feat: fixes #724: add input for --provenance-repository while image verification

README.md

@@ -262,6 +262,28 @@ The only requirement is that the provenance file covers all artifacts passed as
 
 To verify a container image, you need to pass a container image name that is _immutable_ by providing its digest, in order to avoid [TOCTOU attacks](#toctou-attacks).
 
+#### The verify-image command
+
+```bash
+$ slsa-verifier verify-image --help
+Verifies SLSA provenance for an image
+
+Usage:
+  slsa-verifier verify-image [flags] tarball
+
+Flags:
+      --build-workflow-input map[]    [optional] a workflow input provided by a user at trigger time in the format 'key=value'. (Only for 'workflow_dispatch' events on GitHub Actions). (default map[])
+      --builder-id string             [optional] the unique builder ID who created the provenance
+  -h, --help                          help for verify-npm-package
+      --print-provenance              [optional] print the verified provenance to stdout
+      --provenance-path string        path to a provenance file
+      --provenance-repository  string [optional] provenance repository when stored different from image repository. When set, overrides COSIGN_REPOSITORY environment variable
+      --source-branch string          [optional] expected branch the binary was compiled from
+      --source-tag string             [optional] expected tag the binary was compiled from
+      --source-uri string             expected source repository that should have produced the binary, e.g. github.com/some/repo
+      --source-versioned-tag string   [optional] expected version the binary was compiled from. Uses semantic version to match the tag
+```
+
 First set the image name:
 
 ```shell

cli/slsa-verifier/verify.go

@@ -76,7 +76,7 @@ func verifyArtifactCmd() *cobra.Command {
 }
 
 func verifyImageCmd() *cobra.Command {
-	o := &verify.VerifyOptions{}
+	o := &verify.VerifyImageOptions{}
 
 	cmd := &cobra.Command{
 		Use: "verify-image [flags] image",
@@ -96,6 +96,9 @@ func verifyImageCmd() *cobra.Command {
 			if cmd.Flags().Changed("provenance-path") {
 				v.ProvenancePath = &o.ProvenancePath
 			}
+			if cmd.Flags().Changed("provenance-repository") {
+				v.ProvenanceRepository = &o.ProvenanceRepository
+			}
 			if cmd.Flags().Changed("source-branch") {
 				v.SourceBranch = &o.SourceBranch
 			}

cli/slsa-verifier/verify/options.go

@@ -74,6 +74,24 @@ func (o *VerifyOptions) AddFlags(cmd *cobra.Command) {
 	cmd.MarkFlagsMutuallyExclusive("source-versioned-tag", "source-tag")
 }
 
+// VerifyImageOptions is the top-level options for the `verifyImage` command
+
+type VerifyImageOptions struct {
+	VerifyOptions
+	/* Other */
+	ProvenanceRepository string
+}
+
+var _ Interface = (*VerifyImageOptions)(nil)
+
+// AddFlags implements Interface.
+func (o *VerifyImageOptions) AddFlags(cmd *cobra.Command) {
+	o.VerifyOptions.AddFlags(cmd)
+
+	cmd.Flags().StringVar(&o.ProvenanceRepository, "provenance-repository", "",
+		"image repository for provenance with format: <registry>/<repository>. When set, overrides COSIGN_REPOSITORY environment variable")
+}
+
 // VerifyNpmOptions is the top-level options for the `verifyNpmPackage` command.
 type VerifyNpmOptions struct {
 	VerifyOptions

cli/slsa-verifier/verify/verify_image.go

@@ -30,14 +30,15 @@ type ComputeDigestFn func(string) (string, error)
 // Note: nil branch, tag, version-tag and builder-id means we ignore them during verification.
 type VerifyImageCommand struct {
 	// May be nil if supplied alongside in the registry
-	ProvenancePath      *string
-	BuilderID           *string
-	SourceURI           string
-	SourceBranch        *string
-	SourceTag           *string
-	SourceVersionTag    *string
-	BuildWorkflowInputs map[string]string
-	PrintProvenance     bool
+	ProvenancePath       *string
+	ProvenanceRepository *string
+	BuilderID            *string
+	SourceURI            string
+	SourceBranch         *string
+	SourceTag            *string
+	SourceVersionTag     *string
+	BuildWorkflowInputs  map[string]string
+	PrintProvenance      bool
 }
 
 func (c *VerifyImageCommand) Exec(ctx context.Context, artifacts []string) (*utils.TrustedBuilderID, error) {
@@ -70,7 +71,15 @@ func (c *VerifyImageCommand) Exec(ctx context.Context, artifacts []string) (*uti
 		}
 	}
 
-	verifiedProvenance, outBuilderID, err := verifiers.VerifyImage(ctx, artifacts[0], provenance, provenanceOpts, builderOpts)
+	var verifiedProvenance []byte
+	var outBuilderID *utils.TrustedBuilderID
+
+	if c.ProvenanceRepository != nil {
+		verifiedProvenance, outBuilderID, err = verifiers.VerifyImageProvenanceRepo(ctx, artifacts[0], provenance, *c.ProvenanceRepository, provenanceOpts, builderOpts)
+	} else {
+		verifiedProvenance, outBuilderID, err = verifiers.VerifyImage(ctx, artifacts[0], provenance, provenanceOpts, builderOpts)
+	}
+
 	if err != nil {
 		return nil, err
 	}

register/register.go

@@ -24,8 +24,14 @@ type SLSAVerifier interface {
 
 	// VerifyImage verifies a provenance for a supplied OCI image.
