application/vnd.oci.image.layer.v1.tar+gzip","digest":%q,"size":%d}]}`,
+		cfgDigest, cfgSize, layerDigest, layerSize)
+	mDigest, mSize := add([]byte(manifest))
+	index, _ := json.Marshal(map[string]any{
+		"schemaVersion": 2,
+		"manifests": []map[string]any{{
+			"mediaType": "application/vnd.oci.image.manifest.v1+json", "digest": mDigest, "size": mSize,
+		}},
+	})
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	put := func(name string, b []byte) {
+		tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(b)), Typeflag: tar.TypeReg})
+		tw.Write(b)
+	}
+	put("oci-layout", []byte(`{"imageLayoutVersion":"1.0.0"}`))
+	put("index.json", index)
+	for d, b := range blobs {
+		put("blobs/sha256/"+strings.TrimPrefix(d, "sha256:"), b)
+	}
+	tw.Close()
+	path = filepath.Join(dir, arch+"-"+layer+".tar")
+	if err := os.WriteFile(path, buf.Bytes(), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return path, mDigest, cfgDigest
+}
+
+func TestImageBundleWritesTheListingTheInstallerReads(t *testing.T) {
+	dir := t.TempDir()
+	limbo, limboDigest, limboConfig := writeTestLayout(t, dir, "arm64", "limbo")
+	lobby, lobbyDigest, lobbyConfig := writeTestLayout(t, dir, "arm64", "lobby")
+	out, list := filepath.Join(dir, "images.tar"), filepath.Join(dir, "images.txt")
+	var stderr bytes.Buffer
+	code := cmdImageBundle([]string{"--platform", "linux/arm64", "--out", out, "--list", list,
+		"--layout", "limbo=registry.felis.svc:5000/felis/limbo:demo=" + limbo,
+		"--layout", "lobby=registry.felis.svc:5000/felis/lobby:demo=" + lobby,
+	}, nil, &stderr)
+	if code != 0 {
+		t.Fatalf("image-bundle = %d: %s", code, stderr.String())
+	}
+	// deploy/bootstrap.sh reads this with `read -r role name digest config`.
+	got, _ := os.ReadFile(list)
+	want := "limbo registry.felis.svc:5000/felis/limbo:demo " + limboDigest + " " + limboConfig + "\n" +
+		"lobby registry.felis.svc:5000/felis/lobby:demo " + lobbyDigest + " " + lobbyConfig + "\n"
+	if string(got) != want {
+		t.Errorf("listing:\n%s\nwant:\n%s", got, want)
+	}
+	if fi, err := os.Stat(out); err != nil || fi.Size() == 0 {
+		t.Errorf("bundle: %v", err)
+	}
+	if leftovers, _ := filepath.Glob(filepath.Join(dir, "*.tmp")); len(leftovers) != 0 {
+		t.Errorf("left behind %v", leftovers)
+	}
+}
+
+func TestImageBundleLeavesNothingWhenAnImageIsRefused(t *testing.T) {
+	dir := t.TempDir()
+	amd, _, _ := writeTestLayout(t, dir, "amd64", "limbo")
+	out, list := filepath.Join(dir, "images.tar"), filepath.Join(dir, "images.txt")
+	// The pair an earlier run wrote stays as it was: a listing beside a bundle it
+	// does not describe would have the installer look for images that are not there.
+	os.WriteFile(out, []byte("old bundle"), 0o644)
+	os.WriteFile(list, []byte("old listing\n"), 0o644)
+	var stderr bytes.Buffer
+	code := cmdImageBundle([]string{"--platform", "linux/arm64", "--out", out, "--list", list,
+		"--layout", "limbo=registry.felis.svc:5000/felis/limbo:demo=" + amd}, nil, &stderr)
+	if code != 1 || !strings.Contains(stderr.String(), "is a linux/amd64 image") {
+		t.Fatalf("image-bundle = %d: %s", code, stderr.String())
+	}
+	if got, _ := os.ReadFile(out); string(got) != "old bundle" {
+		t.Errorf("bundle was replaced with %d bytes", len(got))
+	}
+	if got, _ := os.ReadFile(list); string(got) != "old listing\n" {
+		t.Errorf("listing was replaced with %q", got)
+	}
+	if leftovers, _ := filepath.Glob(filepath.Join(dir, "*.tmp")); len(leftovers) != 0 {
+		t.Errorf("left behind %v", leftovers)
+	}
+}
+
+func TestPushImageReadsABundleByImageName(t *testing.T) {
+	dir := t.TempDir()
+	limbo, _, _ := writeTestLayout(t, dir, "arm64", "limbo")
+	out, list := filepath.Join(dir, "images.tar"), filepath.Join(dir, "images.txt")
+	if code := cmdImageBundle([]string{"--platform", "linux/arm64", "--out", out, "--list", list,
+		"--layout", "limbo=registry.felis.svc:5000/felis/limbo:demo=" + limbo}, nil, &bytes.Buffer{}); code != 0 {
+		t.Fatal("image-bundle failed")
+	}
+	t.Setenv("FELIS_REGISTRY_USERNAME", "platform")
+	t.Setenv("FELIS_REGISTRY_PASSWORD", "x")
+	// The name is looked up in the bundle's index before the registry is contacted,
+	// so a name the bundle lacks fails here with what it does hold.
+	var stderr bytes.Buffer
+	code := cmdPushImage([]string{"--tar", out, "--image", "registry.felis.svc:5000/felis/lobby:demo",
+		"--ref", "127.0.0.1:1/felis/lobby:demo"}, &bytes.Buffer{}, &stderr)
+	if code != 1 || !strings.Contains(stderr.String(), "holds no image named registry.felis.svc:5000/felis/lobby:demo (it holds: registry.felis.svc:5000/felis/limbo:demo") {
+		t.Fatalf("push-image = %d: %s", code, stderr.String())
+	}
+}

cmd/felis/registrygate.go

@@ -131,7 +131,8 @@ func loopbackAddr(addr string) bool {
 func cmdPushImage(args []string, stdout, stderr io.Writer) int {
 	fs := flag.NewFlagSet("push-image", flag.ContinueOnError)
 	fs.SetOutput(stderr)
-	tarPath := fs.String("tar", "", "image tarball Kaniko wrote with --tar-path")
+	tarPath := fs.String("tar", "", "image tarball Kaniko wrote with --tar-path, or with --image an OCI layout tar")
+	image := fs.String("image", "", "push the image this name (io.containerd.image.name) marks in the OCI layout tar --tar, e.g. a release's image bundle")
 	ref := fs.String("ref", "", "host/repository:tag to publish it as")
 	scheme := fs.String("scheme", "http", "registry scheme: http for the in-cluster registry, https otherwise")
 	if err := fs.Parse(args); err != nil {
@@ -154,7 +155,13 @@ func cmdPushImage(args []string, stdout, stderr io.Writer) int {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 	p := &imagepush.Pusher{Scheme: *scheme, Username: user, Password: pass, Log: stderr}
-	digest, err := p.Push(ctx, *tarPath, *ref)
+	var digest string
+	var err error
+	if *image != "" {
+		digest, err = p.PushLayout(ctx, *tarPath, *image, *ref)
+	} else {
+		digest, err = p.Push(ctx, *tarPath, *ref)
+	}
 	if err != nil {
 		fmt.Fprintf(stderr, "felis push-image: %v\n", err)
 		return 1

cmd/felis/run.go

@@ -78,6 +78,7 @@ var commands = map[string]func(args []string, stdout, stderr io.Writer) int{
 	"init-forwarding":    cmdInitForwarding,
 	"init-volume":        cmdInitVolume,
 	"pin-images":         cmdPinImages,
+	"image-bundle":       cmdImageBundle,
 	"version":            cmdVersion,
 	"update":             cmdUpdate,
 	"watchdog":           cmdWatchdog,

cmd/felis/run_test.go

@@ -43,7 +43,7 @@ func TestRunUnknownCommand(t *testing.T) {
 // decision rather than an oversight.
 var undocumentedCommands = map[string]bool{
 	"bootstrap-assets": true, "init-forwarding": true, "init-volume": true,
-	"pin-images": true,
+	"pin-images": true, "image-bundle": true,
 }
 
 // The usage text and the dispatch table must describe the same set of commands.

internal/imagepush/bundle.go

@@ -0,0 +1,356 @@
+package imagepush
+
+import (
+	"archive/tar"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+)
+
+// The release bundle: one OCI layout tar per architecture holding every image an
+// install runs (the control plane, the login, lobby and Paper images, the registry
+// and PostgreSQL), built once by CI. The installer imports it into k3s's containerd
+// and pushes it into the platform registry, so a host needs neither Docker nor
+// Docker Hub to install.
+//
+// Every index.json entry points straight at one platform's image manifest: no
+// nested index, no platform field, no descriptor whose blobs are missing. ctr's
+// importer then imports each entry the same way whatever platform matcher it runs
+// with, and the digest a pod pins is the digest containerd holds.
+
+// BundleImage is one image WriteBundle puts in a bundle.
+type BundleImage struct {
+	// Role is the image's job in the install (felis, limbo, registry, ...), for the
+	// listing the installer reads.
+	Role string
+	// Name is the containerd image name the bundle gives it.
+	Name string
+	// Layout is an OCI layout tar (buildx --output type=oci) holding the image.
+	Layout string
+	// Source is a digest-pinned reference to read it from a public registry when
+	// Layout is empty.
+	Source string
+}
+
+// BundleEntry describes one image of a written bundle.
+type BundleEntry struct {
+	Role, Name string
+	// Digest is the image manifest's digest; Config its config's, which is the
+	// image ID docker and CRI report.
+	Digest, Config string
+}
+
+// bundleTime stamps every tar header, so two runs over the same images write the
+// same bytes.
+var bundleTime = time.Unix(0, 0).UTC()
+
+// resolvedImage is a BundleImage narrowed to one platform's manifest.
+type resolvedImage struct {
+	BundleImage
+	mediaType string
+	body      []byte
+	m         *manifest
+	config    []byte
+	// open returns one blob's bytes; the writer checks them against the digest.
+	open func(ctx context.Context, d descriptor) (io.ReadCloser, error)
+}
+
+// WriteBundle writes the images as one OCI layout tar to w, each narrowed to s's
+// platform, and returns what it wrote. Every blob is checked against its digest on
+// the way through, and every image's config must be for the platform, so a bundle
+// cannot carry an image another architecture's build left behind.
