cannam@128: /* crypt.h -- base code for crypt/uncrypt ZIPfile
cannam@128: 
cannam@128: 
cannam@128:    Version 1.01e, February 12th, 2005
cannam@128: 
cannam@128:    Copyright (C) 1998-2005 Gilles Vollant
cannam@128: 
cannam@128:    This code is a modified version of crypting code in Infozip distribution
cannam@128: 
cannam@128:    The encryption/decryption parts of this source code (as opposed to the
cannam@128:    non-echoing password parts) were originally written in Europe.  The
cannam@128:    whole source package can be freely distributed, including from the USA.
cannam@128:    (Prior to January 2000, re-export from the US was a violation of US law.)
cannam@128: 
cannam@128:    This encryption code is a direct transcription of the algorithm from
cannam@128:    Roger Schlafly, described by Phil Katz in the file appnote.txt.  This
cannam@128:    file (appnote.txt) is distributed with the PKZIP program (even in the
cannam@128:    version without encryption capabilities).
cannam@128: 
cannam@128:    If you don't need crypting in your application, just define symbols
cannam@128:    NOCRYPT and NOUNCRYPT.
cannam@128: 
cannam@128:    This code support the "Traditional PKWARE Encryption".
cannam@128: 
cannam@128:    The new AES encryption added on Zip format by Winzip (see the page
cannam@128:    http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
cannam@128:    Encryption is not supported.
cannam@128: */
cannam@128: 
cannam@128: #define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
cannam@128: 
cannam@128: /***********************************************************************
cannam@128:  * Return the next byte in the pseudo-random sequence
cannam@128:  */
cannam@128: static int decrypt_byte(unsigned long* pkeys, const z_crc_t* pcrc_32_tab)
cannam@128: {
cannam@128:     unsigned temp;  /* POTENTIAL BUG:  temp*(temp^1) may overflow in an
cannam@128:                      * unpredictable manner on 16-bit systems; not a problem
cannam@128:                      * with any known compiler so far, though */
cannam@128: 
cannam@128:     temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
cannam@128:     return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
cannam@128: }
cannam@128: 
cannam@128: /***********************************************************************
cannam@128:  * Update the encryption keys with the next byte of plain text
cannam@128:  */
cannam@128: static int update_keys(unsigned long* pkeys,const z_crc_t* pcrc_32_tab,int c)
cannam@128: {
cannam@128:     (*(pkeys+0)) = CRC32((*(pkeys+0)), c);
cannam@128:     (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
cannam@128:     (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
cannam@128:     {
cannam@128:       register int keyshift = (int)((*(pkeys+1)) >> 24);
cannam@128:       (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
cannam@128:     }
cannam@128:     return c;
cannam@128: }
cannam@128: 
cannam@128: 
cannam@128: /***********************************************************************
cannam@128:  * Initialize the encryption keys and the random header according to
cannam@128:  * the given password.
cannam@128:  */
cannam@128: static void init_keys(const char* passwd,unsigned long* pkeys,const z_crc_t* pcrc_32_tab)
cannam@128: {
cannam@128:     *(pkeys+0) = 305419896L;
cannam@128:     *(pkeys+1) = 591751049L;
cannam@128:     *(pkeys+2) = 878082192L;
cannam@128:     while (*passwd != '\0') {
cannam@128:         update_keys(pkeys,pcrc_32_tab,(int)*passwd);
cannam@128:         passwd++;
cannam@128:     }
cannam@128: }
cannam@128: 
cannam@128: #define zdecode(pkeys,pcrc_32_tab,c) \
cannam@128:     (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
cannam@128: 
cannam@128: #define zencode(pkeys,pcrc_32_tab,c,t) \
cannam@128:     (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
cannam@128: 
cannam@128: #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
cannam@128: 
cannam@128: #define RAND_HEAD_LEN  12
cannam@128:    /* "last resort" source for second part of crypt seed pattern */
cannam@128: #  ifndef ZCR_SEED2
cannam@128: #    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
cannam@128: #  endif
cannam@128: 
cannam@128: static int crypthead(const char* passwd,      /* password string */
cannam@128:                      unsigned char* buf,      /* where to write header */
cannam@128:                      int bufSize,
cannam@128:                      unsigned long* pkeys,
cannam@128:                      const z_crc_t* pcrc_32_tab,
cannam@128:                      unsigned long crcForCrypting)
cannam@128: {
cannam@128:     int n;                       /* index in random header */
cannam@128:     int t;                       /* temporary */
cannam@128:     int c;                       /* random byte */
cannam@128:     unsigned char header[RAND_HEAD_LEN-2]; /* random header */
cannam@128:     static unsigned calls = 0;   /* ensure different random header each time */
cannam@128: 
cannam@128:     if (bufSize<RAND_HEAD_LEN)
cannam@128:       return 0;
cannam@128: 
cannam@128:     /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
cannam@128:      * output of rand() to get less predictability, since rand() is
cannam@128:      * often poorly implemented.
cannam@128:      */
cannam@128:     if (++calls == 1)
cannam@128:     {
cannam@128:         srand((unsigned)(time(NULL) ^ ZCR_SEED2));
cannam@128:     }
cannam@128:     init_keys(passwd, pkeys, pcrc_32_tab);
cannam@128:     for (n = 0; n < RAND_HEAD_LEN-2; n++)
cannam@128:     {
cannam@128:         c = (rand() >> 7) & 0xff;
cannam@128:         header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
cannam@128:     }
cannam@128:     /* Encrypt random header (last two bytes is high word of crc) */
cannam@128:     init_keys(passwd, pkeys, pcrc_32_tab);
cannam@128:     for (n = 0; n < RAND_HEAD_LEN-2; n++)
cannam@128:     {
cannam@128:         buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
cannam@128:     }
cannam@128:     buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
cannam@128:     buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
cannam@128:     return n;
cannam@128: }
cannam@128: 
cannam@128: #endif