thinkphp微信开发：安全模式消息加解密，thinkphp解密

使用thinkphp官方的WeChat包，使用不同模式可以成功，但是安全模式就是不行，现将分析解决结果做下记录。

TRight

分析问题：

解密微信服务器消息老是不成功，下载下微信公众平台官方给出的解密文件和WechatCrypt.class.php进行比对发现也没有问题。用file_put_contents函数保存下解密后的文件进行分析。发现官方包解密的xml不是标准的xml格式，所以simplexml_load_string函数无法处理。

<span>/*</span><span>*
     * 对密文进行解密
     * @param  string $encrypt 密文
     * @return string          明文
     </span><span>*/</span>
    <span>public</span> <span>function</span> decrypt(<span>$encrypt</span><span>){
        </span><span>//</span><span>BASE64解码</span>
        <span>$encrypt</span> = <span>base64_decode</span>(<span>$encrypt</span><span>);

        </span><span>//</span><span>打开加密算法模块</span>
        <span>$td</span> = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, ''<span>);

        </span><span>//</span><span>初始化加密算法模块</span>
        mcrypt_generic_init(<span>$td</span>, <span>$this</span>->cyptKey, <span>substr</span>(<span>$this</span>->cyptKey, 0, 16<span>));

        </span><span>//</span><span>执行解密</span>
        <span>$decrypt</span> = mdecrypt_generic(<span>$td</span>, <span>$encrypt</span><span>);
       
        </span><span>//</span><span>去除PKCS7补位</span>
        <span>$decrypt</span> = self::PKCS7Decode(<span>$decrypt</span>, mcrypt_enc_get_key_size(<span>$td</span><span>));

        </span><span>//</span><span>关闭加密算法模块</span>
        mcrypt_generic_deinit(<span>$td</span><span>);
        mcrypt_module_close(</span><span>$td</span><span>);

        </span><span>if</span>(<span>strlen</span>(<span>$decrypt</span>) < 16<span>){
            </span><span>throw</span> <span>new</span> \<span>Exception</span>("非法密文字符串！"<span>);
        }

        </span><span>//</span><span>去除随机字符串</span>
        <span>$decrypt</span> = <span>substr</span>(<span>$decrypt</span>, 16<span>);

        </span><span>//</span><span>获取网络字节序</span>
        <span>$size</span> = <span>unpack</span>("N", <span>substr</span>(<span>$decrypt</span>, 0, 4<span>));
        </span><span>$size</span> = <span>$size</span>[1<span>];

        </span><span>//</span><span>APP_ID</span>
        <span>$appid</span> = <span>substr</span>(<span>$decrypt</span>, <span>$size</span> + 4<span>);

        </span><span>//</span><span>验证APP_ID</span>
        <span>if</span>(<span>$appid</span> !== <span>$this</span>-><span>appId){
            </span><span>throw</span> <span>new</span> \<span>Exception</span>("非法APP_ID！"<span>);
        }
        
        </span><span>//</span><span>明文内容</span>
        <span>$text</span> = <span>substr</span>(<span>$decrypt</span>, 4, <span>$size</span><span>);
        </span><span>return</span> <span>$text</span><span>;
    }

    </span><span>/*</span><span>*
     * PKCS7填充字符
     * @param string  $text 被填充字符
     * @param integer $size Block长度
     </span><span>*/</span>
    <span>private</span> <span>static</span> <span>function</span> PKCS7Encode(<span>$text</span>, <span>$size</span><span>){
        </span><span>//</span><span>字符串长度</span>
        <span>$str_size</span> = <span>strlen</span>(<span>$text</span><span>);

        </span><span>//</span><span>填充长度</span>
        <span>$pad_size</span> = <span>$size</span> - (<span>$str_size</span> % <span>$size</span><span>);
        </span><span>$pad_size</span> = <span>$pad_size</span> ? : <span>$size</span><span>;
        
        </span><span>//</span><span>填充的字符</span>
        <span>$pad_chr</span> = <span>chr</span>(<span>$pad_size</span><span>);

        </span><span>//</span><span>执行填充</span>
        <span>$text</span> = <span>str_pad</span>(<span>$text</span>, <span>$str_size</span> + <span>$pad_size</span>, <span>$pad_chr</span>,<span> STR_PAD_RIGHT);

        </span><span>return</span> <span>$text</span><span>;
    }

    </span><span>/*</span><span>*
     * 删除PKCS7填充的字符
     * @param string  $text 已填充的字符
     * @param integer $size Block长度
     </span><span>*/</span>
    <span>private</span> <span>static</span> <span>function</span> PKCS7Decode(<span>$text</span>, <span>$size</span><span>){
        </span><span>//</span><span>获取补位字符</span>
        <span>$pad_str</span> = <span>ord</span>(<span>substr</span>(<span>$text</span>, -1<span>));

        </span><span>if</span> (<span>$pad_str</span> < 1 || <span>$pad_str</span> > <span>$size</span><span>) {
            </span><span>$pad_str</span>= 0<span>;
        } 
            </span><span>return</span> <span>substr</span>(<span>$text</span>, 0, <span>strlen</span>(<span>$text</span>) - <span>$pad_str</span><span>);
        
    }</span>

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解决方法：

输出的xml文件是这样的

<span>1</span> <span><</span><span>xml</span><span>></span>
<span>2</span> <span><</span><span>ToUserName</span><span>></span><span><![CDATA[</span><span>gh_249aeb986d99</span><span>]]></span><span><</span><span>\/ToUserName</span><span>></span><span>\n
</span><span>3</span> <span><</span><span>FromUserName</span><span>></span><span><![CDATA[</span><span>oopVmxHZaeQkDPsRcbpwXKkH-J2Q</span><span>]]></span><span><</span><span>\/FromUserName</span><span>></span><span>\n
</span><span>4</span> <span><</span><span>CreateTime</span><span>></span>1448944621<span><</span><span>\/CreateTime</span><span>></span><span>\n
</span><span>5</span> <span><</span><span>MsgType</span><span>></span><span><![CDATA[</span><span>text</span><span>]]></span><span><</span><span>\/MsgType</span><span>></span><span>\n
</span><span>6</span> <span><</span><span>Content</span><span>></span><span><![CDATA[</span><span>\u7ecf\u7406</span><span>]]></span><span><</span><span>\/Content</span><span>></span><span>\n
</span><span>7</span> <span><</span><span>MsgId</span><span>></span>6223169761311044588<span><</span><span>\/MsgId</span><span>></span><span>\n
</span><span>8</span> <span><</span><span>\/xml</span><span>></span>

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所以需要进行处理才能让simplexml_load_string处理

在输出的明文内容后面加上

<span>1</span> <span>//明文内容
</span><span>2</span> <span>        $text = substr($decrypt, 4, $size);
</span><span>3</span> <span>//去掉多余的内容
</span><span>4</span>         $text=str_replace('<span><</span><span>\/','</', $text</span><span>);      
</span><span>5</span> <span>        $text</span><span>=str_replace('>\n','>', </span><span>$text);
</span><span>6</span> <span>        return $text;</span>

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安全模式就能正常使用了。