+func WriteBundle(ctx context.Context, s *Source, images []BundleImage, w io.Writer) ([]BundleEntry, error) {
+	goos, arch, _ := s.platform()
+	seenRole, seenName := map[string]bool{}, map[string]bool{}
+	var resolved []*resolvedImage
+	for _, img := range images {
+		if img.Role == "" || img.Name == "" {
+			return nil, fmt.Errorf("imagepush: bundle image %+v needs a role and a name", img)
+		}
+		if seenRole[img.Role] || seenName[img.Name] {
+			return nil, fmt.Errorf("imagepush: bundle names role %s or image %s twice", img.Role, img.Name)
+		}
+		seenRole[img.Role], seenName[img.Name] = true, true
+		var (
+			r   *resolvedImage
+			err error
+		)
+		switch {
+		case img.Layout != "" && img.Source == "":
+			r, err = resolveLayoutImage(img, s)
+		case img.Source != "" && img.Layout == "":
+			r, err = resolveSourceImage(ctx, img, s)
+		default:
+			err = fmt.Errorf("imagepush: bundle image %s needs exactly one of a layout and a source", img.Name)
+		}
+		if err != nil {
+			return nil, err
+		}
+		var cfg struct {
+			OS           string `json:"os"`
+			Architecture string `json:"architecture"`
+		}
+		if err := json.Unmarshal(r.config, &cfg); err != nil {
+			return nil, fmt.Errorf("imagepush: %s: config: %w", img.Name, err)
+		}
+		if cfg.OS != goos || cfg.Architecture != arch {
+			return nil, fmt.Errorf("imagepush: %s is a %s/%s image, the bundle is for %s/%s", img.Name, cfg.OS, cfg.Architecture, goos, arch)
+		}
+		resolved = append(resolved, r)
+	}
+
+	tw := tar.NewWriter(w)
+	written := map[string]int64{}
+	writeBytes := func(name string, b []byte) error {
+		if err := tw.WriteHeader(bundleHeader(name, int64(len(b)))); err != nil {
+			return err
+		}
+		_, err := tw.Write(b)
+		return err
+	}
+	if err := writeBytes(layoutMarkerFile, []byte(layoutMarkerContent)); err != nil {
+		return nil, err
+	}
+	for _, dir := range []string{"blobs/", "blobs/sha256/"} {
+		h := bundleHeader(dir, 0)
+		h.Typeflag, h.Mode = tar.TypeDir, 0o755
+		if err := tw.WriteHeader(h); err != nil {
+			return nil, err
+		}
+	}
+	var (
+		index   = layoutIndex{SchemaVersion: 2, MediaType: mediaOCIIndex}
+		entries []BundleEntry
+	)
+	for _, r := range resolved {
+		for _, d := range append([]descriptor{r.m.Config}, r.m.Layers...) {
+			if size, ok := written[d.Digest]; ok {
+				if size != d.Size {
+					return nil, fmt.Errorf("imagepush: %s: blob %s is %d bytes here and %d bytes in an earlier image", r.Name, d.Digest, d.Size, size)
+				}
+				continue
+			}
+			if err := copyBlob(ctx, tw, r, d); err != nil {
+				return nil, err
+			}
+			written[d.Digest] = d.Size
+		}
+		digest := digestOf(r.body)
+		if _, ok := written[digest]; !ok {
+			if err := writeBytes(blobPath(digest), r.body); err != nil {
+				return nil, err
+			}
+			written[digest] = int64(len(r.body))
+		}
+		desc := layoutDescriptor{MediaType: r.mediaType, Digest: digest, Size: int64(len(r.body))}
+		for _, name := range bundleNames(r.Name, digest) {
+			e := desc
+			e.Annotations = map[string]string{annotationImageName: name}
+			if tag := refTag(name); tag != "" {
+				e.Annotations[annotationRefName] = tag
+			}
+			index.Manifests = append(index.Manifests, e)
+		}
+		entries = append(entries, BundleEntry{Role: r.Role, Name: r.Name, Digest: digest, Config: r.m.Config.Digest})
+	}
+	body, err := json.Marshal(index)
+	if err != nil {
+		return nil, err
+	}
+	if err := writeBytes(layoutIndexFile, body); err != nil {
+		return nil, err
+	}
+	if err := tw.Close(); err != nil {
+		return nil, err
+	}
+	return entries, nil
+}
+
+func bundleHeader(name string, size int64) *tar.Header {
+	return &tar.Header{Name: name, Mode: 0o644, Size: size, Typeflag: tar.TypeReg, ModTime: bundleTime}
+}
+
+// bundleNames is every name the bundle gives an image: its own, and for a tagged
+// name also repository@digest. Pods run the game images pinned to their digest
+// (felis pin-images), and CRI looks a pinned reference up by that second name, so
+// with it a pinned pod starts from what the bundle imported instead of pulling.
+func bundleNames(name, digest string) []string {
+	if refTag(name) == "" {
+		return []string{name}
+	}
+	return []string{name, refRepo(name) + "@" + digest}
+}
+
+// refTag is the tag of a host/repository:tag name, or "" for a digest name.
+func refTag(name string) string {
+	if strings.Contains(name, "@") {
+		return ""
+	}
+	if i := strings.LastIndexByte(name, ':'); i > strings.LastIndexByte(name, '/') {
+		return name[i+1:]
+	}
+	return ""
+}
+
+// refRepo is a reference with its tag and digest dropped.
+func refRepo(ref string) string {
+	name, _, _ := strings.Cut(ref, "@")
+	if i := strings.LastIndexByte(name, ':'); i > strings.LastIndexByte(name, '/') {
+		return name[:i]
+	}
+	return name
+}
+
+// PinnedName is the name containerd lists a digest-pinned reference under once CRI
+// pulled it: repository@digest, the tag dropped. It is the name a bundle gives an
+// image read from Source, so the pods naming that reference find it.
+func PinnedName(ref string) string {
+	_, digest, _ := strings.Cut(ref, "@")
+	return refRepo(ref) + "@" + digest
+}
+
+// copyBlob streams one blob into the tar, checking its size and digest.
+func copyBlob(ctx context.Context, tw *tar.Writer, r *resolvedImage, d descriptor) error {
+	rc, err := r.open(ctx, d)
+	if err != nil {
+		return fmt.Errorf("imagepush: %s: blob %s: %w", r.Name, d.Digest, err)
+	}
+	defer rc.Close()
+	if err := tw.WriteHeader(bundleHeader(blobPath(d.Digest), d.Size)); err != nil {
+		return err
+	}
+	h := sha256.New()
+	n, err := io.Copy(io.MultiWriter(tw, h), io.LimitReader(rc, d.Size))
+	if err != nil {
+		return fmt.Errorf("imagepush: %s: blob %s: %w", r.Name, d.Digest, err)
+	}
+	// A byte past the descriptor's size is looked for, never written.
