restore attest command

Signed-off-by: Christopher Phillips <christopher.phillips@anchore.com>

cmd/syft/cli/attest.go

@@ -1 +1,61 @@
 package cli
+
+import (
+	"log"
+
+	"github.com/anchore/syft/cmd/syft/cli/attest"
+	"github.com/anchore/syft/cmd/syft/cli/options"
+	"github.com/anchore/syft/internal"
+	"github.com/anchore/syft/internal/config"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+const (
+	attestExample = `  {{.appName}} {{.command}} --output [FORMAT] --key [KEY] alpine:latest
+  Supports the following image sources:
+    {{.appName}} {{.command}} --key [KEY] yourrepo/yourimage:tag     defaults to using images from a Docker daemon. If Docker is not present, the image is pulled directly from the registry.
+    {{.appName}} {{.command}} --key [KEY] path/to/a/file/or/dir      only for OCI tar or OCI directory
+`
+	attestSchemeHelp = "\n" + indent + schemeHelpHeader + "\n" + imageSchemeHelp
+
+	attestHelp = attestExample + attestSchemeHelp
+)
+
+func Attest(v *viper.Viper, app *config.Application, ro *options.RootOptions) *cobra.Command {
+	ao := options.AttestOptions{}
+	cmd := &cobra.Command{
+		Use:   "attest --output [FORMAT] --key [KEY] [SOURCE]",
+		Short: "Generate a package SBOM as an attestation for the given [SOURCE] container image",
+		Long:  "Generate a packaged-based Software Bill Of Materials (SBOM) from a container image as the predicate of an in-toto attestation",
+		Example: internal.Tprintf(attestHelp, map[string]interface{}{
+			"appName": internal.ApplicationName,
+			"command": "attest",
+		}),
+		Args:          helpArgs,
+		SilenceUsage:  true,
+		SilenceErrors: true,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			// this MUST be called first to make sure app config decodes
+			// the viper object correctly
+			if err := app.LoadAllValues(v, ro.Config); err != nil {
+				return err
+			}
+			// configure logging for command
+			newLogWrapper(app)
+
+			if app.CheckForAppUpdate {
+				checkForApplicationUpdate()
+			}
+
+			return attest.Run(cmd.Context(), app, args)
+		},
+	}
+
+	err := ao.AddFlags(cmd, v)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return cmd
+}

