| commit | author | age | ||
| 6e1425 | 1 | /* crypt.h -- base code for crypt/uncrypt ZIPfile |
| H | 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 | |
