// Elektroenergetski softverski inzenjering
// Primenjene racunarske mreze u namenskim sistemima 2
// Vezba 6 - Interpretacija sadrzaja paketa (2.deo)

// We do not want the warnings about the old deprecated and unsecure CRT functions since these examples can be compiled under *nix as well
#ifdef _MSC_VER
    #define _CRT_SECURE_NO_WARNINGS
#endif

// Include libraries
#include <stdlib.h>
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
#include <ws2tcpip.h>
#include "conio.h"
#include "pcap.h"
#include "protocol_headers.h"

// Function declarations
void packet_handler(unsigned char *param, const struct pcap_pkthdr *packet_header, const unsigned char *packet_data);
int cmpEth(unsigned char* eth, char* addr);
char hex(int d) { return d >= 0 && d <= 9 ? d + '0' : d + 'A' - 10; }

int myUDP = 0;

int main()
{
    printf("TLS koristi TCP transportni protokol, a port je 443\n\n");
    pcap_if_t* devices; // List of network interfaces
    pcap_if_t* device; // Network interface
    int i = 0; // Interface counter
    char errorMsg[PCAP_ERRBUF_SIZE + 1]; // Buffer for errors
    // Retrieve the device list of network intefaces
    if (pcap_findalldevs(&devices, errorMsg) == -1)
    {
        printf("Error in pcap_findalldevs: %s\n", errorMsg);
        return 1;
    }
    // Print the list of network interfaces
    for (device = devices; device; device = device->next)
    {
        printf("%d. %s", ++i, device->name);
        if (device->description)
            printf(" (%s)\n", device->description);
        else
            printf(" (No description available)\n");
    }
    if (i == 0)
    {
        printf("\nNo interfaces found! Make sure WinPcap is installed.\n");
        return -1;
    }

    int devNum;
    scanf("%d", &devNum);
    if (devNum < 1 || devNum > i)
    {
        printf("Out of bounds!\n");
        return 1;
    }

    device = devices;

    for (int i = 0; i < devNum-1; i++)
        device = device->next;
    printf("Odabrana kartica: %s\n\n", device->name);

    pcap_t* device_handle;
    // Open the adapter
    if ((device_handle = pcap_open_live(device->name, // name of the device
        65536, // portion of the packet to capture.
        1, // promiscuous mode
        2500, // read timeout
        errorMsg // error buffer
    )) == NULL)
    {
        printf("\n Unable to open the adapter %s.\n", errorMsg);
        // Free the device list
        pcap_freealldevs(devices);
        return -1;
    }

    if (pcap_datalink(device_handle) != DLT_EN10MB) // DLT_EN10MB oznacava Ethernet
    {
        printf("\nThis program works only on Ethernet networks.\n");
        // Free the device list
        pcap_freealldevs(devices);
        return -1;
    }


    unsigned int netmask;
    char filter_exp[] = "udp or tcp";
    struct bpf_program fcode;
    if (device->addresses != NULL)
        // Retrieve the mask of the first address of the interface
        netmask = ((struct sockaddr_in *)(device->addresses->netmask))
        ->sin_addr.s_addr;
    else
        // If the interface is without an address
        // we suppose to be in a C class network
        netmask = 0xffffff;
    // Compile the filter
    if (pcap_compile(device_handle, &fcode, filter_exp, 1, netmask) < 0)
    {
        printf("\n Unable to compile the packet filter. Check the syntax.\n");
        return -1;
    }
    // Set the filter
    if (pcap_setfilter(device_handle, &fcode) < 0)
    {
        printf("\n Error setting the filter.\n");
        return -1;
    }

    pcap_freealldevs(devices);
    printf("Paketi:\n\n");

    pcap_loop(device_handle, 25, packet_handler, NULL);

    printf("\nBroj UDP paketa sa C8-5B-76-DF-49-27 je %d\n", myUDP);
}

void packet_handler(unsigned char *param, const struct pcap_pkthdr *packet_header, const unsigned char *packet_data)
{
    ethernet_header* eh = (ethernet_header*)packet_data;
    printf("Fizicka adresa primaoca: %.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n", eh->dest_address[0],
        eh->dest_address[1], eh->dest_address[2], eh->dest_address[3], eh->dest_address[4], eh->dest_address[5]);

    printf("Fizicka adresa src: %.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n", eh->src_address[0],
        eh->src_address[1], eh->src_address[2], eh->src_address[3], eh->src_address[4], eh->src_address[5]);

    if (ntohs(eh->type) == 0x800) // IPv4
    {
        ip_header* ih = (ip_header*)(packet_data + sizeof(ethernet_header));
        printf(" Logicka adresa primaoca: %u.%u.%u.%u\n", ih->dst_addr[0], ih->dst_addr[1], ih->dst_addr[2], ih->dst_addr[3]);

        if (ih->next_protocol == 17) // UDP
        {
            printf(" UDP\n");
            udp_header* uh = (udp_header*)((unsigned char*)ih + ih->header_length * 4);
            printf("  Port posiljaoca: %hu\n  Port primaoca: %hu \n", ntohs(uh->src_port), ntohs(uh->dest_port));

            if (cmpEth(eh->src_address, "C8-5B-76-DF-49-27"))
                myUDP++;
        }
        else if (ih->next_protocol == 6) // TCP
        {
            printf(" TCP\n");
            tcp_header* th = (tcp_header*)((unsigned char*)ih + ih->header_length * 4);
            printf("  Velicina prijemnog prozora: %hu\n", ntohs(th->windows_size));
            printf("  Redni broj sekvence: %u\n", ntohl(th->sequence_num));

            if (ntohs(th->src_port) == 443) // SSL
            {
                printf("  SSL");
                unsigned char* app_data = (unsigned char*)th + th->header_length * 4;
                int app_length = packet_header->len - (sizeof(ethernet_header) + ih->header_length * 4 + th->header_length * 4);;
                printf(" %d", app_length);
                for (int i = 0; i < app_length; i++)
                {
                    if ((i ) % 16 == 0)
                        printf("\n   ");
                    printf("%.2x ", app_data[i]);
                }
                printf("\nVerzija SSL protokola 0x%.2x%.2x", app_data[1], app_data[2]);
            }
        }
    }

    printf("\n");
}


int cmpEth(unsigned char* eth, char* addr)
{
    int d = strlen(addr);
    for (int i = 0, j = 0; i < 6; i++, j+=3)
    {
        int high = (eth[i] & 0xF0) >> 4;
        int low = eth[i] & 0x0F;
        if (hex(high) != addr[j] || hex(low) != addr[j + 1])
            return 0;
    }
    return 1;
}