+	if extra, _ := io.CopyN(io.Discard, rc, 1); extra > 0 {
+		return fmt.Errorf("imagepush: %s: blob %s is longer than its %d bytes", r.Name, d.Digest, d.Size)
+	}
+	if got := "sha256:" + hex.EncodeToString(h.Sum(nil)); n != d.Size || got != d.Digest {
+		return fmt.Errorf("imagepush: %s: blob %s (%d bytes) holds %s (%d bytes)", r.Name, d.Digest, d.Size, got, n)
+	}
+	return nil
+}
+
+// resolveLayoutImage finds the platform's image in a buildx OCI layout tar.
+func resolveLayoutImage(img BundleImage, s *Source) (*resolvedImage, error) {
+	idx, err := readLayoutIndex(img.Layout)
+	if err != nil {
+		return nil, err
+	}
+	entries := idx.Manifests
+	for depth := 0; depth < 4; depth++ {
+		d, err := pickLayoutEntry(entries, s)
+		if err != nil {
+			return nil, fmt.Errorf("imagepush: %s: %w", img.Layout, err)
+		}
+		body, err := readLayoutBlob(img.Layout, d)
+		if err != nil {
+			return nil, err
+		}
+		if isIndexType(d.MediaType) {
+			var nested layoutIndex
+			if err := json.Unmarshal(body, &nested); err != nil {
+				return nil, fmt.Errorf("imagepush: %s: index %s: %w", img.Layout, d.Digest, err)
+			}
+			entries = nested.Manifests
+			continue
+		}
+		if !isManifestType(d.MediaType) {
+			return nil, fmt.Errorf("imagepush: %s: %s is a %q, want an image", img.Layout, d.Digest, d.MediaType)
+		}
+		m, err := parseManifest(body, d.MediaType)
+		if err != nil {
+			return nil, fmt.Errorf("imagepush: %s: %w", img.Layout, err)
+		}
+		config, err := readLayoutBlob(img.Layout, layoutDescriptor{Digest: m.Config.Digest, Size: m.Config.Size})
+		if err != nil {
+			return nil, err
+		}
+		path := img.Layout
+		return &resolvedImage{BundleImage: img, mediaType: d.MediaType, body: body, m: m, config: config,
+			open: func(_ context.Context, d descriptor) (io.ReadCloser, error) {
+				f, entry, err := openEntry(path, blobPath(d.Digest))
+				if err != nil {
+					return nil, err
+				}
+				return struct {
+					io.Reader
+					io.Closer
+				}{entry, f}, nil
+			}}, nil
+	}
+	return nil, fmt.Errorf("imagepush: %s: indexes nest too deep", img.Layout)
+}
+
+// pickLayoutEntry chooses the entry for s's platform. A lone entry without a
+// platform is taken as it is (its config is checked later); buildx's attestation
+// manifests say unknown/unknown and never match. Releases are built for plain
+// linux/amd64 and linux/arm64, so a variant is not looked at.
+func pickLayoutEntry(entries []layoutDescriptor, s *Source) (layoutDescriptor, error) {
+	if len(entries) == 1 && entries[0].Platform == nil {
+		return entries[0], nil
+	}
+	wantOS, wantArch, _ := s.platform()
+	for _, e := range entries {
+		if e.Platform != nil && e.Platform.OS == wantOS && e.Platform.Architecture == wantArch {
+			return e, nil
+		}
+	}
+	return layoutDescriptor{}, fmt.Errorf("no %s/%s image among %d entries", wantOS, wantArch, len(entries))
+}
+
+// resolveSourceImage reads the platform's manifest of a digest-pinned public image.
+func resolveSourceImage(ctx context.Context, img BundleImage, s *Source) (*resolvedImage, error) {
+	sr, err := ParseSourceRef(img.Source)
+	if err != nil {
+		return nil, err
+	}
+	if sr.Digest == "" {
+		return nil, fmt.Errorf("imagepush: %s is not pinned by digest; a release bundles only pinned images", img.Source)
+	}
+	// manifest checks the bytes against the pinned digest.
+	body, mt, err := s.manifest(ctx, sr, sr.Digest)
+	if err != nil {
+		return nil, fmt.Errorf("imagepush: %s: %w", sr, err)
+	}
+	if isIndexType(mt) {
+		d, err := s.pick(body)
+		if err != nil {
+			return nil, fmt.Errorf("imagepush: %s: %w", sr, err)
+		}
+		if body, mt, err = s.manifest(ctx, sr, d); err != nil {
+			return nil, fmt.Errorf("imagepush: %s: %w", sr, err)
+		}
+	}
+	if !isManifestType(mt) {
+		return nil, fmt.Errorf("imagepush: %s: unsupported manifest type %q", sr, mt)
+	}
+	m, err := parseManifest(body, mt)
+	if err != nil {
+		return nil, fmt.Errorf("imagepush: %s: %w", sr, err)
+	}
+	rc, err := s.blob(ctx, sr, m.Config.Digest)
+	if err != nil {
+		return nil, fmt.Errorf("imagepush: %s: config: %w", sr, err)
+	}
+	config, err := io.ReadAll(io.LimitReader(rc, maxManifestBytes+1))
+	rc.Close()
+	if err != nil {
+		return nil, fmt.Errorf("imagepush: %s: config: %w", sr, err)
+	}
+	if digestOf(config) != m.Config.Digest || int64(len(config)) != m.Config.Size {
+		return nil, fmt.Errorf("imagepush: %s: config does not match %s", sr, m.Config.Digest)
+	}
+	return &resolvedImage{BundleImage: img, mediaType: mt, body: body, m: m, config: config,
+		open: func(ctx context.Context, d descriptor) (io.ReadCloser, error) {
+			return s.blob(ctx, sr, d.Digest)
+		}}, nil
+}

internal/imagepush/bundle_test.go

@@ -0,0 +1,344 @@
+package imagepush
+
+import (
+	"archive/tar"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"felis.lolicon.best/internal/registrygate"
+)
+
+// layoutBuilder writes OCI layout tars the way buildx's oci exporter does.
