1#!/usr/bin/env python3
2# Copyright (c) 2015-2019 The Bitcoin Core developers
3# Distributed under the MIT software license, see the accompanying
4# file COPYING or http://www.opensource.org/licenses/mit-license.php.
5"""Test node responses to invalid network messages."""
6import asyncio
7import struct
8import sys
9
10from test_framework import messages
11from test_framework.mininode import P2PDataStore, NetworkThread
12from test_framework.test_framework import BitcoinTestFramework
13
14from test_framework.qtumconfig import FACTOR_REDUCED_BLOCK_TIME
15
16class msg_unrecognized:
17    """Nonsensical message. Modeled after similar types in test_framework.messages."""
18
19    command = b'badmsg'
20
21    def __init__(self, *, str_data):
22        self.str_data = str_data.encode() if not isinstance(str_data, bytes) else str_data
23
24    def serialize(self):
25        return messages.ser_string(self.str_data)
26
27    def __repr__(self):
28        return "{}(data={})".format(self.command, self.str_data)
29
30
31class InvalidMessagesTest(BitcoinTestFramework):
32    def set_test_params(self):
33        self.num_nodes = 1
34        self.setup_clean_chain = True
35
36    def run_test(self):
37        """
38         . Test msg header
39        0. Send a bunch of large (4MB) messages of an unrecognized type. Check to see
40           that it isn't an effective DoS against the node.
41
42        1. Send an oversized (4MB+) message and check that we're disconnected.
43
44        2. Send a few messages with an incorrect data size in the header, ensure the
45           messages are ignored.
46        """
47        self.test_magic_bytes()
48        self.test_checksum()
49        self.test_size()
50        self.test_command()
51
52        node = self.nodes[0]
53        self.node = node
54        node.add_p2p_connection(P2PDataStore())
55        conn2 = node.add_p2p_connection(P2PDataStore())
56
57        msg_limit = 8 * 1000 * 1000 // FACTOR_REDUCED_BLOCK_TIME  # 4MB, per MAX_PROTOCOL_MESSAGE_LENGTH
58        valid_data_limit = msg_limit - 5  # Account for the 4-byte length prefix
59
60        #
61        # 0.
62        #
63        # Send as large a message as is valid, ensure we aren't disconnected but
64        # also can't exhaust resources.
65        #
66        msg_at_size = msg_unrecognized(str_data="b" * valid_data_limit)
67        assert len(msg_at_size.serialize()) == msg_limit
68
69        self.log.info("Sending a bunch of large, junk messages to test memory exhaustion. May take a bit...")
70
71        # Run a bunch of times to test for memory exhaustion.
72        for _ in range(80):
73            node.p2p.send_message(msg_at_size)
74
75        # Check that, even though the node is being hammered by nonsense from one
76        # connection, it can still service other peers in a timely way.
77        for _ in range(20):
78            conn2.sync_with_ping(timeout=2)
79
80        # Peer 1, despite serving up a bunch of nonsense, should still be connected.
81        self.log.info("Waiting for node to drop junk messages.")
82        node.p2p.sync_with_ping(timeout=400)
83        assert node.p2p.is_connected
84
85        #
86        # 1.
87        #
88        # Send an oversized message, ensure we're disconnected.
89        #
90        # Under macOS this test is skipped due to an unexpected error code
91        # returned from the closing socket which python/asyncio does not
92        # yet know how to handle.
93        #
94        if sys.platform != 'darwin':
95            msg_over_size = msg_unrecognized(str_data="b" * (valid_data_limit + 1))
96            assert len(msg_over_size.serialize()) == (msg_limit + 1)
97
98            # An unknown message type (or *any* message type) over
99            # MAX_PROTOCOL_MESSAGE_LENGTH should result in a disconnect.
100            node.p2p.send_message(msg_over_size)
101            node.p2p.wait_for_disconnect(timeout=4)
102
103            node.disconnect_p2ps()
104            conn = node.add_p2p_connection(P2PDataStore())
105            conn.wait_for_verack()
106        else:
107            self.log.info("Skipping test p2p_invalid_messages/1 (oversized message) under macOS")
108
109        #
110        # 2.
111        #
112        # Send messages with an incorrect data size in the header.
113        #
114        actual_size = 100
115        msg = msg_unrecognized(str_data="b" * actual_size)
116
117        # TODO: handle larger-than cases. I haven't been able to pin down what behavior to expect.
