text: #!/usr/bin/env python3
  # Copyright (c) 2015-2020 The Bitcoin Core developers
  # Distributed under the MIT software license, see the accompanying
  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  """Test node responses to invalid network messages."""
  import asyncio
  import struct
  import sys
  
  from test_framework import messages
  from test_framework.mininode import (
      NetworkThread,
      P2PDataStore,
      P2PInterface,
  )
  from test_framework.test_framework import BitcoinTestFramework
  
  
  class msg_unrecognized:
      """Nonsensical message. Modeled after similar types in test_framework.messages."""
  
      command = b'badmsg'
  
      def __init__(self, *, str_data):
          self.str_data = str_data.encode() if not isinstance(str_data, bytes) else str_data
  
      def serialize(self):
          return messages.ser_string(self.str_data)
  
      def __repr__(self):
          return "{}(data={})".format(self.command, self.str_data)
  
  
  class InvalidMessagesTest(BitcoinTestFramework):
      def set_test_params(self):
          self.num_nodes = 1
          self.setup_clean_chain = True
  
      def run_test(self):
          """
           . Test msg header
          0. Send a bunch of large (4MB) messages of an unrecognized type. Check to see
             that it isn't an effective DoS against the node.
  
          1. Send an oversized (4MB+) message and check that we're disconnected.
  
          2. Send a few messages with an incorrect data size in the header, ensure the
             messages are ignored.
          """
          self.test_magic_bytes()
          self.test_checksum()
          self.test_size()
          self.test_command()
          self.test_large_inv()
  
          node = self.nodes[0]
          self.node = node
          node.add_p2p_connection(P2PDataStore())
          conn2 = node.add_p2p_connection(P2PDataStore())
  
          msg_limit = 4 * 1000 * 1000  # 4MB, per MAX_PROTOCOL_MESSAGE_LENGTH
          valid_data_limit = msg_limit - 5  # Account for the 4-byte length prefix
  
          #
          # 0.
          #
          # Send as large a message as is valid, ensure we aren't disconnected but
          # also can't exhaust resources.
          #
          msg_at_size = msg_unrecognized(str_data="b" * valid_data_limit)
          assert len(msg_at_size.serialize()) == msg_limit
  
          self.log.info("Sending a bunch of large, junk messages to test memory exhaustion. May take a bit...")
  
          # Run a bunch of times to test for memory exhaustion.
          for _ in range(80):
              node.p2p.send_message(msg_at_size)
  
          # Check that, even though the node is being hammered by nonsense from one
          # connection, it can still service other peers in a timely way.
          for _ in range(20):
              conn2.sync_with_ping(timeout=2)
  
          # Peer 1, despite serving up a bunch of nonsense, should still be connected.
          self.log.info("Waiting for node to drop junk messages.")
          node.p2p.sync_with_ping(timeout=400)
          assert node.p2p.is_connected
  
          #
          # 1.
          #
          # Send an oversized message, ensure we're disconnected.
          #
          # Under macOS this test is skipped due to an unexpected error code
          # returned from the closing socket which python/asyncio does not
          # yet know how to handle.
          #
          if sys.platform != 'darwin':
              msg_over_size = msg_unrecognized(str_data="b" * (valid_data_limit + 1))
              assert len(msg_over_size.serialize()) == (msg_limit + 1)
  
              # An unknown message type (or *any* message type) over
              # MAX_PROTOCOL_MESSAGE_LENGTH should result in a disconnect.
              node.p2p.send_message(msg_over_size)
              node.p2p.wait_for_disconnect(timeout=4)
  
              node.disconnect_p2ps()
              conn = node.add_p2p_connection(P2PDataStore())
              conn.wait_for_verack()
          else:
              self.log.info("Skipping test p2p_invalid_messages/1 (oversized message) under macOS")
  
          #
          # 2.
          #
          # Send messages with an incorrect data size in the header.
          #
          actual_size = 100
          msg = msg_unrecognized(str_data="b" * actual_size)
  
          # TODO: handle larger-than cases. I haven't been able to pin down what behavior to expect.
          for wrong_size in (2, 77, 78, 79):
              self.log.info("Sending a message with incorrect size of {}".format(wrong_size))
  
              # Unmodified message should submit okay.
              node.p2p.send_and_ping(msg)
  
              # A message lying about its data size results in a disconnect when the incorrect
              # data size is less than the actual size.
              #
              # TODO: why does behavior change at 78 bytes?
              #
              node.p2p.send_raw_message(self._tweak_msg_data_size(msg, wrong_size))
  
