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vor 8 Jahren
#!/usr/bin/env /usr/bin/python
# Why don't people use shebangs anymore. It's muppetry I say
# -*- coding: utf-8 -*-
"""
FileResolver - example resolver which responds with fixed response
to all requests
"""
from __future__ import print_function
import copy
import os
import os.path
import base64
import time
from dnslib import RR, QTYPE, TXT, CLASS, RCODE
from dnslib.server import DNSServer,DNSHandler,BaseResolver,DNSLogger
from dnslib.label import DNSLabel
class FileResolver(BaseResolver):
"""
Respond with fixed response to all requests
"""
def __init__(self,directory,domain):
self.filelist=[]
self.domain=domain
self.ttl=60
self.directory=directory
self.cache={}
if directory:
if not os.path.isdir(directory):
print("Directory " + directory + " doesn't exist")
exit()
def getcache(self,path):
cooked=""
pname=os.path.basename(path);
if pname in self.cache:
# it's in the cache - so lets just read it from the cache
print("Taking from cache")
cooked=self.cache[pname]["base64"]
# And update time
self.cache[pname]["time"]=time.time()
else:
# It's not in cache - read the file and cache it
print("Adding to cache")
fin=open(path,"rb")
raw=fin.read()
fin.close()
cooked=base64.b64encode(raw)
self.cache[pname]={}
self.cache[pname]["base64"]=cooked
self.cache[pname]["time"]=time.time()
self.cachecheck()
return cooked
def cachecheck(self):
# Remove any entries in the cache over an hour old
curtime = time.time()
staletime = 3600
for key in self.cache:
if curtime-self.cache[key]["time"] > staletime:
# it's stale
del self.cache[key]
def resolve(self,request,handler):
type=QTYPE[request.q.qtype]
name=request.q.qname
reply = request.reply()
if type == "TXT":
# Check for Chaos stuff first
if request.q.qclass == CLASS.CH:
if name == "version.bind":
reply.add_answer(*RR.fromZone('version.bind 60 CH TXT "Uninvited Guest 0.3"'))
if name == "authors.bind":
reply.add_answer(*RR.fromZone('authors.bind 60 CH TXT "David Lodge"'))
reply.add_answer(*RR.fromZone('authors.bind 60 CH TXT "Ian Williams"'))
if not reply.rr:
reply.header.rcode = RCODE.NXDOMAIN
return reply
# Format is filename.count.domain for count
# First check domain is at the end of the name
if not name.matchSuffix(self.domain):
reply.add_answer(RR(name, QTYPE.TXT, ttl=self.ttl,
rdata=TXT("Domain not found")))
return reply
# Now look whether we're looking for a count or a part
parts=str(name.stripSuffix(self.domain)).split(".")
# parts[0] should be filename, parts[1] should be segment or count
pname='.'.join(parts[:-2])
path=self.directory + "/" + pname
if not os.path.isfile(path):
reply.add_answer(RR(name, QTYPE.TXT, ttl=self.ttl,
rdata=TXT("File not found")))
return reply
# work out the count mathematically
# First work out the base64 size
l=os.path.getsize(path)
l=(4*l)/3
# And padding
l+=(l%4)
# Finally divide into number of 254 byte chunks
chunks=(l/254)
if ''.join(parts[-2:-1]) == "count":
reply.add_answer(RR(name, QTYPE.TXT, ttl=self.ttl,
rdata=TXT(str(chunks))))
return reply
if ''.join(parts[-2:-1]).isdigit():
# Woo it's a number
# lets base64 the file
chunk=int(''.join(parts[-2:-1]))
if chunk > chunks or chunk < 0:
reply.add_answer(RR(name, QTYPE.TXT, ttl=self.ttl,
rdata=TXT("Chunk out of range")))
return reply
# It's actually trying to read the file, so let's cache it in memory
cooked=self.getcache(path)
# Now lets just grab the chunk
start=chunk*254
txtr=cooked[start:start+254]
reply.add_answer(RR(name, QTYPE.TXT, ttl=self.ttl,
rdata=TXT(txtr)))
return reply
# Replace labels with request label
return reply
if __name__ == '__main__':
import argparse,sys,time
p = argparse.ArgumentParser(description="Fixed DNS Resolver")
p.add_argument("--directory","-r",
metavar="<directory>",
help="Directory to pull files from")
p.add_argument("--domain","-d",
metavar="<domain>",
help="Domain we're working in")
p.add_argument("--port","-p",type=int,default=53,
metavar="<port>",
help="Server port (default:53)")
p.add_argument("--address","-a",default="",
metavar="<address>",
help="Listen address (default:all)")
p.add_argument("--udplen","-u",type=int,default=0,
metavar="<udplen>",
help="Max UDP packet length (default:0)")
p.add_argument("--tcp",action='store_true',default=False,
help="TCP server (default: UDP only)")
p.add_argument("--log",default="request,reply,truncated,error",
help="Log hooks to enable (default: +request,+reply,+truncated,+error,-recv,-send,-data)")
p.add_argument("--log-prefix",action='store_true',default=False,
help="Log prefix (timestamp/handler/resolver) (default: False)")
args = p.parse_args()
resolver = FileResolver(args.directory,args.domain)
logger = DNSLogger(args.log,args.log_prefix)
print("Starting File Resolver (%s:%d) [%s]" % (
args.address or "*",
args.port,
"UDP/TCP" if args.tcp else "UDP"))
if args.udplen:
DNSHandler.udplen = args.udplen
udp_server = DNSServer(resolver,
port=args.port,
address=args.address,
logger=logger)
udp_server.start_thread()
if args.tcp:
tcp_server = DNSServer(resolver,
port=args.port,
address=args.address,
tcp=True,
logger=logger)
tcp_server.start_thread()
while udp_server.isAlive():
time.sleep(1)