Simple cost model for sync requests; Penalize peers perfoming flooding or invalid requests

beacon_chain/eth2_network.nim

@@ -102,6 +102,8 @@ type
     maxInactivityAllowed*: Duration
     netThroughput: AverageThroughput
     score*: int
+    requestQuota*: float
+    lastReqTime*: Moment
     connections*: int
     disconnectedFut: Future[void]
 
@@ -200,6 +202,8 @@ type
     else:
       discard
 
+  InvalidInputsError* = object of CatchableError
+
   NetRes*[T] = Result[T, Eth2NetworkingError]
     ## This is type returned from all network requests
 
@@ -216,6 +220,10 @@ const
     ## Score after which peer will be kicked
   PeerScoreHighLimit* = 1000
     ## Max value of peer's score
+  PeerScoreInvalidRequest* = -500
+    ## This peer is sending malformed or nonsensical data
+  PeerScoreFlooder* = -250
+    ## This peer is sending too many expensive requests
 
   ConcurrentConnections* = 10
     ## Maximum number of active concurrent connection requests.
@@ -368,6 +376,28 @@ proc `<`*(a, b: Peer): bool =
   else:
     false
 
+const
+  maxRequestQuota = 1000000.0
+  fullReplenishTime = 5.seconds
+  replenishRate = (maxRequestQuota / fullReplenishTime.nanoseconds.float)
+  requestFloodingThreshold = -500000.0
+
+proc updateRequestQuota*(peer: Peer, reqCost: float) =
+  let
+    currentTime = now(chronos.Moment)
+    nanosSinceLastReq = nanoseconds(currentTime - peer.lastReqTime)
+    replenishedQuota = peer.requestQuota + nanosSinceLastReq.float * replenishRate
+
+  peer.lastReqTime = currentTime
+  peer.requestQuota = min(replenishedQuota, maxRequestQuota) - reqCost
+
+  if peer.requestQuota < requestFloodingThreshold:
+    peer.updateScore(PeerScoreFlooder)
+    peer.requestQuota = 0.0
+
+func allowedOpsPerSecondCost*(n: int): float =
+  (replenishRate * 1000000000'f / n.float)
+
 proc isSeen*(network: ETh2Node, peerId: PeerID): bool =
   ## Returns ``true`` if ``peerId`` present in SeenTable and time period is not
   ## yet expired.
@@ -617,15 +647,15 @@ proc handleIncomingStream(network: Eth2Node,
   #   defer: setLogLevel(LogLevel.DEBUG)
   #   trace "incoming " & `msgNameLit` & " conn"
 
-  try:
   let peer = peerFromStream(network, conn)
-
+  try:
     # TODO peer connection setup is broken, update info in some better place
     #      whenever race is fix:
     #      https://github.com/status-im/nimbus-eth2/issues/1157
     peer.info = conn.peerInfo
 
     template returnInvalidRequest(msg: ErrorMsg) =
+      peer.updateScore(PeerScoreInvalidRequest)
       await sendErrorResponse(peer, conn, InvalidRequest, msg)
       return
 
@@ -691,6 +721,10 @@ proc handleIncomingStream(network: Eth2Node,
     try:
       logReceivedMsg(peer, MsgType(msg.get))
       await callUserHandler(MsgType, peer, conn, msg.get)
+    except InvalidInputsError as err:
+      returnInvalidRequest err.msg
+      await sendErrorResponse(peer, conn, ServerError,
+                              ErrorMsg err.msg.toBytes)
     except CatchableError as err:
       await sendErrorResponse(peer, conn, ServerError,
                               ErrorMsg err.msg.toBytes)
@@ -700,6 +734,7 @@ proc handleIncomingStream(network: Eth2Node,
 
   finally:
     await conn.closeWithEOF()
+    discard network.peerPool.checkPeerScore(peer)
 
