QueryDNS.py

gistfile1.py

###############file QueryDNS.py#################################
#coding: GBK
#Get DNS answer
#详情见RFC 1035
import os, sys
import socket
import struct
import random
from domaintobyte import domaintobyte, bytetodomain
#DHOST = '208.67.222.222' #DNS 服务器的地址
DHOST = '8.8.8.8'   #DNS 服务器的地址
DPORT = 53              #默认端口是53
LHOST = ''
LPORT = 10001           #绑定到的本地端口
TIMEOUT = 3.0           #超时设置为3秒
##数据包整体的格式
##    +---------------------+
##    |        Header       |
##    +---------------------+
##    |       Question      | the question for the name server
##    +---------------------+
##    |        Answer       | RRs answering the question
##    +---------------------+
##    |      Authority      | RRs pointing toward an authority
##    +---------------------+
##    |      Additional     | RRs holding additional information
##    +---------------------+
def QueryDNS(domain):
    TID = random.randint(-32768, 32767)
    Flags = 0x0100
    Questions = 0x0001 
    AnswerRRs = 0x0000
    AuthorityRRs = 0x0000
    AdditionalRRs = 0x0000
    TIDCHARS = struct.pack('!h', TID)
    domainbyte = domaintobyte(domain)
    #TYPE            value and meaning
    #A               1 a host address
    #NS              2 an authoritative name server
    #MD              3 a mail destination (Obsolete - use MX)
    #MF              4 a mail forwarder (Obsolete - use MX)
    #CNAME           5 the canonical name for an alias
    SEARCHTYPE = 0x0001 
    #Class 一般为 1 指 Internet
    SEARCHCLASS = 0x0001
    #构造请求报文
    Bufhead = struct.pack('!hhhhhh', TID, Flags, Questions, AnswerRRs, AuthorityRRs, AdditionalRRs)
    Buftail = struct.pack('!hh', SEARCHTYPE, SEARCHCLASS)
    Buf = Bufhead + domainbyte + Buftail
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.settimeout(TIMEOUT) #设置超时时间
    s.bind((LHOST,LPORT))
    
    s.sendto(Buf,(DHOST, DPORT))
    print 'Send [OK]'
    
    try:
        data, addr = s.recvfrom(1024)
    except socket.timeout:
        s.close()
        print u'响应超时'
        return
        
    s.close()
    print 'From', addr
    print 'Receved', repr(data)

    if data[0:2] == TIDCHARS:
       
        flags = struct.unpack('!h', data[2:4])[0]
        errormsg = flags & 0x000F
        if errormsg != 0:
            
            return
       
        answerRRs = struct.unpack('!h', data[6:8])[0]
        bitflags = 12; 
        
        
        
        while data[bitflags] != '\x00':
            bitflags += 1
        bitflags += 1 
        bitflags += 2 
        bitflags += 2
       
        
        i = 0

        while i < answerRRs:
            
            bitflags += 2
            if data[bitflags:bitflags+2] == '\x00\x05':
                
                
                bitflags += 8
                rdatalength = struct.unpack('!h', data[bitflags:bitflags+2])[0]
                
                bitflags += 2
                #得到rdata中的全部域名
                fullRecord = GetFullName(bitflags, data)
                bitflags += rdatalength
                print 'CNAME:', bytetodomain(fullRecord)
            
            i += 1

def GetFullName(offset, Buf):
    fullRecord = ''
    oneChar = struct.unpack('!B', Buf[offset:offset+1])[0]
    #print oneChar
    if oneChar & 0xc0 == 0xc0 : #指针
        jump = struct.unpack('!h', Buf[offset:offset+2])[0]
        jump = jump & 0x3FFF    #指针指向的地址
        fullRecord += GetFullName(jump, Buf)
    elif oneChar == 0 :         #域名以\0结束
        return '\x00'
    else :                      #域名部分
        fullRecord += Buf[offset:offset+oneChar+1]
        fullRecord += GetFullName(offset+oneChar+1, Buf)
        
    return fullRecord
        
           
if __name__ == "__main__":
    print 'main start...'
    if len(sys.argv) < 2:
        print "Usage:QueryDNS.py www.google.cn"
    elif len(sys.argv) == 2:
        DHOST = '8.8.8.8'   #DNS 服务器的地址
    else:
        DHOST = sys.argv[2]
    try:
        domain = sys.argv[1]
        QueryDNS(domain)
    except Exception, e:
        logging.error("exit:error:%s" %e)
    print 'main over'