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DNSServer.py
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#!/usr/bin/env python
"""
Source:
http://code.google.com/p/minidns/source/browse/minidns
"""
"""
Header
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Query
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ QNAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QTYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QCLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
ResourceRecord
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ NAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TTL |
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| RDLENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
| |
/ RDATA /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Source: http://doc-tcpip.org/Dns/named.dns.message.html
"""
"""
prevent aTV update
Source: http://forum.xbmc.org/showthread.php?tid=93604
loopback to 127.0.0.1...
mesu.apple.com
appldnld.apple.com
appldnld.apple.com.edgesuite.net
"""
import os
import sys
import socket
import struct
from multiprocessing import Pipe # inter process communication
import signal
import Settings
from Debug import * # dprint()
CONFIG_PATH = "."
"""
Hostname/DNS conversion
Hostname: 'Hello.World'
DNSdata: '<len(Hello)>Hello<len(World)>World<NULL>
"""
def HostToDNS(Host):
DNSdata = '.'+Host+'\0' # python 2.6: bytearray()
i=0
while i<len(DNSdata)-1:
next = DNSdata.find('.',i+1)
if next==-1:
next = len(DNSdata)-1
DNSdata = DNSdata[:i] + chr(next-i-1) + DNSdata[i+1:] # python 2.6: DNSdata[i] = next-i-1
i = next
return DNSdata
def DNSToHost(DNSdata, i, followlink=True):
Host = ''
while DNSdata[i]!='\0':
nlen = ord(DNSdata[i])
if nlen & 0xC0:
if followlink:
Host = Host + DNSToHost(DNSdata, ((ord(DNSdata[i]) & 0x3F)<<8) + ord(DNSdata[i+1]) , True)+'.'
break
else:
Host = Host + DNSdata[i+1:i+nlen+1]+'.'
i+=nlen+1
Host = Host[:-1]
return Host
def printDNSdata(paket):
# HEADER
print "ID {0:04x}".format((ord(paket[0])<<8)+ord(paket[1]))
print "flags {0:02x} {1:02x}".format(ord(paket[2]), ord(paket[3]))
print "OpCode "+str((ord(paket[2])>>3)&0x0F)
print "RCode "+str((ord(paket[3])>>0)&0x0F)
qdcount = (ord(paket[4])<<8)+ord(paket[5])
ancount = (ord(paket[6])<<8)+ord(paket[7])
nscount = (ord(paket[8])<<8)+ord(paket[9])
arcount = (ord(paket[10])<<8)+ord(paket[11])
print "Count - QD, AN, NS, AR:", qdcount, ancount, nscount, arcount
adr = 12
# QDCOUNT (query)
for i in range(qdcount):
print "QUERY"
host = DNSToHost(paket, adr)
"""
for j in range(len(host)+2+4):
print ord(paket[adr+j]),
print
"""
adr = adr + len(host) + 2
print host
print "type "+str((ord(paket[adr+0])<<8)+ord(paket[adr+1]))
print "class "+str((ord(paket[adr+2])<<8)+ord(paket[adr+3]))
adr = adr + 4
# ANCOUNT (resource record)
for i in range(ancount):
print "ANSWER"
print ord(paket[adr])
if ord(paket[adr]) & 0xC0:
print"link"
adr = adr + 2
else:
host = DNSToHost(paket, adr)
adr = adr + len(host) + 2
print host
_type = (ord(paket[adr+0])<<8)+ord(paket[adr+1])
_class = (ord(paket[adr+2])<<8)+ord(paket[adr+3])
print "type, class: ", _type, _class
adr = adr + 4
print "ttl"
adr = adr + 4
rdlength = (ord(paket[adr+0])<<8)+ord(paket[adr+1])
print "rdlength", rdlength
