feat: Add support for DSSE Rekor type (#742)

This is in preparation for switching over the Rekor entry type in the
slsa github generator to be the newer DSSE type. This adds support for
searching for both intoto v001 and dsse v001 entries.

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

verifiers/internal/gha/rekor.go

@@ -15,20 +15,21 @@ import (
 
 	cjson "github.com/docker/go/canonical/json"
 	"github.com/go-openapi/runtime"
-	"github.com/go-openapi/strfmt"
-	"github.com/go-openapi/swag"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
 	"github.com/sigstore/rekor/pkg/generated/client"
 	"github.com/sigstore/rekor/pkg/generated/client/entries"
 	"github.com/sigstore/rekor/pkg/generated/client/index"
 	"github.com/sigstore/rekor/pkg/generated/models"
 	"github.com/sigstore/rekor/pkg/sharding"
 	"github.com/sigstore/rekor/pkg/types"
-	intotod "github.com/sigstore/rekor/pkg/types/intoto/v0.0.1"
+	"github.com/sigstore/rekor/pkg/types/dsse"
+	dsse_v001 "github.com/sigstore/rekor/pkg/types/dsse/v0.0.1"
+	"github.com/sigstore/rekor/pkg/types/intoto"
+	intoto_v001 "github.com/sigstore/rekor/pkg/types/intoto/v0.0.1"
 	rverify "github.com/sigstore/rekor/pkg/verify"
 	"github.com/sigstore/sigstore/pkg/cryptoutils"
 	"github.com/sigstore/sigstore/pkg/signature"
-	"github.com/sigstore/sigstore/pkg/signature/dsse"
+	dsseverifier "github.com/sigstore/sigstore/pkg/signature/dsse"
 	"github.com/slsa-framework/slsa-github-generator/signing/envelope"
 
 	serrors "github.com/slsa-framework/slsa-verifier/v2/errors"
@@ -123,14 +124,19 @@ func extractCert(e *models.LogEntryAnon) (*x509.Certificate, error) {
 
 	var publicKeyB64 []byte
 	switch e := eimpl.(type) {
-	case *intotod.V001Entry:
+	case *intoto_v001.V001Entry:
 		publicKeyB64, err = e.IntotoObj.PublicKey.MarshalText()
-		if err != nil {
-			return nil, err
+	case *dsse_v001.V001Entry:
+		if len(e.DSSEObj.Signatures) > 1 {
+			return nil, errors.New("multiple signatures on DSSE envelopes are not currently supported")
 		}
+		publicKeyB64, err = e.DSSEObj.Signatures[0].Verifier.MarshalText()
 	default:
 		return nil, errors.New("unexpected tlog entry type")
 	}
+	if err != nil {
+		return nil, err
+	}
 
 	publicKey, err := base64.StdEncoding.DecodeString(string(publicKeyB64))
 	if err != nil {
@@ -149,19 +155,31 @@ func extractCert(e *models.LogEntryAnon) (*x509.Certificate, error) {
 	return certs[0], err
 }
 
-func intotoEntry(certPem, provenance []byte) (*intotod.V001Entry, error) {
+func intotoEntry(certPem, provenance []byte) (models.ProposedEntry, error) {
 	if len(certPem) == 0 {
 		return nil, fmt.Errorf("no signing certificate found in intoto envelope")
 	}
-	cert := strfmt.Base64(certPem)
-	return &intotod.V001Entry{
-		IntotoObj: models.IntotoV001Schema{
-			Content: &models.IntotoV001SchemaContent{
-				Envelope: string(provenance),
-			},
-			PublicKey: &cert,
-		},
-	}, nil
+	var pubKeyBytes [][]byte
+	pubKeyBytes = append(pubKeyBytes, certPem)
+
+	return types.NewProposedEntry(context.Background(), intoto.KIND, intoto_v001.APIVERSION, types.ArtifactProperties{
+		ArtifactBytes:  provenance,
+		PublicKeyBytes: pubKeyBytes,
+	})
+}
+
+func dsseEntry(certPem, provenance []byte) (models.ProposedEntry, error) {
+	if len(certPem) == 0 {
+		return nil, fmt.Errorf("no signing certificate found in intoto envelope")
+	}
+
+	var pubKeyBytes [][]byte
+	pubKeyBytes = append(pubKeyBytes, certPem)
+
+	return types.NewProposedEntry(context.Background(), dsse.KIND, dsse_v001.APIVERSION, types.ArtifactProperties{
+		ArtifactBytes:  provenance,
+		PublicKeyBytes: pubKeyBytes,
+	})
 }
 
 // getUUIDsByArtifactDigest finds all entry UUIDs by the digest of the artifact binary.
@@ -195,15 +213,15 @@ func GetValidSignedAttestationWithCert(rClient *client.Rekor,
 		return nil, fmt.Errorf("error getting certificate from provenance: %w", err)
 	}
 
-	e, err := intotoEntry(certPem, provenance)
+	intotoEntry, err := intotoEntry(certPem, provenance)
 	if err != nil {
 		return nil, fmt.Errorf("error creating intoto entry: %w", err)
 	}
-	entry := models.Intoto{
-		APIVersion: swag.String(e.APIVersion()),
-		Spec:       e.IntotoObj,
+	dsseEntry, err := dsseEntry(certPem, provenance)
+	if err != nil {
+		return nil, err
 	}
-	searchLogQuery.SetEntries([]models.ProposedEntry{&entry})
+	searchLogQuery.SetEntries([]models.ProposedEntry{intotoEntry, dsseEntry})
 
 	params.SetEntry(&searchLogQuery)
 	resp, err := rClient.Entries.SearchLogQuery(params)
@@ -347,7 +365,7 @@ func verifySignedAttestation(signedAtt *SignedAttestation, trustedRoot *TrustedR
 	}
 
 	// 2. Verify signature using validated certificate.
-	verifier = dsse.WrapVerifier(verifier)
+	verifier = dsseverifier.WrapVerifier(verifier)
 	if err := verifier.VerifySignature(bytes.NewReader(attBytes), bytes.NewReader(attBytes)); err != nil {
 		return fmt.Errorf("%w: %s", serrors.ErrorInvalidSignature, err)
 	}