python dig 模拟—— DGA域名判定用

#!/usr/bin/env python

import dns.resolver, sys

def get_domain_ip(domain):
    """Get the DNS record, if any, for the given domain."""
    dns_records = list()
    try:
        # get the dns resolutions for this domain
        dns_results = dns.resolver.query(domain)
        dns_records = [ip.address for ip in dns_results]
    except dns.resolver.NXDOMAIN as e:
        print "the domain does not exist so dns resolutions remain empty. domain:", domain
    except dns.resolver.NoAnswer as e:
        print "the resolver is not answering so dns resolutions remain empty, domain:", domain
    return dns_records

hostname = sys.argv[1]
print "Recursive name lookup (simulates dig)..."

n=hostname
try:
  while True:
    for rdata in dns.resolver.query(n, 'CNAME') :
      print n, "cname is", rdata
      n=rdata.target
except:
  print get_domain_ip(n)

例如：

python dig_ip.py 8264.com
Recursive name lookup (simulates dig)...
8264.com cname is qaz2d84guo7uz5q2.gfnormal01at.com.
[u'121.29.18.91'] =>IP地址

python dig_ip.py www.baidu.com
Recursive name lookup (simulates dig)...
www.baidu.com cname is www.a.shifen.com.
www.a.shifen.com. cname is www.wshifen.com.
[u'103.235.46.39', u'103.235.46.40'] =>IP地址

来一个无查询结果的 DGA域名：

python dig_ip.py s09xo3-l5domek9ck5ct3go4m.com
Recursive name lookup (simulates dig)...
the domain does not exist so dns resolutions remain empty. domain: s09xo3-l5domek9ck5ct3go4m.com
[]

其中，dns.resolver.NoAnswer会在查询类别错误时候跑出此异常，例如：

python dig_ip.py www.baidu.com
Recursive name lookup (simulates dig)...
www.baidu.com cname is www.a.shifen.com.
www.a.shifen.com. cname is www.wshifen.com.
The DNS response does not contain an answer to the question: www.wshifen.com. IN CNAME

最后重构下代码：

#!/usr/bin/env python

import dns.resolver, sys

def get_domain_ip(domain):
    """Get the DNS record, if any, for the given domain."""
    dns_records = list()
    try:
        # get the dns resolutions for this domain
        dns_results = dns.resolver.query(domain)
        dns_records = [ip.address for ip in dns_results]
    except dns.resolver.NXDOMAIN as e:
        print "the domain does not exist so dns resolutions remain empty. domain:", domain
    except dns.resolver.NoAnswer as e:
        print "the resolver is not answering so dns resolutions remain empty, domain:", domain
    return dns_records

def dig_ip(n):
    try:
        while True:
            for rdata in dns.resolver.query(n, 'CNAME') :
                print n, "cname is", rdata
                n=rdata.target
    except Exception as e:
        print e
        return get_domain_ip(n)

if __name__ == "__main__":
    print "Recursive name lookup (simulates dig)..."
    print dig_ip(sys.argv[1])