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# -*- coding: utf-8 -*-
from __future__ import print_function
try:
from subprocess import getoutput
except ImportError:
from commands import getoutput
from dnslib import RR,QTYPE,RCODE,TXT,parse_time
from dnslib.label import DNSLabel
from dnslib.server import DNSServer,DNSHandler,BaseResolver,DNSLogger
class ShellResolver(BaseResolver):
"""
Example dynamic resolver.
Maps DNS labels to shell commands and returns result as TXT record
(Note: No context is passed to the shell command)
Shell commands are passed in a a list in <label>:<cmd> format - eg:
[ 'uptime.abc.com.:uptime', 'ls:ls' ]
Would respond to requests to 'uptime.abc.com.' with the output
of the 'uptime' command.
For non-absolute labels the 'origin' parameter is prepended
"""
def __init__(self,routes,origin,ttl):
self.origin = DNSLabel(origin)
self.ttl = parse_time(ttl)
self.routes = {}
for r in routes:
route,_,cmd = r.partition(":")
if route.endswith('.'):
route = DNSLabel(route)
else:
route = self.origin.add(route)
self.routes[route] = cmd
def resolve(self,request,handler):
reply = request.reply()
qname = request.q.qname
cmd = self.routes.get(qname)
if cmd:
output = getoutput(cmd).encode()
reply.add_answer(RR(qname,QTYPE.TXT,ttl=self.ttl,
rdata=TXT(output[:254])))
else:
reply.header.rcode = RCODE.NXDOMAIN
return reply
if __name__ == '__main__':
import argparse,sys,time
p = argparse.ArgumentParser(description="Shell DNS Resolver")
p.add_argument("--map","-m",action="append",required=True,
metavar="<label>:<shell command>",
help="Map label to shell command (multiple supported)")
p.add_argument("--origin","-o",default=".",
metavar="<origin>",
help="Origin domain label (default: .)")
p.add_argument("--ttl","-t",default="60s",
metavar="<ttl>",
help="Response TTL (default: 60s)")
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 = ShellResolver(args.map,args.origin,args.ttl)
logger = DNSLogger(args.log,args.log_prefix)
print("Starting Shell Resolver (%s:%d) [%s]" % (
args.address or "*",
args.port,
"UDP/TCP" if args.tcp else "UDP"))
for route,cmd in resolver.routes.items():
print(" | ",route,"-->",cmd)
print()
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)
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