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| 1 | +/* crypt.h -- base code for crypt/uncrypt ZIPfile |
| 2 | +
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| 3 | +
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| 4 | + Version 1.01e, February 12th, 2005 |
| 5 | +
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| 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 z_crc_t* 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 z_crc_t* 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 z_crc_t* 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(const char* passwd, /* password string */ |
| 91 | + unsigned char* buf, /* where to write header */ |
| 92 | + int bufSize, |
| 93 | + unsigned long* pkeys, |
| 94 | + const z_crc_t* 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 | + { |
| 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 |
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