使用node-forge保障Javascript应用的传输安全

引子

半年前的最后一次更新（惭愧），提到了对称与非对称的混合加解密系统，点到为止而未涉及实践，今次将就此展开，再续爱丽丝与鲍伯的前缘。

为什么

Javascript应用的安全传输，这事不是有SSL吗，为什么要多此一举呢？好问题，自己实现TSL是因为：

SSL是基于浏览器的，是浏览器负责的安全性，这意味着，非浏览器应用得不到保护，即使你的服务器上安装了证书
SSL需要有明确的CA受信端，自颁发证书的对等端应用，显然是使用不能

那么，这样的场景是需要自实现 TSL 的：一台node服务器和一个electron桌面应用之间的安全通信

怎么做

SSL是怎么做的呢？它的流程和之前提到的混合密码系统是一样：公私钥和对称算法混合应用，在安全和性能之间取得平衡（更为具体的流程请参见 HTTPS/SSL原理及Ruby实现）。

用啥做

既然要保障的是Javascript应用的传输安全，那自然需要在npm上网罗一下，感谢社区，让我找到了 node-forge 。它是这么介绍自己的：

JavaScript implementations of network transports, cryptography, ciphers, PKI, message digests, and various utilities.

功能似乎很全，然后，关于性能，这货在评测中表现颇为优秀：

任何加解密都需要操作 bytes，在node-forge里，也提供了一个byte buffer的实现：ByteStringBuffer，inspect一下，是不是很眼熟：

更多的介绍可参见官方repo文档和 Node.js加解密

动手实践

需求

有一个页面，通过ajax的方式与node的后端通信，我希望能把各种请求(GET/POST/PUT/DELETE)里的某个参数加密（假设为id好了）

准备工作

颁发一对公私钥：

openssl genrsa -out prv.key 
openssl rsa -in prv.key -pubout > pub.key

1 2	openssl genrsa -out prv.key openssl rsa -in prv.key -pubout > pub.key

公钥给页面用来做加密：

-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00
OF66DkWizWoein2b7n/lTUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQ==
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----

MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00

OF66DkWizWoein2b7n/lTUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQ==

-----END PUBLIC KEY-----

私钥给后端用来解密：

-----BEGIN RSA PRIVATE KEY-----

MIIBPAIBAAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00OF66DkWizWoein2b7n/l

TUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQJBAJsMZ3zmV39xoxcekXrV

dDhfogw6fZY96WJZ8uqeGp5o+E8kIiwSvVPJJ/ktntSeGdz82BKip6CB7Pw28iuM

CiECIQDZESt+cflsbSLydOX8Ioo4PGDw7ftJT4YMlUHvIaOZDwIhAMEsm4v0CSm5

4sXODT546WrnrCECk7Yi1pAwqcSmIlyxAiAyvejE7i+4QOricqEwh4J4EuU2bOtI

/+X+GwYGuH5d0QIhAITnDMk4B4nWoweWIRSHGYh8hbdcT4Xy6A3h/RsXdfKxAiEA

luBD4h2dSlbNwjFyb3bRW+1Kc4PbMFOPCX6ip5PGFQ4=

-----END RSA PRIVATE KEY-----

页面端

先clone一份node-forge源码，安装完依赖，再生成bundle：

git clone https://github.com/digitalbazaar/forge && cd forge
npm install
npm run bundle

git clone https://github.com/digitalbazaar/forge && cd forge

npm install

npm run bundle

然后就能得到一个完整的forge包：js/forge.bundle.js，在页面中引用它：

<script src="js/forge.bundle.js"></script>
<script src="js/jquery.min.js"></script> //jQuery 假定你也是用的

1 2	<script src="js/forge.bundle.js"></script> <script src="js/jquery.min.js"></script> //jQuery 假定你也是用的

一如之前设计的，我们要山寨的TSL是基于RSA+AES的混合方案，纵然有node-forge这么老卵的包，也还是需要自己写点工具方法的：

//aes对称加密，返回: 密文/key/iv
function _encrypt_by_aes(message) {
        var key = forge.random.getBytesSync(32);
        var iv = forge.random.getBytesSync(32);
        var cipher = forge.cipher.createCipher('AES-CBC', key);
        cipher.start({iv: iv});
        cipher.update(forge.util.createBuffer(message));
        cipher.finish();
        var encrypted = cipher.output;
        return {encrypted: encrypted, key: key, iv: iv};
}
//rsa公钥加密，传入: 公钥PEM形式
function _encrypt_by_rsa(message, pubkey) {
        var pki = forge.pki;
        var publicKey = pki.publicKeyFromPem(pubkey);
        return publicKey.encrypt(message);
}
//序列化：把密文binary形式转成能够传输的hex形式
function _serialize(obj) {
        return forge.util.bytesToHex(obj);
}

