get blinded execution payload headers

beacon_chain/spec/mev/bellatrix_mev.nim

@@ -23,7 +23,7 @@ type
     signature*: ValidatorSig
 
   # https://github.com/ethereum/builder-specs/blob/v0.2.0/specs/builder.md#builderbid
-  BuilderBid = object
+  BuilderBid* = object
     header*: ExecutionPayloadHeader
     value*: UInt256
     pubkey*: ValidatorPubKey

beacon_chain/spec/signatures.nim

@@ -317,7 +317,6 @@ proc get_contribution_and_proof_signature*(
 
   blsSign(privkey, signing_root.data)
 
-
 # https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/altair/validator.md#aggregation-selection
 func is_sync_committee_aggregator*(signature: ValidatorSig): bool =
   let
@@ -338,7 +337,7 @@ from stew/byteutils import fromHex
 
 # https://github.com/ethereum/builder-specs/blob/v0.2.0/specs/builder.md#signing
 func compute_builder_signing_root*(
-    fork: Fork, msg: ValidatorRegistrationV1): Eth2Digest =
+    fork: Fork, msg: BuilderBid | ValidatorRegistrationV1): Eth2Digest =
   # Uses genesis fork version regardless
   doAssert fork.current_version == fork.previous_version
 
@@ -362,3 +361,9 @@ proc get_builder_signature*(
     CookedSig =
   let signing_root = compute_builder_signing_root(fork, msg)
   blsSign(privkey, signing_root.data)
+
+proc verify_builder_signature*(
+    fork: Fork, msg: BuilderBid,
+    pubkey: ValidatorPubKey | CookedPubKey, signature: SomeSig): bool =
+  let signing_root = compute_builder_signing_root(fork, msg)
+  blsVerify(pubkey, signing_root.data, signature)

beacon_chain/validators/validator_duties.nim

@@ -480,6 +480,59 @@ proc makeBeaconBlockForHeadAndSlot*(node: BeaconNode,
       head = shortLog(head),
       slot
 
+proc getBlindedExecutionPayload(
+    node: BeaconNode, slot: Slot, executionBlockRoot: Eth2Digest,
+    pubkey: ValidatorPubKey):
+    Future[Result[ExecutionPayloadHeader, cstring]] {.async.} =
+  doAssert not node.restClient.isNil
+
+  let blindedHeader = await node.restClient.getHeader(
+    slot, executionBlockRoot, pubkey)
+
+  const httpOk = 200
+  if blindedHeader.status != httpOk:
+    return err("getBlindedExecutionPayload: non-200 HTTP response")
+  else:
+    #info "getBlindedExecutionPayload: succeeded",
+    #  slot, pubkey = shortLog(pubkey), execution_root = executionBlockRoot
+    if blindedHeader.data.data.message.pubkey != pubkey:
+      return err("getBlindedExecutionPayload: incorrect pubkey")
+
+    if not verify_builder_signature(
+        node.dag.cfg.genesisFork, blindedHeader.data.data.message, pubkey,
+        blindedHeader.data.data.signature):
+      return err("getBlindedExecutionPayload: signature verification failed")
+
+    return ok blindedHeader.data.data.message.header
+
+proc proposeBlockMEV(
+    node: BeaconNode, slot: Slot, head: BlockRef, pubkey: ValidatorPubKey)
+    {.async.} =
+  try:
+    if node.restClient.isNil:
+      debug "proposeBlockMEV: nil REST client",
+        slot, pubkey, head = shortLog(head)
+      return
+
+    let
+      executionBlockRoot = node.dag.loadExecutionBlockRoot(head)
+      executionPayloadHeader =
+        await node.getBlindedExecutionPayload(slot, executionBlockRoot, pubkey)
+
+    if executionPayloadHeader.isErr:
+      info "proposeBlockMEV: failed to get blinded execution payload header",
+        head = shortLog(head),
+        slot, pubkey, executionBlockRoot
+      return
+
+    debug "proposeBlockMEV: got blinded execution payload header",
+      slot, pubkey, executionBlockRoot,
+      head = shortLog(head),
+      payloadHeader = executionPayloadHeader.get
+  except CatchableError as exc:
+    debug "proposeBlockMEV: error",
+      slot, error = exc.msg
+
 proc proposeBlock(node: BeaconNode,
                   validator: AttachedValidator,
                   validator_index: ValidatorIndex,
@@ -515,6 +568,10 @@ proc proposeBlock(node: BeaconNode,
 
   let forkedBlck = newBlock.get()
 
+  # Currently, it doesn't fully propose a block, so continue with control flow
+  if node.config.payloadBuilder.isSome:
+    asyncSpawn node.proposeBlockMEV(slot, head, validator.pubkey)
+
   withBlck(forkedBlck):
     let
       blockRoot = hash_tree_root(blck)