+type layoutBuilder struct {
+	blobs map[string][]byte
+	order []string
+}
+
+func newLayoutBuilder() *layoutBuilder { return &layoutBuilder{blobs: map[string][]byte{}} }
+
+func (b *layoutBuilder) add(body []byte) descriptor {
+	d := digestOf(body)
+	if _, ok := b.blobs[d]; !ok {
+		b.order = append(b.order, d)
+	}
+	b.blobs[d] = body
+	return descriptor{MediaType: mediaOCILayerGz, Size: int64(len(body)), Digest: d}
+}
+
+// image stores one platform's manifest and returns its descriptor.
+func (b *layoutBuilder) image(arch string, layers ...string) layoutDescriptor {
+	cfg := b.add([]byte(`{"architecture":"` + arch + `","os":"linux","rootfs":{"type":"layers"}}`))
+	cfg.MediaType = mediaOCIConfig
+	m := manifest{SchemaVersion: 2, MediaType: mediaOCIManifest, Config: cfg}
+	for _, l := range layers {
+		m.Layers = append(m.Layers, b.add([]byte(l)))
+	}
+	body, _ := json.Marshal(m)
+	d := b.add(body)
+	return layoutDescriptor{MediaType: mediaOCIManifest, Digest: d.Digest, Size: d.Size}
+}
+
+// index stores a nested index over the given entries.
+func (b *layoutBuilder) index(entries ...layoutDescriptor) layoutDescriptor {
+	body, _ := json.Marshal(layoutIndex{SchemaVersion: 2, MediaType: mediaOCIIndex, Manifests: entries})
+	d := b.add(body)
+	return layoutDescriptor{MediaType: mediaOCIIndex, Digest: d.Digest, Size: d.Size}
+}
+
+func (b *layoutBuilder) write(t *testing.T, top ...layoutDescriptor) string {
+	t.Helper()
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	add := func(name string, body []byte) {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(body)), Typeflag: tar.TypeReg}); err != nil {
+			t.Fatal(err)
+		}
+		tw.Write(body)
+	}
+	add(layoutMarkerFile, []byte(layoutMarkerContent))
+	idx, _ := json.Marshal(layoutIndex{SchemaVersion: 2, MediaType: mediaOCIIndex, Manifests: top})
+	add(layoutIndexFile, idx)
+	for _, d := range b.order {
+		add(blobPath(d), b.blobs[d])
+	}
+	tw.Close()
+	path := filepath.Join(t.TempDir(), "layout.tar")
+	if err := os.WriteFile(path, buf.Bytes(), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}
+
+// readTar returns every regular file in a tar, and fails on a name written twice.
+func readTar(t *testing.T, r io.Reader) map[string][]byte {
+	t.Helper()
+	files := map[string][]byte{}
+	tr := tar.NewReader(r)
+	for {
+		h, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			return files
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+		if h.Typeflag != tar.TypeReg {
+			continue
+		}
+		if _, dup := files[h.Name]; dup {
+			t.Errorf("%s is written twice", h.Name)
+		}
+		files[h.Name], _ = io.ReadAll(tr)
+	}
+}
+
+func TestBundleCarriesOnePlatformAndPushesByteForByte(t *testing.T) {
+	// The control-plane image the way buildx leaves it with provenance on: an index
+	// over the image and an attestation manifest, beside another architecture.
+	lb := newLayoutBuilder()
+	arm := lb.image("arm64", "shared base", "felis binary")
+	amd := lb.image("amd64", "amd64 base", "amd64 binary")
+	att := lb.image("unknown", "provenance")
+	att.Annotations = map[string]string{"vnd.docker.reference.type": "attestation-manifest"}
+	att.Platform = &platformSpec{OS: "unknown", Architecture: "unknown"}
+	arm.Platform = &platformSpec{OS: "linux", Architecture: "arm64"}
+	amd.Platform = &platformSpec{OS: "linux", Architecture: "amd64"}
+	felisLayout := lb.write(t, lb.index(amd, att, arm))
+
+	// A game image built alone: one manifest, no platform field, sharing a base layer.
+	lb2 := newLayoutBuilder()
+	limbo := lb2.image("arm64", "shared base", "limbo jar")
+	limboLayout := lb2.write(t, limbo)
+
+	src := newFakeSource(t)
+	idx, srcArm := src.addIndex("2.8.3")
+	pinned := src.host() + "/tools/thing:2.8.3@" + idx
+
+	var out bytes.Buffer
+	s := &Source{Scheme: "http", Platform: "linux/arm64"}
+	entries, err := WriteBundle(context.Background(), s, []BundleImage{
+		{Role: "felis", Name: "registry.felis.svc:5000/felis/felis:v1.2.3", Layout: felisLayout},
+		{Role: "limbo", Name: "registry.felis.svc:5000/felis/limbo:demo", Layout: limboLayout},
+		{Role: "registry", Name: PinnedName(pinned), Source: pinned},
+	}, &out)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := map[string]string{"felis": arm.Digest, "limbo": limbo.Digest, "registry": srcArm}
+	if len(entries) != 3 {
+		t.Fatalf("entries = %+v", entries)
+	}
+	for _, e := range entries {
+		if e.Digest != want[e.Role] {
+			t.Errorf("%s: digest %s, want the arm64 manifest %s", e.Role, e.Digest, want[e.Role])
+		}
+	}
+	if entries[2].Name != src.host()+"/tools/thing@"+idx {
+		t.Errorf("the pulled image is named %s, want repository@index-digest, the name CRI looks the pinned ref up by", entries[2].Name)
+	}
+
+	files := readTar(t, bytes.NewReader(out.Bytes()))
+	if string(files[layoutMarkerFile]) != layoutMarkerContent {
+		t.Errorf("oci-layout = %q", files[layoutMarkerFile])
+	}
+	var index layoutIndex
+	if err := json.Unmarshal(files[layoutIndexFile], &index); err != nil {
+		t.Fatal(err)
+	}
+	names := map[string]layoutDescriptor{}
+	for _, m := range index.Manifests {
+		if m.Platform != nil || m.MediaType != mediaOCIManifest {
+			t.Errorf("index entry %+v must point straight at a manifest, with no platform", m)
+		}
+		names[m.Annotations[annotationImageName]] = m
+	}
+	for name, digest := range map[string]string{
+		"registry.felis.svc:5000/felis/felis:v1.2.3":          arm.Digest,
+		"registry.felis.svc:5000/felis/felis@" + arm.Digest:   arm.Digest,
+		"registry.felis.svc:5000/felis/limbo:demo":            limbo.Digest,
+		"registry.felis.svc:5000/felis/limbo@" + limbo.Digest: limbo.Digest,
+		src.host() + "/tools/thing@" + idx:                    srcArm,
+	} {
+		if names[name].Digest != digest {
+			t.Errorf("%s -> %q, want %s", name, names[name].Digest, digest)
+		}
+	}
+	if len(names) != 5 {
+		t.Errorf("index names %d images, want 5: %v", len(names), names)
+	}
+	if got := names["registry.felis.svc:5000/felis/limbo:demo"].Annotations[annotationRefName]; got != "demo" {
+		t.Errorf("ref.name = %q, want the tag", got)
+	}
+
+	// Every blob an entry needs is in the tar and hashes to its name; nothing from
+	// the other architecture or the attestation came along.