 	VerifyImage(ctx context.Context,
-		provenance []byte, artifactImage string,
-		provenanceOpts *options.ProvenanceOpts,
+		provenance []byte, artifactImage string, provenanceOpts *options.ProvenanceOpts,
+		builderOpts *options.BuilderOpts,
+	) ([]byte, *utils.TrustedBuilderID, error)
+
+	// VerifyImageProvenanceRepo verifies a provenance stored in a separate repository for a supplied OCI image.
+	VerifyImageProvenanceRepo(ctx context.Context,
+		provenance []byte, provenanceRepository string,
+		artifactImage string, provenanceOpts *options.ProvenanceOpts,
 		builderOpts *options.BuilderOpts,
 	) ([]byte, *utils.TrustedBuilderID, error)
 

verifiers/internal/gcb/verifier.go

@@ -50,8 +50,7 @@ func (v *GCBVerifier) VerifyNpmPackage(ctx context.Context,
 
 // VerifyImage verifies provenance for an OCI image.
 func (v *GCBVerifier) VerifyImage(ctx context.Context,
-	provenance []byte, artifactImage string,
-	provenanceOpts *options.ProvenanceOpts,
+	provenance []byte, artifactImage string, provenanceOpts *options.ProvenanceOpts,
 	builderOpts *options.BuilderOpts,
 ) ([]byte, *utils.TrustedBuilderID, error) {
 	prov, err := ProvenanceFromBytes(provenance)
@@ -126,3 +125,12 @@ func (v *GCBVerifier) VerifyImage(ctx context.Context,
 	}
 	return content, builderID, nil
 }
+
+// VerifyImageProvenanceRepo verifies provenance for an OCI image.
+func (v *GCBVerifier) VerifyImageProvenanceRepo(ctx context.Context,
+	provenance []byte, provenanceRepository string,
+	artifactImage string, provenanceOpts *options.ProvenanceOpts,
+	builderOpts *options.BuilderOpts,
+) ([]byte, *utils.TrustedBuilderID, error) {
+	return v.VerifyImage(ctx, provenance, artifactImage, provenanceOpts, builderOpts)
+}

verifiers/internal/gha/verifier.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/google/go-containerregistry/pkg/name"
 	"github.com/secure-systems-lab/go-securesystemslib/dsse"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
 	"github.com/sigstore/rekor/pkg/client"
@@ -243,39 +244,9 @@ func (v *GHAVerifier) VerifyArtifact(ctx context.Context,
 		utils.MergeMaps(defaultArtifactTrustedReusableWorkflows, defaultBYOBReusableWorkflows))
 }
 
-// VerifyImage verifies provenance for an OCI image.
-func (v *GHAVerifier) VerifyImage(ctx context.Context,
-	provenance []byte, artifactImage string,
-	provenanceOpts *options.ProvenanceOpts,
-	builderOpts *options.BuilderOpts,
-) ([]byte, *utils.TrustedBuilderID, error) {
-	/* Retrieve any valid signed attestations that chain up to Fulcio root CA. */
-	trustedRoot, err := TrustedRootSingleton(ctx)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// Parse any provenance target repository set using environment variable COSIGN_REPOSITORY
-	provenanceTargetRepository, err := ociremote.GetEnvTargetRepository()
-	if err != nil {
-		return nil, nil, err
-	}
-
-	registryClientOpts := []ociremote.Option{}
-
-	// Append target repository to OCI Registry opts
-	// Must be authenticated against the specified target repository externally
-	if provenanceTargetRepository.Name() != "" {
-		registryClientOpts = append(registryClientOpts, ociremote.WithTargetRepository(provenanceTargetRepository))
-	}
-
-	opts := &cosign.CheckOpts{
-		RegistryClientOpts: registryClientOpts,
-		RootCerts:          trustedRoot.FulcioRoot,
-		IntermediateCerts:  trustedRoot.FulcioIntermediates,
-		RekorPubKeys:       trustedRoot.RekorPubKeys,
-		CTLogPubKeys:       trustedRoot.CTPubKeys,
-	}
+// verifyImageWithOptions abstracts the cosign options and returns verified provenance for an artifact.
