############################################################################
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.
############################################################################
############################################################################
# ans.py: See README.anspy for details.
############################################################################
from __future__ import print_function
import os
import sys
import signal
import socket
import select
from datetime import datetime, timedelta
import functools
import dns, dns.message, dns.query
from dns.rdatatype import *
from dns.rdataclass import *
from dns.rcode import *
from dns.name import *
############################################################################
# set up the RRs to be returned in the next answer
#
# the message contains up to two pipe-separated ('|') fields.
#
# the first field of the message is a comma-separated list
# of actions indicating what to put into the answer set
# (e.g., a dname, a cname, another cname, etc)
#
# supported actions:
# - cname (cname from the current name to a new one in the same domain)
# - dname (dname to a new domain, plus a synthesized cname)
# - xname ("external" cname, to a new name in a new domain)
#
# example: xname, dname, cname represents a CNAME to an external
# domain which is then answered by a DNAME and synthesized
# CNAME pointing to yet another domain, which is then answered
# by a CNAME within the same domain, and finally an answer
# to the query. each RR in the answer set has a corresponding
# RRSIG. these signatures are not valid, but will exercise the
# response parser.
#
# the second field is a comma-separated list of which RRs in the
# answer set to include in the answer, in which order. if prepended
# with 's', the number indicates which signature to include.
#
# examples: for the answer set "cname, cname, cname", an rr set
# '1, s1, 2, s2, 3, s3, 4, s4' indicates that all four RRs should
# be included in the answer, with siagntures, in the origninal
# order, while 4, s4, 3, s3, 2, s2, 1, s1' indicates the order
# should be reversed, 's3, s3, s3, s3' indicates that the third
# RRSIG should be repeated four times and everything else should
# be omitted, and so on.
#
# if there is no second field (i.e., no pipe symbol appears in
# the line) , the default is to send all answers and signatures.
# if a pipe symbol exists but the second field is empty, then
# nothing is sent at all.
############################################################################
actions = []
rrs = []
def ctl_channel(msg):
global actions, rrs
msg = msg.splitlines().pop(0)
print ('received control message: %s' % msg)
msg = msg.split(b'|')
if len(msg) == 0:
return
actions = [x.strip() for x in msg[0].split(b',')]
n = functools.reduce(lambda n, act: (n + (2 if act == b'dname' else 1)), [0] + actions)
if len(msg) == 1:
rrs = []
for i in range(n):
for b in [False, True]:
rrs.append((i, b))
return
rlist = [x.strip() for x in msg[1].split(b',')]
rrs = []
for item in rlist:
if item[0] == b's'[0]:
i = int(item[1:].strip()) - 1
if i > n:
print ('invalid index %d' + (i + 1))
continue
rrs.append((int(item[1:]) - 1, True))
else:
i = int(item) - 1
if i > n:
print ('invalid index %d' % (i + 1))
continue
rrs.append((i, False))
############################################################################
# Respond to a DNS query.
############################################################################
def create_response(msg):
m = dns.message.from_wire(msg)
qname = m.question[0].name.to_text()
labels = qname.lower().split('.')
wantsigs = True if m.ednsflags & dns.flags.DO else False
# get qtype
rrtype = m.question[0].rdtype
typename = dns.rdatatype.to_text(rrtype)
# for 'www.example.com.'...
# - name is 'www'
# - domain is 'example.com.'
# - sld is 'example'
# - tld is 'com.'
name = labels.pop(0)
domain = '.'.join(labels)
sld = labels.pop(0)
tld = '.'.join(labels)
print ('query: ' + qname + '/' + typename)
print ('domain: ' + domain)
# default answers, depending on QTYPE.
# currently only A, AAAA, TXT and NS are supported.
ttl = 86400
additionalA = '10.53.0.4'
additionalAAAA = 'fd92:7065:b8e:ffff::4'
if typename == 'A':
final = '10.53.0.4'
elif typename == 'AAAA':
final = 'fd92:7065:b8e:ffff::4'
elif typename == 'TXT':
final = 'Some\ text\ here'
elif typename == 'NS':
domain = qname
final = ('ns1.%s' % domain)
else:
final = None
# RRSIG rdata - won't validate but will exercise response parsing
t = datetime.now()
delta = timedelta(30)
t1 = t - delta
t2 = t + delta
inception=t1.strftime('%Y%m%d000000')
expiry=t2.strftime('%Y%m%d000000')
sigdata='OCXH2De0yE4NMTl9UykvOsJ4IBGs/ZIpff2rpaVJrVG7jQfmj50otBAp A0Zo7dpBU4ofv0N/F2Ar6LznCncIojkWptEJIAKA5tHegf/jY39arEpO cevbGp6DKxFhlkLXNcw7k9o7DSw14OaRmgAjXdTFbrl4AiAa0zAttFko Tso='
