sign blinded blob sidecars during builder API proposals (#5537)

beacon_chain/spec/signatures.nim

@@ -90,7 +90,7 @@ func compute_block_signing_root*(
 
 func compute_blob_signing_root(
     fork: Fork, genesis_validators_root: Eth2Digest, slot: Slot,
-    blob: BlobSidecar): Eth2Digest =
+    blob: BlindedBlobSidecar | BlobSidecar): Eth2Digest =
   let
     epoch = epoch(slot)
     domain = get_domain(fork, DOMAIN_BLOB_SIDECAR, epoch,
@@ -109,7 +109,8 @@ func get_block_signature*(
 # https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.3/specs/deneb/validator.md#constructing-the-signedblobsidecars
 proc get_blob_sidecar_signature*(
   fork: Fork, genesis_validators_root: Eth2Digest, slot: Slot,
-    blob: BlobSidecar, privkey: ValidatorPrivKey): CookedSig =
+    blob: BlindedBlobSidecar | BlobSidecar, privkey: ValidatorPrivKey):
+    CookedSig =
   let signing_root = compute_blob_signing_root(
     fork, genesis_validators_root, slot, blob)
 

beacon_chain/validators/beacon_validators.nim

@@ -761,9 +761,18 @@ proc blindedBlockCheckSlashingAndSign[
       fork, genesis_validators_root, slot, blockRoot,
       blindedBlockContents.signed_blinded_block.message)
     if res.isErr():
-      return err("Unable to sign block: " & res.error())
+      return err("Unable to sign blinded block: " & res.error())
     res.get()
 
+  for signedBlindedBlobSidecar in mitems(
+      blindedBlockContents.signed_blinded_blob_sidecars):
+    signedBlindedBlobSidecar.signature = validator.getBlobSignature(
+        fork, genesis_validators_root, slot,
+        signedBlindedBlobSidecar.message).valueOr:
+      warn "Unable to sign blinded blob",
+           reason = error()
+      return
+
   return ok blindedBlockContents
 
 proc getUnsignedBlindedBeaconBlock[

beacon_chain/validators/validator_pool.nim

@@ -628,7 +628,8 @@ proc getBlockSignature*(v: AttachedValidator, fork: Fork,
 # https://github.com/ethereum/consensus-specs/blob/v1.4.0-alpha.3/specs/deneb/validator.md#constructing-the-signedblobsidecars
 proc getBlobSignature*(v: AttachedValidator, fork: Fork,
                        genesis_validators_root: Eth2Digest, slot: Slot,
-                       blob: BlobSidecar): SignatureResult =
+                       blob: BlindedBlobSidecar | BlobSidecar):
+                       SignatureResult =
   return
     case v.kind
     of ValidatorKind.Local: