common/dist/zlib/contrib/minizip/crypt.h

   1 /*      $NetBSD: crypt.h,v 1.1.1.1 2006/01/14 20:10:57 christos Exp $   */
   2
   3 /* crypt.h -- base code for crypt/uncrypt ZIPfile
   4
   5
   6    Version 1.01e, February 12th, 2005
   7
   8    Copyright (C) 1998-2005 Gilles Vollant
   9
  10    This code is a modified version of crypting code in Infozip distribution
  11
  12    The encryption/decryption parts of this source code (as opposed to the
  13    non-echoing password parts) were originally written in Europe.  The
  14    whole source package can be freely distributed, including from the USA.
  15    (Prior to January 2000, re-export from the US was a violation of US law.)
  16
  17    This encryption code is a direct transcription of the algorithm from
  18    Roger Schlafly, described by Phil Katz in the file appnote.txt.  This
  19    file (appnote.txt) is distributed with the PKZIP program (even in the
  20    version without encryption capabilities).
  21
  22    If you don't need crypting in your application, just define symbols
  23    NOCRYPT and NOUNCRYPT.
  24
  25    This code support the "Traditional PKWARE Encryption".
  26
  27    The new AES encryption added on Zip format by Winzip (see the page
  28    http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
  29    Encryption is not supported.
  30 */
  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  */
  37 static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab)
  38 {
  39     unsigned temp;  /* POTENTIAL BUG:  temp*(temp^1) may overflow in an
  40                      * unpredictable manner on 16-bit systems; not a problem
  41                      * with any known compiler so far, though */
  42
  43     temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
  44     return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
  45 }
  46
  47 /***********************************************************************
  48  * Update the encryption keys with the next byte of plain text
  49  */
  50 static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c)
  51 {
  52     (*(pkeys+0)) = CRC32((*(pkeys+0)), c);
  53     (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
  54     (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
  55     {
  56       register int keyshift = (int)((*(pkeys+1)) >> 24);
  57       (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
  58     }
  59     return c;
  60 }
  61
  62
  63 /***********************************************************************
  64  * Initialize the encryption keys and the random header according to
  65  * the given password.
  66  */
  67 static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab)
  68 {
  69     *(pkeys+0) = 305419896L;
  70     *(pkeys+1) = 591751049L;
  71     *(pkeys+2) = 878082192L;
  72     while (*passwd != '\0') {
  73         update_keys(pkeys,pcrc_32_tab,(int)*passwd);
  74         passwd++;
  75     }
  76 }
  77
  78 #define zdecode(pkeys,pcrc_32_tab,c) \
  79     (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
  80
  81 #define zencode(pkeys,pcrc_32_tab,c,t) \
  82     (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
  83
  84 #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
  85
  86 #define RAND_HEAD_LEN  12
  87    /* "last resort" source for second part of crypt seed pattern */
  88 #  ifndef ZCR_SEED2
  89 #    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
  90 #  endif
  91
  92 static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting)
  93     const char *passwd;         /* password string */
  94     unsigned char *buf;         /* where to write header */
  95     int bufSize;
  96     unsigned long* pkeys;
  97     const unsigned long* pcrc_32_tab;
  98     unsigned long crcForCrypting;
  99 {
 100     int n;                       /* index in random header */
 101     int t;                       /* temporary */
 102     int c;                       /* random byte */
 103     unsigned char header[RAND_HEAD_LEN-2]; /* random header */
 104     static unsigned calls = 0;   /* ensure different random header each time */
 105
 106     if (bufSize<RAND_HEAD_LEN)
 107       return 0;
 108
 109     /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
 110      * output of rand() to get less predictability, since rand() is
 111      * often poorly implemented.
 112      */
 113     if (++calls == 1)
 114     {
 115         srand((unsigned)(time(NULL) ^ ZCR_SEED2));
 116     }
 117     init_keys(passwd, pkeys, pcrc_32_tab);
 118     for (n = 0; n < RAND_HEAD_LEN-2; n++)
 119     {
 120         c = (rand() >> 7) & 0xff;
 121         header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
 122     }
 123     /* Encrypt random header (last two bytes is high word of crc) */
 124     init_keys(passwd, pkeys, pcrc_32_tab);
 125     for (n = 0; n < RAND_HEAD_LEN-2; n++)
 126     {
 127         buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
 128     }
 129     buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
 130     buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
 131     return n;
 132 }
 133
 134 #endif