              # For some reason unknown to me, we sometimes have to push additional data to the
              # peer in order for it to realize a disconnect.
              try:
                  node.p2p.send_message(messages.msg_ping(nonce=123123))
              except IOError:
                  pass
  
              node.p2p.wait_for_disconnect(timeout=10)
              node.disconnect_p2ps()
              node.add_p2p_connection(P2PDataStore())
  
          # Node is still up.
          conn = node.add_p2p_connection(P2PDataStore())
  
      def test_magic_bytes(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
  
          async def swap_magic_bytes():
              conn._on_data = lambda: None  # Need to ignore all incoming messages from now, since they come with "invalid" magic bytes
              conn.magic_bytes = b'\x00\x11\x22\x32'
  
          # Call .result() to block until the atomic swap is complete, otherwise
          # we might run into races later on
          asyncio.run_coroutine_threadsafe(swap_magic_bytes(), NetworkThread.network_event_loop).result()
  
          with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART ping']):
              conn.send_message(messages.msg_ping(nonce=0xff))
              conn.wait_for_disconnect(timeout=1)
              self.nodes[0].disconnect_p2ps()
  
      def test_checksum(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
          with self.nodes[0].assert_debug_log(['CHECKSUM ERROR (badmsg, 2 bytes), expected 78df0a04 was ffffffff']):
              msg = conn.build_message(msg_unrecognized(str_data="d"))
              cut_len = (
                  4 +  # magic
                  12 +  # command
                  4  #len
              )
              # modify checksum
              msg = msg[:cut_len] + b'\xff' * 4 + msg[cut_len + 4:]
              self.nodes[0].p2p.send_raw_message(msg)
              conn.sync_with_ping(timeout=1)
              self.nodes[0].disconnect_p2ps()
  
      def test_size(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
          with self.nodes[0].assert_debug_log(['']):
              msg = conn.build_message(msg_unrecognized(str_data="d"))
              cut_len = (
                  4 +  # magic
                  12  # command
              )
              # modify len to MAX_SIZE + 1
              msg = msg[:cut_len] + struct.pack("<I", 0x02000000 + 1) + msg[cut_len + 4:]
              self.nodes[0].p2p.send_raw_message(msg)
              conn.wait_for_disconnect(timeout=1)
              self.nodes[0].disconnect_p2ps()
  
      def test_command(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
          with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
              msg = msg_unrecognized(str_data="d")
              msg.command = b'\xff' * 12
              msg = conn.build_message(msg)
              # Modify command
              msg = msg[:7] + b'\x00' + msg[7 + 1:]
              self.nodes[0].p2p.send_raw_message(msg)
              conn.sync_with_ping(timeout=1)
              self.nodes[0].disconnect_p2ps()
  
      def test_large_inv(self):
          conn = self.nodes[0].add_p2p_connection(P2PInterface())
          with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=4 (0 -> 20): message inv size() = 50001']):
              msg = messages.msg_inv([messages.CInv(1, 1)] * 50001)
              conn.send_and_ping(msg)
          with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=4 (20 -> 40): message getdata size() = 50001']):
              msg = messages.msg_getdata([messages.CInv(1, 1)] * 50001)
              conn.send_and_ping(msg)
          with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=4 (40 -> 60): headers message size = 2001']):
              msg = messages.msg_headers([messages.CBlockHeader()] * 2001)
              conn.send_and_ping(msg)
          self.nodes[0].disconnect_p2ps()
  
      def _tweak_msg_data_size(self, message, wrong_size):
          """
          Return a raw message based on another message but with an incorrect data size in
          the message header.
          """
          raw_msg = self.node.p2p.build_message(message)
  
          bad_size_bytes = struct.pack("<I", wrong_size)
          num_header_bytes_before_size = 4 + 12
  
          # Replace the correct data size in the message with an incorrect one.
          raw_msg_with_wrong_size = (
              raw_msg[:num_header_bytes_before_size] +
              bad_size_bytes +
              raw_msg[(num_header_bytes_before_size + len(bad_size_bytes)):]
          )
          assert len(raw_msg) == len(raw_msg_with_wrong_size)
  
          return raw_msg_with_wrong_size
  
  
  if __name__ == '__main__':
      InvalidMessagesTest().main()
  