/* crypt.h -- base code for crypt/uncrypt ZIPfile | |
Version 1.01e, February 12th, 2005 | |
Copyright (C) 1998-2005 Gilles Vollant | |
This code is a modified version of crypting code in Infozip distribution | |
The encryption/decryption parts of this source code (as opposed to the | |
non-echoing password parts) were originally written in Europe. The | |
whole source package can be freely distributed, including from the USA. | |
(Prior to January 2000, re-export from the US was a violation of US law.) | |
This encryption code is a direct transcription of the algorithm from | |
Roger Schlafly, described by Phil Katz in the file appnote.txt. This | |
file (appnote.txt) is distributed with the PKZIP program (even in the | |
version without encryption capabilities). | |
If you don't need crypting in your application, just define symbols | |
NOCRYPT and NOUNCRYPT. | |
This code support the "Traditional PKWARE Encryption". | |
The new AES encryption added on Zip format by Winzip (see the page | |
http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong | |
Encryption is not supported. | |
*/ | |
#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 |