SBOM support in "cosign attach" and "cosign download sbom". (#387)

This is ready!

Signed-off-by: Dan Lorenc <dlorenc@google.com>

cmd/cosign/cli/attach/attach.go

@@ -32,7 +32,7 @@ func Attach() *ffcli.Command {
 		ShortUsage:  "cosign attach",
 		ShortHelp:   "attach contains tools to attach artifacts to other artifacts in a registry",
 		FlagSet:     flagset,
-		Subcommands: []*ffcli.Command{Signature()},
+		Subcommands: []*ffcli.Command{Signature(), SBOM()},
 		Exec: func(ctx context.Context, args []string) error {
 			return flag.ErrHelp
 		},

cmd/cosign/cli/attach/sbom.go

@@ -0,0 +1,112 @@
+//
+// Copyright 2021 The Sigstore Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package attach
+
+import (
+	"context"
+	"flag"
+	"io/ioutil"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/empty"
+	"github.com/google/go-containerregistry/pkg/v1/mutate"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+	"github.com/peterbourgon/ff/v3/ffcli"
+
+	"github.com/sigstore/cosign/pkg/cosign"
+	cremote "github.com/sigstore/cosign/pkg/cosign/remote"
+)
+
+var mediaTypes = map[string]string{
+	"cyclonedx": "application/vnd.cyclonedx",
+	"spdx":      "text/spdx",
+}
+
+func SBOM() *ffcli.Command {
+	var (
+		flagset  = flag.NewFlagSet("cosign attach sbom", flag.ExitOnError)
+		sbom     = flagset.String("sbom", "", "path to the sbom, or {-} for stdin")
+		sbomType = flagset.String("type", "spdx", "type of sbom (spdx|cyclonedx), default spdx")
+	)
+	return &ffcli.Command{
+		Name:       "sbom",
+		ShortUsage: "cosign attach sbom <image uri>",
+		ShortHelp:  "attach sbom to the supplied container image",
+		FlagSet:    flagset,
+		Exec: func(ctx context.Context, args []string) error {
+			if len(args) != 1 {
+				return flag.ErrHelp
+			}
+
+			mt, ok := mediaTypes[*sbomType]
+			if !ok {
+				return flag.ErrHelp
+			}
+
+			return SBOMCmd(ctx, *sbom, mt, args[0])
+		},
+	}
+}
+
+func SBOMCmd(ctx context.Context, sbomRef, sbomType, imageRef string) error {
+
+	ref, err := name.ParseReference(imageRef)
+	if err != nil {
+		return err
+	}
+
+	b, err := ioutil.ReadFile(sbomRef)
+	if err != nil {
+		return err
+	}
+	s := &cremote.StaticLayer{
+		B:  b,
+		Mt: types.MediaType(sbomType),
+	}
+
+	img := mutate.MediaType(empty.Image, types.OCIManifestSchema1)
+	img, err = mutate.Append(img, mutate.Addendum{
+		Layer: s,
+	})
+	if err != nil {
+		return err
+	}
+
+	// This doesn't work on DockerHub
+	m, err := img.Manifest()
+	if err != nil {
+		return err
+	}
+	// Setting it to an artifact type doesn't work on media types
+	m.Config.MediaType = types.OCIConfigJSON
+
+	auth := remote.WithAuthFromKeychain(authn.DefaultKeychain)
+
+	get, err := remote.Get(ref, auth)
+	if err != nil {
+		return err
+	}
+	repo := ref.Context()
+
+	dstRef := cosign.AttachedImageTag(repo, get, cosign.SuffixSBOM)
+
+	if err := remote.Write(dstRef, img, remote.WithAuthFromKeychain(authn.DefaultKeychain)); err != nil {
+		return err
+	}
+	return nil
+}

cmd/cosign/cli/download/download.go

@@ -32,7 +32,7 @@ func Download() *ffcli.Command {
 		ShortUsage:  "cosign download",
 		ShortHelp:   "download contains tools to download artifacts and attached artifacts in a registry",
 		FlagSet:     flagset,
-		Subcommands: []*ffcli.Command{Signature()},
+		Subcommands: []*ffcli.Command{Signature(), SBOM()},
 		Exec: func(ctx context.Context, args []string) error {
 			return flag.ErrHelp
 		},

cmd/cosign/cli/download/sbom.go

@@ -0,0 +1,90 @@
+//
+// Copyright 2021 The Sigstore Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package download
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"github.com/sigstore/cosign/pkg/cosign"
+)
+
+func SBOM() *ffcli.Command {
+	var (
+		flagset = flag.NewFlagSet("cosign download sbom", flag.ExitOnError)
+	)
+	return &ffcli.Command{
+		Name:       "sbom",
+		ShortUsage: "cosign download sbom <image uri>",
+		ShortHelp:  "Download SBOMs from the supplied container image",
+		FlagSet:    flagset,
+		Exec: func(ctx context.Context, args []string) error {
+			if len(args) != 1 {
+				return flag.ErrHelp
+			}
+			return SBOMCmd(ctx, args[0])
+		},
+	}
+}
+
+func SBOMCmd(ctx context.Context, imageRef string) error {
+	ref, err := name.ParseReference(imageRef)
+	if err != nil {
+		return err
+	}
+
+	auth := remote.WithAuthFromKeychain(authn.DefaultKeychain)
+
+	get, err := remote.Get(ref, auth)
+	if err != nil {
+		return err
+	}
+
+	repo := ref.Context()
+	dstRef := cosign.AttachedImageTag(repo, get, cosign.SuffixSBOM)
+	img, err := remote.Image(dstRef, remote.WithAuthFromKeychain(authn.DefaultKeychain))
+	if err != nil {
+		return err
+	}
+	layers, err := img.Layers()
+	if err != nil {
+		return err
+	}
+	for _, l := range layers {
+		mt, err := l.MediaType()
+		if err != nil {
+			return err
+		}
+		fmt.Fprintf(os.Stderr, "Found SBOM of media type: %s\n", mt)
+		r, err := l.Compressed()
+		if err != nil {
+			return err
+		}
+		sbom, err := ioutil.ReadAll(r)
+		if err != nil {
+			return err
+		}
+		fmt.Println(string(sbom))
+	}
+	return nil
+}

pkg/cosign/fetch.go

@@ -51,12 +51,13 @@ type SignedPayload struct {
 
 const (
 	SuffixSignature = ".sig"
+	SuffixSBOM      = ".sbom"
 )
 
-func AttachedImageTag(sigRepo name.Repository, signedImgDesc *remote.Descriptor, suffix string) name.Tag {
+func AttachedImageTag(repo name.Repository, imgDesc *remote.Descriptor, suffix string) name.Tag {
 	// sha256:d34db33f -> sha256-d34db33f.sig
-	tagStr := strings.ReplaceAll(signedImgDesc.Digest.String(), ":", "-") + suffix
-	return sigRepo.Tag(tagStr)
+	tagStr := strings.ReplaceAll(imgDesc.Digest.String(), ":", "-") + suffix
+	return repo.Tag(tagStr)
 }
 
 func GetAttachedManifestForImage(imgDesc *remote.Descriptor, repo name.Repository, suffix string, opts ...remote.Option) (*remote.Descriptor, error) {