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1 // Crypto/ZipCrypto.cpp
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2
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3 #include "StdAfx.h"
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4
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5 extern "C"
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6 {
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7 #include "../../../C/7zCrc.h"
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8 }
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9
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10 #include "../Common/StreamUtils.h"
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11
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12 #include "RandGen.h"
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13 #include "ZipCrypto.h"
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14
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15 namespace NCrypto {
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16 namespace NZip {
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17
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18 void CCipher::UpdateKeys(Byte b)
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19 {
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20 Keys[0] = CRC_UPDATE_BYTE(Keys[0], b);
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21 Keys[1] += Keys[0] & 0xff;
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22 Keys[1] = Keys[1] * 134775813L + 1;
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23 Keys[2] = CRC_UPDATE_BYTE(Keys[2], (Byte)(Keys[1] >> 24));
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24 }
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25
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26 void CCipher::SetPassword(const Byte *password, UInt32 passwordLen)
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27 {
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28 Keys[0] = 305419896L;
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29 Keys[1] = 591751049L;
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30 Keys[2] = 878082192L;
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31 for (UInt32 i = 0; i < passwordLen; i++)
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32 UpdateKeys(password[i]);
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33 }
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34
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35 Byte CCipher::DecryptByteSpec()
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36 {
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37 UInt32 temp = Keys[2] | 2;
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38 return (Byte)((temp * (temp ^ 1)) >> 8);
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39 }
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40
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41 Byte CCipher::DecryptByte(Byte b)
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42 {
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43 Byte c = (Byte)(b ^ DecryptByteSpec());
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44 UpdateKeys(c);
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45 return c;
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46 }
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47
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48 Byte CCipher::EncryptByte(Byte b)
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49 {
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50 Byte c = (Byte)(b ^ DecryptByteSpec());
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51 UpdateKeys(b);
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52 return c;
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53 }
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54
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55 void CCipher::DecryptHeader(Byte *buf)
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56 {
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57 for (unsigned i = 0; i < kHeaderSize; i++)
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58 buf[i] = DecryptByte(buf[i]);
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59 }
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60
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61 void CCipher::EncryptHeader(Byte *buf)
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62 {
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63 for (unsigned i = 0; i < kHeaderSize; i++)
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64 buf[i] = EncryptByte(buf[i]);
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65 }
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66
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67 STDMETHODIMP CEncoder::CryptoSetPassword(const Byte *data, UInt32 size)
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68 {
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69 _cipher.SetPassword(data, size);
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70 return S_OK;
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71 }
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72
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73 STDMETHODIMP CEncoder::CryptoSetCRC(UInt32 crc)
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74 {
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75 _crc = crc;
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76 return S_OK;
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77 }
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78
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79 STDMETHODIMP CEncoder::Init()
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80 {
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81 return S_OK;
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82 }
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83
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84 HRESULT CEncoder::WriteHeader(ISequentialOutStream *outStream)
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85 {
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86 Byte header[kHeaderSize];
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87 g_RandomGenerator.Generate(header, kHeaderSize - 2);
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88
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89 header[kHeaderSize - 1] = Byte(_crc >> 24);
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90 header[kHeaderSize - 2] = Byte(_crc >> 16);
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91
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92 _cipher.EncryptHeader(header);
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93 return WriteStream(outStream, header, kHeaderSize);
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94 }
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95
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96 STDMETHODIMP_(UInt32) CEncoder::Filter(Byte *data, UInt32 size)
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97 {
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98 UInt32 i;
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99 for (i = 0; i < size; i++)
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100 data[i] = _cipher.EncryptByte(data[i]);
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101 return i;
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102 }
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103
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104 STDMETHODIMP CDecoder::CryptoSetPassword(const Byte *data, UInt32 size)
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105 {
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106 _cipher.SetPassword(data, size);
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107 return S_OK;
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108 }
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109
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110 HRESULT CDecoder::ReadHeader(ISequentialInStream *inStream)
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111 {
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112 Byte header[kHeaderSize];
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113 RINOK(ReadStream_FAIL(inStream, header, kHeaderSize));
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114 _cipher.DecryptHeader(header);
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115 return S_OK;
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116 }
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117
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118 STDMETHODIMP CDecoder::Init()
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119 {
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120 return S_OK;
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121 }
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122
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123 STDMETHODIMP_(UInt32) CDecoder::Filter(Byte *data, UInt32 size)
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124 {
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125 UInt32 i;
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126 for (i = 0; i < size; i++)
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127 data[i] = _cipher.DecryptByte(data[i]);
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128 return i;
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129 }
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130
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131 }}
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