Class: DEVp2p::Discovery::Protocol

Inherits:
Kademlia::WireInterface show all
Defined in:
lib/devp2p/discovery/protocol.rb

Constant Summary collapse

VERSION = 
4
EXPIRATION =

let messages expire after N seconds

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CMD_ID_MAP = 
{
  ping: 1,
  pong: 2,
  find_node: 3,
  neighbours: 4
}.freeze
REV_CMD_ID_MAP = 
CMD_ID_MAP.map {|k,v| [v,k] }.to_h.freeze
CMD_ELEM_COUNT_MAP =

number of required top-level list elements for each cmd_id. elements beyond this length are trimmed.

{
  ping: 4,
  poing: 3,
  find_node: 2,
  neighbours: 2
}

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app, service) ⇒ Protocol

Returns a new instance of Protocol.



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# File 'lib/devp2p/discovery/protocol.rb', line 31

def initialize(app, service)
  @app = app
  @service = service

  @privkey = Utils.decode_hex app.config[:node][:privkey_hex]
  @pubkey = Crypto.privtopub @privkey

  @nodes = {} # nodeid => Node
  @node = Node.new(pubkey, @service.address)

  @kademlia = KademliaProtocolAdapter.new @node, self

  uri = Utils.host_port_pubkey_to_uri(ip, udp_port, pubkey)
  logger.info "starting discovery proto", enode: uri
end

Instance Attribute Details

#pubkey ⇒ Object (readonly)

Returns the value of attribute pubkey.



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# File 'lib/devp2p/discovery/protocol.rb', line 29

def pubkey
  @pubkey
end

Instance Method Details

#bootstrap(nodes) ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 47

def bootstrap(nodes)
  @kademlia.bootstrap(nodes) unless nodes.empty?
end

#get_node(nodeid, address = nil) ⇒ Object

return node or create new, update address if supplied

Raises:

  • (ArgumentError) 


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# File 'lib/devp2p/discovery/protocol.rb', line 54

def get_node(nodeid, address=nil)
  raise ArgumentError, 'invalid nodeid' unless nodeid.size == Kademlia::PUBKEY_SIZE / 8
  raise ArgumentError, 'must give either address or existing nodeid' unless address || @nodes.has_key?(nodeid)

  @nodes[nodeid] = Node.new nodeid, address if !@nodes.has_key?(nodeid)
  node = @nodes[nodeid]

  if address
    raise ArgumentError, 'address must be Address' unless address.instance_of?(Address)
    node.address = address
  end

  node
end

#ip ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 307

def ip
  @app.config[:discovery][:listen_host]
end

#pack(cmd_id, payload) ⇒ Object

UDP packets are structured as follows:

hash || signature || packet-type || packet-data

  • packet-type: single byte < 2**7 // valid values are [1,4]

  • packet-data: RLP encoded list. Packet properties are serialized in the order in which they’re defined. See packet-data below.

Offset | 0 | MDC | Ensures integrity of packet. 65 | signature | Ensures authenticity of sender, ‘SIGN(sender-privkey, MDC)` 97 | type | Single byte in range [1, 4] that determines the structure of Data 98 | data | RLP encoded, see section Packet Data

The packets are signed and authenticated. The sender’s Node ID is determined by recovering the public key from the signature.

sender-pubkey = ECRECOVER(Signature)

The integrity of the packet can then be verified by computing the expected MDC of the packet as:

MDC = keccak256(sender-pubkey || type || data)

As an optimization, implementations may look up the public key by the UDP sending address and compute MDC before recovering the sender ID. If the MDC values do not match, the packet can be dropped.

Raises:

  • (ArgumentError) 


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# File 'lib/devp2p/discovery/protocol.rb', line 103

def pack(cmd_id, payload)
  raise ArgumentError, 'invalid cmd_id' unless REV_CMD_ID_MAP.has_key?(cmd_id)
  raise ArgumentError, 'payload must be Array' unless payload.is_a?(Array)

  cmd_id = encode_cmd_id cmd_id
  expiration = encode_expiration Time.now.to_i + EXPIRATION

  encoded_data = RLP.encode(payload + [expiration])
  signed_data = Crypto.keccak256 "#{cmd_id}#{encoded_data}"
  signature = Crypto.ecdsa_sign signed_data, @privkey

  raise InvalidSignatureError unless signature.size == 65

  mdc = Crypto.keccak256 "#{signature}#{cmd_id}#{encoded_data}"
  raise InvalidMACError unless mdc.size == 32

  "#{mdc}#{signature}#{cmd_id}#{encoded_data}"
end

#receive_message(address, message) ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 153

def receive_message(address, message)
  logger.debug "<<< message", address: address
  raise ArgumentError, 'address must be Address' unless address.instance_of?(Address)

  begin
    remote_pubkey, cmd_id, payload, mdc = unpack message

    # Note: as of discovery version 4, expiration is the last element for
    # all packets. This might not be the case for a later version, but
    # just popping the last element is good enough for now.
    expiration = decode_expiration payload.pop
    raise PacketExpired if Time.now.to_i > expiration
  rescue DefectiveMessage
    logger.debug $!
    return
  end

  cmd = "recv_#{REV_CMD_ID_MAP[cmd_id]}"
  nodeid = remote_pubkey

  get_node(nodeid, address) unless @nodes.has_key?(nodeid)
  send cmd, nodeid, payload, mdc
rescue
  logger.error 'invalid message', error: $!, from: address
end

#recv_find_node(nodeid, payload, mdc) ⇒ Object

Raises:



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# File 'lib/devp2p/discovery/protocol.rb', line 262

def recv_find_node(nodeid, payload, mdc)
  node = get_node nodeid

  logger.debug "<<< find_node", remoteid: node
  raise InvalidPayloadError unless payload[0].size == Kademlia::PUBKEY_SIZE/8

  target = Utils.big_endian_to_int payload[0]
  @kademlia.recv_find_node node, target
end

#recv_neighbours(nodeid, payload, mdc) ⇒ Object

Raises:



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# File 'lib/devp2p/discovery/protocol.rb', line 283

def recv_neighbours(nodeid, payload, mdc)
  node = get_node nodeid
  raise InvalidPayloadError unless payload.size == 1
  raise InvalidPayloadError unless payload[0].instance_of?(Array)
  logger.debug "<<< neighbours", remoteid: node, count: payload[0].size

  neighbours_set = payload[0].uniq
  logger.warn "received duplicates" if neighbours_set.size < payload[0].size

  neighbours = neighbours_set.map do |n|
    if n.size != 4 || ![4,16].include?(n[0].size)
      logger.error "invalid neighbours format", neighbours: n
      return
    end

    n = n.dup
    nodeid = n.pop
    address = Address.from_endpoint *n
    get_node nodeid, address
  end

  @kademlia.recv_neighbours node, neighbours
end

#recv_ping(nodeid, payload, mdc) ⇒ Object

Update ip, port in node table. Addresses can only be learned by ping messages.



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# File 'lib/devp2p/discovery/protocol.rb', line 208

def recv_ping(nodeid, payload, mdc)
  if payload.size != 3
    logger.error "invalid ping payload", payload: payload
    return
  end

  node = get_node nodeid
  logger.debug "<<< ping", node: node

  remote_address = Address.from_endpoint(*payload[1]) # from
  my_address = Address.from_endpoint(*payload[2]) # my address

  get_node(nodeid).address.update remote_address
  @kademlia.recv_ping node, mdc
end

#recv_pong(nodeid, payload, mdc) ⇒ Object

Raises:



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# File 'lib/devp2p/discovery/protocol.rb', line 234

def recv_pong(nodeid, payload, mdc)
  if payload.size != 2
    logger.error 'invalid pong payload', payload: payload
    return
  end

  raise InvalidPayloadError unless payload[0].size == 3
  raise InvalidPayloadError unless [4,16].include?(payload[0][0].size)

  my_address = Address.from_endpoint *payload[0]
  echoed = payload[1]

  if @nodes.include?(nodeid)
    node = get_node nodeid
    @kademlia.recv_pong node, echoed
  else
    logger.debug "<<< unexpected pong from unknown node"
  end
end

