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| 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 lon
g* 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 |
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