/* $Id: pswd.c,v 1.1 2004/12/07 15:12:38 cinar Exp $
 *
 * pswd.c: is a simple program which emulates the password
 * encryption/encoding process done by LabView HTTP Server
 * (part of G Server)'s sub-vi named "Pswd Encode Password.vi"
 *
 * Copyright (c) 2003 Ali Onur Cinar <cinar(a)zdo.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version. And also
 * please DO NOT REMOVE my name, and give me a CREDIT when you use
 * whole or a part of this program in an other program.
 *
 * To compile:
 *   using GNU C Compiler     : gcc pswd.c -lieee
 *   using Intel C++ Compiler : icc -mp pswd.c -lieee
 *
 * Tested on Linux using GNU C Compiler 3.2, Intel C++ Compiler 7.1
 *
 */

#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <memory.h>
#include <string.h>
#include <endian.h>

static inline unsigned char rotate (const unsigned char c) {
  return (c << 1) | ((c & 0x80) >> 7);
}

static void copy (unsigned char* s, unsigned char* t, int c) {
  int i;
  for (i=0; i<=c; i++)
    t[i] = s[i];
}

static void reverse (unsigned char* s, int c) {
  int i;
  unsigned char *t;
  assert((t = (unsigned char*) malloc(c+1)) != NULL);

  copy (s,t,c);

  for (i=c; i>=0; i--)
    s[i] = t[c-i];

  free(t);
}

typedef struct __pswd_pack {
  char *user;
  char *pass;
  unsigned char enc[19];
} pswd_pack;

void pswd_encode (pswd_pack *p) {
  /* vars */
  char *pwd;
  unsigned char *key, *key1, *key2, *key3, *key4;
  int i,j;

  /* for casting */
  union dbits {
    double d;
    unsigned char s[8];
  } ac;

  /* force IEEE 754 compatibility */
  assert(_LIB_VERSION == _IEEE_);

  /* check user and pass sizes */
  assert(strlen(p->user) >= 2);
  assert(strlen(p->pass) <= 126);

  /* combine pass and user (pass + first 2 letter of user ) */
  assert((pwd = (char*) malloc(strlen(p->pass)+2)) != NULL);
  memset(pwd,0,strlen(p->pass)+2);
  strcpy(pwd,p->pass);
  strncat(pwd,p->user,2);

  /* fill key block */
  assert((key = (unsigned char*) malloc(128)) != NULL);
  for (i=0; i<128; i++)
    key[i] = pwd[i % strlen(pwd)];

  free(pwd);

  /* accumulate */
  for (i=0,ac.d=0.0; i<128; i++)
    ac.d = (ac.d * M_PI_2) + key[i];

  free(key);

  /* cast double to unsigned char array */
  key1 = ac.s;

#if __BYTE_ORDER == __LITTLE_ENDIAN
  /* to big endian */
  reverse(key1,7);
#endif

  /* rotate */
  assert((key2 = (unsigned char*) malloc(8)) != NULL);
  for (i=0; i<8; i++)
    key2[i] = rotate(key1[i]);

  /* reverse */
  assert((key3 = (unsigned char*) malloc(8)) != NULL);
  copy(key1,key3,7);
  reverse(key3,7);

  /* xor */
  assert((key4 = (unsigned char*) malloc(8)) != NULL);
  for (i=0; i<8; i++)
    key4[i] = (key1[i] ^ key2[i]) ^ key3[i];

  free(key2);
  free(key3);

  /* combine user and enc */
  strncpy((char*) p->enc,p->user,2);

  /* enc */
  for (i=0,j=2; i<8; i++,j+=2) {
    p->enc[j] = ('a'+i) + (key4[i] & 7);
    p->enc[j+1] = ('a'+i) + ((key4[i] >> 4));
  }

  free(key4);

  /* terminate enc */
  p->enc[18] = '\0';
}

int main (int argc, char **argv) {

  pswd_pack p;

  /* test 1 */
  p.user = "cinar";
  p.pass = "onur";
  pswd_encode(&p);
  printf("Checking (%s)... %s\n",p.enc,
    (strcmp("cibgbjheknemjtnvnr",(char*) p.enc) == 0) ? "ok" : "failed");

  return(0);
}