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from contextlib import contextmanager
import random
import ssl
import struct
import time
import dns
import dns.message
import pytest
# default net.tcp_in_idle is 10s, TCP_DEFER_ACCEPT 3s, some extra for
# Python handling / edge cases
MAX_TIMEOUT = 16
def receive_answer(sock):
answer_total_len = 0
data = sock.recv(2)
if not data:
return None
answer_total_len = struct.unpack_from("!H", data)[0]
answer_received_len = 0
data_answer = b''
while answer_received_len < answer_total_len:
data_chunk = sock.recv(answer_total_len - answer_received_len)
if not data_chunk:
return None
data_answer += data_chunk
answer_received_len += len(data_answer)
return data_answer
def receive_parse_answer(sock):
data_answer = receive_answer(sock)
if data_answer is None:
raise BrokenPipeError("kresd closed connection")
msg_answer = dns.message.from_wire(data_answer, one_rr_per_rrset=True)
return msg_answer
def prepare_wire(
qname='localhost.',
qtype=dns.rdatatype.A,
qclass=dns.rdataclass.IN,
msgid=None):
"""Utility function to generate DNS wire format message"""
msg = dns.message.make_query(qname, qtype, qclass)
if msgid is not None:
msg.id = msgid
return msg.to_wire(), msg.id
def prepare_buffer(wire, datalen=None):
"""Utility function to prepare TCP buffer from DNS message in wire format"""
assert isinstance(wire, bytes)
if datalen is None:
datalen = len(wire)
return struct.pack("!H", datalen) + wire
def get_msgbuff(qname='localhost.', qtype=dns.rdatatype.A, msgid=None):
wire, msgid = prepare_wire(qname, qtype, msgid=msgid)
buff = prepare_buffer(wire)
return buff, msgid
def get_garbage(length):
return bytes(random.getrandbits(8) for _ in range(length))
def get_prefixed_garbage(length):
data = get_garbage(length)
return prepare_buffer(data)
def try_ping_alive(sock, msgid=None, close=False):
try:
ping_alive(sock, msgid)
except AssertionError:
return False
finally:
if close:
sock.close()
return True
def ping_alive(sock, msgid=None):
buff, msgid = get_msgbuff(msgid=msgid)
sock.sendall(buff)
answer = receive_parse_answer(sock)
assert answer.id == msgid
@contextmanager
def expect_kresd_close(rst_ok=False):
with pytest.raises(BrokenPipeError, message="kresd didn't close the connection"):
try:
time.sleep(0.2) # give kresd time to close connection with TCP FIN
yield
except ConnectionResetError:
if rst_ok:
raise BrokenPipeError
else:
pytest.skip("kresd closed connection with TCP RST")
def make_ssl_context(insecure=False, verify_location=None):
# set TLS v1.2+
context = ssl.SSLContext(ssl.PROTOCOL_TLS)
context.options |= ssl.OP_NO_SSLv2
context.options |= ssl.OP_NO_SSLv3
context.options |= ssl.OP_NO_TLSv1
context.options |= ssl.OP_NO_TLSv1_1
if insecure:
# turn off certificate verification
context.check_hostname = False
context.verify_mode = ssl.CERT_NONE
else:
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
if verify_location is not None:
context.load_verify_locations(verify_location)
return context
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