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'use strict';
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const md5 = require('md5');
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const microtime = function() {
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let unixtimeMs = new Date().getTime();
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let sec = parseInt(unixtimeMs / 1000, 10);
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return (unixtimeMs - (sec * 1000)) / 1000 + ' ' + sec;
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};
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const getTimestamp = function() {
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let unixtimeMs = new Date().getTime();
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return parseInt(unixtimeMs / 1000, 10);
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};
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module.exports = function(str, key, expiry, operation) {
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operation = operation ? operation : 'decode';
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key = key ? key : '';
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expiry = expiry ? expiry : 0;
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let tmpstr, tmp;
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let ckeyLength = 4;
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key = md5(key);
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// 密匙a会参与加解密
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let keya = md5(key.substr(0, 16));
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// 密匙b会用来做数据完整性验证
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let keyb = md5(key.substr(16, 16));
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// 密匙c用于变化生成的密文
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let keyc = operation === 'decode' ?
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str.substr(0, ckeyLength) : md5(microtime()).substr(-ckeyLength);
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// 参与运算的密匙
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let cryptkey = keya + md5(keya + keyc);
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let strbuf;
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if (operation === 'decode') {
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str = str.substr(ckeyLength);
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strbuf = new Buffer(str, 'base64');
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// string = b.toString();
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} else {
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expiry = expiry ? expiry + getTimestamp() : 0;
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tmpstr = expiry.toString();
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if (tmpstr.length >= 10) {
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str = tmpstr.substr(0, 10) + md5(str + keyb).substr(0, 16) + str;
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} else {
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let count = 10 - tmpstr.length;
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for (let i = 0; i < count; i++) {
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tmpstr = '0' + tmpstr;
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}
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str = tmpstr + md5(str + keyb).substr(0, 16) + str;
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}
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strbuf = new Buffer(str);
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}
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let box = new Array(256);
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let rndkey = [];
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for (let i = 0; i < 256; i++) {
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box[i] = i;
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// 产生密匙簿
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rndkey[i] = cryptkey.charCodeAt(i % cryptkey.length);
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}
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// 用固定的算法，打乱密匙簿，增加随机性，好像很复杂，实际上对并不会增加密文的强度
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for (let j = 0, i = 0; i < 256; i++) {
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j = (j + box[i] + rndkey[i]) % 256;
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tmp = box[i];
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box[i] = box[j];
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box[j] = tmp;
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}
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// 核心加解密部分
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let s = '';
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for (let a = 0, j = 0, i = 0; i < strbuf.length; i++) {
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a = (a + 1) % 256;
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j = (j + box[a]) % 256;
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tmp = box[a];
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box[a] = box[j];
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box[j] = tmp;
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// 从密匙簿得出密匙进行异或，再转成字符
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// s += String.fromCharCode(string[i] ^ (box[(box[a] + box[j]) % 256]));
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/* jshint -W016*/
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strbuf[i] = strbuf[i] ^ (box[(box[a] + box[j]) % 256]);
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}
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if (operation === 'decode') {
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s = strbuf.toString();
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if ((s.substr(0, 10) === '0'.repeat(10) ||
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s.substr(0, 10) - getTimestamp() > 0) &&
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s.substr(10, 16) === md5(s.substr(26) + keyb).substr(0, 16)) {
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s = s.substr(26);
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} else {
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s = '';
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}
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} else {
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s = strbuf.toString('base64');
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let regex = new RegExp('=', 'g');
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s = s.replace(regex, '');
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s = keyc + s;
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}
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return s;
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}; |
...
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...
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