一些使用trim（）的字符串的PHP解密失败 [英] PHP decryption fails on some strings with trim()'s

问题描述

我无法解密以％3D％3D结尾的值。解密后，我会收到一个完全无法辨认的返回值。加密的值正在通过querystring传递，但是我已经运行了一个测试循环，通过值0到200来排除url编码的问题。

I'm having trouble decrypting values that end with %3D%3D. Upon decrypting I get a return value that's completely illegible. The encrypted value is being passed via the querystring, but I've run a test looping through values 0 to 200 to rule out problems with url encoding.

加密和解密功能：

Encryption and decryption functions:

function encryptValue($encrypt) {
    $key = variable_get_local("privateKey", $default = "");
    $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB),   MCRYPT_RAND);
    $passcrypt = trim(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, trim($encrypt), MCRYPT_MODE_ECB, $iv));
    $encode = urlencode(base64_encode($passcrypt));
    return $encode;
}


function decryptValue($decrypt) {
    $key = variable_get_local("privateKey", $default = "");
    $decoded = base64_decode(urldecode($decrypt));
    $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND);
    $decrypted = trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, trim($decoded), MCRYPT_MODE_ECB, $iv));
    return $decrypted;
}

我已经尝试保持iv值在加密和解密之间相同，但这不不改变输出。我也尝试删除 trim（$ decoding）之间的 trim（），但是没有更改任何。

I've tried keeping the iv value identical across encryption and decryption but this doesn't change the output. I've also tried removing the trim() around trim($decoded) but that didn't change anything either.

以下是我用来识别问题的方法。在0到200之间，加密将产生以％3D％3D结尾的值9次，并导致解密失败。

Below is what I used to identify the problem. Between 0 and 200 the encryption will produce a value ending on %3D%3D 9 times and result in the decryption failing.

for($i=0;$i<200;$i++) {
    echo encryptValue($i) . "<br/>";
    echo decryptValue(encryptValue($i)) . "<br/><hr/>";
}

感谢阅读。

推荐答案

您的问题是所有的 trim 函数，不应该使用。您不会修剪编码的数据，因为数据将被删除，可能对您关注的关键是您注意到的。

Your problem is with all the trim function, that shouldnt be used. You dont trim encoded data as data will be removed, could be vital to the key as you have noticed.

它的工作原理如下：

function encryptValue($encrypt) {
    $key = variable_get_local("privateKey", $default = "");
    $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB),   MCRYPT_RAND);
    $passcrypt = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, trim($encrypt), MCRYPT_MODE_ECB, $iv);
    $encode = urlencode(base64_encode($passcrypt));
    return $encode;
}


function decryptValue($decrypt) {
    $key = variable_get_local("privateKey", $default = "");
    $decoded = base64_decode(urldecode($decrypt));
    $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND);
    $decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $decoded, MCRYPT_MODE_ECB, $iv);
    return $decrypted;
}

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