835 - Keyless Support for SBOM Attestations (anchore#910)

Co-authored-by: Alex Goodman <alex.goodman@anchore.com>

cmd/syft/cli/attest.go

@@ -8,6 +8,7 @@ import (
 	"github.com/anchore/syft/cmd/syft/cli/options"
 	"github.com/anchore/syft/internal"
 	"github.com/anchore/syft/internal/config"
+	"github.com/sigstore/cosign/cmd/cosign/cli/sign"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 )
@@ -53,7 +54,19 @@ func Attest(v *viper.Viper, app *config.Application, ro *options.RootOptions) *c
 				checkForApplicationUpdate()
 			}
 
-			return attest.Run(cmd.Context(), app, args)
+			// build cosign key options for attestation
+			ko := sign.KeyOpts{
+				KeyRef:                   app.Attest.KeyRef,
+				FulcioURL:                app.Attest.FulcioURL,
+				IDToken:                  app.Attest.FulcioIdentityToken,
+				InsecureSkipFulcioVerify: app.Attest.InsecureSkipFulcioVerify,
+				RekorURL:                 app.Attest.RekorURL,
+				OIDCIssuer:               app.Attest.OIDCIssuer,
+				OIDCClientID:             app.Attest.OIDCClientID,
+				OIDCRedirectURL:          app.Attest.OIDCRedirectURL,
+			}
+
+			return attest.Run(cmd.Context(), app, ko, args)
 		},
 	}
 

cmd/syft/cli/attest/attest.go

@@ -6,7 +6,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
-	"strings"
+
+	"github.com/wagoodman/go-progress"
 
 	"github.com/anchore/stereoscope"
 	"github.com/anchore/stereoscope/pkg/image"
@@ -18,15 +19,28 @@ import (
 	"github.com/anchore/syft/internal/formats/cyclonedxjson"
 	"github.com/anchore/syft/internal/formats/spdx22json"
 	"github.com/anchore/syft/internal/formats/syftjson"
+	"github.com/anchore/syft/internal/log"
 	"github.com/anchore/syft/internal/ui"
 	"github.com/anchore/syft/syft"
 	"github.com/anchore/syft/syft/event"
 	"github.com/anchore/syft/syft/sbom"
 	"github.com/anchore/syft/syft/source"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/in-toto/in-toto-golang/in_toto"
 	"github.com/pkg/errors"
+	"github.com/sigstore/cosign/cmd/cosign/cli/rekor"
 	"github.com/sigstore/cosign/cmd/cosign/cli/sign"
+	"github.com/sigstore/cosign/pkg/cosign"
 	"github.com/sigstore/cosign/pkg/cosign/attestation"
+	cbundle "github.com/sigstore/cosign/pkg/cosign/bundle"
+	"github.com/sigstore/cosign/pkg/oci/mutate"
+	ociremote "github.com/sigstore/cosign/pkg/oci/remote"
+	"github.com/sigstore/cosign/pkg/oci/static"
+	sigs "github.com/sigstore/cosign/pkg/signature"
+	"github.com/sigstore/cosign/pkg/types"
+	"github.com/sigstore/rekor/pkg/generated/client"
+	"github.com/sigstore/rekor/pkg/generated/models"
 	"github.com/sigstore/sigstore/pkg/signature/dsse"
 	"github.com/wagoodman/go-partybus"
 
@@ -43,7 +57,7 @@ var (
 	intotoJSONDsseType = `application/vnd.in-toto+json`
 )
 
-func Run(ctx context.Context, app *config.Application, args []string) error {
+func Run(ctx context.Context, app *config.Application, ko sign.KeyOpts, args []string) error {
 	// We cannot generate an attestation for more than one output
 	if len(app.Outputs) > 1 {
 		return fmt.Errorf("unable to generate attestation for more than one output")
@@ -59,17 +73,20 @@ func Run(ctx context.Context, app *config.Application, args []string) error {
 	format := syft.FormatByName(app.Outputs[0])
 	predicateType := formatPredicateType(format)
 	if predicateType == "" {
-		return fmt.Errorf("could not produce attestation predicate for given format: %q. Available formats: %+v", options.FormatAliases(format.ID()), options.FormatAliases(allowedAttestFormats...))
+		return fmt.Errorf(
+			"could not produce attestation predicate for given format: %q. Available formats: %+v",
+			options.FormatAliases(format.ID()),
+			options.FormatAliases(allowedAttestFormats...),
+		)
 	}
 
-	passFunc, err := selectPassFunc(app.Attest.Key, app.Attest.Password)
-	if err != nil {
-		return err
-	}
+	if app.Attest.KeyRef != "" {
+		passFunc, err := selectPassFunc(app.Attest.KeyRef, app.Attest.Password)
+		if err != nil {
+			return err
+		}
 