adr = adr + 2
if _type==1:
print "IP:",
for j in range(rdlength):
print ord(paket[adr+j]),
print
elif _type==5:
print "redirect:", DNSToHost(paket, adr)
else:
print "type unsupported:",
for j in range(rdlength):
print ord(paket[adr+j]),
print
adr = adr + rdlength
def printDNSdata_raw(DNSdata):
# hex code
for i in range(len(DNSdata)):
if i % 16==0:
print
print "{0:02x}".format(ord(DNSdata[i])),
print
# printable characters
for i in range(len(DNSdata)):
if i % 16==0:
print
if (ord(DNSdata[i])>32) & (ord(DNSdata[i])<128):
print DNSdata[i],
else:
print ".",
print
def parseDNSdata(paket):
def getWord(DNSdata, addr):
return (ord(DNSdata[addr])<<8)+ord(DNSdata[addr+1])
DNSstruct = {}
adr = 0
# header
DNSstruct['head'] = { \
'id': getWord(paket, adr+0), \
'flags': getWord(paket, adr+2), \
'qdcnt': getWord(paket, adr+4), \
'ancnt': getWord(paket, adr+6), \
'nscnt': getWord(paket, adr+8), \
'arcnt': getWord(paket, adr+10) }
adr = adr + 12
# query
DNSstruct['query'] = []
for i in range(DNSstruct['head']['qdcnt']):
DNSstruct['query'].append({})
host_nolink = DNSToHost(paket, adr, followlink=False)
host_link = DNSToHost(paket, adr, followlink=True)
DNSstruct['query'][i]['host'] = host_link
adr = adr + len(host_nolink)+2
DNSstruct['query'][i]['type'] = getWord(paket, adr+0)
DNSstruct['query'][i]['class'] = getWord(paket, adr+2)
adr = adr + 4
# resource records
DNSstruct['resrc'] = []
for i in range(DNSstruct['head']['ancnt'] + DNSstruct['head']['nscnt'] + DNSstruct['head']['arcnt']):
DNSstruct['resrc'].append({})
host_nolink = DNSToHost(paket, adr, followlink=False)
host_link = DNSToHost(paket, adr, followlink=True)
DNSstruct['resrc'][i]['host'] = host_link
adr = adr + len(host_nolink)+2
DNSstruct['resrc'][i]['type'] = getWord(paket, adr+0)
DNSstruct['resrc'][i]['class'] = getWord(paket, adr+2)
DNSstruct['resrc'][i]['ttl'] = (getWord(paket, adr+4)<<16)+getWord(paket, adr+6)
DNSstruct['resrc'][i]['rdlen'] = getWord(paket, adr+8)
adr = adr + 10
DNSstruct['resrc'][i]['rdata'] = []
if DNSstruct['resrc'][i]['type']==5: # 5=redirect, evaluate name
host = DNSToHost(paket, adr, followlink=True)
DNSstruct['resrc'][i]['rdata'] = host
adr = adr + DNSstruct['resrc'][i]['rdlen']
DNSstruct['resrc'][i]['rdlen'] = len(host)
else: # 1=IP, ...
for j in range(DNSstruct['resrc'][i]['rdlen']):
DNSstruct['resrc'][i]['rdata'].append( paket[adr+j] )
adr = adr + DNSstruct['resrc'][i]['rdlen']
return DNSstruct
def encodeDNSstruct(DNSstruct):
def appendWord(DNSdata, val):
DNSdata.append((val>>8) & 0xFF)
DNSdata.append( val & 0xFF)
DNS = bytearray()
# header
appendWord(DNS, DNSstruct['head']['id'])
appendWord(DNS, DNSstruct['head']['flags'])
appendWord(DNS, DNSstruct['head']['qdcnt'])
appendWord(DNS, DNSstruct['head']['ancnt'])
appendWord(DNS, DNSstruct['head']['nscnt'])
appendWord(DNS, DNSstruct['head']['arcnt'])
# query
for i in range(DNSstruct['head']['qdcnt']):
host = HostToDNS(DNSstruct['query'][i]['host'])
DNS.extend(bytearray(host))
appendWord(DNS, DNSstruct['query'][i]['type'])
appendWord(DNS, DNSstruct['query'][i]['class'])
# resource records
for i in range(DNSstruct['head']['ancnt'] + DNSstruct['head']['nscnt'] + DNSstruct['head']['arcnt']):
host = HostToDNS(DNSstruct['resrc'][i]['host']) # no 'packing'/link - todo?
