Save invalid blob to temp under new flag

beacon-chain/sync/validate_blob.go

@@ -3,17 +3,21 @@ package sync
 import (
 	"context"
 	"fmt"
+	"os"
+	"path"
 	"strings"
 
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/pkg/errors"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/verification"
+	"github.com/prysmaticlabs/prysm/v5/config/features"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
 	"github.com/prysmaticlabs/prysm/v5/crypto/rand"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
+	"github.com/prysmaticlabs/prysm/v5/io/file"
 	eth "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	prysmTime "github.com/prysmaticlabs/prysm/v5/time"
 	"github.com/prysmaticlabs/prysm/v5/time/slots"
@@ -109,6 +113,7 @@ func (s *Service) validateBlob(ctx context.Context, pid peer.ID, msg *pubsub.Mes
 	}
 
 	if err := vf.SidecarKzgProofVerified(); err != nil {
+		saveInvalidBlobToTemp(blob)
 		return pubsub.ValidationReject, err
 	}
 
@@ -165,3 +170,21 @@ func blobFields(b blocks.ROBlob) logrus.Fields {
 func computeSubnetForBlobSidecar(index uint64) uint64 {
 	return index % params.BeaconConfig().BlobsidecarSubnetCount
 }
+
+// saveInvalidBlobToTemp as a block ssz. Writes to temp directory.
+func saveInvalidBlobToTemp(b blocks.ROBlob) {
+	if !features.Get().SaveInvalidBlob {
+		return
+	}
+	filename := fmt.Sprintf("blob_sidecar_%d.ssz", b.Slot())
+	fp := path.Join(os.TempDir(), filename)
+	log.Warnf("Writing invalid blob sidecar to disk at %s", fp)
+	enc, err := b.MarshalSSZ()
+	if err != nil {
+		log.WithError(err).Error("Failed to ssz encode blob sidecar")
+		return
+	}
+	if err := file.WriteFile(fp, enc); err != nil {
+		log.WithError(err).Error("Failed to write to disk")
+	}
+}

config/features/config.go

@@ -74,6 +74,7 @@ type Flags struct {
 	BlobSaveFsync bool
 
 	SaveInvalidBlock bool // SaveInvalidBlock saves invalid block to temp.
+	SaveInvalidBlob  bool // SaveInvalidBlob saves invalid blob to temp.
 
 	// KeystoreImportDebounceInterval specifies the time duration the validator waits to reload new keys if they have
 	// changed on disk. This feature is for advanced use cases only.
@@ -195,6 +196,11 @@ func ConfigureBeaconChain(ctx *cli.Context) error {
 		cfg.SaveInvalidBlock = true
 	}
 
+	if ctx.Bool(saveInvalidBlobTempFlag.Name) {
+		logEnabled(saveInvalidBlobTempFlag)
+		cfg.SaveInvalidBlob = true
+	}
+
 	if ctx.IsSet(disableGRPCConnectionLogging.Name) {
 		logDisabled(disableGRPCConnectionLogging)
 		cfg.DisableGRPCConnectionLogs = true

config/features/flags.go

@@ -46,6 +46,10 @@ var (
 		Name:  "save-invalid-block-temp",
 		Usage: "Writes invalid blocks to temp directory.",
 	}
+	saveInvalidBlobTempFlag = &cli.BoolFlag{
+		Name:  "save-invalid-blob-temp",
+		Usage: "Writes invalid blobs to temp directory.",
+	}
 	disableGRPCConnectionLogging = &cli.BoolFlag{
 		Name:  "disable-grpc-connection-logging",
 		Usage: "Disables displaying logs for newly connected grpc clients.",
@@ -201,6 +205,7 @@ var BeaconChainFlags = append(deprecatedBeaconFlags, append(deprecatedFlags, []c
 	enableExperimentalState,
 	writeSSZStateTransitionsFlag,
 	saveInvalidBlockTempFlag,
+	saveInvalidBlobTempFlag,
 	disableGRPCConnectionLogging,
 	HoleskyTestnet,
 	PraterTestnet,