/* crypt.h -- base code for traditional PKWARE encryption
   Version 1.2.0, September 16th, 2017

   Copyright (C) 2012-2017 Nathan Moinvaziri
     https://github.com/nmoinvaz/minizip
   Copyright (C) 1998-2005 Gilles Vollant
     Modifications for Info-ZIP crypting
     http://www.winimage.com/zLibDll/minizip.html
   Copyright (C) 2003 Terry Thorsen

   This code is a modified version of crypting code in Info-ZIP distribution

   Copyright (C) 1990-2000 Info-ZIP.  All rights reserved.

   This program is distributed under the terms of the same license as zlib.
   See the accompanying LICENSE file for the full text of the license.
*/

#ifndef _MINICRYPT_H
#define _MINICRYPT_H

#include <stdint.h>
#include <stdlib.h>
#include <time.h>

#  ifndef ZCR_SEED2
#    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
#  endif

#if ZLIB_VERNUM < 0x1270
typedef unsigned long z_crc_t;
#endif

#define RAND_HEAD_LEN  12

/***************************************************************************/

#define CRC32(c, b) ((*(pcrc_32_tab+(((uint32_t)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))

/***************************************************************************/

#define zdecode(pkeys,pcrc_32_tab,c) \
    (update_keys(pkeys,pcrc_32_tab, c ^= decrypt_byte(pkeys)))

#define zencode(pkeys,pcrc_32_tab,c,t) \
    (t = decrypt_byte(pkeys), update_keys(pkeys,pcrc_32_tab,c), t^(c))

/***************************************************************************/

/* Return the next byte in the pseudo-random sequence */
static uint8_t decrypt_byte(uint32_t *pkeys)
{
    unsigned temp;  /* POTENTIAL BUG:  temp*(temp^1) may overflow in an
                    * unpredictable manner on 16-bit systems; not a problem
                    * with any known compiler so far, though */

    temp = ((uint32_t)(*(pkeys + 2)) & 0xffff) | 2;
    return (uint8_t)(((temp * (temp ^ 1)) >> 8) & 0xff);
}

/* Update the encryption keys with the next byte of plain text */
static uint8_t update_keys(uint32_t *pkeys, const z_crc_t *pcrc_32_tab, int32_t c)
{
    (*(pkeys + 0)) = (uint32_t)CRC32((*(pkeys + 0)), c);
    (*(pkeys + 1)) += (*(pkeys + 0)) & 0xff;
    (*(pkeys + 1)) = (*(pkeys + 1)) * 134775813L + 1;
    {
        int32_t keyshift = (int32_t)((*(pkeys + 1)) >> 24);
        (*(pkeys + 2)) = (uint32_t)CRC32((*(pkeys + 2)), keyshift);
    }
    return c;
}

/* Initialize the encryption keys and the random header according to the given password. */
static void init_keys(const char *passwd, uint32_t *pkeys, const z_crc_t *pcrc_32_tab)
{
    *(pkeys + 0) = 305419896L;
    *(pkeys + 1) = 591751049L;
    *(pkeys + 2) = 878082192L;
    while (*passwd != 0)
    {
        update_keys(pkeys, pcrc_32_tab, *passwd);
        passwd += 1;
    }
}

#ifndef NOCRYPT
/* Generate cryptographically secure random numbers */
static int cryptrand(unsigned char *buf, unsigned int len)
{
    /*
    Important  This API is deprecated. New and existing software should 
    start using Cryptography Next Generation APIs. 
    Microsoft may remove this API in future releases.
    see: https://docs.microsoft.com/zh-cn/windows/desktop/api/wincrypt/nf-wincrypt-cryptgenrandom
    */
#define CRYPTGENRANDOM_DEPRECATED 1
#if defined(_WIN32) && !defined(CRYPTGENRANDOM_DEPRECATED)
    HCRYPTPROV provider;
    unsigned __int64 pentium_tsc[1];
    int rlen = 0;
    int result = 0;


    if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
    {
        result = CryptGenRandom(provider, len, buf);
        CryptReleaseContext(provider, 0);
        if (result)
            return len;
    }

    for (rlen = 0; rlen < (int)len; ++rlen)
    {
        if (rlen % 8 == 0)
            QueryPerformanceCounter((LARGE_INTEGER *)pentium_tsc);
        buf[rlen] = ((unsigned char*)pentium_tsc)[rlen % 8];
    }

    return rlen;
#else
    static unsigned calls = 0;              /* ensure different random header each time */
    /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
* output of rand() to get less predictability, since rand() is
* often poorly implemented.
*/
    if (++calls == 1)
    {
        srand((unsigned)(time(NULL) ^ ZCR_SEED2));
    }
    for(unsigned int i = 0; i < len; ++i){
        buf[i] = rand() % 256;
    }
    return len;
#endif
}

/* Create encryption header */
static int crypthead(const char *passwd, uint8_t *buf, int buf_size, uint32_t *pkeys,
    const z_crc_t *pcrc_32_tab, uint8_t verify1, uint8_t verify2)
{
    uint8_t n = 0;                      /* index in random header */
    uint8_t header[RAND_HEAD_LEN - 2];    /* random header */
    uint16_t t = 0;                     /* temporary */

    if (buf_size < RAND_HEAD_LEN)
        return 0;

    init_keys(passwd, pkeys, pcrc_32_tab);

    /* First generate RAND_HEAD_LEN-2 random bytes. */
    cryptrand(header, RAND_HEAD_LEN - 2);

    /* Encrypt random header (last two bytes is high word of crc) */
    init_keys(passwd, pkeys, pcrc_32_tab);

    for (n = 0; n < RAND_HEAD_LEN - 2; n++)
        buf[n] = (uint8_t)zencode(pkeys, pcrc_32_tab, header[n], t);

    buf[n++] = (uint8_t)zencode(pkeys, pcrc_32_tab, verify1, t);
    buf[n++] = (uint8_t)zencode(pkeys, pcrc_32_tab, verify2, t);
    return n;
}
#endif

/***************************************************************************/

#endif