.NET Core 加密填充无效且无法删除

Question

我正在尝试在 ASP.NET Core Web API 项目中使用加密/解密。我发现这篇文章展示了加密和解密的工作示例：

https://mikaelkoskinen.net/post/encrypt-decrypt-string-asp-net-core

复制并运行，它有效，非常棒——到目前为止。

然后我更改了要加密/解密的字符串，如果因填充问题而失败，则不允许。

EncryptString

和

DecryptString

方法逐字记录到网站源代码。

// THIS IS ORIGINAL and works (without Console.WriteLine)
var content = "Example test";
var key = "E546C8DF278CD5931069B522E695D4F2";
var encrypted = EncryptString(content, key);
var decrypted = DecryptString(encrypted, key);

// Then I changed to encrypt a simple string and fails
content = "testing16charsX1";
encrypted = EncryptString(content, key);
decrypted = DecryptString(encrypted, key);

将函数的原始代码保留在此处的单一源位置。

public static string EncryptString(string text, string keyString)
{
    var key = Encoding.UTF8.GetBytes(keyString);

    using (var aesAlg = Aes.Create())
    {
        using (var encryptor = aesAlg.CreateEncryptor(key, aesAlg.IV))
        {
            using (var msEncrypt = new MemoryStream())
            {
                using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                using (var swEncrypt = new StreamWriter(csEncrypt))
                {
                    swEncrypt.Write(text);
                }

                var iv = aesAlg.IV;

                var decryptedContent = msEncrypt.ToArray();

                var result = new byte[iv.Length + decryptedContent.Length];

                Buffer.BlockCopy(iv, 0, result, 0, iv.Length);
                Buffer.BlockCopy(decryptedContent, 0, result, iv.Length, decryptedContent.Length);

                return Convert.ToBase64String(result);
            }
        }
    }
}

public static string DecryptString(string cipherText, string keyString)
{
    var fullCipher = Convert.FromBase64String(cipherText);

    var iv = new byte[16];
    var cipher = new byte[16];

    Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
    Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, iv.Length);

    var key = Encoding.UTF8.GetBytes(keyString);

    using (var aesAlg = Aes.Create())
    {
        using (var decryptor = aesAlg.CreateDecryptor(key, iv))
        {
            string result;

            using (var msDecrypt = new MemoryStream(cipher))
            {
                using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                     using (var srDecrypt = new StreamReader(csDecrypt))
                     {
                         result = srDecrypt.ReadToEnd();
                     }
                }
            }

            return result;
        }
    }
}

感谢帮助。此外，想要强制加密/解密为 AES256，这里没有关于 KeySize 设置为 256 的内容，但想要在不破坏的情况下进行测试，但似乎也被破坏了？

Answer 1

错误就在这里。在

EncryptString

方法中，它依次复制IV和加密内容：

var result = new byte[iv.Length + decryptedContent.Length];
Buffer.BlockCopy(iv, 0, result, 0, iv.Length);
Buffer.BlockCopy(decryptedContent, 0, result, iv.Length, decryptedContent.Length);

但是在

DecryptString

方法中，它只复制了16字节的加密内容：

var iv = new byte[16];
var cipher = new byte[16];
Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, iv.Length);

它应该复制所有剩余的内容：

var cipher = new byte[fullCipher.Length - iv.Length];
Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, cipher.Length);

AES默认的填充模式是pkcs7，如果你的输入数据长度正好是BlockSize，则会追加一个额外的块。如果您想强制加密内容长度为16，则需要将填充模式更改为None并手动填充输入数据。