php AES256加密兼容性在目标c [英] php AES256 encryption compatibility in objective-c

问题描述

我已经在php（作为服务）中编写了一个代码来解密通过协议发送的密码。协议要求密码为Mac然后加密（MtE），使用AES256，然后使用base-64编码。

消息结构如这个在php.net上的评论。

  base46encoded（iv + ecrypted（mac + password））
  

该过程很容易使用php

  public static function getPassword（$ password，$ key，$ mac_algorithm ='sha1'，
 $ enc_algorithm = MCRYPT_RIJNDAEL_256，$ enc_mode = MCRYPT_MODE_CBC）
 {
 //将预共享密钥截断为32字节。 
 $ key = substr（$ key，0，32）; 
 
 //从base64 
 $ password = base64_decode（$ password）解码消息（作为密码）; 
 
 //根据算法和加密模式获取iv大小
 $ iv_size = mcrypt_get_iv_size（$ enc_algorithm，$ enc_mode）; 
 
 //从消息头（通常是前32个字节）中提取iv用于解密
 $ iv_dec = substr（$ password，0，$ iv_size）; 
 
 //在头文件（前32个字节之后）获取加密的消息
 $ password = substr（$ password，$ iv_size）; 
 
 //使用预共享密钥解密消息并提取iv 
 $ password = mcrypt_decrypt（$ enc_algorithm，$ key，$ password，$ enc_mode，$ iv_dec）; 
 
 //获取哈希算法的块大小（sha1块大小为160位）
 $ mac_block_size = ceil（static :: getMacAlgoBlockSize（$ mac_algorithm）/ 8）; 
 
 //从解密消息的头中提取mac 
 $ mac_dec = substr（$ password，0，$ mac_block_size）; 
 
 //提取有价值的消息
 $ password = substr（$ password，$ mac_block_size）; 
 
 //消除额外的空终止符，作为enc /解密的结果填充以下if和下一条语句是unpack函数的check子句
 $ password = unpack（'Z *'，$密码）; 
 if（！isset（$ password [1]））
 {
 return false; 
} 
 
 //从解压缩结果获取纯预期消息（作为密码）
 $ password = $ password [1]; 
 
 //重新生成mac来控制传输的真实性和正确性
 $ mac = hash_hmac（$ mac_algorithm，$ password，$ key，true）; 
 
 //看是否传输的mac（mac_dec）和生成的mac是相同的，数据是有效的
如果（$ mac_dec == $ mac）
 {
返回$密码; 
} 
 else 
 {
 return false; 
} 
} 
  

现在的问题是，应用程序是围绕着这个开发的我们使用了标准的CCHmac，Base64EncodedStringWithOptions：NSDataBase64EncodingEndLineWithCarriageReturn和 CCCrypt的此SO答案。

解决方案

mcrypt_generic_init函数通过指定密钥和IV来初始化密码。密钥的长度决定了我们是否正在进行128位，192位或256位加密。

所以使用MCRYPT_RIJNDAEL_128与256位（32 -byte）键与AES256兼容。

I've written a code in php (as a service) to decrypt passwords sent over a protocol. The protocol demands the password to be "Mac then Encrypt"ed (MtE) using AES256, then encoded using base-64.

The message structure is as described in this comment on php.net.

base46encoded (iv + ecrypted(mac + password))

The process was easy using php

public static function getPassword($password, $key, $mac_algorithm = 'sha1',
                                       $enc_algorithm = MCRYPT_RIJNDAEL_256, $enc_mode = MCRYPT_MODE_CBC)
    {
        // truncating pre-shared key to 32 bytes.
        $key = substr($key, 0, 32);

        // decoding the message (being a password) from base64
        $password = base64_decode($password);

        // getting the iv size based on algorithm and encryption mode
        $iv_size = mcrypt_get_iv_size($enc_algorithm, $enc_mode);

        // extracting iv from message header (normally the first 32 byte) for decryption
        $iv_dec = substr($password, 0, $iv_size);

        // getting the encrypted message after the header (after the first 32 byte)
        $password = substr($password, $iv_size);

        // decrypting message using the pre-shared key and extracted iv
        $password = mcrypt_decrypt($enc_algorithm, $key, $password, $enc_mode, $iv_dec);

        // getting block size for hash algorithm in bytes (sha1 block size is 160 bit)
        $mac_block_size = ceil(static::getMacAlgoBlockSize($mac_algorithm)/8);

        // extracting the mac from the header of decrypted message
        $mac_dec = substr($password, 0, $mac_block_size);

        // extracting the valuable message
        $password = substr($password, $mac_block_size);

        // eliminate extra null terminators padded as the result of enc/decryption the following if and the next statement are check clauses for unpack function
        $password = unpack('Z*', $password);
        if (!isset($password[1]))
        {
            return false;
        }

        // obtaining the pure intended message (being the password) from the unpack result
        $password = $password[1];

        // regenerating the mac to control the authenticity and correctness of transmission
        $mac = hash_hmac($mac_algorithm, $password, $key, true);

        // see if transmitted mac (mac_dec) and the generated mac are the same and the data is valid
        if($mac_dec == $mac)
        {
            return $password;
        }
        else
        {
            return false;
        }
    }

Now the problem is, the application is developed around this protocol in iOS, and tried AESCrypt and CCCrypt, but the decryption results are different (gibberish).

We used standard CCHmac, Base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithCarriageReturn and This SO answer for CCCrypt.

解决方案

The mcrypt_generic_init function initializes the cipher by specifying both the key and the IV. The length of the key determines whether we're doing 128-bit, 192-bit, or 256-bit encryption.

So use MCRYPT_RIJNDAEL_128 with a 256-bit (32-byte) key to be compatible with AES256.

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