+	need := map[string]bool{}
+	for _, m := range index.Manifests {
+		body := files[blobPath(m.Digest)]
+		if digestOf(body) != m.Digest {
+			t.Fatalf("manifest %s missing or corrupt", m.Digest)
+		}
+		var mf manifest
+		json.Unmarshal(body, &mf)
+		need[m.Digest] = true
+		for _, d := range append([]descriptor{mf.Config}, mf.Layers...) {
+			need[d.Digest] = true
+			if digestOf(files[blobPath(d.Digest)]) != d.Digest {
+				t.Errorf("blob %s missing or corrupt", d.Digest)
+			}
+		}
+	}
+	for name := range files {
+		if strings.HasPrefix(name, "blobs/") && !need["sha256:"+strings.TrimPrefix(name, "blobs/sha256/")] {
+			t.Errorf("%s is in the bundle but no image uses it", name)
+		}
+	}
+
+	// The same bytes again give the same bundle.
+	var again bytes.Buffer
+	if _, err := WriteBundle(context.Background(), s, []BundleImage{
+		{Role: "felis", Name: "registry.felis.svc:5000/felis/felis:v1.2.3", Layout: felisLayout},
+		{Role: "limbo", Name: "registry.felis.svc:5000/felis/limbo:demo", Layout: limboLayout},
+		{Role: "registry", Name: PinnedName(pinned), Source: pinned},
+	}, &again); err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(out.Bytes(), again.Bytes()) {
+		t.Error("two runs over the same images wrote different bundles")
+	}
+	// Both runs above fall in the same second; a rebuild of the release a day later
+	// must write the same bytes too, so no header carries the time it was written.
+	tr := tar.NewReader(bytes.NewReader(out.Bytes()))
+	for {
+		h, err := tr.Next()
+		if err != nil {
+			break
+		}
+		if !h.ModTime.Equal(time.Unix(0, 0)) {
+			t.Errorf("%s is stamped %v", h.Name, h.ModTime)
+		}
+	}
+
+	// Pushed from the bundle, the registry records the manifest containerd imported.
+	bundle := filepath.Join(t.TempDir(), "bundle.tar")
+	os.WriteFile(bundle, out.Bytes(), 0o644)
+	reg, host := startStack(t)
+	p := &Pusher{Scheme: "http", Username: registrygate.PrincipalPlatform, Password: "plat-secret", Attempts: 1}
+	for _, tc := range []struct{ name, repo, digest string }{
+		{"registry.felis.svc:5000/felis/limbo:demo", "felis/limbo", limbo.Digest},
+		{src.host() + "/tools/thing@" + idx, "felis/thing", srcArm},
+	} {
+		got, err := p.PushLayout(context.Background(), bundle, tc.name, host+"/"+tc.repo+":demo")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != tc.digest {
+			t.Errorf("pushed %s as %s, want %s", tc.name, got, tc.digest)
+		}
+		if !bytes.Equal(reg.manifests[tc.repo+":demo"], files[blobPath(tc.digest)]) {
+			t.Errorf("%s: the registry's manifest differs from the bundle's bytes", tc.repo)
+		}
+		if reg.types[tc.repo+":demo"] != mediaOCIManifest {
+			t.Errorf("%s: pushed as %q", tc.repo, reg.types[tc.repo+":demo"])
+		}
+	}
+	puts := reg.puts
+	if _, err := p.PushLayout(context.Background(), bundle, "registry.felis.svc:5000/felis/limbo:demo", host+"/felis/limbo:demo"); err != nil {
+		t.Fatal(err)
+	}
+	if reg.puts != puts {
+		t.Errorf("a second push uploaded %d blobs the registry already held", reg.puts-puts)
+	}
+}
+
+func TestBundleRefusesAnotherArchitecturesImage(t *testing.T) {
+	lb := newLayoutBuilder()
+	layout := lb.write(t, lb.image("amd64", "layer"))
+	_, err := WriteBundle(context.Background(), &Source{Platform: "linux/arm64"},
+		[]BundleImage{{Role: "limbo", Name: "r.example:5000/felis/limbo:demo", Layout: layout}}, io.Discard)
+	if err == nil || !strings.Contains(err.Error(), "is a linux/amd64 image, the bundle is for linux/arm64") {
+		t.Fatalf("WriteBundle = %v, want the architecture refused", err)
+	}
+}
+
+func TestBundleRefusesANonImage(t *testing.T) {
+	// An OCI artifact manifest has an image manifest's shape but is no image: the
+	// installer's push would refuse it, so the release build must refuse it first.
