Parent Directory | Revision Log
Initial import
1 | harbaum | 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 | */ | ||
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 | */ | ||
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 | /*********************************************************************** | ||
62 | * Initialize the encryption keys and the random header according to | ||
63 | * the given password. | ||
64 | */ | ||
65 | static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab) | ||
66 | { | ||
67 | *(pkeys+0) = 305419896L; | ||
68 | *(pkeys+1) = 591751049L; | ||
69 | *(pkeys+2) = 878082192L; | ||
70 | while (*passwd != '\0') { | ||
71 | update_keys(pkeys,pcrc_32_tab,(int)*passwd); | ||
72 | passwd++; | ||
73 | } | ||
74 | } | ||
75 | |||
76 | #define zdecode(pkeys,pcrc_32_tab,c) \ | ||
77 | (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab))) | ||
78 | |||
79 | #define zencode(pkeys,pcrc_32_tab,c,t) \ | ||
80 | (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c)) | ||
81 | |||
82 | #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED | ||
83 | |||
84 | #define RAND_HEAD_LEN 12 | ||
85 | /* "last resort" source for second part of crypt seed pattern */ | ||
86 | # ifndef ZCR_SEED2 | ||
87 | # define ZCR_SEED2 3141592654UL /* use PI as default pattern */ | ||
88 | # endif | ||
89 | |||
90 | static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting) | ||
91 | const char *passwd; /* password string */ | ||
92 | unsigned char *buf; /* where to write header */ | ||
93 | int bufSize; | ||
94 | unsigned long* pkeys; | ||
95 | const unsigned long* pcrc_32_tab; | ||
96 | unsigned long crcForCrypting; | ||
97 | { | ||
98 | int n; /* index in random header */ | ||
99 | int t; /* temporary */ | ||
100 | int c; /* random byte */ | ||
101 | unsigned char header[RAND_HEAD_LEN-2]; /* random header */ | ||
102 | static unsigned calls = 0; /* ensure different random header each time */ | ||
103 | |||
104 | if (bufSize<RAND_HEAD_LEN) | ||
105 | return 0; | ||
106 | |||
107 | /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the | ||
108 | * output of rand() to get less predictability, since rand() is | ||
109 | * often poorly implemented. | ||
110 | */ | ||
111 | if (++calls == 1) | ||
112 | { | ||
113 | srand((unsigned)(time(NULL) ^ ZCR_SEED2)); | ||
114 | } | ||
115 | init_keys(passwd, pkeys, pcrc_32_tab); | ||
116 | for (n = 0; n < RAND_HEAD_LEN-2; n++) | ||
117 | { | ||
118 | c = (rand() >> 7) & 0xff; | ||
119 | header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t); | ||
120 | } | ||
121 | /* Encrypt random header (last two bytes is high word of crc) */ | ||
122 | init_keys(passwd, pkeys, pcrc_32_tab); | ||
123 | for (n = 0; n < RAND_HEAD_LEN-2; n++) | ||
124 | { | ||
125 | buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t); | ||
126 | } | ||
127 | buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t); | ||
128 | buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t); | ||
129 | return n; | ||
130 | } | ||
131 | |||
132 | #endif |