+func verifyImageWithOptions(ctx context.Context, artifactImage string, provenanceOpts *options.ProvenanceOpts,
+	builderOpts *options.BuilderOpts, opts *cosign.CheckOpts) ([]byte, *utils.TrustedBuilderID, error) {
 	atts, _, err := container.RunCosignImageVerification(ctx,
 		artifactImage, opts)
 	if err != nil {
@@ -322,6 +293,70 @@ func (v *GHAVerifier) VerifyImage(ctx context.Context,
 	return nil, nil, fmt.Errorf("%w", serrors.ErrorNoValidSignature)
 }
 
+// VerifyImage verifies provenance for an OCI image.
+func (v *GHAVerifier) VerifyImage(ctx context.Context,
+	provenance []byte, artifactImage string, provenanceOpts *options.ProvenanceOpts,
+	builderOpts *options.BuilderOpts,
+) ([]byte, *utils.TrustedBuilderID, error) {
+	/* Retrieve any valid signed attestations that chain up to Fulcio root CA. */
+	trustedRoot, err := TrustedRootSingleton(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+	opts := &cosign.CheckOpts{
+		RootCerts:         trustedRoot.FulcioRoot,
+		IntermediateCerts: trustedRoot.FulcioIntermediates,
+		RekorPubKeys:      trustedRoot.RekorPubKeys,
+		CTLogPubKeys:      trustedRoot.CTPubKeys,
+	}
+	return verifyImageWithOptions(ctx, artifactImage, provenanceOpts, builderOpts, opts)
+}
+
+// VerifyImageProvenanceRepo verifies provenance from a separate store for an OCI image.
+func (v *GHAVerifier) VerifyImageProvenanceRepo(ctx context.Context,
+	provenance []byte, provenanceRepository string,
+	artifactImage string, provenanceOpts *options.ProvenanceOpts,
+	builderOpts *options.BuilderOpts,
+) ([]byte, *utils.TrustedBuilderID, error) {
+	/* Retrieve any valid signed attestations that chain up to Fulcio root CA. */
+	trustedRoot, err := TrustedRootSingleton(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var provenanceTargetRepository name.Repository
+	// Consume input for --provenance-repository when set
+	if provenanceRepository != "" {
+		provenanceTargetRepository, err = name.NewRepository(provenanceRepository)
+		if err != nil {
+			return nil, nil, err
+		}
+	} else {
+		// If user input --provenance-repository is empty, look for COSIGN_REPOSITORY environment
+		provenanceTargetRepository, err = ociremote.GetEnvTargetRepository()
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	registryClientOpts := []ociremote.Option{}
+
+	// Append target repository to OCI Registry opts
+	// Must be authenticated against the specified target repository externally
+	if provenanceTargetRepository.Name() != "" {
+		registryClientOpts = append(registryClientOpts, ociremote.WithTargetRepository(provenanceTargetRepository))
+	}
+
+	opts := &cosign.CheckOpts{
+		RegistryClientOpts: registryClientOpts,
+		RootCerts:          trustedRoot.FulcioRoot,
+		IntermediateCerts:  trustedRoot.FulcioIntermediates,
+		RekorPubKeys:       trustedRoot.RekorPubKeys,
+		CTLogPubKeys:       trustedRoot.CTPubKeys,
+	}
+	return verifyImageWithOptions(ctx, artifactImage, provenanceOpts, builderOpts, opts)
+}
+
 // VerifyNpmPackage verifies an npm package tarball.
 func (v *GHAVerifier) VerifyNpmPackage(ctx context.Context,
 	attestations []byte, tarballHash string,

verifiers/verifier.go

@@ -47,6 +47,19 @@ func VerifyImage(ctx context.Context, artifactImage string,
 	return verifier.VerifyImage(ctx, provenance, artifactImage, provenanceOpts, builderOpts)
 }
 
+func VerifyImageProvenanceRepo(ctx context.Context, artifactImage string,
+	provenance []byte,
+	provenanceRepository string,
+	provenanceOpts *options.ProvenanceOpts,
+	builderOpts *options.BuilderOpts,
+) ([]byte, *utils.TrustedBuilderID, error) {
+	verifier, err := getVerifier(builderOpts)
+	if err != nil {
+		return nil, nil, err
+	}
+	return verifier.VerifyImageProvenanceRepo(ctx, provenance, provenanceRepository, artifactImage, provenanceOpts, builderOpts)
+}
+
 func VerifyArtifact(ctx context.Context,
 	provenance []byte, artifactHash string,
 	provenanceOpts *options.ProvenanceOpts,