Add very basic fuzzing setup for discovery

tests/fuzzing/discovery/fuzz.nim

@@ -0,0 +1,68 @@
+import
+  streams, posix, sequtils, strutils, chronicles, chronos, byteutils,
+  eth/p2p/[discovery, kademlia, enode], eth/[keys, rlp],
+  ../../p2p/p2p_test_helper
+
+template fuzz(body) =
+  # For code we want to fuzz.
+  try:
+    body
+  except:
+    let e = getCurrentException()
+    debug "Fuzzer input created exception", exception=e.name, trace=e.repr
+    discard kill(getpid(), SIGSEGV)
+
+template noFuzz(body) =
+  # For code not in the scope of the test.
+  # Lets not have false negatives due to possible issues in this code.
+  try:
+    body
+  except:
+    let e = getCurrentException()
+    debug "Exception out of scope of the fuzzing target",
+      exception=e.name, trace=e.repr
+    return
+
+const DefaultListeningPort = 30303
+
+proc fuzzTest() =
+  var
+    msg: seq[byte]
+    address: Address
+    targetNode: DiscoveryProtocol
+
+  noFuzz:
+    # Set up a discovery node, this is the node we target with fuzzing
+    let
+      targetNodeKey = initPrivateKey("a2b50376a79b1a8c8a3296485572bdfbf54708bb46d3c25d73d2723aaaf6a617")
+      targetNodeAddr = localAddress(DefaultListeningPort)
+    targetNode = newDiscoveryProtocol(targetNodeKey, targetNodeAddr, @[])
+    # Create the transport as else replies on the messages send will fail.
+    targetNode.open()
+
+    # Read input from stdin (fastest for AFL)
+    let s = newFileStream(stdin)
+    # We use binary files as with hex we can get lots of "not hex" failures
+    var input = s.readAll()
+    s.close()
+    # Remove newline if it is there
+    input.removeSuffix
+    # TODO: is there a better/faster way?
+    let payload = input.mapIt(it.byte)
+
+    # Sending raw payload is possible but won't find us much. We need a hash and
+    # a signature, and without it there is a big chance it will always result in
+    # "Wrong msg mac from" error.
+    let nodeKey = initPrivateKey("a2b50376a79b1a8c8a3296485572bdfbf54708bb46d3c25d73d2723aaaf6a618")
+    msg = packData(payload, nodeKey)
+    address = localAddress(DefaultListeningPort + 1)
+
+  try:
+    targetNode.receive(address, msg)
+  # These errors are also catched in `processClient` in discovery.nim
+  # TODO: move them a layer down in discovery so we can do a cleaner test there?
+  except RlpError, DiscProtocolError:
+    debug "Receive failed", err = getCurrentExceptionMsg()
+
+fuzz:
+  fuzzTest()

