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#define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
31
32/***********************************************************************
33 * Return the next byte in the pseudo-random sequence
34 */
35static int decrypt_byte(unsigned long* pkeys, const z_crc_t* pcrc_32_tab) {
36 unsigned temp; /* POTENTIAL BUG: temp*(temp^1) may overflow in an
37 * unpredictable manner on 16-bit systems; not a problem
38 * with any known compiler so far, though */
39
40 (void)pcrc_32_tab;
41 temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
42 return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
43}
44
45/***********************************************************************
46 * Update the encryption keys with the next byte of plain text
47 */
48static int update_keys(unsigned long* pkeys, const z_crc_t* pcrc_32_tab, int c) {
49 (*(pkeys+0)) = CRC32((*(pkeys+0)), c);
50 (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
51 (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
52 {
53 register int keyshift = (int)((*(pkeys+1)) >> 24);
54 (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
55 }
56 return c;
57}
58
59
60/***********************************************************************
61 * Initialize the encryption keys and the random header according to
62 * the given password.
63 */
64static void init_keys(const char* passwd, unsigned long* pkeys, const z_crc_t* pcrc_32_tab) {
65 *(pkeys+0) = 305419896L;
66 *(pkeys+1) = 591751049L;
67 *(pkeys+2) = 878082192L;
68 while (*passwd != '\0') {
69 update_keys(pkeys,pcrc_32_tab,(int)*passwd);
70 passwd++;
71 }
72}
73
74#define zdecode(pkeys,pcrc_32_tab,c) \
75 (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
76
77#define zencode(pkeys,pcrc_32_tab,c,t) \
78 (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), (Byte)t^(c))
79
80#ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
81
82#define RAND_HEAD_LEN 12
83 /* "last resort" source for second part of crypt seed pattern */
84# ifndef ZCR_SEED2
85# define ZCR_SEED2 3141592654UL /* use PI as default pattern */
86# endif
87
88static unsigned crypthead(const char* passwd, /* password string */
89 unsigned char* buf, /* where to write header */
90 int bufSize,
91 unsigned long* pkeys,
92 const z_crc_t* pcrc_32_tab,
93 unsigned long crcForCrypting) {
94 unsigned n; /* index in random header */
95 int t; /* temporary */
96 int c; /* random byte */
97 unsigned char header[RAND_HEAD_LEN-2]; /* random header */
98 static unsigned calls = 0; /* ensure different random header each time */
99
100 if (bufSize<RAND_HEAD_LEN)
101 return 0;
102
103 /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
104 * output of rand() to get less predictability, since rand() is
105 * often poorly implemented.
106 */
107 if (++calls == 1)
108 {
109 srand((unsigned)(time(NULL) ^ ZCR_SEED2));
110 }
111 init_keys(passwd, pkeys, pcrc_32_tab);
112 for (n = 0; n < RAND_HEAD_LEN-2; n++)
113 {
114 c = (rand() >> 7) & 0xff;
115 header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
116 }
117 /* Encrypt random header (last two bytes is high word of crc) */
118 init_keys(passwd, pkeys, pcrc_32_tab);
119 for (n = 0; n < RAND_HEAD_LEN-2; n++)
120 {
121 buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
122 }
123 buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
124 buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
125 return n;
126}
127
128#endif
129