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."""
  from test_framework.messages import (
      CBlockHeader,
      CInv,
      msg_getdata,
      msg_headers,
      msg_inv,
      MSG_TX,
      ser_string,
  )
  from test_framework.mininode import (
      P2PDataStore,
      P2PInterface,
  )
  from test_framework.test_framework import BitcoinTestFramework
  
  MSG_LIMIT = 4 * 1000 * 1000  # 4MB, per MAX_PROTOCOL_MESSAGE_LENGTH
  VALID_DATA_LIMIT = MSG_LIMIT - 5  # Account for the 5-byte length prefix
  
  class msg_unrecognized:
      """Nonsensical message. Modeled after similar types in test_framework.messages."""
  
      msgtype = 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 ser_string(self.str_data)
  
      def __repr__(self):
          return "{}(data={})".format(self.msgtype, self.str_data)
  
  
  class InvalidMessagesTest(BitcoinTestFramework):
      def set_test_params(self):
          self.num_nodes = 1
          self.setup_clean_chain = True
  
      def run_test(self):
          self.test_magic_bytes()
          self.test_checksum()
          self.test_size()
          self.test_msgtype()
          self.test_large_inv()
          self.test_resource_exhaustion()
  
      def test_magic_bytes(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
          with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART badmsg']):
              msg = conn.build_message(msg_unrecognized(str_data="d"))
              # modify magic bytes
              msg = b'\xff' * 4 + msg[4:]
              conn.send_raw_message(msg)
              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"))
              # Checksum is after start bytes (4B), message type (12B), len (4B)
              cut_len = 4 + 12 + 4
              # 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(['']):
              # Create a message with oversized payload
              msg = msg_unrecognized(str_data="d" * (VALID_DATA_LIMIT + 1))
              msg = conn.build_message(msg)
              self.nodes[0].p2p.send_raw_message(msg)
              conn.wait_for_disconnect(timeout=1)
              self.nodes[0].disconnect_p2ps()
  
      def test_msgtype(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.msgtype = b'\xff' * 12
              msg = conn.build_message(msg)
              # Modify msgtype
              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 = msg_inv([CInv(MSG_TX, 1)] * 50001)
              conn.send_and_ping(msg)
          with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=4 (20 -> 40): message getdata size() = 50001']):
              msg = msg_getdata([CInv(MSG_TX, 1)] * 50001)
              conn.send_and_ping(msg)
          with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=4 (40 -> 60): headers message size = 2001']):
              msg = msg_headers([CBlockHeader()] * 2001)
              conn.send_and_ping(msg)
          self.nodes[0].disconnect_p2ps()
  
      def test_resource_exhaustion(self):
          conn = self.nodes[0].add_p2p_connection(P2PDataStore())
          conn2 = self.nodes[0].add_p2p_connection(P2PDataStore())
          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):
              conn.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 being served up a bunch of nonsense, should still be connected.
          self.log.info("Waiting for node to drop junk messages.")
          conn.sync_with_ping(timeout=400)
          assert conn.is_connected
          self.nodes[0].disconnect_p2ps()
  
  
  if __name__ == '__main__':
      InvalidMessagesTest().main()
  