1 | var aes = require('./aes');
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2 | var Transform = require('./cipherBase');
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3 | var inherits = require('inherits');
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4 | var modes = require('./modes');
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5 | var StreamCipher = require('./streamCipher');
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6 | var ebtk = require('./EVP_BytesToKey');
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7 |
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8 | inherits(Decipher, Transform);
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9 | function Decipher(mode, key, iv) {
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10 | if (!(this instanceof Decipher)) {
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11 | return new Decipher(mode, key, iv);
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12 | }
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13 | Transform.call(this);
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14 | this._cache = new Splitter();
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15 | this._last = void 0;
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16 | this._cipher = new aes.AES(key);
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17 | this._prev = new Buffer(iv.length);
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18 | iv.copy(this._prev);
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19 | this._mode = mode;
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20 | }
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21 | Decipher.prototype._transform = function (data, _, next) {
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22 | this._cache.add(data);
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23 | var chunk;
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24 | var thing;
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25 | while ((chunk = this._cache.get())) {
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26 | thing = this._mode.decrypt(this, chunk);
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27 | this.push(thing);
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28 | }
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29 | next();
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30 | };
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31 | Decipher.prototype._flush = function (next) {
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32 | var chunk = this._cache.flush();
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33 | if (!chunk) {
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34 | return next;
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35 | }
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36 |
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37 | this.push(unpad(this._mode.decrypt(this, chunk)));
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38 |
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39 | next();
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40 | };
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41 |
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42 | function Splitter() {
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43 | if (!(this instanceof Splitter)) {
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44 | return new Splitter();
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45 | }
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46 | this.cache = new Buffer('');
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47 | }
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48 | Splitter.prototype.add = function (data) {
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49 | this.cache = Buffer.concat([this.cache, data]);
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50 | };
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51 |
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52 | Splitter.prototype.get = function () {
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53 | if (this.cache.length > 16) {
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54 | var out = this.cache.slice(0, 16);
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55 | this.cache = this.cache.slice(16);
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56 | return out;
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57 | }
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58 | return null;
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59 | };
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60 | Splitter.prototype.flush = function () {
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61 | if (this.cache.length) {
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62 | return this.cache;
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63 | }
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64 | };
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65 | function unpad(last) {
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66 | var padded = last[15];
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67 | if (padded === 16) {
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68 | return;
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69 | }
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70 | return last.slice(0, 16 - padded);
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71 | }
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72 |
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73 | var modelist = {
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74 | ECB: require('./modes/ecb'),
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75 | CBC: require('./modes/cbc'),
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76 | CFB: require('./modes/cfb'),
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77 | OFB: require('./modes/ofb'),
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78 | CTR: require('./modes/ctr')
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79 | };
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80 |
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81 | module.exports = function (crypto) {
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82 | function createDecipheriv(suite, password, iv) {
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83 | var config = modes[suite];
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84 | if (!config) {
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85 | throw new TypeError('invalid suite type');
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86 | }
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87 | if (typeof iv === 'string') {
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88 | iv = new Buffer(iv);
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89 | }
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90 | if (typeof password === 'string') {
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91 | password = new Buffer(password);
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92 | }
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93 | if (password.length !== config.key/8) {
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94 | throw new TypeError('invalid key length ' + password.length);
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95 | }
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96 | if (iv.length !== config.iv) {
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97 | throw new TypeError('invalid iv length ' + iv.length);
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98 | }
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99 | if (config.type === 'stream') {
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100 | return new StreamCipher(modelist[config.mode], password, iv, true);
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101 | }
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102 | return new Decipher(modelist[config.mode], password, iv);
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103 | }
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104 |
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105 | function createDecipher (suite, password) {
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106 | var config = modes[suite];
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107 | if (!config) {
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108 | throw new TypeError('invalid suite type');
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109 | }
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110 | var keys = ebtk(crypto, password, config.key, config.iv);
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111 | return createDecipheriv(suite, keys.key, keys.iv);
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112 | }
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113 | return {
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114 | createDecipher: createDecipher,
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115 | createDecipheriv: createDecipheriv
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116 | };
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117 | };
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