微信公众号消息加密解密nodejs模块

wxcrypto.js

const crypto = require('crypto');
const debug = require('debug')('wxcrypto');

/**
 * 微信公众号消息加密解密，支持 node > 8.0
 *
 * var WXCrypto = require('this module');
 * var wx = new WXCrypto(token, aesKey, appid);
 *
 * var [err, encryptedXML] = wx.encrypt(xml, timestamp, nonce);
 *
 * var [err, decryptedXML] = wx.decrypt(signature, timestamp, nonce, encrypted);
 *
 *
 * thanks:
 * http://my.oschina.net/u/2324376/blog/397296
 * 
 */

class encryptMessage {

	constructor(token, key, appid) {
		this.token = token;
		this.key = key;
		this.appid = appid;
		debug('wechat crypto class initiaed with token=', token, 'key=', key, 'appid=', appid);
	}

	//sha1摘要算法
	sha1() {
		let args = Array.prototype.slice.call(arguments);
		args.sort(function(a,b) {
			a = a.toString();
			b = b.toString();
			return a>b?1:a<b?-1:0;
		});
		return crypto.createHash('sha1').update(args.join('')).digest("hex");
	}

	//加密消息
	encrypt(text, timestamp, nonce) {
		var prp = new prpcrypt(this.key);
		var re = prp.encrypt(text, this.appid);
		if (re[0]) return re;
		var encrypted = re[1];
		var hash = this.sha1(this.token, timestamp, nonce, encrypted);

		var xml = `<xml>
<Encrypt><![CDATA[${encrypted}]]></Encrypt>
<MsgSignature><![CDATA[${hash}]]></MsgSignature>
<TimeStamp>${timestamp}</TimeStamp>
<Nonce><![CDATA[${nonce}]]></Nonce>
</xml>`;

		return [false, xml];
	}

	//解密消息
	decrypt(hash, timestamp, nonce, xml) {
		debug('begin decrypt', 'hash=', hash, 'timestamp=', timestamp, 'nonce=', nonce, 'xml=', xml);
		var obj = this.parseWechatXML(xml);
		debug('parsed xml=', obj);
		if (!obj || !obj.Encrypt) return [true, 'wrong xml format, no Encrypt child'];
		var _hash = this.sha1(this.token, timestamp, nonce, obj.Encrypt);
		debug('calculated hash=', _hash);
		if (hash != _hash) return [true, 'signature not match'];
		var prp = new prpcrypt(this.key);
		return prp.decrypt(obj.Encrypt, this.appid);
	}

	//解析微信xml
	parseWechatXML(xml) {
		if (!xml || typeof xml != 'string') return {};
		var re = {};
		xml = xml.replace(/^<xml>|<\/xml>$/g, '');
		var ms = xml.match(/<([a-z0-9]+)>([\s\S]*?)<\/\1>/ig);
		if (ms && ms.length > 0) {
			ms.forEach( t => {
				let ms = t.match(/<([a-z0-9]+)>([\s\S]*?)<\/\1>/i);
				let tagName = ms[1];
				let cdata = ms[2] || '';
				cdata = cdata.replace(/^\s*<\!\[CDATA\[\s*|\s*\]\]>\s*$/g,'');
				re[tagName] = cdata;
			});
		}
		return re;
	}
}


class prpcrypt
{
	constructor(k)
	{
		this.key = new Buffer(k + '=', 'base64');//.toString('binary');
		this.mode = 'aes-256-cbc';
		this.iv = this.key.toString('hex').slice(0, 16);
	}

	encrypt(text, appid)
	{
		var text = new Buffer(text),
			pad = this.enclen(text.length);
		var pack = new PKCS7().encode(20 + text.length + appid.length),
			random = this.getRandomStr(),
			content = random + pad + text.toString('binary') + appid + pack;
		try {
			var cipher = crypto.createCipheriv(this.mode, this.key, this.iv);
			cipher.setAutoPadding(false);
			var crypted = cipher.update(content, 'binary', 'base64') + cipher.final('base64');
			return [false, crypted];
		} catch (e) {
			console.error(e);
			return [true, e];
		}
	}

	decrypt(encrypted, appid) 
	{
		var decipher, plain_text;
		try {
			decipher = crypto.Decipheriv(this.mode, this.key, this.iv);
			decipher.setAutoPadding(false);
			plain_text = decipher.update(encrypted, 'base64');
			plain_text = Buffer.concat([plain_text, decipher.final()]);
		} catch (e) {
			console.error(e);
			return [true, e];
		}
		var pad = plain_text[plain_text.length - 1];
		if (pad < 1 || pad > 32) pad = 0;
		plain_text = plain_text.slice(20, -pad).toString('utf8').replace(/<\/xml>.*/,'</xml>');
		debug('plain_text=', plain_text);
		return [false, plain_text];
	}

	enclen(len)
	{
		var buf = new Buffer(4);
		buf.writeUInt32BE(len);
		return buf.toString('binary');
	}

	getRandomStr()
	{
		var pool = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
		var re = '';
		for(var i=0;i<16;i++)
		{
			re += pool.charAt(Math.random()*pool.length);
		}
		return re;
	}
}

class PKCS7
{
	constructor() 
	{
		this.block_size = 32;
	}

	encode (text_length)
	{
		// 计算需要填充的位数
		var amount_to_pad = this.block_size - (text_length % this.block_size);
		if (amount_to_pad === 0) 
		{
			amount_to_pad = this.block_size;
		}

		// 获得补位所用的字符
		var pad = String.fromCharCode(amount_to_pad), s = [];
		//console.log('pad:', amount_to_pad, pad);
		for (var i=0; i<amount_to_pad; i++) s.push(pad);
		return s.join('');
	}
}



module.exports = encryptMessage;

var [err, decryptedXML] = wx.decrypt(signature, timestamp, nonce, encrypted); signature可以改成msg_signature 。url返回有个signature我用这个一直报错，改成 msg_signature 这个更为直观点，不让大家踩坑