可以在 C#/dotNet 5 中解密由 openssl enc -k 加密的 AES 密码保护文件吗？

Question

我需要解密来自 linux 盒子的文件，密码受 Openssl 和 AES 保护。加密完成

openssl enc -aes-256-cbc -k <pwd>

目前，我在 Windows 上使用以下脚本正确解密：

"openssl.exe" enc -d -aes-256-cbc -k <pwd> -in <inputFile> -out <output>

到目前为止，我在我的项目中包含了 openssl exe 和 2 dll。

但是，我想摆脱那些依赖关系并直接在 C# 中对其进行解码。

上面 openssl enc -d 的 C# 等价物是什么？

反正可以吗？我从 https://security.stackexchange.com/questions/20628/where-is-the-salt-on-the-openssl-aes-encryption 了解到 openssl enc 是一种非标准的，并且使用给定密码中的随机盐。

受其他一些类似主题的启发，我目前的方法总是遇到“填充无效”问题，例如这个问题 AES-256-CBC Decrypt Error Stating Padding is invalid and cannot be removed

这个有 10 年历史的帖子 OpenSSL encryption using .NET classes 提出了一个解决方案，检索盐和 IV 更加复杂，但这不再有效。我也遇到了“填充无效”的问题。

（删除了密码的 Rfc2898DeriveBytes 对象的原始代码，openssl 不使用这个 Rfc2898DeriveBytes 东西）。请参阅已接受答案中的工作代码。

Answer 1

来自 10 year old question you linked 的代码实际上在稍作修改后仍然有效。首先请注意，默认情况下 OpenSSL 现在使用 SHA256 作为哈希函数而不是 MD5，我们可以轻松解决这个问题。然后，该答案假设您为 openssl 提供“-base64”选项，并以 base64 格式获得结果，而不是 OpenSSL 默认使用的奇怪格式，但这也很容易修复。只需将目标文件读取为字节，然后从开头剥离 ascii 编码的“SALTED__”字符串：

var input = File.ReadAllBytes(@"your encrypted file");
input = input.Skip(Encoding.ASCII.GetBytes("SALTED__").Length).ToArray();

现在调整它从那里提取盐分和加密数据的方式，并使用 PKCS7 填充，它就会起作用。从上面的答案复制的完整代码以及提到的修复：

public class Protection
{
    public string OpenSSLDecrypt(byte[] encryptedBytesWithSalt, string passphrase)
    {
        // extract salt (first 8 bytes of encrypted)
        byte[] salt = new byte[8];
        byte[] encryptedBytes = new byte[encryptedBytesWithSalt.Length - salt.Length];
        Buffer.BlockCopy(encryptedBytesWithSalt, 0, salt, 0, salt.Length);
        Buffer.BlockCopy(encryptedBytesWithSalt, salt.Length, encryptedBytes, 0, encryptedBytes.Length);
        // get key and iv
        byte[] key, iv;
        DeriveKeyAndIV(passphrase, salt, out key, out iv);
        return DecryptStringFromBytesAes(encryptedBytes, key, iv);
    }

    private static void DeriveKeyAndIV(string passphrase, byte[] salt, out byte[] key, out byte[] iv)
    {
        // generate key and iv
        List<byte> concatenatedHashes = new List<byte>(48);

        byte[] password = Encoding.UTF8.GetBytes(passphrase);
        byte[] currentHash = new byte[0];
        var md5 = SHA256.Create();
        bool enoughBytesForKey = false;
        // See http://www.openssl.org/docs/crypto/EVP_BytesToKey.html#KEY_DERIVATION_ALGORITHM
        while (!enoughBytesForKey)
        {
            int preHashLength = currentHash.Length + password.Length + salt.Length;
            byte[] preHash = new byte[preHashLength];

            Buffer.BlockCopy(currentHash, 0, preHash, 0, currentHash.Length);
            Buffer.BlockCopy(password, 0, preHash, currentHash.Length, password.Length);
            Buffer.BlockCopy(salt, 0, preHash, currentHash.Length + password.Length, salt.Length);

            currentHash = md5.ComputeHash(preHash);
            concatenatedHashes.AddRange(currentHash);

            if (concatenatedHashes.Count >= 48)
                enoughBytesForKey = true;
        }

        key = new byte[32];
        iv = new byte[16];
        concatenatedHashes.CopyTo(0, key, 0, 32);
        concatenatedHashes.CopyTo(32, iv, 0, 16);

        md5.Clear();
        md5 = null;
    }
    static string DecryptStringFromBytesAes(byte[] cipherText, byte[] key, byte[] iv)
    {
        // Check arguments.
        if (cipherText == null || cipherText.Length <= 0)
            throw new ArgumentNullException("cipherText");
        if (key == null || key.Length <= 0)
            throw new ArgumentNullException("key");
        if (iv == null || iv.Length <= 0)
            throw new ArgumentNullException("iv");

        // Declare the RijndaelManaged object
        // used to decrypt the data.
        RijndaelManaged aesAlg = null;

        // Declare the string used to hold
        // the decrypted text.
        string plaintext;

        try
        {
            // Create a RijndaelManaged object
            // with the specified key and IV.
            aesAlg = new RijndaelManaged {Mode = CipherMode.CBC, KeySize = 256, BlockSize = 128, Key = key, IV = iv, Padding = PaddingMode.PKCS7};

            // Create a decrytor to perform the stream transform.
            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
            // Create the streams used for decryption.
            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {
                        // Read the decrypted bytes from the decrypting stream
                        // and place them in a string.
                        plaintext = srDecrypt.ReadToEnd();
                        srDecrypt.Close();
                    }
                }
            }
        }
        finally
        {
            // Clear the RijndaelManaged object.
            if (aesAlg != null)
                aesAlg.Clear();
        }

        return plaintext;
    }
}

然后：

var input = File.ReadAllBytes(@"path to your encrypted file");
input = input.Skip(Encoding.ASCII.GetBytes("SALTED__").Length).ToArray();
var decrypted= new Protection().OpenSSLDecrypt(input, "123123");

如果解密非字符串数据，将DecryptStringFromBytesAes改成这样：

static byte[] DecryptStringFromBytesAes(byte[] cipherText, byte[] key, byte[] iv) {
    // Check arguments.
    if (cipherText == null || cipherText.Length <= 0)
        throw new ArgumentNullException("cipherText");
    if (key == null || key.Length <= 0)
        throw new ArgumentNullException("key");
    if (iv == null || iv.Length <= 0)
        throw new ArgumentNullException("iv");

    // Declare the RijndaelManaged object
    // used to decrypt the data.
    RijndaelManaged aesAlg = null;

    try {
        // Create a RijndaelManaged object
        // with the specified key and IV.
        aesAlg = new RijndaelManaged { Mode = CipherMode.CBC, KeySize = 256, BlockSize = 128, Key = key, IV = iv, Padding = PaddingMode.PKCS7 };

        // Create a decrytor to perform the stream transform.
        ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
        // Create the streams used for decryption.
        using (MemoryStream msDecrypt = new MemoryStream(cipherText)) {
            using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read)) {
                using (var output = new MemoryStream()) {
                    csDecrypt.CopyTo(output);
                    return output.ToArray();
                }
            }
        }
    }
    finally {
        // Clear the RijndaelManaged object.
        if (aesAlg != null)
            aesAlg.Clear();
    }
}

可以在 C#/dotNet 5 中解密由 openssl enc -k 加密的 AES 密码保护文件吗？

It is possible to decrypt AES password protected file in C# / dotNet 5 encrypted by openssl enc -k?

c#

openssl

aes

.net-core