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[test] Add functional test to test early key response behaviour in BI…
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…P 324

- A node initiates a v2 connection by sending 64 bytes ellswift
- In BIP 324 "The responder waits until one byte is received which does not match the
  V1_PREFIX (16 bytes consisting of the network magic followed by "version\x00\x00\x00\x00\x00".)"
- It's possible that the 64 bytes ellswift sent by an initiator starts with a prefix of V1_PREFIX
- Example form of 64 bytes ellswift could be:
	4 bytes network magic + 60 bytes which aren't prefixed with remaining V1_PREFIX
- We test this behaviour:
	- when responder receives 4 byte network magic -> no response received by initiator
	- when first mismatch happens -> response received by initiator
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stratospher committed Jan 2, 2024
1 parent 689318c commit 42203f8
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85 changes: 85 additions & 0 deletions test/functional/p2p_v2_earlykeyresponse.py
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#!/usr/bin/env python3
# Copyright (c) 2022 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.

import random

from test_framework.test_framework import BitcoinTestFramework
from test_framework.crypto.ellswift import ellswift_create
from test_framework.p2p import P2PInterface
from test_framework.v2_p2p import EncryptedP2PState


class TestEncryptedP2PState(EncryptedP2PState):
""" Custom implementation of class EncryptedP2PState for testing purposes:
- if `send_net_magic` is True, send first 4 bytes of ellswift(match network magic) else send remaining 60 bytes
- `can_data_be_received` is a variable used to assert if data is received on recvbuf.
- v2 TestNode shouldn't respond back if we send V1_PREFIX and data shouldn't be received on recvbuf.
This state is represented using `can_data_be_received` = False.
- v2 TestNode responds back when mismatch from V1_PREFIX happens and data can be received on recvbuf.
This state is represented using `can_data_be_received` = True.
"""

def __init__(self):
super().__init__(initiating=True, net='regtest')
self.send_net_magic = True
self.can_data_be_received = False

def initiate_v2_handshake(self, garbage_len=random.randrange(4096)):
"""Initiator begins the v2 handshake by sending its ellswift bytes and garbage.
Here, the 64 bytes ellswift is assumed to have it's 4 bytes match network magic bytes. It is sent in 2 phases:
1. when `send_network_magic` = True, send first 4 bytes of ellswift (matches network magic bytes)
2. when `send_network_magic` = False, send remaining 60 bytes of ellswift
"""
if self.send_net_magic:
self.privkey_ours, self.ellswift_ours = ellswift_create()
self.sent_garbage = random.randbytes(garbage_len)
self.send_net_magic = False
return b"\xfa\xbf\xb5\xda"
else:
self.can_data_be_received = True
return self.ellswift_ours[4:] + self.sent_garbage


class PeerEarlyKey(P2PInterface):
def __init__(self):
super().__init__()
self.v2_state = None

def connection_made(self, transport):
"""Custom implementation so that 64 bytes ellswift is sent in 2 parts during `initial_v2_handshake()`"""
self.v2_state = TestEncryptedP2PState()
super().connection_made(transport)

def data_received(self, t):
# check that data can be received on recvbuf only when mismatch from V1_PREFIX happens (send_net_magic = False)
assert self.v2_state.can_data_be_received and not self.v2_state.send_net_magic


class P2PEarlyKey(BitcoinTestFramework):
def set_test_params(self):
self.num_nodes = 1
self.extra_args = [["-v2transport=1", "-peertimeout=3"]]

def run_test(self):
# testing BIP 324 "The responder waits until one byte is received which does not match the 16 bytes
# consisting of the network magic followed by "version\x00\x00\x00\x00\x00"."
self.log.info('Sending ellswift bytes in parts to ensure that response from responder is received only when')
self.log.info('ellswift bytes have a mismatch from the 16 bytes(network magic followed by "version\\x00\\x00\\x00\\x00\\x00")')
node0 = self.nodes[0]
self.log.info('Sending first 4 bytes of ellswift which match network magic')
self.log.info('If a response is received, assertion failure would happen in our custom data_received() function')
# send happens in `initiate_v2_handshake()` in `connection_made()`
peer1 = node0.add_p2p_connection(PeerEarlyKey(), wait_for_verack=False, supports_v2_p2p=True)
self.log.info('Sending remaining ellswift and garbage which are different from V1_PREFIX. Since a response is')
self.log.info('expected now, our custom data_received() function wouldn\'t result in assertion failure')
ellswift_and_garbage_data = peer1.v2_state.initiate_v2_handshake()
peer1.send_raw_message(ellswift_and_garbage_data)
peer1.wait_for_disconnect(timeout=5)
self.log.info('successful disconnection when MITM happens in the key exchange phase')


if __name__ == '__main__':
P2PEarlyKey().main()
1 change: 1 addition & 0 deletions test/functional/test_runner.py
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Expand Up @@ -260,6 +260,7 @@
'p2p_invalid_tx.py --v2transport',
'p2p_v2_transport.py',
'p2p_v2_encrypted.py',
'p2p_v2_earlykeyresponse.py',
'example_test.py',
'wallet_txn_doublespend.py --legacy-wallet',
'wallet_multisig_descriptor_psbt.py --descriptors',
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