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4430 cbradney 1
/*
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For general Scribus (>=1.3.2) copyright and licensing information please refer
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to the COPYING file provided with the program. Following this notice may exist
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a copyright and/or license notice that predates the release of Scribus 1.3.2
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for which a new license (GPL+exception) is in place.
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*/
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/* crypt.h -- base code for crypt/uncrypt ZIPfile
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   Version 1.01, May 8th, 2004
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   Copyright (C) 1998-2004 Gilles Vollant
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   This code is a modified version of crypting code in Infozip distribution
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   The encryption/decryption parts of this source code (as opposed to the
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   non-echoing password parts) were originally written in Europe.  The
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   whole source package can be freely distributed, including from the USA.
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   (Prior to January 2000, re-export from the US was a violation of US law.)
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   This encryption code is a direct transcription of the algorithm from
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   Roger Schlafly, described by Phil Katz in the file appnote.txt.  This
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   file (appnote.txt) is distributed with the PKZIP program (even in the
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   version without encryption capabilities).
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   If you don't need crypting in your application, just define symbols
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   NOCRYPT and NOUNCRYPT.
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   This code support the "Traditional PKWARE Encryption".
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   The new AES encryption added on Zip format by Winzip (see the page
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   http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
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   Encryption is not supported.
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*/
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#include "scconfig.h"
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#define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
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/***********************************************************************
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 * Return the next byte in the pseudo-random sequence
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 */
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static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab)
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{
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    unsigned temp;  /* POTENTIAL BUG:  temp*(temp^1) may overflow in an
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                     * unpredictable manner on 16-bit systems; not a problem
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                     * with any known compiler so far, though */
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    temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
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    return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
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}
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/***********************************************************************
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 * Update the encryption keys with the next byte of plain text
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 */
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static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c)
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{
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    (*(pkeys+0)) = CRC32((*(pkeys+0)), c);
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    (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
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    (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
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    {
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      register int keyshift = (int)((*(pkeys+1)) >> 24);
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      (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
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    }
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    return c;
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}
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/***********************************************************************
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 * Initialize the encryption keys and the random header according to
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 * the given password.
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 */
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static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab)
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{
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    *(pkeys+0) = 305419896L;
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    *(pkeys+1) = 591751049L;
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    *(pkeys+2) = 878082192L;
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    while (*passwd != '\0') {
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        update_keys(pkeys,pcrc_32_tab,(int)*passwd);
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        passwd++;
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    }
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}
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#define zdecode(pkeys,pcrc_32_tab,c) \
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    (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
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#define zencode(pkeys,pcrc_32_tab,c,t) \
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    (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
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#ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
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#define RAND_HEAD_LEN  12
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   /* "last resort" source for second part of crypt seed pattern */
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#  ifndef ZCR_SEED2
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#    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
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#  endif
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static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting)
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    const char *passwd;         /* password string */
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    unsigned char *buf;         /* where to write header */
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    int bufSize;
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    unsigned long* pkeys;
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    const unsigned long* pcrc_32_tab;
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    unsigned long crcForCrypting;
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{
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    int n;                       /* index in random header */
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    int t;                       /* temporary */
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    int c;                       /* random byte */
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    unsigned char header[RAND_HEAD_LEN-2]; /* random header */
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    static unsigned calls = 0;   /* ensure different random header each time */
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    if (bufSize<RAND_HEAD_LEN)
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      return 0;
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    /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
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     * output of rand() to get less predictability, since rand() is
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     * often poorly implemented.
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     */
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    if (++calls == 1)
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    {
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        srand((unsigned)(time(NULL) ^ ZCR_SEED2));
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    }
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    init_keys(passwd, pkeys, pcrc_32_tab);
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    for (n = 0; n < RAND_HEAD_LEN-2; n++)
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    {
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        c = (rand() >> 7) & 0xff;
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        header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
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    }
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    /* Encrypt random header (last two bytes is high word of crc) */
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    init_keys(passwd, pkeys, pcrc_32_tab);
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    for (n = 0; n < RAND_HEAD_LEN-2; n++)
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    {
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        buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
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    }
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    buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
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    buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
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    return n;
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}
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#endif
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