lua 与 php 通过AES数据加密进行通讯

近期公司有款《围住神经猫》的微信小游戏火爆的不行！公司又决定开发一系列的神经猫的小游戏，于是，我被拉过来了。

后来使用cocos-2dx 开发一款小游戏，client用的是lua脚本，为了server与client交互的安全性，我们决定对API接口

传输的JSON数据进行加密、解密。普通情况就是client加密，server段进行解密：

luaclient使用的是一个纯lua写的库：aeslua，下载地址：http://luaforge.net/projects/aeslua/

可是该库是有问题的：用该库加密解密是没有问题的，可是跟PHP通讯就存在问题了，由于该库加密后base64之后的

字符串PHP是无法解密的！为了这个问题，我查阅了好多资料，最终找到某个国外大神的解决的方法：

http://chainans.blogspot.com/2012/09/working-with-lua-encryption.html（可能有些同学无法FQ，故把原文贴出来例如以下：）

Working with Lua encryption

Recently working with Corona SDK, I start to need some standard encryption/decryption algorithm in Lua. To start with, actually, it has rather small number of developers comparing to the Objective-C which I have been working with. Meaning that there are fewer 3rd party librarys you can rely upon. Luckily, I found one called AESLua which has some code to start. From there, my objective is to make a way to securely passing data between my client and server. (php on server-side) In fact, from what I'd read, my method is not very secure but it is better than nothing. Just for my reference, here are the list of issues along the way

Edited: Tested with iPhone 4... Input cipher text of 1280 characters. Take around 25 seconds. Unacceptable speed for general uses.

1) It requires Lua 5.2 feature which does not seem to be in Corona

Solution: Download LuaBit v0.4 and integrate it... You will need to make a mapping to allow API call to the proper place

2) Next you need to get Base64 library -- grab it here https://gist.github.com/2563975 -- It initially made to allow passing it over the URL (using '-' and '_' instead of '+' and '/') So, I change them to the latter one.

3) For AESLua, by default, it uses AES-128, CBC, some kind of random padding <- I don't know its name, IV = 0. I will change it into is AES-128, CBC, PKCS7 padding. Here are the website to test if our conversion is ok or not

http://www.unsw.adfa.edu.au/~lpb/src/AEScalc/AEScalc.html

http://www.tools4noobs.com/online_tools/decrypt/

Here are the things to do

3.1) In pwInKey function, comment the line out

 password = ciphermode.encryptString(pwBytes, password, ciphermode.encryptCBC);

3.2) In util.padByteString function, change it to

    local paddingLength = math.ceil(#data/16)*16 - #data;

    local padding = "";

    local paddingValue = string.char ( paddingLength )  -- PKCS7 padding

    for i=1,paddingLength do

padding = padding .. paddingValue; -- PKCS7 padding

    end 

    return data .. padding;

4) Set up web server for testing, you will need php / mcrypt mod to test.

5) Creating a php for testing... here is a code

Now, my plain text below is "1234567890123456ss@#%de".

<?php

$data = 'dXzNDNxckOrb7uz2ON0AAJp4BXgkYewblTNWBSAQSEw=';

$key128 = '1234567890123456';

$iv =  '';

echo mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key128, base64_decode($data), MCRYPT_MODE_CBC, $iv)

?>

That's it. The encryption backward to client machine should be a piece of cake. =)

*** By using these library, the user should be aware of the fact that Lua's performance is still far from native code. You may not want to use this algorithm to encrypt a large volume of data.

依照他的办法，一切都OK了。可是有下面几点须要说明下面：（本人摸索的）

1.利用CBC模式加密的字符串的key必须是16位，否则PHP无法解密！

2.明文字符串的必须把key作为前缀加进去

3.上面文章中没有把unpack函数写出来，本人查阅了一些资料，补充了，否则aeslua无法正常解密了！

util.lua中的以下这个函数改为例如以下：

function public.unpadByteString(data)
    local padLength = tonum((string.byte(data, #data)));
    return string.sub(data,1, #data-padLength)   --unpack
end