# construct answer set.
answers = []
sigs = []
curdom = domain
curname = name
i = 0
for action in actions:
if name != 'test':
continue
if action == b'xname':
owner = curname + '.' + curdom
newname = 'cname%d' % i
i += 1
newdom = 'domain%d.%s' % (i, tld)
i += 1
target = newname + '.' + newdom
print ('add external CNAME %s to %s' % (owner, target))
answers.append(dns.rrset.from_text(owner, ttl, IN, CNAME, target))
rrsig = 'CNAME 5 3 %d %s %s 12345 %s %s' % \
(ttl, expiry, inception, domain, sigdata)
print ('add external RRISG(CNAME) %s to %s' % (owner, target))
sigs.append(dns.rrset.from_text(owner, ttl, IN, RRSIG, rrsig))
curname = newname
curdom = newdom
continue
if action == b'cname':
owner = curname + '.' + curdom
newname = 'cname%d' % i
target = newname + '.' + curdom
i += 1
print ('add CNAME %s to %s' % (owner, target))
answers.append(dns.rrset.from_text(owner, ttl, IN, CNAME, target))
rrsig = 'CNAME 5 3 %d %s %s 12345 %s %s' % \
(ttl, expiry, inception, domain, sigdata)
print ('add RRSIG(CNAME) %s to %s' % (owner, target))
sigs.append(dns.rrset.from_text(owner, ttl, IN, RRSIG, rrsig))
curname = newname
continue
if action == b'dname':
owner = curdom
newdom = 'domain%d.%s' % (i, tld)
i += 1
print ('add DNAME %s to %s' % (owner, newdom))
answers.append(dns.rrset.from_text(owner, ttl, IN, DNAME, newdom))
rrsig = 'DNAME 5 3 %d %s %s 12345 %s %s' % \
(ttl, expiry, inception, domain, sigdata)
print ('add RRSIG(DNAME) %s to %s' % (owner, newdom))
sigs.append(dns.rrset.from_text(owner, ttl, IN, RRSIG, rrsig))
owner = curname + '.' + curdom
target = curname + '.' + newdom
print ('add synthesized CNAME %s to %s' % (owner, target))
answers.append(dns.rrset.from_text(owner, ttl, IN, CNAME, target))
rrsig = 'CNAME 5 3 %d %s %s 12345 %s %s' % \
(ttl, expiry, inception, domain, sigdata)
print ('add synthesized RRSIG(CNAME) %s to %s' % (owner, target))
sigs.append(dns.rrset.from_text(owner, ttl, IN, RRSIG, rrsig))
curdom = newdom
continue
# now add the final answer
owner = curname + '.' + curdom
answers.append(dns.rrset.from_text(owner, ttl, IN, rrtype, final))
rrsig = '%s 5 3 %d %s %s 12345 %s %s' % \
(typename, ttl, expiry, inception, domain, sigdata)
sigs.append(dns.rrset.from_text(owner, ttl, IN, RRSIG, rrsig))
# prepare the response and convert to wire format
r = dns.message.make_response(m)
if name != 'test':
r.answer.append(answers[-1])
if wantsigs:
r.answer.append(sigs[-1])
else:
for (i, sig) in rrs:
if sig and not wantsigs:
continue
elif sig:
r.answer.append(sigs[i])
else:
r.answer.append(answers[i])
if typename != 'NS':
r.authority.append(dns.rrset.from_text(domain, ttl, IN, "NS",
("ns1.%s" % domain)))
r.additional.append(dns.rrset.from_text(('ns1.%s' % domain), 86400,
IN, A, additionalA))
r.additional.append(dns.rrset.from_text(('ns1.%s' % domain), 86400,
IN, AAAA, additionalAAAA))
r.flags |= dns.flags.AA
r.use_edns()
return r.to_wire()
def sigterm(signum, frame):
print ("Shutting down now...")
os.remove('ans.pid')
running = False
sys.exit(0)
############################################################################
# Main
#
# Set up responder and control channel, open the pid file, and start
# the main loop, listening for queries on the query channel or commands
# on the control channel and acting on them.
############################################################################
ip4 = "10.53.0.4"
ip6 = "fd92:7065:b8e:ffff::4"
try: port=int(os.environ['PORT'])
except: port=5300
try: ctrlport=int(os.environ['EXTRAPORT1'])
except: ctrlport=5300
query4_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
query4_socket.bind((ip4, port))
havev6 = True
try:
query6_socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
try:
query6_socket.bind((ip6, port))
except:
query6_socket.close()
havev6 = False
except:
havev6 = False
ctrl_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ctrl_socket.bind((ip4, ctrlport))
ctrl_socket.listen(5)
signal.signal(signal.SIGTERM, sigterm)
f = open('ans.pid', 'w')
pid = os.getpid()
print (pid, file=f)
f.close()
running = True
print ("Listening on %s port %d" % (ip4, port))
if havev6:
print ("Listening on %s port %d" % (ip6, port))
print ("Control channel on %s port %d" % (ip4, ctrlport))
print ("Ctrl-c to quit")
if havev6:
input = [query4_socket, query6_socket, ctrl_socket]
else:
input = [query4_socket, ctrl_socket]
while running:
try:
inputready, outputready, exceptready = select.select(input, [], [])
except select.error as e:
break
except socket.error as e:
break
except KeyboardInterrupt:
break
for s in inputready:
if s == ctrl_socket:
# Handle control channel input
conn, addr = s.accept()
print ("Control channel connected")
while True:
msg = conn.recv(65535)
if not msg:
break
ctl_channel(msg)
conn.close()
if s == query4_socket or s == query6_socket:
print ("Query received on %s" %
(ip4 if s == query4_socket else ip6))
# Handle incoming queries
msg = s.recvfrom(65535)
rsp = create_response(msg[0])
if rsp:
s.sendto(rsp, msg[1])
if not running:
break