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1 /* crypt.h -- base code for crypt/uncrypt ZIPfile |
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2 |
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3 |
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4 Version 1.01e, February 12th, 2005 |
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5 |
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6 Copyright (C) 1998-2005 Gilles Vollant |
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7 |
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8 This code is a modified version of crypting code in Infozip distribution |
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9 |
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10 The encryption/decryption parts of this source code (as opposed to the |
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11 non-echoing password parts) were originally written in Europe. The |
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12 whole source package can be freely distributed, including from the USA. |
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13 (Prior to January 2000, re-export from the US was a violation of US law.) |
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14 |
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15 This encryption code is a direct transcription of the algorithm from |
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16 Roger Schlafly, described by Phil Katz in the file appnote.txt. This |
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17 file (appnote.txt) is distributed with the PKZIP program (even in the |
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18 version without encryption capabilities). |
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19 |
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20 If you don't need crypting in your application, just define symbols |
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21 NOCRYPT and NOUNCRYPT. |
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22 |
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23 This code support the "Traditional PKWARE Encryption". |
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24 |
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25 The new AES encryption added on Zip format by Winzip (see the page |
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26 http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong |
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27 Encryption is not supported. |
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28 */ |
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29 |
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30 #define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8)) |
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31 |
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32 /*********************************************************************** |
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33 * Return the next byte in the pseudo-random sequence |
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34 */ |
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35 static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab) |
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36 { |
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37 unsigned temp; /* POTENTIAL BUG: temp*(temp^1) may overflow in an |
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38 * unpredictable manner on 16-bit systems; not a problem |
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39 * with any known compiler so far, though */ |
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40 |
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41 temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2; |
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42 return (int)(((temp * (temp ^ 1)) >> 8) & 0xff); |
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43 } |
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44 |
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45 /*********************************************************************** |
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46 * Update the encryption keys with the next byte of plain text |
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47 */ |
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48 static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c) |
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49 { |
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50 (*(pkeys+0)) = CRC32((*(pkeys+0)), c); |
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51 (*(pkeys+1)) += (*(pkeys+0)) & 0xff; |
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52 (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1; |
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53 { |
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54 register int keyshift = (int)((*(pkeys+1)) >> 24); |
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55 (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift); |
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56 } |
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57 return c; |
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58 } |
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59 |
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60 |
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61 /*********************************************************************** |
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62 * Initialize the encryption keys and the random header according to |
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63 * the given password. |
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64 */ |
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65 static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab) |
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66 { |
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67 *(pkeys+0) = 305419896L; |
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68 *(pkeys+1) = 591751049L; |
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69 *(pkeys+2) = 878082192L; |
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70 while (*passwd != '\0') { |
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71 update_keys(pkeys,pcrc_32_tab,(int)*passwd); |
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72 passwd++; |
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73 } |
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74 } |
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75 |
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76 #define zdecode(pkeys,pcrc_32_tab,c) \ |
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77 (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab))) |
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78 |
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79 #define zencode(pkeys,pcrc_32_tab,c,t) \ |
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80 (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c)) |
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81 |
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82 #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED |
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83 |
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84 #define RAND_HEAD_LEN 12 |
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85 /* "last resort" source for second part of crypt seed pattern */ |
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86 # ifndef ZCR_SEED2 |
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87 # define ZCR_SEED2 3141592654UL /* use PI as default pattern */ |
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88 # endif |
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89 |
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90 static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting) |
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91 const char *passwd; /* password string */ |
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92 unsigned char *buf; /* where to write header */ |
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93 int bufSize; |
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94 unsigned long* pkeys; |
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95 const unsigned long* pcrc_32_tab; |
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96 unsigned long crcForCrypting; |
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97 { |
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98 int n; /* index in random header */ |
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99 int t; /* temporary */ |
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100 int c; /* random byte */ |
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101 unsigned char header[RAND_HEAD_LEN-2]; /* random header */ |
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102 static unsigned calls = 0; /* ensure different random header each time */ |
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103 |
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104 if (bufSize<RAND_HEAD_LEN) |
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105 return 0; |
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106 |
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107 /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the |
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108 * output of rand() to get less predictability, since rand() is |
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109 * often poorly implemented. |
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110 */ |
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111 if (++calls == 1) |
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112 { |
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113 srand((unsigned)(time(NULL) ^ ZCR_SEED2)); |
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114 } |
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115 init_keys(passwd, pkeys, pcrc_32_tab); |
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116 for (n = 0; n < RAND_HEAD_LEN-2; n++) |
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117 { |
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118 c = (rand() >> 7) & 0xff; |
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119 header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t); |
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120 } |
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121 /* Encrypt random header (last two bytes is high word of crc) */ |
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122 init_keys(passwd, pkeys, pcrc_32_tab); |
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123 for (n = 0; n < RAND_HEAD_LEN-2; n++) |
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124 { |
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125 buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t); |
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126 } |
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127 buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t); |
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128 buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t); |
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129 return n; |
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130 } |
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131 |
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132 #endif |