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