//aes对称加密，返回: 密文/key/iv

function _encrypt_by_aes(message) {

var key = forge.random.getBytesSync(32);

var iv = forge.random.getBytesSync(32);

var cipher = forge.cipher.createCipher('AES-CBC', key);

cipher.start({iv: iv});

cipher.update(forge.util.createBuffer(message));

cipher.finish();

var encrypted = cipher.output;

return {encrypted: encrypted, key: key, iv: iv};

}

//rsa公钥加密，传入: 公钥PEM形式

function _encrypt_by_rsa(message, pubkey) {

var pki = forge.pki;

var publicKey = pki.publicKeyFromPem(pubkey);

return publicKey.encrypt(message);

}

//序列化：把密文binary形式转成能够传输的hex形式

function _serialize(obj) {

return forge.util.bytesToHex(obj);

}

页面与后端的传输逻辑也就相对容易实施了：

function _normalize(url, kvset) {
        var api_url = url + '?';
        for (var k in kvset) {
            api_url += k + '=' + kvset[k] + '&';
        }
        return api_url;
} 
function _transfer_wrapper(type) {
        return function(id, pubkey, url, cb_success, cb_err) {
            var _cipher = _encrypt_by_aes(id);
            var _cipher_id = _serialize(_cipher.encrypted);
            //后端对称解密id原文需要用到的的key和iv，被rsa加密后序列化传输:
            var _cipher_key = _serialize(_encrypt_by_rsa(_serialize(_cipher.key), pubkey));   
            var _cipher_iv = _serialize(_encrypt_by_rsa(_serialize(_cipher.iv), pubkey));

            var api_url = _normalize(access_url, {
                key: _cipher_key,
                iv: _cipher_iv,
                id: _cipher_id
            });

            $.ajax({type: type, url: api_url, data: {}})
                .done(cb_success)
                .fail(cb_err);
        };
}

$.fn.API_GET = _transfer_wrapper('GET');
$.fn.API_POST = _transfer_wrapper('POST');
$.fn.API_PUT = _transfer_wrapper('PUT');
$.fn.API_DELETE = _transfer_wrapper('DELETE');

function _normalize(url, kvset) {

var api_url = url + '?';

for (var k in kvset) {

api_url += k + '=' + kvset[k] + '&';

}

return api_url;

}

function _transfer_wrapper(type) {

return function(id, pubkey, url, cb_success, cb_err) {

var _cipher = _encrypt_by_aes(id);

var _cipher_id = _serialize(_cipher.encrypted);

//后端对称解密id原文需要用到的的key和iv，被rsa加密后序列化传输:

var _cipher_key = _serialize(_encrypt_by_rsa(_serialize(_cipher.key), pubkey));

var _cipher_iv = _serialize(_encrypt_by_rsa(_serialize(_cipher.iv), pubkey));

var api_url = _normalize(access_url, {

key: _cipher_key,

iv: _cipher_iv,

id: _cipher_id

});

$.ajax({type: type, url: api_url, data: {}})

.done(cb_success)

.fail(cb_err);

};

}

$.fn.API_GET = _transfer_wrapper('GET');

$.fn.API_POST = _transfer_wrapper('POST');

$.fn.API_PUT = _transfer_wrapper('PUT');

$.fn.API_DELETE = _transfer_wrapper('DELETE');

页面上如此调用：

var pubkey = `-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00
OF66DkWizWoein2b7n/lTUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQ==
-----END PUBLIC KEY-----`;
var id = 'b5a98f0a-73a2-403a-b6fe-a7cc712169a8'; //被加密的id
var url = 'http://example.org/api';

function success(data){
     console.log('SUCCESS', data);
}
function error(err){
     console.log('ERR', err);
}

$.fn.API_POST(id, pubkey, url, success, error);

var pubkey = `-----BEGIN PUBLIC KEY-----

MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00

OF66DkWizWoein2b7n/lTUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQ==

-----END PUBLIC KEY-----`;

var id = 'b5a98f0a-73a2-403a-b6fe-a7cc712169a8'; //被加密的id

var url = 'http://example.org/api';

function success(data){

console.log('SUCCESS', data);

}

function error(err){

console.log('ERR', err);