tests/fuzzing/discovery/generate.nim

@@ -0,0 +1,73 @@
+import
+  chronos, times, byteutils, stint, chronicles, streams, nimcrypto, os,
+  strformat, strutils, eth/p2p/[discovery, kademlia], eth/[keys, rlp],
+  ../../p2p/p2p_test_helper
+
+template sourceDir: string = currentSourcePath.rsplit(DirSep, 1)[0]
+const inputsDir = &"{sourceDir}{DirSep}generated-input{DirSep}"
+
+proc toFile(data: Bytes, fn: string) =
+  var s = newFileStream(fn, fmWrite)
+  for x in data:
+    s.write(x)
+  s.close()
+
+const EXPIRATION = 3600 * 24 * 365 * 10
+proc expiration(): uint32 = uint32(epochTime() + EXPIRATION)
+
+proc generate() =
+  ## Generate some valid inputs where one can start fuzzing with
+  let
+    fromAddr = localAddress(30303)
+    toAddr = localAddress(30304)
+    peerKey = initPrivateKey("a2b50376a79b1a8c8a3296485572bdfbf54708bb46d3c25d73d2723aaaf6a617")
+
+  # valid data for a Ping packet
+  block:
+    let payload = rlp.encode((4, fromAddr, toAddr, expiration())).toRange
+    let encodedData = @[1.byte] & payload.toSeq()
+    debug "Ping", data=byteutils.toHex(encodedData)
+
+    encodedData.toFile(inputsDir & "ping")
+
+  # valid data for a Pong packet
+  block:
+    let token = keccak256.digest(@[0])
+    let payload = rlp.encode((toAddr, token , expiration())).toRange
+    let encodedData = @[2.byte] & payload.toSeq()
+    debug "Pong", data=byteutils.toHex(encodedData)
+
+    encodedData.toFile(inputsDir & "pong")
+
+  # valid data for a FindNode packet
+  block:
+    var data: array[64, byte]
+    data[32 .. ^1] = peerKey.getPublicKey.toNodeId().toByteArrayBE()
+    let payload = rlp.encode((data, expiration())).toRange
+    let encodedData = @[3.byte] & payload.toSeq()
+    debug "FindNode", data=byteutils.toHex(encodedData)
+
+    encodedData.toFile(inputsDir & "findnode")
+
+  # valid data for a Neighbours packet
+  block:
+    let
+      n1Addr = localAddress(30305)
+      n2Addr = localAddress(30306)
+      n1Key = initPrivateKey("a2b50376a79b1a8c8a3296485572bdfbf54708bb46d3c25d73d2723aaaf6a618")
+      n2Key = initPrivateKey("a2b50376a79b1a8c8a3296485572bdfbf54708bb46d3c25d73d2723aaaf6a619")
+
+    type Neighbour = tuple[ip: IpAddress, udpPort, tcpPort: Port, pk: PublicKey]
+    var nodes = newSeqOfCap[Neighbour](2)
+
+    nodes.add((n1Addr.ip, n1Addr.udpPort, n1Addr.tcpPort, n1Key.getPublicKey()))
+    nodes.add((n2Addr.ip, n2Addr.udpPort, n2Addr.tcpPort, n2Key.getPublicKey()))
+
+    let payload = rlp.encode((nodes, expiration())).toRange
+    let encodedData = @[4.byte] & payload.toSeq()
+    debug "Neighbours", data=byteutils.toHex(encodedData)
+
+    encodedData.toFile(inputsDir & "neighbours")
+
+discard existsOrCreateDir(inputsDir)
+generate()

tests/fuzzing/fuzz.nims

@@ -0,0 +1,18 @@
+# TODO: make this configurable when more fuzzing targets
+cd "discovery"
+
+if not dirExists("generated-input"):
+  exec "nim c -r generate"
+
+if not fileExists("fuzz"):
+  # Requires afl-gcc to be installed
+  # TODO: add + test option for clang
+  exec "nim c --cc=gcc --gcc.exe=afl-gcc --gcc.linkerexe=afl-gcc fuzz"
+
+if dirExists("output"):
+  exec "afl-fuzz -i - -o output -M fuzzer01 -- ./fuzz"
+else:
+  exec "afl-fuzz -i generated-input -o output -M fuzzer01 -- ./fuzz"
+
+# TODO: how to add slaves for multiple cores in nimscript?
+# afl-fuzz -i generated-input -o output -S fuzzer02 -- ./fuzz

tests/p2p/p2p_test_helper.nim

@@ -1,5 +1,5 @@
 import
-  unittest, chronos, eth/[keys, p2p], eth/p2p/[discovery, enode]
+  unittest, chronos, nimcrypto, eth/[keys, p2p], eth/p2p/[discovery, enode]
 
 var nextPort = 30303
 
@@ -32,3 +32,9 @@ template asyncTest*(name, body: untyped) =
   test name:
     proc scenario {.async.} = body
     waitFor scenario()
+
+proc packData*(payload: seq[byte], pk: PrivateKey): seq[byte] =
+  let
+    signature = @(pk.signMessage(payload).getRaw())
+    msgHash = keccak256.digest(signature & payload)
+  result = @(msgHash.data) & signature & payload

tests/p2p/test_discovery.nim

@@ -8,7 +8,7 @@
 #
 
 import
-  sequtils, unittest, chronos, byteutils, nimcrypto,
+  sequtils, unittest, chronos, byteutils,
   eth/[keys, rlp], eth/p2p/[discovery, kademlia, enode],
   ./p2p_test_helper
 
@@ -16,12 +16,6 @@ proc nodeIdInNodes(id: NodeId, nodes: openarray[Node]): bool =
   for n in nodes:
     if id == n.id: return true
 
-proc packData(payload: seq[byte], pk: PrivateKey): seq[byte] =
-  let
-    signature = @(pk.signMessage(payload).getRaw())
-    msgHash = keccak256.digest(signature & payload)
-  result = @(msgHash.data) & signature & payload
-
 proc test() {.async.} =
   suite "Discovery Tests":
     let