118        for wrong_size in (2, 77, 78, 79):
119            self.log.info("Sending a message with incorrect size of {}".format(wrong_size))
120
121            # Unmodified message should submit okay.
122            node.p2p.send_and_ping(msg)
123
124            # A message lying about its data size results in a disconnect when the incorrect
125            # data size is less than the actual size.
126            #
127            # TODO: why does behavior change at 78 bytes?
128            #
129            node.p2p.send_raw_message(self._tweak_msg_data_size(msg, wrong_size))
130
131            # For some reason unknown to me, we sometimes have to push additional data to the
132            # peer in order for it to realize a disconnect.
133            try:
134                node.p2p.send_message(messages.msg_ping(nonce=123123))
135            except IOError:
136                pass
137
138            node.p2p.wait_for_disconnect(timeout=10)
139            node.disconnect_p2ps()
140            node.add_p2p_connection(P2PDataStore())
141
142        # Node is still up.
143        conn = node.add_p2p_connection(P2PDataStore())
144
145    def test_magic_bytes(self):
146        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
147
148        async def swap_magic_bytes():
149            conn._on_data = lambda: None  # Need to ignore all incoming messages from now, since they come with "invalid" magic bytes
150            conn.magic_bytes = b'\x00\x11\x22\x32'
151
152        # Call .result() to block until the atomic swap is complete, otherwise
153        # we might run into races later on
154        asyncio.run_coroutine_threadsafe(swap_magic_bytes(), NetworkThread.network_event_loop).result()
155
156        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART ping']):
157            conn.send_message(messages.msg_ping(nonce=0xff))
158            conn.wait_for_disconnect(timeout=1)
159            self.nodes[0].disconnect_p2ps()
160
161    def test_checksum(self):
162        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
163        with self.nodes[0].assert_debug_log(['CHECKSUM ERROR (badmsg, 2 bytes), expected 78df0a04 was ffffffff']):
164            msg = conn.build_message(msg_unrecognized(str_data="d"))
165            cut_len = (
166                4 +  # magic
167                12 +  # command
168                4  #len
169            )
170            # modify checksum
171            msg = msg[:cut_len] + b'\xff' * 4 + msg[cut_len + 4:]
172            self.nodes[0].p2p.send_raw_message(msg)
173            conn.sync_with_ping(timeout=1)
174            self.nodes[0].disconnect_p2ps()
175
176    def test_size(self):
177        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
178        with self.nodes[0].assert_debug_log(['']):
179            msg = conn.build_message(msg_unrecognized(str_data="d"))
180            cut_len = (
181                4 +  # magic
182                12  # command
183            )
184            # modify len to MAX_SIZE + 1
185            msg = msg[:cut_len] + struct.pack("<I", 0x02000000 + 1) + msg[cut_len + 4:]
186            self.nodes[0].p2p.send_raw_message(msg)
187            conn.wait_for_disconnect(timeout=1)
188            self.nodes[0].disconnect_p2ps()
189
190    def test_command(self):
191        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
192        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
193            msg = msg_unrecognized(str_data="d")
194            msg.command = b'\xff' * 12
195            msg = conn.build_message(msg)
196            # Modify command
197            msg = msg[:7] + b'\x00' + msg[7 + 1:]
198            self.nodes[0].p2p.send_raw_message(msg)
199            conn.sync_with_ping(timeout=1)
200            self.nodes[0].disconnect_p2ps()
201
202    def _tweak_msg_data_size(self, message, wrong_size):
203        """
204        Return a raw message based on another message but with an incorrect data size in
205        the message header.
206        """
207        raw_msg = self.node.p2p.build_message(message)
208
209        bad_size_bytes = struct.pack("<I", wrong_size)
210        num_header_bytes_before_size = 4 + 12
211
212        # Replace the correct data size in the message with an incorrect one.
213        raw_msg_with_wrong_size = (
214            raw_msg[:num_header_bytes_before_size] +
215            bad_size_bytes +
216            raw_msg[(num_header_bytes_before_size + len(bad_size_bytes)):]
217        )
218        assert len(raw_msg) == len(raw_msg_with_wrong_size)
219
220        return raw_msg_with_wrong_size
221
222
223if __name__ == '__main__':
224    InvalidMessagesTest().main()
225