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Python DNS server with Redis backend
# A naive dns server with a Redis backend
# Set keys in Redis you want to be authoritative for (set google.com. 127.0.0.1)
# Tip: Use Redis's ttl functions to have temporary names
# Currently only does A records, feel free to fix that
#
# Licensed under the PSF License
# Thanks to: http://code.activestate.com/recipes/491264-mini-fake-dns-server/
# Author: @Kaerast <alice@kaerast.info>
import socket
import redis # https://github.com/andymccurdy/redis-py
class DNSQuery:
def __init__(self, data):
self.data = data
self.domain = None
tipo = (ord(data[2]) >> 3) & 15 # Opcode bits
if tipo == 0: # Standard query
ini = 12
lon = ord(data[ini])
while lon != 0:
self.domain += data[ini + 1:ini + lon + 1] + '.'
ini += lon + 1
lon = ord(data[ini])
def answer(self, ip):
packet = []
if self.domain and ip:
packet += self.data[:2] + '\x81\x80'
packet += self.data[4:6] + self.data[4:6] + '\x00\x00\x00\x00' # Questions and Answers Counts
packet += self.data[12:] # Original Domain Name Question
packet += '\xc0\x0c' # Pointer to domain name
packet += '\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04' # Response type, ttl and resource data length -> 4 bytes
packet += ''.join(map(lambda x: chr(int(x)), ip.split('.'))) # 4bytes of IP
if not ip:
packet += self.data[:2] + '\x81\x80'
packet += self.data[4:6] + '\x00\x00' + '\x00\x00\x00\x00' # Questions and Answers Counts
packet += self.data[12:] # Original Domain Name Question
packet += '\xc0\x0c' # Pointer to domain name
return ''.join(packet)
if __name__ == '__main__':
r = redis.StrictRedis(host='localhost', port=6379, db=0, password='mypassword')
print 'pyDNS:: dom.query. 60 IN A IP'
udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
udps.bind(('',53))
try:
while True:
data, addr = udps.recvfrom(1024)
p = DNSQuery(data)
ip = r.get(p.domain)
udps.sendto(p.answer(ip), addr)
print 'Answer: %s -> %s' % (p.domain, ip)
except KeyboardInterrupt:
print 'Finished.'
udps.close()
@rfyiamcool

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rfyiamcool commented Aug 28, 2013

牛逼~

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