void sign_file(char file_name[], RSA* rsa)
{
  FILE *f, *fsig;

  f = fopen(file_name, "r+"); //file I want to sign
  fsig = fopen("file.sig", "w+"); //hash value of 'file_name'
  calc_sha256(file_name, "file.sig"); //hash value now inside of file.sig, lets now sign that hash
  fclose(fsig);

  int fsize=0;

  fsig = fopen("file.sig", "r+"); //read the hash inside that file

  fseek(fsig, 0L, SEEK_END);
  fsize = ftell(fsig);
  fseek(fsig, 0L, SEEK_SET);

  unsigned char *m = malloc(fsize);
  unsigned char *sigret = malloc(1024); //i guess its 1024 because my ksize if 1024...
  unsigned int *sigret_len = 0;
  sigret_len = sizeof(sigret);
  printf("teste:%d\n", sigret_len);
  BIO *b=NULL;
  RSA *rsaPrivateKey=NULL;


  fread(m, fsize, 1, fsig); //printed *m and it was loaded correctly

//  RSA_sign(NID_sha256, m, strlen(m), sigret, strlen(sigret), rsa);

}