105 lines
3.5 KiB
C
105 lines
3.5 KiB
C
|
|
#define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
|
|
|
|
/***********************************************************************
|
|
* Return the next byte in the pseudo-random sequence
|
|
*/
|
|
static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab)
|
|
{
|
|
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 = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
|
|
return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Update the encryption keys with the next byte of plain text
|
|
*/
|
|
static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c)
|
|
{
|
|
(*(pkeys+0)) = CRC32((*(pkeys+0)), c);
|
|
(*(pkeys+1)) += (*(pkeys+0)) & 0xff;
|
|
(*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
|
|
{
|
|
register int keyshift = (int)((*(pkeys+1)) >> 24);
|
|
(*(pkeys+2)) = 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,unsigned long* pkeys,const unsigned long* pcrc_32_tab)
|
|
{
|
|
*(pkeys+0) = 305419896L;
|
|
*(pkeys+1) = 591751049L;
|
|
*(pkeys+2) = 878082192L;
|
|
while (*passwd != '\0') {
|
|
update_keys(pkeys,pcrc_32_tab,(int)*passwd);
|
|
passwd++;
|
|
}
|
|
}
|
|
|
|
#define zdecode(pkeys,pcrc_32_tab,c) \
|
|
(update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
|
|
|
|
#define zencode(pkeys,pcrc_32_tab,c,t) \
|
|
(t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
|
|
|
|
#ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
|
|
|
|
#define RAND_HEAD_LEN 12
|
|
/* "last resort" source for second part of crypt seed pattern */
|
|
# ifndef ZCR_SEED2
|
|
# define ZCR_SEED2 3141592654UL /* use PI as default pattern */
|
|
# endif
|
|
|
|
static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting)
|
|
const char *passwd; /* password string */
|
|
unsigned char *buf; /* where to write header */
|
|
int bufSize;
|
|
unsigned long* pkeys;
|
|
const unsigned long* pcrc_32_tab;
|
|
unsigned long crcForCrypting;
|
|
{
|
|
int n; /* index in random header */
|
|
int t; /* temporary */
|
|
int c; /* random byte */
|
|
unsigned char header[RAND_HEAD_LEN-2]; /* random header */
|
|
static unsigned calls = 0; /* ensure different random header each time */
|
|
|
|
if (bufSize<RAND_HEAD_LEN)
|
|
return 0;
|
|
|
|
/* 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));
|
|
}
|
|
init_keys(passwd, pkeys, pcrc_32_tab);
|
|
for (n = 0; n < RAND_HEAD_LEN-2; n++)
|
|
{
|
|
c = (rand() >> 7) & 0xff;
|
|
header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
|
|
}
|
|
/* 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] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
|
|
}
|
|
buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
|
|
buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
|
|
return n;
|
|
}
|
|
|
|
#endif
|