#send_find_node(node, target_node_id) ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 254

def send_find_node(node, target_node_id)
  target_node_id = Utils.zpad_int target_node_id, Kademlia::PUBKEY_SIZE/8
  logger.debug ">>> find_node", remoteid: node

  message = pack CMD_ID_MAP[:find_node], [target_node_id]
  send_message node, message
end

#send_message(node, message) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/devp2p/discovery/protocol.rb', line 179

def send_message(node, message)
  raise ArgumentError, 'node must have address' unless node.address
  logger.debug ">>> message", address: node.address
  @service.async.send_message node.address, message
end

#send_neighbours(node, neighbours) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/devp2p/discovery/protocol.rb', line 272

def send_neighbours(node, neighbours)
  raise ArgumentError, 'neighbours must be Array' unless neighbours.instance_of?(Array)
  raise ArgumentError, 'neighbours must be Node' unless neighbours.all? {|n| n.is_a?(Node) }

  nodes = neighbours.map {|n| n.address.to_endpoint + [n.pubkey] }
  logger.debug ">>> neighbours", remoteid: node, count: nodes.size

  message = pack CMD_ID_MAP[:neighbours], [nodes]
  send_message node, message
end

#send_ping(node) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/devp2p/discovery/protocol.rb', line 185

def send_ping(node)
  raise ArgumentError, "node must be Node" unless node.is_a?(Node)
  raise ArgumentError, "cannot ping self" if node == @node

  logger.debug ">>> ping", remoteid: node

  version = RLP::Sedes.big_endian_int.serialize VERSION
  payload = [
    version,
    Address.new(ip, udp_port, tcp_port).to_endpoint,
    node.address.to_endpoint
  ]

  message = pack CMD_ID_MAP[:ping], payload
  send_message node, message

  message[0,32] # return the MDC to identify pongs
end

#send_pong(node, token) ⇒ Object

Raises:



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# File 'lib/devp2p/discovery/protocol.rb', line 224

def send_pong(node, token)
  logger.debug ">>> pong", remoteid: node

  payload = [node.address.to_endpoint, token]
  raise InvalidPayloadError unless [4,16].include?(payload[0][0].size)

  message = pack CMD_ID_MAP[:pong], payload
  send_message node, message
end

#sign(msg) ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 69

def sign(msg)
  msg = Crypto.keccak256 msg
  Crypto.ecdsa_sign msg, @privkey
end

#tcp_port ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 315

def tcp_port
  @app.config[:p2p][:listen_port]
end

#udp_port ⇒ Object 



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# File 'lib/devp2p/discovery/protocol.rb', line 311

def udp_port
  @app.config[:discovery][:listen_port]
end

#unpack(message) ⇒ Object

macSize = 256 / 8 = 32 sigSize = 520 / 8 = 65 headSize = macSize + sigSize = 97

Raises:



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# File 'lib/devp2p/discovery/protocol.rb', line 127

def unpack(message)
  mdc = message[0,32]
  if mdc != Crypto.keccak256(message[32..-1])
    logger.warn 'packet with wrong mcd'
    raise InvalidMessageMAC
  end

  signature = message[32,65]
  raise InvalidSignatureError unless signature.size == 65

  signed_data = Crypto.keccak256(message[97..-1])
  remote_pubkey = Crypto.ecdsa_recover(signed_data, signature)
  raise InvalidKeyError unless remote_pubkey.size == Kademlia::PUBKEY_SIZE / 8

  cmd_id = decode_cmd_id message[97]
  cmd = REV_CMD_ID_MAP[cmd_id]

  payload = RLP.decode message[98..-1], strict: false
  raise InvalidPayloadError unless payload.instance_of?(Array)

  # ignore excessive list elements as required by EIP-8
  payload = payload[0, CMD_ELEM_COUNT_MAP[cmd]||payload.size]

  return remote_pubkey, cmd_id, payload, mdc
end