-	ko := sign.KeyOpts{
-		KeyRef:   app.Attest.Key,
-		PassFunc: passFunc,
+		ko.PassFunc = passFunc
 	}
 
 	sv, err := sign.SignerFromKeyOpts(ctx, "", "", ko)
@@ -144,7 +161,7 @@ func execWorker(app *config.Application, sourceInput source.Input, format sbom.F
 			return
 		}
 
-		err = generateAttestation(sbomBytes, src, sv, predicateType)
+		err = generateAttestation(app, sbomBytes, src, sv, predicateType)
 		if err != nil {
 			errs <- err
 			return
@@ -153,7 +170,7 @@ func execWorker(app *config.Application, sourceInput source.Input, format sbom.F
 	return errs
 }
 
-func generateAttestation(predicate []byte, src *source.Source, sv *sign.SignerVerifier, predicateType string) error {
+func generateAttestation(app *config.Application, predicate []byte, src *source.Source, sv *sign.SignerVerifier, predicateType string) error {
 	switch len(src.Image.Metadata.RepoDigests) {
 	case 0:
 		return fmt.Errorf("cannot generate attestation since no repo digests were found; make sure you're passing an OCI registry source for the attest command")
@@ -163,11 +180,22 @@ func generateAttestation(predicate []byte, src *source.Source, sv *sign.SignerVe
 	}
 
 	wrapped := dsse.WrapSigner(sv, intotoJSONDsseType)
+	ref, err := name.ParseReference(src.Metadata.ImageMetadata.UserInput)
+	if err != nil {
+		return err
+	}
+
+	digest, err := ociremote.ResolveDigest(ref)
+	if err != nil {
+		return err
+	}
+
+	h, _ := v1.NewHash(digest.Identifier())
 
 	sh, err := attestation.GenerateStatement(attestation.GenerateOpts{
 		Predicate: bytes.NewBuffer(predicate),
 		Type:      predicateType,
-		Digest:    findValidDigest(src.Image.Metadata.RepoDigests),
+		Digest:    h.Hex,
 	})
 	if err != nil {
 		return err
@@ -183,24 +211,107 @@ func generateAttestation(predicate []byte, src *source.Source, sv *sign.SignerVe
 		return errors.Wrap(err, "unable to sign SBOM")
 	}
 
+	// We want to give the option to not upload the generated attestation
+	// if passed or if the user is using local PKI
+	if app.Attest.NoUpload || app.Attest.KeyRef != "" {
+		bus.Publish(partybus.Event{
+			Type: event.Exit,
+			Value: func() error {
+				_, err := os.Stdout.Write(signedPayload)
+				return err
+			},
+		})
+		return nil
+	}
+
+	return uploadAttestation(app, signedPayload, digest, sv)
+}
+
+func trackUploadAttestation() (*progress.Stage, *progress.Manual) {
+	stage := &progress.Stage{}
+	prog := &progress.Manual{}
+
+	bus.Publish(partybus.Event{
+		Type: event.UploadAttestation,
+		Value: progress.StagedProgressable(&struct {
+			progress.Stager
+			progress.Progressable
+		}{
+			Stager:       stage,
+			Progressable: prog,
+		}),
+	})
+
+	return stage, prog
+}
+
+// uploads signed SBOM payload to Rekor transparency log along with key information;
+// returns a bundle for attestation annotations
+// rekor bundle includes a signed payload and rekor timestamp;
+// the bundle is then wrapped onto an OCI signed entity and uploaded to
+// the user's image's OCI registry repository as *.att
+func uploadAttestation(app *config.Application, signedPayload []byte, digest name.Digest, sv *sign.SignerVerifier) error {
+	// add application/vnd.dsse.envelope.v1+json as media type for other applications to decode attestation
+	opts := []static.Option{static.WithLayerMediaType(types.DssePayloadType)}
+	if sv.Cert != nil {
+		opts = append(opts, static.WithCertChain(sv.Cert, sv.Chain))
+	}
+
+	stage, prog := trackUploadAttestation()
+	defer prog.SetCompleted() // just in case we return early
+
+	prog.Total = 2
+	stage.Current = "uploading signing information to transparency log"
+
+	// uploads payload to Rekor transparency log along with key information;
+	// returns bundle for attesation annotations
+	// rekor bundle includes a signed payload and rekor timestamp;
+	// the bundle is then wrapped onto an OCI signed entity and uploaded to
+	// the user's image's OCI registry repository as *.att
+	bundle, err := uploadToTlog(context.TODO(), sv, app.Attest.RekorURL, func(r *client.Rekor, b []byte) (*models.LogEntryAnon, error) {
+		return cosign.TLogUploadInTotoAttestation(context.TODO(), r, signedPayload, b)
+	})
+	if err != nil {
+		return err
+	}
+
+	prog.N = 1
+	stage.Current = "uploading attestation to OCI registry"
+
+	// add bundle OCI attestation that is uploaded to
+	opts = append(opts, static.WithBundle(bundle))
+	sig, err := static.NewAttestation(signedPayload, opts...)
+	if err != nil {
+		return err
+	}
+
+	se, err := ociremote.SignedEntity(digest)
+	if err != nil {
+		return err
+	}
+
+	newSE, err := mutate.AttachAttestationToEntity(se, sig)
+	if err != nil {
+		return err
+	}
+
+	// Publish the attestations associated with this entity
+	err = ociremote.WriteAttestations(digest.Repository, newSE)
+	if err != nil {
+		return err
+	}
+
+	prog.SetCompleted()
+
 	bus.Publish(partybus.Event{
 		Type: event.Exit,
 		Value: func() error {
-			_, err := os.Stdout.Write(signedPayload)
-			return err
+			return nil
 		},
 	})
-
 	return nil
 }
 
