external-tests: add python implementation

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

contrib/external-tests/python/main.py

@@ -0,0 +1,94 @@
+#!/usr/bin/python3
+
+# SPDX-License-Identifier: MIT
+# Author: Piotr Lizonczyk <plizonczyk.public@gmail.com>
+
+import base64
+import datetime
+from hashlib import blake2s
+import socket
+import struct
+
+from scapy.layers.inet import IP, ICMP
+
+from noise.connection import NoiseConnection, Keypair
+
+
+address = ('demo.wireguard.com', 12913)
+
+our_private = base64.b64decode('WAmgVYXkbT2bCtdcDwolI88/iVi/aV3/PHcUBTQSYmo=')
+their_public = base64.b64decode('qRCwZSKInrMAq5sepfCdaCsRJaoLe5jhtzfiw7CjbwM=')
+preshared = base64.b64decode('FpCyhws9cxwWoV4xELtfJvjJN+zQVRPISllRWgeopVE=')
+prologue = b'WireGuard v1 zx2c4 Jason@zx2c4.com'
+
+noise = NoiseConnection.from_name(b'Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s')
+noise.set_as_initiator()
+noise.set_keypair_from_private_bytes(Keypair.STATIC, our_private)
+noise.set_keypair_from_public_bytes(Keypair.REMOTE_STATIC, their_public)
+noise.set_psks(psk=preshared)
+noise.set_prologue(prologue)
+noise.start_handshake()
+
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+
+# 1. Prepare and send handshake initiation packet
+now = datetime.datetime.now()
+tai = struct.pack('!qi', 4611686018427387914 + int(now.timestamp()), int(now.microsecond * 1e3))
+initiation_packet = b'\x01'  # Type: initiation
+initiation_packet += b'\x00' * 3  # Reserved
+initiation_packet += struct.pack('<i', 28)  # Sender index: 28 (arbitrary)
+initiation_packet += noise.write_message(payload=tai)
+mac_key = blake2s(b'mac1----' + their_public).digest()
+initiation_packet += blake2s(initiation_packet, digest_size=16, key=mac_key).digest()
+initiation_packet += b'\x00' * 16
+
+sock.sendto(initiation_packet, address)
+
+
+# 2. Receive response to finalize handshake
+response_packet = sock.recv(92)
+assert response_packet[0] == 2  # Type: response
+assert response_packet[1:4] == b'\x00' * 3  # Reserved
+their_index, our_index = struct.unpack('<ii', response_packet[4:12])
+assert our_index == 28
+payload = noise.read_message(response_packet[12:60])
+assert payload == b''
+assert noise.handshake_finished
+
+
+# 3. Prepare, encrypt and send ping packet
+icmp_packet = ICMP(type=8, id=921, seq=438)/b'WireGuard'
+ip_packet = IP(proto=1, ttl=20, src="10.189.129.2", dst="10.189.129.1", id=0)/icmp_packet
+ping_packet = b'\x04'  # Type: data
+ping_packet += b'\x00' * 3  # Reserved
+ping_packet += struct.pack('<iq', their_index, 0)
+ping_packet += noise.encrypt(bytes(ip_packet))
+
+sock.sendto(ping_packet, address)
+
+
+# 4. Retrieve ping response, decrypt and verify
+encrypted_response = sock.recv(80)
+assert encrypted_response[0] == 4  # Type: data
+assert encrypted_response[1:4] == b'\x00' * 3  # Reserved
+our_index, nonce = struct.unpack('<iq', encrypted_response[4:16])
+assert our_index == 28
+assert nonce == 0
+ip = IP(noise.decrypt(encrypted_response[16:]))
+icmp = ip[1]
+payload = ip[2]
+assert icmp.type == 0
+assert icmp.code == 0
+assert icmp.id == 921
+assert icmp.seq == 438
+assert payload.load == b'WireGuard'
+
+
+# 5. Send keepalive
+keepalive = b'\x04'  # Type: data
+keepalive += b'\x00' * 3  # Reserved
+keepalive += struct.pack('<iq', their_index, 1)
+keepalive += noise.encrypt(b'')
+
+sock.sendto(keepalive, address)