DNS.extend(bytearray(host))
appendWord(DNS, DNSstruct['resrc'][i]['type'])
appendWord(DNS, DNSstruct['resrc'][i]['class'])
appendWord(DNS, (DNSstruct['resrc'][i]['ttl']>>16) & 0xFFFF)
appendWord(DNS, (DNSstruct['resrc'][i]['ttl'] ) & 0xFFFF)
appendWord(DNS, DNSstruct['resrc'][i]['rdlen'])
if DNSstruct['resrc'][i]['type']==5: # 5=redirect, hostname
host = HostToDNS(DNSstruct['resrc'][i]['rdata'])
DNS.extend(bytearray(host))
else:
DNS.extend(DNSstruct['resrc'][i]['rdata'])
return DNS
def printDNSstruct(DNSstruct):
for i in range(DNSstruct['head']['qdcnt']):
print "query:", DNSstruct['query'][i]['host']
for i in range(DNSstruct['head']['ancnt'] + DNSstruct['head']['nscnt'] + DNSstruct['head']['arcnt']):
print "resrc:",
print DNSstruct['resrc'][i]['host']
if DNSstruct['resrc'][i]['type']==1:
print "->IP:",
for j in range(DNSstruct['resrc'][i]['rdlen']):
print ord(DNSstruct['resrc'][i]['rdata'][j]),
print
elif DNSstruct['resrc'][i]['type']==5:
print "->alias:", DNSstruct['resrc'][i]['rdata']
else:
print "->unknown type"
def Run(cmdPipe, param):
if not __name__ == '__main__':
signal.signal(signal.SIGINT, signal.SIG_IGN)
dinit(__name__, param) # init logging, DNSServer process
cfg_IP_self = param['IP_self']
cfg_Port_DNSServer = param['CSettings'].getSetting('port_dnsserver')
cfg_IP_DNSMaster = param['CSettings'].getSetting('ip_dnsmaster')
try:
DNS = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
DNS.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
DNS.settimeout(5.0)
DNS.bind((cfg_IP_self, int(cfg_Port_DNSServer)))
except Exception, e:
dprint(__name__, 0, "Failed to create socket on UDP port {0}: {1}", cfg_Port_DNSServer, e)
sys.exit(1)
intercept = [param['HostToIntercept']]
restrain = []
if param['CSettings'].getSetting('use_custom_dns_bind_ip') == "True":
cfg_IP_self = param['CSettings'].getSetting('custom_dns_bind_ip')
else:
cfg_IP_self = param['IP_self']
if param['CSettings'].getSetting('intercept_atv_icon')=='True':
intercept.append('a1.phobos.apple.com')
dprint(__name__, 0, "Intercept Atv Icon: Enabled")
if param['CSettings'].getSetting('prevent_atv_update')=='True':
restrain = ['mesu.apple.com', 'appldnld.apple.com', 'appldnld.apple.com.edgesuite.net']
dprint(__name__, 0, "Prevent Atv Update: Enabled")
dprint(__name__, 0, "***")
dprint(__name__, 0, "DNSServer: Serving DNS on {0} port {1}.", cfg_IP_self, cfg_Port_DNSServer)
dprint(__name__, 1, "intercept: {0} => {1}", intercept, cfg_IP_self)
dprint(__name__, 1, "restrain: {0} => 127.0.0.1", restrain)
dprint(__name__, 1, "forward other to higher level DNS: "+cfg_IP_DNSMaster)
dprint(__name__, 0, "***")
try:
while True:
# check command
if cmdPipe.poll():
cmd = cmdPipe.recv()
if cmd=='shutdown':
break
# do your work (with timeout)
try:
data, addr = DNS.recvfrom(1024)
dprint(__name__, 1, "DNS request received!")
