/* 
   does stuff when you attempt to connect to ports in a certain order
   
 */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/if_ether.h>
#include <net/if.h>
#include <unistd.h>
#include <sys/time.h>
#include "/usr/include/sys/ioctl.h"

#define RSTS		10
#define IF		"eth0"


#define MYPORT 4950    /* the port users will be sending to */

#define MAXBUFLEN 100


int sp_fd;

unsigned short ip_fast_csum(unsigned char *iph,unsigned long ihl) {
        unsigned long sum;

        __asm__ __volatile__("
            movl (%1), %0
            subl $4, %2
            jbe 2f
            addl 4(%1), %0
            adcl 8(%1), %0
            adcl 12(%1), %0
1:          adcl 16(%1), %0
            lea 4(%1), %1
            decl %2
            jne 1b
            adcl $0, %0
            movl %0, %2
            shrl $16, %0
            addw %w2, %w0
            adcl $0, %0
            notl %0
2:
 	    "
        : "=r" (sum), "=r" (iph), "=r" (ihl)
        : "1" (iph), "2" (ihl));
        return(sum);
}

struct tcppk {                         
        struct iphdr ip;
        struct tcphdr tcp;
        char data[1500];
};

struct pseudo {
	unsigned long saddr, daddr;
	unsigned char zero, proto;
	unsigned short len;
};

void raw(void)
{
    int opt=1;

    if((sp_fd=socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) <0){
        perror("\nRAWIP() RAW Socket problems [Died]");
        exit();
    }
    if(setsockopt(sp_fd, IPPROTO_IP, IP_HDRINCL, &opt, sizeof(opt)) <0){
            perror("RAWIP() Cannot set IP_HDRINCL [Died]");
            exit();
    }

}

int tap(char* device,int mode)
{
    int fd;
    struct ifreq ifr;

    if((fd=socket(AF_INET, SOCK_PACKET, htons(0x3))) <0){
        perror("SNIFF() SOCK_PACKET allocation problems [Died]");
        exit();
    }

    strcpy(ifr.ifr_name,device);
    if((ioctl(fd, SIOCGIFFLAGS, &ifr)) <0){    
        perror("SNIFF() Can't get device flags [Died]");
        close(fd);
        exit();
    }

    if(!mode)ifr.ifr_flags ^= IFF_PROMISC;
    else ifr.ifr_flags |= IFF_PROMISC;
    if((ioctl(fd, SIOCSIFFLAGS, &ifr)) <0){
        perror("SNIFF() Can't set/unset promiscuous mode [Died]");
        close(fd);
        exit();
    }

    if(!mode){
        close(fd);
        return(0);
    }
    else return(fd);
}

void root_shell()
{


  int sockfd, new_fd;  /* listen on sock_fd, new connection on new_fd */
  struct sockaddr_in my_addr;    /* my address information */
  struct sockaddr_in their_addr; /* connector's address information */
  int sin_size;
  int numbytes;
  struct linger lingerparam;
  int reuseparam;
  
  char outmsg[1024];

  sockfd = socket(AF_INET, SOCK_STREAM, 0); /* do some error checking! */

  my_addr.sin_family = AF_INET;         /* host byte order */
  my_addr.sin_port = htons(MYPORT);     /* short, network byte order */
  my_addr.sin_addr.s_addr = INADDR_ANY; /* auto-fill with my IP */
  bzero(&(my_addr.sin_zero), 8);        /* zero the rest of the struct */

  /* don't forget your error checking for these calls: */

  /* set linger to 1s... */
  lingerparam.l_onoff = 1; 
  lingerparam.l_linger = 1;
  if (setsockopt(sockfd, SOL_SOCKET,SO_LINGER,&lingerparam,sizeof(lingerparam)) != 0)
    {
      fprintf(stderr, "Error setting socket options\n");
      return;
    }
  /* now set SO_REUSEADDR so we can rebind soon */
  reuseparam = 0;
  if (setsockopt(sockfd, SOL_SOCKET,SO_REUSEADDR,&reuseparam,sizeof(reuseparam)) != 0)
    {
      fprintf(stderr, "Error setting socket options\n");
      return;
    }

  fprintf(stderr,"Binding...\n");
  if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) != 0)
    {
      close(sockfd);
      fprintf(stderr, "Bind error\n");
      return;
    }
  fprintf(stderr,"Listen...\n");
  if (listen(sockfd, 0) != 0)
    {
      close(sockfd);
      fprintf(stderr, "Listen error");
      return;
    }
  sin_size = sizeof(struct sockaddr_in);
  fprintf(stderr,"Accept...\n");
  
  new_fd = accept(sockfd, &their_addr, &sin_size);

  fprintf(stderr,"sending thing\n");

  sprintf(outmsg, "Adding firewall allowance rule for %s\n", inet_ntoa(their_addr.sin_addr.s_addr));

  if ((numbytes=send(new_fd, outmsg, strlen(outmsg), 0)) == -1) {
    close(sockfd);
    perror("send");
    exit(1);
  }
  close(new_fd);
  shutdown(sockfd,0);
  close(sockfd);
    