+	lb := newLayoutBuilder()
+	img := lb.image("arm64", "layer")
+	var mf manifest
+	json.Unmarshal(lb.blobs[img.Digest], &mf)
+	mf.MediaType = ""
+	body, _ := json.Marshal(mf)
+	d := lb.add(body)
+	layout := lb.write(t, layoutDescriptor{MediaType: "application/vnd.oci.artifact.manifest.v1+json", Digest: d.Digest, Size: d.Size})
+	_, err := WriteBundle(context.Background(), &Source{Platform: "linux/arm64"},
+		[]BundleImage{{Role: "limbo", Name: "r.example:5000/felis/limbo:demo", Layout: layout}}, io.Discard)
+	if err == nil || !strings.Contains(err.Error(), "want an image") {
+		t.Fatalf("WriteBundle = %v, want the artifact refused", err)
+	}
+}
+
+func TestBundleRefusesATamperedBlob(t *testing.T) {
+	for swapped, want := range map[string]string{
+		"the fake layer":           "holds sha256:",
+		"the real layer, and more": "is longer than its 14 bytes",
+		"the real":                 "(8 bytes)",
+	} {
+		lb := newLayoutBuilder()
+		img := lb.image("arm64", "the real layer")
+		var mf manifest
+		json.Unmarshal(lb.blobs[img.Digest], &mf)
+		lb.blobs[mf.Layers[0].Digest] = []byte(swapped)
+		layout := lb.write(t, img)
+		_, err := WriteBundle(context.Background(), &Source{Platform: "linux/arm64"},
+			[]BundleImage{{Role: "limbo", Name: "r.example:5000/felis/limbo:demo", Layout: layout}}, io.Discard)
+		if err == nil || !strings.Contains(err.Error(), want) {
+			t.Errorf("layer swapped for %q: WriteBundle = %v, want %q", swapped, err, want)
+		}
+	}
+}
+
+func TestBundleRefusesAnUnpinnedSource(t *testing.T) {
+	src := newFakeSource(t)
+	src.addIndex("2.8.3")
+	_, err := WriteBundle(context.Background(), &Source{Scheme: "http", Platform: "linux/arm64"},
+		[]BundleImage{{Role: "registry", Name: "x", Source: src.host() + "/tools/thing:2.8.3"}}, io.Discard)
+	if err == nil || !strings.Contains(err.Error(), "not pinned by digest") {
+		t.Fatalf("WriteBundle = %v, want a tag-only source refused", err)
+	}
+}
+
+func TestPushLayoutNamesWhatTheBundleHolds(t *testing.T) {
+	lb := newLayoutBuilder()
+	img := lb.image("arm64", "layer")
+	img.Annotations = map[string]string{annotationImageName: "r.example:5000/felis/limbo:demo"}
+	layout := lb.write(t, img)
+	_, host := startStack(t)
+	p := &Pusher{Scheme: "http", Username: registrygate.PrincipalPlatform, Password: "plat-secret", Attempts: 1}
+	_, err := p.PushLayout(context.Background(), layout, "r.example:5000/felis/lobby:demo", host+"/felis/lobby:demo")
+	if err == nil || !strings.Contains(err.Error(), "holds no image named r.example:5000/felis/lobby:demo (it holds: r.example:5000/felis/limbo:demo)") {
+		t.Fatalf("PushLayout = %v, want the missing name reported with what is there", err)
+	}
+}
+
+func TestPinnedName(t *testing.T) {
+	for in, want := range map[string]string{
+		"docker.io/library/registry:2.8.3@sha256:ab": "docker.io/library/registry@sha256:ab",
+		"host:5000/a/b:tag@sha256:cd":                "host:5000/a/b@sha256:cd",
+		"host:5000/a/b@sha256:ef":                    "host:5000/a/b@sha256:ef",
+	} {
+		if got := PinnedName(in); got != want {
+			t.Errorf("PinnedName(%q) = %q, want %q", in, got, want)
+		}
+	}
+}

internal/imagepush/layout.go

@@ -0,0 +1,184 @@
+package imagepush
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"sort"
+	"strings"
+)
+
+// An OCI image layout tar is what a release ships its images in: oci-layout,
+// blobs/sha256/<hex> and an index.json whose entries each name one image through
+// the io.containerd.image.name annotation. `ctr images import` reads that
+// annotation, so a host imports the images straight into k3s's containerd under
+// the names the pods use, and PushLayout pushes the same bytes into the platform
+// registry: the manifest goes up verbatim, so the registry and containerd agree on
+// every digest.
+
+const (
+	annotationImageName = "io.containerd.image.name"
+	annotationRefName   = "org.opencontainers.image.ref.name"
+	layoutIndexFile     = "index.json"
+	layoutMarkerFile    = "oci-layout"
+	layoutMarkerContent = `{"imageLayoutVersion":"1.0.0"}`
+)
+
+// layoutDescriptor is one entry of an index: index.json's or a nested index's.
+type layoutDescriptor struct {
+	MediaType   string            `json:"mediaType"`
+	Digest      string            `json:"digest"`
+	Size        int64             `json:"size"`
+	Annotations map[string]string `json:"annotations,omitempty"`
+	Platform    *platformSpec     `json:"platform,omitempty"`
+}
+
+type platformSpec struct {
+	OS           string `json:"os"`
+	Architecture string `json:"architecture"`
+	Variant      string `json:"variant,omitempty"`
+}
+
+type layoutIndex struct {
+	SchemaVersion int                `json:"schemaVersion"`
+	MediaType     string             `json:"mediaType,omitempty"`
+	Manifests     []layoutDescriptor `json:"manifests"`
+}
+
+// blobPath is where a layout keeps the blob with this digest.