 proc toPeerAddr*(r: enr.TypedRecord):
     Result[PeerAddr, cstring] {.raises: [Defect].} =
@@ -1024,6 +1059,7 @@ proc init*(T: type Peer, network: Eth2Node, info: PeerInfo): Peer =
   result.network = network
   result.connectionState = Connected
   result.maxInactivityAllowed = 15.minutes # TODO: Read this from the config
+  result.lastReqTime = now(chronos.Moment)
   newSeq result.protocolStates, allProtocols.len
   for i in 0 ..< allProtocols.len:
     let proto = allProtocols[i]

beacon_chain/peer_pool.nim

@@ -253,7 +253,7 @@ proc shortLogSpace*[A, B](pool: PeerPool[A, B]): string =
 proc shortLogCurrent*[A, B](pool: PeerPool[A, B]): string =
   $pool.curIncPeersCount & "/" & $pool.curOutPeersCount
 
-proc checkPeerScore[A, B](pool: PeerPool[A, B], peer: A): bool {.inline.} =
+proc checkPeerScore*[A, B](pool: PeerPool[A, B], peer: A): bool {.inline.} =
   ## Returns ``true`` if peer passing score check.
   if not(isNil(pool.scoreCheck)):
     pool.scoreCheck(peer)

beacon_chain/sync_protocol.nim

@@ -11,6 +11,10 @@ logScope:
 const
   MAX_REQUEST_BLOCKS = 1024
 
+  blockByRootLookupCost = allowedOpsPerSecondCost(50)
+  blockResponseCost = allowedOpsPerSecondCost(100)
+  blockByRangeLookupCost = allowedOpsPerSecondCost(20)
+
 type
   StatusMsg* = object
     forkDigest*: ForkDigest
@@ -139,7 +143,7 @@ p2pProtocol BeaconSync(version = 1,
       {.async, libp2pProtocol("beacon_blocks_by_range", 1).} =
     trace "got range request", peer, startSlot,
                                count = reqCount, step = reqStep
-    if reqCount > 0'u64:
+    if reqCount > 0'u64 and reqStep > 0'u64:
       var blocks: array[MAX_REQUEST_BLOCKS, BlockRef]
       let
         chainDag = peer.networkState.chainDag
@@ -151,6 +155,9 @@ p2pProtocol BeaconSync(version = 1,
         startIndex =
           chainDag.getBlockRange(startSlot, reqStep,
                                  blocks.toOpenArray(0, endIndex))
+      peer.updateRequestQuota(
+        blockByRangeLookupCost +
+        max(0, endIndex - startIndex + 1).float * blockResponseCost)
 
       for i in startIndex..endIndex:
         doAssert not blocks[i].isNil, "getBlockRange should return non-nil blocks only"
@@ -160,6 +167,8 @@ p2pProtocol BeaconSync(version = 1,
 
       debug "Block range request done",
         peer, startSlot, count, reqStep, found = count - startIndex
+    else:
+      raise newException(InvalidInputsError, "Potential DoS attack: empty blocksByRange")
 
   proc beaconBlocksByRoot(
       peer: Peer,
@@ -168,18 +177,24 @@ p2pProtocol BeaconSync(version = 1,
       blockRoots: BlockRootsList,
       response: MultipleChunksResponse[SignedBeaconBlock])
       {.async, libp2pProtocol("beacon_blocks_by_root", 1).} =
+    if blockRoots.len == 0:
+      raise newException(InvalidInputsError, "Potential DoS attack: empty blocksByRoot")
+
     let
       chainDag = peer.networkState.chainDag
       count = blockRoots.len
 
-    var found = 0
+    peer.updateRequestQuota(count.float * blockByRootLookupCost)
 
+    var found = 0
     for i in 0..<count:
       let blockRef = chainDag.getRef(blockRoots[i])
       if not isNil(blockRef):
         await response.write(chainDag.get(blockRef).data)
         inc found
 
+    peer.updateRequestQuota(found.float * blockResponseCost)
+
     debug "Block root request done",
       peer, roots = blockRoots.len, count, found