-func findValidDigest(digests []string) string {
-	// since we are only using the OCI repo provider for this source we are safe that this is only 1 value
-	// see https://github.com/anchore/stereoscope/blob/25ebd49a842b5ac0a20c2e2b4b81335b64ad248c/pkg/image/oci/registry_provider.go#L57-L63
-	split := strings.Split(digests[0], "sha256:")
-	return split[1]
-}
-
 func formatPredicateType(format sbom.Format) string {
 	switch format.ID() {
 	case spdx22json.ID:
@@ -214,3 +325,33 @@ func formatPredicateType(format sbom.Format) string {
 		return ""
 	}
 }
+
+type tlogUploadFn func(*client.Rekor, []byte) (*models.LogEntryAnon, error)
+
+func uploadToTlog(ctx context.Context, sv *sign.SignerVerifier, rekorURL string, upload tlogUploadFn) (*cbundle.RekorBundle, error) {
+	var rekorBytes []byte
+	// Upload the cert or the public key, depending on what we have
+	if sv.Cert != nil {
+		rekorBytes = sv.Cert
+	} else {
+		pemBytes, err := sigs.PublicKeyPem(sv, signatureoptions.WithContext(ctx))
+		if err != nil {
+			return nil, err
+		}
+		rekorBytes = pemBytes
+	}
+
+	rekorClient, err := rekor.NewClient(rekorURL)
+	if err != nil {
+		return nil, err
+	}
+	entry, err := upload(rekorClient, rekorBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	if entry.LogIndex != nil {
+		log.Debugf("transparency log entry created with index: %v", *entry.LogIndex)
+	}
+	return cbundle.EntryToBundle(entry), nil
+}

cmd/syft/cli/options/attest.go

@@ -6,23 +6,72 @@ import (
 	"github.com/spf13/viper"
 )
 
+const defaultKeyFileName = "cosign.key"
+
 type AttestOptions struct {
-	Key string
+	Key       string
+	Cert      string
+	CertChain string
+	NoUpload  bool
+	Force     bool
+	Recursive bool
+
+	Rekor  RekorOptions
+	Fulcio FulcioOptions
+	OIDC   OIDCOptions
 }
 
 var _ Interface = (*AttestOptions)(nil)
 
 func (o *AttestOptions) AddFlags(cmd *cobra.Command, v *viper.Viper) error {
-	cmd.PersistentFlags().StringVarP(&o.Key, "key", "", "cosign.key",
+	if err := o.Rekor.AddFlags(cmd, v); err != nil {
+		return err
+	}
+	if err := o.Fulcio.AddFlags(cmd, v); err != nil {
+		return err
+	}
+	if err := o.OIDC.AddFlags(cmd, v); err != nil {
+		return err
+	}
+
+	cmd.Flags().StringVarP(&o.Key, "key", "", defaultKeyFileName,
 		"path to the private key file to use for attestation")
 
-	return bindAttestationConfigOptions(cmd.PersistentFlags(), v)
+	cmd.Flags().StringVarP(&o.Cert, "cert", "", "",
+		"path to the x.509 certificate in PEM format to include in the OCI Signature")
+
+	cmd.Flags().BoolVarP(&o.NoUpload, "no-upload", "", false,
+		"do not upload the generated attestation")
+
+	cmd.Flags().BoolVarP(&o.Force, "force", "", false,
+		"skip warnings and confirmations")
+
+	cmd.Flags().BoolVarP(&o.Recursive, "recursive", "", false,
+		"if a multi-arch image is specified, additionally sign each discrete image")
+
+	return bindAttestationConfigOptions(cmd.Flags(), v)
 }
 
 func bindAttestationConfigOptions(flags *pflag.FlagSet, v *viper.Viper) error {
 	if err := v.BindPFlag("attest.key", flags.Lookup("key")); err != nil {
 		return err
 	}
 
+	if err := v.BindPFlag("attest.cert", flags.Lookup("cert")); err != nil {
+		return err
+	}
+
+	if err := v.BindPFlag("attest.no-upload", flags.Lookup("no-upload")); err != nil {
+		return err
+	}
+
+	if err := v.BindPFlag("attest.force", flags.Lookup("force")); err != nil {
+		return err
+	}
+
+	if err := v.BindPFlag("attest.recursive", flags.Lookup("recursive")); err != nil {
+		return err
+	}
+
 	return nil
 }