implement cosign copy (#317)

Signed-off-by: Jake Sanders <jsand@google.com>

cmd/cosign/cli/copy.go

@@ -0,0 +1,127 @@
+// 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 cli
+
+import (
+	"context"
+	"flag"
+	"fmt"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"github.com/sigstore/cosign/pkg/cosign"
+)
+
+func Copy() *ffcli.Command {
+	var (
+		flagset     = flag.NewFlagSet("cosign copy", flag.ExitOnError)
+		sigOnlyFlag = flagset.Bool("sig-only", false, "only copy the image signature")
+		forceFlag   = flagset.Bool("f", false, "overwrite destination image(s), if necessary")
+	)
+	return &ffcli.Command{
+		Name:       "copy",
+		ShortUsage: "cosign copy <source image> <destination image>",
+		ShortHelp:  `Copy the supplied container image and signatures.`,
+		LongHelp: `Copy the supplied container image and signatures.
+
+EXAMPLES
+  # copy a container image and its signatures
+  cosign copy example.com/src:latest example.com/dest:latest
+
+  # copy the signatures only
+  cosign copy -sig-only example.com/src example.com/dest
+
+  # overwrite destination image and signatures
+  cosign copy -f example.com/src example.com/dest
+  `,
+		FlagSet: flagset,
+		Exec: func(ctx context.Context, args []string) error {
+			if len(args) != 2 {
+				return flag.ErrHelp
+			}
+			return CopyCmd(ctx, args[0], args[1], *sigOnlyFlag, *forceFlag)
+		},
+	}
+}
+
+func CopyCmd(ctx context.Context, srcImg, dstImg string, sigOnly, force bool) error {
+	remoteAuth := remote.WithAuthFromKeychain(authn.DefaultKeychain)
+
+	srcRef, err := name.ParseReference(srcImg)
+	if err != nil {
+		return err
+	}
+	dstRef, err := name.ParseReference(dstImg)
+	if err != nil {
+		return err
+	}
+
+	gotSrc, err := remote.Get(srcRef, remoteAuth)
+	if err != nil {
+		return err
+	}
+
+	sigSrcRef, err := cosign.DestinationRef(srcRef, gotSrc)
+	if err != nil {
+		return err
+	}
+
+	dstRepoRef := dstRef.Context()
+	sigDstRef := dstRepoRef.Tag(sigSrcRef.Identifier())
+
+	if err := copyImage(sigSrcRef, sigDstRef, force, remoteAuth); err != nil {
+		return err
+	}
+
+	if !sigOnly {
+		if err := copyImage(srcRef, dstRef, force, remoteAuth); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func descriptorsEqual(a, b *v1.Descriptor) bool {
+	if a == nil || b == nil {
+		return a == nil && b == nil
+	}
+	return a.Digest == b.Digest
+}
+
+func copyImage(src, dest name.Reference, overwrite bool, opts ...remote.Option) error {
+	got, err := remote.Get(src, opts...)
+	if err != nil {
+		return err
+	}
+	img, err := got.Image()
+	if err != nil {
+		return err
+	}
+
+	if !overwrite {
+		if dstDesc, err := remote.Head(dest, opts...); err == nil {
+			if descriptorsEqual(&got.Descriptor, dstDesc) {
+				return nil
+			}
+			return fmt.Errorf("image %q already exists. Use `-f` to overwrite", dest.Name())
+		}
+	}
+
+	return remote.Write(dest, img, opts...)
+}

cmd/cosign/main.go

@@ -41,7 +41,7 @@ func main() {
 		FlagSet:    rootFlagSet,
 		Subcommands: []*ffcli.Command{
 			cli.Verify(), cli.Sign(), cli.Upload(), cli.Generate(), cli.Download(), cli.GenerateKeyPair(), cli.SignBlob(),
-			cli.VerifyBlob(), cli.Triangulate(), cli.Version(), cli.PublicKey(), pivcli.PivKey()},
+			cli.VerifyBlob(), cli.Triangulate(), cli.Version(), cli.PublicKey(), pivcli.PivKey(), cli.Copy()},
 		Exec: func(context.Context, []string) error {
 			return flag.ErrHelp
 		},

test/e2e_test_secrets.sh

@@ -32,17 +32,23 @@ export COSIGN_PASSWORD=$pass
 img="us-central1-docker.pkg.dev/projectsigstore/cosign-ci/test"
 img2="us-central1-docker.pkg.dev/projectsigstore/cosign-ci/test-2"
 legacy_img="us-central1-docker.pkg.dev/projectsigstore/cosign-ci/legacy-test"
+img_copy="${img}/copy"
 for image in $img $img2 $legacy_img
 do
     (crane delete $(./cosign triangulate $image)) || true
     crane cp busybox $image
 done
+crane ls $img_copy | while read tag ; do crane delete $tag ; done
 
 
 ## sign/verify
 ./cosign sign -key cosign.key $img
 ./cosign verify -key cosign.pub $img
 
+# copy
+./cosign copy -source $img -destination $img_copy
+./cosign verify -key cosign.pub $img_copy
+
 ## confirm use of OCI media type in signature image
 crane manifest $(./cosign triangulate $img) | grep -q "application/vnd.oci.image.config.v1+json"