params: reject chain config missing blobSchedule when Osaka is enabled

params/blob_config.go

@@ -53,6 +53,21 @@ func (bcfg *BlobConfig) MaxBlobGas() uint64 {
 	return uint64(bcfg.Max) * BlobTxBlobGasPerBlob
 }
 
+// validate checks that a blob config from a chain configuration is sane.
+// UpdateFraction must be non-zero because it is used as a division denominator.
+func (bcfg *BlobConfig) validate() error {
+	if bcfg.Max < 0 {
+		return errors.New("max < 0")
+	}
+	if bcfg.Target < 0 {
+		return errors.New("target < 0")
+	}
+	if bcfg.UpdateFraction == 0 {
+		return errors.New("update fraction must be defined and non-zero")
+	}
+	return nil
+}
+
 // blobPriceEIP4844 returns the price for EIP-4844 of one blob in Wei.
 func (bcfg *BlobConfig) BlobPriceEIP4844(excessBlobGas uint64) *big.Int {
 	f := bcfg.BlobBaseFeeEIP4844(excessBlobGas)

params/config.go

@@ -449,7 +449,7 @@ func (c *ChainConfig) Copy() *ChainConfig {
 
 // BlobConfig returns the blob config associated with the provided fork.
 func (c *ChainConfig) BlobConfig(head *big.Int) *BlobConfig {
-	if c.IsOsakaForkEnabled(head) {
+	if c.IsOsakaForkEnabled(head) && c.BlobScheduleConfig != nil {
 		return c.BlobScheduleConfig.Osaka
 	}
 	return nil
@@ -649,6 +649,19 @@ func (c *ChainConfig) CheckConfigForkOrder() error {
 			lastFork = cur
 		}
 	}
+
+	// Check that the fork enabling blobs explicitly defines a valid blob schedule.
+	var osakaBlobConfig *BlobConfig
+	if c.BlobScheduleConfig != nil {
+		osakaBlobConfig = c.BlobScheduleConfig.Osaka
+	}
+	if osakaBlobConfig != nil {
+		if err := osakaBlobConfig.validate(); err != nil {
+			return fmt.Errorf("invalid chain configuration in blobSchedule for fork %q: %v", "osaka", err)
+		}
+	} else if c.OsakaCompatibleBlock != nil {
+		return fmt.Errorf("invalid chain configuration: missing entry for fork %q in blobSchedule", "osaka")
+	}
 	return nil
 }