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5ca28f79 L |
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 | */ | |
da09a436 | 35 | static int decrypt_byte(unsigned long* pkeys, const z_crc_t* pcrc_32_tab) |
5ca28f79 L |
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 | */ | |
da09a436 | 48 | static int update_keys(unsigned long* pkeys,const z_crc_t* pcrc_32_tab,int c) |
5ca28f79 L |
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 | */ | |
da09a436 | 65 | static void init_keys(const char* passwd,unsigned long* pkeys,const z_crc_t* pcrc_32_tab) |
5ca28f79 L |
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(const char* passwd, /* password string */ | |
91 | unsigned char* buf, /* where to write header */ | |
92 | int bufSize, | |
93 | unsigned long* pkeys, | |
da09a436 | 94 | const z_crc_t* pcrc_32_tab, |
5ca28f79 L |
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 | { | |
112 | srand((unsigned)(time(NULL) ^ ZCR_SEED2)); | |
113 | } | |
114 | init_keys(passwd, pkeys, pcrc_32_tab); | |
115 | for (n = 0; n < RAND_HEAD_LEN-2; n++) | |
116 | { | |
117 | c = (rand() >> 7) & 0xff; | |
118 | header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t); | |
119 | } | |
120 | /* Encrypt random header (last two bytes is high word of crc) */ | |
121 | init_keys(passwd, pkeys, pcrc_32_tab); | |
122 | for (n = 0; n < RAND_HEAD_LEN-2; n++) | |
123 | { | |
124 | buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t); | |
125 | } | |
126 | buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t); | |
127 | buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t); | |
128 | return n; | |
129 | } | |
130 | ||
131 | #endif |