dprint(__name__, 1, "Source: "+str(addr))
#print "incoming:"
#printDNSdata(data)
# analyse DNS request
# todo: how about multi-query messages?
opcode = (ord(data[2]) >> 3) & 0x0F # Opcode bits (query=0, inversequery=1, status=2)
if opcode == 0: # Standard query
domain = DNSToHost(data, 12)
dprint(__name__, 1, "Domain: "+domain)
paket=''
if domain in intercept:
dprint(__name__, 1, "***intercept request")
paket+=data[:2] # 0:1 - ID
paket+="\x81\x80" # 2:3 - flags
paket+=data[4:6] # 4:5 - QDCOUNT - should be 1 for this code
paket+=data[4:6] # 6:7 - ANCOUNT
paket+='\x00\x00' # 8:9 - NSCOUNT
paket+='\x00\x00' # 10:11 - ARCOUNT
paket+=data[12:] # original query
paket+='\xc0\x0c' # pointer to domain name/original query
paket+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04' # response type, ttl and resource data length -> 4 bytes
paket+=str.join('',map(lambda x: chr(int(x)), cfg_IP_self.split('.'))) # 4bytes of IP
dprint(__name__, 1, "-> DNS response: "+cfg_IP_self)
elif domain in restrain:
dprint(__name__, 1, "***restrain request")
paket+=data[:2] # 0:1 - ID
paket+="\x81\x80" # 2:3 - flags
paket+=data[4:6] # 4:5 - QDCOUNT - should be 1 for this code
paket+=data[4:6] # 6:7 - ANCOUNT
paket+='\x00\x00' # 8:9 - NSCOUNT
paket+='\x00\x00' # 10:11 - ARCOUNT
paket+=data[12:] # original query
paket+='\xc0\x0c' # pointer to domain name/original query
paket+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04' # response type, ttl and resource data length -> 4 bytes
paket+='\x7f\x00\x00\x01' # 4bytes of IP - 127.0.0.1, loopback
dprint(__name__, 1, "-> DNS response: "+cfg_IP_self)
else:
dprint(__name__, 1, "***forward request")
try:
DNS_forward = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
DNS_forward.settimeout(5.0)
except Exception, e:
dprint(__name__, 0, "Failed to create socket for DNS_forward): {0}", e)
continue
DNS_forward.sendto(data, (cfg_IP_DNSMaster, 53))
paket, addr_master = DNS_forward.recvfrom(1024)
DNS_forward.close()
# todo: double check: ID has to be the same!
# todo: spawn thread to wait in parallel
dprint(__name__, 1, "-> DNS response from higher level")
#print "-> respond back:"
#printDNSdata(paket)
# todo: double check: ID has to be the same!
DNS.sendto(paket, addr)
except socket.timeout:
pass
except socket.error as e:
dprint(__name__, 1, "Warning: DNS error ({0}): {1}", e.errno, e.strerror)
except KeyboardInterrupt:
signal.signal(signal.SIGINT, signal.SIG_IGN) # we heard you!
dprint(__name__, 0, "^C received.")
finally:
dprint(__name__, 0, "Shutting down.")
DNS.close()
if __name__ == '__main__':
cmdPipe = Pipe()
cfg = Settings.CSettings(CONFIG_PATH)
param = {}
param['CSettings'] = cfg
param['IP_self'] = os.getenv("IP_SELF", "192.168.1.18")
param['baseURL'] = 'http://'+ param['IP_self'] +':'+ cfg.getSetting('port_webserver')
param['HostToIntercept'] = cfg.getSetting('hosttointercept')
Run(cmdPipe[1], param)