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  */

    37 static 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  */

    51 static 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  */

    68 static 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 

    93 static 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