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 */
decrypt_byte(unsigned long * pkeys,const unsigned long * pcrc_32_tab)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 */
update_keys(unsigned long * pkeys,const unsigned long * pcrc_32_tab,int c)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 */
init_keys(const char * passwd,unsigned long * pkeys,const unsigned long * pcrc_32_tab)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
crypthead(passwd,buf,bufSize,pkeys,pcrc_32_tab,crcForCrypting)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
135