+func blobPath(digest string) string {
+	return "blobs/sha256/" + strings.TrimPrefix(digest, "sha256:")
+}
+
+func isManifestType(mt string) bool { return mt == mediaOCIManifest || mt == mediaDockerManifest }
+func isIndexType(mt string) bool    { return mt == mediaOCIIndex || mt == mediaDockerList }
+
+// readLayoutIndex reads a layout tar's index.json.
+func readLayoutIndex(tarPath string) (*layoutIndex, error) {
+	raw, err := readEntry(tarPath, layoutIndexFile, maxManifestBytes)
+	if err != nil {
+		return nil, err
+	}
+	var idx layoutIndex
+	if err := json.Unmarshal(raw, &idx); err != nil {
+		return nil, fmt.Errorf("imagepush: %s: %s: %w", tarPath, layoutIndexFile, err)
+	}
+	return &idx, nil
+}
+
+// readLayoutBlob reads a small blob (a manifest, an index, a config) out of a layout
+// tar and checks it against its descriptor.
+func readLayoutBlob(tarPath string, d layoutDescriptor) ([]byte, error) {
+	if !sha256DigestRE.MatchString(d.Digest) {
+		return nil, fmt.Errorf("imagepush: %s: bad digest %q", tarPath, d.Digest)
+	}
+	if d.Size < 0 || d.Size > maxManifestBytes {
+		return nil, fmt.Errorf("imagepush: %s: blob %s has size %d", tarPath, d.Digest, d.Size)
+	}
+	body, err := readEntry(tarPath, blobPath(d.Digest), maxManifestBytes)
+	if err != nil {
+		return nil, err
+	}
+	if got := digestOf(body); got != d.Digest || int64(len(body)) != d.Size {
+		return nil, fmt.Errorf("imagepush: %s: blob %s (%d bytes) holds %s (%d bytes)", tarPath, d.Digest, d.Size, got, len(body))
+	}
+	return body, nil
+}
+
+// PushLayout uploads the image the OCI layout tar at tarPath names name (its
+// io.containerd.image.name) as ref, and returns the manifest digest the registry
+// recorded: the digest of the manifest in the tar, since it is pushed byte for byte.
+func (p *Pusher) PushLayout(ctx context.Context, tarPath, name, ref string) (string, error) {
+	r, err := ParseRef(ref)
+	if err != nil {
+		return "", err
+	}
+	idx, err := readLayoutIndex(tarPath)
+	if err != nil {
+		return "", err
+	}
+	var (
+		desc  layoutDescriptor
+		found int
+		names []string
+	)
+	for _, m := range idx.Manifests {
+		n := m.Annotations[annotationImageName]
+		names = append(names, n)
+		if n == name {
+			desc = m
+			found++
+		}
+	}
+	switch {
+	case found == 0:
+		sort.Strings(names)
+		return "", fmt.Errorf("imagepush: %s holds no image named %s (it holds: %s)", tarPath, name, strings.Join(names, ", "))
+	case found > 1:
+		return "", fmt.Errorf("imagepush: %s names %d images %s", tarPath, found, name)
+	}
+	// A bundle entry points straight at one platform's manifest: that is what makes
+	// the pushed digest the one containerd imported.
+	if !isManifestType(desc.MediaType) {
+		return "", fmt.Errorf("imagepush: %s: %s is a %q, want an image manifest", tarPath, name, desc.MediaType)
+	}
+	body, err := readLayoutBlob(tarPath, desc)
+	if err != nil {
+		return "", err
+	}
+	m, err := parseManifest(body, desc.MediaType)
+	if err != nil {
+		return "", fmt.Errorf("imagepush: %s: %s: %w", tarPath, name, err)
+	}
+	blobs := append([]descriptor{m.Config}, m.Layers...)
+	for i, b := range blobs {
+		err := p.retry(ctx, func() error {
+			return p.uploadBlob(ctx, r, b.Digest, b.Size, func() (io.ReadCloser, error) {
+				f, entry, err := openEntry(tarPath, blobPath(b.Digest))
+				if err != nil {
+					return nil, err
+				}
+				return struct {
+					io.Reader
+					io.Closer
+				}{entry, f}, nil
+			})
+		})
+		if err != nil {
+			return "", fmt.Errorf("imagepush: %s: blob %d/%d (%s): %w", name, i+1, len(blobs), b.Digest, err)
+		}
+	}
+	var digest string
+	err = p.retry(ctx, func() error {
+		d, err := p.putManifest(ctx, r, desc.MediaType, body)
+		digest = d
+		return err
+	})
+	if err != nil {
+		return "", fmt.Errorf("imagepush: %s: manifest: %w", r, err)
+	}
+	p.logf("pushed %s as %s@%s", name, r, digest)
+	return digest, nil
+}
+
+// parseManifest reads an image manifest's config and layers and checks each is a
+// well-formed descriptor. A mediaType field in the body must agree with mt.
+func parseManifest(body []byte, mt string) (*manifest, error) {
+	var m manifest
+	if err := json.Unmarshal(body, &m); err != nil {
+		return nil, fmt.Errorf("manifest: %w", err)
+	}
+	if m.MediaType != "" && m.MediaType != mt {
+		return nil, fmt.Errorf("manifest says it is a %q, its descriptor a %q", m.MediaType, mt)
+	}
+	if len(m.Layers) == 0 {
+		return nil, fmt.Errorf("manifest has no layers")
+	}
+	for i, b := range append([]descriptor{m.Config}, m.Layers...) {
+		if !sha256DigestRE.MatchString(b.Digest) || b.Size < 0 {
+			return nil, fmt.Errorf("blob %d has digest %q size %d", i+1, b.Digest, b.Size)
+		}
+	}
+	return &m, nil
+}