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 */
37static 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 */
50static 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 */
67static 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
92static 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
135