HTTP Request encrypt & decrypt failure with PHP & Objective-C

问题

I have an issue with HTTP POST requests encrypting & decrypting.

I have an OS X Application written in Objective-C which sends encrypted (CocoaSecurity) HTTP POST request to server:

- (NSString *)secure
{
    NSData* key = [@"9eab87dc72b927c9" dataUsingEncoding:NSASCIIStringEncoding];
    NSData* iv = [@"d6f8f85911c4d8d1" dataUsingEncoding:NSASCIIStringEncoding];

    CocoaSecurityResult *result = [CocoaSecurity aesEncrypt:@"a" key:key iv:iv];

    return result.hexLower;    
}

and I am getting encryption

5219abd6c1439dc832ab512dae8cce80

Also I have a WEB Application written in PHP which decrypts sent request

protected function processEncrypt()
{
    if ($this->input) {
        $crypt = mcrypt_module_open($this->algorithm, '', $this->mode, $this->encryptIv);
        mcrypt_generic_init($crypt, $this->encryptKey, $this->encryptIv);
        $this->input = mcrypt_generic($crypt, $this->input);
        mcrypt_generic_deinit($crypt);
        mcrypt_module_close($crypt);

        if ($this->template == 'hex') {
            $this->input = bin2hex($this->input);
        } elseif ($this->template == 'base64') {
            $this->input = base64_encode($this->input);
        }
    }
}

The encrypted message, at the end of request handling, is totally different from the decrypted one.

I am getting encryption

10967675e5cf70878ee063a73f2a8394

Until now I have found out, that this might be a PKCS#7 padding issue (PHP mcrypt library has null padding). I have tried to remove padding by changing CocoaSecurity.m source and replacing kCCOptionPKCS7Padding value to 0. After this replacement, CocoaSecurity raises exception Encrypt Error!triggered by kCCAlignmentError...

Could anyone tell me, where is the problem?

回答1:

Note that CocoaSecurity uses standard PKCS#7 padding (kCCOptionPKCS7Padding) but mcrypt uses non-standard/insecure null padding. You will need to remove the PKCS#7 padding in your php code. You can use the this code:

Add PKCS#7 padding (php):

 $pad = $block - (strlen($str) % $block);
 $str .= str_repeat(chr($pad), $pad);

Remove PKCS#7 padding (php):

$len = strlen($str);
$pad = ord($str[$len-1]);
$str = $strsubstr($str, 0, $len - $pad);

See this SO answer for detailed information.

来源：https://stackoverflow.com/questions/32138354/http-request-encrypt-decrypt-failure-with-php-objective-c

标签

php

objective-c

encryption

cryptography

aes