Enr rlp lists (#408)

* Don't fail ENR decoding when value is an RLP list

* Store RLP raw list in the ENR field pair instead

* Add ENR kList FieldKind so lists can be treated differently

Treated differently now when printing out the ENR, mentioning
that it is a raw RLP list

eth/p2p/discoveryv5/enr.nim

@@ -46,7 +46,8 @@ type
   FieldKind = enum
     kString,
     kNum,
-    kBytes
+    kBytes,
+    kList
 
   Field = object
     case kind: FieldKind
@@ -56,6 +57,9 @@ type
       num: BiggestUInt
     of kBytes:
       bytes: seq[byte]
+    of kList:
+      listRaw: seq[byte] ## Differently from the other kinds, this is is stored
+      ## as raw (encoded) RLP data, and thus treated as such further on.
 
   EnrResult*[T] = Result[T, cstring]
 
@@ -68,6 +72,8 @@ template toField[T](v: T): Field =
     Field(kind: kBytes, bytes: v)
   elif T is SomeUnsignedInt:
     Field(kind: kNum, num: BiggestUInt(v))
+  elif T is object|tuple:
+    Field(kind: kList, listRaw: rlp.encode(v))
   else:
     {.error: "Unsupported field type".}
 
@@ -80,6 +86,8 @@ proc `==`(a, b: Field): bool =
       return a.num == b.num
     of kBytes:
       return a.bytes == b.bytes
+    of kList:
+      return a.listRaw == b.listRaw
   else:
     return false
 
@@ -96,6 +104,7 @@ proc makeEnrRaw(seqNum: uint64, pk: PrivateKey,
       of kString: w.append(v.str)
       of kNum: w.append(v.num)
       of kBytes: w.append(v.bytes)
+      of kList: w.appendRawBytes(v.listRaw) # No encoding needs to happen
     w.finish()
 
   let toSign = block:
@@ -419,7 +428,16 @@ proc fromBytesAux(r: var Record): bool {.raises: [RlpError, Defect].} =
       let v = rlp.read(uint16)
       r.pairs.add((k, Field(kind: kNum, num: v)))
     else:
+      # Don't know really what this is supposed to represent so drop it in
+      # `kBytes` field pair when a single byte or blob.
+      if rlp.isSingleByte() or rlp.isBlob():
         r.pairs.add((k, Field(kind: kBytes, bytes: rlp.read(seq[byte]))))
+      elif rlp.isList():
+        # Not supporting decoding lists as value (especially unknown ones),
+        # just drop the raw RLP value in there.
+        r.pairs.add((k, Field(kind: kList, listRaw: @(rlp.rawData()))))
+        # Need to skip the element still.
+        rlp.skipElem()
 
   verifySignature(r)
 
@@ -463,6 +481,8 @@ proc `$`(f: Field): string =
     "0x" & f.bytes.toHex
   of kString:
     "\"" & f.str & "\""
+  of kList:
+    "(Raw RLP list) " & "0x" & f.listRaw.toHex
 
 proc `$`*(r: Record): string =
   result = "("

tests/p2p/test_enr.nim

@@ -37,7 +37,7 @@ suite "ENR":
     var r: Record
     check not fromBytes(r, [])
 
-  test "Base64 dserialsation without data":
+  test "Base64 deserialsation without data":
     var r: Record
     let sigValid = r.fromURI("enr:")
     check(not sigValid)
@@ -243,3 +243,25 @@ suite "ENR":
         typedEnr.udp.get() == 9001
 
         r.seqNum == 4
+
+  test "ENR with RLP list value":
+    type
+      RlpTestList = object
+        number: uint16
+        data: seq[byte]
+        text: string
+
+    let rlpList =
+      RlpTestList(number: 72, data: @[byte 0x0, 0x1, 0x2], text: "Hi there")
+
+    let pk = PrivateKey.fromHex(
+      "5d2908f3f09ea1ff2e327c3f623159639b00af406e9009de5fd4b910fc34049d")[]
+    var r = initRecord(123, pk, {"udp": 1234'u, "ip": [byte 5, 6, 7, 8],
+      "some_list": rlpList})[]
+
+    check($r == """(123, id: "v4", ip: 0x05060708, secp256k1: 0x02E51EFA66628CE09F689BC2B82F165A75A9DDECBB6A804BE15AC3FDF41F3B34E7, some_list: (Raw RLP list) 0xCE4883000102884869207468657265, udp: 1234)""")
+
+    let encoded = rlp.encode(r)
+    let decoded = rlp.decode(encoded, enr.Record)
+    check($decoded == $r)
+    check(decoded.raw == r.raw)