wx/lib/wx-msg-crypt.js

W(ei)X(in) -- (minimalist) WeChat Middleware for Express.js

// Generated by CoffeeScript 1.10.0
(function() {
  var PKCS7, Prpcrypt, WXBizMsgCrypt, crypto, generated_signature, xml2js;

  crypto = require('crypto');

  xml2js = require('xml2js');

  PKCS7 = (function() {
    var block_size;
    block_size = 32;
    return {
      encode: function(data) {
        var amount_to_pad, buf;
        amount_to_pad = block_size - (data.length % block_size);
        if (amount_to_pad === 0) {
          amount_to_pad = block_size;
        }
        buf = new Buffer(amount_to_pad);
        buf.fill(String.fromCharCode(amount_to_pad));
        return Buffer.concat([data, buf]);
      },
      decode: function(data) {
        var pad;
        pad = data.readUInt8(data.length - 1);
        if (pad < 1 || pad > 32) {
          pad = 0;
        }
        return data.slice(0, data.length - pad);
      }
    };
  })();

  Prpcrypt = (function() {
    var get_random_str;

    function Prpcrypt(key) {
      this.key = new Buffer(key + '=', 'base64');
    }

    get_random_str = function() {
      var i, j, str, str_pol;
      str = '';
      str_pol = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
      for (i = j = 0; j <= 15; i = ++j) {
        str += str_pol[parseInt(Math.random() * str_pol.length)];
      }
      return str;
    };

    Prpcrypt.prototype.encrypt = function(text, appid) {
      var buf, cipher, cipherChunks, iv, msg_len;
      msg_len = 16 + 4 + Buffer.byteLength(text) + appid.length;
      buf = new Buffer(msg_len);
      buf.write(get_random_str(), 0);
      buf.writeUInt32BE(Buffer.byteLength(text), 16);
      buf.write(text, 20);
      buf.write(appid, Buffer.byteLength(text) + 20);
      iv = this.key.slice(0, 16);
      buf = PKCS7.encode(buf);
      cipher = crypto.createCipheriv('aes-256-cbc', this.key, iv);
      cipher.setAutoPadding(false);
      cipherChunks = [cipher.update(buf, 'binary', 'base64'), cipher.final('base64')];
      return cipherChunks.join('');
    };

    Prpcrypt.prototype.decrypt = function(text, appid) {
      var buf, decipher, iv, plainChunks;
      iv = this.key.slice(0, 16);
      decipher = crypto.createDecipheriv('aes-256-cbc', this.key, iv);
      decipher.setAutoPadding(false);
      plainChunks = [decipher.update(text, 'base64'), decipher.final()];
      buf = Buffer.concat(plainChunks);
      buf = PKCS7.decode(buf);
      buf = buf.slice(20, buf.length - appid.length);
      return buf.toString('utf8');
    };

    return Prpcrypt;

  })();

  generated_signature = function(token, timestamp, nonce, encrypt) {
    var sha1;
    sha1 = crypto.createHash('sha1');
    sha1.update([token, timestamp, nonce, encrypt].sort().join(''));
    return sha1.digest('hex');
  };

  WXBizMsgCrypt = (function() {
    function WXBizMsgCrypt(token1, key1, appId) {
      this.token = token1;
      this.key = key1;
      this.appId = appId;
      if (this.key.length !== 43) {
        throw 'Key is not valid.';
      }
    }

    WXBizMsgCrypt.prototype.encrypt = function(msg, timestamp, nonce) {
      var encrypt, pc, signature;
      pc = new Prpcrypt(this.key);
      encrypt = pc.encrypt(msg, this.appId);
      signature = generated_signature(this.token, timestamp, nonce, encrypt);
      return "<xml> <Encrypt><![CDATA[" + encrypt + "]]></Encrypt> <MsgSignature><![CDATA[" + signature + "]]></MsgSignature> <TimeStamp>" + timestamp + "</TimeStamp> <Nonce><![CDATA[" + nonce + "]]></Nonce> </xml>";
    };

    WXBizMsgCrypt.prototype.decrypt = function(msg, callback) {
      return xml2js.parseString(msg, (function(_this) {
        return function(err, result) {
          var pc, xml;
          if (err) {
            throw err;
          }
          xml = result.xml;
          if (xml.Encrypt) {
            pc = new Prpcrypt(_this.key);
            return xml2js.parseString(pc.decrypt(xml.Encrypt[0], _this.appId), callback);
          } else {
            return callback('Not encrypted.', null);
          }
        };
      })(this));
    };

    return WXBizMsgCrypt;

  })();

  module.exports = WXBizMsgCrypt;

}).call(this);