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/src/libtomahawk/thirdparty/quazip/quazip/crypt.h

http://github.com/tomahawk-player/tomahawk
C++ Header | 135 lines | 73 code | 15 blank | 47 comment | 7 complexity | 659eb6a99fda4c7603a4497a8f93e803 MD5 | raw file
  1/* crypt.h -- base code for crypt/uncrypt ZIPfile
  2
  3
  4   Version 1.01e, February 12th, 2005
  5
  6   Copyright (C) 1998-2005 Gilles Vollant
  7
  8   This code is a modified version of crypting code in Infozip distribution
  9
 10   The encryption/decryption parts of this source code (as opposed to the
 11   non-echoing password parts) were originally written in Europe.  The
 12   whole source package can be freely distributed, including from the USA.
 13   (Prior to January 2000, re-export from the US was a violation of US law.)
 14
 15   This encryption code is a direct transcription of the algorithm from
 16   Roger Schlafly, described by Phil Katz in the file appnote.txt.  This
 17   file (appnote.txt) is distributed with the PKZIP program (even in the
 18   version without encryption capabilities).
 19
 20   If you don't need crypting in your application, just define symbols
 21   NOCRYPT and NOUNCRYPT.
 22
 23   This code support the "Traditional PKWARE Encryption".
 24
 25   The new AES encryption added on Zip format by Winzip (see the page
 26   http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
 27   Encryption is not supported.
 28*/
 29
 30#include "quazip_global.h"
 31
 32#define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
 33
 34/***********************************************************************
 35 * Return the next byte in the pseudo-random sequence
 36 */
 37static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab UNUSED)
 38{
 39    //(void) pcrc_32_tab; /* avoid "unused parameter" warning */
 40    unsigned temp;  /* POTENTIAL BUG:  temp*(temp^1) may overflow in an
 41                     * unpredictable manner on 16-bit systems; not a problem
 42                     * with any known compiler so far, though */
 43
 44    temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
 45    return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
 46}
 47
 48/***********************************************************************
 49 * Update the encryption keys with the next byte of plain text
 50 */
 51static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c)
 52{
 53    (*(pkeys+0)) = CRC32((*(pkeys+0)), c);
 54    (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
 55    (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
 56    {
 57      register int keyshift = (int)((*(pkeys+1)) >> 24);
 58      (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
 59    }
 60    return c;
 61}
 62
 63
 64/***********************************************************************
 65 * Initialize the encryption keys and the random header according to
 66 * the given password.
 67 */
 68static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab)
 69{
 70    *(pkeys+0) = 305419896L;
 71    *(pkeys+1) = 591751049L;
 72    *(pkeys+2) = 878082192L;
 73    while (*passwd != '\0') {
 74        update_keys(pkeys,pcrc_32_tab,(int)*passwd);
 75        passwd++;
 76    }
 77}
 78
 79#define zdecode(pkeys,pcrc_32_tab,c) \
 80    (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
 81
 82#define zencode(pkeys,pcrc_32_tab,c,t) \
 83    (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
 84
 85#ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
 86
 87#define RAND_HEAD_LEN  12
 88   /* "last resort" source for second part of crypt seed pattern */
 89#  ifndef ZCR_SEED2
 90#    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
 91#  endif
 92
 93static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting)
 94    const char *passwd;         /* password string */
 95    unsigned char *buf;         /* where to write header */
 96    int bufSize;
 97    unsigned long* pkeys;
 98    const unsigned long* pcrc_32_tab;
 99    unsigned long crcForCrypting;
100{
101    int n;                       /* index in random header */
102    int t;                       /* temporary */
103    int c;                       /* random byte */
104    unsigned char header[RAND_HEAD_LEN-2]; /* random header */
105    static unsigned calls = 0;   /* ensure different random header each time */
106
107    if (bufSize<RAND_HEAD_LEN)
108      return 0;
109
110    /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
111     * output of rand() to get less predictability, since rand() is
112     * often poorly implemented.
113     */
114    if (++calls == 1)
115    {
116        srand((unsigned)(time(NULL) ^ ZCR_SEED2));
117    }
118    init_keys(passwd, pkeys, pcrc_32_tab);
119    for (n = 0; n < RAND_HEAD_LEN-2; n++)
120    {
121        c = (rand() >> 7) & 0xff;
122        header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
123    }
124    /* Encrypt random header (last two bytes is high word of crc) */
125    init_keys(passwd, pkeys, pcrc_32_tab);
126    for (n = 0; n < RAND_HEAD_LEN-2; n++)
127    {
128        buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
129    }
130    buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
131    buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
132    return n;
133}
134
135#endif