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Archive for February, 2004

Simple Secure Data Transfer

Published by Paolo Ardoino on February 13, 2004 under Crypto/Security

SSDT, Simple Secure Data Transfer, utility makes use of sending spoofed ICMP and UDP traffic to send RSA encrypted files. It is based on OpenSSL library.

Version: 0.1

Download source code

As usual here is a bit of code :)

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// RSA encryption function
long int rsa_encrypt(char *pubfile, unsigned long int plsz, char *filein, unsigned char *ciphdata)
{
  int ks=0;
  unsigned long size=0, len=0, ctr=0, ciphsz=0;
  RSA* key=NULL;
  FILE *fp=NULL;
  char *tmpciph=NULL, *tmpplain=NULL;
 
  if(!(fp = fopen(filein, "r"))) {
    fprintf(stderr, "Error: Cannot locate input file.\n");
    return -1;
  }
  key = (RSA *)readpubkey(pubfile);
  if (!key) {
    return -1;
  }
  ks = RSA_size(key);
  tmpplain = (unsigned char *)malloc(ks * sizeof(unsigned char));
  tmpciph = (unsigned char *)malloc(ks * sizeof(unsigned char));
  srand(time(NULL));
  while(!feof(fp)) {
    if (ciphsz + ks > plsz) {
      fprintf(stderr, "Error: Size of RSA encrypted data exceeded: %ld bytes.\n", ciphsz);
      fclose(fp);
      return -1;
    }
    memset(tmpplain, '\0', ks);
    memset(tmpciph, '\0', ks);
    len = fread(tmpplain, 1, ks - 11, fp);
    if((size = RSA_public_encrypt(len, tmpplain, tmpciph, key, RSA_PKCS1_PADDING)) == -1) {
      fprintf(stderr, "%s\n", ERR_error_string(ERR_get_error(), NULL));
      return -1;
    }
    for (ctr = 0; ctr < size; ciphsz++, ctr++)
      *(ciphdata + ciphsz) = *(tmpciph + ctr);
  }
  fclose(fp);
  free(tmpciph);
  free(tmpplain);
  RSA_free(key);
  return ciphsz;
}
 
// RSA decryption function
long int rsa_decrypt(char *secfile, unsigned char *ciphdata, unsigned long int ciphsz,unsigned char *plaindata)
{
  unsigned long int plsz=0, size=0, ks=0, ctr=0;
  RSA* key=NULL;
  char *tmpplain=NULL, *tmpciph=NULL;
 
  key = (RSA *)readseckey(secfile);
  ks = RSA_size(key);
  tmpciph = (unsigned char *)malloc(ks * sizeof(unsigned char));
  tmpplain = (unsigned char *)malloc(ks * sizeof(unsigned char));
  while (*ciphdata != '\0' && plsz < ciphsz) {
    memset(tmpciph, '\0', ks);
    memset(tmpplain, '\0', ks);
    bcopy(ciphdata, tmpciph, ks);
    for (ctr=0; ctr < ks; ctr++)
      ciphdata++;
    if((size = RSA_private_decrypt(ks, tmpciph, tmpplain, key, RSA_PKCS1_PADDING)) == -1) {
    //  fprintf(stderr, "%s\n", ERR_error_string(ERR_get_error(), NULL));
    //  exit(EXIT_FAILURE);
      continue;
    }
    for(ctr = 0; ctr < size; plsz++, ctr++)
      *(plaindata + plsz) = *(tmpplain + ctr);
  }
  free(tmpplain);
  free(tmpciph);
  RSA_free(key);
  return plsz;
}