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"""TCP Connection Management tests - prefix length
RFC1035
4.2.2. TCP usage
The message is prefixed with a two byte length field which gives the message
length, excluding the two byte length field.
The following test suite focuses on edge cases for the prefix - when it
is either too short or too long, instead of matching the length of DNS
message exactly.
"""
import time
import pytest
import utils
@pytest.fixture(params=[
'no_query_before',
'query_before',
'query_before_in_single_buffer',
])
def send_query(request):
"""Function sends a buffer, either by itself, or with a valid query before.
If a valid query is sent before, it can be sent either in a separate buffer, or
along with the provided buffer."""
# pylint: disable=possibly-unused-variable
def no_query_before(sock, buff): # pylint: disable=unused-argument
sock.sendall(buff)
def query_before(sock, buff, single_buffer=False):
"""Send an initial query and expect a response."""
msg_buff, msgid = utils.get_msgbuff()
if single_buffer:
sock.sendall(msg_buff + buff)
else:
sock.sendall(msg_buff)
sock.sendall(buff)
answer = utils.receive_parse_answer(sock)
assert answer.id == msgid
def query_before_in_single_buffer(sock, buff):
return query_before(sock, buff, single_buffer=True)
return locals()[request.param]
@pytest.mark.parametrize('datalen', [
1, # just one byte of DNS header
11, # DNS header size minus 1
14, # DNS Header size plus 2
])
def test_prefix_cuts_message(kresd_sock, datalen, send_query):
"""Prefix is shorter than the DNS message."""
wire, _ = utils.prepare_wire()
assert datalen < len(wire)
invalid_buff = utils.prepare_buffer(wire, datalen)
send_query(kresd_sock, invalid_buff) # buffer breaks parsing of TCP stream
with utils.expect_kresd_close():
utils.ping_alive(kresd_sock)
def test_prefix_greater_than_message(kresd_sock, send_query):
"""Prefix is greater than the length of the entire DNS message."""
wire, invalid_msgid = utils.prepare_wire()
datalen = len(wire) + 16
invalid_buff = utils.prepare_buffer(wire, datalen)
send_query(kresd_sock, invalid_buff)
valid_buff, _ = utils.get_msgbuff()
kresd_sock.sendall(valid_buff)
# invalid_buff is answered (treats additional data as trailing garbage)
answer = utils.receive_parse_answer(kresd_sock)
assert answer.id == invalid_msgid
# parsing stream is broken by the invalid_buff, valid query is never answered
with utils.expect_kresd_close():
utils.receive_parse_answer(kresd_sock)
@pytest.mark.parametrize('glength', [
0,
1,
8,
1024,
4096,
20000,
])
def test_prefix_trailing_garbage(kresd_sock, glength, query_before):
"""Send messages with trailing garbage (its length included in prefix)."""
if query_before:
utils.ping_alive(kresd_sock)
for _ in range(10):
wire, msgid = utils.prepare_wire()
wire += utils.get_garbage(glength)
buff = utils.prepare_buffer(wire)
kresd_sock.sendall(buff)
answer = utils.receive_parse_answer(kresd_sock)
assert answer.id == msgid
time.sleep(0.1)
|
