DES Decryption not working!!!

[wolk324]

Hi guys i have this code for multicast with encryption and decryption with DES(shared key) i think encryption goes ok but decryption not working and i can't find the problem both codes compiles fine without problem when i execute them encryption works but decryption not PLS HELP ME!!!... here is code. Receiver.c:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <openssl/des.h>
#define MAX_LEN  1024
char *Decrypt( char *Key, char *Msg, int size)
{
   static char*     Res;
   int              n=0;
   DES_cblock       Key2;
   DES_key_schedule schedule;
   Res = ( char * ) malloc( size );
   memcpy( Key2, Key,8);
   DES_set_odd_parity( &Key2 );
   DES_set_key_checked( &Key2, &schedule );
   DES_cfb64_encrypt( ( unsigned char * ) Msg, ( unsigned char * ) Res, size, &schedule, &Key2, &n, DES_DECRYPT );
return (Res);
}
int main(int argc, char *argv[])
{
    int     sock;
    int         flag_on = 1;
    struct      sockaddr_in multicast_addr;
    char        message_received[MAX_LEN+1];
    int             msgrecv_len;
    struct          ip_mreq mc_req;
    char*           multicast_ip;
    unsigned short  multicast_port;
    struct          sockaddr_in from_addr;
    unsigned int    from_len;
    char        *decrypted;
  FILE *fp;
  char key[512];
  fp=fopen("passphrase.txt", "r");
  if (fp) {
  while(fscanf(fp, "%s", key)!=EOF)
  fclose(fp);
}
printf("Key: %s\n", key);
if (argc != 3)
{
    fprintf(stderr, "Usage: %s Multicast_IP Multicast_Port\n", argv[0]);
    exit(1);
}
    multicast_ip = argv[1];          /* arg 1: multicast ip address */
    multicast_port = atoi(argv[2]);  /* arg 2: multicast port number */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
{
    perror("socket() failed");
    exit(1);
}
if ((setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &flag_on,
sizeof(flag_on))) < 0)
{
    perror("setsockopt() failed");
    exit(1);
}
memset(&multicast_addr, 0, sizeof(multicast_addr));
multicast_addr.sin_family      = AF_INET;
multicast_addr.sin_addr.s_addr = htonl(INADDR_ANY);
multicast_addr.sin_port        = htons(multicast_port);
if ((bind(sock, (struct sockaddr *) &multicast_addr, sizeof(multicast_addr))) < 0)
{
    perror("bind() failed");
    exit(1);
}
mc_req.imr_multiaddr.s_addr = inet_addr(multicast_ip);
mc_req.imr_interface.s_addr = htonl(INADDR_ANY);
if ((setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*) &mc_req, sizeof(mc_req))) < 0)
{
    perror("setsockopt() failed");
    exit(1);
}
    while(1)
{
    decrypted=malloc(sizeof(message_received));
    memcpy(decrypted,Decrypt(key,message_received,sizeof(message_received)), sizeof(message_received));
    memset(message_received, 0, sizeof(message_received));
    from_len = sizeof(from_addr);
    memset(&from_addr, 0, from_len);
if ((msgrecv_len = recvfrom(sock, message_received, MAX_LEN, 0, (struct sockaddr*)&from_addr, &from_len)) < 0)
{
    perror("recvfrom() failed");
    break;
}
printf("Received %d bytes from %s: ", msgrecv_len, inet_ntoa(from_addr.sin_addr));
printf("%s", decrypted);
}
if ((setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (void*) &mc_req, sizeof(mc_req))) < 0)
{
    perror("setsockopt() failed");
    exit(1);  
}
close(sock);
return 0;
}

and this is the result i'm getting:

bunny@ubuntu:~/Desktop/Client Receiver$ ./rec 224.0.1.14 6000

Key: qwerty123ABCD456

Received 3 bytes from 192.168.1.8: ��O�p1�z�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�z�̚�w�

[TheIdeasMan]

Hi,

Seriously - have you tried using a debugger? It will save you days of staring at code that compiles and is the most efficient at finding logic errors. You should be able top quickly isolate where the problem is then deduce it's cause.

HTH

Edit:

Some stuff I noticed:

when using any type of scanf, always check the value it returns - to see if it worked. I notice you check for EOF, but check the number of items read in as well. I found that a switch is a good way of dealing with all the cases.

With malloc, always check the pointer returned is not NULL, that will show it worked as well.

Did you free any of the memory you allocated? Not important for making your program work right now, but important nonetheless.

I don't have any experience with sockets etc, just pointing out a couple of things I do know a little about.

HTH

[wolk324]

thx i'll check again...