cmd/syft/cli/attest/attest.go

@@ -0,0 +1,214 @@
+package attest
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/anchore/stereoscope"
+	"github.com/anchore/stereoscope/pkg/image"
+	"github.com/anchore/syft/cmd/syft/cli/eventloop"
+	"github.com/anchore/syft/cmd/syft/cli/options"
+	"github.com/anchore/syft/cmd/syft/cli/packages"
+	"github.com/anchore/syft/internal/bus"
+	"github.com/anchore/syft/internal/config"
+	"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/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/in-toto/in-toto-golang/in_toto"
+	"github.com/pkg/errors"
+	"github.com/sigstore/cosign/cmd/cosign/cli/sign"
+	"github.com/sigstore/cosign/pkg/cosign/attestation"
+	"github.com/sigstore/sigstore/pkg/signature/dsse"
+	"github.com/wagoodman/go-partybus"
+
+	signatureoptions "github.com/sigstore/sigstore/pkg/signature/options"
+)
+
+var allowedAttestFormats = []sbom.FormatID{
+	syftjson.ID,
+	spdx22json.ID,
+	cyclonedxjson.ID,
+}
+
+var intotoJSONDsseType = `application/vnd.in-toto+json`
+
+func Run(ctx context.Context, app *config.Application, 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")
+	}
+
+	// can only be an image for attestation or OCI DIR
+	userInput := args[0]
+	si, err := sourceFromInput(userInput, app)
+	if err != nil {
+		return err
+	}
+
+	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...))
+	}
+
+	passFunc, err := selectPassFunc(app.Attest.Key, app.Attest.Password)
+	if err != nil {
+		return err
+	}
+
+	ko := sign.KeyOpts{
+		KeyRef:   app.Attest.Key,
+		PassFunc: passFunc,
+	}
+
+	sv, err := sign.SignerFromKeyOpts(ctx, "", "", ko)
+	if err != nil {
+		return err
+	}
+	defer sv.Close()
+
+	eventBus := partybus.NewBus()
+	stereoscope.SetBus(eventBus)
+	syft.SetBus(eventBus)
+
+	return eventloop.EventLoop(
+		execWorker(app, *si, format, predicateType, sv),
+		eventloop.SetupSignals(),
+		eventBus.Subscribe(),
+		stereoscope.Cleanup,
+		ui.Select(options.IsVerbose(app), app.Quiet)...,
+	)
+}
+
+func sourceFromInput(userInput string, app *config.Application) (s *source.Input, err error) {
+	si, err := source.ParseInput(userInput, app.Platform, false)
+	if err != nil {
+		return nil, fmt.Errorf("could not generate source input for attest command: %w", err)
+	}
+
+	switch si.Scheme {
+	case source.ImageScheme, source.UnknownScheme:
+		// at this point we know that it cannot be dir: or file: schemes;
+		// we will assume that the unknown scheme could represent an image;
+		si.Scheme = source.ImageScheme
+	default:
+		return nil, fmt.Errorf("attest command can only be used with image sources but discovered %q when given %q", si.Scheme, userInput)
+	}
+
+	// if the original detection was from the local daemon we want to short circuit
+	// that and attempt to generate the image source from its current registry source instead
+	switch si.ImageSource {
+	case image.UnknownSource, image.OciRegistrySource:
+		si.ImageSource = image.OciRegistrySource
+	default:
+		return nil, fmt.Errorf("attest command can only be used with image sources fetch directly from the registry, but discovered an image source of %q when given %q", si.ImageSource, userInput)
+	}
+
+	return si, nil
+}
+
+func execWorker(app *config.Application, sourceInput source.Input, format sbom.Format, predicateType string, sv *sign.SignerVerifier) <-chan error {
+	errs := make(chan error)
+	go func() {
+		defer close(errs)
+
+		src, cleanup, err := source.NewFromRegistry(sourceInput, app.Registry.ToOptions(), app.Exclusions)
+		if cleanup != nil {
+			defer cleanup()
+		}
+		if err != nil {
+			errs <- fmt.Errorf("failed to construct source from user input %q: %w", sourceInput.UserInput, err)
+			return
+		}
+
+		s, err := packages.GenerateSBOM(src, errs, app)
+		if err != nil {
+			errs <- err
+			return
+		}
+
+		sbomBytes, err := syft.Encode(*s, format)
+		if err != nil {
+			errs <- err
+			return
+		}
+
+		err = generateAttestation(sbomBytes, src, sv, predicateType)
+		if err != nil {
+			errs <- err
+			return
+		}
+	}()
+	return errs
+}
+
+func generateAttestation(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")
+	case 1:
+	default:
+		return fmt.Errorf("cannot generate attestation since multiple repo digests were found for the image: %+v", src.Image.Metadata.RepoDigests)
+	}
+
+	wrapped := dsse.WrapSigner(sv, intotoJSONDsseType)
+
+	sh, err := attestation.GenerateStatement(attestation.GenerateOpts{
+		Predicate: bytes.NewBuffer(predicate),
+		Type:      predicateType,
+		Digest:    findValidDigest(src.Image.Metadata.RepoDigests),
+	})
+	if err != nil {
+		return err
+	}
+
+	payload, err := json.Marshal(sh)
+	if err != nil {
+		return err
+	}
+
+	signedPayload, err := wrapped.SignMessage(bytes.NewReader(payload), signatureoptions.WithContext(context.Background()))
+	if err != nil {
+		return errors.Wrap(err, "unable to sign SBOM")
+	}
+
+	bus.Publish(partybus.Event{
+		Type: event.Exit,
+		Value: func() error {
+			_, err := os.Stdout.Write(signedPayload)
+			return err
+		},
+	})
+
+	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:
+		return in_toto.PredicateSPDX
+	case cyclonedxjson.ID:
+		// Tentative see https://github.com/in-toto/attestation/issues/82
+		return "https://cyclonedx.org/bom"
+	case syftjson.ID:
+		return "https://syft.dev/bom"
+	default:
+		return ""
+	}
+}

cmd/syft/cli/attest/password.go

@@ -0,0 +1,56 @@
+package attest
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/anchore/syft/internal"
+	"github.com/anchore/syft/internal/log"
+	"github.com/sigstore/cosign/pkg/cosign"
+)
+
+func selectPassFunc(keypath, password string) (cosign.PassFunc, error) {
+	keyContents, err := os.ReadFile(keypath)
+	if err != nil {
+		return nil, err
+	}
+
+	var fn cosign.PassFunc = func(bool) (b []byte, err error) { return nil, nil }
+
+	_, err = cosign.LoadPrivateKey(keyContents, nil)
+	if err != nil {
+		fn = func(bool) (b []byte, err error) {
+			return fetchPassword(password)
+		}
+	}
+
+	return fn, nil
+}
+
+func fetchPassword(password string) (b []byte, err error) {
+	potentiallyPipedInput, err := internal.IsPipedInput()
+	if err != nil {
+		log.Warnf("unable to determine if there is piped input: %+v", err)
+	}
+
+	switch {
+	case password != "":
+		return []byte(password), nil
+	case potentiallyPipedInput:
+		// handle piped in passwords
+		pwBytes, err := io.ReadAll(os.Stdin)
+		if err != nil {
+			return nil, fmt.Errorf("unable to get password from stdin: %w", err)
+		}
+		// be resilient to input that may have newline characters (in case someone is using echo without -n)
+		cleanPw := strings.TrimRight(string(pwBytes), "\n")
+		return []byte(cleanPw), nil
+	case internal.IsTerminal():
+		return cosign.GetPassFromTerm(false)
+	}
+
+	return nil, errors.New("no method available to fetch password")
+}