}

unsigned long in_aton(const char *str)
{
        unsigned long l;
        unsigned long val;
        int i;

        l = 0;
        for (i = 0; i < 4; i++)
        {
           l <<= 8;
           if (*str != '\0')
           {
               val = 0;
               while (*str != '\0' && *str != '.')
               {
                        val *= 10;
                        val += *str - '0';
                                str++;
                        }
                        l |= val;
                        if (*str != '\0')
                                str++;
                }
        }
        return(htonl(l));
}

void uff(void) {
	printf("\nUso: RST sourceIP src_port destIP dest_port\n\n");
	exit(1);
}

int main(int argc, char **argv) {

	unsigned char buffer[1500], checkbuff[32], checkbuff2[32];
	struct sockaddr_in sin, sin2;
	struct iphdr *ip;
	struct tcphdr *tcp;
	struct pseudo *psp, *psp2;
	struct tcppk tpk, tpk2;
	int sniff, snt, snt2, rst=0;
	unsigned long saddr, daddr;
	unsigned short src, dest;
        int combo_ctr = 0;
	int combo_list[3] = {7000,8000,9000};
	#define HOST_MAX 10
	long last_host;
	long last_time; 
	int host_count; 
	struct timeval tv;
	struct timezone tz;
	int x;

	/*	if(argc<5) {
		uff();
		exit(1);
	}
	saddr=in_aton(argv[1]);daddr=in_aton(argv[3]);
	src=htons(atoi(argv[2]));dest=htons(atoi(argv[4]));
	*/
	sniff=tap(IF, 1);
	/* raw(); */

	if(setpriority(0, 0, -20) <0){
                fprintf(stderr,"\nRST setpriority Error\n");
        }

        ip = (struct iphdr *)(((char *)buffer)+14);
        tcp = (struct tcphdr *)(((char *)buffer)+(sizeof(struct iphdr)+14));
        psp = (struct pseudo *)checkbuff;
	psp2 = (struct pseudo *)checkbuff2;

	memset(&sin, 0, sizeof(sin));
        sin.sin_family=AF_INET;
        sin.sin_port=src;
        sin.sin_addr.s_addr=saddr;
	memset(&sin2, 0, sizeof(sin2));
	sin.sin_family=AF_INET;
        sin.sin_port=dest;
        sin.sin_addr.s_addr=daddr;

        memset(&tpk, 0, sizeof(tpk));
	memset(&tpk2, 0, sizeof(tpk2));
	memset(psp, 0, sizeof(struct pseudo));
	memset(psp2, 0, sizeof(struct pseudo));	

        tpk.ip.ihl=5;
        tpk.ip.version=4;
        tpk.ip.tos=0;
        tpk.ip.tot_len=htons(40);
        tpk.ip.frag_off=0;
        tpk.ip.ttl=64;
        tpk.ip.protocol=IPPROTO_TCP;
        tpk.ip.saddr=daddr;
        tpk.ip.daddr=saddr;
        tpk.tcp.source=dest;
        tpk.tcp.dest=src;
        tpk.tcp.doff=5;
        tpk.tcp.rst=1;
        tpk.tcp.ack=1;
        tpk.tcp.window=0;
        psp->saddr=tpk.ip.daddr;
        psp->daddr=tpk.ip.saddr;
        psp->zero=0;
        psp->proto=IPPROTO_TCP;
        psp->len=htons(20);
	tpk2=tpk;
	tpk2.ip.saddr=saddr;
	tpk2.ip.daddr=daddr;
	tpk2.tcp.source=src;
	tpk2.tcp.dest=dest;
	psp2->saddr=tpk.ip.saddr;
        psp2->daddr=tpk.ip.daddr;
        psp2->zero=0;
        psp2->proto=IPPROTO_TCP;
        psp2->len=htons(20);

	/*        printf("RSTing :\t%s:%d > %s:%d\n",
		  argv[1], src, argv[3], dest); */
        while(read(sniff, &buffer, sizeof(buffer))) {
	  /*	  printf("src addr %d src port: %d\n", ip->saddr,ntohs(tcp->source)); */
	  /*	  	  printf("%li",tv.tv_usec);  */
	  gettimeofday(&tv, &tz);
	  if ((tv.tv_usec > last_time + 1000000) && (combo_ctr > 0)) { combo_ctr = 0; last_time = tv.tv_usec; fprintf(stderr,"resetting(time)\n");}
	  if (((combo_ctr > 0)  && (last_host == ip->saddr)) || (combo_ctr == 0))
	  {
	    last_host = ip->saddr;
	    last_time = tv.tv_usec;
	    if (combo_list[combo_ctr] == ntohs(tcp->source))
	    {
	      combo_ctr++;
	      printf("Incrementing ctr %i\n",combo_ctr);
	      if(combo_ctr == 3)
		{
		  fprintf(stderr,"GOT TRIPLET\n");
		  root_shell();
		  combo_ctr = 0;
		}
	    }
	    else
	      {
		if ((combo_ctr > 0) && ( last_host != ip->saddr))
		  {
		    printf("resetting\n");
		    combo_ctr = 0;
		  }
	      }
	  }
	}
	printf("\n");
	tap(IF, 0);
	exit(0);
}