尝试用 php 用 aes-256-gcm 解密答案

【问题标题】：Trying to decrypt with aes-256-gcm with php尝试用 php 用 aes-256-gcm 解密
【发布时间】：2019-02-27 20:12:48
【问题描述】：

我想知道是否有人可以提供帮助，

我使用的是aes-256-gcm加密方式，可以加密，但不能解密。

下面是我的代码，谁能看出我哪里出错了

$textToDecrypt = $_POST['message'];
$password = '3sc3RLrpd17';
$method = 'aes-256-gcm'; 
$tag_length = 16;
$password = substr(hash('sha256', $password, true), 0, 32);
$iv = chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0);
$decrypted = openssl_decrypt(base64_decode($textToDecrypt), $method, 
$password, OPENSSL_RAW_DATA, $iv, $tag_length);

加密代码

$textToEncrypt = $_POST['message'];
$password = '3sc3RLrpd17';
$method = 'aes-256-gcm'; 
$tag_length = 16;


$password = substr(hash('sha256', $password, true), 0, 32);



$iv = chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . 
chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . 
chr(0x0) . chr(0x0) . chr(0x0);


$encrypted = base64_encode(openssl_encrypt($textToEncrypt, $method, 
$password, OPENSSL_RAW_DATA, $iv, $tag_length));

【问题讨论】：

标签： php encryption aes-gcm

【解决方案1】：

您需要将 GCM tag (HMAC) 与密文一起保存，并将其传递给解密函数。它不会自动为您保存（您还应该生成一个好的 IV 并将其与密文一起存储）。

openssl_encrypt 指定为：

string openssl_encrypt ( string $data , string $method , string $key [, int $options = 0 [, string $iv = "" [, string &$tag = NULL [, string $aad = "" [, int $tag_length = 16 ]]]]] )

如果你仔细观察，你会传入$tag_length，这里应该是$tag。

它应该是这样的：

加密：

$textToEncrypt = $_POST['message'];
$password = '3sc3RLrpd17';
$key = substr(hash('sha256', $password, true), 0, 32);
$cipher = 'aes-256-gcm';
$iv_len = openssl_cipher_iv_length($cipher);
$tag_length = 16;
$iv = openssl_random_pseudo_bytes($iv_len);
$tag = ""; // will be filled by openssl_encrypt

$ciphertext = openssl_encrypt($textToEncrypt, $cipher, $key, OPENSSL_RAW_DATA, $iv, $tag, "", $tag_length);
$encrypted = base64_encode($iv.$ciphertext.$tag);

解密：

$textToDecrypt = $_POST['message'];
$encrypted = base64_decode($textToDecrypt);
$password = '3sc3RLrpd17';
$key = substr(hash('sha256', $password, true), 0, 32);
$cipher = 'aes-256-gcm';
$iv_len = openssl_cipher_iv_length($cipher);
$tag_length = 16;
$iv = substr($encrypted, 0, $iv_len);
$ciphertext = substr($encrypted, $iv_len, -$tag_length);
$tag = substr($encrypted, -$tag_length);

$decrypted = openssl_decrypt($ciphertext, $cipher, $key, OPENSSL_RAW_DATA, $iv, $tag);

【讨论】：

感谢您的解密，最后一行出现错误“警告：openssl_decrypt()：AEAD 模式的 IV 长度设置失败”，我该如何纠正？
这意味着你的$_POST['message'] 是空的。检查您是否确实获得了 $textToDecrypt 中的数据

【解决方案2】：

@Scribilicious 这里的问题是 $iv 和 $tag 是二进制的（$encrypted 是 base64）。所以数据中可能有一个'::'。所以这可能会更好。

function encrypt($key, $data) {
    $encryptionKey = base64_decode($key);
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-gcm'));
    $encrypted = openssl_encrypt($data, 'aes-256-gcm', $encryptionKey, 0, $iv, $tag);
    return $encrypted . ':' . base64_encode($iv) . ':' . base64_encode($tag));
}

function decrypt($key, $data) {
    $encryptionKey = base64_decode($key);
    list($encryptedData, $iv, $tag) = explode(':', $data, 3);
    return openssl_decrypt($encryptedData, 'aes-256-gcm', $encryptionKey, 0, base64_decode($iv), base64_decode($tag));
}

$encrypt = encrypt('key', 'test data');
$decrypt = decrypt('key', $encrypt);

echo $encrypt . ' : ' . $decrypt;

【讨论】：

【解决方案3】：

怎么样？

function encrypt($key, $data) {
    $encryptionKey = base64_decode($key);
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-gcm'));
    $encrypted = openssl_encrypt($data, 'aes-256-gcm', $encryptionKey, 0, $iv, $tag);
    return base64_encode($encrypted . '::' . $iv . '::' . $tag);
}


function decrypt($key, $data) {
    $encryptionKey = base64_decode($key);
    list($encryptedData, $iv, $tag) = explode('::', base64_decode($data), 3);
    return openssl_decrypt($encryptedData, 'aes-256-gcm', $encryptionKey, 0, $iv, $tag);
}

$encrypt = encrypt('key', 'test data');
$decrypt = decrypt('key', $encrypt);

echo $encrypt . ' : ' . $decrypt;

【讨论】：