Patch support attestation log search and bundle to payload hash check (…

…#1030) * Patch support attestation log search and bundle to payload hash check Signed-off-by: houdini91 <mdstrauss91@gmail.com> * Fix lint Signed-off-by: houdini91 <mdstrauss91@gmail.com> * Typo Signed-off-by: houdini91 <mdstrauss91@gmail.com> * PR fix Signed-off-by: houdini91 <mdstrauss91@gmail.com> * PR add comment Signed-off-by: houdini91 <mdstrauss91@gmail.com> * PR fix lint Signed-off-by: houdini91 <mdstrauss91@gmail.com>
sigstore · Nov 14, 2021 · 5468ddc · 5468ddc
1 parent fe00315
commit 5468ddc
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Showing 2 changed files with 96 additions and 8 deletions.
diff --git a/pkg/cosign/tlog.go b/pkg/cosign/tlog.go
@@ -145,20 +145,42 @@ func GetTlogEntry(rekorClient *client.Rekor, uuid string) (*models.LogEntryAnon,
 	return nil, errors.New("empty response")
 }
 
+func proposedEntry(b64Sig string, payload, pubKey []byte) ([]models.ProposedEntry, error) {
+	var proposedEntry []models.ProposedEntry
+	signature, err := base64.StdEncoding.DecodeString(b64Sig)
+	if err != nil {
+		return nil, errors.Wrap(err, "decoding base64 signature")
+	}
+
+	// The fact that there's no signature (or empty rather), implies
+	// that this is an Attestation that we're verifying.
+	if len(signature) == 0 {
+		te := intotoEntry(payload, pubKey)
+		entry := &models.Intoto{
+			APIVersion: swag.String(te.APIVersion()),
+			Spec:       te.IntotoObj,
+		}
+		proposedEntry = []models.ProposedEntry{entry}
+	} else {
+		re := rekorEntry(payload, signature, pubKey)
+		entry := &models.Rekord{
+			APIVersion: swag.String(re.APIVersion()),
+			Spec:       re.RekordObj,
+		}
+		proposedEntry = []models.ProposedEntry{entry}
+	}
+	return proposedEntry, nil
+}
+
 func FindTlogEntry(rekorClient *client.Rekor, b64Sig string, payload, pubKey []byte) (uuid string, index int64, err error) {
 	searchParams := entries.NewSearchLogQueryParams()
 	searchLogQuery := models.SearchLogQuery{}
-	signature, err := base64.StdEncoding.DecodeString(b64Sig)
+	proposedEntry, err := proposedEntry(b64Sig, payload, pubKey)
 	if err != nil {
-		return "", 0, errors.Wrap(err, "decoding base64 signature")
-	}
-	re := rekorEntry(payload, signature, pubKey)
-	entry := &models.Rekord{
-		APIVersion: swag.String(re.APIVersion()),
-		Spec:       re.RekordObj,
+		return "", 0, err
 	}
 
-	searchLogQuery.SetEntries([]models.ProposedEntry{entry})
+	searchLogQuery.SetEntries(proposedEntry)
 
 	searchParams.SetEntry(&searchLogQuery)
 	resp, err := rekorClient.Entries.SearchLogQuery(searchParams)

diff --git a/pkg/cosign/verify.go b/pkg/cosign/verify.go
@@ -22,6 +22,7 @@ import (
 	"crypto/sha256"
 	"crypto/x509"
 	"encoding/base64"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -37,6 +38,7 @@ import (
 	ociremote "github.com/sigstore/cosign/pkg/oci/remote"
 	rekor "github.com/sigstore/rekor/pkg/client"
 	"github.com/sigstore/rekor/pkg/generated/client"
+	"github.com/sigstore/rekor/pkg/generated/models"
 	"github.com/sigstore/sigstore/pkg/cryptoutils"
 	"github.com/sigstore/sigstore/pkg/signature"
 	"github.com/sigstore/sigstore/pkg/signature/dsse"
@@ -426,9 +428,73 @@ func VerifyBundle(sig oci.Signature) (bool, error) {
 	if err := checkExpiry(cert, time.Unix(bundle.Payload.IntegratedTime, 0)); err != nil {
 		return false, errors.Wrap(err, "checking expiry on cert")
 	}
+
+	payload, err := sig.Payload()
+	if err != nil {
+		return false, errors.Wrap(err, "reading payload")
+	}
+	signature, err := sig.Base64Signature()
+	if err != nil {
+		return false, errors.Wrap(err, "reading base64signature")
+	}
+
+	alg, bundlehash, err := bundleHash(bundle.Payload.Body.(string), signature)
+	h := sha256.Sum256(payload)
+	payloadHash := hex.EncodeToString(h[:])
+
+	if alg != "sha256" || bundlehash != payloadHash {
+		return false, errors.Wrap(err, "matching bundle to payload")
+	}
 	return true, nil
 }
 
+func bundleHash(bundleBody, signature string) (string, string, error) {
+	var toto models.Intoto
+	var rekord models.Rekord
+	var intotoObj models.IntotoV001Schema
+	var rekordObj models.RekordV001Schema
+
+	bodyDecoded, err := base64.StdEncoding.DecodeString(bundleBody)
+	if err != nil {
+		return "", "", err
+	}
+
+	// The fact that there's no signature (or empty rather), implies
+	// that this is an Attestation that we're verifying.
+	if len(signature) == 0 {
+		err = json.Unmarshal(bodyDecoded, &toto)
+		if err != nil {
+			return "", "", err
+		}
+
+		specMarshal, err := json.Marshal(toto.Spec)
+		if err != nil {
+			return "", "", err
+		}
+		err = json.Unmarshal(specMarshal, &intotoObj)
+		if err != nil {
+			return "", "", err
+		}
+
+		return *intotoObj.Content.Hash.Algorithm, *intotoObj.Content.Hash.Value, nil
+	}
+
+	err = json.Unmarshal(bodyDecoded, &rekord)
+	if err != nil {
+		return "", "", err
+	}
+
+	specMarshal, err := json.Marshal(rekord.Spec)
+	if err != nil {
+		return "", "", err
+	}
+	err = json.Unmarshal(specMarshal, &rekordObj)
+	if err != nil {
+		return "", "", err
+	}
+	return *rekordObj.Data.Hash.Algorithm, *rekordObj.Data.Hash.Value, nil
+}
+
 func VerifySET(bundlePayload oci.BundlePayload, signature []byte, pub *ecdsa.PublicKey) error {
 	contents, err := json.Marshal(bundlePayload)
 	if err != nil {