}

$.fn.API_POST(id, pubkey, url, success, error);

node.js 后端

后端一切从简，假定web框架用的express 4.x，依然需要先安装node-forge包：

npm install node-forge --save

1	npm install node-forge --save

纵然老卵，工具方法还是要自己写的：

var forge = require('node-forge');

function _decrypt_by_aes(encrypted, key, iv) {
    var decipher = forge.cipher.createDecipher('AES-CBC', key);
    decipher.start({iv: iv});
    decipher.update(encrypted);
    decipher.finish();
    return decipher.output;    
}
function _decrypt_by_rsa(encrypted, prvkey) {
    var pki = forge.pki;
    var privateKey = pki.privateKeyFromPem(prvkey);
    return privateKey.decrypt(encrypted);
}
function _deserialize(hex) {
    var buffer = forge.util.hexToBytes(hex);
    return forge.util.createBuffer(buffer, 'raw');
}

var private_key = `-----BEGIN RSA PRIVATE KEY-----
MIIBPAIBAAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00OF66DkWizWoein2b7n/l
TUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQJBAJsMZ3zmV39xoxcekXrV
dDhfogw6fZY96WJZ8uqeGp5o+E8kIiwSvVPJJ/ktntSeGdz82BKip6CB7Pw28iuM
CiECIQDZESt+cflsbSLydOX8Ioo4PGDw7ftJT4YMlUHvIaOZDwIhAMEsm4v0CSm5
4sXODT546WrnrCECk7Yi1pAwqcSmIlyxAiAyvejE7i+4QOricqEwh4J4EuU2bOtI
/+X+GwYGuH5d0QIhAITnDMk4B4nWoweWIRSHGYh8hbdcT4Xy6A3h/RsXdfKxAiEA
luBD4h2dSlbNwjFyb3bRW+1Kc4PbMFOPCX6ip5PGFQ4=
-----END RSA PRIVATE KEY-----`;

var forge = require('node-forge');

function _decrypt_by_aes(encrypted, key, iv) {

var decipher = forge.cipher.createDecipher('AES-CBC', key);

decipher.start({iv: iv});

decipher.update(encrypted);

decipher.finish();

return decipher.output;

}

function _decrypt_by_rsa(encrypted, prvkey) {

var pki = forge.pki;

var privateKey = pki.privateKeyFromPem(prvkey);

return privateKey.decrypt(encrypted);

}

function _deserialize(hex) {

var buffer = forge.util.hexToBytes(hex);

return forge.util.createBuffer(buffer, 'raw');

}

var private_key = `-----BEGIN RSA PRIVATE KEY-----

MIIBPAIBAAJBAKPLxKHePPC3OusMSYqPymDuuUpojM00OF66DkWizWoein2b7n/l

TUqwtiEkwY0ZZkDvktfjijpiDJMp4xscN18CAwEAAQJBAJsMZ3zmV39xoxcekXrV

dDhfogw6fZY96WJZ8uqeGp5o+E8kIiwSvVPJJ/ktntSeGdz82BKip6CB7Pw28iuM

CiECIQDZESt+cflsbSLydOX8Ioo4PGDw7ftJT4YMlUHvIaOZDwIhAMEsm4v0CSm5

4sXODT546WrnrCECk7Yi1pAwqcSmIlyxAiAyvejE7i+4QOricqEwh4J4EuU2bOtI

/+X+GwYGuH5d0QIhAITnDMk4B4nWoweWIRSHGYh8hbdcT4Xy6A3h/RsXdfKxAiEA

luBD4h2dSlbNwjFyb3bRW+1Kc4PbMFOPCX6ip5PGFQ4=

-----END RSA PRIVATE KEY-----`;

写个中间件，尝试解密请求并判定是否合法：

function _check_api_request(req, res, next) {
     //...blabla
     try { //出错必定为非法请求
          var key = _deserialize(req.query.key);
          var iv = _deserialize(req.query.iv);
          var cipher_id = _deserialize(req.query.id);
          var cipher_k = _deserialize(_decrypt_by_rsa(key.data, private_key));
          var cipher_v = _deserialize(_decrypt_by_rsa(iv.data, private_key));
          //注入id
          req.id = _decrypt_by_aes(cipher_id, cipher_k, cipher_v);
     } catch(err) { return res.sendStatus(401); }
     
     return next();
}

function _check_api_request(req, res, next) {

//...blabla

try { //出错必定为非法请求

var key = _deserialize(req.query.key);

var iv = _deserialize(req.query.iv);

var cipher_id = _deserialize(req.query.id);

var cipher_k = _deserialize(_decrypt_by_rsa(key.data, private_key));

var cipher_v = _deserialize(_decrypt_by_rsa(iv.data, private_key));

//注入id

req.id = _decrypt_by_aes(cipher_id, cipher_k, cipher_v);

} catch(err) { return res.sendStatus(401); }

return next();

}

小结

至此，关于Javascript的TSL实践告一段落，其实上面的例子可以做得更鲁棒一些，加上CheckSum也是好的选择，有时间的话，择日将再整理一版跨语言的加解密方案。

参考

Node.js加解密 http://www.jianshu.com/p/85f152944527
HTTPS/SSL原理及Ruby实现 http://foobar.me/2011/05/19/https-ssl-yuan-li-ji-ruby-shi-xian/

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Published

December 19, 2015

Mo Ye in JavaScript | December 19, 2015